# The "Real Deal" with 8 ohm drivers



## npdang

I've seen many people say, "Well I want to use this speaker, but I'm put off by the fact that it's 8 ohms." 

Let me explain why it's ok to use an 8 ohm speaker, and why it could actually be better than a 4 or 2 ohm speaker.

First of all, using a higher impedance than what your amp is nominally rated for is always ok. In fact, if your amp is rated for 4 and 2 ohm impedances, typically you will get less power into 8 ohms meaning that your amp will run cooler and more efficiently at higher impedances. It won't hurt your amp, and in fact it's actually much better for your amp's longevity.

Now, you're probably saying how is getting less power out of my amp a good thing? Think of your amp's power reserves as your bank account. Just because you have 100 dollars in your bank account doesn't mean you have to spend it all. Quite the opposite. Wouldn't you rather spend LESS and get MORE? That's exactly what you're doing when you use less power from your amp, and get the same amount of output from a high efficiency speaker.

Remember, most speakers are rated at 2.83V. A 4 ohm speaker rated for 90db spl at 2.83v is really being rated at 2 watts! Whereas an 8 ohm speaker rated for 90db spl at 2.83v is only being rated at 1 watt. You can do the math for yourself, Power = Voltage^2 / resistance. At 2 watts, we can assume that same 8 ohm speaker is actually rated at 93db spl (remember, every doubling of power gives you a theoretical 3db gain in spl). So using that 8 ohm speaker will give you the same amount of output, at half the power required as a 4 ohm speaker. Your amps run cooler and draw less power from your vehicle's charging system, your speakers run cooler, and everyone is happy!

Ok, now let's look at another example of an 8 ohm versus 4 ohm voice coil. Typically, the efficiency of a speaker is given by:

Efficiency = ( B^2 * L^2 ) / ( R * Sd^2 * Mms^2 )

B = magnetic field strength
L = length of wire
R = resistance
Sd = surface area
Mms = mass

So for your 8 ohm voice coil, using the same wire as a 4 ohm voice coil, you would need twice the L or length to get an 8 ohm impedance. That makes sense doesn't it? A longer wire will have more resistance. Now, looking at the formula above, doubling L actually causes your efficiency to rise, even though the impedance also rises. So in this very oversimplified example, raising the impedance actually causes efficiency to go up and lowering the impedance actually causes a loss of efficiency.

What's important to remember is that it's the overall output and efficiency of the speaker that's important, not the impedance. A high impedance, high efficiency driver can get just as loud off a small amount of power as a low impedance, low efficiency driver that sucks a ton of power! Just because you have a 100 watt amp doesn't mean you have to use all 100 watts.... it's all about being efficient.

I also found this excellent post by Dan Wiggins over at carstereos.org:

"I think one thing to consider is that going to a higher impedance voice coil will result in better packing of the voice coil, meaning a higher cross-sectional-area of copper in the flux, for a given mass.

If you take a given driver, and simply swap out voice coils, you end up with more efficiency as you increase the impedance. Take a voice coil, say 2" diameter, 1" winding length, 24AWG 4 layer, and swap it with a 2" diameter, 1" winding length, 27AWG 4 layer, and you double the impedance, but the efficiency also goes up - less mass and better packing density."

It's because the moving mass has dropped, and if desired - because of the thinner wire diameter which packs in tighter - you can put more layers in the voice coil and potentially raise the BL."


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## mitchyz250f

Please help me understand this better. Let us say I have an amp (Orion SX150) that puts out:
-150 watts per channel @ 4-ohm,
-300 watts per channel at 2-ohms
-600 watts bridged @ 4-ohm

Lets say I have sub that has two 8-ohm coils (tempest) or a sub with two 2-ohm coils. What would be the performance difference being with running the amp bridged, non-bridged with the sub in parallel or series? If you could answer this I would be very grateful.


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## npdang

I'm not sure that I understand the question. WIth that amp, and a dual 8 ohm sub you would want to wire the sub in parallel for a 4 ohm nominal load.
For a dual 2 ohm sub, you would want to wire the coils in series for a 4 ohm nominal load. In all instances, you'd want to run your amp bridged into a 4 ohm load.

However, if you were to chose between a sub that was 4 ohm vs. 8 ohm, and the 8 ohm sub was more efficient by ~3db or more... I would choose the 8 ohm sub since you would be pushing your amp alot less harder and achieving same/more output.


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## calvinhpk

ok...for this senario....
i have this amp that can output 4x150w @4ohm

and i have 2 choices of mid same manufacturer, same series, but different impedance, 
i) 18W/4531G00 - 4ohm
ii) 18W/8531G00 - 8ohm

which one would give me more control, better sound? 
will I lose out on some kick-bass in the 8ohm series?


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## 10K2HVN

revelators.. yawn....

you wont hear the difference, just get the 4-ohm because you can.

what are you planning to run with those mids..?

If your planning to run them in the doors, NpDang says the Seas CA18RNX sound better in the doors, freeair.


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## calvinhpk

noted. planning to put at the door. In consideration also the 15W version instead of the 18W.
the matter is, i've never listen to the Seas CA18RNX
i've listen to the revelator 4ohm version, and love it.

running with an a/d/s/ P850.2, bridged.


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## Tirefryr

I was down to the Revs or Lotus for In-door app. After doing research, the Lotus/Excel drivers seem to be far better suited. If you have the room for the proper enclosure (and the extra cash), I'd suggest the Revs. Well, then again, that depends on the overall application you are looking for.


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## Kramerica

So does this also mean that an 8 Ohm driver will pull halve as much current than a 4 Ohm driver?

Just trying to figure out the total current draw if I were to add another amplifier.

Thanks


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## demon2091tb

I would think it would, as he said the amp would run cooler and be more efficient with an 8ohm driver over a 4ohm driver at the same sensativity. Say you have a driver with 88db/2.83v at 8ohms, and then you have one that is 88db/2.83v @ 4ohms then its basically 1/2 the power as the formula states, to get the same sensativity of the driver. Because the length of wire for the 8ohm driver is 2x as long as the 4ohm driver, making the 8ohm driver as effecient as the 4ohm driver with 1/2 the power.

Hope i re-itterated that correctly.

The big question i have is, Would cutting down the amount of power that an amp can possibly put out at 4ohms rather than 8ohms have a huge difference on overall spl levels? I probobly already answere my question but besides the obvious benefits of having an amp run cooler and lengthening the life of the amp, how amount actual power differences in question. Like having an amp that does 100rms @ 4ohms, and 50rms or less at 8ohms make a huge impact on the overall sound and possible spl levels?

Hhehe or did i answer that already?


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## npdang

You answered your own question


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## demon2091tb

Haha Figures well good deal then, thats the only thing i really wondered about in using an 8ohm driver over a 4ohm driver, as all of the drivers that i will be using in my current build up are 8ohm drivers, except the Tempest and thats a duel 8 

The only other thing i worry about is how loud the CA18 and the LPG 26 could be with ~40rms each @ 8ohms, as my amp puts out 82rms @ 4ohms. Somewhat off topic but any ideas Dang? Will they be loud enough to suffice?


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## Kramerica

What I meant to ask was, will an amplifier powering an 8Ohm speaker pull halve the current then if it was powering a 4Ohm speaker?

Say an amp pulls 20 amps to power a 4Ohm speaker.

Will the same amp only need 10 amps to power the 8Ohm speaker?

Thanks, and I will be getting a Dayton Reference tweeter and midrange to replace some CDT's.


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## minitruck_freq

demon2091tb said:


> The only other thing i worry about is how loud the CA18 and the LPG 26 could be with ~40rms each @ 8ohms, as my amp puts out 82rms @ 4ohms. Somewhat off topic but any ideas Dang? Will they be loud enough to suffice?



40 watts will be loud with that combo. i have the ca18's and lpg 25nfa's running off an arc 4050. around 50x4 rated power. they get quite loud. even with the gains all the way down.


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## npdang

40 watts will be very loud... however, keep in mind that with music an amp will very rarely be outputting it's max. continuous power.


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## minitruck_freq

i played a 1 khz. tone at my normal listening level...measured ac voltage across + and - terminals... used the formula to convert to wattage blah blah blah. my ca18's are getting just over 17 watts. they are really loud with that little power to them. that myth about needing alot of power is just rediculous. IMO of course.


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## pervo

finally registered thanks npdang!

wanted to bring attention to some issues 

an 8 ohm driver compared to a 4 ohm, all things being equal outside of the voice coil windings have these trade offs

the 8 ohm will be slightly thinner and longer
resulting in more turns in the gap.... thus higher bl

making a 4 ohm will have a lower bl and thus needs to compensate

one meathod is to double the layer of voice coils, often facilitating the need for a different voice coil winding... ie flatter wires in order to fit in the same gap. thus bl will most likely not surpas the 8 ohm because even more windings are lost

so dirrect conclusions cannot be drawn form exactly how much inductance differs on the 4 layer vc vs the longer (winding wise) 2 layer

but it is safe to say that inductance will be higher on the 4 layer
also increased mass plays a factor also


this is my understansing at least


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## dwyers99

I HAVE A QUESTION. I AM CURRENTLY RUNNING AN AUDIO ART 100HC THAT CLAIMS STABLE TO 1/2 OHM A CHANNEL

also have 2 oz matrix elite subs dual 4 ohm coils

in this case i had wondered how much difference i would get in the different loads i applied to this amp

i mean 1000 to 1200 watts bridged at 1ohm should give me that bass i need but i am worried it might be overkill both for my front stage and my electrical system not to mention running now at a 2 ohms load bridged is making it considerably hot even at mid listening levels.

i honestly dont think this amp can handle much lower impedence than 1 ohm/channel

however running each channel straight to each sub w/ say a 2ohm load drops the wattage of the amp significantly, nevermind running it to each sub w/ an 8 ohm load

i will try it tonight for kickS (BOTH 2 AND 8 PER CHANNEL)but i would like to hear your feedback on this

I understand what this thread was saying and it makes a great point btw!


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## kckon

So in conclusion does a 2 ohm load have an increase in spl over an 8 ohm speaker?? we know that the amp will run hotter. Also so why make 1 ohm stable amps?


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## npdang

It may or may not. It depends on the speaker. The key is to pay atttention to BOTH the efficiency and the impedance of the speaker.

I was just pointing out that there are tradeoffs in getting a low impedance driver that may lower efficiency if not compensated for. Of course for dual voice coil speakers it maybe different.


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## chad

I think another thing that DIY types overlook is the distance from the driver. Granted sensitivity is rated 1W/1M BUT coming from a home/pro environment we tend to go by experience and dictate a sensitivity number and involuntarily/mentally calculate that to "Listening Position Loudness" Knowing that sound pressure level decreases 6dB for every time you double the distance in an anechoic environment, one can conclude that in a vehicle interior the level perceived with one watt input will be MUCH greater than that it would be in a home or other surrounding. This also proves that the reduction in power going to an 8 ohm driver will be negated by early reflections, cabin gain and lack of appreciable distance from the driver. So not only is it an electrical calculation it’s a matter of the intended application that keeps the SPL of the driver up well within acceptable limits.

Chad


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## npdang

Very true, good post Chad.


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## MarkZ

Nice article, but one *very important* thing I didn't see mentioned was power compression. In the end, the actual resistive component of the 8 ohm and 4 ohm speaker probably wouldn't be terribly far off from each other in most drivers, assuming substantial power levels (a safe assumption, because if we're talking about low volume levels, the point is moot anyway). That theoretical doubling of power you get when you halve the impedance quickly goes away when you factor in amplifier losses and power compression. And that's before you even get into the loudspeaker sensitivity stuff. [For those who don't know, power compression is the phenomenon whereby the resistive component of the driver increases with temperature -- naturally, more power dissipation means higher resistance which, for a voltage amplifier, means a reduction in power dissipation. It's a sort of negative feedback mechanism].

Anyway, you're right to say that the 4 ohm vs 8 ohm issue is all a tradeoff. But you can also look at it from a different perspective: to deliver the same amount of *power* into the 4 ohm speaker requires less voltage. This doesn't matter much until the signal starts to approach the onset of clipping. The problem is that with an 8 ohm driver you'll reach clipping earlier than you will with a 4 ohm driver (again, assuming somewhat similar power dissipation!).

The obvious response to that is: so what? If we've already established that the difference between 4 ohm and 8 ohm output isn't that great because of power compression and amplifier losses, then the difference in clipping shouldn't be all that great either, right? Maybe not. For some musical content, the difference between the peak and average output (usually specified as the "crest factor") can be substantial. So the transients at even moderate volume levels can sometimes reach the rail voltage. That translates into distortion...whether or not it's enough to be perceptible is the question. We can typically tolerate a pretty hefty amount of clipping before it becomes noticable.

Personally, I like to use amplifiers that have enough guts to them to be able to run the 2 or 4 ohm load they claim to be able to run and not have to worry about it. But I also realize that if the speaker I want to use is a higher impedance, like a lot of the 8 ohm stuff that people tout, it's definitely not the end of the world...


