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

[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.

 

[Better-Action 10+ year member]

Are they the same model and brand subwoofer?

 

[RSDXzec 10+ year member]

Are they the same model and brand subwoofer?

yeah lol, i'd never mix different subs, they're all soundstream PCW-12"s

if you want to get technical 2 of them are soundstream EG-12X subwoofers but they have all the exact same mechanical values as the PCW-12 so they're just rebranded. I had a thorough look at all the specsheets before buying them to make sure they were the same subwoofer.

 

[Jroo 10+ year member]

I am willing to bet that if you put 2 subs in the optimal/correct enclosure, it will sound better than the 3 you have now. I have personally seen guys go down to a single sub with a great box and sound better and hit harder than a previous bad set up with multiple subs. I would personally go out to one of the several great box designers and get you a nice set of plans for the 2 and then decide.

 

[Better-Action 10+ year member]

You could put them all in the same box even though 2 of em are second hand.

How much port area do you have and what's your tuning?

 

[RSDXzec 10+ year member]

You could put them all in the same box even though 2 of em are second hand.
How much port area do you have and what's your tuning?

nice, actually all of them are second hand, but i assume your statement still stands. I bought the pcw first, then the 2 ex's second.

tuning is at 31.7hz after displacements (I aimed for 32) and my port area is sad lol, it's the bare minimum.

I have the specs written in winisd and from that I have 3 ports 1.57"x11.25" so 53"^2 all up lol

I am willing to bet that if you put 2 subs in the optimal/correct enclosure, it will sound better than the 3 you have now. I have personally seen guys go down to a single sub with a great box and sound better and hit harder than a previous bad set up with multiple subs. I would personally go out to one of the several great box designers and get you a nice set of plans for the 2 and then decide.

I had a lot of time to research and design this box on winisd and spent a fair bit on the box, not gonna bother with a whole other design for 1db... I'd have to see a real improvement and somehow with less sub surface area and cheap gear like mine i doubt it.

 

[Better-Action 10+ year member]

Your port is to small man. And with what those subs are I think your losing out by tuning that low with them.

What kind of car is this in? You may be able to fit all 4 if you don't mind building it in the trunk "I'm assuming you have a trunk" and firing up.

On the other hand. You are running 3 now, and the way your going about it I think you can probably be louder with 2 of them. For that I'm thinking 2 cubes each. 4 cubes net, tuned to 34-37hz with 16 inches of port per cubic foot.

 

[RSDXzec 10+ year member]

Your port is to small man. And with what those subs are I think your losing out by tuning that low with them.
What kind of car is this in? You may be able to fit all 4 if you don't mind building it in the trunk "I'm assuming you have a trunk" and firing up.

On the other hand. You are running 3 now, and the way your going about it I think you can probably be louder with 2 of them. For that I'm thinking 2 cubes each. 4 cubes net, tuned to 34-37hz with 16 inches of port per cubic foot.

Last box I had was tuned to 25hz when I only had one , now it's 32 because I need my subs to be able to reach the 20's. I drive a hatchback, and as it is the boot is completely full. Here are some pics so you can get an idea. And will increased port area really change the loudness? winisd doesn't seem to change the output with varying port area

 

[Better-Action 10+ year member]

Yes more port will get you louder. And looking at the pics I think even those low power subs are being completely choked by the port they have.

One thing to think about. After seeing how you got it in the boot, rebuilding a box for 3 of them, shared chamber, much more port and I think you will get a pretty substantial increase in output. About the low tuning, some subs just aren't built to play down into the 20's very well. If you tuned to 35ish you'd still be able to play down to 30ish which is pretty low. And the higher tuning and the bigger port of the new box you WILL be substantially louder.

 

[RSDXzec 10+ year member]

Yes more port will get you louder. And looking at the pics I think even those low power subs are being completely choked by the port they have.
One thing to think about. After seeing how you got it in the boot, rebuilding a box for 3 of them, shared chamber, much more port and I think you will get a pretty substantial increase in output. About the low tuning, some subs just aren't built to play down into the 20's very well. If you tuned to 35ish you'd still be able to play down to 30ish which is pretty low. And the higher tuning and the bigger port of the new box you WILL be substantially louder.

I just need my subs to play down to 26hz comfortably, I like to get low lol. How would rebuilding this box get me much more volume? I'd be taking out the chamber walls but at the same time I'd have to add in extra bracing which I didn't have to worry about with this design so I'd probably get the same volume... and it would actually be less if I'm using larger ports. What kind of db is a substantial increase to you? near 10db? 3db?... it's gonna be probably near $100 for me to build a new box so I'd have to justify it as a decent increase.

 

[Better-Action 10+ year member]

I can't really say how much it would increase. You would have to do some bracing but not much for 3 low power subwoofers. What are the current dimension on your box? Could you go any wider, taller, or deeper? Having a shared chamber will add some volume, so will having the port on the rear of the box because the port will have more common walls.