Speaker Cabinet Alteration?

[Teleblooz]

Right now, I'm running my Crate V33H head into a 1x15 cabinet that used to be a Sunn Studio Bass combo amp. It originally looked very much like this:


The top end no longer has the amp head in it, and I made a longer grille cloth frame that covers the empty space.


The problem, if it can be characterized as such, is that the cabinet is a closed-back, ported box that is ideally suited to what it was designed for, which is to reproduce bass frequencies. While it sounds pretty nice as is, I have to severely roll off the bass EQ on the amp or the thing gets pretty boomy.

I'm thinking about opening up the back by cutting out an 8" section in the hope that it'll optimize the tonal characteristics more in the guitar realm. Anybody have any experience in this kind of cabinet surgery or advice on whether this is even a good idea?

[cynical1]

You have a few things working against you here. As you noted, this is a bass cabinet with the port specifically designed for this loudspeaker. You also have a 15" loudspeaker in this cabinet...not exactly know for their range and definition...

I would suggest reading JohnH's posting Speaker cab for electric and acoustic and follow some of the links mentioned there about cabinet design.

I would suggest against cutting an arbitrary hole in the back of the cabinet. While this may reduce the boominess of the cabinet, if you cut too large a hole and create phase cancellation you'll reduce everything else as well.

You could try mounting a pair of peizo units in the cabinet as JohnH did. These will go a long way to adding more high end and definition and they're cheap. They won't come in until around 4000 hz, so you're still up against the 15" speakers range issue, but I'd try that before I started surgery on the back of the cabinet.

Happy Trails

Cynical One

[newey]

One question: The big rectangular area at the top, where the amp used to be- is that sealed off from the speaker cab or is it open to the cab?

If it's open, cutting another hole in the back isn't going to do much of anything.

I agree with Cynical1, a tweeter or two may be more what you're after. These could be put in a separate enclosure if you don't want to cut up the Sunn cab.

[Teleblooz]

The space on top is isolated from the speaker chamber.

The 15 isn't specifically a bass speaker; it's a JBL (I forget the model) that I pirated out of a PA cabinet. It does a pretty decent job with the upper range frequencies.

The issue for me isn't one of getting more top end (I mean c'mon - I play a Telecaster after all :, rather, as cynical1 said, of reducing the boominess of the low end.

I'll check out that link tonight when I can do it at my leisure. Thanks - your replies speak directly to the concerns I have.

[cynical1]

I had another thought about your boomy cabinet problem. Acoustic insulation. You can buy the professional type stuff, but that gets a tad expensive. For the R & D phase drive over to any fabric store and pick up a few rolls of polyester batting. Same stuff they use to make quilts.



Without anything more then a staple gun you can pull this off. Take off the back and just staple about 1" of this stuff on the inside of the cabinet and the back plate. Don't block the port.

This may not solve all of your issues with this cabinet, but it should tighten up the boominess.

And you can make a pillows out of what you have left.

Happy Trails

Cynical One

[andy]

Have you checked out the specs of some of the 1x15" Fender cabs?

There are an increasing number of 15"ers on their books, the Steel King, Jazz King, and 65' Twin Custon 15.

I'm sure they are fully open backed and that may help issues- was there a specific reason for the 8" hole you planned to cut?

[JohnH]

A 15" for guitar can be great - like on a Peavey Delta blues combo.

I reckon the first thing to try is just take the back right off - it might be just the right balance and theres no loss if not since nothing has been hacked. Partial openings can end up acting as ports wich affect certain frequencies, causing some weirdness as I found with my cab build.

John

[Teleblooz]

Feb 26, 2009 21:06:45 GMT -5 JohnH said:

A 15" for guitar can be great - like on a Peavey Delta blues combo.

I reckon the first thing to try is just take the back right off - it might be just the right balance and theres no loss if not since nothing has been hacked. Partial openings can end up acting as ports wich affect certain frequencies, causing some weirdness as I found with my cab build.

John

That thought occurred to me too, but the back's not a bolt-on - it's on there permanently. Everything inside is accessed from the front. One thought I had was to cut the section out in such a way that I can screw it back into place if need be.

[lunaalta]

Just an idea, but have you tried blocking up the port? It may be there to augment bass sounds for it's original purpose...
Just an idea that should be easy to check out.

[Teleblooz]

Mar 30, 2009 11:34:46 GMT -5 lunaalta said:

Just an idea, but have you tried blocking up the port? It may be there to augment bass sounds for it's original purpose...
Just an idea that should be easy to check out.

On your suggestion I tried that, and it did seem to help some, but then something happened that made the whole point moot.

About 3 weeks ago, I got my American Musical Supply catalog in the mail. And what should I find in the amps section but a Crate V-series 4x12 cabinet for $199.95? After agonizing over it for a good twenty seconds, I pulled the trigger on the slant-front version.

The cab showed up about a week later. So I finally own my first half-stack. At 73 lbs, it's kind of a bear, but it came with a good set of plug-in casters. And it sounds great! My bass player (who has the best ears in the band) heard it for the first time at last Friday's gig, and says it's the best he's ever heard from me tone-wise.

I'm pretty jazzed about the whole deal. Not only does it sound good, but it matches my V33 head - and the whole rig together cost me less new than my Blues Junior did used!