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## fearlessfly28

Im looking to get a pair of 6.5" midbass drivers.
Alot of peeps reccomended the Seas W18. 
My amp is rated 50w @ 4 ohms.(zapco)

Straight to the point....
Seas W18 will outperform the Seas Performance midbass??


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## npdang

Should be fine with that power, although you will notice a definite improvement in dynamics with more power.


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## fearlessfly28

so u reccomend the Xcels over the Performers?


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## npdang

I don't think you can compare the two. Completely different drivers.


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## fearlessfly28

Hmmm so help a brotha out =)
midbass...dedicated midbass...which one??


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## tf1216

Hey, how long do you have to make your decision? 

If I get some free time I will hook up my L18 to my 4.0 and see if I notice a difference in its performance from the 6.0.

I think you might want the 4 ohm driver for your situation.


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## avaxis

i've been reading npdang's article for very long and trying to get it in my head and understand it..and i came up with the figures to explain what npdang is saying.. (i can't quite compute it so i just have to list it down)

speaker A
4 ohm
[email protected] = 2watts and 0.7075A current draw

speaker B
8ohm
[email protected] = 1watts and 0.35375A current draw

amp X
16w @ 4ohm
8w @ 8ohm

every double of power would be +3dB, it can be said that both speaker A & B would play at the same loudness levels if pushed by amp X

speaker A + amp X 
2 watt = 90dB
4 watt = 93dB
8 watt = 96dB
16 watt = 99dB

speaker A + amp X
1 watt = 90dB
2 watt = 93dB
4 watt = 96dB
8 watt = 99dB

the difference would be that @ higher impedence, the draw would be at higher voltages but at lower current draw... or in other words..less load.. 

i hope i am accurate..else do correct me. i was reading npdang's explaination but i couldnt visualize it..until i came up with the figures above.. simply put, its all about matching the impedance and sensitivity of the speaker to the amp. an amp rated for 4ohm would work at 8ohm, and most of the time, with less effort.


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## notacop

Here is a post i made a while back trying to simplify the info in this thread:



> A quick summary (hopefully simplified version) of the tech post.
> 
> You need to look at the sensitivity ratings of each driver and how they are rated.
> 
> 
> If both are rated 1w/1m you need to be 3db higher sensitivity to get the same output with 8 ohm vs 4 ohm
> 
> If both are rated 2.83v/1m you need to be the same or higher to get the same (or better) output.
> 
> 
> The reasoning is if both speakers are rated with 1watt that is assuming same power to both speakers, since you will be applying half power you will get half output (-3db) so if the speaker is +3db sensitivity or higher you are overcoming that loss of power.
> 
> If both are rated with 2.83v that means the 4 ohm speaker was getting 2 watts while the 8ohm speaker was only getting 1 watt, that means that the 4 ohm speaker was given a 3db boost in sensitivity numbers given the same power. So 4ohm-3db = 8ohm given the same power. However since we are only giving half power to the 8 ohm driver our equation is going to be more like 4ohm-3db=8ohm-3db. Obviously the "-3db" part cancels itself out, so as long as sensitivity is the same or better you will get just as loud.
> 
> 
> On top of that the way 8ohm drivers are built leads to higher sensitivity ratings so you are more likely to find 8 ohm speakers that can meet the above sensitivity goals.
> 
> Hope that helps


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## demon2091tb

Yea so effectively, running an 8ohm load on an amp that is rated at 4ohms, is 1/2 the power of the 4ohm load, but can be just as loud, given the spl/w, if 2 speakers have the same spl lvls' but different imp. the higher imp. or 8ohm load will be run cooler, etc.

Only other reason i would run a 4ohm driver is to just get loads and loads more power out of an amp.

For instance, i'll be running LPG 26's at 8ohms, 82rms @4ohms, diyma 2" at 5ohms, 82rms @ 4ohms, possibly a pair of extremis 6.4's at 4ohm, 160wrms @4ohms.


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## Hernan

I'm running a pair of Auras NS3, 8ohms and (very) low sensitivity. No problem at all powered by 2 x 40W amp with the gains about 75%. They keep the pace with the midbass and Sub powered by a 75 x 4 Eclipse amp. If these drivers work ok, I could guess that any other "popular" 8 ohmer should work too.


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## scar19

I have a 4 channel amp that I'm using to power the tweeters and mid-woofers on my 3Way active system. Currently, 2 channels are connected to the tweets at 4 Ohm and the other 2 channels are for the mid-woofers, also at 4 Ohm...
Let's say I buy a set of 8 Ohm woofers, to exchange for the actual 4 Ohm ones that I have installed. Will the amp work fine? In this case, I would have 2 channels for the tweets at 4 Ohm and the other 2 at 8 Ohm! Is this possible? The amp is rated 4x75W RMS...


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## Chaos

scar19 said:


> Let's say I buy a set of 8 Ohm woofers, to exchange for the actual 4 Ohm ones that I have installed. Will the amp work fine? In this case, I would have 2 channels for the tweets at 4 Ohm and the other 2 at 8 Ohm! Is this possible?



No problem. Keeping in mind the subject matter of this thread, you should be able to achieve similar output levels (provided that you choose drivers wisely) while putting less demand on your amp.


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## 03blueSI

And this is why I think all speakers should be rated at 1w/1m. This way all speakers can easily be compared


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## skydeaner

03blueSI said:


> And this is why I think all speakers should be rated at 1w/1m. This way all speakers can easily be compared



^^true dat


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## Pulse-R

hope you don't hate me for digging this one up...

back on the topic of efficiency...
A colleague of mine insists that efficiency at 1W is meaningless when you apply a lot of power to a speaker, calling it power compression loss.
I understand the concept, but I want to know if it is true, and why....


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## MarkZ

Pulse-R said:


> hope you don't hate me for digging this one up...
> 
> back on the topic of efficiency...
> A colleague of mine insists that efficiency at 1W is meaningless when you apply a lot of power to a speaker, calling it power compression loss.
> I understand the concept, but I want to know if it is true, and why....


The resistance of the voice coil increases with increasing temperature. That's true (to some extent) of all conductors. Hell, that's how a light bulb works.

Although I'd hesitate to call power compression a "loss". A loss implies a loss in efficiency, but usually carries the connotation of waste. True, system efficiency decreases with power compression, but it's not being lost in transduction or wasted per se (ie. it's not being converted to heat or something).


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## Whiterabbit

given the fact that many DIY enthusiasts tend to change power output to each driver (like buying a 50 watt amp for the tweeters and a 350 watt amp for midbass drivers), and that the DIY enthusiasts tent to have advanced signal processors that allow for tuning individual gain between each drivers for the purpose of output matching, Ive never really concerned myself much with efficiency.

Dont get me wrong, I always check it and keep it in mind. just in case. But I see it as a qualitative spec rather than quantitative, and until I run or install a passive stage ill never use efficiency as a "deal breaker" when picking drivers.

so I CERTAINLY dont see 8 ohm drivers as a dealbreaker either! if the other performance specs fit my app, its the driver for me!


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## erickoh

Assuming no difference in efficiency, are there any disadvantages in using an 8ohm driver vs a corresponding 4ohmer? If there isnt, then why are 4ohm speakers the "standard" for automotive usage?


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## MarkZ

Whiterabbit said:


> given the fact that many DIY enthusiasts tend to change power output to each driver (like buying a 50 watt amp for the tweeters and a 350 watt amp for midbass drivers), and that the DIY enthusiasts tent to have advanced signal processors that allow for tuning individual gain between each drivers for the purpose of output matching, Ive never really concerned myself much with efficiency.
> 
> Dont get me wrong, I always check it and keep it in mind. just in case. But I see it as a qualitative spec rather than quantitative, and until I run or install a passive stage ill never use efficiency as a "deal breaker" when picking drivers.
> 
> so I CERTAINLY dont see 8 ohm drivers as a dealbreaker either! if the other performance specs fit my app, its the driver for me!


Efficiency becomes an important parameter when you start talking about high output applications. The overall output capabilities of the driver are dominated by efficiency. Personally, I think it's a pretty big deal, particularly in midrange and midbass applications where output limitations are often very real (partly due to their unique position of trying to achieve high frequency extension while still trying to move some air).


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## MarkZ

erickoh said:


> Assuming no difference in efficiency, are there any disadvantages in using an 8ohm driver vs a corresponding 4ohmer? If there isnt, then why are 4ohm speakers the "standard" for automotive usage?


I can't think of any inherent disadvantages. In fact, some amplifiers will like it better, and amplifier design is a bit easier with higher impedance loads in mind.

From what I understand, the original rationale for lower impedance drivers in cars was the reluctance to use power supplies in amplifiers (and head units) that worked on voltages higher than 12v. With only 12v available, the only way to increase power is by lowering the impedance. With aftermarket amps, that problem goes away.

However, another reason to use low impedance drivers comes with the advent of switching amplifiers -- specifically, class D and "class T". The basic operation of this type of amplifier pretty much requires low impedance loads (although they can be designed around higher impedance loads).


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## evan

MarkZ said:


> However, another reason to use low impedance drivers comes with the advent of switching amplifiers -- specifically, class D and "class T". The basic operation of this type of amplifier pretty much requires low impedance loads (although they can be designed around higher impedance loads).


Can you elaborate on that?


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## npdang

Switching amplifiers are generally more efficient, and cost effective but tend to maximize their power output into low impedance loads.


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## MarkZ

Their basic design topology makes them more suitable for low impedance loads. The transistors "like" to switch rather than operate within their linear range. Also, in some class D amps, the output filter (which converts the pulsed representation of the signal into a usable audio signal) is supposedly optimized for the targeted impedances of the amp, which tends to be low.


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## evan

Thanks for the clarification.


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## erickoh

Thank you, that concern was at the back of my mind too, since I am using the alpine PDX amp but was considering trying the Seas L18 8ohmer. I guess I'll keep that project on hold for now


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## Whiterabbit

good god why? with 150 rms at your disposal what difference would it make if the driver were 1 ohm or 16 ohms?


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## MattinTheCrown

MarkZ said:


> From what I understand, the original rationale for lower impedance drivers in cars was the reluctance to use power supplies in amplifiers (and head units) that worked on voltages higher than 12v. With only 12v available, the only way to increase power is by lowering the impedance. With aftermarket amps, that problem goes away.


Help me out; I don't understand how that problem goes away. Isn't the problem all about getting high amounts of power out of a 12V source? Regardless of the amp you have, you're still feeding off a 12V source, are you not? What am I missing?


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## MarkZ

You're feeding off a 12v source no matter what, that's correct. But amplifiers convert that 12v into a higher voltage in order to achieve greater amounts of power. This requires a more complex and sizable power supply in the amp, which tends to take up about 1/4 of the total real estate in a typical amplifier (and about half of the heatsink). So it's not exactly trivial to stick a power supply that does that into something small and confined like a head unit, which is why most head units out there were faced with that 12v limit.


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## MattinTheCrown

MarkZ said:


> You're feeding off a 12v source no matter what, that's correct. But amplifiers convert that 12v into a higher voltage in order to achieve greater amounts of power. This requires a more complex and sizable power supply in the amp, which tends to take up about 1/4 of the total real estate in a typical amplifier (and about half of the heatsink). So it's not exactly trivial to stick a power supply that does that into something small and confined like a head unit, which is why most head units out there were faced with that 12v limit.


Oh, I see. I got confused there. My thinking was just that the power supply's ability to convert to the higher voltage was the main factor in difficulty, and therefore, cost. See, even if you're allowing for these monster supplies, you're still saving money and trouble by just building 4ohm speakers (all things being equal, obviously). Or at least that's what I always assumed.

ETA: This, of course, compared to home application where you're working with voltages sufficiently high to make this sort of thing moot.


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## chad

MattinTheCrown said:


> ETA: This, of course, compared to home application where you're working with voltages sufficiently high to make this sort of thing moot.



Yes but you are still faced with the voltage limits of the semiconductors in the amplifiers. Car amps run at nearly the same rail voltages as home amps if not more. Not until you get intop pro amps do you see the mondo rail voltages (like 180V rail to rail) in a Crest Audio big boy 01 series, get out your wallet though.

Chad


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## icky4

I think I have got this figured out, but I want to make sure. I was thinking about buying SEAS Lotus Reference speakers for a 3 way set up. I was going to buy the RW165/1 6.5" for midbass and the RM110 4.5" for midrange. These have slmost the exact same specs at the SEAS Excel W18 and W12. Since I havent been able to find the Lotus midrange, I would be able to use the Excel midrange and midbass instead? Each midbass would be recieving 150W RMS and 75 W RMS to each midrange (4 Ohm rating). 

Also, at this power would I be able to use the W22 instead of the W18 given that it will fit in my door?


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## GlasSman

NpDang. If we're talking about a car woofer like an IDQ8 DVC with 4 ohm coils and a sensitivity of 91.5 do the same rules apply since it's not clear wether that speaker was tested at 4 or 8 ohms? My plans for my current setup are limited since I need my lower powered amp, a Reference 500 for my sub. My only options for my midbass is a Rubicon 702 which does 350x2 into 2 ohms, 125x2 into 4 ohms and 75x2 into 8ohms. I've run them at 2 ohms in my previous car but I just don't want THAT much power up front and the extra strain on the amp and electrical system.


