adding a 4th sub, do chamber specs need to match other 3 to sound good?

[RSDXzec 10+ year member]

Considering adding a 4th subwoofer of the same kind as my other 3. I have 3 in the boot each in an approx 1.8cf chamber tuned to 32hz so I have no remaining boot space. My idea is to make sort of an arm rest for the back seats which will actually be a sub box. My question is when adding the 4th sub if the box size/tuning needs to be the same as the others to sound good with the others (same freq response) or if i can take advantage of having more space available there and make a larger box to sound better (more efficiency/hits lower than other 3). The 4th sub will be on its own amplifer, the other 3 are on a single amp as well.

Cheers.

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[Jroo 10+ year member]

not quite sure what you are asking? Are you basically trying to add another sub on the inside of the car and keep the 3 in the trunk? I would focus on making the 3 in the trunk sound best before adding another sub with its own amp and such. What are you trying to gain by adding the 4th sub?

 

[RSDXzec 10+ year member]

not quite sure what you are asking? Are you basically trying to add another sub on the inside of the car and keep the 3 in the trunk? I would focus on making the 3 in the trunk sound best before adding another sub with its own amp and such. What are you trying to gain by adding the 4th sub?

the 3 in the trunk are already as good as they're gonna get, got no boot space left and I designed the custom box for them.

and an extra sub would add more bass, figured that bit was self explanatory

I'd like to know if all 4 subs need the same chamber size/tuning to sound good together.

 

[Jroo 10+ year member]

I think what you are trying to do will cause you more issues. You start getting into phase and delay issues by having a single woofer in car. They only time I have seen anything close to this is when someone has the subs playing different frequency. One example is and set of 8's under in cabin, on rear deck, or under the seat playing 100 to 50 and the subs in trunk playing 50 down. I sounds like you are just trying to stick another sub somewhere playing all the same as what is in the trunk.

 

[hispls 5,000+ posts]

More than likely this will give you little or no gain for a big investment.

If your goal is more output there has to be a better way to get there for less money.

 

[Better-Action 10+ year member]

what kind of subs do you have and what size? and what amp is powering them. and what car are they in?

 

[Lowflyin 10+ year member]

No,no,no. You need each sub to be giving the amp the same impedance so they all receive the same power. The must all also be in the same sized box tuned to the same frequency. and don't mix and match amps for the same speakers.........

 

[Vincer77 10+ year member]

This brings up an interesting question. Does it make sense to have several subs in different boxes tuned to different frequencies to get a fuller sound spectrum? From the comment above, if you do this, they would need to be run on separate amps.

 

[Buck 5,000+ posts]

It doesn't work like that. If I was to have 4 subs I would want them all in the same box tuned to the same frequency with preferably one large port.

 

[Chriszle 10+ year member]

It may be louder on certain frequencies, but will also cause a lot of cancellation at others. Will more than likely sound horrible.

 

[RSDXzec 10+ year member]

No,no,no. You need each sub to be giving the amp the same impedance so they all receive the same power. The must all also be in the same sized box tuned to the same frequency. and don't mix and match amps for the same speakers.........

The idea was to run it on a separate amp so differing impedance wouldn't be an issue, my concern was causing cancellation at certain frequencies if the subs responded differently as one would be in a different box to the others

This brings up an interesting question. Does it make sense to have several subs in different boxes tuned to different frequencies to get a fuller sound spectrum? From the comment above, if you do this, they would need to be run on separate amps.

No, they will be covering the same frequencies and were going to be run on a different amp if the box was going to be another size, but at this point I believe I'm just going to go with the same size box/tuning freq to make sure all the subs respond the same. Then later on if I want I can run them all on the same amp.

what kind of subs do you have and what size? and what amp is powering them. and what car are they in?

old *** hatchback, 3 12" subs rated at 350WRMS, amp rated at 1500WRMS so it's capable of taking on 4 of them.

I'm not going over that power because the cars electrical is being stretched to it's limits, recently had the alternator rebuilt/upgraded and I'm buying an AGM battery soon.

It may be louder on certain frequencies, but will also cause a lot of cancellation at others. Will more than likely sound horrible.

is that with the 4th sub in a different size chamber? or all the same?

Cheers.

 

[Better-Action 10+ year member]

What are the brands and models of the amp and subs?

