Speaker cab design questions

[Jim Phelps]

Does size matter? Ahem... I mean, I know that in a closed-back cab the dimensions are very important, but in an open-back cabinet, how important are the dimensions of the cab, how much if any does the size of the cab affect the sound? For example, would an open-back cab about the size of a Twin Reverb containing two 12-inch speakers sound any different than another open-back cab that was bigger?

Also, does the thickness and hardness of the wood in the cabinet sides affect the tone? Does a cab with sides of solid 1-inch pine sound different than one made of plywood?

And... Does closing off the upper and lower thirds of the back, leaving the center third open, make any difference in the sound compared to the whole back being open?

Thanks for any info!

[T. C. Furlong]

Everything matters. Cabinet size will affect lows and low mids, but that also depends on which speaker you use. Generally, a larger speaker requires a larger cabinet to give more low frequency response. But that might not be what you want for good tone. You may want the lows to be tailored by making the cabinet smaller. The position of the back panel will matter most if the acoustics to the rear of the cabinet are reflective. Some players mostly listen to what is coming out of the rear of an open back cabinet. That way they avoid the harsh highs that sometimes are produced directly in front of the cabinet. You've seen steel players almost sitting on top of their cabinet with most of the front sound firing under their legs.

I have found that the only way to come up with something that is good is to build, listen, measure...build, listen, measure. Or in the case of cabinets that are commercially available, listen measure...listen, measure.

Cabinet material is an interesting debate. It is a factor but pretty far down the list of what matters most. Here is what I think counts most:
1. The speaker itself
2. Open or closed back
3. The size and quantity of the ports (or rear opening)
4. Cabinet size
5. Baffle board design (floating or not)
6. Rigidity and mass of the cabinet
TC
<font size="1" color="#8e236b"><p align="center">[This message was edited by T. C. Furlong on 31 October 2006 at 05:45 AM.]</p></FONT>

[David Doggett]

My only advice for a steel or guitar cabinet is to take your size cues from other steel and guitar cabinets, not from bass or PA cabinets. The latter are designed to boost lows down where there are none for steel and guitar, and will have you building cabinets much bigger and heavier than you need.

Seems like the main criteria for material is rigidity. Particle board is duller, cheaper, heavier and weaker. Plywood is good. Solid wood is supposedly better, but seems like the sound difference is pretty subtle. Some guitar and steel amps have very flimsy back panels, in open and closed back models. I guess this is to keep costs down. But in terms of rigidity and thickness, I don't see why back panels are any less important than the sides and front baffle.

[Gene Jones]

A suggestion, and only a suggestion, is to take the dimensions of a cabinet that has the sound you like, and build one like it!



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<img width=100 src=http://genejones.bizland.com/index.1.jpg>www.genejones.com

[Donny Hinson]

As T.C. says...everything matters!

Generally speaking, <u>all</u> musical instrument amps have cabinets smaller than what is optimum for reasons of portability. For the same reason, most cabinets are made of the thinnest and cheapest materials that they can use to eliminate unwanted resonances, and reduce weight.

Years ago, I built a 2-15" cabinet from Altec-Lansing blueprints. At 52" high, 26" wide, and 14" deep, it's size, weight, and bulk presents a big problem to haul it around, but it sounds better (far better) than any "factory cabinet" I've ever heard.

[Jim Phelps]

Thanks for your replies, all.