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## aneonrider

Although 7 weeks old... I'll chime in that 95% of the DVC subwoofers have their t/s parameters measured when the coils are in series. If they don't, it will be noted.


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## Whiterabbit

and there are also references to methodologies of damping dvc subwoofers by powering only one coil, then "tuning" your Q by either leaving the second coil open, shorting it, or installing a resistor in there.

could be a fun test


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## 1stOnRaceDay

Another question. I was looking at the RS180 4 and 8 Ohm power handling capabilities. Both have 60W RMS/90 Max. Does that mean that if I use an amp rated at 100W at 4Ohms, that I could toast the 4 Ohm version, but would be fine with the 8 since the amp will only deliver 50W to an 8 Ohm load. By the way, the 3 Ohm rule holds here 91 vs 88 dB at 2.83/1m.


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## ryan s

kind of OT but i changed my dual 4 ohm sub from parallel to series yesterday and polyfilled the box. it sounds completely different and im loving it, thanks to this thread


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## Oliver

ryan s said:


> kind of OT but i changed my dual 4 ohm sub from parallel to series yesterday and polyfilled the box. it sounds completely different and im loving it, thanks to this thread


Glad to hear it !!  

NP Dang, will be too !!


----------



## mitchyz250f

Sorry, to bring this up from the dead and I am sure it has been answered 100 times. 

I have an Orion 2150GX; it puts out 150 watts per channel into 4 ohms, 300 watts per channel into 2 ohms. I guess it puts out 75 watts per channel into 8 ohms.

I have dual 4 ohm VC speakers, IDQ8's. The IDQ8's could be setup as 2 ohm or eight ohm speakers. I would be getting 300 watts per channel at 2 ohms and 75 watts per channel at 8 ohms. Sounds like a huge difference to me. How would the speakers sound different in each setup?

These are midbasses (100-250hz) and my primary interest are the dynamics (headroom).

BTW, my car has been in pieces since dec. 19. 2007. I hope to have it together in the next 3 weeks.


----------



## notacop

mitchyz250f said:


> Sorry, to bring this up from the dead and I am sure it has been answered 100 times.
> 
> I have an Orion 2150GX; it puts out 150 watts per channel into 4 ohms, 300 watts per channel into 2 ohms. I guess it puts out 75 watts per channel into 8 ohms.
> 
> I have dual 4 ohm VC speakers, IDQ8's. The IDQ8's could be setup as 2 ohm or eight ohm speakers. I would be getting 300 watts per channel at 2 ohms and 75 watts per channel at 8 ohms. Sounds like a huge difference to me. How would the speakers sound different in each setup?
> 
> These are midbasses (100-250hz) and my primary interest are the dynamics (headroom).
> 
> BTW, my car has been in pieces since dec. 19. 2007. I hope to have it together in the next 3 weeks.




This thread is meant to apply comparing a 4 ohm driver with an 8 ohm driver. In application where you have multiple wiring options for the same driver (like your DVC sub) wire it to get the most power from the amp, in your case 2 ohms. Since efficiency is not drastically different when you wire it differently, since it is still using the same coils, just in a different configuration.


----------



## mitchyz250f

I understand what you are saying and it makes sense. But what about this statement;

"kind of OT but i changed my dual 4 ohm sub from parallel to series yesterday and polyfilled the box. it sounds completely different and im loving it, thanks to this thread"

I have read the same thing on 'diyaudio' about subs.


----------



## BEAVER

I'm gonna have to side with notacop on this one.

I believe the original purpose of this thread was to compare single voice coil drivers and educate the masses on the possible benefit of 8ohm drivers vs. 4ohm drivers... I don't believe it was intended to have people re-wiring their DVC subs to get less power to them. This is just silly, in my estimation. Please correct me if I'm wrong.


----------



## jnelly

Hey, I don't post much but have a question. I am running a JL 10w1-8 off of a MTX Thunder 502 and to get any noticeable output I have to crank the gains all the way up. The sub's Rms rating is 125 watts. So I figure at an 8 ohm load the amp is pushing out around 180 watts. I guess my question is why the gains have to be maxed out for for any good amount of output.


----------



## bdubs767

bobditts said:


> The gain is not a volume nob! you are more than likely sending that sub a very distorted signal at higher volumes. Id be very careful if I were you


that was not his question.....


To the original poster it most likely has to do with weak out voltage of your head unit. But there are many different variables that could be effecting why you are not getting what you consider to be a good volume.


----------



## MarkZ

bobditts said:


> The gain is not a volume nob! you are more than likely sending that sub a very distorted signal at higher volumes. Id be very careful if I were you


The gain IS a volume knob. There's no reason to think that his sub is receiving a distorted signal.


----------



## jnelly

I set the gains by putting the volume to 3/4 of the way up on the HU and then slowly turning the gain up until it hear distortion. The head unit I am using is a Clarion Hx-D10 w/ the processor. It has 4v pre-outs. I just don't get any noticeable output unless the gains are maxed out. Any help is appreciated.


----------



## bdubs767

jnelly said:


> I set the gains by putting the volume to 3/4 of the way up on the HU and then slowly turning the gain up until it hear distortion. The head unit I am using is a Clarion Hx-D10 w/ the processor. It has 4v pre-outs. I just don't get any noticeable output unless the gains are maxed out. Any help is appreciated.



Thats prob max 4 volts out. I doubt it puts any thing more then 2 volts out. A line driver would not hurt.


----------



## Oliver

Ratio = input-to-output.

Going in reverse order turn gain down on amp or amps, next piece in the line and finally head unit.

Now going in forward turn volume up on head unit to 3/4 of full, turn gain up on amp [you are looking to get the headunit at a clipping point at the same time the amp clips ].


----------



## 60ndown

chad said:


> Yes but you are still faced with the voltage limits of the semiconductors in the amplifiers. Car amps run at nearly the same rail voltages as home amps if not more. Not until you get intop pro amps do you see the mondo rail voltages (like 180V rail to rail) in a Crest Audio big boy 01 series, get out your wallet though.
> 
> Chad


i modded my ipod internal amp to that ^.


----------



## AAAAAAA

I had fun today comparing a 4ohm tweeter (canton) to an 8ohm(tang band) and there was no diffrence that I could hear volume wise at most frequencies.

High efficiency 8ohms rules!


----------



## 60ndown

agreed,
my new midrange
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-020


----------



## AAAAAAA

Here is mine, not high efficiency but not bad.
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-842


----------



## GlasSman

60ndown said:


> agreed,
> my new midrange
> http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-020


Slap a pair of those in the kicks....call it a day.


----------



## br85

I don't really see why anyone would think moving to 8 ohm drivers would be under most circumstances. Let's be realistic, most of us are constantly buying and selling gear anyway, surely we would just do our best to make amps match our speaker setup?

For example, I have recently purchased a pair of SLS 8". Previously I was running my 4 ohm midbass off 150 Watts per side. I'll be happy with 2 X 75W @ 4 ohms for a little while, but pretty soon I'm going to get another amp, bridge the two amps up and have 300 Watts per side at 8 ohms anyway.

Given how power is not really as expensive as it used to be, I only look at effeciency ratings to question whether the quoted Xmax can be reached with stated RMS power.

For example, if I saw this on an 8" driver (I haven't, but one day i'm sure i will):

Sensitivity: 79db
RMS power: 150W
XMAX: 10mm one way

I would call bs on ever seeing the driver stroke that much without causing a vcv (voice coil volcano).

If I trust the specs, I won't look at sensitivity or effeciency. I'll look at cone size, fs, rms power handling, and Xmax to determine what role it will play in a given setup and what amp to get for it.


----------



## Oliver

br85 said:


> Given how power is not really as expensive as it used to be, I only look at effeciency ratings to question whether the quoted Xmax can be reached with stated RMS power.


variables 

IB = less power handling

small box = less low end more power handling [ SPL ]

efficiency = how loud it gets with available power


----------



## br85

a$$hole said:


> variables
> 
> IB = less power handling
> 
> small box = less low end more power handling [ SPL ]
> 
> efficiency = how loud it gets with available power


Good point.


----------



## ErinH

br85 said:


> If I trust the specs, I won't look at sensitivity or effeciency. I'll look at cone size, fs, rms power handling, and Xmax to determine what role it will play in a given setup and what amp to get for it.


What would be the purpose of the driver?

If it's midbass in a door I'm looking at Sd, Fs and qts. Not worried much about xmax.


----------



## Oliver

bikinpunk said:


> What would be the purpose of the driver?
> 
> If it's midbass in a door I'm looking at Sd, Fs and qts. Not worried much about xmax.



Fs: 45 Hz 
Qts: ..38
Power handling: 70 watts RMS
Frequency range: 45-5,000 Hz

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=296-603


----------



## cheesehead

60ndown said:


> agreed,
> my new midrange
> http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=290-020


Did you go with this for midrange? Are you using it for midrange only?


----------



## 86mr2

Waaay off topic for the thread. Could you start a new one?


----------



## t3sn4f2

Best of both worlds = A bridged 4 channel (that increases in power from 4 ohms to 2 ohms) on a pair of 8 ohms drivers.


----------



## tim eh?

I have a nice 8ohm 8" vifa woofer that I would like to use as a sub just to pull the lows off a factory setup, but I have never been able to figure out what kind of amp to use for it. Any suggestions?


----------



## azngotskills

a two channel bridged or a mono...whats hard about it?


----------



## tim eh?

azngotskills said:


> a two channel bridged or a mono...whats hard about it?


well i guess i thought a typical amp would be too hot for it and also blow the system speakers away.


----------



## tim eh?

tim eh? said:


> well i guess i thought a typical amp would be too hot for it and also blow the system speakers away.


OK sorry that's stupid, but for example if my sub amp has a lo-pass filter of 80Hz on 4 ohm wouldn't that be drastically changed with an 8 ohm driver for one thing?


----------



## BassBrat

I was under the assumption that when you just decide to run amps at higher impedances they blow up.(ie. four ohm bridged amp would experience meltdown if run at 8 ohms). Someone answer this question please!


----------



## chad

BassBrat said:


> I was under the assumption that when you just decide to run amps at higher impedances they blow up.(ie. four ohm bridged amp would experience meltdown if run at 8 ohms). Someone answer this question please!


Whoever told you that needs to be shot, they could not be more wrong. an amp will run fine with ZERO load pending it's not a tube amp, a real tube amp, with tube finals and transformer outputs. Some of the SS mac amps with OP transformers did not like it either, but that's a RARE case to have OP transformers on a SS amp.


----------



## MiniVanMan

BassBrat said:


> I was under the assumption that when you just decide to run amps at higher impedances they blow up.(ie. four ohm bridged amp would experience meltdown if run at 8 ohms). Someone answer this question please!


It's going to be really hard for me to not be sarcastic here.

However, your assumption was exactly that, an assumption, and a wrong one at that. 

The fact is that running an amp at a higher impedance actually DECREASES the work the amp has to do. The lower the impedance, the more efficiency the amp loses. This efficiency loss creates heat. Heat is what will kill an amp.


----------



## Hernan

BassBrat said:


> I was under the assumption that when you just decide to run amps at higher impedances they blow up.(ie. four ohm bridged amp would experience meltdown if run at 8 ohms). Someone answer this question please!


It's just the opossite. You would stress the amp running at lower impedance, not higher.

A Car amp bridged to a 8 ohm load is just fine.


----------



## Oliver

Hernan said:


> It's just the opossite. You would stress the amp running at lower impedance, not higher.
> 
> A Car amp bridged to a 8 ohm load is just fine.


Whenever you bridge an amp the amp is functionally running at 1/2 the load {so it sees 4 ohms in this instance }


----------



## Hernan

a$$hole said:


> Whenever you bridge an amp the amp is functionally running at 1/2 the load {so it sees 4 ohms in this instance }


Half the load or double the voltage swing?
The speaker is a passive component... 8ohms is 8ohms independent to the amp. Any modern car amp is stable runnning 4 ohms loads bridged. 8ohms load for a bridged amp would not pull too much current. No problem.


----------



## chad

Hernan said:


> Half the load or double the voltage swing?
> 
> Both, absolutely.


 It will see it as a 4 ohm load if the driver is at 8, which in my eyes is absolutely perfect. big voltage, light load. 

Where magic is made.


----------



## MarkZ

a$$hole said:


> Whenever you bridge an amp the amp is functionally running at 1/2 the load {so it sees 4 ohms in this instance }


Fight fight fight!


----------



## Oliver

chad said:


> It will see it as a 4 ohm load if the driver is at 8, which in my eyes is absolutely perfect. big voltage, light load.
> 
> Where magic is made.





MarkZ said:


> Fight fight fight!


Never say DIE !! 

Thanks Chad and MarkZ !!!


----------



## MarkZ

a$$hole said:


> Never say DIE !!
> 
> Thanks Chad and MarkZ !!!


Say wha?? I'm with the other guy. Fight fight fight!


----------



## BassBrat

Thanks for clearing this up for me but MarkZ is right. One more bit of confusion i would like to get cleared up everyone keeps saying its fine if its bridged, what if you want to run an amp 8 ohms stereo, is that okay.


