Really thin under couch subwoofer

[annunaki]

http://www.parts-express.com/projectshowcase/indexn.cfm?project=Boogieman

Even the boogieman won't quite fit. You'd need to elevate the couch slightly, as it is 5" tall without feet.

No you wouldn't, just modify the design a bit.

 

[annunaki]

With an unsketched design I am getting 3.295ft^3 gross volume. to do a proper slot vent one will need to figure a driver that will work in about 2.5ft^3 net volume and have a mounting depth no more than 4.5".

 

[askene]

So I've been playing around with some other drivers and the SB Acoustics 10" SW26DAC76-4 is looking like the winner so far. The bit that concerns me is the difference in specs from madisound (the only US distributor) and SB Acoustics themselves.

Madisound's "preliminary" specs

SB Acoustics's specs

If the manufacturers specs model much better and don't have "Preliminary Data" in the PDF, so I'm going to assume those are the real ones.

The good part to this is the default winISD model with those specs works perfectly for the space I've got: 2.359 ft^3 and 19.72Hz with f3 of 18Hz

I'm not sure I really believe a low profile driver will go that low....

WinISD pro project
WinISD pro driver specs from SB Acoustics data
WinISD pro driver specs from Madisound

 

[askene]

annunaki, you were pretty much dead on with the size requirements!

I've been having too much fun with sketchup creating something that will fit under there. This is the basic design I'm looking at. The top is the outside, the bottom is the inside volume

I can squeeze ~2.55 cu ft out of there once I take out the bracing, driver, amp and vent volume.

I'm not really sure what the better vent configuration would be though...out the front/back is easier to build but since the back of the box would be 5-8" from the wall would it make the sub too boomy?

I'm not worried about my box/volume calculations, but I've no idea if my sub modeling is anywhere near decent. I just tried to create the flattest curve I could with a few drivers and this is what I've got:

WinISD project
Sketchup project

It'd be awesome if someone could double check my model to see if it looks reasonable before I start hacking apart some MDF.

 

[annunaki]

Sorry, I have been very busy between some extra college courses & work.

Your design is very similar to what I would have done. What driver are you modeling in that volume?

I will run it through as well and see what I come up with.

annunaki, you were pretty much dead on with the size requirements!

I've been having too much fun with sketchup creating something that will fit under there. This is the basic design I'm looking at. The top is the outside, the bottom is the inside volume

I can squeeze ~2.55 cu ft out of there once I take out the bracing, driver, amp and vent volume.

I'm not really sure what the better vent configuration would be though...out the front/back is easier to build but since the back of the box would be 5-8" from the wall would it make the sub too boomy?

I'm not worried about my box/volume calculations, but I've no idea if my sub modeling is anywhere near decent. I just tried to create the flattest curve I could with a few drivers and this is what I've got:

WinISD project
Sketchup project

It'd be awesome if someone could double check my model to see if it looks reasonable before I start hacking apart some MDF.

 

[askene]

No worries, you're already doing me a favor helping out.

I've modeled it with a few different ones:

Earthquake SWS-10 (winISD proj file)
SB Acoustics 10" SW26DAC76-4 (winISD proj file)
JL Audio 10w1v2-4 (winISD proj file)

The Earthquake is by far the most powerful, but their specs are a little suspect and when emailing them they advised using it in a sealed enclosure instead.

The SB Acoustics goes the lowest, but looks horribly inefficient.

I already know you love JL Audio's drivers so no need to go into detail there.

I have no idea what would work better...I'm a novice in looking at a frequency chart and knowing what it will sound like.

 

[annunaki]

There is more to it than just the frequency chart. There is the linearity of the driver design to consider, excursion limits, vent velocity, group delay and others. JL drivers are nice but there are plenty other nice ones out there. They just seem to fit a lot of applications. They are also a completely known entity to me.

I will model the three drivers against each other and see what come up with.

No worries, you're already doing me a favor helping out.

