Under Couch Subwoofer?

[GO-NAD!]

Can you post a rough sketch up of the under couch framing? Both a side and an overhead profile? Or, get some photos of the couch's underside?

I would like to see what we have there. We need to maximize as much volume as possible. It may require a slightly more complicated build but realize better results.

I think it would be better to get you some photos, I'm not terribly artistic when it comes to sketches. Can you have a look at the rough enclosure sketch I sent? To get even more volume, I could even make it with 3 humps - 1 fitting inside each bay. I just don't know if that would create more turbulance, or if turbulance is an issue anyway. I have a gut feeling that modifying the couch frame to the extent necessary to fit an enclosure of sufficent volume might require significant compromise to the couch's structural integrity.

I'll post those photos later today.

 

[GO-NAD!]

Here are the photos of the couch. Do you understand my concern about the skirt and the possibility of the sound being muffled? I placed the boards against the fabric in order to push the fabric against the frame. You should be able to see the outline of the frame crossmembers. The frame boards are 3" wide and the space behind is hollow. The couch spring support for the cushions sits on top of this frame. The legs are 5 1/2" high, which gives a total height of the space under the couch, of 8 1/2". I would not want any enclosure to be more than 7" high, including feet, in order to account for any sag in the couch when somebody sits down. I don't know any football linebackers, so I don't expect anyone of more than average gravitational pull to sit on it.

I can confirm the 60" width and the depth can actually 26".

I was looking at the JL website yesterday and they have a tutorial which provides a formula for calculating port dimensions. I couldn't figure it out though... Besides, it would probably be much easier to figure out by using WinISD. I haven't had time to play with that program yet, but I will when I get a chance - looks interesting.

If we come to the conclusion that this design is doable, I can cut away the fabric under the couch, so that it doesn't become compressed against the sub enclosure.

 

[annunaki]

Here are the photos of the couch. Do you understand my concern about the skirt and the possibility of the sound being muffled? I placed the boards against the fabric in order to push the fabric against the frame. You should be able to see the outline of the frame crossmembers. The frame boards are 3" wide and the space behind is hollow. The couch spring support for the cushions sits on top of this frame. The legs are 5 1/2" high, which gives a total height of the space under the couch, of 8 1/2". I would not want any enclosure to be more than 7" high, including feet, in order to account for any sag in the couch when somebody sits down. I don't know any football linebackers, so I don't expect anyone of more than average gravitational pull to sit on it.

I can confirm the 60" width and the depth can actually 26".

I was looking at the JL website yesterday and they have a tutorial which provides a formula for calculating port dimensions. I couldn't figure it out though... Besides, it would probably be much easier to figure out by using WinISD. I haven't had time to play with that program yet, but I will when I get a chance - looks interesting.

If we come to the conclusion that this design is doable, I can cut away the fabric under the couch, so that it doesn't become compressed against the sub enclosure.

I highly doubt the sound would be "muffled". I would potentially worry about subwoofer placement however. You will be at the mercy of room response in the couch's location. The helpful thing would be adding a DCX2496 but if there are large dips in response, they may be difficult to correct.

I will see what I can come up with based upon what I am seeing now. Is the couch 60" wide inside the bracing underneath or total width??

I will see what I can come up with.

 

[GO-NAD!]

I highly doubt the sound would be "muffled". I would potentially worry about subwoofer placement however. You will be at the mercy of room response in the couch's location. The helpful thing would be adding a DCX2496 but if there are large dips in response, they may be difficult to correct.

I will see what I can come up with based upon what I am seeing now. Is the couch 60" wide inside the bracing underneath or total width??

I will see what I can come up with.

The 60" measurement is between the 2 outside frame pieces. That's allowing an inch or 2 of space at either end. Hope you understand what I mean.

I'm at the mercy of room response, no matter what type of subwoofer I use. I'm quite restricted when it comes to placement. My present sub is quite close to a corner right now and there's hump that peaks around 40 Hz, then a null that starts right around 50Hz, but it's being masked by the standing wave being generated by the mains.

I'm hoping that the placement under the couch, being further from a corner, will help things a bit.

 

[lsiberian]

http://forums.audioholics.com/forums/showthread.php?t=53991

is a thread already undertaking your plans.

The biggest issue is sub depth. most drivers don't fit under the couch while in a box.

 

[GO-NAD!]

http://forums.audioholics.com/forums/showthread.php?t=53991

is a thread already undertaking your plans.

The biggest issue is sub depth. most drivers don't fit under the couch while in a box.

