What's the best design for a subwoofer?

[walpurgis]

In your opinion what is the best cabinet/system design for a subwoofer? What would you build? Me personally, I reckon in a big enough room, I'd like give a large, properly tuned and damped quarter wave column a whirl, with maybe a 15" driver. That should give some nice, house shaking, crunchy bass. Geoff.

[sq225917]

I'd build a sub that was suitable for the construction of the room. ;-)

[walpurgis]

You could build one that was part of the construction of the room. Using a redundant fireplace and chimney would work as a virtually infinite transmission line!

[sq225917]

I have just such a vacant chimney in my hifi room...

[Bluedroog]

Have you guys ever seen this? :eek:

http://www.royaldevice.com/custom.htm

[walpurgis]

Damn, who gave you those pictures of my listening room?

Seriously though, quite a few people have built themselves huge under-floor or in-wall speaker systems. I recollect John Crabbe of Hi-Fi News building huge concrete bass horns into his listening room walls many years ago, these were if I recall each driven by a pair of KEF B139s. The project was featured in the magazine.

[daytona600]

seen that mad underground bass horn before , thought must have delay problems due to its length compared to the Mid/Hf , Must fall into the more money than sense bracket
would not mind spending a couple of hours with some dub/techo/trance on that rig though

[Reid Malenfant]

If you are going to ask it to reproduce bass in music then a sealed box will give the best sound quality due to the control of cone by the air in the enclosure.

The problem is that it raises the drivers free air resonance, I don't know of many drivers with a 10Hz free air resonance :lol:

A way round it is to use a Linkwitz/Riley transform to extend the low frequency cutoff. This requires a goodly bit of power from any amp & a driver that can handle the power, they are made however :)

As I want to also use what you'd call subwoofers with movie playback I'm going to compromise a tad. While I'm not keen on reflex speakers due to the group delay caused by the port tuning, if the tuning frequency is low enough there will be only a very small delay in the audio band (20Hz & above). The group delay mainly centres on the port tuning frequency & if this is tuned to below 12Hz the entire speaker will behave like a closed box down to double the tuning frequency, or about 20Hz.

Below that the enclosure will behave like a standard reflex the deeper it goes.

The nifty part is the fact that if the rolloff of the speaker is made shallow enough (4 - 6dB per octave) below the lowest frequency you can generate a standing wave in the room, the result will be a flat in room response :cool:


So in answer to your question, a very low tuned reflex...

[walpurgis]

I suspect you may be right about reflex designs Mark. Possibly the best bass I've heard came from Altec A7 'Voice of The Theatre' speakers and they were huge reflex cabinets from the sixties and seventies. The bottom end was fluid, tight and incredibly deep and seemingly without any colouration or overhang!

Mind you the original Bose 901 from the same era (the sealed cabinet one) sounded pretty damn convincing with very low bass, but it did rely on masses of equalisation. It was flat down to below 20Hz I believe.

I do have a personal liking for acoustic columns and transmision lines though.

[Harry Hill]

No no no its the TRW-17 from Eminent Technology in the USA that you need makes all other subs look kind of pathetic!

[Marco]

Hi Dave,

Welcome to AoS :)

Before going any further, please go to the Welcome section and start a new thread, telling us what system you use and what music you like, as this procedure is required of all new members.

Thanks! :cool:

Marco.

[Reid Malenfant]

No no no its the TRW-17 from Eminent Technology in the USA that you need makes all other subs look kind of pathetic!
If you hear it, they will come :lol:

I'd love to hear one, but you do realise you need to install it in some kind of enclosure... Not too small either from what I can gather :(

Must admit I'm fascinated by the rotary bass driver...


Someone invite me round :D

[Harry Hill]

Check out their website, they did an install to simulate a rocket launch and only needed one to achieve the 120db they wanted! God what must 2 sound like?:)

[Marco]

Hi Dave,

Did you miss my post #11 (above)?

Before posting anywhere else, please go to the Welcome area and introduce yourself to our community, as directed.

Your failure to do so will result in your account being closed forthwith. This is your last and FINAL warning.

Marco.

[technobear]

The best subs are infinite baffle using a cellar or underfloor space or loft space to lose the back wave.

For more constrained domestic setups I would choose a closed box. My MJ Pro 50 MkII sounds great and complements the equally closed box JPW Golds very well.

Open baffle subs can be very good too but tend to be large and a bugger to position. They're good outdoors.

[walpurgis]

I suppose there are good and bad, but I've heard quite a few closed box subs that sound just like that. A box!

[Reid Malenfant]

I suppose there are good and bad, but I've heard quite a few closed box subs that sound just like that. A box!
A closed box sub will sound fine, as long as the driver doesn't have a high total Q & the box is built stiff enough :)

I have seen loads of people throw lots of mass at enclosures, mass isn't needed, stiffness is as the frequencies we are talking about.

While 36mm thick enclosure walls will help, you can get a far stiffer enclosure by dividing it up internally into what would effectively be much smaller enclosures. Some bracing on the enclosure walls on the top, bottom, sides, front & back & then something like hardwood dowels connecting the whole lot up together into a kind of matrix will work wonders :)

It'll make the whole thing so stiff that any panel resonances will be pushed up to an order of magnitude frequency wise above the passband.

No panels making sound means only the sound of the driver will be heard, which should be clean, driver dependent of course :eyebrows:

[walpurgis]

My missus thinks stiffness is the defining factor.

Seriously though, there are many schools of thought. Yamaha are currently marketing their Soavo speakers featuring lightweight, rather 'live' cabinets and have had much praise for their designs in the Hi-Fi press. This of course, is totally opposite to the approach they used in the NS1000 (another great design), which has an incredibly rigid, braced, stiff ply cabinet. I know the NS1000 was designed donkeys years ago, but I believe a modern variant is still available in Japan by the way.

The Spendor BC1 was somewhere in between, having relatively thin but well damped walls and that also worked well (although you can detect the port chuffing at high volumes)

How about an open baffle, should it be stiff, or is a bit of flexure immaterial? I'd be inclined to opt for rigidity myself.