So I built my own 4x10 ...

Discussion in 'Amps and Cabs [BG]' started by bassguitar, May 31, 2005.

  1. .. and it's ok at low volumes, but if I turn it up past about 5 on my xs800H it totally farts out, the speakers are really dancing, and it's not nearly loud enough to compete with my band - loud drummer and 2 marshall stacks. Beside an xs400 combo (with one 15") it's 1/2 the volume.

    I know some guys had said the speakers in the baffle weren't lined up well enough and that I should line the up totally horizontally. Will replacing the baffle make that much of a difference?

    BTW - they're eminence bp102 drivers wired series/paralell @ 8 ohms.

    Attached Files:

  2. dr_love2112


    May 28, 2005
    baytown texas
    well it might but not that much, but you could also get 4 ohm speakers and it will be alot louder

    if you amp puts out 400 watts @ 4 ohms
    thats 200 watts (about) @ 8 ohms

    so the less the ohms in the speakers the louder!!!!! :hyper:
  3. It's 800 watts - not sure what it is exactly at 8 ohms, but I think it's around 600?
  4. The alignment of your drivers will have a significant impact on your tone, maybe volume too.

    When using multiple speakers to produce the same range of frequencies they should be placed as close trogether as possible and a vertical alignment is also helpful. The most important thing is having the centers close together. The farther aprt they are the more phase problems and comb filtering effects are introduced at lower frequencies. I'm surprised to hear they are farting out but not too surprised it isn't really loud with those drivers. That's the price you pay for speakers capable of good low end which these seem to be. Still, you should be able to get plenty of vulume with 600watts.

    I would line them up like this if they won't all go vertical.

  5. Petebass


    Dec 22, 2002
    QLD Australia
    I agree that the speaker placement could also be revised. But the larger problem is the drivers.

    With currnt technology, it's a case of "Loud, Low, small, pick any 2". Those BP102's are 10"(small), and go right down to 40Hz(Low). Loud loses out.
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Where are the ducts? Are they in back or do you not have any? With the very low Qts of those drivers they will not put out any real bottom end in a sealed box.

    A vertical alignment is a must. Don't take advise from anyone who's telling you to have the drivers side by side. That's cosmetically correct, sonically incorrect.

    'so the less the ohms in the speakers the louder'

    This only applies if you have an amp that's too small to drive the speaker to full power, and the farting out doesn't indicate that this is the case.

    "Loud, Low, small, pick any 2".

    True, Pete, but that applies to the cabinet size, not the driver size. I suspect the box size here is just too small, and if it's a sealed cab I can almost guarantee it.

    I'd go back to WinISD and model out what you have, and then see what alterations you need to make to push up the response in the critical 60 to 100 Hz band. If the program says you can't get at least another 3dB there with a better box or even two boxes then it's time to think about different drivers.
  7. Petebass


    Dec 22, 2002
    QLD Australia
    It applies to driver size! Case in point, a 10" sub in an small automobile or home theatre cab produces more bottom end than a 10" designed for Pro Audio. It does so via very low sensitivity.
  8. BassikLee

    BassikLee Supporting Member Commercial User

    Feb 13, 2004
    Deltona, FL
    Owner: Brevard Sound Systems
    Then a ran the driver using winisd. It suggest, for four of the BP102, a sealed box of 6.63ft3, with a -3dB point of 61.34hz. The EBP of that driver is 80, which leans more toward the vented side of the equation than the sealed, so I ran it in a vented box. There, it calls for 13.9ft3, tuned to 34.97Hz, with a -3dB of 32Hz. On the surface, 13' seems pretty big, and it is by today's standards. Your box loox to me like an SVT with poor dental hygiene. If I recall, those SVTs were like 48x27x16. After losing the thickness of all the walls, and the fact that the baffle is back about an inch, I get roughly 9' for your box. I plugged 9' into winisd, and it kicked out a -3dB point of about 40Hz, with porting as follows: if you go with 4 three inch ports, that are 4.6" deep, you should be in the ballpark. Me, I'd have used a more efficient driver to start with, as that one is only 91dB.
  9. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    What you're referring to is the general trade off between SPL and fs. With fs primarily being a function of mms a lower fs will equal a lower SPL if all the other specs are equal. But that doesn't mean that you can't get both a low extension and a high sensitivity from a small driver with moderate sensitivity. My T24 gets a higher sensitivity and lower extension than the average direct radiating 15 with an Eminence HL10a, and a Labhorn gets both lower extension and higher SPL from a Eminence Lab 12 than the the average direct radiating dual 18. How? With a larger box. And a few other tricks. But it can be done.

