# Some sub considerations for the DIY



## DeltaB (Jun 17, 2017)

Speaker selection is an important consideration in any quality system. And one of the most important, is low frequency, and how to obtain truly impressive performance, without the common mistakes made when designing this critical section of frequencies.

There is much more to consider when selecting subwoofers, their implementation and overall balance of the system. This is where Thiele-Small parameters dictate enclosure design and sizing, and one commonly ignored. There is much more to designing this system than just buying a driver and cabinet. The mechanical and electrical Q of a driver has to be properly matched to the cabinet. And one size (diameter) doesn’t match all cabinets. And any subwoofer driver not inside an enclosure, will not produce the effect you are seeking. The trunk itself doesn’t count, as it doesn’t match the Thiele-Small parameters of the driver originally used.

Rule #1, any sub driver outside a properly matched cabinet is only half a subwoofer.

Rule #2, never disconnect the driver from the cabin of the vehicle. You cannot overlook this rule, and often attempted. Disconnected designs where you place a sub in a cabinet, and place it in the trunk, is not a desirable design in any system. Imagine taking your home audio system in your listening room, and placing the subwoofer in the garage. The only result that will produce, is a very muddy, and over emphasized port chuffing monster that doesn’t lend itself to high quality reproduction… all it creates is noise. When you place a driver outside of the cabin, you lose the intricacies of the lower frequencies needed to reproduce music accurately. The primary frequency of low A (A-0) of a piano is 27.5Hz, and its second even harmonic is 55Hz, and it’s third even harmonic is 110Hz. And that’s only one example. These subtle harmonics are lost in disconnected designs, and lower volume levels will lose all detail.

And using that same piano note as an example, it is important that the amplifier is phase accurate, especially in this arena. It’s why attention to an amplifier’s signal path is so important, and why so much attention is paid in that area. It is the foundational building block to accurately create sinusoidal waves for the drivers. This is the arena in which realism and soundstage is created, those subtle harmonics and vibrato that are created during the recording process.

Another critical area, is the damping factor of the amp you connect your subwoofer to. This is one area that is misunderstood by many, and seldom executed well. As you decrease resistance, you decrease the damping factor of your amp. It’s why you should find a solution that has only one driver per amplifier channel, and at least 4 ohm. 2 ohm designs or less, while able to create more load, and in the end, more current, (watts) however, it is not conducive to damping factor. The amp has to be able to control driver excursion, and the closer one gets to 2 or 1 ohm, the less ability that amp will be able to control it. The net result is poor performance. Also, using anything less than 10 gauge wire for subs is not recommended. An amplifier that has a damping factor of 500 at 4 ohm, will be reduced to around 100 by using only 5ft of 14 gauge, and at 2 ohm it is almost 50. Damping factors that are at least >100 is a general rule for minimum, and the higher, the better. The function of using large wire gauge (10 gauge or larger) is not for current, but the amount of voltage drop.

*From Crown*; "Loudspeakers have a mind of their own. You send them a signal and they add their own twist to it. They keep on vibrating after the signal has stopped, due to inertia. That's called "ringing" or "time smearing." In other words, the speaker produces sound waves that are not part of the original signal. Suppose the incoming signal is a "tight" kick drum with a short attack and decay in its signal envelope. When the kick-drum signal stops, the speaker continues to vibrate. The cone bounces back and forth in its suspension. So that nice, snappy kick drum turns into a boomy throb. Fortunately, a power amplifier can exert control over the loudspeaker and prevent ringing. Damping is the ability of a power amplifier to control loudspeaker motion. It's measured in Damping Factor, which is load impedance divided by amplifier output impedance. High damping factor equals tight bass."

The goal is to find a subwoofer driver that matches the wattage rating of the amp, placed in a properly designed cabinet to match its Thiele-Small parameters, and connected to the cabin of the vehicle, without using the boot as the enclosure itself.


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## Holmz (Jul 12, 2017)

DeltaB said:


> ...


Holy smokes, I was expecting 10 rules...


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## Bayboy (Dec 29, 2010)

Any relative info can be found on this site by doing a search. However, I suspect you will find many may disagree with the "disconnect" theory.


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## DeltaB (Jun 17, 2017)

Bayboy said:


> Any relative info can be found on this site by doing a search. However, I suspect you will find many may disagree with the "disconnect" theory.


It is what it is. I try to keep it in simplistic terms. But time and SPL alignment is lost in disconnected designs. It doesn't matter how you try to shape it. There are some basic rules in play here, no matter the opinion of others.


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## I800C0LLECT (Jan 26, 2009)

I disagree with most of it. But anybody willing to research can figure that out.


