Sealing an Open Back Cab - Tips

[chaosMK]

I picked up a semi-open back Avatar 2x12 guitar cabinet (for guitar) a while back and wanted to seal it. Anyone have experience with this? Avatar sells a kit but it basically looks like a thin piece of wood and some screws. I can get that on my own.

Basically my plan would be to line the cab with some dampening material and screw a plate (ideally similar material/thickness to the back.. not sure what it is, probably plywood) over the opening.

I'd post on a guitar forum, but I never have any luck getting facts from those places!

[darkstorm]

Your idea of installing sound insulation is excellent. Ive used polyester high loft batting roll for small to medium bass combo amps and speakers several times. I layer it so youve got a good inch thickness. Applied to back, floor, sides and ceiling of cab insides. But not blocking the sound port of course. Ive also used it for low to mid price home stereo speakers which either didnt come with any insulation, or that have that horrible fiber glass nonsense. Sound improvements are tighter bass, more pleasant mids and highs, and a bit better stereo imaging. Same effect for single instrument cabs like bass and keyboard/synth rigs to.

Anyway, the two conciderations you'll have for good results is A. Figuring out right size round hole, ro slot rectangle port to put in it. And useing speakers designed to perform well for the speaker cab size. And yes, qaulity plywood is best choice. Lots of cheap to mid price combos use fiberboard which is horrible to. MDF is better, but plyswood is best. I think carvin uses Pinem plywood for both strength and lightweight. Btw plywood cab will weigh less then most any mdf or fiberboard one.

Anyway, have you checked speaker mfg wether celestion, jbl, or whatever, to see if the speaker model in the cab now are listed for both open and closed back cab?

[B-string]

Line the outer sealing edge with felt to provide a seal and prevent buzzing.

[1958Bassman]

Originally Posted by darkstorm

Your idea of installing sound insulation is excellent. Ive used polyester high loft batting roll for small to medium bass combo amps and speakers several times. I layer it so youve got a good inch thickness. Applied to back, floor, sides and ceiling of cab insides. But not blocking the sound port of course. Ive also used it for low to mid price home stereo speakers which either didnt come with any insulation, or that have that horrible fiber glass nonsense. Sound improvements are tighter bass, more pleasant mids and highs, and a bit better stereo imaging. Same effect for single instrument cabs like bass and keyboard/synth rigs to.

If it was made as an open back cabinet, it won't have a port.

[1958Bassman]

Originally Posted by chaosMK

I picked up a semi-open back Avatar 2x12 guitar cabinet (for guitar) a while back and wanted to seal it. Anyone have experience with this? Avatar sells a kit but it basically looks like a thin piece of wood and some screws. I can get that on my own.

Basically my plan would be to line the cab with some dampening material and screw a plate (ideally similar material/thickness to the back.. not sure what it is, probably plywood) over the opening.

I'd post on a guitar forum, but I never have any luck getting facts from those places!

It may work, or it may not. If the speaker needs a large cabinet or is made for infinite baffle (open back), you'll lose low end. OTOH, I made an open back cabinet for an Altec 417B and open, it worked great for guitar, but I closed the back and then, it was great for bass. It really depends on the driver. If you post the model of the speakers, I can model a cabinet fro you in my box design software. Show the cabinet dimensions, too.

[billfitzmaurice]

Originally Posted by 1958Bassman

If you post the model of the speakers, I can model a cabinet fro you in my box design software. Show the cabinet dimensions, too.

Guitar drivers in general don't benefit from ported enclosures. The drivers don't use specs appropriate for VBs and the frequency response of the guitar doesn't go low enough either.

[chaosMK]

Thanks for the tips everyone.

The cab has Emminence Black Powders (a kind of uncommon not-a-lot-of info online bright/mids oriented speaker). I talked to a rep from Emminence and he said there would be no harm in using them with a closed back.