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Old 8th January 2003, 11:01 AM   #11
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I lined my cabinets with a sound and temperature insulation that I first saw in an aviation supply and later found in Home Depot being sold as water heater blankets for $20 a 4' X 6' sheet. For more info check out my thread "Isobaric Subs" in the DIY forum at the www.audiokarma.org site. I have misplaced the packing label but the stuff is good at trapping sound, is light weight and less than $1/sq ft.
For internal bracing try the ash dowel used for hanging clothes on. Very strong and round is a good shape to cut through the center of a speaker box.
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Old 8th January 2003, 11:48 AM   #12
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Dave,

Do you have connections on the rear of the receiver for "pre-amp out" and "amp in", connected with a jumper?

Rodd Yamashita
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Old 8th January 2003, 03:41 PM   #13
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I would like to thank Rodd and Greg on their comments. They are very good food for thought.

James
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Old 8th January 2003, 08:41 PM   #14
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Found the packing slip for the insulation. It is made by Quality Heat Shield Sound Deadener (800) 252-7901 in Riverside, Ca.
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Old 9th January 2003, 06:05 AM   #15
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G'day Rodd,

Quote:
Do you have connections on the rear of the receiver for "pre-amp out" and "amp in", connected with a jumper?
No sorry - she's a pretty simple receiver - only high level speaker outputs.... no pre-amp out or anything like that (that was an extra feature on the next model up

Hey - I just realised something. Can I use the tape "rec" (line out)? since the receiver has a tape monitor switch?

Only problem - volume won't vary - since it doesn't go through the preamp.

High level outputs it is then! Will I loose too much sound quality? (I suppose it depends on the quality of the electronics in the plateamp)

BTW - its a redgum RGsw2 (made in australia):
http://www.users.bigpond.net.au/redgumaudio/rgsw2.html

Cheers,
Dave.
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Old 9th January 2003, 06:15 AM   #16
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I forgot to ask...

The plate amp (see the link above) only has a 6dB xover. I think this will be too shallow (as my mains will no doubt have a much steeper rolloff) - I'm afraid the system will "boom" - since I cannot modify the xover to the mains.

Any suggestions?

Thanks,
Dave
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Old 9th January 2003, 09:56 AM   #17
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Dave,

I noticed that the Redgum has only line level inputs. If you have no pre-amp out, what were you planning on using for the inputs to the Redgum?

This is where you would apply your own active xover, but you must again be able to have access to your pre-amp out signal and receiver amp in connections.

You might want to start a new thread in the SS catagory asking how this might be accomplished inside your receiver.

I'll be watching
Rodd Yamashita
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Old 10th January 2003, 03:42 AM   #18
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Thanks Rodd,

Redgum supply a high level plug in board to take the speaker outputs of the receiver - so no problem there.

I might start the new post as suggested. I want to investigate the shallow 6dB rolloff of the sub amplifier - which I will also do as new thread,

David.
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Old 10th January 2003, 09:17 AM   #19
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Default standing waves (from THD or cutoff rate) are not going to be absorbed by the lining

, at least not significantly. The pressure max is at the walls, whereas the volecity max is at some point within the enclosure, depending on the order of the wave.

Damping material is not efficient for pressure, just for velocity. At the frequencies of concern, it would have to be many inches thick to have an effect.
To achieve this end, it should be placed close to the center of the box. I usually use two braces spaced several inches apart which have several large cutouts, cover the cutouts with 5 mm thick wood-felt (the stuff that is meant to go between the concrete floor and whatever surface, i.e. tiles, polished wood, carpet, is on top). Between the braces I stuff rock wool.
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Old 11th January 2003, 07:29 AM   #20
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Capslock,

Are you saying only standing waves cause panel resonance? I thought every panel has some resonance frequency - its own fs if you will.

As such the purpose of bracing is to make each panel smaller - pushing that resonance up in the frequency spectrum - whereas the lining / batting on the walls is to absorb energy that would make it resonate in the first place?

eg - bracing is resonance prevention, damping and lining is resonance cure.

Dave.
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