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## Bayboy (Dec 29, 2010)

DeltaB said:


> It is what it is. I try to keep it in simplistic terms. But time and SPL alignment is lost in disconnected designs. It doesn't matter how you try to shape it. There are some basic rules in play here, no matter the opinion of others.


Any specific reason you're trying to "keep it in simplistic terms"?


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## DeltaB (Jun 17, 2017)

Bayboy said:


> Any specific reason you're trying to "keep it in simplistic terms"?


It's a public forum. 

I will say this though, I'm keenly aware there are lots of various opinions when it comes to audio. It's kind of like the quote from Crown Audio Engineering that I quoted above, who is one of the most respected professional audio companies out there, and certainly know loudspeaker, and it's interaction with various designs. And invariably someone who will come up and have a differing opinion. That's okay with me.


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## I800C0LLECT (Jan 26, 2009)

Your quote from Crown Audio Engineering didn't support anything you said. I agree with some aspects, like understanding T/s.

But... Rule #1: you build a cabinet based on performance expectations. I agree.

Rule #2: what does disconnected from the cabin mean? A sub in the trunk can do very well. Your example of a disconnected cabin design doesn't make sense. If it was as critical as you say then we'd all have hatchbacks and SUVs on this forum.

Dampening factor... Read about that on this forum and it's generally considered an issue for theorists. You cover that by stating how misunderstood and uneducated most are... But don't provide any evidence or argument otherwise.

Your op doesn't provide a good foundation for argument. It seems inflammatory more than anything


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## Bayboy (Dec 29, 2010)

DeltaB said:


> It's a public forum.
> 
> I will say this though, I'm keenly aware there are lots of various opinions when it comes to audio. It's kind of like the quote from Crown Audio Engineering that I quoted above, who is one of the most respected professional audio companies out there, and certainly know loudspeaker, and it's interaction with various designs. And invariably someone who will come up and have a differing opinion. That's okay with me.



I still don't understand your point in that. Public forum, yes. But are you hinting at the forum is full of people that can't comprehend the level you claim? 

As far as opinions. Not sure what that has to do with factual aspects. By factual, I mean actual proof from measurements. There's plenty of technical write ups on here to show that most here are not beyond reason when relative proof is provided. But I digress... I've got a dual opposed manifold to finish up and would like to hear the results before this day is over with.


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## DeltaB (Jun 17, 2017)

Bayboy said:


> I still don't understand your point in that. Public forum, yes. But are you hinting at the forum is full of people that can't comprehend the level you claim?


I'm not eluding to anything. "If you can't explain it simply, you don't understand it well enough." - Albert Einstein



> As far as opinions. Not sure what that has to do with factual aspects. By factual, I mean actual proof from measurements. There's plenty of technical write ups on here to show that most here are not beyond reason when relative proof is provided. But I digress... I've got a dual opposed manifold to finish up and would like to hear the results before this day is over with.


Measurements are great, that I agree. But it doesn't replace ears. Two simple rules above were, you need a cabinet that meets speaker Q, and, you can't disconnect the driver from the cabin. The rest is info you should know.


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## I800C0LLECT (Jan 26, 2009)

DeltaB, if you're attempting to contribute a How-to-article then the burden of proof lies on you. Otherwise, you didn't contribute anything but an opinion. You can't justify the how-to with "if you understood, then I wouldn't have to explain..."

My teachers never taught anything that way.


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## Holmz (Jul 12, 2017)

I800C0LLECT said:


> DeltaB, if you're attempting to contribute a How-to-article then the burden of proof lies on you. Otherwise, you didn't contribute anything but an opinion. You can't justify the how-to with "if you understood, then I wouldn't have to explain..."
> 
> My teachers never taught anything that way.


Hence my reference in post #2.

I just need to figure out how to link to the picture of Charlton Heston carrying those tablets.

,<edit>
Thy Sub shall be done thusly...


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## GEM592 (Jun 19, 2015)

Holmz said:


> Hence my reference in post #2.
> 
> I just need to figure out how to link to the picture of Charlton Heston carrying those tablets.


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## DeltaB (Jun 17, 2017)

I800C0LLECT said:


> DeltaB, if you're attempting to contribute a How-to-article then the burden of proof lies on you. Otherwise, you didn't contribute anything but an opinion. You can't justify the how-to with "if you understood, then I wouldn't have to explain..."
> 
> My teachers never taught anything that way.


I'm not into your contention. You don't pay me enough to be your instructor. If there is one thing the matriculation process should have taught you, and in turn the most important thing any teacher can teach you, is how to do research, filter that research, and apply the things learned from that research. Obviously, philosophy of education wasn't your major.

It does appear though, you don't like what is being said. And that's your "opinion." Have a great day.


