# Bridging amp for midbass speaker ?



## Robb (Dec 5, 2008)

Is it fine to bridge an amp for midbass speakers ? 
The midbass speaker will play from 63hz till 4000hz.
Wil I lose alot of SQ ?


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## fish (Jun 30, 2007)

Yeah, people do it all the time.


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## nick650 (Feb 7, 2011)

Not ideal but it can be done.


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## dragonrage (Feb 14, 2007)

Robb said:


> Is it fine to bridge an amp for midbass speakers ?
> The midbass speaker will play from 63hz till 4000hz.
> Wil I lose alot of SQ ?


Just be careful not to overpower them. People love to claim that they run 400WRMS to their mids and stuff but that's pretty much always BS - mids WILL blow. Do NOT believe the asses that claim 'You can run as much power as you want as long as it's clean' because that is absolutely not true. Especially if you are playing them down to 63Hz (as opposed to, say, 80Hz).


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## hottcakes (Jul 14, 2010)

http://www.diymobileaudio.com/forum/diyma-sq-forum-technical-advanced/74089-bridging-amps-sq.html


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## Robb (Dec 5, 2008)

hottcakes said:


> http://www.diymobileaudio.com/forum/diyma-sq-forum-technical-advanced/74089-bridging-amps-sq.html


Thanks.


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## michaelsil1 (May 24, 2007)

dragonrage said:


> Just be careful not to overpower them. People love to claim that they run 400WRMS to their mids and stuff but that's pretty much always BS - mids WILL blow. Do NOT believe the asses that claim 'You can run as much power as you want as long as it's clean' because that is absolutely not true. Especially if you are playing them down to 63Hz (as opposed to, say, 80Hz).


I recently blew a Mid Bass Driver Crossed @ 80Hz 18db Slope. 

I have my Mid Bass Amps Bridged and I'm not losing any SQ.


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## Robb (Dec 5, 2008)

michaelsil1 said:


> I recently blew a Mid Bass Driver Crossed @ 80Hz 18db Slope.


Frying voicecails ? :laugh:

btw, how much power are you throwing @ the midbass ?


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## michaelsil1 (May 24, 2007)

Robb said:


> Frying voicecails ? :laugh:
> 
> btw, how much power are you throwing @ the midbass ?


460 Watts RMS per Mid Bass.


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## subwoofery (Nov 9, 2008)

michaelsil1 said:


> 460 Watts RMS per Mid Bass.


And you want us to feel sorry for you???  

Kelvin


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## nick650 (Feb 7, 2011)

GOOD GOD! And my subs only get 300 each!


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## TrickyRicky (Apr 5, 2009)

It must be a 4-channel amp (atleast thats what I would use if I was to bridge channels).We all know subwoofers that produce under 100hz or so can be bridged and wont make a difference but by bridge do you mean using both left and right midbass in one output? You'll loose all channel separation if this is what your asking. Will it make a big difference, may, maybe not it depends on how much channel separation is in the music your listing to, if the signal is mono then no difference. I notice that a lot of the new music in rap, hip hop don't have much channel seperation. But then you got classical, orchestra that have major channel separation.

Its like some Beatles songs especially those from the Magical Mystery Tour album, all those had lots of channel separation.

And as far as SQ, I doubt you'll loose any, or any thats noticable.


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## fish (Jun 30, 2007)

I just assumed you meant a 4-channel amp bridged. Is that what you meant Robb?


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## nervewrecker (Oct 5, 2009)

I have 150 watts available per midbass but I go easy on them & keep the extra headroom so I dont have to push my amps to the limit.


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## michaelsil1 (May 24, 2007)

subwoofery said:


> And you want us to feel sorry for you???
> 
> Kelvin


No, I was just pointing out that even crossing the Mid Bass @ 80 Hz you still have to be sane.


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## sqshoestring (Jun 19, 2007)

In practice it should work fine. In my opinion if you run them lower you should use a good quality 4ch or a 2ch, because cheaper 4ch tend to not have as large a power supply and even outputs. They appear to be designed to run half the amp bridged on sub and not the whole amp. If you run a lot of power at 80Hz or below they might not work as well. Remember any boost or higher gain in the midbass will dial up the power to this amp significantly. People tend to push them because they are using a pretty small driver to make high bass.


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## pionkej (Feb 29, 2008)

There is seriously zero problem with bridging a 4-channel amp down to 2-channels for your midbass (or turning your 5-channel amp into a 3-channel--or turning your 2-channel amp into a mono) as long as the amp can handle whatever impedance load you are using. I have done this in nearly half my installs and never blown a speaker.

