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B102 DIY cab spec help

Discussion in 'Amps [BG]' started by sifi2112, Feb 12, 2014.

  1. sifi2112

    sifi2112

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    Hi all, I want to build a 110 (home practice cab) & like the idea of just having a single 10" driver. Eminence B102 looks good as I don't have to worry about tweeters/x-overs etc ....

    I have ply / speakon / hardware & even some port, also I was planning on angling the baffle a little unless that's not a good idea.

    Can anyone please advise on approx cab dimensions & port size ?

    Thanks in advance :)
  2. wcriley

    wcriley

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    Uncompensated endorsing user: fEARful
  3. bgavin

    bgavin Supporting Member

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    There are two or more versions of this driver.

    If you use for the T/S data on the Eminence site, understand this is for current production drivers.
    Ditto for the 3015LF and BP102, both have old and current versions.

    They are different.
  4. sifi2112

    sifi2112

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    Thanks for the link ... looks like they offer a few different size cabs but not sure which one to go for ? The ports I have are 3" Dv by 4.5" Lv .. Can I vary my port size as in 'larger cab' states 4 Dv & 2.136 Lv so still use my 3" but shorten the Lv ? Or best to look at 'med sized' which specs a 3" by 2.135" ?

    Also ... what do they mean by 'Use a steep high pass filter set to 40 Hz' ? I understand a hpf will only let the higher freqs thru but how do they expect me to do this ?

    I do play a 5 string & in drop A ... I'm not expecting too much from this cab, just a decent practice volume sound, certainly not gigging spl .....

    Sorry if these questions seem a bit silly but I've never attempted a ported cab before :)
  5. sifi2112

    sifi2112

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    Bump ... any advice re: cab size porting most welcome. I've looked at the Eminence specs but can't say I really understand it ... Guess the lager cab requires less power than the smaller one. I'd rather go smaller but 0.6 cu ft seems too small ?

    What I really need is ...

    h x w x d in inches & (3" dia) port length for decent sound quality for 5 string at practice vol & I would like to angle the baffle so depth at the top will be less than at the base .. any suggestions ?

    Thanks again guys & excuse my ignorance :)
  6. jongor

    jongor Supporting Member

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    Using a HPF set to 40hZ will allow everything above 40hZ to the speaker, anything below that will be attenuated.

    It protects the speaker from receiving frequencies it can't handle well.
  7. sifi2112

    sifi2112

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    HPF ... so basically put something like a Thumpinator before the speaker or use an amp that has a HPF ? (don't believe my Tech21 Landmark 300 does) ... Ok I get that part :)
  8. DukeLeJeune

    DukeLeJeune Only immortal for a limited time Gold Supporting Member

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    The B102 has modest excursion capability, so it's going to fart out a lot sooner than its sibling the BP102. In fact the latter will go about 6 dB louder before fartout, and its parameters are otherwise better suited for low-B, but then the BP102 trades off roughly an octave of top end relative to the B102. And, that wizzer cone gives the B102 good dispersion up top, so its top end energy advantage is better than comparing the curves would imply. So those are the tradeoffs, and it sounds to me like you're aware of them, and have consciously chosen the B102 for the more SPL-limited role of practice cab. Personally I prefer the Basslite 2010, which falls in between the other two in both excursion and top end, but it's also quite a bit more expensive than either.

    Imo the minimum you want for low-B is -6 dB at the first overtone of low-B, which is 62 Hz. For the B102, the internal dimensions I suggest are 9.25" x 11.25" x 14.5"; this is very close to a golden ratio based on the cube root of three. I suggest a port 3" internal diameter by 7.0" long, and the calculated gross internal volume of .89 cubic feet already takes the volume displaced by speaker and port into account so you don't need to worry about that. You'd end up with a tuning frequency of about 48 Hz, which is a little lower than optimum for maximum low end energy, but it helps to stave off fartout, so I think it's a good balance.

    If you want some tiltback, either increase the depth at the bottom and decrease the depth at the top by the same amount to give the needed tiltback, or add sufficiently tall (possibly wooden) feet to the bottom front.