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## Holmz (Jul 12, 2017)

In the spirit of helping, it "sounds" like a 4-ohm sub is recommended over a 2-ohm.
I have 300W at 4-ohms and 500W at 2-ohms.
For a SQ setup should I run a 8" or 10" sub at 4-ohm?
Can a difference be heard?


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## Jscoyne2 (Oct 29, 2014)

Holmz said:


> In the spirit of helping, it "sounds" like a 4-ohm sub is recommended over a 2-ohm.
> I have 300W at 4-ohms and 500W at 2-ohms.
> For a SQ setup should I run a 8" or 10" sub at 4-ohm?
> Can a difference be heard?


Ohms dont matter at all other than power. There is zero audible different other than loudness


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## DeltaB (Jun 17, 2017)

Holmz said:


> In the spirit of helping, it "sounds" like a 4-ohm sub is recommended over a 2-ohm.
> I have 300W at 4-ohms and 500W at 2-ohms.
> For a SQ setup should I run a 8" or 10" sub at 4-ohm?
> Can a difference be heard?


The first thing to recognize, is that SQ is not a function of power, but one of control. When I was at Altec-Lansing before Mark IV Industries sold the brand to Chinese in the late 90's, many hours were spent in the anechoic chamber looking at just this very issue. Amplifier design, and it's output impedance varies widely on it's class, it's engineering design, and the devices in the output stage itself. But in general, you will find control becomes aggressively out of control with driver combinations getting as low as 2 ohm or less, especially at higher SPL, which lends nothing to SQ. The larger the mass, (the larger the driver) the harder it becomes to control at high excursion. To answer your question, "can it be heard?" Yes. And an anechoic chamber proves it time and again when you compare the input signal against the output of the driver/cabinet. General rule of thumb, the higher the damping factor, the less overshoot will be seen. SQ is found in control of the driver, so that it reproduces faithfully the input.

*Courtesy of Crown*;

http://www.acorn-designs.com/articles/133472.pdf
Please pay attention to pages 14 & 15. And as I stated before the desired DF of >100, Crown recommends upwards of 500.

*Courtesy of EAW*;

Amplifier damping factor (DF) is defined as “the ratio of the load impedance (loudspeaker plus wire resistance) to the amplifier internal output impedance.” This basically indicates the amplifier’s ability to control overshoot of the loudspeaker, i.e., to stop the cone from moving. It is most evident at frequencies below 150 Hz or so where the size and weight of the cones become significant. A system where the damping factor of the entire loudspeaker/wire/amplifier circuit is very low will exhibit poor definition in the low frequency range. Low frequency transients such as kick drum hits will sound “muddy” instead of that crisp “punch” we would ideally want from the system.

The formula for calculating damping factor is










Where:

Z L = The impedance of the loudspeaker(s)

Z AMP = The output impedance of the amplifier

R W = The resistance of the wire times 2 for the total loop resistance.

Very few amplifier spec sheets state the output impedance, but you can generally call the manufacturer for this spec or you can calculate it by dividing the minimum rated load impedance by the damping factor rating. For example, if we are using amplifier with a damping factor rating of 400 and it requires a minimum load of 2 Ohms, then its output impedance would be calculated as being 0.005 Ohms.

For example…

So let’s look at several examples and figure out what we can control in the design of our system to achieve the best results. Say we have two 8 ohm subwoofers connected to an amplifier with a damping factor of 400 with 100’ of 12 ga. wire with a resistance of 0.00159 Ohms/ft times 100’ gives us a total resistance of 0.159 Ohms. Plugging the numbers into our formula, we get:










In this case, our system damping factor is just 12. Most experts agree that a reasonable minimum target DF for a live sound reinforcement system would be 20, so we need to consider changing something to get this up.

The critical element in this definition is the “loudspeaker plus wire resistance” part. In this case, the resistance in 100’ of 12 ga. wire with a 4 Ohm load results in around 0.7 dB of loss, much greater than the maximum target of 0.4 dB of loss, so let’s try bigger wire. 10 ga. wire has a resistance of .000999 Ohms/ft times 100’ equals .0999 Ohms and will get us to the 0.4 dB target. What will it do for DF?










Ok, now we’re pretty close to the 20 we were looking for. Notice that the loudspeaker impedance can also give us a big change. The higher the circuit impedance, the less loss we have due to wire resistance. What if we change our wiring so we have one 8 Ohm loudspeaker connected instead of two? Going back to our 12 ga. wire, we calculate:










Even better! In fact, if you run the numbers a few times, you will see that in a system with some significant length of wire, we will find that damping factor will generally be 20 or higher as long as our total wire loss is 0.4 dB or less.

What if we have a self-powered subwoofer? In this case, our loudspeaker wire is probably around 14 ga. and since the amplifier is in the loudspeaker enclosure, it is probably less than a couple feet long. Assuming the manufacturer is connecting two 8 ohm loudspeakers to the amplifier, and 14 ga. wire has a resistance of .00256 Ohms/ft times 2’ equals 0.00506 Ohms of resistance, and our amplifier has a damping factor spec of 400, what do we get?










