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Built a cabinet similar to a fEARful that is distorting

Discussion in 'Amps and Cabs [BG]' started by Willie5String, Apr 18, 2021.


  1. Willie5String

    Willie5String

    Dec 23, 2018
    Cabinet sounds great at low volumes but when it gets louder the below notes distort.

    Anyone suggest some troubleshooting ideas?
     
  2. Redbrangus

    Redbrangus Supporting Member

    Nov 19, 2018
    Under The X In Texas
    Which cab in particular? Did you use the specified Eminence driver?
     
  3. Foz

    Foz

    Jul 26, 2008
    Jax FL USA
    check crimps and solder joints
     
  4. wcriley

    wcriley

    Apr 5, 2010
    Western PA
    Define "similar".
     
  5. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Similar may in fact be totally different in critical details.
     
  6. Willie5String

    Willie5String

    Dec 23, 2018
    I’ll post all particulars shortly
     
  7. Willie5String

    Willie5String

    Dec 23, 2018
    Woofer Dayton 15” PN 395-8
    Mid Eminence Alpha 8 MRA (closed back)
    Tweeter Selenium DT 150 (a horn tweeter)
    Cross over Eminence PXB 3:3K5
    18”x2” 6.5” deep slotted port

    Cabinet 1/2” marine plywood reinforced with 3/4”x3/4” pine in an x pattern on all inner walls (screwed and glued in)

    Cabinet dimensions 23”x20”x16”

    Powering with a 200 watt (@8 ohm) B200 amp that sounds fine with its current enclosure which is a single 15” 8 ohm speaker.

    New cabinet sounds really good at lower volumes but woofer is distorting when it gets louder (not real loud, I could probably yell over it at the volume level it starts distorting at)

    Thanks for any suggestions given
     
  8. Foz

    Foz

    Jul 26, 2008
    Jax FL USA
    also check to make sure speaker coil leads aren't rubbing against the cone
     
    mcnach and MTN.bass72 like this.
  9. mapleglo

    mapleglo Gold Supporting Member

    Sep 7, 2013
    phoenix, az
    I think the first problem is that the Dayton 395-8 calls for a 1.6 cubic foot optimum vented cabinet, while you have it in a 4.3 cubic foot cabinet.
     
  10. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    How is this like a Fearful again?
     
  11. Thundar

    Thundar The other ones are complete bull$hit Supporting Member

  12. sawzalot

    sawzalot Supporting Member

    Oct 18, 2007
    Is this an Acoustic B200 combo amp?

    The first thing I’d do is try the cab with a different power amp and see if you still hear it distorting. If so you can reliably assume it’s something in the cab. Otherwise it’s something else in your signal chain, and if the only thing different is the amp, then I would suspect the amp rather than the cab. The B200, according to the specs I see, is capable of 200w into 4 ohms, not 8. That’s maybe not a lot of power for bass, depending on your eq settings.

    if it still distorts with a different amp, I’d maybe look for rattles/etc in the physical construction of the amp. 1/2” marine plywood isn’t guaranteed to be void free and, because it’s made with pine or other softwoods, may have knots/etc that conceivably could be rattling around inside the plies of the wood. Also, you didn’t mention the joinery of the cabinet walls to each other or how the vent is constructed. So a little more of that kind of info could help.
     
  13. Redbrangus

    Redbrangus Supporting Member

    Nov 19, 2018
    Under The X In Texas
    I'm only coming up with about 3.5 cu. ft., but your observation is on point.

    Edit:
    Qts: Dayton = .35 -- 3015LF = .46
    Xmax: Dayton = 6.5mm -- 3015LF = 9.6mm
     
    Last edited: Apr 18, 2021
  14. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    What’s the crossover freq to the mid driver?
     
  15. Willie5String

    Willie5String

    Dec 23, 2018
    I believe the cross over to the mid is 800 hz
     
  16. Redbrangus

    Redbrangus Supporting Member

    Nov 19, 2018
    Under The X In Texas
    I'm coming up with an approximate net internal volume for your box as 3.5 cu. ft, after deducting 234 cu. in. for the vent volume. The Fearful 15/6 has about 4.2 cu. ft. net internal volume with a vent volume of 513 cu. in. And you used a substantially different LF driver. Making @agedhorse's initial comment all the more relevant: how is this like a Fearful again?
     
    Last edited: Apr 18, 2021
    dan1952 and wcriley like this.
  17. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    The crossover you listed is only a 3.5kHz high pass filter for the tweeter.

    How is the mid driver crossed over again?
     
    dan1952 likes this.
  18. Redbrangus

    Redbrangus Supporting Member

    Nov 19, 2018
    Under The X In Texas
    There's a screw-up in the Parts Express part numbers, if that's what you're referencing. The Eminence PXB3:3K5 is the part number for a 3-way network, with 500 and 3K crossover points.

    Edit: PXB3:3K5 spec
    Crossover Frequency: 500 Hz/3.5 kHz
    Slope: 12dB/octave LP, 6dB/octave MP, 18dB/octave HP Butterworth
    Impedance: 8 ohms
    Power Handling: 400W

    500 Hz crossover point, single-pole, 6dB slope for MF driver...? You might be on to something, @agedhorse.
     
    Last edited: Apr 18, 2021
    yodedude2 likes this.
  19. nutdog

    nutdog when I'm a good dog they sometimes throw me a bone

    Feb 19, 2009
    in the dog house
    word
     
  20. Willie5String

    Willie5String

    Dec 23, 2018
    Thanks yes, crossed over at 3,000 hz and 500 hz. Parts express recommends the 3.6 cu ft size box when ported.

    I realize that similar is not exact.

    The box is designed using good specs as far as I can see from online software.

    I’d really like the help that I know this group of very experienced people can offer, I’ve build several cabinets in the past that have worked well, so my debug skills aren’t the best.
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    May 6, 2021

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