----------



## Candisa

Off course, people see amplifiers too much as power deliverers... 
That's not true (with most amps, there are exceptions), most amps 'deliver' more power on lower impedance loads, that would be impossible if amps were power deliverers...

Amps give voltage. The load decides how much current there flows and that current combined with the voltage gives power.

If the impedance of the load is too low, the current will be to high and you'll burn the amp. Higher impedance loads make current lower, nothing wrong with that. It doesn't matter if you bridge the load or you just connect it in stereo, high impedance = good, low impedance = BAD.

Even on amps that do work as power deliverers (instead of voltage deliverers) it's good to keep high impedance loads: an amp that gives the same power on 2 ohms as on 4 ohms will still give more current (but less voltage) at 2 ohms compared to 4 ohms. 

Voltage = good, Current = BAD, why do you think countries where you can't sue everybody for everything have 220-240V instead of 110-120V? Why do you think fuses and cables are rated on maximum current instead of maximum voltage?


----------



## shadowfactory

This thread really opened my eyes. I just went from a 4 ohm midbass driver on my bridged Arc 4050xxk to an 8 ohm peerless exclusive 7, and, just like the science says, there is just as much output but a much better experience! I didn't even have to adjust the gains much to have it match up to my other drivers, and I have as much power on tap as before, all while giving my amp a sexy dual 4 ohm load rather than dual 2 ohm (since its bridged). 

8 ohms ftw!


----------



## Candisa

"...but a much better experience..."

That's your amp that tells you it's glad it doesn't have to work that hard anymore


----------



## AboveAK

If i hooked up an 8ohm driver to a JL amp that had RIPS technology would that mean I'd get the same output power as i would say a 4ohm driver? I would think it would but i'm curious to know


----------



## djr

this is a intresting thread and very helpfull, but many people start off with the impression that all car audio shud be 4 ohm

the spl lads running major system often run at .5 ohm 

i have a lot learn in all these aspects. thanks for the info


----------



## t3sn4f2

AboveAK said:


> If i hooked up an 8ohm driver to a JL amp that had RIPS technology would that mean I'd get the same output power as i would say a 4ohm driver? I would think it would but i'm curious to know


Only when bridged.


----------



## chad

AboveAK said:


> If i hooked up an 8ohm driver to a JL amp that had RIPS technology would that mean I'd get the same output power as i would say a 4ohm driver? I would think it would but i'm curious to know


No At 4 ohms the RIPS system is at the highest rail voltage. I have a JL with RIPS that I plan to test this supper to see exactly how much if underrated it is and how it behaves at 8 ohm versus 4 ohm. FWIW I'm all 8 ohm except my sub which is 4 ohm.


----------



## Oliver

Candisa said:


> Amps give voltage. The load decides how much current there flows and that current combined with the voltage gives power.
> 
> 
> 
> 
> *HIGH Voltage* = good. HIGH Current = BAD . Why do you think fuses and cables are rated on maximum current instead of maximum voltage?
> 
> If the impedance of the load is too low, the current will be to high and you'll burn the amp up sooner than later. Higher impedance loads make current lower , nothing wrong with that. It doesn't matter if you bridge the load or you just connect it in stereo, high impedance = good. low impedance = lot harder on electrical system.


Definately !!


----------



## AboveAK

chad said:


> No At 4 ohms the RIPS system is at the highest rail voltage. I have a JL with RIPS that I plan to test this supper to see exactly how much if underrated it is and how it behaves at 8 ohm versus 4 ohm. FWIW I'm all 8 ohm except my sub which is 4 ohm.


Sweet. I'm interested to know the results and i'm sure you'll let us know.


----------



## AboveAK

Hey Chad did you test out that JL on those driver's yet? I really want to know the results..


----------



## IBcivic

AboveAK said:


> Hey Chad did you test out that JL on those driver's yet? I really want to know the results..


just stare at his avatar for a sec....you will have your answer.


----------



## chad

I don't have the heart to take it out of the car and out it on the bench... weather is cooling down, I'll be in the shop more soon


----------



## teenycar

Hopefully this isn't too far off topic but is it still ok to replace a 4ohm midbass in a passive 2 way setup with an 8 ohm driver? In other words I have a passive 2 way setup all 4 ohm, driven by a jl 450/4 rips amplifier. Can I pull the 4 ohm midbass and replace it with an 8 ohm midbass without doing anything else? Each set gets 75 watts to the tweet and the midbass. Will the 8 ohm midbass then be getting 37 watts and the tweet get 75 watts off the passive crossover? Thanks.


----------



## MiniVanMan

teenycar said:


> Hopefully this isn't too far off topic but is it still ok to replace a 4ohm midbass in a passive 2 way setup with an 8 ohm driver? In other words I have a passive 2 way setup all 4 ohm, driven by a jl 450/4 rips amplifier. Can I pull the 4 ohm midbass and replace it with an 8 ohm midbass without doing anything else? Each set gets 75 watts to the tweet and the midbass. Will the 8 ohm midbass then be getting 37 watts and the tweet get 75 watts off the passive crossover? Thanks.


No! Bad idea.

/e-handslap


----------



## teenycar

So the only thing I can do is to get rid of the passive 2 way rear fill setup and run the peerless sls 8" as a dedicated midbass run parallel with eachother and bridge channels 3 and 4 to send 150 watts? This would take away the left and right balance but as a rear fill I guess it wouldn't matter much anyway.


----------



## enduro

And as similar Q, could an 8 ohm tweeter be substituted for 4 ohm in a passive system? I imagine the answer is no, but the question is why not. 

How about 8ohm woofer and tweeter driver with the same 4 ohm passive crossover.?


----------



## chad

no, because the driver impedance dictates the crossover frequency and any notch filtering it may have.


----------



## enduro

So if the crossover was at 4500hz for the tweeter (4ohm) what would it be for an 8 ohm tweeter.


----------



## MiniVanMan

enduro said:


> So if the crossover was at 4500hz for the tweeter (4ohm) what would it be for an 8 ohm tweeter.


Guess. 

No, seriously guess, because that's all you can do. Unless you want to take impedance measurements for each tweeter.


----------



## Hernan

enduro said:


> So if the crossover was at 4500hz for the tweeter (4ohm) what would it be for an 8 ohm tweeter.


Aprox. half the frecuency for the 4ohms tw. No good.


----------



## t3sn4f2

Hernan said:


> Aprox. half the frecuency for the 4ohms tw. No good.


No..


----------



## MiniVanMan

Hernan said:


> Aprox. half the frecuency for the 4ohms tw. No good.


That's a BAD, and very inaccurate "general rule of thumb". 

I can show you tweeters that would have very similar component values for a 4500 crossover point even though their listed "nominal impedance" is different.

http://www.madisound.com/catalog/PDF/x3-06_exotic-t35.pdf

http://www.madisound.com/catalog/PDF/ST728.pdf


----------



## enduro

I'm not really getting the point you're trying to make with two tweeter examples above. Are you saying that if those 2 tweeters ( different impedences) are hooked to the same passive crossover, the crossover frequency will be the same ?


----------



## MiniVanMan

enduro said:


> I'm not really getting the point you're trying to make with two tweeter examples above. Are you saying that if those 2 tweeters ( different impedences) are hooked to the same passive crossover, the crossover frequency will be the same ?


The impedance of those two tweeters are very close at 4500 hz, even though one is rated at 6 ohms and the other at 8 ohms. Therefore the component values in the crossover would be pretty close. However, you could use both those tweeters down to 2000 hz, and the crossover component values would be vastly different if crossed there. 

In other words, just looking at the manufacturer's impedance spec gives no indication of what component values to use when designing a passive crossover. Properly designed passive crossovers use a combination of the driver's frequency response, coupled with the impedance curve to shape the response needed. Without knowing either, much less both, there's no way to tell how a driver will perform with a given random crossover.


----------



## Hernan

Hernan said:


> Aprox. half the frecuency for the 4ohms tw. No good.


Sorry, I was wrong. 
I just wanting to say that is not a good/safe idea to hook a higher impendance driver to a HP passive... 

Still, the electrical xo point should be lower?


----------



## ironchef b

Nice read. Changes my view on an 8 ohm speaker.


----------



## miphonematt

Agreed, this thread is fantastic. The Big Three, Active vs Passive, and this thread are, IMO, the first three threads a noob should read on this forum (a noob being someone who only knows the name brands sold at Best Buy or Circuit City)

After finding this thread I immediately picked up some Dayton Reference drivers, and solved a major mounting issue for me. Thanks guys for all the great content in this thread!


----------



## SummerGuy

very nice thread i think i will make some change in my setup!

do you have some nice 8 ohm home speaker to show ?

speaker wich can compete with focal 4 ohm cdt 4 ohms driver, hybrid , morel etc?


----------



## SummerGuy

ok this what i tried:

i have 2 cdt es-06 midbass in each door...so 4 misdbass.

they are 4 ohms.

before , they were each on a channel of my cdt sqa 4100.
so the amplifier saw 4 ohm load per chanel.

i tried them in serie with just two chanel.....so i had 115 w in 4 ohm for two midbass(just an image)

in reality it is something like 115/2= 57,5w for wo midbass in 8 ohms. but i think it would give soemthing like 70 w in reality.

so i have now 35 w at (in serie) per middbass...against 110 in 4 ohms .

i have surely a little lest power...but them sound like before ....
no difference in db! i think i have a little more control on them.



i will sold my sqa4100 to buy a two chanel for my midbass . like another arcaudio 300.2



really thank for this tips....

i will surely change some other componetnest year to get the 8 ohm load...it will have theorically more control..

and sure... less curent draw from the battery


----------



## SummerGuy

so if i have les amp for more volt in 8 ohm.....can i take a thiner speaker wire?


----------



## SummerGuy

mm i think i didnt understand the topic...but the sound level seems to be the same.. with 8 ohm . 

Maybe because it has more control i dont know


----------



## fredridge

wow, I have been to Canada and the people seemed much smarter than this... that was in Vancouver though


----------



## SummerGuy

yeah and in vancouver they speaker inglish as their first language...not here

anyways...the way i understand it now is to replace all speaker with 8 ohms


----------



## IBcivic

c'est pas mal trou de cul comme commentaire....


----------



## I800C0LLECT

SummerGuy said:


> yeah and in vancouver they speaker inglish as their first language...not here
> 
> anyways...the way i understand it now is to replace all speaker with 8 ohms


The purpose of the thread was to explain that 8ohm loads are not bad. That they can be very beneficial. Personally, I don't like to head below 4ohm loads but 2ohm or 1ohm loads aren't necessarily terrible either.

The goal is to learn how specifications effect your equipment. Sometimes you just don't need all that power from 2ohm or 1ohm. 4 and 8ohm loads can suffice your needs.

In the end, an 8ohm speaker just happens to be more efficient with power majority of the time. Therefore, it doesn't require as much.


----------



## SummerGuy

stinky06 said:


> c'est pas mal trou de cul comme commentaire....


bah ca lui a fait du bien surement. Rabaisser une personne pour se remonter..quoi de mieux pour l'égo


----------



## SummerGuy

I800C0LLECT said:


> The purpose of the thread was to explain that 8ohm loads are not bad. That they can be very beneficial. Personally, I don't like to head below 4ohm loads but 2ohm or 1ohm loads aren't necessarily terrible either.
> 
> The goal is to learn how specifications effect your equipment. Sometimes you just don't need all that power from 2ohm or 1ohm. 4 and 8ohm loads can suffice your needs.
> 
> In the end, an 8ohm speaker just happens to be more efficient with power majority of the time. Therefore, it doesn't require as much.


yes surely that 8 ohm with les power on my two cdt is enought for me.

i put them on my other amp yesterday..arc audio ks300.2, wich is180w x 2 @ 4 ohms

in 8 ohms the amplifier will surely loss less wattage in heat so...it is maybe more than 90 w x 2......surely something like 125 w x 2?


----------



## IBcivic

certe...lol


----------



## fredridge

yep, must just be language issue



SummerGuy said:


> yeah and in vancouver they speaker inglish as their first language...not here
> 
> anyways...the way i understand it now is to replace all speaker with 8 ohms


----------



## TPMS

npdang said:


> ....
> Remember, most speakers are rated at 2.83V. A 4 ohm speaker rated for 90db spl at 2.83v is really being rated at 2 watts! Whereas an 8 ohm speaker rated for 90db spl at 2.83v is only being rated at 1 watt. You can do the math for yourself, *Power = Voltage^2 / resistance.* At 2 watts, we can assume that same 8 ohm speaker is actually rated at 93db spl (remember, every doubling of power gives you a theoretical 3db gain in spl). So using that 8 ohm speaker will give you the same amount of output, at half the power required as a 4 ohm speaker. Your amps run cooler and draw less power from your vehicle's charging system, your speakers run cooler, and everyone is happy!
> 
> ...



math is clear but at this point I am really confused

let's consider the Morel Ultimo Sub: both the 4Ohm and the 2Ohm version have Sensitivity equally rated 88db at 2.83V.
I am going to drive them with my Monoblock amp that yields [email protected] or 800W @ 2 Ohm.
From the reasoning above: <<using that 8 ohm speaker will give you the same amount of output, at half the power required as a 4 ohm speaker>> ,
assuming no matter if we are comparing 8Ohms with 4 ohms or 4 Ohms with 2ohms, follows that the 2 Ohm version needs double the power just .. to give THE SAME amount of output.
so ... i will not obtain any higher sound level if running Ultimo 2Ohm instead of Ultimo 4ohm with my amplifier ?


