Whos cab has cotton batten in it? Any DIY'ers?

[MuthaFunk]

I'm in the process of replacing all the speakers in my Traynor YC-610. It looks like the speakers I have chosen are optimized for a slightly smaller area than the cab is. I put cotton batten in it to help use up some space. I imagine it will eliminate internal reflections but I don't know if this is desirable in a bass cab. I know a few of the more modern cabs I've seen have some dampening in them. (SWR)

Does your cab have any kind of dampening? What kind of cab is it. For those who have experimented with building your own cabs, was adding dampening to the cab an option? What say you?

[kb9wyz]

I can't speak for my cabinet in particular, but I have done some studying of loudspeaker design and can answer about the batting material.

Many cabinets are made smaller than the they should be for the amount of air the driver needs for proper resistance. It's called compliance.

Batting in the cabinet slows down air movement in the cabinet simulating a larger airspace. The effect can be an up to 10% "increase" (if memory serves right) in the space in the cabinet.

This has a few effects. The most notable is that the frequency response of a cabinet is changed. A less than ideal amount of air will decrease the cabinet's efficiency in producing lows.

Now your problem is that your driver is optimized for less airspace. Two easy solutions:

1) Get a hunk of wood equal to the volume you want to reduce the space by
2) Find something lighter than wood, like a closed-cell foam, to reduce the airspace

Or you can not do that and enjoy the extra balls the cab has. Or add the batting and give it more balls yet.

But beware, too much extra air and the driver will not have the suspension it needs, so it won't be very tight. Avoid anything more than 10% more than the ideal airspace as determined by the Thiele-Small parameters of the driver.

I haven't read this stuff in a while, so if I got something wrong, someone please give me a hand.

[greenboy]

There's about 10 recent threads about damping. Here's a simple little bit: http://greenboy.us/fEARful/variousit...#DampingPorted

And by the way, kb9wyz, that stuff about simulating larger airpsace was long ago discredited. Look in more recent editions of the Loudspeaker Design Cookbook and I think you'll see that one of its main purveyors will even tell you that. The main beneit is to knock down internal reflections that otherwise come back at the cone.

[MuthaFunk]

Thank gentlemen! I guess I should run a Google search before I post for help. My cab is a sealed enclosure and that link deals with ported mostly. The little part about sealed is referring to a mid driver section of a larger speaker.

I'll do a little more research. Thanks again fellas.

[greenboy]

Same thing applies to large sealed cabs, in general, though some people just line them when they are for MI use. Cotton isn't a good way to go.

[billfitzmaurice]

Originally Posted by greenboy

Cotton isn't a good way to go.

Not the usual stuff, but recently a cotton product that resembles fiberglass insulation, without the itch, has come to market, and it might make a passable damping material, especially in transmission lines or stuffed infinite baffles. I haven't tried it yet, but I probably will eventually.

[kb9wyz]

Originally Posted by greenboy

There's about 10 recent threads about damping. Here's a simple little bit: http://greenboy.us/fEARful/variousit...#DampingPorted

And by the way, kb9wyz, that stuff about simulating larger airpsace was long ago discredited. Look in more recent editions of the Loudspeaker Design Cookbook and I think you'll see that one of its main purveyors will even tell you that. The main beneit is to knock down internal reflections that otherwise come back at the cone.

Well, that just goes to show you that it is good to be humble. I will definitely check out the new edition. I don't actually know why I don't own a copy to begin with. I thought I had one, but couldn't find it.

I have a stupid idea for a home-brewed PJB type of rig for home practice. Nothing meant to be hi fi, just something to build for the fun of it.

[greenboy]

Originally Posted by billfitzmaurice

Not the usual stuff, but recently a cotton product that resembles fiberglass insulation, without the itch, has come to market, and it might make a passable damping material, especially in transmission lines or stuffed infinite baffles. I haven't tried it yet, but I probably will eventually.

Yeah, I think I may have seen some at a home improvement store a few weeks back, but didn't even make the connection that it might be cotton-based - only that it was "itch free". Was very plush.

[MuthaFunk]

Yeah, I used some type of polly fill. It's white so I called it cotton. It's not.

[JSK5String]

I built a DIY cab and did a bunch of research on different damping materials. I settled on a memory foam matress topper. It's flat on one side and egg crate on the other. Stayed in place perfectly with Liquid Nails. Works like a champ. Here's a link to the build thread where you can see pics of it. DIY Ampeg Build, sort of...

[greenboy]

Hmmmm,

I wonder if they haven't relaxed the definition of "memory foam". The original stuff was pretty damn dense and with very little porosity, and more expensive than what I just saw. And it would likely not have been very good for the purpose.

[MuthaFunk]

That link shows some beautiful work. You have a genuine talent for cabinetry!

[fdeck]

I used poly batting material from BLT Sound, just because the experts said it was the right thing to do, and their explanation seemed credible to me.

[pnut166]

I tinkered with some cheap Seismic Audio cabs awhile back. On the advice of Bill and others, I simply ripped open some pillows with poly fill, stuffed the cabs, and blocked the ports. Made for a quite noticeable improvement in their (SA) design !

[billfitzmaurice]

Originally Posted by greenboy

Hmmmm,

I wonder if they haven't relaxed the definition of "memory foam". The original stuff was pretty damn dense and with very little porosity, and more expensive than what I just saw. And it would likely not have been very good for the purpose.

As of late the only thing I've seen at Wally World is labeled 'memory foam'. If the density is too high it can result in over-damping. Higher density is OK, as in felt carpet padding, but that's only 1/2 inch thick. But you can still find standard density foam, and for that matter polyester batts, at fabric stores.

[lbwdog]

Isn't it just as easy, and perhaps cheaper to just get some 1" batting from a fabric shop?

[JSK5String]

Originally Posted by MuthaFunk

That link shows some beautiful work. You have a genuine talent for cabinetry!

Thanks for the kind words, they are appreciated...

[BassmanPaul]

Originally Posted by MuthaFunk

I'm in the process of replacing all the speakers in my Traynor YC-610. It looks like the speakers I have chosen are optimized for a slightly smaller area than the cab is.

How did you select the new drivers?? It not as simple a picking some 10" driver or another and installing them into a cabinet.
Please read the FAQ atop page one.

[MuthaFunk]

Originally Posted by BassmanPaul

How did you select the new drivers?? It not as simple a picking some 10" driver or another and installing them into a cabinet.
Please read the FAQ atop page one.

I picked them on their price and fit for my application. The Traynor cab is not worth a lot of $ so I couldn't get carried away. Eminence does make a "perfect" driver (CA2010) to fit this cab but they're $100 ea. I'd need 6 of them and it's just not worth it to try. The Alpha 10A's on the other hand are $44.95 ea. and are very close spec wise.

I looked up in the FAQ but I didn't see anything to do with cabinet fill or speaker selection. Link please?

[kb9wyz]

Originally Posted by JSK5String

Thanks for the kind words, they are appreciated...

You deserve many more kind words. I wish I had them for you. But I'm too busy drooling at the beautiful thing you made to find any.