Second, there is NOTHING wrong with giving tons of power to your speakers. If they don't need it...they don't use it. I'm pretty sure my math is right in the example I'm about to give, but someone please correct me if I'm wrong.

Example:

-A speaker needs power to be increased by a factor of 10x to handle a 10db peak.
-A speaker can handle large amounts of power for brief periods of time (dynamic peaks)

* If you have a speaker playing at just 10w (most speakers use very little power at moderate volume) and are listening to dynamic music that has 10db peaks, you need 100w to cover that peak without clipping the amp.

* If you have a speaker playing at just 10w and are listening to dynamic music that has 18db peaks (it does happen), you need 1000w to cover that peak without clipping the amp.

The problem people (that I've personally experienced) run into with cooking speakers when using high-power amps is that they will tune using well-recorded, dynamic music. You set your max volume to that. You then put in some current pop music with 3db peaks and don't adjust the volume...

It really is true that you can't have too much power. The problem is that it gets VERY expensive and typically takes up a lot of room. Since most of these peaks are very brief and your amps and speakers can both tolerate some clipping, you end up with the law of diminishing returns. How much is that clean power worth? This is especially true in a car where rattles/buzzes introduce their own forms of distortion that can easily mask the gains you get from all that clean power.

I will finish with one last comment, and that is that you CAN tell a difference when setup properly. I sat in Kirk Proffit's car at Erin's last GTG, and it had tons of power to each speaker...but was also deadened to back it up. He could turn the volume up on Money for Nothin (a very dynamic song) to a point where it was litreally painful to hear and it was still perfectly clean and clear sounding.


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## dragonrage (Feb 14, 2007)

Ugh. What an awful post.

First of all, putting a one million watt amp with gain control on a speaker does NOT mean that you are feeding the speaker one million watts. Do not tell us that you're running a million watts to your speakers.

Secondly, power WILL blow speakers whether it is clipping or not. The ONLY difference between a clipped signal and a clean signal is that during sections of clipping, the driver is not moving, which means that there is not airflow to help cool the voice coil. While this does make a driver blow a bit easier, it is NOT that big a factor. The overall power is a MUCH bigger factor than how clean said power is. A sine wave will heat up a voice coil the same as a square wave or even DC of the same power level. Again, the only difference is that you get the best cooling when driving a sine wave. And, again, that cooling is not going to save your driver from extreme power levels at all. The only way to handle more power is a bigger voice coil, but that will limit upper frequency response considerably due to a major increase in moving mass (Mms). Increase it enough and you've turned your woofer into a subwoofer, and you'll need a 3-way setup. (Not that I advocate against that!)

My MB Quart Q4.150 is EASILY capable of blowing my Rainbow Profi Kicks without being bridged. But I'm not a dumbass, so that won't be happening... hopefully, anyway.

Yes, if you're driving a 'baseline' power level of 10W and you come to a 20dB peak (not 18dB), your amp would drive 1000W if it is capable of doing so. But you'd better damn well hope that it's for a DAMN short amount of time because that will blow ANY 6.5/7" midbass driver VERY quickly.

There is NO REASON to put 400W worth of amp per channel on a midbass speaker. Period.


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## pionkej (Feb 29, 2008)

dragonrage said:


> Ugh. What an awful post.
> 
> First of all, putting a one million watt amp with gain control on a speaker does NOT mean that you are feeding the speaker one million watts. Do not tell us that you're running a million watts to your speakers.
> 
> ...


Sorry, but it's not an aweful post. It can be done when done properly and you adjust the volume according to the content you are listening to. 

And 10w on a properly deadened car will be plenty loud enough for everyday listening. Lets say you are listening to a speaker that has an efficiency of 85db. That is 85db at 1w/1m. Let's say you are 2m away (generous), that's a 6db reduction (correct?), but you're running 10w so you're back at 89db. You have two speakers (L and R) which roughly equates to a 3db gain for any information that is centered (L+R) and you are now at 92db. This IS a rough approximation and I'm on a crappy "remote" computer at work where I can't check my math, but it should be pretty accurate.

I also said that dynamic peaks ARE very brief and speaker would rather have 1000w of clean power than a 100w amp TRYING to hit 1000w and clipping.

I do apologize for one thing however and that is not typing "almost". As in a 18db peak will need "almost" 1000w to play cleanly.


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