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GK 410MBE Mods

Discussion in 'Amps [BG]' started by gmarcus, Jul 2, 2011.

  1. gmarcus

    gmarcus Supporting Member

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    I've had this cabinet at rehearsal with my quiet rootsy folksy band for a few months and just love the full range sound at low volumes. Last night I had it out in a big room with a much louder band. When I turned it up it definitely started to sound a little blatty and less controlled. It was shaking the walls, but seemed a little loose if that makes any sense.

    I heard that there is no stuffing in these acoustic suspension (sealed) cabinets. Being an engineer I had to see for my self. So I took off the grill and popped out one of the speakers. It was in there pretty tight with some kind of a sealing compound, so I had to use a plastic spatula to pry it out. I take this as a good sign because sealed cabinets are supposed to be....well...sealed.

    I was surprised at just how nice the speaker looked (see photo). It looks quite a bit like an Eminence deltalite. the internal construction looks solid, definitely ply wood, 7/8" front baffle and 1/2" braces inside. The braces run front to back and kind of divide the cabinet into 4 sub boxes (one for each speaker). All of them are open in the middle.

    I ordered 3 lbs of acousta-stuff to stuff the cabinet. I also bought a set of 3/4" tall rubber feet so I can set this on top of my other cabinet (Schroeder 1515L). The GK and the Schroeder sound great together but the corners don't line up at all. I was thinking about side handles, but the strap on top is all I really need.

    I'll let you know how it sounds with the stuffing. It should tighten up the bass a lot.

    Attached Files:

  2. rovito

    rovito

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    Subscribed!
  3. tallboybass

    tallboybass Supporting Member Supporting Member

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    Yes, let us know how it responds to the stuffing!
  4. Matthew_84

    Matthew_84

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    Make sure to stuff her good, lol :cool:

    I still have't gotten the beast yet... Should be in the next week or two, but am very curios to hear the outcome.
  5. billfitzmaurice

    billfitzmaurice

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    Owner, Bill Fitzmaurice Loudspeaker Design
    They aren't acoustic suspension. All acoustic suspension cabs are sealed, but most sealed cabs are not acoustic suspension. No musical instrument cabs are, or ever have been, acoustic suspension, as the drivers used in acoustic suspension have far too low sensitivity.
    As for stuffing the cab, that may not work well. Depending on the driver specs it may be appropriate, but it also may not. It should be lined, but as for stuffing, add it gradually.
  6. gmarcus

    gmarcus Supporting Member

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    Bill are you saying that these are infinite baffle? How does stuffing effect this? Oh well I can always remove the stuffing,
  7. billfitzmaurice

    billfitzmaurice

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    Yes. All sealed cabs are infinite baffle, as are all acoustic suspension.
    It lowers the cab Q, which is quite beneficial if the Q is too high, detrimental if it isn't. That's totally different from lining it with damping, which is a necessity with all cabs to prevent boomy response from standing wave development and erratic midrange from internal midrange reflections.
  8. gmarcus

    gmarcus Supporting Member

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    Bill

    Thanks for the insight! You have a lot more experience with this than i do and i really value your thoughts. I am hoping to lower the Q to tighten up the bass a little bit. My biggest concern is that this might also lower the efficiency and power handling. I assume GK designed these to maximize both. I realize that lowering the Q will reduce the mid bass bump but are there any other effects in addition this and the reduction to standing waves and reflections?

    Thanks for the advice!
  9. gmarcus

    gmarcus Supporting Member

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    Matthew and Tallboybass

    The stuffing should be here sometime this week I'll let you know how it turns out. Sounds like I will have to use just the right amount to tune the cabinet. I'm sure my neighbors will love the high volume testing phase ;-). I don't have any way to record this well or take any measurements so the best I can do is say how many bags of stuffing it takes to make the cabinet sound good to my ears.
  10. JonnyAngle

    JonnyAngle Supporting Member

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    While you have three drivers out, you should add a side handle. It's much easier to carry!
  11. gmarcus

    gmarcus Supporting Member

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    Just pulled the trigger on a pair of handles. Might as well pimp this out
  12. gmarcus

    gmarcus Supporting Member

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    Oops I just brought the cab to practice again. We had the drummer, 2 electric guitars, keys, trumpet and 2 singers. I set my Shuttle 6.0 almost all at noon. Mid at 12:30 mid frequent at ~ 150 hz. All shape controls off. It sat perfectly in the mix!

