Do 2 subs play lower than one?

[abefroeman]

If you have 2 identical subs and you turn one off, would the measured extension be lower than if both were running?

Not to answer my own question because I don't know. But I was thinking that if a 15hz tone was played on a single sub that falls off to -3 at 18hz, that the tone would play louder with 2 subs rather than one and would therefore have a lower extension and perhaps a lower F3.

Thoughts?

 

[Matt34]

If you have 2 identical subs and you turn one off, would the measured extension be lower than if both were running?

Not to answer my own question because I don't know. But I was thinking that if a 15hz tone was played on a single sub that falls off to -3 at 18hz, that the tone would play louder with 2 subs rather than one and would therefore have a lower extension and perhaps a lower F3.

Thoughts?

From my understanding....kind of. Yes the tone will be louder but the sub(s) are still going to be limited by enclosure, driver and amp. They are still going to drop off at the same freqency, it will just be at a higher level.

Gawd, that explanation sucks.

 

[MidnightSensi]

If you have 2 identical subs and you turn one off, would the measured extension be lower than if both were running?

Not to answer my own question because I don't know. But I was thinking that if a 15hz tone was played on a single sub that falls off to -3 at 18hz, that the tone would play louder with 2 subs rather than one and would therefore have a lower extension and perhaps a lower F3.

Thoughts?

If the acoustics are okay (meaning, the listening position doesn't have destructive interference between the two subwoofers), than the additional subwoofer will raise the spl by +3dB. With the room pictured in, roughly +5dB (+6dB without factoring room modes, but in practical applications its +5dB). This means that at the same SPL you can lower your cutoff frequency.

Where you might find one subwoofer to measure better than two at some frequency, is if there is destructive interference (the drivers are producing waves that hit eachother at the measuring point out of phase, cancelling one another out). If this is the case, increasing the volume will actually lower the level. To fix this, adjust placement of the subwoofers. EQ will NOT fix this problem.

 

[tcarcio]

I would say the answer is no. I agree the response will be better and the spl will go up but if the two subs your useing are identical then how can it go lower?

 

[TLS Guy]

If you have 2 identical subs and you turn one off, would the measured extension be lower than if both were running?

Not to answer my own question because I don't know. But I was thinking that if a 15hz tone was played on a single sub that falls off to -3 at 18hz, that the tone would play louder with 2 subs rather than one and would therefore have a lower extension and perhaps a lower F3.

Thoughts?

You will be up 3 db at 18 Hz, but you will also be up 3 db at 40 Hz! If the subs are in close proximity it will be up 6 db, at both points. So the curve will not change, you will just need less power for the same spl.

 

[KEW]

I would say the answer is no. I agree the response will be better and the spl will go up but if the two subs your useing are identical then how can it go lower?

All I can think of is that if you EQ it, you would be able to have a lower usable limit.

 

[njedpx3]

If you have 2 identical subs and you turn one off, would the measured extension be lower than if both were running?

Not to answer my own question because I don't know. But I was thinking that if a 15hz tone was played on a single sub that falls off to -3 at 18hz, that the tone would play louder with 2 subs rather than one and would therefore have a lower extension and perhaps a lower F3.

Thoughts?

Frequencies below 100 Hz are non-directional, but overall you will get better imaging with two subs. Two will provide smoother bass response due to modal averaging, but there will be no change in F3 or lower extension, which will remain the same. I know in some subwoofers, the F3 can be lowered 10-20 Hz by blocking some of the ports, example SVS PB12-Plus has three ports, you can block none (20 Hz) , one (15 Hz) or all three (25 hz, higher SPL). However increased port turbulence can literally cause high distortion and negative gain. From the Thiele-Small parameters, the advantage of a vented over sealed box is about equal to a 1/3rd box volume reduction.


Sub- On

Forest Man

 

[MidnightSensi]

The subwoofers don't lower their f3, the system extends its low end response.

You have an extra 3dB of headroom at each point (without factoring in the room, as mentioned earlier), so depending on how steep your cutoff is set (or if you don't use a subsonic cut than how the response tapers off naturally) you gain a significant amount of extension.

What TLS is talking about is if you stack them, because of a mirroring effect you can get 6dB (anechoic) and effectively increase your low end extension even more.

The trade off then becomes do you want to tame room response or gain low end. Generally, taming the room response makes for a bigger difference in a home theater.

 

[TLS Guy]

All I can think of is that if you EQ it, you would be able to have a lower usable limit.

If it is ported you can't Eq it. If they are sealed subs you could get significant extension.

 

[tcarcio]

All I can think of is that if you EQ it, you would be able to have a lower usable limit.

Agreed, But I don't think it would go lower then one sub only.

