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Conference napalm::guitar

Title:GUITARnotes - Where Every Note has Emotion
Notice:Discussion of the finer stringed instruments
Moderator:KDX200::COOPER
Created:Thu Aug 14 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:3280
Total number of notes:61432

1544.0. "Insulation in a guitar cabinet?" by CSC32::G_HOUSE (Hooks in you) Mon Oct 30 1989 22:28

    I am refinishing a used Ampeg (V4) 4x12 closed back guitar cabinet.  I
    found layers of fiberglass insulation inside and removed them while I
    recovered the cabinet and put new handles on it and such.
    
    What I'm wondering is whether I need to replace it or not.  What will
    the effect be if I do not replace the insulation.
    
    FWIW, the cabinet is 27x30x14 with a sealed back.  It has 12" CTS
    speakers.
    
    Thanks in advance,
    Greg
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1544.1Stop Rattling AQUA::ROSTSubliminal trip to nowhereTue Oct 31 1989 10:2810
    
    The fibreglass is used for two things.  One is to help prevent rattling
    of the cabinet.  The other is that acoustically, a cabinet stuffed with
    fibreglass supposedly acts like an empty cab of slightly larger
    dimensions.
    
    Radio Shack will sell you a large bag of fibreglass for a couple of
    bucks.  
    
    						Brian
1544.2Sealed cabs should be insulatedSTAR::DONOVANTue Oct 31 1989 14:2220
    I would put some type of insulation in your cabinets.  I neglected to
    put insulation in my cabinets and the result was a noticeable
    distortion....not the good kind.
    
    A recording engineer told me that, in sealed, uninsulated cabs, the sound 
    waves bounce off of the hard wood insides and actually "slam" back into the
    cone of the speaker.  
    
    The speaker driver is trying to move the cone in accordance with the 
    electronic signals it is receiving, and it is forced to compete with
    all of these extraneous "shock waves" that are literally distorting the
    shape of the cone.  The result is low efficiency and lousy sound.
    
    I insulated my cabinets with builder's insulation and the result was
    pretty dramatic.
    
    Hope this helps,
    
    Brian
    Obviouslyu, in open back cabinets, the sound waves can escape.
1544.3Great!CSC32::G_HOUSEHooks in youTue Oct 31 1989 20:257
    Thanks!  I'll definately put it back in (I still have what was in there
    and it's in good condition.
    
    You guys are definately a wealth of information, don't know what I'd do
    without this notesfile.
    
    Greg 
1544.4sealed boxes should beSWAV1::STEWARTThere is no dark side of the moon...Wed Nov 01 1989 02:5414




	Don't forget to either caulk the openings or put in some
	weatherstripping. "Sealed" boxes that leak sometimes produce real
	annoying noises.  This isn't so much a problem with ported (or
	open-back) designs. 





1544.5a second for sealantMARVIN::MACHINWed Nov 01 1989 07:506
    RE .-1
    
    Yes, and a slight leak can act as a one-way valve, so the speaker 
    pumps air into the cabinet and the cone gradually emerges until...
    
    Richard.
1544.6foamimg at the mouthDISCVR::JONEILLWed Dec 06 1989 13:313
    Does the insulation have to be fiber glass or can foam be used as well?
    
                             Jim (who has a lot of foam awaiting an answer)
1544.7I like the foamRAVEN1::BLAIRFan mail from some flounder?Wed Dec 06 1989 16:309
    
    My uneducated opinion is that the best is the foam rubber that has
    the "egg carton" sides.  I faced this side toward the sound.  I really
    don't KNOW if it's better than fiberglas but it LOOKS cool.  The Field
    Service guys often have some on hand.  It is real easy to install - I
    didn't even need staples or glue.  You might check the AUDIO conference
    and ask the audiophiles.
    
    -pat
1544.8OTOA01::ELLACOTTFreddie's RevengeWed Dec 06 1989 18:457
     	IMO foam (the thick stuff) is almost as good... line all sides
    of the cab...if you use fiberglass pack the cab but avoid letting
    it come in contact with the spkr cone
    
    FJE_who_was_once_very_quiet_but_not_any_more
                            
    
1544.9Try it, You'll like it...CSC32::MOLLERNightmare on Sesame StreetThu Dec 07 1989 17:568
	The goal is to stop the sound from bouncing around in the cabinet    
	on the flat surfaces. Foam will work as well as other substances.
	I've used old shag carpeting (it really works) as well as
	fiberglass. Fiberglass is lots cheaper than foam, or pretty
	much any other sound deading padding, hence it's used more
	frequenty. Use the foam, it should work quite well.

								Jens