Furniture doubling up as Subwoofer?

[anm]

Hi,
I am a newbie in DIY. Actually I mean a newbie who is still at the thought level than actually doing something. I am currently reading before asking specific questions on speaker params etc.
Has anyone thought about (and maybe rejected) putting subwoofer into large furniture like couch, sofa, shoe rack, a storage cabinet, av rack etc? Volume of air available
Two issues I can see upfront

- rattling
- air inside the furniture like shoe rack would not be sealed perfectly.

If I want to put downfiring sub inside my 3 seater sofa, how much above the ground should it be at least? Thoughts on downfiring active driver with a downfiring passive radiator?

regards

[rcavictim]

The chances of getting a high quality speaker when modifying a piece of furniture to form a dual function system will be a challenge and is likely to be a less than optimum speaker. If you want to get bass while sitting on your couch have you looked into installing tactile transducers underneath on the wooden frame rails? These create powerful vibrations in whatever they are screwed or bolted to. Basically a motor from a large woofer with no cone. Look up Aura bass shakers as one product available. Parts Express in the USA sells them.

These are an interesting addition to a home theater setup since much of the low frequency energy and rumble in explosions and other sound effects should be felt while the normal speaker system allows the higher harmonic content to be heard.

[454Casull]

Could be done, but the acoustic delay should be compensated for.

[MaVo]

You would still need to build an enclosure, which you integrate into the furniture, since a sub without a box wont do much sound. Seems difficult, but theoretically no problem.

[GM]

Not necessarily, just like with any cab alignment you choose the driver to suit, so for a sofa or similar highly damped/lossy cab a low Fs, high Qts OB/IB driver can be made to work well with a bit of EQ.

WRT proper phasing, of course having an adjustable phase control on the sub amp is preferable, but I've found that most of the time wiring a sub in phase with the mains offsets it enough since normally it needs to be reverse phase wired when located around/at the same plane as the mains.

WRT down-firing spacing, it's a bit counter-intuitive in that the larger the 'baffle's' perimeter the less the gap required to push its bandpass tuning well above the sub's desired pass-band, so a large sofa such as my three wide with barely enough room to slide a dust mop under is acoustically large enough even if partially blocked off.

For storage units, etc., good speaker building design/construction applies, so factoring in pi space loading and significant bracing space losses usually applies and of course there's the 'rattle' factor to consider if other than a bookcase loaded with only massive/lossy books, mags, vinyl albums or similar.

Anyway, just some thoughts to ponder.

GM

[HK26147]

See AudioXpress 6/06: The Table Tuba
I have not built one but have heard good reports based upon this design. It is a folded horn built as a coffee table.
Vibration is not a problem reportedly, with appropriate bracing.
It occupies 8 cu. ft. - 15.75" H x 29.75" W x 29.75" D.
To me, that seems large as a coffee table, and many times coffee table are placed away from walls. To benefit from boundary loading any sub would be better placed near a wall or corner.
Others have reworked the horn folds into the base of an entertainment center.
Also I have read of individuals who placed horn subs in adjacent utility spaces. The horn mouth played through a opening in the wall, covered by a vent.

[planet10]

Here is a sketch i did of a dual-push-push (push-push to reduce box vibration) subwoofer/table.

All sorts of variations on this concept are possible... i probably would have built one but i couldn't figure out how to get cabling to it innocuously.

dave

[HK26147]

Interesting,
Just at the idea stage, or do you have dimensions?
And drivers in mind?
Since you have to have an access panel for the drivers.. is there a problem with using it?
Or coming up from below?

[planet10]

Originally posted by HK26147
Just at the idea stage, or do you have dimensions?
And drivers in mind?
Since you have to have an access panel for the drivers.. is there a problem with using it?
Or coming up from below?

Just a concept at this point... I have contemplated extremis & SDX7, but if you wanted it to be a true subwoofer, you'd need to move up to a larger driver that goes lower and can move more air.

Access to the drivers and construcability is a problem that would have to be considered. In this respect even trickier are the ones that are push-pull-push-push isobarik. Probably have to treat the multitude of drivers as a removable plug-in unit.

If i build one it will probably look more like this... the floating table top would need to be removable for driver module assembly.

dave

[anm]

Sorry for being away for such a long time. I thought no one replied as I didn't get any mail notifications.
I am just considering getting into DIY, and given that my rooms are not large enough, using furniture crossed my mind. I think I should take some pictures of the furniture and room and post. I am not looking for couch shakers, but subwoofers with decent response.
I am trying to find out drivers available locally (New Delhi) - hope I will get my hands on 12" or 15" drivers - but not very sure what quality they would be. Shipping from the US is going to be very expensive.

regards