Cabinet construction started - additional absorbent internal layers?

quickshift · 25th February 2007, 05:58 PM

Hello

Not a very good thread title. Sorry.

I'm part way through making some more curved speakers. I've got as far as building an MDF frame, skinning it with bendy MDF and layering up some fibreglass and sand mixed with polyester resin. So far so good, they are fairly dead and there isn’t a lot of chance of them flexing much at all thanks to 5KG of resin, 4 layers of thick matting and ½ bag of sand in each.

However, I want to do as much as possible to reduce cabinet resonance so was wondering if it's advisable to put in a soft layer, I was thinking about something like upholstery foam, with another couple of layers of fibreglass on top?

Good idea or not worth bothering?
Is there anything better to use / do?

badman · 26th February 2007, 02:48 PM

Yes, it's a good idea, as long as you can compress the soft layer effectively- it'd be a shame to add the extra layer just to have it start resonating from the stimulus of the output from the speaker.

Pit Hinder · 26th February 2007, 04:53 PM

Quickshift,
"more curved" got my attention. It means you can get the horn to support the upper bass/lower mids a low Q driver can't do alone - but it doesn't attenuate unwanted midrange smut. Calculate the standing wave that might build up in your cab's width. Hanging a layer of felt in the middle of your horns ("hanging" means it halves the width, you look at the edge of it - s**t, I couldn't even explain it in German without using my hands) might be a good idea. Anyway, whatever you do - keep one side panel unglued until you are really happy. There is nothing as

as "I ought to have tried that"

Cheers,
Pit

quickshift · 26th February 2007, 04:56 PM

OK, thank you badman

I'll incorporate some foam.

I'm not sure how I'd compress it though. I'll have a think on it.

quickshift · 26th February 2007, 05:16 PM

I understood perfectly pit

I'm not building horns though, just simple sealed boxes for some woofers.

There is nothing as as "I ought to have tried that"

And nothing as

as "I wish I hadn't tried that"

Pit Hinder · 26th February 2007, 05:58 PM

Quote:

[i]And nothing as

as "I wish I hadn't tried that"

[/B]

Oi, what you think you're saying? What about the bird your mate got on with and the boxes you didn't try?

Pit

quickshift · 26th February 2007, 06:54 PM

A good point well made

I was remembering the time I spent about an hour removing contact adhesive from some speakers I'd botched a veneering job on using petrol and a chisel

A very

moment

Pit Hinder · 26th February 2007, 07:42 PM

Ermm...*polite cough*...were there any planes or 90° left when you were done?

Pit

quickshift · 26th February 2007, 08:08 PM

Yeah - it all came good in the end - luckily I'd soaked the outer layer of hardboard with Bonda wood hardener so it wasn't as bad as it could have been - tough stuff Bonda...

The adhesive came off with only a couple of scrapes. Nothing filler didn't cure.

Today I have been considering if I should have another go

The speakers curve in 2 planes but I reckon if I damp the veneer and form it round the speakers for a day or so before letting glue anywhere near them... it may just work...

25th February 2007, 05:58 PM	#1
quickshift diyAudio Member Join Date: Jun 2005 Location: West London	Cabinet construction started - additional absorbent internal layers? Hello Not a very good thread title. Sorry. I'm part way through making some more curved speakers. I've got as far as building an MDF frame, skinning it with bendy MDF and layering up some fibreglass and sand mixed with polyester resin. So far so good, they are fairly dead and there isn’t a lot of chance of them flexing much at all thanks to 5KG of resin, 4 layers of thick matting and ½ bag of sand in each. However, I want to do as much as possible to reduce cabinet resonance so was wondering if it's advisable to put in a soft layer, I was thinking about something like upholstery foam, with another couple of layers of fibreglass on top? Good idea or not worth bothering? Is there anything better to use / do?

26th February 2007, 02:48 PM	#2
badman Custom Title diyAudio Member Join Date: Sep 2003 Location: Sunny Tustin, SoCal	Yes, it's a good idea, as long as you can compress the soft layer effectively- it'd be a shame to add the extra layer just to have it start resonating from the stimulus of the output from the speaker. __________________ I write for www.enjoythemusic.com in the DIY section. You may find yourself getting a preview of a project in-progress. Be warned!

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26th February 2007, 04:53 PM	#3
Pit Hinder diyAudio Member Join Date: Nov 2006 Location: Hannover, Germany	Quickshift, "more curved" got my attention. It means you can get the horn to support the upper bass/lower mids a low Q driver can't do alone - but it doesn't attenuate unwanted midrange smut. Calculate the standing wave that might build up in your cab's width. Hanging a layer of felt in the middle of your horns ("hanging" means it halves the width, you look at the edge of it - s**t, I couldn't even explain it in German without using my hands) might be a good idea. Anyway, whatever you do - keep one side panel unglued until you are really happy. There is nothing as as "I ought to have tried that" Cheers, Pit

26th February 2007, 04:56 PM	#4
quickshift diyAudio Member Join Date: Jun 2005 Location: West London	OK, thank you badman I'll incorporate some foam. I'm not sure how I'd compress it though. I'll have a think on it.

26th February 2007, 05:16 PM	#5
quickshift diyAudio Member Join Date: Jun 2005 Location: West London	I understood perfectly pit I'm not building horns though, just simple sealed boxes for some woofers. There is nothing as as "I ought to have tried that" And nothing as as "I wish I hadn't tried that"

26th February 2007, 06:54 PM	#7
quickshift diyAudio Member Join Date: Jun 2005 Location: West London	A good point well made I was remembering the time I spent about an hour removing contact adhesive from some speakers I'd botched a veneering job on using petrol and a chisel A very moment

26th February 2007, 07:42 PM	#8
Pit Hinder diyAudio Member Join Date: Nov 2006 Location: Hannover, Germany	Ermm...polite cough...were there any planes or 90° left when you were done? Pit

26th February 2007, 08:08 PM	#9
quickshift diyAudio Member Join Date: Jun 2005 Location: West London	Yeah - it all came good in the end - luckily I'd soaked the outer layer of hardboard with Bonda wood hardener so it wasn't as bad as it could have been - tough stuff Bonda... The adhesive came off with only a couple of scrapes. Nothing filler didn't cure. Today I have been considering if I should have another go The speakers curve in 2 planes but I reckon if I damp the veneer and form it round the speakers for a day or so before letting glue anywhere near them... it may just work...

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