My sub project is huge... should I build a riser for my sofa instead? (1 Viewer)

[Javier_Huerta]

Here is what I've been thinking.

I need approximately 900 liters' worth of space for my 4-driver subwoofer. Initially, I planned to build it as a base for my center channel, in 4 220L boxes.

Now I realize 900 liters is the approximate size of a *huge* refrigerator. It's just *too* big.

I don't want to lose low frequency response, though. An IB is out of the question, too (the drivers drop off too fast on an IB enclosure).

How about a sofa riser, then? If I built it, I could have a 900l enclosure with zero problems whatsoever. The questions I have, though, are...

1) Should the drivers be firing frontwards, backwards, sideways, or straight up to the sofa?

2) What about the ports?

3) How would sound quality be affected?

4) Do you think I could have any other options for building such a huge sub enclosure?

Thank you very much for your help!

Javier.

 

[Jassen M. West]

i have nothing more to say than i hope this idea works and i want to see pics if it gets done. who needs bass shakers....


jay

 

[Cam S]

I would think that with the weight of the sofa on the sub box your going to have a VERY dead box. I don't see why it wouldn't work, other than not being the perfect place to put a sub, but with 4 subs (tempests I'm assuming) the location won't be too important with that much air being moved. Good luck with the project and keep us informed!

 

[RayJK]

I've seen this done with up firing subs but that was an 18" driver. If possible fire 2 drivers out of either side and put the ports in the rear. This will keep feet from kicking the drivers if they were front mounted and also cancel some of the forces involved because the drivers are on opposite sides of the enclosure.

I converted a closet into a giant sub @ 2531 L so 900 L is just a small box.

 

[Owen Bartley]

I would probably try to put 2 drivers firing up into the couch (assuming dust wouldn't be a huge problem - it might) and then one on each side. Put the ports facing forward, and it should be pretty sweet! This is a project I would definetely do myself if I had a dedicated room (or one that I could get away with putting a riser in) so I'm really interested in how you do it... keep us updated!

 

[Dean Cooper]

I would probably do something like this:

 

[Javier_Huerta]

Thank you all for your opinions!!! They have been very helpful.

I like your idea, Dean. REALLY! The subs would be completely protected against accidental bumping or the like, which is what I've been worrying about. Wouldn't it be even better to have the drivers firing *upwards*? I guess you'd feel the bass waves coming to your head... and considering there will be around 1 meter from the subs to your ears, I guess I'll be getting *massive* SPL amounts with low power requirements.

I won't be using Tempests, though. I'll be using 4 C-V 12" drivers. The whole point of the project is, being in Mexico I can't buy those drivers (I already have one, and will be building a sub for my music system).

The thing is, how well would bass integrate with the rest of the speakers' response???? They would be pretty far away from them.

Another thing. I think I'd like to separate the riser into 4 individual boxes, each one with its own driver. That way, I wouldn't have to worry too much about extremely long ports, resonance and high mach ratings.

So far, I've liked all of your suggestions. I've been thinking lots of options since yesterday thanks to you!

Javier.

 

[Cam S]

I wouldn't have to worry too much about extremely long ports, resonance and high mach ratings.

This would be more of a factor in individual box's. One large box might be a little hard to build, and may be awkward when you wanna move it, so individual box's might be the way to go. The box's could be a little big for the drivers, but you'll have to figure that out and let us know the dimensions. BTW, do you a link for the specs on these 12" drivers?

 

[ThomasW]

An IB is out of the question, too (the drivers drop off too fast on an IB enclosure).

Naa that's not true. All 'boxes' roll off at basically the same rate. But with a ported design you get free boost from the box tuning frequency.

You'll definitely 'hear/locate' a platform sub as a pressure source separate from the mains, so use a VERY low XO point.

Phase is going to be an issue with the drivers mounted behind your head. So be sure to use a XO that has a variable phase control. Even then there maybe integration problems.

Not sure over the long run that I'd want a subwoofer functioning as 'headphones'

 

[Cam S]

Javier, is it possible for you to do an IB sub? I would seriously consider going with that. Thomas is the man to talk to about IB subs!

 

[JimRHIT]

Hey Thomas,

Would the Paradigm X-30 be a good candidate for this application for Javier?

I am kind of thinking about the same idea as Javier for extreme lows. IE - XO @ ~ 50Hz to extend to the mid-teens.