I saw that thread and mentioned the Boogieman when I started this one, but during the discussion, it's morphed into something a bit different than that.

 

[annunaki]

The 60" measurement is between the 2 outside frame pieces. That's allowing an inch or 2 of space at either end. Hope you understand what I mean.

I'm at the mercy of room response, no matter what type of subwoofer I use. I'm quite restricted when it comes to placement. My present sub is quite close to a corner right now and there's hump that peaks around 40 Hz, then a null that starts right around 50Hz, but it's being masked by the standing wave being generated by the mains.

I'm hoping that the placement under the couch, being further from a corner, will help things a bit.

One more thing before I get started on this. The openings between the braces are 20" correct? and the braces are 3" wide"? This would put the total width of the couch at 69"?

Or should it be 17" wide openings with 3" wide braces yielding a total of 60" in width?

The height from floor to the bottom of the bracing is 5.5"? You were looking to do 1.5" feet on the bottom of the enclosure as well, correct?

Sorry for all the questions, just planning to do it right the first time.

 

[GO-NAD!]

One more thing before I get started on this. The openings between the braces are 20" correct? and the braces are 3" wide"? This would put the total width of the couch at 69"?

Or should it be 17" wide openings with 3" wide braces yielding a total of 60" in width?

I'll attempt draw up a sketch later today, that will clearly (I hope) illustrate the maximum dimensions you'll have to play with. I should've realized that a photo and some poorly explained dimensions would not suffice. Mea Culpa.

The height from floor to the bottom of the bracing is 5.5"?

That is correct.

You were looking to do 1.5" feet on the bottom of the enclosure as well, correct?

The 1.5" feet is just a guess on my part. Is that enough "breathing room" for a down-firing driver? If it isn't, the enclosure height would have to be reduced accordingly. If the driver doesn't require that much space, then of course, the enclosure can be taller.

Sorry for all the questions, just planning to do it right the first time.

Absolutely no apologies needed! You're doing a favour for a person you've never met. I can't express how much I appreciate that!

 

[GO-NAD!]

I figured the best thing to do, was to come up with a sketch that would hopefully illustrate it better than I could in words. The dimensions I previously gave you for an enclosure were quite conservative, in order to ensure that it would fit in the space. The triangles in the corner of the couch frame are the blocks to which the feet are fastened. The 2 lumps in the middle section are just parts of the frame, whose purpose, I cannot tell you.

I drew the enclosure's depth and width so narrow, in order to clear those obstacles. After drawing it, I'm wondering if we might get more total volume by not trying to fit a raised section in all three bays of the frame. I'll draw up another sketch, but this time, I'll only have 1 raised section to accomodate the driver. The rest, I will leave at 3 1/2" high. But, I'll make it deeper and wider. Then I'll do the math and see which design would give more volume.

Thanks for all your assistance, Annunaki. Most appreciated.

 

[GO-NAD!]

Here's the other idea. I'll do some math and see which is bigger....

 

[annunaki]

Here's the other idea. I'll do some math and see which is bigger....

Here is what I am coming up with so far.

JL Audio 10W1v2-4 vented tuned to 22hz. Net enclosure volume around 2.4ft^3 after vent displacement. A rectangle vent 4" high by 5.0" wide & 42.5" long would work well here. The total height of the enclosure with feet will be 7" in the cavity areas.

Overall dimensions would be 60.5" w x 22.5" d x 6.5" h (less the feet).

I have gone for an upward firing driver though to maximize volume. The feet would only be .5" high in this case.

This will give an anechoic f3 of 22.6hz at 105db. In room results will be stronger of course.

I would suggest an infrasonic filter (2nd order or higher) beginning at 20hz.

Let me know if you have any questions.


I have attached a brief sketch-up I did of the enclosure below:

 

[GO-NAD!]

Net enclosure volume around 2.4ft^3 after vent displacement.

I assume there is no other bracing accounted for in this displacement? Should I add some? If so, would the vent tuning need to be revised?

I have gone for an upward firing driver though to maximize volume. The feet would only be .5" high in this case.

I never thought of that, as I'd never seen one. So, firing up into the bottom of the couch isn't going to muffle the sound? Are the operating frequencies too low to be attenuated by the couch stuffing?

This will give an anechoic f3 of 22.6hz at 105db. In room results will be stronger of course.

That's quite low! Deeper than I was expecting and will certainly be adequate for music. I'd be happy with that for a HT!

I would suggest an infrasonic filter (2nd order or higher) beginning at 20hz.

I assume this would be set throught the DCX? I'll probably be seeking some direction in setting up the DCX when I get it...