----------



## MarkZ

TPMS said:


> math is clear but at this point I am really confused
> 
> let's consider the Morel Ultimo Sub: both the 4Ohm and the 2Ohm version have Sensitivity equally rated 88db at 2.83V.
> I am going to drive them with my Monoblock amp that yields [email protected] or 800W @ 2 Ohm.
> From the reasoning above: <<using that 8 ohm speaker will give you the same amount of output, at half the power required as a 4 ohm speaker>> ,
> assuming no matter if we are comparing 8Ohms with 4 ohms or 4 Ohms with 2ohms, follows that the 2 Ohm version needs double the power just .. to give THE SAME amount of output.
> so ... i will not obtain any higher sound level if running Ultimo 2Ohm instead of Ultimo 4ohm with my amplifier ?


If the sensitivities are really both the same for 2.83v, then yes, you are correct.


----------



## TPMS

MarkZ said:


> If the sensitivities are really both the same for 2.83v, then yes, you are correct.



that's what is written in specs 








something must be wrong somewhere 
I just got them both and didn't try yet but, everybody keep saying that the 2Ohm version DOES play louder !


----------



## kyheng

^Port tuning and enclosure design can make your sub louder.....


----------



## TPMS

.. found it: Morel's web designer is just slow at updating specification data 
this new table containing values for their new 8" sub clearly shows that sensitivity rises more than proportionately when halving resistance
+4.1db going from 4 to 2 ohms 
Morel Loudspeakers - Mobile Audio - Subwoofers - Ultimo Subwoofer - Ultimo Subwoofer

so, just take published data "cum grano salis"


----------



## I Need Bass

...sounds like my sub setup, I have 12" Lanzar OA 8ohm ( 1 cu ft) under rear seat driven by a LP 150IQ at 285 rms at 8ohms...output is upper nice, it is almost too much for my SPX 17pros at 4ohms driven by LP 5304IQ at 75 rms x4. Need to make pods for my doors to help SQ up front


----------



## I Need Bass

...okay, I just read the entire post and man there are a lot of people with serious math going on ...and I am totally rethinking the use of my amps.

To clarify: I want to use my USA 400 on my JL 10w6v2. The amps is unregulated and rated at 200 rms x 2 @ 4homs, 400rms x2 @ 2ohms...if I run the subs at 8ohms my amp will produce 100 rms x2 but give me the same output in db?

Can this be true as well for my midbass drivers... if I run my SPX 17pro's (4 ohm drivers w/ 88db sensitivity) in seires at 8ohm I will have the same output as if I ran them at 2 ohm using another USA 400 even though I will have much less RMS power output (50 rms per driver)? This was the way I intended to apply these drivers any way but just wondering about the output now that I have read this thread...


----------



## AboveAK

haha language is an issue. you guys are not understanding what's been said. I suggest you guys re-read the thread and actually think about it


----------



## I Need Bass

AboveAK said:


> haha language is an issue. you guys are not understanding what's been said. I suggest you guys re-read the thread and actually think about it


...I think I understand a lil bit, just want some reassurance that I am making sense of what has been said and that it will work to my advantage. I mean it has to be an improvement over my current set up.


----------



## AboveAK

Here's a lil hint. Look at the thread title...It's refering to 8 ohm drivers. It doesn't mean wiring it up to equal a 8 ohm load


----------



## HertzGuy

What is more important as far as speaker performance goes....
Do you want more current flowing to your speaker? OR
Do you want more voltage?

If I wire a 4ohm DVC sub in parallel it will produce a 2ohm load onto my amp with equal Voltages across each vc (Vtotal= V1=V2...) while the total current is summed together (Itotal =I1+I2) going into each vc, am I correct so far??

If I wire this same sub in series I get an 8 ohm load on my amp but now the voltages are summed together (Vtotal = V1+V2) and my current is equal (Itotal = I1=I2)

I know that the amp will produce more watts at the 4ohm load, thats not really my question. I would like to know which way, if either is preferable, of wiring my sub.
Is Current more important or Voltage?

Or neither, maybe all I should consider is the amount of resistance I am putting onto my amp and what my system requirements are??

Any help from the pro's greatly appreciated...


----------



## t3sn4f2

Ohm's Law with Calculator


----------



## Candisa

TPMS said:


> math is clear but at this point I am really confused
> 
> let's consider the Morel Ultimo Sub: both the 4Ohm and the 2Ohm version have Sensitivity equally rated 88db at 2.83V.
> I am going to drive them with my Monoblock amp that yields [email protected] or 800W @ 2 Ohm.
> ........
> so ... i will not obtain any higher sound level if running Ultimo 2Ohm instead of Ultimo 4ohm with my amplifier ?


2.83V at 4ohms = 2W, 2.83V at 2 ohms = 4W. This means, in your case, both versions will give you the same output, but the 2ohm version will require more power to reach it.
It won't give you more output, only more heat and lesser sound quality!
Most amps don't give double the power when impedance drops by half, so in those cases, it will even give less output!

greetings,
Isabelle


----------



## Candisa

TPMS said:


> .. found it: Morel's web designer is just slow at updating specification data
> this new table containing values for their new 8" sub clearly shows that sensitivity rises more than proportionately when halving resistance
> +4.1db going from 4 to 2 ohms
> Morel Loudspeakers - Mobile Audio - Subwoofers - Ultimo Subwoofer - Ultimo Subwoofer
> 
> so, just take published data "cum grano salis"


That's only for the 8". The 10" and 12" seem to have the same sensitivity whether you take the 4 or 2 ohms version. 
In case of the 8", the 2 ohm version is louder than the 4 ohm version. It's even louder than 2 4ohm versions wired in parallel, but that's only for the 8".
The question is if you indeed have to take the sensitivity of the 10 and 12" with a grain of salt, or if the differences between the 8" subs are... euh, different than the differences between the 10 and 12" subs...

greetings,
Isabelle


----------



## TPMS

Candisa said:


> 2.83V at 4ohms = 2W, 2.83V at 2 ohms = 4W. This means, in your case, both versions will give you the same output, but the 2ohm version will require more power to reach it.
> It won't give you more output, only more heat and lesser sound quality!
> Most amps don't give double the power when impedance drops by half, so in those cases, it will even give less output!
> 
> greetings,
> Isabelle



yes, that would be a given in case, and only in case, both drivers have same sensitivity.
but actually, if you look at updated data for Ultimo8" in the link posted, you'll see that sensitivity for the 2ohm version is much higher than for the 4ohm version ( 3db more meaning double sound output) 
... so that the NET effect will be MORE THAN beneficial 


ps: .. Morel just did not update old published data for Ultimo 10" and 12" !
the 12" 2oms just arrived to me and instructions in th ebooklet inside just have a stick upon old specs in correspondence of Ohm value.


----------



## t3sn4f2

TPMS said:


> *yes, that would be a given in case, and only in case, both drivers have same sensitivity.
> but actually, if you look at updated data for Ultimo8" in the link posted, you'll see that sensitivity for the 2ohm version is much higher than for the 4ohm version ( 3db more meaning double sound output)
> ... so that the NET effect will be MORE THAN beneficial *
> 
> 
> ps: .. Morel just did not update old published data for Ultimo 10" and 12" !
> the 12" 2oms just arrived to me and instructions in th ebooklet inside just have a stick upon old specs in correspondence of Ohm value.


"Sensitivity *1W* / 1M *84* dB *83.5* dB"


----------



## MarkZ

HertzGuy said:


> What is more important as far as speaker performance goes....
> Do you want more current flowing to your speaker? OR
> Do you want more voltage?
> 
> If I wire a 4ohm DVC sub in parallel it will produce a 2ohm load onto my amp with equal Voltages across each vc (Vtotal= V1=V2...) while the total current is summed together (Itotal =I1+I2) going into each vc, am I correct so far??
> 
> If I wire this same sub in series I get an 8 ohm load on my amp but now the voltages are summed together (Vtotal = V1+V2) and my current is equal (Itotal = I1=I2)


No. The voltage across each series coil is actually cut in half. And therefore, so is the current.


----------



## TPMS

t3sn4f2 said:


> "Sensitivity *1W* / 1M *84* dB *83.5* dB"



Sensitivity 2.83 Vrms / 1M *91.5* dB *87.4* dB


----------



## Candisa

I've said it before in this or a similar thread and I'll say it again: Yes it's better to keep impedance high, but NOT by wiring drivers/coils in series if the amp can handle them wired in parallel! 
It's a good thing to keep current as low as possible, but not if voltage drops with it!
If you have a DVC subwoofer and you're amplifier can handle the load of the coils wired in parallel, wire them in parallel!
The only 3 reasons to wire drivers/coils in series is if the amplifier:
- has a ****load of power so you still get at least ("at least" =/= just!!!) enough power from it
and/or
- isn't stable at the impedance load you get by putting everything in parallel.
- gives the same power at both impedance loads (which is possible with amps like PG Xenon, JL Slash...)

greetings,
Isabelle


----------



## t3sn4f2

TPMS said:


> Sensitivity 2.83 Vrms / 1M *91.5* dB *87.4* dB


How is a woofer more _sensitive_ if it needs more wattage to reach that increase in sensitivity when compared to a less sensitive one using less power.


----------



## TPMS

t3sn4f2 said:


> How is a woofer more _sensitive_ if it needs more wattage to reach that increase in sensitivity when compared to a less sensitive one using less power.


dunno 
.. I bought both versions exactly because I want to test myself which one work better with my amp anf for my taste, no matter of published data.
Then, I 'll sell the other


----------



## I Need Bass

AboveAK said:


> Here's a lil hint. Look at the thread title...It's refering to 8 ohm drivers. It doesn't mean wiring it up to equal a 8 ohm load


ok,but the amp just responds to ohm load not number of drivers correct? Besides I am just asking for clarifications, and if you are going to answer directly then maybe... well to frank I was looking for a "yes" or "no" type reply


----------



## subwoofery

Candisa said:


> I've said it before in this or a similar thread and I'll say it again: Yes it's better to keep impedance high, but NOT by wiring drivers/coils in series if the amp can handle them wired in parallel!
> It's a good thing to keep current as low as possible, but not if voltage drops with it!
> If you have a DVC subwoofer and you're amplifier can handle the load of the coils wired in parallel, wire them in parallel!
> The only 3 reasons to wire drivers/coils in series is if the amplifier:
> - has a ****load of power so you still get at least ("at least" =/= just!!!) enough power from it
> and/or
> - isn't stable at the impedance load you get by putting everything in parallel.
> - gives the same power at both impedance loads (which is possible with amps like PG Xenon, JL Slash...)
> 
> greetings,
> Isabelle


And 4, inductance (per voice coil) is cut in half. Therefore if your sub has an inductance of 1.2 in series, it will have 0.3 in parallel. 

Kelvin


----------



## MarkZ

subwoofery said:


> And 4, inductance (per voice coil) is cut in half. Therefore if your sub has an inductance of 1.2 in series, it will have 0.3 in parallel.
> 
> Kelvin


Doesn't matter. Resistance falls proportionally. L/R is what matters, not L.

The same isn't necessarily true when you change a single coil from 4 ohms to 8 ohms. That's because they generally don't achieve that simply by doubling the length of the VC.


----------



## HertzGuy

MarkZ said:


> No. The voltage across each series coil is actually cut in half. And therefore, so is the current.


Wait, how is the voltage cut in half?
Are voice coils not considered resistors, as far as ohms law is concerned?
Just trying to figure out the math here.
Thanks


----------



## MarkZ

HertzGuy said:


> Wait, how is the voltage cut in half?
> Are voice coils not considered resistors, as far as ohms law is concerned?
> Just trying to figure out the math here.
> Thanks


The output from the amplifier is the voltage, and it remains (mostly) unchanged regardless of the load. When you put two series resistors of equivalent value across it, each resistor has half of that voltage applied across its individual terminals. If those resistors were in parallel, each resistor would have the amplifier's full voltage across it.

In terms of ohm's law...

V = amplifier output
R1 = resistance of first VC
R2 = resistance of second VC

In a series configuration...

I = V/(R1+R2)

Therefore, the voltage across R1 is I*R1.

So, if the V is 40v, and the R1 and R2 are 4 ohms, then...

I = 40/8 = 5 amps
V across R1 = (5 amps)*(4 ohms) = 20v

20v is half the original 40v applied.

Draw out the circuit and fill in the voltage at every node, and I think it will become clearer to you.


----------



## HertzGuy

I was forgetting to take R1+R2, for total resistance, and divide that by V. 
Makes sense, thank you.
So we want to keep the current low, so not to much strain on the electrical system, while keeping volts high...is that right??