    Driver size in and of itself would be a limiting factor if all the other specs, such as fs, Qts, Qes, Qms, and xmax to name only a few, were the same between the larger and smaller driver. But if the area of the cone of driver A is twice the area of driver B that's instantly negated if driver B has twice the xmax of driver A.

    Model an average ten in a 4 cu.ft box and similarly spec'd fifteen in a two cubic foot box. The ten will outpush the fifteen. Run a sim on any driver and see what happens to response when you take the box size to less than optimal. Driver size does entail limitations, but cabinet size is the defining factor when it comes to extension versus sensitivity.
  10. It's ported at the back - 4.5x4.5x2.5.

    I can't remember the exact dimensions of the box, but the outside dimensions are around 48*28*18. The material is 3/4" thick.

    I've also put batting on all the inside walls.

    A few more ports eh?
  11. Steve


    Aug 10, 2001
    Nor will it ever be. Not any 4x10. 4 ten inch bass speakers against...what 8 twelves worth of Marshall AND Keith Moon? Or is that 16 twelve's and Keith Moon?

    Seal that box and add 4 more speakers then build another one and put it right next to it.
  12. BruceWane


    Oct 31, 2002
    Houston, TX
    Yep, he's right. The only chance you've got of getting adequate volume for that situation, with just that cab, is to seriously cut your low frequencies and crank up the amp. Your tone will suffer, but you will be able to hear yourself. At least until you go deaf.

    Even if you had the gear to pump low frequencies at high volume, you'd probably find that it's counter-productive to the band practicing. It gets so loud that you can't really hear anything. Your practices will be much more productive if the entire band learns to play at a volume that is as low as possible. The whole point of a band practicing together is to learn to play well together. Turn it down and you'll be able to hear everything much more clearly. Also, low stage volume is a huge plus when playing live. It's a lot easier to mix the PA system, and the club owners will be a lot happier not having to deal with noise complaints.
  13. I'm thinking about buying a 115 to go along with this. Any suggestions? What ohm rating should it be if the 4x10 is 8 ohms?

    Sorry for so many questions, but I am new to this.

    Tip for next time: just friggin buy one.
  14. Steve


    Aug 10, 2001
    Ok then. Let's try it this way...

    Exactly how fast would you like to go deaf so we know how to help you ruin whatever fun music may bring you in this life?

    You know what the worst part is about being a deaf musician? It's how huge of a pain in the butt you are to the guys you play with that aren't deaf.

    A 4x10 cab...even a poorly designed one (NOT THAT YOUR'S IS..)
    will get you loud enough to hurt yourself.

    Save yourself a ton of money and two tons of grief....tell your boy's to turn the eff down.
  15. Funkengrooven

    Funkengrooven Turn it down? You gotta be nuts!!

    IMHO I would have made the cabinet much smaller and done away with the ports entirely.
    Maybe 24w x 24h x 10d
    All other things being equal and assuming that the speakers are ok for the application, a smaller cabinet has less air that can be compressed making a tighter responding cabinet.
    The more air inside the cabinet the greater the excursion of the speaker cones resulting in a flabby sound and less power handling.
    Generally speaking you can drive the hell out of a speaker if you limit the cone movement. just don't forget that the voice coil's have a finite power limit and you will blow them up real good if you contimously exceed that limit. if you exceed the limit on the peaks you will give the coil time to recover and dissipate the heat.
    just an observation from an old guy.
  16. BruceWane


    Oct 31, 2002
    Houston, TX
    It should be 8 ohms as well. Hook it up parallel with your 8 ohm 4x10, and you'll have a total load of 4 ohms. That will allow your amp to put out a bit more wattage; that, along with the added output of the second cabinet, will get you a decent bump in volume.

