Big n Fat

lowmass

Member
2016-01-26 12:46 am
A few years back I started playing with box size/shape/bracing/ material/damping..... I first worked out crude simple ways to make cheap cabinets quickly that although look ugly, were both well damped, AND stiff.
A far more difficult combination than most think BTW ;)

Now please dont get into all the details about the strengths / weaknesses of stiffness and damping etc etc. Trust me I get it. In the end I worked out a way to get both easily. I could get very good results from cheap 1/2 " particle board (yes thats what I said ;) ), so long as the bracing left no more than 3 inches or less cab wall between braces, the braces were no less than 4 inches tall when set on edge, the braces went fully around inside of walls , the braces include cross bracing to opposite walls, AND this is a big one, All bracing was glued to walls and each other with a semi soft setting construction adhesive ( important that glue line was about 1/8 to 1/4 inch thick. The combo results in excellent mid freq resonance suppression AND quite serious stiffness no mater cab size.

Yes, a butt load of bracing etc doesnt sound like a cheap and fast cabinet. But when you dont care about looks at all, and are simply slapping rectangular braces in places using literally GOBS of construction adhesive (urethane sub floor adhesive), using sheet rock screws with no pre drilling to hold the whole mess together while it sets enough to be stable, then remove screws, you can bang together a high perf test bed cab in a short time.

OK so to the point of thred...

I spent years with only open panel planer magnetic bass drivers. Literally a couple hundred prototypes. When I switched to playing with pistons in a box I was disappointed. Love the loudness and precieved dynamics BUT I could never seem to get that ultimate sense of open transparent tuneful bass/ mid perf of open panel.
Now this was always using the typically more acceptable tall thin cab. No matter what I did with shape / size it just never quite impressed enough.

One day I decided to build a fat one. A fat wide box instead of the taller thinner shapes. From the get go, from the first box I finally heard for the first time, a similar sound to the open panel stuff.

I supose some will say for a given volume/ shape, its all in how you damp the box internals BUT seriously, hundreds of different cabs latter and all kinds of different internal damping materials / shapes/ sizes latter, its hard to imagine thats all there is to it.

For the moment I will take the well built Fat girl over the cat walk regulars.
 

ILikeFoodz

Member
2014-06-22 12:33 pm
One thing that this will affect is the frequency the baffle step occurs at. A wider baffle will reduce the frequency. If you haven't compensated for baffle step in previous crossovers, this could cause a significant reduction in perceived bass response. Baffle step will cause a theoretical 6dB drop in response, which in practice is usually fewer dB than 6 becauze of room gain. However, that room gain will be from reflections off of the rear wall, which can cause muddiness in the sound since it is delayed relative to the direct wave coming from the speaker.
 

lowmass

Member
2016-01-26 12:46 am
yes good point. Yes this was always compensated for in crossover AND even at times tryed many times putting equil sized baffles on the front of tall thin cab versions.

For whatever reason the big wide deep cabs are easy to get the sound Im talkin about.
Again, and maybe this is just me, I spent years developing planer bass panels to the point where my hearing was tuned in so to speak to that open ( sorry all I have is subjective terms) sounding bass.

Also not sure if or how much to do with it, but Im talking mostly 10" and 12" pistons used anywhere between 500 and 1khz in two way systems. And perhaps important to note ALL the planer system were also 500-1k crossovers
 
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For the moment I will take the well built Fat girl over the cat walk regulars.
Being presumptuous I know, but you can assume one is good in the kitchen and the other is good in another room.

Actually, there's no mystery. The days of the Altec squatters is over. The catwalk ones appeal to WAF. Less foot print, more chance of having them in your living room.
 

zman01

Member
Paid Member
2011-02-04 11:35 am
Dhaka
AND this is a big one, All bracing was glued to walls and each other with a semi soft setting construction adhesive ( important that glue line was about 1/8 to 1/4 inch thick. The combo results in excellent mid freq resonance suppression AND quite serious stiffness no mater cab size.

lowmass,

Interesting observation. I recall reading that KEF did something similar in concept by having "damped bracing" for the LS50.

Can you give an example of such an adhesive?
 
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I supose some will say for a given volume/ shape, its all in how you damp the box internals BUT seriously, hundreds of different cabs latter and all kinds of different internal damping materials / shapes/ sizes latter, its hard to imagine thats all there is to it.

Assuming they set on and perpendicular to, the floor, then the wider box has more baffle end correction, so this acoustic width in turn yields a much wider 'mirror image' [2x] gain.

The downside is that if you try with a mirror it doesn't take much tilt to lose most of it, so for other than bass apps, not very practical unless you like to listen sitting on the floor.

Since late '96 I've been telling folks on/off-line that up to a point of diminishing returns that wider is better, though over time it got lumped in as 'bigger is better' [BIB] rules.

In short, acoustic solutions to acoustic problems.

Unfortunately, there's been an obvious shrinking of mass market room size, increasing noise restricted apt., etc., homes in the USA, so will be[come] just a 'pipe dream' for many. :(

GM
 

freddi

Member
Paid Member
2005-08-16 4:21 pm
LWSUKJ8.jpg
 

boswald

Member
Paid Member
2014-06-27 3:32 pm
Since you have tried matching baffle size and heard little difference, I suspect the internal reflections are what bothers you with a smaller volume.
The intensity of the internal reflections falls exponentially with distance, so you may have found a happy spot for you, there will be a diminishing return on building ever bigger boxes.