----------



## fredness

So why should I pay $300 for a set of components if I can use a great pair of home bookshelf speakers that are gathering dust. I have some Phase Technology V-4 speakers 8 ohm 90db. I was trying to sell them on ebay to finance new car speakers, but I can hardly get 1/2 their $300 value. Can I just disassemble them and have them installed in my car?


----------



## Candisa

If you use active processing (the passive filter network inside the speakerbox is designed for the speakers inside their box and in the living room) and make sure you don't blow them mechanically (because they are in a huge car door instead of a small box) by using a high pass filter on them (which you need to do with a caraudio component set too), it's definately worth giving it a try in your car!

greetings,
Isabelle


----------



## jasondplacetobe

i'll never shy away from 8 ohm again. thanks!


----------



## Candisa

And now this topic is bumped, if there are people reading this that still are in doubt: 
Download WinISD Pro and simulate a couple drivers of different sensitivities and impedances. You'll notice how irrelevant power really it!

For example: Xenia runs a Dayton IB385-8 subwoofer with only 100W on it, but it outperforms a LOT of subwoofers with twice or even more power on it!

PS.: If anyone finds a shop in the EU that still has the Dayton IB385-8: PLEASE send me a PM. Intertechnik (the EU main supplier for Dayton) doesn't list them anymore 

Isabelle


----------



## ManuelR

scar19 said:


> I have a 4 channel amp that I'm using to power the tweeters and mid-woofers on my 3Way active system. Currently, 2 channels are connected to the tweets at 4 Ohm and the other 2 channels are for the mid-woofers, also at 4 Ohm...
> Let's say I buy a set of 8 Ohm woofers, to exchange for the actual 4 Ohm ones that I have installed. Will the amp work fine? In this case, I would have 2 channels for the tweets at 4 Ohm and the other 2 at 8 Ohm! Is this possible? The amp is rated 4x75W RMS...





Chaos said:


> No problem. Keeping in mind the subject matter of this thread, you should be able to achieve similar output levels (provided that you choose drivers wisely) while putting less demand on your amp.


i have the exact same question as scar19, but i have already chosen my drivers wich are 

PEERLESS HDS 6.5 EXCLUSIVE NOMEX WOOFER....8ohm

and the

Vifa XT25TG30-04 1" Dual Ring Radiator Tweeter.....4ohm

is your answer still the same with my choice of woofers and tweeters?


----------



## chad

it will be just fine.


----------



## ManuelR

chad said:


> it will be just fine.


thx chad


----------



## ManuelR

ManuelR said:


> i have the exact same question as scar19, but i have already chosen my drivers wich are
> 
> PEERLESS HDS 6.5 EXCLUSIVE NOMEX WOOFER....8ohm
> 
> and the
> 
> Vifa XT25TG30-04 1" Dual Ring Radiator Tweeter.....4ohm
> 
> is your answer still the same with my choice of woofers and tweeters?





chad said:


> it will be just fine.


what about the GAINS ???? should they be similar or the 8ohms should have double the gain? or 25% more or something?


----------



## kyheng

Depending on situations... But usually you need to set the gain up a bit more.


----------



## hottcakes

they should probably be set so they do not send a clipped signal to the speakers. and so the levels sound matched with the volume up.


----------



## kyheng

Usually when using a 4ohm amp to drive an 8ohm drivers won't go into clipping. because the power output is reduced....


----------



## ManuelR

kyheng said:


> Depending on situations... But usually you need to set the gain up a bit more.


ok......how much more in %-----10% , 20%, 25%.....give me your best guess plz....



hottcakes said:


> they should probably be set so they do not send a clipped signal to the speakers. and so the levels sound matched with the volume up.


what do you mean with " be set"?


----------



## hottcakes

the gains should "be set" to their maximum unclipped level then turned down accordingly so nothing really overpowers anything else. i don't want to crap on this half-way decent thread. go to the "no question is dumb" and check out the sticky by nineball.


----------



## ManuelR

hottcakes said:


> the gains should "be set" to their maximum unclipped level then turned down accordingly so nothing really overpowers anything else. i don't want to crap on this half-way decent thread. go to the "no question is dumb" and check out the sticky by nineball.


this is what i get when i click tutorials----Invalid Forum specified. If you followed a valid link, please notify the administrator


----------



## kyheng

Wow, this question is really a good one, but sorry, I can't answer this as I'm not you. You have to use your ears to test it out.


----------



## tornaido_3927

ManuelR said:


> ok......how much more in %-----10% , 20%, 25%.....give me your best guess plz....
> 
> 
> 
> what do you mean with " be set"?


Just set your gains so they sound normal, in the same way you would do it with 4 ohm drivers. It doesn't make a difference that they are 8 ohm, gains are set the same way.

All drivers have different sensitivites and can handle different amounts of power, so we cannot tell you where to set your gains.


----------



## Ludemandan

Here's a question for you NPdang, referring back to the original post. I haven't read all 8 pages of the thread.

Silver Flute 4 ohm drivers have a sensitivity of 91.5 db. https://www.madisound.com/store/product_info.php?products_id=846

Silver Flute 8 ohm drivers have a sensitivity of 89 db. https://www.madisound.com/store/product_info.php?products_id=845

So by these numbers you would get slightly more than half the output from an 8 ohm driver as you would the 4 ohm driver. Is this example just an outlier? Is there something unusual about these speakers that makes the rated output roughly proportional to the power they'll let through?


----------



## tornaido_3927

Isn't that just because it would be measured with 2.83v instead of at one watt, meaning the 4 ohm driver is getting 2 watts while the 8 ohm one is getting one, hence 3dB?

Maybe you should have gone through the first page


----------



## subwoofery

tornaido_3927 said:


> Isn't that just because it would be measured with 2.83v instead of at one watt, meaning the 4 ohm driver is getting 2 watts while the 8 ohm one is getting one, hence 3dB?
> 
> Maybe you should have gone through the first page


^ yup... Need to read the thread. 

Kelvin


----------



## Ludemandan

Well, the reason I ask is because the first post suggests that efficiency rises with the construction of an 8 ohm speaker, otherwise you'd get half the output as you would from a 4 ohm version. 



> Remember, most speakers are rated at 2.83V. A 4 ohm speaker rated for 90db spl at 2.83v is really being rated at 2 watts! Whereas an 8 ohm speaker rated for 90db spl at 2.83v is only being rated at 1 watt. You can do the math for yourself, Power = Voltage^2 / resistance. At 2 watts, we can assume that same 8 ohm speaker is actually rated at 93db spl (remember, every doubling of power gives you a theoretical 3db gain in spl). So using that 8 ohm speaker will give you the same amount of output, at half the power required as a 4 ohm speaker.


I can't make sense of this. The last sentence seems to contradict everything else. Twice the impedance should give you half the current at a given voltage. Current is what causes inductance, which makes a speaker move. 

2.83V across 4 ohms yields ~.71A, for 2 watts. 2.83V across 8 ohms yields .35A, for 1 watt. Meaning you need twice the volts to get the same current through the speaker. Per watt it may be the same efficiency, but you get half the watts, thus half the output, with the 8 ohm speaker. This is basic. I don't see where he makes the jump to twice the resistance having the same output. 

There's an argument that efficiency should rise with impedance due to the BL rising. However, this isn't what I'm seeing in the driver specs. The specs on the drivers I posted above, if tested at 2.83V, seem to say you get half the output with twice the impedance.


----------



## tornaido_3927

Just below that quote you have there in the same post, it says;



> Efficiency = ( B^2 * L^2 ) / ( R * Sd^2 * Mms^2 )
> 
> B = magnetic field strength
> L = length of wire
> R = resistance
> Sd = surface area
> Mms = mass
> 
> So for your 8 ohm voice coil, using the same wire as a 4 ohm voice coil, you would need twice the L or length to get an 8 ohm impedance. That makes sense doesn't it? A longer wire will have more resistance. Now, looking at the formula above, doubling L actually causes your efficiency to rise, even though the impedance also rises. So in this very oversimplified example, raising the impedance actually causes efficiency to go up and lowering the impedance actually causes a loss of efficiency.


I hope that clears it up.. But also, do not get mixed up between loudness and efficiency, an 8 ohm driver will be more efficient but not louder (at 1w1m that is)

..I hope I got that right lol


----------



## Ludemandan

That doesn't solve the problem. What is the difference between efficiency and sensitivity? If they are different, then what is efficiency a measure of?


----------



## tornaido_3927

I said loudness and efficiency (which is sensitivity, ie. how efficiently the driver converts electrical power into acoustic power).

I think you are confused between the sensitivity of the driver compared to how loud it can get off of an amp driving a 4 ohm load at a certain wattage and then halving that output when it bumps up to 8 ohm.

In this case, the speakers are as sensitive as each other assuming the speakers are like the ones in the posts above. The 8 ohm one will however cause the amp to put out half(ish) the rated power of 4 ohms causing the 8 ohm driver to be 3dB less *loud* even though it has *the same efficiency/sensitivity*.


----------



## Ludemandan

tornaido_3927 said:


> The 8 ohm one will however cause the amp to put out half(ish) the rated power of 4 ohms causing the 8 ohm driver to be 3dB less *loud* even though it has *the same efficiency/sensitivity*.


This is my point. You get half the acoustic output when you double the impedance. The original post says that you get the same output when you double the impedance.


----------



## tRidiot

You get half the output if the sensitivity is identical... But usually it isn't when ypu compare. 3dB increase in sensitivity offsets that change in power available due to impedance doubling...


----------



## Ludemandan

Theoretically, yes, but with the drivers I posted above, the sensitivity is 2.5 decibels less with the 8 ohm driver.


----------



## Ludemandan

I just searched through all the 6"-7" drivers on Madisound that have identical 4 ohm and 8 ohm versions. The 8 ohm versions are almost always lower sensitivity than the 4 ohm versions.


----------



## ZAKOH

Here a hypothetical situation. I have a dual voice coil 4 ohm 300watt RMS sub. The amp has a 4ohm, 400 watt RMS channel. I can wire the sub voice coils in series to present 8ohm load to the amp. Will this work satisfactorily?


----------



## kyheng

Will work, don't worry.... If you like to see fancy numbers, your damping factor will be doubled when running 8ohm....


----------



## Ludemandan

ZAKOH said:


> Here a hypothetical situation. I have a dual voice coil 4 ohm 300watt RMS sub. The amp has a 4ohm, 400 watt RMS channel. I can wire the sub voice coils in series to present 8ohm load to the amp. Will this work satisfactorily?


This has been brought up several times and it is not what is being said.


----------



## javig999

I have a Kicker ZX700.5 that has been overheating. Loud listening levels and about 40 minutes and it shuts down. Not sure if this was normal so I wired the sub (Dual 4) to 8ohms (series) from 2ohm (parallel). I cannot tell if there is a loudness reduction. I kinda played with the gain a little bit on all the channels, but if, in theory, I am only pushing 105w to the sub (amp rated 420 @2, [email protected]), it sounds pretty damned good. If my overheating problem does not go away, I may opt for 8ohm mids as well...I have never really been happy with the RS180's anyhow...


----------



## subwoofery

javig999 said:


> I have a Kicker ZX700.5 that has been overheating. Loud listening levels and about 40 minutes and it shuts down. Not sure if this was normal so I wired the sub (Dual 4) to 8ohms (series) from 2ohm (parallel). I cannot tell if there is a loudness reduction. I kinda played with the gain a little bit on all the channels, but if, in theory, I am only pushing 105w to the sub (amp rated 420 @2, [email protected]), it sounds pretty damned good. If my overheating problem does not go away, I may opt for 8ohm mids as well...I have never really been happy with the RS180's anyhow...


That might not be an overheating issue only... Did you check your charging system? Going under 10V can also cause an amp to overheat and shut down. 

Kelvin


----------



## javig999

My lights did dim with the sub at 2ohms. They do do not dim now. I tested with AC on, interior lights on, and headlights on and no dimming anymore with the sub at 8homs. I do not have a voltage meter, but the 880PRS unit has a voltage indicator for entertainment purposes - not sure how accurate it is, but in the summer with AC on, and headlights on, never dipped below 12.9 or 13.0 - is this acceptable? Wouldn't the fact the lights aren't dimming now be an improvement? 

In the end I believe the amp has some serious issues, because running in this manner solved my heating problem, but when it heats up (not to the point of protection now) is when I am experiencing what appears to be a distorted signal to the tweeters. At the 2 ohm wiring of the sub, the distortion was on all the time, but with the sub wired at 8ohm, its only when it heats up - which now takes longer, but is still a problem. Unless my charging system is the culprit, I feel like a sub at 8ohms and the stereo channels at 4ohm should not be pushing this amp to heat up as it does.

Thanks for the input!


----------



## subwoofery

Which sub amp? 
How did you set your sub amp gains? 

I would say try to have your alternator and battery checked (I believe a couple of shops do it for free). 

Kelvin


----------



## t3sn4f2

Hhmmm the amp is stable at the impedance that you were having a problem with the tweeter. You move up to 8 ohms and the amp is still crapping on the tweeter when it heats up? Doesn't seem like that is something that should happen ever in a mass market protected amp.

Call Kicker and get it replaced if you can.


