Lightweight cab design question

[Twincam]

Was just wondering do lightweight cabs lose anything or gain anything over a heavier cab? Due to transfer of energy into the cab making it vibrate, from mechanical energy from the speaker itself moving and also sound wave energy bouncing off surfaces.
Or is the difference so small it would not matter?

[chris_b]

Cabs are usually made from 3/4" Baltic ply so the sides don't vibrate. This design is the cheapest in materials and easiest to build. Many lightweight cabs use the same materials in the cab and just use a neo speaker chassis.

Barefaced cabs use thin ply but extensively brace the sides to maintain rigidity and prevent energy (ie tone) being lost through the vibrating panels.

IMO 30lbs is good for a 112, anything less is a bonus and 45lbs is good for a 212.

[Twincam]

[quote name='chris_b' timestamp='1455369585' post='2978491']
Cabs are usually made from 3/4" Baltic ply so the sides don't vibrate. This design is the cheapest in materials and easiest to build. Many lightweight cabs use the same materials in the cab and just use a neo speaker chassis.

Barefaced cabs use thin ply but extensively brace the sides to maintain rigidity and prevent energy (ie tone) being lost through the vibrating panels.

IMO 30lbs is good for a 112, anything less is a bonus and 45lbs is good for a 212.
[/quote]

Possible daft but has anyone seen if you can gain anything from having the cab vibrate somewhat? In terms of tone/frequency response.

Too add I've seen a lot of variation in cab material and thickness and weight. But I get your point.

Edited February 13, 2016 by Twincam

[Bill Fitzmaurice]

It depends on the cab construction. A well braced cab made of 12mm plywood will perform better than a poorly braced cab made of 18mm plywood. Most manufactured cabs are made of 18mm not because it's better, but because it's cheaper. Installing proper bracing increases labor costs.
[quote]Possible daft but has anyone seen if you can gain anything from having the cab vibrate somewhat?[/quote]Energy expended vibrating cabinet walls is energy that doesn't get translated into sound output.

Edited February 13, 2016 by Bill Fitzmaurice

[Twincam]

[quote name='Bill Fitzmaurice' timestamp='1455369861' post='2978499']
Energy expended vibrating cabinet walls is energy that doesn't get translated into sound output.
[/quote]

Yes that is simple to understand of course, I'm just wondering if anyone has experimented with this in some sort of strange cab design. I don't think myself there would be any benefit or it would work I just like to hear any off theory experiments.

[Phil Starr]

Any energy used in vibrating the cab itself is wasted energy of course. Since the amount of energy absorbed is frequency dependant the cab vibration will result in changes in the frequency response and a resonating cab is going to have an uneven frequency response. Most speaker designers are going to be designing to get as smooth a response as possible and even if you are going for a tailored response then it is hard to predict what a cab will do to the response so tailoring a cab by making it resonant is pretty nearly impossible.

However non-flat cabs and music sometimes work well together. Guitarists go for highly coloured cabs to get their 'sound'. In a sense a lot of 60's and 70's cabs were 'experimenting' with this as they were often put together with very little theoretical knowledge and then just tested by playing through them. Some of those designs still continue and people love their sound, so yes theoretically and in practice there can be benefit in a non-flat, resonant design.

Currently the trend in boutique bass cabs is to make them as flat as possible. Personally I think that is the way to go, with cab and amp simulators getting better and cheaper all the time. With a flat cab and some electronics you can have all the sounds from clean to Ampeg with a couple of lightweight cabs.

Finally on bracing, There will come a point where bracing makes little difference to what you can actually hear, and all that bracing adds weight. Alex Claber has said here that the main aim of his bracing was rigidity rather than weight reduction which comes as a side benefit. Thick panels on small cabs are inherently rigid and mass is a useful damper of resonances so for a small cab you can have a successful speaker with minimal bracing. It's also critical how you do the bracing, you can simply shift the frequency of panel vibration to higher and more irritating frequencies in the worst cases. I think what BFM has said about a well designed thin walled braced cab being better than a poorly designed thick walled cab is absolutely fair but that adds considerable expense in manufacture. It might be better to spend that money on the drive unit and stick to a simple cab at a particular price point.

[Twincam]

[quote name='Phil Starr' timestamp='1455435326' post='2978996']
Any energy used in vibrating the cab itself is wasted energy of course. Since the amount of energy absorbed is frequency dependant the cab vibration will result in changes in the frequency response and a resonating cab is going to have an uneven frequency response. Most speaker designers are going to be designing to get as smooth a response as possible and even if you are going for a tailored response then it is hard to predict what a cab will do to the response so tailoring a cab by making it resonant is pretty nearly impossible.

However non-flat cabs and music sometimes work well together. Guitarists go for highly coloured cabs to get their 'sound'. In a sense a lot of 60's and 70's cabs were 'experimenting' with this as they were often put together with very little theoretical knowledge and then just tested by playing through them. Some of those designs still continue and people love their sound, so yes theoretically and in practice there can be benefit in a non-flat, resonant design.

Currently the trend in boutique bass cabs is to make them as flat as possible. Personally I think that is the way to go, with cab and amp simulators getting better and cheaper all the time. With a flat cab and some electronics you can have all the sounds from clean to Ampeg with a couple of lightweight cabs.

Finally on bracing, There will come a point where bracing makes little difference to what you can actually hear, and all that bracing adds weight. Alex Claber has said here that the main aim of his bracing was rigidity rather than weight reduction which comes as a side benefit. Thick panels on small cabs are inherently rigid and mass is a useful damper of resonances so for a small cab you can have a successful speaker with minimal bracing. It's also critical how you do the bracing, you can simply shift the frequency of panel vibration to higher and more irritating frequencies in the worst cases. I think what BFM has said about a well designed thin walled braced cab being better than a poorly designed thick walled cab is absolutely fair but that adds considerable expense in manufacture. It might be better to spend that money on the drive unit and stick to a simple cab at a particular price point.
[/quote]

Excellent post!
Thank you for taking your time posting that, especially if on a mobile device.

I agree about the flat response cabs being better especially as you said with amp technology getting better. Although the romantic in me loves the idea of cabs having a certain signiture sound.

Edited February 14, 2016 by Twincam

[chris_b]

A cab that vibrates is like a car with a slipping clutch.

[Beer of the Bass]

Some of the seemingly flawed designs from previoud decades live on in the guitar world. Tweed era Fender combos used an unbraced baffle made of thin softwood ply which was only attached at a few points around the edge, not solidly glued in. And that was true even of the 4x10" models. Some people insist that they just wouldn't sound the same with a stiffer baffle.