Can I put a speaker with a Q of .3 in a sealed box?

[sardonx]

I want to use four 8" long throw sub-woofers in a sealed enclosure. They're the tang band one with 12 mm x-max. My only problem is that they say for a sealed enclosure you gotta have a driver Q over .4

This particular driver's Q is .3. Would it work?

[sreten]

The speakers have a Vas - the suspension stiffness which is
expressed as an equivalent box volume.

This and the cone mass determine Fs - the free air resonant frequency.

When you put the driver in a box the box volume combines
with Vas to raise the stiffness and the resonant frequency
goes up and at the same time the Q goes up.

Its the Q of the driver in the box that counts not its free air Q.

So yes you can, absolutely, but you need the right box volume
per driver for the Q you want. But note that sometimes to get
the Q you want the resonant frequency in box can be too high.

Try playing around with one of the box calculators here :

http://www.speakerbuilding.com/software

/sreten.

[GM]

Sure, but it will have a high F3, so will be more midbass than sub-woofer. Since you have four, you could put them in a low Q sealed cab (big) and use EQ to flatten the in-room response, at the expense of efficiency of course.

GM

[sardonx]

Cool.. thanks guys.

Actually raising the Q is exactly what i want to do. I'm thinking about using something like the ELF (or EAS as Rod Elliot calls it) subwoofer controller where you raise the Q of your woofer(s) to the point where the new resonance frequency is about the same as your main speakers (your satellites, midranges or whatever) and you operate your subwoofers below their new resonance peak. Then you use equlization and mega huge amps to get a perfectly flat responce down to 20hz.
The only thing that boggles me is this - From modeling, to get four of the woofers i want to use to have a resonance frequency as high as the mains i'd have to put them woofers in a ridiculously small sealed enclosure (.2 cubic feet for the four of them - 8 inchers!!!!) and then flatten out the responce and drive 400 watts into them!!! There is something slightly disturbing about that concept and common sense tells me it aint gonna happen. If it would work out it would of course be the greatest thing in the world - .2 cubic foot enclosure with that goes down to 20 hz. Hmmmm... what a nice thought
Although in reality i'd just end up blowing the woofers with the 400 watt amps. I guess i'll have to look for a better woofer for the job.... -or seek mental help

[womiller]

If you have a choice of speakers other than the TangBands, I suggest you look at Human Speakers 6" and 8" woofers, at about $60 USD each. They are intended for sealed systems and have been used in commercial speakers. The 8" woofers are very forgiving of box size. They are recommended by LDSG. The models of interest are

003 6" woofer
007 6" long throw woofer
008 6" 2 ohm long throw woofer

001 8" long throw woofer
005 8" extra long throw woofer
006 8" 2 ohm long throw woofer


http://www.humanspeakers.com

[sreten]

There's something extremely wrong with your modelling.

By mains I believe you mean your other speakers - there's
no reason why this frequency is relevant to the bass alignment.

Your subwoofer amplifier will control the frequency the sub
crosses over to the mains and this is low pass function,
completely seperate to the high pass function of the bass
alignment.

/sreten.

[sardonx]

By mains I believe you mean your other speakers - there's no reason why this frequency is relevant to the bass alignment.

Actually, there is a very clear reason why it's relevant. If you visit Rod Elliot's sound pages and the subwoofer processor project,

http://sound.westhost.com/project48.htm

you'll see that the frequency at which the cut off for the main speakers is at is very relevant since this is where you have to bring the subwoofer's system resonance to.

This is not just 'adding' a subwoofer at any frequency. The purpose of this thing is to have a flat responce and smooth integration from mid to woofer down to 20 hz.

How much are the human drivers??

[sreten]

You are quite right,
sorry I should have read your post more thoroughly.

I couldn't find a TangBand 8" bass unit at Parts Express.

The post above states the Human drivers are around 60 USD each.

/sreten.

[sardonx]

Sreten,
Parts express doesn't carry that driver. Tang Band is a bit weird like that, you never know what to expect from them. Go here...
http://www.nuera-acoustic.ca
they carry the 8" tang band and an interesting 6X9 too along with a bunch of smaller ones.

I have to say that the human drivers look nice. But the tang bands are cheap.. and they look cute too

[sreten]

Nice unit - good price !

I'd say forget about the EBS stuff.

Just put them in a box and design towards Q=0.6.

What box volume and box F do you get ?

/sreten.