Wow! Now that’s a significant difference! Kind of supports the idea of using self-powered subwoofers, or at least putting the subwoofer amps as close as possible to the subs.

Amplifier DF Ratings

So we’ve looked at the differences in the size and length of our wire and the differences in hanging one loudspeaker on the line vs. two to change the impedance of the line. What if we choose an amplifier with a higher damping factor spec., say 3000? That’s a big difference, so we should see a much higher damping factor in our circuit, right? Assuming this amplifier can drive a minimum 2 Ohm load, we find the output impedance would be 0.001 Ohms. Plugging the numbers into our single loudspeaker with 12 ga. wire system, we get:










Hmmmm, not such a big deal. That higher amplifier damping factor only improved our system damping factor by 0.31 over the amplifier with a DF spec of only 400.

What if we use the amplifier with the 3000 DF spec in our self-powered sub with 2’ of 14 ga. wire?










Remember our calculation using the 400 DF amplifier was 264.55, so now we start to see when the amplifier spec becomes significant. Essentially, in sound reinforcement systems where we have some significant length of wire between the amplifier and the loudspeaker, the amplifier DF spec has little affect on the performance of the system.

In Summary…

So what have we learned? In live sound reinforcement systems, damping factor is really driven by the length and size of our wire and the impedance of the loudspeakers we connect at the other end. Since damping factor mostly affects low frequency, we should endeavor to keep our subwoofer loudspeaker lines as short as possible and/or use larger gauge wire. We should keep the impedance of the connected load as high as possible by connecting only one transducer per wire instead of two.

So is more amplifier damping factor better? As one of my colleagues recently said, “Sure! If the loudspeaker terminals are welded to the amplifier output terminals!” Well, maybe he overstated it a little bit, but yes, as long as the loudspeaker wire is really short, then by all means!


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## I800C0LLECT (Jan 26, 2009)

I'm not sold on damping issues. I think it's a crusade for perfection through theory

http://www.audioholics.com/audio-amplifier/damping-factor-effects-on-system-response


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## DeltaB (Jun 17, 2017)

I800C0LLECT said:


> I'm not sold on damping issues. I think it's a crusade for perfection through theory
> 
> Damping Factor: Effects On System Response | Audioholics


Transistor amps didn't exist until the 60's, so research from 1934 when Fritz did his work "Radiotron Designer's Handbook" when tubes reigned supreme, transformer based output reacts quite differently to load.


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## SPLEclipse (Aug 17, 2012)

OK, I'l bite.

How does the amp control cone motion and how does damping factor play a role? If we're so worried about cone control, why isn't inductance included in the above calculations? Given the answers to these, what is the approximate contribution that amplifier damping has on cone control compared to mechanical/electromechanical deficiencies of the sub and enclosure?


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## Holmz (Jul 12, 2017)

I suppose that the other way to consider it is that 500W is about 600w, which is 3dB high SPL than 300W, so I give up 3dB of SPL.

A subwoofer with an SPL of 82dB/w + 24-dB (300w) yields an SPL of 106dB.
(Maybe that is not dBA.)

So the question remains, is that enough SPL for general use without it being designed as a thumpfest?


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## DeltaB (Jun 17, 2017)

SPLEclipse said:


> OK, I'l bite.
> 
> How does the amp control cone motion and how does damping factor play a role? If we're so worried about cone control, why isn't inductance included in the above calculations? Given the answers to these, what is the approximate contribution that amplifier damping has on cone control compared to mechanical/electromechanical deficiencies of the sub and enclosure?


The voice coil resistance is a key factor in limiting the amount of damping that can be achieved electrically, because its value is larger (say between 4 and 8Ω typically) than any other resistance in the output circuitry of an amplifier that does not use an output transformer (nearly every solid-state amplifier on the mass market). I said this before but bears repeating;

*From Crown*; "Loudspeakers have a mind of their own. You send them a signal and they add their own twist to it. They keep on vibrating after the signal has stopped, due to inertia. That's called "ringing" or "time smearing." In other words, the speaker produces sound waves that are not part of the original signal. Suppose the incoming signal is a "tight" kick drum with a short attack and decay in its signal envelope. When the kick-drum signal stops, the speaker continues to vibrate. The cone bounces back and forth in its suspension. So that nice, snappy kick drum turns into a boomy throb. Fortunately, a power amplifier can exert control over the loudspeaker and prevent ringing. Damping is the ability of a power amplifier to control loudspeaker motion. It's measured in Damping Factor, which is load impedance divided by amplifier output impedance. High damping factor equals tight bass."

