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Discussion Starter #1
Could anyone please share his experience in this?
I am not interested in serial or parallel wiring of sub, or what ohm should the amp be working at.

What i am trying to understand is what happens in terms of volume and sound quality?

Just comparing 400Wx1-4ohm(1 sub) to 200Wx2-4ohm(2 subs)

also would there be any difference in 2 subs setup, using separate left/right channels for bass compared to using dual mono?

so which one is preferred?

400Wx1 mono, 200Wx2 left/right or 200Wx2 dual mono

thanks a lot in advance
 

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Could anyone please share his experience in this?
I am not interested in serial or parallel wiring of sub, or what ohm should the amp be working at.

What i am trying to understand is what happens in terms of volume and sound quality?

Just comparing 400Wx1-4ohm(1 sub) to 200Wx2-4ohm(2 subs)

also would there be any difference in 2 subs setup, using separate left/right channels for bass compared to using dual mono?

so which one is preferred?

400Wx1 mono, 200Wx2 left/right or 200Wx2 dual mono

thanks a lot in advance
Am confused, in mono are you still going to have 2 subs or just 1?

Second if your having 2 subs on both wiring set ups and assuming your going to end up with 400watts total in both set ups, then I dont think there will be a difference.

In subwoofers (low frequency) the signal is almost always combined (mono) so it wouldn't matter if you have a left and right channel separation in woofers.

Now if your asking how will 1 woofer at 400watts compare to 2 woofers at 200watts each, then you bet your ass the 2 woofers at 200watts will be louded simply because of cone area.

But this questions cannot be simply answered, it depends on how well the enclosures are built. 1 woofer in a perfect enclosure can out do multiple woofers in a crappy enclosure. Even smaller single woofer can out do multiple bigger woofers. Trust me I've seen it done.
 

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I once had 3 12" woofers in a pretty well built enclosure (all three chambers were equal in area) and the woofers were Xtant X124's with a single 600watt (mono) rockford X5 amplifier and it out performed this other guys system which he thought his was louder simply because he had 5 12" woofers (dont remember the brand but am pretty sure they were cheapies) and had a 2000watt pyramid or pyle amplifier.

We compared both systems and no doubt mine was way louder and deeper, he couldn't believe I had 3 12's at 600watts compared to his suppost to be 2000watt 5 12's set up.
 

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umm, duh! that is like saying "I raced this guy in my ferrari and I won, he had a toyota corrola"

his 2000 watt pryamid prolly put out 200watts for real
 

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umm, duh! that is like saying "I raced this guy in my ferrari and I won, he had a toyota corrola"

his 2000 watt pryamid prolly put out 200watts for real
 

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umm, duh! that is like saying "I raced this guy in my ferrari and I won, he had a toyota corrola"

his 2000 watt pryamid prolly put out 200watts for real
Yeah I know, but the guy didnt know **** about amplifiers or woofers, so he automatically thought just because he had five 12's and a 2000watt (wink wink) amplifier that his set up was louder than my three 12's 600watt set up.

But besides that, what is your comment on what -ToR- is asking or seeking advise on.
 

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Yeah I know, but the guy didnt know **** about amplifiers or woofers, so he automatically thought just because he had five 12's and a 2000watt (wink wink) amplifier that his set up was louder than my three 12's 600watt set up.

But besides that, what is your comment on what -ToR- is asking or seeking advise on.
for what he is asking. (1) 12" at 400w or (2) 12" at 200watts each. all things being exactly the same. the (2) 12" will be louder. you have the same amount of power with more drivers, gonna be louder. only 3dB louder, which IMHO is not worth the extra space and expense.
 

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for what he is asking. (1) 12" at 400w or (2) 12" at 200watts each. all things being exactly the same. the (2) 12" will be louder. you have the same amount of power with more drivers, gonna be louder. only 3dB louder, which IMHO is not worth the extra space and expense.
Yep, twice the cone area will be louder. To get the single sub to have roughly the same output as the two subs you would need twice as much power as the two subs. Simple math, 'A change in power ratio by a factor of two is approximately a 3 dB change."

As for wiring it to the left and right channel or going mono? Go mono, which sums up the left and right. Sub woofer frequencies are very hard to localize, especially in a car, and having discrete left and right subwoofers is pointless, especially in a car. If you go mono both subs will be playing the same signal together....which is mo-better. :D

I think you are just trying to understand the theory behind your questions and not really thinking of doing it, correct? If you are actually considering running two 4ohm subs on a 2-channel amp then you should really get a 2ohm stable amp and run the two subs in parrallel and bridge the amp. Which brings us back to "A change in power ratio by a factor of two is approximately a 3 dB change." but this time you get it relatively free!
 

