Thickness of material

[Graemed14]

I am building a center channel speaker with around 3 " drivers. How thick should I make the enclosure?

[Cal Weldon]

5/8"

[Graemed14]

Thank you. Could you provide any help in terms of explaining infinite baffle and sealed enclosures to me? I'm not exactly clear as to how that works. In an infinite baffle system, the cone does not have any pressure from behind, so do infinite baffle systems not have as great of response as sealed enclosures?

[raypalmer]

Originally Posted by Graemed14

Thank you. Could you provide any help in terms of explaining infinite baffle and sealed enclosures to me? I'm not exactly clear as to how that works. In an infinite baffle system, the cone does not have any pressure from behind, so do infinite baffle systems not have as great of response as sealed enclosures?

Oh boy. I don't think I want to wade too deep into this one with you. But IB and sealed are but two of the types of cabinet. There's also aperiodic and transmission line and reflex and it's all great fun.

Theoretically an infinite baffle is the best enclosure (but it's not an enclosure, by definition it's a baffle, or barrier) because the sound waves from the back of the driver never interfere with the front. Thus the pressure on either side remains equal.

BUT

It's got to be huge to work well. AND, it's really a theoretical construct more than anything, because infinite plywood isn't readily available. Open baffle would really be what you're thinking, but then your TV would be blocked by a giant piece of plywood with a little speaker on it. Not so good for theatre..

You're almost certainly going to want to build a vented enclosure of some kind. It gives better SPL lower down by allowing the backwave of the woofer to resonate out of the port, the cabinet effectively tuned with the port will give you an audible and appropriately loud port resonance.

But don't forget the baffle step compensator. Which I would ask one of the more engineer type guys about because I have no idea how that works.

[AllenB]

Look at the infinite baffle as a large closed box. A small closed box will support the cone more. Woofers designed for infinite baffle mounting might have a stiff suspension to compensate for not having the air cushion behind them.

If you already have the drivers, you could probably put this aside and just concentrate on the best volume for your enclosure.

[planet10]

If you are using good plywood 12mm is fine.

Think of the sealed box transitioning to an infinite baffle as the the volume of the box gets large. You can consider it large when the system Qt of the box gets close to the driver Qt.

dave

[Cal Weldon]

IB used to mean IB. Now in the days of low Q drivers it seems to to mean a sealed box at least 3X the woofer Vas. IB cabinets were the best in the days of high Q and low cone travel. Low Q drivers lose a lot in IB. (read no bass).

A true IB would be a round piece of wood with a 57 foot diameter to ensure no cancellation of waves down to 20 Hz.

[AllenB]

I first picked up on that definition in Vance Dickason's book. I think I'd settle for 'virtually' an infinite baffle. But then again, in engineering parlance anything that is a factor of ten more significant that another, renders the other 'insignificant'. I'm not sure we'd all agree with that always.

[Graemed14]

Thanks a lot for all the great information. I have one more question, what kind drivers are common to put in center channels if using the same ones as in your L/R channels are not an option?

[Cal Weldon]

Sensitive, good vocal full rangers like Fostex.