I plan on using Rocket 750's ... which have pretty good extension to around that range.

Thanks in adavance

 

[Javier_Huerta]

Cam, yeah, it's entirely possible for me to build an IB. Problem is, I think the roll-off rate would mean I'd need at least 8 dB of equalization to achieve flat frequency response.

Thomas, I know what you mean. I don't want a Sennheiser Surrounder kind of subwoofer (does anyone except me have one, anyway??? ). Do you think these subs would make a good IB driver?

Qes=0.386
Qms=13.362
Qts=0.385
Fs=22Hz
Vas=198.56l
SPL=89.31dB
Xmax=+-17mm

As I said, I have four of them. Since I have the PE300-794, I also have a variable phase knob and the possibility of adding some EQ to the mix.

Thanks for all your help!

Javier.

 

[Dave Milne]

Javier
Check out this platform sub
It's about 600 liters. The port is front-firing. Works very well. The couch on top prevents damage from fingers and feet. The solid walnut trim helps protect the corner --otherwise the carpet seam would be very vulnerable.

Only drawback is it took three people to move it from the shop. It's 1" MDF and about 250lb.

 

[StephenP]

If it were me, I would put the subs firing up into the couch, with ports on the front. Subs on the front or sides would either make your couch much to tall, or require a more complicated box with strange bracing needs. You must have a large room to think you need 4 subs. Have you considered 2 15's? Or even one of those new Adire Tumults would produce tremendous pressure. Good luck with your project and keep us posted!

 

[ThomasW]

Jim

Yes the Paradigm is a good low cost active XO.

Javier

An IB really isn't going to need any more or less EQ than any other sub. A lot of what happens depends on room gain.

Those appear to be the same T/S parameter you posted on the 'cult' forum and yes they look fine, if they're accurate.

Platfrom subs are ok if they are the only available option. Most that use larger diameter drivers are IMO, not deep enough for the rear wave of the driver to avoid bouncing back towards the cone.....

 

[Todd Shore]

I can just imagine my cat curling up in that nice cuddly driver and the surprise he would be in for when the movie starts.

I laughed myself silly for a couple of minutes on that one.

 

[Gary Griffiths]

I have a sofa sitting on a riser fitted with a pair of Tempest drivers. The size of the riser is approximately 7'x4'x1.25', roughly 900 litres. It is split into two sealed chambers. As you sit on the sofa the twin tempests are in the right hand half of the riser, I haven't finished the left hand side as I got sidetracked with an IB and sold my other two Tempests thinking I wouldn't need them. I've now abandoned the IB because of structural issues and have reverted back to finishing the riser.

With only the right hand half working (450L) using a Marchand Electronics BASSIS to boost the low end, a BFD to even out the peaks and an x30 for the low-pass filter I can tell you that I'm very pleased with the result. So much so that I'm now selling my two Paradigm Servo 15's as this sub now goes just as deep with a much better overall sound quality.

There is just a couple of slight drawbacks, I was keen to get the project back on the road again and attached the baffle without finishing the internal bracing. The effect is not pleasant. The vibration through the Sofa made me feel physically sick when testing the sub with the DTS soundtrack of Titan AE. Also, I can tell that the sub is off to my right which sounds a little odd, but that wont be a problem when I get the other half of the riser sorted out.

Hope that helps.

 

[Brian J Dupuis]

I've now abandoned the IB because of structural issues

Care to comment on the structural issues? I'm still considering an IB someday, so this has me curious. Thanks.

 

[Javier_Huerta]

Now I'm actually considering an IB for my sub! The trouble of building a riser / huge box and then fitting it esthetically in the room is proving to be too much.

I'm drawing a couple of sketches of how an IB would look. It seems feasible now that I think about it. I'll finish up the drawings and post them here.

Now, I think that in order for an IB to work the best, I should try and make the room have reinforcement over its length on the 20-40 Hz range. This way, I may not need EQ. Am I right? If so, I can start working!

 

[Gary Griffiths]

Care to comment on the structural issues? I'm still considering an IB someday, so this has me curious. Thanks.

I couldn't stop the ceiling resonating which was causing cracks around the edges. Tried re-locating the sub but that didn't solve the problem. I'm actually happier with the sound now that the subs are in the riser, I seem to be more comfortable with the sound coming from below head height rather than above.