 

[TLS Guy]

Agreed, But I don't think it would go lower then one sub only.

It would if they were a sealed subs, and you could use the sensitivity gain to increase spl in the last octave by equalization.

 

[djreef]

I believe the OP is looking for a sum is greater than it's parts type explanation. Unfortunately one does not exist for this ap without an EQ boost in the lowest octave.

Like TLS said (crap he beat me to it again).

DJ

 

[fredk]

If it is ported you can't Eq it. If they are sealed subs you could get significant extension.

If you mean that you cannot boost the bottom end of a ported sub to significantly extend it, I would agree, but you most certainly can EQ a ported sub.

 

[TLS Guy]

If you mean that you cannot boost the bottom end of a ported sub to significantly extend it, I would agree, but you most certainly can EQ a ported sub.

Yes, obviously I meant you can not Eq a ported sub to extend the low end response. This was clearly the point of the OP's post. You can not extend the low end because the driver decouples from the box, and all you get is useless distorted cone motion with no useful output, and risk driver damage.

 

[mike c]

re: ported subs

NO. each of the ported subs will play exactly the same low frequencies as two of the same ported subs except less loudly.

re: sealed subs

i think they talked about it up there. YES, but there's a whole lot of BUTs

 

[The acoustic 1]

Yes Yes Yes...2 subs CAN get you better deeper higher SPL at a lower Q if you understand a couple of good insights. First you will not use the same sub...choose 2 different although same type phisically and acoustically speaking. For example use a 10" sub and a 15" sub and you can push each of them harder and more frequency specific in two separate bands. The 15" might be used from 60 down at +Xdb and the 10" from 50-120Hz.

This is a practice used in some of the worlds finest professional sound systems designed and installed in many acclaimed auditoriums. The most ideal situation of all would be to have an independent electronic crossover and be able to set all the parameters of crossover Q, slope and EQ which would require non-powered subs and separate amps. I recommended used Crown Com-Techs (pro amps) as they are a gem most people don't know about and have killer performance and power for the money especially on the used market.

Always have fun and remember rule #1:

" There are no rules to good sound...Make stuff up"

 

[mike c]

Yes Yes Yes...2 subs CAN get you better deeper higher SPL at a lower Q if you understand a couple of good insights. First you will not use the same sub...choose 2 different although same type phisically and acoustically speaking. For example use a 10" sub and a 15" sub and you can push each of them harder and more frequency specific in two separate bands. The 15" might be used from 60 down at +Xdb and the 10" from 50-120Hz.

This is a practice used in some of the worlds finest professional sound systems designed and installed in many acclaimed auditoriums. The most ideal situation of all would be to have an independent electronic crossover and be able to set all the parameters of crossover Q, slope and EQ which would require non-powered subs and separate amps. I recommended used Crown Com-Techs (pro amps) as they are a gem most people don't know about and have killer performance and power for the money especially on the used market.

Always have fun and remember rule #1:

" There are no rules to good sound...Make stuff up"

welcome to audioholics.

just for future reference (in about 1 or 2 posts actually)
please contact the admin if you want to advertise.

do not put it in your signature or your next post.

 

[annunaki]

Yes Yes Yes...2 subs CAN get you better deeper higher SPL at a lower Q if you understand a couple of good insights. First you will not use the same sub...choose 2 different although same type phisically and acoustically speaking. For example use a 10" sub and a 15" sub and you can push each of them harder and more frequency specific in two separate bands. The 15" might be used from 60 down at +Xdb and the 10" from 50-120Hz.

This is a practice used in some of the worlds finest professional sound systems designed and installed in many acclaimed auditoriums. The most ideal situation of all would be to have an independent electronic crossover and be able to set all the parameters of crossover Q, slope and EQ which would require non-powered subs and separate amps. I recommended used Crown Com-Techs (pro amps) as they are a gem most people don't know about and have killer performance and power for the money especially on the used market.

Always have fun and remember rule #1:

" There are no rules to good sound...Make stuff up"

This is a possibility ONLY if one uses a quality crossover system for each of the drivers with independent amplification.


In the situation described, using two identical subs, one cannot actually lower the actual f3 of the system. One could potentially lower the "effective" f3 with proper placement within the room of both subwoofers. Otherwise the system will simply play +3db or more across the sub's anechoic output range.

 

[Guiria]

I asked the same question a while back. See the thread:

Multiple subs increase extension?

I would agree with TLS Guy and mike c. Multiples of the same sub will give you more SPL, but not extension, ceteris paribus.

 

[abefroeman]

Thanks guys.

It looks like the consensus is that there would be more spl with 2 subs, not more extension.

Has anyone measured 2 subs vs one?