A loudspeaker's flyback current is not only dissipated through the amplifier output circuit, but also through the internal resistance of the loudspeaker itself. Therefore the choice of different loudspeakers will lead to different damping factors when coupled with the same amplifier. (this is why selection of driver/cabinet/amp selection is important in SQ)

The driver's motor itself is an inductor. And it resides in a magnetic field, which also makes it a generator.

Mechanical Q (driver loading) is accomplished by the cabinet. Damping factor will not help you much in deficiencies of a poorly matched driver/cabinet.


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## DeltaB (Jun 17, 2017)

Holmz said:


> I suppose that the other way to consider it is that 500W is about 600w, which is 3dB high SPL than 300W, so I give up 3dB of SPL.
> 
> A subwoofer with an SPL of 82dB/w + 24-dB (300w) yields an SPL of 106dB.
> (Maybe that is not dBA.)
> ...


A 3dB increase in power does not equate to a doubling of SPL. Sorry.


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## I800C0LLECT (Jan 26, 2009)

DeltaB said:


> Transistor amps didn't exist until the 60's, so research from 1934 when Fritz did his work "Radiotron Designer's Handbook" when tubes reigned supreme, transformer based output reacts quite differently to load.


What does that have to do with that article? That book wasn't referenced.

In your above response, he didn't even mention "doubling SPL" but you negated his question with that.


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## Holmz (Jul 12, 2017)

DeltaB said:


> A 3dB increase in power does not equate to a doubling of SPL. Sorry.


How does it work then?
The speakers have numbers associated with them in terms of dB/watt.
So I assume I push an RMS watt in, and I should get the exact SPL dB/watt that they are rated at.

So if I have the amp cranked up to 3 dBW, then what does that equate to in a SPL dB(s) change compared to when it was at 0-dBW?


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## DeltaB (Jun 17, 2017)

I800C0LLECT said:


> What does that have to do with that article? That book wasn't referenced.
> 
> In your above response, he didn't even mention "doubling SPL" but you negated his question with that.


The information from the article was taken from Fritz's work, and is referenced at the summation of that article.


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## DeltaB (Jun 17, 2017)

Holmz said:


> How does it work then?
> The speakers have numbers associated with them in terms of dB/watt.
> So I assume I push an RMS watt in, and I should get the exact SPL dB/watt that they are rated at.
> 
> So if I have the amp cranked up to 3 dBW, then what does that equate to in a SPL dB(s) change compared to when it was at 0-dBW?


A speaker's sensitivity measurement, (i.e. 83dB/1w-1m) is a measurement of the ability of the driver to create a given SPL at 1 watt measured at 1 meter. This does not mean a doubling of power (2watt) will create 166dB/2w-1m, or that 4 watts (again a 3dB increase in power) will create 322dB/4w-1m.

Loudness volume doubling sound level change factor of perceived loudness decibel scale log compare intensities formula calculate power level noise levels volume logarithm dependence three four fold loudness sound - by what factor does level decrease


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## Holmz (Jul 12, 2017)

DeltaB said:


> A speaker's sensitivity measurement, (i.e. 83dB/1w-1m) is a measurement of the ability of the driver to create a given SPL at 1 watt measured at 1 meter. This does not mean a doubling of power (2watt) will create 166dB/2w-1m, or that 4 watts (again a 3dB increase in power) will create 322dB/4w-1m.
> 
> Loudness volume doubling sound level change factor of perceived loudness decibel scale log compare intensities formula calculate power level noise levels volume logarithm dependence three four fold loudness sound - by what factor does level decrease


I am aware that when working in LOG space we add the number.
So my understanding is that...:
0dBW = 1W
3dBW = 2W
10dBW - 10W
20dBW = 100W
26dBW = 400W

Question1: Is the conversion of watts to dBW consistent with your understanding?

Question2: Does 1W give 83dB of SPL?

Question3: what does 2W yield?
(I am pretty confident that it is closer to 86dB of SPL than 166dB of SPL)


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## mzmtg (Dec 8, 2009)




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## Holmz (Jul 12, 2017)

Jscoyne2 said:


> Ohms dont matter at all other than power. There is zero audible difference other than loudness


The context was that I can get the same brand of subwoofer as either
1) 2-Ohms
2) 4-Ohms

The amp is rated at:
1) 500W (2-Ohms)
2) 300W (4-Ohms)

So I am tryng to understand whether the extra watts from a 2-Ohm is:
A) needed?
B) worthwhile?
C) lower SQ than the 4-Ohm?


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## I800C0LLECT (Jan 26, 2009)

DeltaB said:


> The information from the article was taken from Fritz's work, and is referenced at the summation of that article.