I've modeled it with a few different ones:

Earthquake SWS-10 (winISD proj file)
SB Acoustics 10" SW26DAC76-4 (winISD proj file)
JL Audio 10w1v2-4 (winISD proj file)

The Earthquake is by far the most powerful, but their specs are a little suspect and when emailing them they advised using it in a sealed enclosure instead.

The SB Acoustics goes the lowest, but looks horribly inefficient.

I already know you love JL Audio's drivers so no need to go into detail there.

I have no idea what would work better...I'm a novice in looking at a frequency chart and knowing what it will sound like.

 

[annunaki]

annunaki, you were pretty much dead on with the size requirements!

I've been having too much fun with sketchup creating something that will fit under there. This is the basic design I'm looking at. The top is the outside, the bottom is the inside volume

I can squeeze ~2.55 cu ft out of there once I take out the bracing, driver, amp and vent volume.

I'm not really sure what the better vent configuration would be though...out the front/back is easier to build but since the back of the box would be 5-8" from the wall would it make the sub too boomy?

I'm not worried about my box/volume calculations, but I've no idea if my sub modeling is anywhere near decent. I just tried to create the flattest curve I could with a few drivers and this is what I've got:

WinISD project
Sketchup project

It'd be awesome if someone could double check my model to see if it looks reasonable before I start hacking apart some MDF.

With the earthquake, can you get me the T/S specs you used. not the ones in your WinIsd file either since they do not show the measurement type used for xmax or Sd.

Also, I need the gross volume of the enclosure. You can figure out the bracing displacement but leave everything else out. The vent is too small to adequately accommodate any of those drives without vent noise issues.

Thanks!

 

[askene]

Sure thing.

The Earthquake specs are here: specs

Re=3.76
Fs=28.447
Sd=0.033
BL=22.09
Qms=5.02
Qes=0.51
Qts=0.46
SPL=88.2
Vas=51.479 l
Xmax=28 mm
Pe=200 W

The BL value is surprisingly high. The response from Earthquake about it was "These are the measurements from our technicians"

The interior volume without any bracing or vents is ~3.2 ft^3 (90 L).

After putting the sketch together I realized I was calculating everything for 1W of power...so yeah, I'll have to probably have to double venting cross section and adjust length, etc. For venting...how important is the directionality of them? I mean does out the side, back, top make a significant difference?

Thanks again!

 

[annunaki]

Sure thing.

The Earthquake specs are here: specs

Re=3.76
Fs=28.447
Sd=0.033
BL=22.09
Qms=5.02
Qes=0.51
Qts=0.46
SPL=88.2
Vas=51.479 l
Xmax=28 mm
Pe=200 W

The BL value is surprisingly high. The response from Earthquake about it was "These are the measurements from our technicians"

The interior volume without any bracing or vents is ~3.2 ft^3 (90 L).

After putting the sketch together I realized I was calculating everything for 1W of power...so yeah, I'll have to probably have to double venting cross section and adjust length, etc. For venting...how important is the directionality of them? I mean does out the side, back, top make a significant difference?

Thanks again!

The earthquake looks to be a reasonably good option here. With 200 watts of input power (recommended) it nearly mirrors the 10W1v2 in terms of response, but stays much lower in terms of rated xmax. I do not believe the earthquake to have an extremely linear motor so I would suggest no more than the 200 watts rms.

with 250 watts rms anechoic output is +/-3db from 21.5hz-85hz with around 106db-109db capability. The vent velocity stays below 17m/s with a 4.0" H x 5.5" W vent 39" long tuning to about 23.5hz. Xmax is also well below rated which should keep the driver in the linear range. This vent should accommodate noise free operation up to about 300 watts of rms input power.

This vent will net you about 2.594 ft^3 volume using .02ft^3 for driver displacement and .75" material for the vent pieces.

The earthquake looks to be the best performer based upon simulations that I can see from the three drivers you were considering.

It should perform quite well for your application!!