The Amp Garage

Geeze had a thread on a Thiele style cab he built, and billyz posted some pics of his designs.
billyz used bracing in his cab, and I have seen some commercial cabinets that used conventional dimensioned materials, but routed out in several places, I assume to lighten the weight, but would that also serve the same purpose, to stiffen the cab as the bracing would?

I think for one-offs, using 3/4" BB and routing out to 5/8" or 1/2" could save some weight.

You haven't been specific -- are you interested in a 1-12" guitar cab? T'were me, I'd just use 5/8" BB and be done with it, since the speaker + cab can't end up too heavy, even with an EVM 12L. If you're talking 2-12" or 1-15", I could see looking into Neodymium speakers and ways of lightening the box.

I sort of dislike the idea of braces, since it's more measuring, cutting, bicuit joining, gluing.

13mm (half-inch) Baltic birch will make a very nice lightweight cab and it should hold up just fine if properly constructed. I'd be careful not to allow abuse. I doubt you can go thinner with any decent result.

The store near me closed, but I remember Rockler sells 5' square sheets for a decent price. I remember being there when I was the only one in the store and the guy who was there put it on their saw and cut it for me. It was great because I got exactly what I wanted (by luck I had the cutting plan with me) and he actually knew how to operate the saw and use a rule (unlike the big box experience). There was no charge for cutting!

I've heard some thin walnut and mahogany cabinets sing at some frequencies.

Pine sings midrange. Maple high range, and walnut lower.

You can hear it when you sand the joints.

Don't lighten the baffle. It needs to be rigid. Make the back of the cabinet removeable and you can experiment with different thickness backs.

John

I don't have an immediate project in mind. I was just struck that the reinforcing would dampen the cabinet vibrations, and curious what others had done.
I did build an open back cabinet, (middle oval), years ago from 1/2 ply, and had problem with resonance. I ended up glueing rubber sheeting in several places on the sides, and back to eliminate it.

While definitely NOT an expert I when I look at the bracing on the EV TL series I think overkill. The first couple of cabs I did I put braces in the corners [glue and screws] and all of the baffle/back plate bracing the same way. Now I only glue the bracing. The back and baffle get screws.

I doubt the routing would do anything structurally - just save weight. Interesting as it might resonate as 'hot spots'. For the thinner walled cabs it would depend on what you are playing to a degree - bass heavy metal for instance vs. jazz. You could experiment by using bracing like an acoustic guitar top and 'tune' the wall response. Many drummers tune the heads by tapping the shell to hear the 'tone' and tune to complement it.

Oh crap, now you have me thinking.....

Geeze wrote:While definitely NOT an expert I when I look at the bracing on the EV TL series I think overkill. The first couple of cabs I did I put braces in the corners [glue and screws] and all of the baffle/back plate bracing the same way. Now I only glue the bracing. The back and baffle get screws.

I doubt the routing would do anything structurally - just save weight. Interesting as it might resonate as 'hot spots'. For the thinner walled cabs it would depend on what you are playing to a degree - bass heavy metal for instance vs. jazz. You could experiment by using bracing like an acoustic guitar top and 'tune' the wall response. Many drummers tune the heads by tapping the shell to hear the 'tone' and tune to complement it.

Oh crap, now you have me thinking.....

That's what I did with the bracing pattern I used. The bracing grain is perpendicular the panel for stiffness as well. The front
To back struts act just like the sound post in a violin. Again a tuning thing.
I find this construction much
Lighter than any ply cabinet I have ever used and sounds better to me
As well.

The heavier the baffle the brighter the sound. I like a thinner baffle to warm the sound, but heavy enough to not buzz. 3/8 to 1/2 max.

Cantplay wrote: ↑Thu Jan 09, 2014 8:11 pm I've heard some thin walnut and mahogany cabinets sing at some frequencies.

Pine sings midrange. Maple high range, and walnut lower.

You can hear it when you sand the joints.

I got an unfinished pine 2x12 the other day for a pair of '61 Hammond donor speakers. Right now the front and back are removed so I could stain the baffle and attach the grill cloth.



I was really surprised at how much it sounds like a drum when you tap the center of one of the longer sides. When I match the resonant pitch by whistling, my guitar tuner app calls it C# at 1100(ish) Hz, and if I point the mic directly at the cab the tuner app says it's 3 octaves lower, C# at 137 Hz. So the fundamental resonant frequency and the pitch my ears picked up on are both C#. Now that I know a little bit more about how this particular pine box resonates, I'm even more eager to get the speakers in and see if I can hear any major differences between playing a C# and any other notes.

The stain should be dry on the baffle by the time I wake up, and I'm not expecting the grill cloth to cause any setbacks. I'll try to remember to get a recording of the cab sounding like a drum before I put it back together, hopefully I won't be in too much of a hurry and skip that step.

I just can't help myself...I can see that's one sharp cabinet. <groan>

Here's the empty shell of a cabinet:
When I put the baffle back on (no speakers yet) the tuner app said the resonant freq dropped a little over two octaves to B at 31.7 Hz.

With the speakers in it was reading D# at 154 Hz.

Then I ran into a snag. At least 2 of the 6 crimp on speaker connectors had been crimped onto the insulation and not the wire. So I cut all the connectors off and I'll do them right tomorrow after a trip to the hardware store.

The very distinct resonant frequency of this cab didn't end up being obvious at all once the speakers were connected to an amp. There aren't any single notes that set the box ringing like tapping on it with a finger does. I'm thinking that maybe that same resonant freq is hiding in every note that gets played through the cab? I don't know right this moment whether there are any software spectrum analyzers that are any good. Hopefully I'll come back to this idea with more observations somewhere down the road.

I would definitely think that those resonances will change drastically once you insert a speaker, and drill in a baffle etc. that changes the fundamental data of the cabinet itself, and how it responds to noises in it. The speaker cone moving air will cause reflections off the metal speaker base, the back of the cabinet, the sides etc in extremely random ways that just tapping an empty shell can't replicate.

~Phil

Interesting observations!
Back in the 80's, we put together a country band, but were still using our R&R PA, with the 13 CF EV designed cabs. I was building a couple of 7 CF EV bass cabs in the garage, while listening to music through the old PA. I stuck my head in through the speaker opening to inspect the insulation before I installed the speaker, and realized that the cabs really were designed to emphasize certain frequencies!
(The smaller cabs with the HR90 horns, worked just fine for the venues we were playing! No need for the huge bass cabs, and the 2-12 mid cabs!)