 

[RSDXzec 10+ year member]

What are the brands and models of the amp and subs?

does it make a difference? I'm just asking in general.

on another note does the box have to be exactly the same shape? or just size and tuning are enough?

as i understand it a different shape would only alter the phase a bit.

 

[RicksI30 10+ year member]

does it make a difference? I'm just asking in general.

To be blunt, do not do it because it is a waste of time and you will not benefit from it.

 

[Better-Action 10+ year member]

does it make a difference? I'm just asking in general.

on another note does the box have to be exactly the same shape? or just size and tuning are enough?

as i understand it a different shape would only alter the phase a bit.

Yea it does kinda make a difference. If its poor quality equipment you could get much louder with fewer drivers. You could save space and be louder.... in general. But its your setup so yea, whatever you want.

If the tuning and airspace is the same it should be OK. The only thing I can think of would be that because of the different enclosure you may get different box rise on that one. Which I don't know if it would be significant enough to matter, but I'm thinking probably not.

Edit - I forgot it would be on a different amp. If your set on having 4 my recommendation would be to rebuild an enclosure for all 4, and get a amp that can power all 4. Seperate boxes and different amps and different boxes is not the way it should be done. 1 box, 1 amp and it should work out OK.

 

[momax_powers 10+ year member]

sell the subs and box and get a pair of 15s

 

[Fishpoke 10+ year member]

Due to phase cancellations you will see no benefit, but a reduction in output.

 

[RSDXzec 10+ year member]

Yea it does kinda make a difference. If its poor quality equipment you could get much louder with fewer drivers. You could save space and be louder.... in general. But its your setup so yea, whatever you want.
If the tuning and airspace is the same it should be OK. The only thing I can think of would be that because of the different enclosure you may get different box rise on that one. Which I don't know if it would be significant enough to matter, but I'm thinking probably not.

Edit - I forgot it would be on a different amp. If your set on having 4 my recommendation would be to rebuild an enclosure for all 4, and get a amp that can power all 4. Seperate boxes and different amps and different boxes is not the way it should be done. 1 box, 1 amp and it should work out OK.

yeah it's pretty cheap equipment, subs were second hand bought separately so I'm iffy about having them together in the same chamber, also I don't have enough room to fit all 4 in the same enclosure... 3 was already a stretch, only got 1.7cf for each sub after displacements and ports as small as I could get them to be able to handle 350w without port noise according to winisd.

and I'm hoping to be able to put this sub on the same amp if i need to, the amp can handle it but I'd prefer to have it on another atm otherwise i need to buy thicker wires. Hopefully a different shape box with the same volume and tuning doesn't alter the box rise enough to matter.

Due to phase cancellations you will see no benefit, but a reduction in output.

you really think it's definitely gonna be between 90 and 270 degrees out of phase?

What recommendation would you give to maintain the phase within 90 degrees of the other 3 subs... preferably in phase if possible.

 

[Better-Action 10+ year member]

1.7 for each 12? Honestly you will probably be louder running only 2 in a proper sized box then 3 being choked. Then add in a 4th on a different amp and enclosure, possible phase issues and receiving a different amount of power. Seems like a big inefficient mess. Keep it simple man. People can hit 150 decibels with a single subwoofer. No need for a mess of a setup that in the end could be outdone for a 10th the effort.

Efficiency is key.

 

[RSDXzec 10+ year member]

1.7 for each 12? Honestly you will probably be louder running only 2 in a proper sized box then 3 being choked. Then add in a 4th on a different amp and enclosure, possible phase issues and receiving a different amount of power. Seems like a big inefficient mess. Keep it simple man. People can hit 150 decibels with a single subwoofer. No need for a mess of a setup that in the end could be outdone for a 10th the effort.
Efficiency is key.

Just double checked and it's 1.85cf each sorry, I used winisd to simulate the response and 3 of them is only 1db louder across about 28-36hz, after 40hz that 3 subs rises to about 4db louder when all subs are at rms power. Most prefab boxes for 12's I think are around 1.5cf so these aren't doing too bad, I designed this box for my car so I could make use of all the boot space I have. Also i'd like to know what you think of having 2 separately bought second hand subwoofers in the same chamber? Is it ok or would they react differently because they've been used in different boxes previously?

Cheers.