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I would go with the two subs louder with the same total amount of watts. For me the main reason for going with the two subs over 1 is less excursion wich equals less distortion.
 

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Discussion Starter #10 (Edited)
Thanks a lot for all the responses.
Let me try to be a bit more clear on what exactly i'm trying to determine.

first consider setup1 with two separate amps;
1 x 220W RMS/500W MAX (0.04% THD @ 4ohms - NFB)
each to be wired to a 200W RMS, 200 mm (8"), 4 ohm, 90dB subwoofers
(Magnat - Transforce Reference 120BP)

now consider setup2 with one amp;
1 x 300W RMS/600W MAX (0.1% THD @ 4ohms - NFB)
to be wired to a 400W RMS, 300 mm (12"), 4 ohm, 93dB subwoofer
(Magnat - Transforce Reference 130BP)

to make things more interesting and for comparison sake, consider both setups not to be tested at higher than 90dB and both setups are connected combined mono (following TrickyRicky's advise for mono).

Having louder bass with 2 subs as TrickyRicky, Baada and boogeyman indicated is a definite plus but i feel what boogeyman says about less excursion and less distortion is more interesting.

now, since in both setups the total considered volume is also same, wouldn't using one subwoofer create a clearer/better sounding bass compared to using two?

I am trying to understand besides all effects, if there would be any interference between the signals produced by the two subwoofers?

Also, to add more confusion, the 220W amp would be about 0.3% THD without the NFB on, but the 300W amp would be about 1% THD without the NFB on.

What do you recommend? It seems like everything is pointing to a setup with two subs but call me crazy i just can not be sure if two subs would produce a clearer bass? Why home theater amps are normally 5.1 but not 5.2 for example? (amp channels, not source channels)

Also in two amp setup, should one of the signals be inverted?

Thanks a lot
 

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Well this one guy I know has a 76 Mustang with racing tires and this other guy I know has a 96 Camry with all season touring tires and I am trying to figure out which car will charge my phone better through the cigarette lighter:poke:


Okay your post isn't that bad but wow...that's a lot of variables.

1. 8"s are going to have a different sound and presence than 12"s....even with all else being as equal as you can get it. For starters they typically play a slightly different frequency range. Surface area of the single 12 is still slightly higher by the way. This is more of a preference thing than anything.

2. I would be amazed if you could hear the difference with the THD you are talking about on subs.

3. As for excursion/distortion. First off, assuming that in your example you had subs appropriatley matched to amplifiers, the distortion is not a one sub vs 2 sub situation. If you supplied a single 400 watt sub with 400 watts and two of the exact same subs but rated for only 200 watts supplied with 200 watts you would have roughly the same distortion because all would be playing at close to their max recommended rms rating. And giving a sub that is rated for 400 watts rms 200 watts doesn't necessarily lower distortion either because it's all about the control of the cone and not enough power may bring on distortion from turning it up to compensate. Plus, why waste money on a sub you aren't maximizing the potential of/

4. 5.1 can indeed have multiple subs...the .1 just refers to the sub channel (Low frequeny effects for home theater) and not the total number of woofers.

5. The dB rating you gave for each speaker is the efficiency of the sub with 1 watt measure at 1 meter and not the level they test to...not sure if you misunderstood that?

I would steer you towards a single 12 versus 2 8's. I think it will be more versatile and give you more of a 'subwoofer' performance than the 8's, which always sound little more like low mid bass to me. Either way you go, since you haven't bought equipment yet, try to maximize your amp by getting one that is 2 ohm stable and if you go the single 12 route get one with dual voicecoils and wire it so you can run your amp to it's full potential. Or go big and and get two 12's.

Oh and for one more variable, my favorite setup is two 10's.:eek:
 

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Discussion Starter #12 (Edited)
I think you are just trying to understand the theory behind your questions and not really thinking of doing it, correct? If you are actually considering running two 4ohm subs on a 2-channel amp then you should really get a 2ohm stable amp and run the two subs in parrallel and bridge the amp.
Actually i have the equipment
two sony XM-7557 (each with 1x220w rms at 4 ohms)
One XM-7527 (bridged 1x300w rms at 4 ohms)
One XM-7547
Magnat - Transforce Reference 130BP (400W rms, 12", 4 ohm, 93dB)

Was trying to understand and detemine which setup to use.
 

