'Quick' subwoofers

[Bill poster]

I want to make a small subwoofer to match some small full range satellites and I'm worried that the sub might not keep up with the sats. I know that Sealed enclosures offer a fast bass sound but I'm set on a BR sub ie if I go for a smallish woofer (6.5")and keep the box size optimum(not too big) and port length tuned properly (not too low) etc is this the right approach?

[Kjeldsen]

Fast is kind of a contradiction when talking subwoofers. I know what you mean and "slow" subwoofers i think is coming from manufacturer who try to get de deepest bas out of a small box, and tuning the BR wrong. This gives a "one-note" bass that I think relates to "slow" bass.

A fast bass have I only heard from big subs, where the cone don't have to move very much, and where the cabinet is designes with er proper size according to the thiele/small parameters.

Reading you comments, you are on the right track, but I would go for at least an 8" woofer with a low fs - (BUT not because of high mass), and a Q that is not to low either.

[Kjeldsen]

THis one looks like crap, but it's got IMHO som good classic data, that makes it suitable as i hifi woofer.

SPH-212

[Veke76]

I had the same starting point in project and ended up with Peerless SLS 6,5" 8L bass reflex enclosure. I modelled it to go near 32Hz and reach 108dB in room. It's not finished yet but because of using slot ports I get some port noises. Using this driver I would go passive radiator design now! Otherwise I would rather think of something bigger...perhaps Peerless XXLS-10" in 26L sealed enclosure. It would go near 25Hz and reach 116dB in room.

[Bill poster]

Thanks for the advice! nice unit but I'm looking for a max 25 litre volume. I found this -its specified as a car sub but think it could be suitable? It's good value. The peerless range looks good too.
IT Speaker Shop - MDS08 | Loudspeakers > Nova by Intertechnik > MDS Series

[Kjeldsen]

Hard to tell with no T/S parameters. A car woofer is often designed to work with the cabin gain in a car, and will often sound thin in a living room.

[Bill poster]

Here we go, it plots well on winisd. The smaller 6.5" also. It has some useful sensitivity over the sats, so I think I could get nice response if I design the x/o correctly. The only thing I'm not sure about is the 4 ohm rating and how that works with both channels in one etc?

Lautsprecher Shop Intertechnik - MDS08 | Lautsprecher > Nova by Intertechnik > Subwoofer Lautsprecher

[5th element]

Originally Posted by Bill poster

Here we go, it plots well on winisd. The smaller 6.5" also. It has some useful sensitivity over the sats, so I think I could get nice response if I design the x/o correctly. The only thing I'm not sure about is the 4 ohm rating and how that works with both channels in one etc?

Lautsprecher Shop Intertechnik - MDS08 | Lautsprecher > Nova by Intertechnik > Subwoofer Lautsprecher

3.5mm of one way xmax? This is not a subwoofer by any definition that I would care to use.

[Bill poster]

7mm is enough for this application I reckon, I don't want to blow the sats. Maybe the smaller mds06 is a another option, same xmax and similar extension (higher qts)

[5th element]

Well blowing the sats has nothing to do with how much Xmax the woofer really has. The Xmax and other woofer stats represent what extension and SPL the design will be capable of.

Out of the three parameters in Hoffman's Iron law you've got box size(how small), extension (how low) and SPL (how loud). You are allowed two of them, ie you can have a small sub with good extension that cannot go particularly loud. In your case as SPL is not a requirement exploiting the how low/how small part would seem like the natural thing to do.

A sub that can go down to 20hz or down to 40hz isn't going to sound any 'faster' then another unless it's designed improperly.

Another issue might be with room modes. If you've got a speaker with extension down to 80hz, adding in a sub that can go down to 30hz would allow other room modes to be excited. Now depending on where these lie it could dramatically add to the sensation of one note bass.

In small rooms though modal behaviour ends around 40hz anyway, so getting that extra 20hz wouldn't cause any extra excitation. A small 8" sub wont really do 20hz either, but that's not really the point.

Something like this is more in line with what I'd be thinking about. A 15 litre box tuned to 30 hz or something. I can't run a full sim now because I don't have the time.