    But you do need to seriously look at your band's overall volume. Aside from preserving your own hearing, you can get a hell of a lot of gigs just by playing at a level that is comfortable to the average person. ANY band can play loud. But there's all kinds of bars and restaurants that want entertainment that isn't totally obtrusive.
  17. I totally hear you about the volume level. It's loud, but it's not obscene. What I'm comparing the level to is an xs400 combo with a single 15". It puts out twice the volume level as my cab and xs800 head. I run the xs400 at about 5. Not killing it by any means. When I put my rig to 5 it's 1/2 the volume, and by about 6.5 the speakers start to really fart and vibrate.

    I would think I should be able to get a comparable volume with the 4x10 and an amp twice the power.
  18. The Clap

    The Clap

    Jan 5, 2004
    Scottsdale, AZ
    The speakers you're using have a low sensitivity. Each driver is 3-5db less efficient than eminence's other 10" speakers, and since they can't handle a ton of power, the BP102s will never get THAT loud. You can try to re-engineer your box but you've got a system there with an efficiency of about 97db/1W/1M with those 4 10s working, whereas if you're going for loudness, a loud 410 should be about 4-6db more efficient overall.

    You're going to have to put at least double the power into your 410 as you would for another cab of comparable speaker cone area to compensate for this lack of efficiency.

    I've got a 15" speakers that's more efficient than your 410 as well, and you'll probably have to chalk this one up as a learning experience or convert it into a practice amp. Your speakers could be farting out for a variety of reasons apart from the inherent sensitivity restrictions though;
    -An unsealed joint where air is escaping from (other than the port)
    -Too big of a box
    -Incorrect porting
  19. BruceWane


    Oct 31, 2002
    Houston, TX
    Yeah, your box is awfully big.

    Going strictly by the basic thiele-small parameters of the BP102's, that box is about the right size - it gives a very nice frequency response curve. But in the real world, you have to consider a lot more than frequency response.

    The problem with your big box is that it doesn't give enough resistance to the motion of the cones. That's why it's farting out so easily.

    A smaller box yields better cone control because the air volume inside it is smaller, and thus harder to compress. Of course, the tuning of the port(s) come into play also, but basically, smaller cab = tighter cone control.

    Without getting into too many details, I'd say Funkengrooven has it about right. A sealed cab with internal dimensions of about 22" x 22" x 10" will keep your speakers from complaining up to about 400-500 watts. You'll lose some low end, but there's always a trade-off.

    These speakers would do a little better in a ported cab, but it would be a little more complicated design. The problem you run into when designing a small ported cab is that it gets difficult to fit the neccessary port within the cabinet. For instance, these speakers look pretty good in a 22" x 24" x 10" (internal) cab tuned to around 40Hz. The problem now is building the port. You have to have enough port area so that it doesn't make noise from the air rushing in and out - you don't want "chuffing". And the larger the port area, the longer the port must be. You could use 2 4" ID round ports that are each 14" long......but this cab is only 10" deep. So you'd have to put a 90 degree bend in them. Not terribly difficult, just use PVC pipe from Home Depot or Lowe's. This effort gets you a little bit more low end and power handling over the sealed box, but I don't know that it'd be worth the effort. I've done these kind of ports before, so it'd be no big deal to me, but if you haven't, you might just go with the simpler sealed box.

    Either of these boxes should maintain their composure pretty well up to 400 watts or so, even if you tune down to D or play a 5 string. But neither is going to have a great deal of low end.
  20. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Many interesting opinions, some of them valid, some off the wall. But all interesting.

    Your cab is in the vicinity of 10 cu. ft., net. I can't tell from your description about the ports exactly what you have. The way you wrote it it seems like about 30 square inches with no ducts. If that's the case the box is tuned to about 40Hz. That would be fine if this is a hi-fi box and you're trying for the flattest possible response. It isn't and you aren't.

    From a ten cu. ft. box with these drivers you'll get the best response for electric bass tuning the box to about 55 Hz. That will give you a 6dB response bump around 65Hz, with a resulting SPL of 102dB/watt at that frequency, right in the middle of the electric bass power band. If your ports aren't ducted that means an area of about 90 square inches, three times what you have now as best as I can tell. Your f3 will go from about 38 Hz to about 48 Hz, but that's of no consequence. Your peak power demands are an octave higher than that.

    Sealed boxes do help limit excursion, but when they limit it so much that you have no sensitivity they hurt performance, not enhance it. Your present box sealed would give an SPL of only 94dB/watt at 65 Hz, 8dB down from what my proposed vented option would give, and 4dB down from what you have now.