I'm not the brightest bulb. I looked everywhere on that page for that reference. Could you identify where on that page it's located? It's definitely not published there... Was it a link?


DeltaB said:


> A speaker's sensitivity measurement, (i.e. 83dB/1w-1m) is a measurement of the ability of the driver to create a given SPL at 1 watt measured at 1 meter. This does not mean a doubling of power (2watt) will create 166dB/2w-1m, or that 4 watts (again a 3dB increase in power) will create 322dB/4w-1m.
> 
> Loudness volume doubling sound level change factor of perceived loudness decibel scale log compare intensities formula calculate power level noise levels volume logarithm dependence three four fold loudness sound - by what factor does level decrease


His question revolved around how much SPL is enough? If you're going to start arguing theory again then you should also include the fact that the vehicle is a bass machine so to speak. I have measured C-weighted response in the mid 130's with a 10" sub sitting in the spare tire well.

So if doubling power doesn't exactly produce +3dB of output I'm certain cabin gain more than makes up for it.


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## I800C0LLECT (Jan 26, 2009)

At this point, these rabbit trails aren't adding to the conversation and anybody "researching" should have enough information to make a choice. Good luck and take care


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## DeltaB (Jun 17, 2017)

Holmz said:


> I am aware that when working in LOG space we add the number.
> So my understanding is that...:
> 0dBW = 1W
> 3dBW = 2W
> ...


Q1: dBW is a unit for the measurement of the strength of a signal, not SPL

Q2: The driver itself determines the amount of SPL (it's sensitivity) it can produce at 1 watt at 1 meter. (the use of 83dB/1w-1m was simply an example)

Q3: This is where you ran off the tracks before by equating 300W to 600W as 3db of SPL. What you have compared is a leftover from a prior question concerning a rating into an amplifier's rating at a given load value, which may not change SPL at all. You can refer to the information I have already left for that explanation.


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## I800C0LLECT (Jan 26, 2009)

Holmz said:


> The context was that I can get the same brand of subwoofer as either
> 1) 2-Ohms
> 2) 4-Ohms
> 
> ...


My opinion is that you can make that choice based on personal circumstance, finances, already available hardware, or other factors. The difference in SQ and output won't be meaningful. I post this everywhere... But I'll do it again... The car adds more variation to response than anything else. It simply isn't worth arguing over .01% of theoretical performance.

Damping?! Are you kidding me?!


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## Holmz (Jul 12, 2017)

DeltaB said:


> Q1: dBW is a unit for the measurement of the strength of a signal, not SPL
> 
> Q2: The driver itself determines the amount of SPL (it's sensitivity) it can produce at 1 watt at 1 meter. (the use of 83dB/1w-1m was simply an example)
> 
> Q3: This is where you ran off the tracks before by equating 300W to 600W as 3db of SPL. You can refer to the information I have already left for that explanation.


We seem to have a communication problem.

Question1 dealt with conversion of watts to dBW

In Question2 I used your SPL value of 83 dB/watt.
I assume that watts*(dB/Watts) => dB (At least the units are consistent)

Question 3 follow question2, You have not provided any illumination other than that a factor of 2 does not multiply the SPL by 2. And I agree when working in dB one adds the numbers.

I tried to make this easy for you to provide a straight forward answer in an obtuse fashion. However it seems like your understanding is tightly held. If you do not wish to answer the question then that is you prerogative. Since it seems like you were providing some sage considerations for DIY, I held out the olive branch.


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## Holmz (Jul 12, 2017)

I800C0LLECT said:


> My opinion is that you can make that choice based on personal circumstance, finances, already available hardware, or other factors. The difference in SQ and output won't be meaningful. I post this everywhere... But I'll do it again... The car adds more variation to response than anything else. It simply isn't worth arguing over .01% of theoretical performance.
> 
> Damping?! Are you kidding me?!
> View attachment 187722
> View attachment 187730


I got it clearly - Thanks.

So the question I have now is where does one start?

I figured I would get stuck into sound proofing and treatment once I had speakers and amps in my warm paws.
(Another box with what is likely an amp just today)

Then some adjustment of amp gains and measurements to get some measured sound that is reminiscent of the input signal. Whether or not I apply an EQ to it I still need the speakers, amps and wiring in place and generally working.

I have about 1/2 to 2/3 of a system, so I getting an appropriate subwoofer and amp for the levels seems worthwhile.

Should I just assume that 300W is a decent amount of subwoofer, if the vehicle is not being designed to be obviously going duuff-duuff with stupid high bass levels? and then just call it a day?

Basically I kind of want to avoid an endless merry-go-round of upgrades...
That would probably cost me more in the long term.


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## Bayboy (Dec 29, 2010)

Again, a quick search within this forum will turn up all that is needed to the importance of damping factor as well as other aspects. A lot has been covered over the years here, but most fail or refuse to read it. 