    Hmmmmm I'll probably still add some stuffing but not too much.
  13. gmarcus

    gmarcus Supporting Member

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    Okay so the stuffing arrived and I couldn't help my self so I popped out one woofer and stuffed the whole 3 lbs in through that one hole. I really didn't want to remove all of the speakers. I'm also bagging on the handles. I'm just not that motivated to cut two big holes in a nice cabinet.

    So it did tighten up the bass, but I'm just playing it in this funky little basement. I have another practice with the loud band a week from Monday. I'll report back how it sounds after that. Honestly it doesn't sound that much different. It's kind of like I turned the low boost off on my shuttle compared to before I stuffed it but not as drastic. Now it sounds tight with the low boost on which I believe is just setting the low roll off of the amp lower. Before I stuffed the cabinet turning off the low boost (= engaging a low cut filter) compensated for the boomyness of the cabinet. Now I just run the amp wide open (= lowboost on ) and it sounds balanced. If I turn the Lowe boost off it sounds kind of thin.
  14. Matthew_84

    Matthew_84

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    Interesting... Looking forward to what you discover. Thanks for posting this
  15. billfitzmaurice

    billfitzmaurice

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    Owner, Bill Fitzmaurice Loudspeaker Design
    Stuffing lowers Q. Too high a Q gives a midbass response bump that makes the cab sound louder, but also leads to boom. Lowering Q reduces the boom, but also reduces perceived loudness. Finding the best balance is easy with measurement tools, but by ear could take a fair amount of experimentation.
  16. garagebassman

    garagebassman

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    speaking of the "trial and error' method of cab lining/insulating, would there be a noticeable difference between one or two layers of 1" polyester batting in a ported 212 cab ?
  17. billfitzmaurice

    billfitzmaurice

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    Impossible to say, as there are other variables involved. If the cab isn't boomy with an inch then more probably would be of no benefit. If it is boomy with an inch then more probably would be better.
  18. garagebassman

    garagebassman

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    if the 2nd inch creates no benefit, is there a specific (predicted or expected) downside to having the extra inch there ?
    thx
  19. gmarcus

    gmarcus Supporting Member

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    I used the cab at practice tonight with a VT bass pedal as a preamp directly into the effects loop return of a shuttle 6.0. So the VT was my preamp and the Shuttle was my 350 watt class d power amp. The stuffing definitely tightened up the sound in a very good way. The VT bass used to make this cabinet sound boomy with the SVT setting. Now it sounds full, but tight. It is articulate but you get a sense that there is some deep bass going on and you can feel it in your chest. I played it with a 5 string p-bass with flats and is had a lot of growl.

    My friend used it with another band in the same large auditorium. He used a beautiful 1966 Gibson Thunderbird with very old flats. It was fat and beautiful. They played some Cream and he sounded like Jack Bruce. He was using the VT bass with a catalinabread WIIO which simulates a Highwatt and a bass big muff all at the same time.

    I'm happy with this mod it tightens the sound just enough. If I was more motivated I might take some of the stuffing out to fatten the sound a little bit, but honestly in a band it sounds really good. It just might be a little better with a slightly higher Q. My guess is that 2 lbs of stuffing would be perfect. I used 3 lbs. I just don't have the time to pull the speakers right now. It is definitely gig worthy now.

    Tomorrow we have an outdoor gig with both bands. I'm going to pair it up with my Schroeder 1515L and GK1001RBII. We will use the same pedal board described above. I'll let you know how it sounds after the gig.
  20. billfitzmaurice

    billfitzmaurice

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    If you overdamp you'll lose some midbass sensitivity. In hi-fi, where listeners are far more critical, there's no agreement as to the best Q of a speaker. 0.7 is the accepted compromise figure, but personal preference can run from 0.6 to 0.9, and room interactions also affect the final result, so the answer to how much is too much is a very firm it depends.

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