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For a given spl, 2 drivers use less Xmax than 1 driver .....Less Xmax = Less Distortion.
Running more than 1 sub the power will be shared resulting in Less power compression.
2 motors versus 1 motor the 2 motors are going to run cooler than the single motor thats a good thing.
The output of 2 subs versus 1 will be more linear since each sub will be working well below its limit.
THIS IS ASSUMING THE SAME SUBS AND THE SAME AMPLIFICATION OF 2 SUBS VERSUS 1
Distortion is a one sub versus two sub thing.
 

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For a given spl, 2 drivers use less Xmax than 1 driver .....Less Xmax = Less Distortion.
Running more than 1 sub the power will be shared resulting in Less power compression.
2 motors versus 1 motor the 2 motors are going to run cooler than the single motor thats a good thing.
The output of 2 subs versus 1 will be more linear since each sub will be working well below its limit.
THIS IS ASSUMING THE SAME SUBS AND THE SAME AMPLIFICATION OF 2 SUBS VERSUS 1
Distortion is a one sub versus two sub thing.
For the argument you are making you are correct to assume less distortion with 2 subs but ONLY IF you are only going to drive both systems to the same SPL....which is not what most people would do. If someone has a 1 sub system they are goin to maximize SPL output up to the point that it still sounds good. If they have a 2 sub system they are also going to maximize SPL up to the point that it still sounds good...it will just be a higher SPL. In practice, both setups are goint to have approximately the same distortion levels. We aren't talking about overdriving the one sub setup and driving the 2 sub setup the perfect amount.

And why would you ever want to give a sub recommended for 400 watt rms half it's capable power? It's like buying a Ferrari and idiling it around your neighborhood because you don't want the enginge to get hot. Equipment is typicaly underated anyway so if you are close to the manufactuers suggested power input you aren't goign to have issues. Again, your system is only as good as it's weakest link, and underpowering a sub, which people always push anyway, is going to bring on amplifier or HU distortion from trying to crank it up to compensate.
 

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Actually i have the equipment
two sony XM-7557 (each with 1x220w rms at 4 ohms)
One XM-7527 (bridged 1x300w rms at 4 ohms)
One XM-7547
Magnat - Transforce Reference 130BP (400W rms, 12", 4 ohm, 93dB)

Was trying to understand and detemine which setup to use.
If you only have one 12 and aren't going to get another, it looks like, with the equipment you have listed, you should just hook it up to the 7527 and be done with it. I'm sure it will sound great.

Now you if are thinking about getting another 12 and using both the 7557's to drive them it's another variable added...instead of a 2 channel amp you have two discrete amps...that may or may not be closely matched...driving two different subs. It will definitely work but the outputs of the amps will have to balanced as much as possible so one sub isn't significantly louder than the other.
 

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For the argument you are making you are correct to assume less distortion with 2 subs but ONLY IF you are only going to drive both systems to the same SPL....which is not what most people would do. If someone has a 1 sub system they are goin to maximize SPL output up to the point that it still sounds good. If they have a 2 sub system they are also going to maximize SPL up to the point that it still sounds good...it will just be a higher SPL. In practice, both setups are goint to have approximately the same distortion levels. We aren't talking about overdriving the one sub setup and driving the 2 sub setup the perfect amount.

And why would you ever want to give a sub recommended for 400 watt rms half it's capable power? It's like buying a Ferrari and idiling it around your neighborhood because you don't want the enginge to get hot. Equipment is typicaly underated anyway so if you are close to the manufactuers suggested power input you aren't goign to have issues. Again, your system is only as good as it's weakest link, and underpowering a sub, which people always push anyway, is going to bring on amplifier or HU distortion from trying to crank it up to compensate.
I never said give a sub recommended for 400 watts rms half its capable power. What if half the recommended power for the sub is all you have? I agree with some things you said and some I do not. We are clearly seeing a different scenario.....I am not saying drive your speakers at half load for thermal reasons. I am saying that is a benefit or a bonus or a plus of doing so.
 

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I never said give a sub recommended for 400 watts rms half its capable power. What if half the recommended power for the sub is all you have? I agree with some things you said and some I do not. We are clearly seeing a different scenario.....I am not saying drive your speakers at half load for thermal reasons. I am saying that is a benefit or a bonus or a plus of doing so.
There are so many variables in the OP....many of which don't matter much, if at all, and others that weren't even discussed....that an apples to apples discussion is tough, at best. It's hard to talk about theory with out specific examples and then to compare that theory to actual world practice. According to NASA the bumble bee should not be able to fly but it gets along just fine.

I think we can both agree though, distortion is most often a symptom of improper setup and/or pushing the system beyond its capabilities to eeke out just a little more volume and rarely just about the performance of specific components in ideal test conditions.
 
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