Sent from my SM-G955U using Tapatalk


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## DeltaB (Jun 17, 2017)

Holmz said:


> We seem to have a communication problem.
> 
> Question1 dealt with conversion of watts to dBW
> 
> ...


You're confusing two domains. Electrical (power) ratio to express power or amplitude ratios, to acoustic pressure levels or the effective pressure of a sound relative to a reference value. Both are expressed in a log scale of dB, but they are not the same. There is no magic here. Educate yourself rather than offering off-hand insults to me for your poor understanding. Start with the site I left you.


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## Holmz (Jul 12, 2017)

DeltaB said:


> There is no magic here. Educate yourself rather than offering off-hand insults to me for your poor understanding. Start with the site I left you.


It is not an of-handed insult when I mentioned that we are having a failure to communicate. From my perspective we clearly are, and I am not sure how much clearer I can be.



DeltaB said:


> You're confusing two domains. Electrical (power) ratio to express power or amplitude ratios, to acoustic pressure levels or the effective pressure of a sound relative to a reference value. Both are expressed in a log scale of dB, but they are not the same.


But I'll try again...
I believe I am fairly well educated in the basics.
So my understanding of an amplifier is that it supply voltage (or power) to the speaker.
I have not seen units for SPL on an amp, it is always watts, and measurements are usually performed in the voltage domain with a know ressitive-load (however one could measure current and voltage)

The speaker is a transducer that converts electric energy into acoustic (mechanical) energy.

I believe that I have a decent enough understanding of these two domains:
- The speaker will not produce any sound without an amplifier
- The amplifier will not produce any sound without the speaker.
- The combination of amplifier and speaker together result in acoustic energy.




DeltaB said:


> ... Both are expressed in a log scale of dB, but they are not the same.


So we have a spec like 83 dB/Watt.
We use 1W (0dBW) 
We get SPL = 83dB/W * 1W/1dBW = 83dB SLP referenced at 0dBW
Then for any #-dBW we have
SPL = 83 dB + #-dBW
So 2 watts is 86 dB (SPL)

I am hearing that you are saying that the math is incorrect.
(It should be 10LOG10 or 20LOG10)


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## I800C0LLECT (Jan 26, 2009)

My bad... My response was more directed at the reader than it was you 

I think the problem most run into is matching sub output with their mids. If they aren't leveled properly I noticed most people presume they need more subwoofers, power, etc.

Again... Not squarely directed at you. I think measurements will shine the light on system deficiencies. Once identified, you tackle from there.... Even post! And people will gladly try to help.

As far as the op... Don't mistake activity for accomplishment

Anyways, these topics don't need to be rehashed. Lates!


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## DeltaB (Jun 17, 2017)

I800C0LLECT said:


> Damping?! Are you kidding me?!


This is a non sequitur as it relates to the issue of DF.


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## DeltaB (Jun 17, 2017)

Holmz said:


> It is not an of-handed insult when I mentioned that we are having a failure to communicate. From my perspective we clearly are, and I am not sure how much clearer I can be.
> 
> But I'll try again...
> I believe I am fairly well educated in the basics.
> ...


You won't ever see SPL from an amp rating. SPL is dependent on a speaker's efficiency, your distance from it, and the amount of power you place into it.



> The speaker is a transducer that converts electric energy into acoustic (mechanical) energy.
> 
> I believe that I have a decent enough understanding of these two domains:
> - The speaker will not produce any sound without an amplifier
> ...


But that understanding doesn't by reason of knowing it, make dBW a measurement of SPL or vice-versa.



> So we have a spec like 83 dB/Watt.
> We use 1W (0dBW)
> We get SPL = 83dB/W * 1W/1dBW = 83dB SLP referenced at 0dBW
> Then for any #-dBW we have
> ...


If you are looking at a theoretical limit, you cannot exclude distance. Same 83dB/1w-1m moved to 10m will experience a drop of 20dB of SPL.


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## SPLEclipse (Aug 17, 2012)

DeltaB said:


> A loudspeaker's flyback current is not only dissipated through the amplifier output circuit, but also through the internal resistance of the loudspeaker itself. Therefore the choice of different loudspeakers will lead to different damping factors when coupled with the same amplifier. (this is why selection of driver/cabinet/amp selection is important in SQ)
> 
> The driver's motor itself is an inductor. And it resides in a magnetic field, which also makes it a generator.
> 
> Mechanical Q (driver loading) is accomplished by the cabinet. Damping factor will not help you much in deficiencies of a poorly matched driver/cabinet.


Agreed. Let's move one to the point I was trying to make: worrying about how amp damping effects acoustic damping is like worrying about how hitting a mosquito on the drag strip increases your 1/4 mile time. Reducing ringing is much, much better addressed through motor design (like shorting paths), enclosure optimization, and acoustic treatment within the car.