I will post another sketch to illustrate a couple more questions

Thanks again!

 

[GO-NAD!]

OK, here is a sketch with a few questions included. Now I must apologize for all the questions!

 

[annunaki]

I assume there is no other bracing accounted for in this displacement? Should I add some? If so, would the vent tuning need to be revised?



I never thought of that, as I'd never seen one. So, firing up into the bottom of the couch isn't going to muffle the sound? Are the operating frequencies too low to be attenuated by the couch stuffing?



That's quite low! Deeper than I was expecting and will certainly be adequate for music. I'd be happy with that for a HT!



I assume this would be set throught the DCX? I'll probably be seeking some direction in setting up the DCX when I get it...

I will post another sketch to illustrate a couple more questions

Thanks again!

I can help with the DCX, and yes, you would set it there.

I accounted for about .2ft^3 for bracing, which may be a tad low, but if you do window bracing like I did in the in-wall sub you should be able to hit right near that.

Woofer displacement was figured in as well.

firing into the couch should not cause much if any issue. There is plenty of room for air to move from underneath (the couch), as well as the vent moving plenty of air.

Is this how the port should look?

Yes. However, if you use 3/4" mdf, there will only be 4" of height. The width will be 5"

The width questions

All of the gaps you pointed out need to maintain the vent width of 5". Remember that vent length is figured down the center line of the vent. So you will need two pieces of mdf the height of the section internally (in this case 4"). One at 16" x 4" and one at 15.75" x 4"

 

[GO-NAD!]

I accounted for about .2ft^3 for bracing, which may be a tad low, but if you do window bracing like I did in the in-wall sub you should be able to hit right near that.

Got it!

if you use 3/4" mdf, there will only be 4" of height.

I don't got it!

I must be not getting something here - your sketch gave an overall height of 6.5". So, if I'm using 3/4" MDF, the internal height should be 5.0", shouldn't it? That's why, when I sketched the port as I understood it, I ended up with a 1/2" section above and below the port. I thought that was odd...

Could you clarify that for me. I didn't think my math was that bad - but maybe it is.

I can help with the DCX, and yes, you would set it there.

Excellent! Thanks!

So you will need two pieces of mdf the height of the section internally (in this case 4"). One at 16" x 4" and one at 15.75" x 4"

Now my head hurts...

Using 3/4" MDF, and with an overall depth of 22.5", I would subtract 1.5" for the 2 sides, then subtract another 5" for the port width. That would give me 16" for both pieces for the vent path.

Could you explain that for me? Sorry for being such a pain...

 

[annunaki]

You are right my bad!!

It is 5". Simply swap the vent dimensions. 5" x 4" wide. Everything else will remain static. The height would be 5" on the 16" & 15.75" vent pieces.

 

[GO-NAD!]

You are right my bad!!

It is 5". Simply swap the vent dimensions. 5" x 4" wide. Everything else will remain static. The height would be 5" on the 16" & 15.75" vent pieces.

Whew! I thought I was losing my mind! Thanks for all you help and patience! I have a few months before I start this, because we are getting our hardwood floors refinished in November. That means packing up and moving out of the house, because the whole main floor is hardwood. I'll be sooooo glad when that is done!

I also have to build a stereo component stand this fall. They're all stacked on a small table now, which pains me to look at. It won't be a quick build, as I'm using pine from a tree that used to be in my back yard - so I have to plane and joint it all first.

In the meantime, I'm going to keep my eyes open for any deals on the pieces I need. By the way, would you suggest a BASH 300 or 500 for amplification? I would mount it to the back of the component stand, so it would be out of sight.

Thanks again. I'll post photos of the subwoofer when I get it underway.

 

[annunaki]

I double checked the volume, and you will have about .4ft^3 to use for bracing and woofer displacement.

This is a fair amount of volume to use for the application.

The second vent piece you can shorten by 3.5" to 12.25".

 

[GO-NAD!]

I double checked the volume, and you will have about .4ft^3 to use for bracing and woofer displacement.

This is a fair amount of volume to use for the application.

The second vent piece you can shorten by 3.5" to 12.25".

Gotcha! I was confused, at first, about the different vent piece lengths, but then I subtracted the individual lengths from the original overall length of 42.5" and then I understood where you got the dimensions.

Thanks.

 

[GO-NAD!]

OK - last question! I see that the 10W1V2 comes in 4 and 8 ohm versions. Which should I get? Or does it matter? Does it come down to the amplifier I choose, i.e. 4 ohm = BASH 500 or 8 ohm = BASH 300?