----------



## subwoofery

t3sn4f2 said:


> Hhmmm the amp is stable at the impedance that you were having a problem with the tweeter. You move up to 8 ohms and the amp is still crapping on the tweeter when it heats up? Doesn't seem like that is something that should happen ever in a mass market protected amp.
> 
> Call Kicker and get it replaced if you can.


^ you could do that too lol 

Kelvin


----------



## javig999

The sub amp is the sub section of the ZX700.5

The gains were set to about 75% - I knew I would not be overpowering that sub, and in tuning with with front stage, this is what worked best. 880PRS sub channel set to 0db or +1-2db depending on the music program.

I will test my charging system, but its strange that it only happens when the amp gets hot. And its stranger still that the amp gets hot running 8 and 4 ohm loads.

Kicker has provided an RA so its going back, I will fight them for a new one, but who knows what they will tell me...

Thanks again for all of your input...I will keep everyone updated.


----------



## Hertz5400LincolnLS

What does your electrical look like? Wiring, alternator, battery? Big 3 done?


----------



## subwoofery

javig999 said:


> The sub amp is the sub section of the ZX700.5
> 
> The gains were set to about 75% - I knew I would not be overpowering that sub, and in tuning with with front stage, this is what worked best. 880PRS sub channel set to 0db or +1-2db depending on the music program.
> 
> I will test my charging system, but its strange that it only happens when the amp gets hot. And its stranger still that the amp gets hot running 8 and 4 ohm loads.
> 
> Kicker has provided an RA so its going back, I will fight them for a new one, but who knows what they will tell me...
> 
> Thanks again for all of your input...I will keep everyone updated.


Gains set to about 75% doesn't tell us the gains have been set correctly. 
Try to do a search (on the forum) about gain settings. 
You might be clipping the sub output which might explain why the amp gets so hot. 
Wiring the amp from 2 ohm to 8 ohm, you did lose some output - then upping the gain to make up for the loss of output. 

Again, search about gain settings - no offense, just a suggestion... 

Kelvin


----------



## cvjoint

tornaido_3927 said:


> I said loudness and efficiency (which is sensitivity, ie. how efficiently the driver converts electrical power into acoustic power).
> 
> I think you are confused between the sensitivity of the driver compared to how loud it can get off of an amp driving a 4 ohm load at a certain wattage and then halving that output when it bumps up to 8 ohm.
> 
> In this case, the speakers are as sensitive as each other assuming the speakers are like the ones in the posts above. The 8 ohm one will however cause the amp to put out half(ish) the rated power of 4 ohms causing the 8 ohm driver to be 3dB less *loud* even though it has *the same efficiency/sensitivity*.


IMO this is why this thread confuses people. Maybe I don't understand this stuff yet but given the choice between an 8 ohm driver and the same one in 4 ohm, I would pick the 4ohm. The sensitivity increase in the 8 ohm driver is usually .5db not 3db, so all you are really doing is halving the power when you choose the 8 ohm route. 

The main example has the 8 and 4 ohm driver with the same V rating, which pretty much never happens. The 4 ohm is generally 3db higher in the same driver. So while the first example is technically correct it suggest to the average user that the 8ohm version of the same speaker ends up having the same output as the 4ohm which isn't true. Sure, it will be less than 3db down compared to the 4 ohm speaker, but the 4 ohm driver will be noticeably louder.


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## nosmose

^ this is what confuses me also. 

If I have the choice of 2 identical drivers:
1) 4ohms at [email protected]/M (50W RMS)
2) 8ohms at [email protected]/M (50W RMS)

Both would be power by a 45W RMS powerpack. Which would be the better choice?


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## subwoofery

nosmose said:


> ^ this is what confuses me also.
> 
> If I have the choice of 2 identical drivers:
> 1) 4ohms at [email protected]/M (50W RMS)
> 2) 8ohms at [email protected]/M (50W RMS)
> 
> Both would be power by a 45W RMS powerpack. Which would be the better choice?


Depends... Does your powerpack do 45W @ 8 ohm and 45W @ 4 ohm? 

Kelvin


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## nosmose

subwoofery said:


> Depends... Does your powerpack do 45W @ 8 ohm and 45W @ 4 ohm?
> 
> Kelvin


It's 4 channel, [email protected] not bridgeable. There is only a high/low gain switch. So I'm guessing that it will not supply much power to the 8ohms speakers and the 4 ohms would be the better option.


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## subwoofery

nosmose said:


> It's 4 channel, [email protected] not bridgeable. There is only a high/low gain switch. So I'm guessing that it will not supply much power to the 8ohms speakers and the 4 ohms would be the better option.


You got your answer all by yourself  

Kelvin


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## Metal Guru

nosmose said:


> It's 4 channel, [email protected] not bridgeable. There is only a high/low gain switch. So I'm guessing that it will not supply much power to the 8ohms speakers and the 4 ohms would be the better option.


The 4 ohm model would be better.

See post #30 in this thread:



notacop said:


> If both are rated 1w/1m you need to be 3db higher sensitivity to get the same output with 8 ohm vs 4 ohm


So based on that, for the 8 ohm version to be of any benefit, it would need to have a sensitivity of at least 93dB or higher for your situation.


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## supermotofan

Thanks to the Original Poster for answering my NOOB dumb question.

I am about to start my first install, and because I'm not really ready to do the whole thing yet, I figured I might power up the 4 Ohm 2-channel amp and run it to some 8 Ohm home speakers I have laying around. Seems like I'll be fine (for the time being, until my 4 Ohm speakers show up in the mail.

Thanks again.


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## adrenalinejunkie

So, if I was to have a JL AUDIO 300/2 (150x2 @ 1.5-4 OHM's) and a pair of Peerless XLS 8" (10MM XMax)with a DB of nearly 91DB and a pair of HAT 6 1/2 Clarus (12MM XMax) with a sensativity of 90.4DB, the Peerless should have more output due to it's cone area, right? What if the Peerless was a 6.5" just like the Clarus, would the Peerless still have equal output on 75 W since it's 8 OHM's?


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## TrickyRicky

adrenalinejunkie said:


> So, if I was to have a JL AUDIO 300/2 (150x2 @ 1.5-4 OHM's) and a pair of Peerless XLS 8" (10MM XMax)with a DB of nearly 91DB and a pair of HAT 6 1/2 Clarus (12MM XMax) with a sensativity of 90.4DB, the Peerless should have more output due to it's cone area, right? What if the Peerless was a 6.5" just like the Clarus, would the Peerless still have equal output on 75 W since it's 8 OHM's?


Use the formula's given on the first page (first post or post #1). That should give you the answer or atleast a better idea.


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## adrenalinejunkie

TrickyRicky said:


> Use the formula's given on the first page (first post or post #1). That should give you the answer or atleast a better idea.




I'm fairly new at this technical stuff and it just went over my head. :/ Maybe I can find someone that can help me out on this. Thanks


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## evangojason

A lot of good info here!


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## MUGWUMP

This thread helped me make a decision to get a pro audio driver for a midrange. I got in on the pre-purchase of the Melodic Acoustic Intimid8r 8" midwoofer and wanted something that would be a similar sensitivity as it. I ordered a pair of Faital Pro 3Fe22 8 ohm drivers. Still not sure what I'm going to do for a tweeter.

My question is will I be OK running these on 2 channels of my PDX-F4? It was specd at 121 watts per channel @ 4ohms. Do I have a chance of running them on the F4 or is it just gonna be too much even if the gain is down?


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## edzyy

MUGWUMP said:


> This thread helped me make a decision to get a pro audio driver for a midrange. I got in on the pre-purchase of the Melodic Acoustic Intimid8r 8" midwoofer and wanted something that would be a similar sensitivity as it. I ordered a pair of Faital Pro 3Fe22 8 ohm drivers. Still not sure what I'm going to do for a tweeter.
> 
> My question is will I be OK running these on 2 channels of my PDX-F4? It was specd at 121 watts per channel @ 4ohms. Do I have a chance of running them on the F4 or is it just gonna be too much even if the gain is down?


Yes..it's ok.

They'll appreciate the headroom


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## MUGWUMP

Thank you. 

I know when to back off the volume knob most of the time. I'm usually not trying to power them with close to 3x rated power though 

I suppose they're not too expensive if I burn them up. I'm also having second thoughts about them. I just learned about QTS and enclosures. These may not be ideal for ib in a door. Suppose it can't hurt to try it and see. Cars are really weird environments for sound so anything is possible.

Then you have the fact that I'm attempting my first active system. I wonder how long the Bit One is gonna take to learn  I know just enough to make me dangerous and I have all the tools needed.

...and it's a 3 way plus sub at that. LOL

Wish me luck!


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## Golden Ear

I was worried about how much power I'd be sending to a pair of dvc Jordans I'll be using until I read this thread. Great info! 75wpc at 8ohms should be perfect.


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## placenta

I came across this thread related to an issue I encountered last week. I used to come here a lot 10 years ago or so.

I am still struggling to understand the concept. My 2013 Charger SRT8 Superbee has the Alpine 6 speaker ~260W system. It has 3.5" dual cones in dash, 6x9 mids in front doors, and 6x9 2-way in the rear deck. I already replaced the whole front stage. The factory impedance for all 6 corners is 2 ohms, I have verified this at 1.7 ohm dry out of car. My Kicker 3.5" 2-way upgrade in dash seemed to work well. I lost no volume, and the highs are much more noticable. It also brought up my stage height quite nicely. Probably because its a couple 4 ohm's wired in parallel to keep the factory resistance the weak factory amp likes. Where I had a big problem is when I did the Kicker 6x9 1-ways into the front doors. They are confirmed 4 ohm. (3.6 ohm dry). They were not even detecable anymore, and the rear deck 2-way 6x9's completely overpowered the whole car, bringing my stage to towards the back seat. I put my stock 6x9's back in shortly after that to restore the balance.

I was going for a very minor upgrade, no interest in changing any amps or decks. So per the first post in this thread, how is the 4 ohm speaker going to match the volume and quality, when I am used to a 2 ohm volume level? I have no idea what the sensitivity rating is on either speaker, all i know was the volume was cut in half. I don't want to swap out the rear 6x9's also, as then all 4 6x9's would be much quieter and my dash speakers would move into the overpowering role.

I did check PartsExpress for any 1-way 2 ohm 6x9's and found nothing. I like 6x9's and don't really want to switch to 6.5", this car is a lease. As minor modifications as possible.


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## jimmybee1108

So morel mdt12s are 8ohm tweeters that require 80 watts rms. 
does this mean I need to find an amp that puts out 160 watts at 4 ohm?


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## jimmybee1108

So morel mdt12s are 8ohm tweeters that require 80 watts rms. 
does this mean I need to find an amp that puts out 160 watts at 4 ohm?


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## chad

jimmybee1108 said:


> So morel mdt12s are 8ohm tweeters that require 80 watts rms.
> does this mean I need to find an amp that puts out 160 watts at 4 ohm?


If you give those tweets 80 watts your eyes will fall out of your head.


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## jimmybee1108

chad said:


> If you give those tweets 80 watts your eyes will fall out of your head.


Could you recommend a good amount to give?


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## spyders03

You can give them whatever you can afford (within reason). Just because they are rated at 80 watts, does not mean that you couldn't give them 40 watts rms, or even 100. No speaker will ever be damaged from giving it too little power, if this was true, anyone that listened to their stereo under half volume would have blown speakers. Don't over drive your amp trying to compensate for more power, and you will be fine with whatever you give them.


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## jimmybee1108

So my plan, ppi p900.4 (140 at 4 ohms) and then maybe gain it down?


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## t3sn4f2

jimmybee1108 said:


> So my plan, ppi p900.4 (140 at 4 ohms) and then maybe gain it down?


That's fine. It's a non issue unless you go to the extremes really. IE 25 watt @ 4 ohm on an small format 3/4" 8 ohm tweeter, or a large format very sensitive 4 ohm tweeter receiving 300 watts from a bridged channel pair. Anything in between that, which is typical what you would have to choose from is fine. No one ever complains about them needing more power or having too much if you don't fall within those extremes. And even then you might still be ok.

For you though, like most others, just pick the 4 channel amp based on what you want to give the mid and the remaining 2 channel is what you tweeter gets regardless of anything else.


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## chad

Mine were fine, as are/were any other tweet on that car off if the "rear channels" of a JL 500/5. (25WX2 rated)


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## spyders03

A tweeter crossed over at 5k well only use about 10% of the rated power of the amplifier.

http://diymobileaudio.com/forum/showthread.php?t=152187

A very good read also http://sound.westhost.com/tweeters.htm

Swyped while swerving


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## chad

spyders03 said:


> A tweeter crossed over at 5k well only use about 10% of the rated power of the amplifier.
> 
> [


No, if the required level would need 10W they will get 10W no matter if the amp is 25W or 10 KW


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## rideexileex

Going to bump this thread since it seems somewhat relevant to the question I have. I took a long break from the audio scene, and have old equipment which I assumed to be 2 ohm stable. Upon re-reading the manuals, the amplifier I have is only stable at 4 ohms when bridged (which surprised me). The biggest shock for me was the non x2 factor with the 2 to 4 ohm power ratings.

