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Really no insulation in my big 3620!

Discussion in 'Amps and Cabs [BG]' started by hrgiger, Mar 10, 2009.


  1. hrgiger

    hrgiger

    Jan 11, 2009
    I was reading about insulation and I decided to look inside my 3620 cab and I found some interesting things. This thing is partitioned off into 3 separate cabs. There is a sealed top part with 2 10s (no insulation), and 2 equally separate ported areas in the bottom for each 18 (also no insulation.) I knew that the top was a sealed separate area, but I had assumed that the 2 18s were in the same enclosure (though now that I think about it the 2 ports were a little suspicious, though a 215 cab I had also had 2 ports but was not 2 fully isolated areas inside.)

    Anyway, I guess I need to get this thing insulated up! I am going to line all areas of the bottom with egg crate mattress foam, but how should I stuff the top, sealed area? I have not seen any specifics on this...

    3311022332_12372e09a0.

    To the left you see the baffle blocking the 2 10s which the red and black wires go to.
    3345961540_078c96eaa1_o.
     
  2. Sundogue

    Sundogue

    Apr 26, 2001
    Wausau, WI
    I don't know if the 18's area needs any foam as I'm sure they aren't producing much in the way of mids (which is what the foam is meant to control).

    With the 10's being sealed, I'd think if you stuffed their area completely with cotton batting loosely, they'd sound a bit bigger.

    I'd be interested in hearing what the experts have to say about this.
     
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Line everything. The ports on the 18s are about 1/4 the area they should be to prevent chuffing. All in all a very poorly engineered cab.
     
  4. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    There's still midrange bouncing around in there, especially with a lower-order crossover, and there's also harmonic distortion produced by the drivers themselves that's created as a byproduct, an octave and up - above what the actual signal contains.
     
  5. my back is screaming just thinking about that cab. i had the 1820 and that was hernia inducing enough. good luck with the lining.
     
  6. hrgiger

    hrgiger

    Jan 11, 2009
    I thought port size was set around tuned frequency? Or are these not tuned ports since there is no tube?
     
  7. hrgiger

    hrgiger

    Jan 11, 2009
    Have a question about the floor of the top 18's area. It has some bracing and I was wondering since the port is involved in this area, should I pad it up as shown, or does the port need this area to be free of foam?

    3347742407_3886235af0.

    3347742403_70de44aef0.
     
  8. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    They are.
    The 'tube' is a duct, which allows the area of the port to be large enough so that the air passing through the port won't create chuffing noise. In this case no ducts results in port areas so small that chuffing is inevitable. The port must be free to breathe, don't put foam over it.
     
  9. hrgiger

    hrgiger

    Jan 11, 2009
    What about mildly radiusing the inner lip of the port? I've read that can help alleviate chuffing...
     
  10. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    In this case like applying a band-aid to a broken arm.
     
  11. hrgiger

    hrgiger

    Jan 11, 2009
    Thanks for your help, I'll speak with some other people I know...
     
  12. eots

    eots

    Dec 18, 2004
    Morris, IL.
    I had the 1516 used with a GK800rb. I thought it sounded like butt. Makes me wish I held on to the GK to try with other cabs.
     
  13. Rock-Bassman

    Rock-Bassman

    Dec 25, 2008
    Boston
    I use a 1820 and mine has none in there either!!! Man the 1820 is HEAVY. I don't want to think about the 3620
     
  14. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    If they know anything about loudspeaker design they'll say the same thing. To remove the possibility of chuffing the port area must be a minimum of 1/3 the cone area. With an 18 that means a port area of at least 60 square inches per driver. A duct of the correct length would then be required to properly tune the cab.
     
  15. hrgiger

    hrgiger

    Jan 11, 2009
    Well time to get it lined up inside! Come on these things have wheels! Besides bass is not for wimps... :bag:
     
  16. hrgiger

    hrgiger

    Jan 11, 2009
    Well now that's better, I filled the top section with poly batting (used one bag and a handful of a second bag) and lined the bottom 2 sections with mattress topper foam. Haven't had much time to try it out yet, but so far it seems much more 'solid' sounding. Now it's on to a little bit of appearance refurbishing...

    3350120207_f78317a183.
     
  17. eots

    eots

    Dec 18, 2004
    Morris, IL.
    If only you could leave it sit. Moving it is why it takes it's lumps
     
  18. hrgiger

    hrgiger

    Jan 11, 2009
    Yeah, well, I agree on that. Also a paintbrush and spray paint didn't do the grill any good, got some mojo cloth on the way...
     
  19. gerryjazzman

    gerryjazzman Supporting Member

    Dec 31, 2006
    New Jersey
    Very interesting. I recently gave someone else a suggestion to check to see if his cab was padded based on my experience of finding out that my old TNT160 had none. I wasn't sure if it was just poor quality control or if Peavey was cutting corners. It looks more like it was the latter. :eyebrow: I'd venture to say that this might be going on with some other cost conscious manufacturers as well. Might be a good idea in general to pop a speaker and have a peek inside if one is not satisfied with their sound.
     
  20. Rock-Bassman

    Rock-Bassman

    Dec 25, 2008
    Boston
    Hey now, I got mine used and no wheels. I'm 16 and ya know what, I'm not that strong (not to say I couldn't hit a baseball 300ft :p) And no roadies (again, small band, only a few gigs.)
    I don't take any offense by the way ;) Cause ya know what really hurts? 75 mph fastballs that hit ya in the chest whn you catch... Ugh!
     

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