[...]

Oh Boy. I was just looking up an article to cite on the audibility of an amp's damping factor and it looks like everything the OP is posting is copy pasted from a few sites.

EAW: Eastern Acoustic Works | Amplifier damping factor: More is better! (….or is it?)

https://en.wikipedia.org/wiki/Damping_factor

Most of what the OP has said is directly copied from those two sites. No wonder he can't directly answer the questions.


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## Bayboy (Dec 29, 2010)

Well, none of the links and associated writings are being held as false. I think all agree in general to what they say. What's in dispute again and again is to what magnitude are these issues in a car? To quote a site basing it's principles in pro audio where wire length certainly affects damping factor, yet on a car audio site where such lengths are not being used, that pretty much belittles the argument to almost worthless. No different than using an example of a subwoofer being disconnected by being in a different room, but fails to research or include how transparent rear seats are with a trunk installed sub. 

Surely a trip to this section (and a few others) will save some time:

Car Audio Truth, Myths & Industry Dogma - Car Audio | DiyMobileAudio.com | Car Stereo Forum


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## Bayboy (Dec 29, 2010)

An excerpt from elsewhere within the site (as I've state again, where plenty relative info is located):

http://www.diymobileaudio.com/forum/605531-post11.html


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## DeltaB (Jun 17, 2017)

SPLEclipse said:


> Agreed. Let's move one to the point I was trying to make: worrying about how amp damping effects acoustic damping is like worrying about how hitting a mosquito on the drag strip increases your 1/4 mile time. Reducing ringing is much, much better addressed through motor design (like shorting paths), enclosure optimization, and acoustic treatment within the car.
> 
> [...]
> 
> ...


I cited the sources, and I said it early on, "I will say this though, I'm keenly aware there are lots of various opinions when it comes to audio. It's kind of like the quote from Crown Audio Engineering that I quoted above, who is one of the most respected professional audio companies out there, and certainly know loudspeaker, and it's interaction with various designs. And invariably someone who will come up and have a differing opinion. That's okay with me.


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## DeltaB (Jun 17, 2017)

Bayboy said:


> Well, none of the links and associated writings are being held as false. I think all agree in general to what they say. What's in dispute again and again is to what magnitude are these issues in a car? To quote a site basing it's principles in pro audio where wire length certainly affects damping factor, yet on a car audio site where such lengths are not being used, that pretty much belittles the argument to almost worthless. No different than using an example of a subwoofer being disconnected by being in a different room, but fails to research or include how transparent rear seats are with a trunk installed sub.
> 
> Surely a trip to this section (and a few others) will save some time:
> 
> Car Audio Truth, Myths & Industry Dogma - Car Audio | DiyMobileAudio.com | Car Stereo Forum


You're more than welcome to your own opinion, however that is your own opinion. And there is no shortage of those here. Hope you have a great day.


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## Bayboy (Dec 29, 2010)

And this is where another problem comes in. So now the straddling of the fence in saying all that you present is relevant facts, and anything outside of that is mere opinion, then you touch it with a bit of passive aggressiveness? Quite rude. Up to this point there has been no useful debate or even friendly talk. You simply only care to dictate. Hope you have a great day as well. I'm done here. 

Sent from my SM-G955U using Tapatalk


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## Holmz (Jul 12, 2017)

DeltaB said:


> You won't ever see SPL from an amp rating. SPL is dependent on a speaker's efficiency, your distance from it, and the amount of power you place into it.
> 
> 
> 
> ...



Your echoing back that an amp is not rated in SPL is consistent with my claim.

I have never seen a vehicle with a 20m sound stage other than possibly an airplane.

I suppose I am a bit slow, as I am just getting to the point where I am thinking this is a trolling session.

Showing up like Moses with the tablets, and then when reasonable questions that were germane to your DIY subwoofer discussion are asked, getting a response along the lines of "the mysteries of the universe are beyond comprehension" seems to be somewhat evasive.

You either understand this stuff or you do not.

As we are at a communication impasse, it is time that I move on and not further detract from your message.


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## DeltaB (Jun 17, 2017)

Bayboy said:


> And this is where another problem comes in. So now the straddling of the fence in saying all that you present is relevant facts, and anything outside of that is mere opinion, then you touch it with a bit of passive aggressiveness? Quite rude. Up to this point there has been no useful debate or even friendly talk. You simply only care to dictate. Hope you have a great day as well. I'm done here.
> 
> Sent from my SM-G955U using Tapatalk


Get a mic, place it on a stand, hit your sub with 40Hz for 1s at 1w. Record the ring. This is easily tested. I'm not interested in the contention folks. You have a great day.


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