Amp:
JBL / Crown
Px600.2
• 180W RMS x 2 channels at 4 ohms and <1% THD + N
• Signal-to-noise ratio: 79.5dBA (reference 1W into 4 ohms)
• 663W RMS x 1 channel at 4 ohms, 14.4V supply and
<1% THD + N
• 290W RMS x 2 channels at 2 ohms, 14.4V supply and
<1% THD + N
• Dynamic power: 692W at 4 ohms x 1 channel
• Effective damping factor: 6.274 at 4 ohms
• Frequency response: 10Hz – 97.5kHz (–3dB)
• Maximum input signal: 5.95V
• Maximum sensitivity: 264mV
• Output regulation: .056dB at 4 ohms

Sub:
JL 10w6v2
Dual 4ohm coils, so (to state the obvious, 2 ohm parallel / bridged ***not an option for me*** , 4 ohm wired as stereo from amp, or 8 ohm series wired bridged / mono)

So what's the best recommendation for utilizing the amp? It seems I'd get the 180Wx2 = 360W if the coils are wired separately, which is far less than the 663W rating for a bridged setup at 4 ohms, which in my case is a 8ohm load. It's hard to say without knowing how the amplifier behaves, but would I just assume that the 663W would remain the same for the 8ohm load, just with the amp working at half the current? Or, from the non x2 factor with the wattage between the 2 to 4 ohm amp ratings, do you think the amp wattage might actually increase more with the 8ohm load?


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## Yourconfused

Misleading title and the assumptions are just that, but whose to say that an amp is more efficient at 8ohms vs 4,2,1,etc? This is all just situation dependent and makes this pointless.
OP must have never had a cheater amp. pfft
Thanks for the effort though.
(I only read the first post and saw no reason to go further in such a long thread)


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## Bayboy

Come on man....


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## Yourconfused

Bayboy said:


> Come on man....


Yeah, it's old, but you make it an open sticky so you get what you get.


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## I800C0LLECT

*Re: The &quot;Real Deal&quot; with 8 ohm drivers*

Besides just throwing out an opinion... Care to explain why it's wrong?


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## Hoye0017

Just found another person to put on my "ignore" list. Even the username is arrogant.


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## Bayboy

*Re: The &quot;Real Deal&quot; with 8 ohm drivers*

Being that a current trend is to power up via bridging or staggered power setups, I don't see the issue here. Besides, cheater amps? Not in popular use on this forum

Sent from my SM-G900V using Tapatalk


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## captainobvious

Yourconfused said:


> Misleading title and the assumptions are just that, but whose to say that an amp is more efficient at 8ohms vs 4,2,1,etc? This is all just situation dependent and makes this pointless.
> OP must have never had a cheater amp. pfft
> Thanks for the effort though.
> (I only read the first post and saw no reason to go further in such a long thread)


1. It's not a misleading title. People have confusion about this topic...clearly.
2. Where was the assumption?
3. It's very reasonable that an amplifier driving a less resistive load will run cooler. 

The main focus of this thread was to point out the method in which speakers sensitivities are calculated and why that is important when considering 4ohm vs 8ohm (or other impedance) speakers as many people simply look at a sensitivity rating and go no further.


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## Yourconfused

Yes, less heat is better for the amp, but has nothing to do with efficiency, within reason.

The post makes it seem like 8 ohm drivers are actually more efficient, given his own math that checks out but is a classic apple to potato comparison. 

I'll use Morel (see attached pic) as my example where comparing 3 pairs of their drivers in 4ohm to the 8 ohm variants, paints a much different picture than what the OP has conveyed. I think that those 3 examples there are as good of an apple to apple comparison as you will find. (I am assuming here that the manufacture didn't misprint the specs)

Same thing goes for these scan speak drivers:
https://www.madisoundspeakerstore.c...ak-revelator-18w/8531g-00-7-mid-woofer-8-ohm/
https://www.madisoundspeakerstore.c...speak-revelator-18w/4531g-7-mid-woofer-4-ohm/


I guess I could have read and argued about the rest of his post, but just kinda stopped there. Yeah I was being lazy and looking for something interesting and different, which is why I was looking at stickies.


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## Yourconfused

Hoye0017 said:


> Just found another person to put on my "ignore" list. Even the username is arrogant.


If I were to have used the spelling and therefore implied meaning of "you're" instead of "your", that would be arrogant of me; but being as it is you just made me chuckle. I chose that spelling to annoy a grammar nazi friend of mine about 15 yrs ago, and keep using it so I can be tracked from one forum to the next, as I have nothing to hide and it's all in jest.


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## Bayboy

Yourconfused said:


> Yes, less heat is better for the amp, but has nothing to do with efficiency, within reason.
> 
> The post makes it seem like 8 ohm drivers are actually more efficient, given his own math that checks out but is a classic apple to potato comparison.
> 
> I'll use Morel (see attached pic) as my example where comparing 3 pairs of their drivers in 4ohm to the 8 ohm variants, paints a much different picture than what the OP has conveyed. I think that those 3 examples there are as good of an apple to apple comparison as you will find. (I am assuming here that the manufacture didn't misprint the specs)
> 
> Same thing goes for these scan speak drivers:
> https://www.madisoundspeakerstore.c...ak-revelator-18w/8531g-00-7-mid-woofer-8-ohm/
> https://www.madisoundspeakerstore.c...speak-revelator-18w/4531g-7-mid-woofer-4-ohm/
> 
> 
> I guess I could have read and argued about the rest of his post, but just kinda stopped there. Yeah I was being lazy and looking for something interesting and different, which is why I was looking at stickies.


Look at impedance curves & pay more attention to efficiency than mere small signal measurements. Still not a big deal unless the drivers vary widely anyway. Just not getting what your point is on this thread other than to just cause a ruckus. Perhaps a mod should come in and clean this up and you can start your own thread for debate & discussion rather than mess up a timeless thread.


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## Yourconfused

Bayboy said:


> Look at impedance curves & pay more attention to efficiency than mere small signal measurements. Still not a big deal unless the drivers vary widely anyway. Just not getting what your point is on this thread other than to just cause a ruckus. Perhaps a mod should come in and clean this up and you can start your own thread for debate & discussion rather than mess up a timeless thread.


So what I am gathering here is that despite the impedance variant (being the the 8ohm is around 26hz for a peak and the 4ohm is around 42hz) the VC winding's due to wire size and weight, my randomly googled drivers presented here, which are otherwise the same drivers, and not some fictitious drivers, which actually show the 8 ohm to be less efficient than the 4 ohm; all 8 ohm speakers are more efficient and therefore despite the amp delivering less power are capable of producing the same output, or better, and while all presenting less of a load on the amp, which results in less heat and a better time for the amp? Are those things even going to be crossed over low enough for those peaks to be an issue? I suppose that in a 2 way bookshelf or the like, they might be playing anything below the LF passband and in theory could come into play. That's just not a typical thing for a mobile application in my mind. (I am pretty sure those were run-on sentences. :laugh

I guess that I don't see the elephant in the room here. Please paint the elephant pink for me. 

Not being an ass (today anyway lol), but I just found the premise that the argument was based upon to be flawed, or misrepresented. No offense to the OP intended.

(I'll work on reading the entire thread now, but that will take me about a week, as I am bad at looking at any one thing too long.


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## DC/Hertz

None of this is set in stone. Things change once more then 1w is applied. Compression takes effect. 
Then it comes down to the drivers sensitivity vs amplifier power.


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## Yourconfused

Yes, power compression is annoying and usually shortens the life of the speaker once that becomes a factor. 
My point remains, and the sky is not blue if you are color blind. (not just directed at you DC, but in general)
unsubscribed


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## Bayboy

The whole point of this thread was for people not to fret if what they wanted to use only came in 8 ohm. The examples used were drivers of similar sensitivity and showing the difference between a starting point 1 watt for 8 ohm & 2 watts for 4 ohm. Do the math and you will see that 8 ohm is still a viable option despite power output by the amp being halved, essentially making the compared drivers' output equal. It's a simple equation that needs no debate, and no, it's not the end all be all answer to which driver to use. The rest to compare are still up to the user.


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## I800C0LLECT

*Re: The &amp;quot;Real Deal&amp;quot; with 8 ohm drivers*

This attitude generally ruins forums and the internet is general. Bayboy hit it on the head. The point of this op was to help people understand speaker ratings and that in MAJORITY of the speakers available, the difference in sensitivity will remove concerns for overall output... Making 8ohm drivers a viable option.

The op is a speaker designer and realizes that their are caveats or exceptions. I don't know if you're attempting to establish your reputation or have another motivation but it's self serving. If you want to identify every exception for the sake of education that's awesome. But you've made your comments with a tone that seems spiteful. So really, you aren't adding to the forum. You're just trying to tear down the idea that seems inspired with a superiority complex.

You seem like a smart guy. Come back with a better attitude and you'll be well received


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## wheelieking71

Yourconfused said:


> Misleading title and the assumptions are just that, but whose to say that an amp is more efficient at 8ohms vs 4,2,1,etc? This is all just situation dependent and makes this pointless.
> OP must have never had a cheater amp. pfft
> Thanks for the effort though.
> (I only read the first post and saw no reason to go further in such a long thread)


You are a ****ing idiot.
This is one of the greatest threads (and most important read) ever in the history of car-audio specific internet forums.
And, i have read many many threads. I go all the way back to the ECA days. And, this is still the most important thread I have ever read.


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## pliedtka

Holly ****...
Ideal amp with stable power supply that is able to provide tons of current to amplifier section without dropping voltage on rails should in theory double the power (current) for every time impedance drops in half of the initial value. So amp ratted [email protected] should have [email protected], [email protected], and so on. However this requires a lot of silicone and doping, big capacitors, coils and transformers w. high ga., lot of cooling surface. The amplifier section: VAS (voltage amplification), driver and output design is very important as it needs to be efficient, very stable so the amp doesn't start to oscillate, also keep the distortions low with increasing current demands. So reality kicks and only most efficient designs with plenty of silicone will do 'double the power - half ohm' rule. Most amps do 60-70% doubling of power. Please also keep in mind that loudspeakers are complex impedance devices where inductive and capacitive components change with voltage level and position of the voice coil in the motor - thanks Klippel ?.
Bob Cordell wrote excellent book on audio amplifiers, Jan Didden of Linear Audio, and many others wrote a lot on amp design. Check Audio Critic by Peter Aczel who had some interesting articles and ways of testing power amps.


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## t3sn4f2

pliedtka said:


> Holly ****...
> Ideal amp with stable power supply that is able to provide tons of current to amplifier section without dropping voltage on rails should in theory double the power (current) for every time impedance drops in half of the initial value. So amp ratted [email protected] should have [email protected], [email protected], and so on. However this requires a lot of silicone and doping, big capacitors, coils and transformers w. high ga., lot of cooling surface. The amplifier section: VAS (voltage amplification), driver and output design is very important as it needs to be efficient, very stable so the amp doesn't start to oscillate, also keep the distortions low with increasing current demands. So reality kicks and only most efficient designs with plenty of silicone will do 'double the power - half ohm' rule. Most amps do 60-70% doubling of power. Please also keep in mind that loudspeakers are complex impedance devices where inductive and capacitive components change with voltage level and position of the voice coil in the motor - thanks Klippel ?.
> Bob Cordell wrote excellent book on audio amplifiers, Jan Didden of Linear Audio, and many others wrote a lot on amp design. Check Audio Critic by Peter Aczel who had some interesting articles and ways of testing power amps.


Yup, you don't wanna did down below 4 ohms unbridged unless you have a very good amp. Even then I wouldn't for anything other than the lower midbass and sub region. Which is where the power is typically really used/needed, as well as the audibility of distortion goes wayyyy down.

typical amp:


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## lurch

T3sn4f2

i " think " i understand this graph, but could you please elaborate for me ?

not sure what the cap/ res / in and other acronyms stand for, and how the scale actually
works.


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## Holmz

lurch said:


> T3sn4f2
> 
> i " think " i understand this graph, but could you please elaborate for me ?
> 
> not sure what the cap/ res / in and other acronyms stand for, and how the scale actually
> works.


The capacitive and inductance in degrees of phase make sense.

However what is the Z axis? I do not see any label on that.


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## t3sn4f2

The Z-axis is a power level, not actual though just relative. As you can see, as the load becomes more difficult (ie lower impedance and greater phase shift) the power begins to sag. Typically it only matters with passive speaker systems, as the combination of more than one driver and the passive's own properties leads to a complex impedance and phase interaction. Active setups don't have that problem since it's only one component seen by the amp and they don't begin to have a significant phase shift until you get close to the resonance peak on the low end and out of the speakers ability to play on the high end. Below is an impedance and phase plot for a fullrange passive home speaker and a single SB Acoustics 6.5" graph from ErinH's MedleysMusings site as an example. 

MartinLogan Prodigy









http://medleysmusings.com/category/speaker-driver-tests/midwoofers/









Here's more on the cube.

audiograph – Home of the PowerCube
https://www.ap.com/technical-library/measuring-power-amplifiers-with-reactive-loads/


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