    Best of luck with your project!
  9. sifi2112

    sifi2112

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    Thank you so much for that response, just the sort of thing I was after :) .... btw I had a look at your site, Thunderchild 112 model looks fab & bet it sounds even better !
    I've heard of AudioKinesis before but never seen any here in UK as yet ... really appreciate you taking the time to answer my queries ... TB is great for this kinda thing :)
  10. sifi2112

    sifi2112

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    Basslite 2010 is about the same price as the B102 in UK so maybe I should look at that instead ... would the measurements change much ?
  11. DukeLeJeune

    DukeLeJeune Only immortal for a limited time Gold Supporting Member

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    Thank you!

    Turns out that same size box works with the Basslite S2010, but its greater x-max allows us to raise the tuning frequency a bit. So you could go with a 6.5" long port. In this case, the net result of changing woofers and tuning freqeuncy is about 2 dB more output at that 62 Hz first overtone of low-B. You'll hit fartout at about the same power level as before, but your low-B will be about 2 dB louder (or at least that first overtone will be).

    Of course there are many other possible box sizes and tunings, but if you like that box size, I think this'll work.

    If you really want to get fancy, cut the inner end of your port at a 45 degree angle (and measure the length down the centerline). This increases the cross-sectional area of the opening there at the inner end of the port, facilitating airflow. "Aim" the opening towards the woofer. This improves the airflow in the place where it's most prone to going turbulent at high levels.

    If the port (or PVC pipe) diameters you have available are something other than 3.0 inches internal diameter, let me know what you have access to, and I'll re-calculate the length. You don't want to go any smaller than 3.0 inches, and a little bit bigger would be better.
  12. Downunderwonder

    Downunderwonder

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    You may not know, Duke is a world class expert on cab design. Lucky you.
  13. DukeLeJeune

    DukeLeJeune Only immortal for a limited time Gold Supporting Member

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    Okay, I overlooked that the tuning is drop-A. Let's reset our sights on the first overtone of drop-A, which would be 54 Hz.

    In order to hit -6 dB at the first overtone of drop-A, we need to increase the internal volume, and I think we should bring our tuning frequency back down a bit. I suggest 10.0" x 12.5" x 15.75" internal dimensions, and our 3" diameter port length shrinks to 4.5". But our port airspeed has gone up into the chuffing zone as we approach x-max, which also means we're losing low-end at high SPLs, and imo we really ought to either use a larger diameter port or use a port that's flared on both ends (which is of course expensive). I've allowed a little bit of leeway in the box size for using a larger port (or multiple smaller ports), so let me know what internal diameters are available to you. This is kinda taking that little 10" woofer to the edge of the envelope, and a protective high-pass filter would not be a bad idea. If you have one available, let me know its frequency and slope (if possible) and I'll try to take that into account as well.

    Thanks, but mostly I just talk a good game.
  14. sifi2112

    sifi2112

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    No HPF at the moment I'm afraid tho looking to maybe get a thumpinator at some point. I do have two 3x4.5" ports if that helps & I'm assuming it's the S2010 we're now looking at.

    If I did the 45 degree cut on the port(s) will it be facing up as I plan on putting port in a rear corner ?

    Also the dimensions ... As long as Vd is per your spec, does it matter which is h w & d ?

    Thanks again Duke :)
  15. sifi2112

    sifi2112

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    I also have a nice grille which is 14" x 12" so I'd like to use this for w x h so depth @ 12" ?
  16. bgavin

    bgavin Supporting Member

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    Increasing the bass extension using a larger box works, but the trade off is less power handling.
    Kinda like stuffing Dolly Parton into a "B" cup... something has to give.

    The point of this being, one can make a small and light weight bass cab for use in limited output.
    WinISD tells me this driver is good for 23 watts down to 41 Hz in the above tuning.

    Link to S2010 Chart

    This is the S2010 in 1.0 cubic feet net volume, with a 4" ID vent tuned at 67 Hz.
    The SPL is not relevant to freespace 1w/1m, because it was measured indoors in a corner.
    Tuning was done empirically by varying the external vent length on the test box to find the most flat response.

    In 1.0 cuft at 67 Hz, S2010 is -10dB by 65 Hz, making it a 2nd-harmonic box.
    Playing Dark Side of the Moon through this setup reveals it does not produce the deep lows inherent in that track..

    The new-style B102 (2007 and newer) are much better suited for bass than the old-style B102 that I own for HF extension.
    The B102 has much better HF response, to 5000 Hz, than does the S2010.
    IMO, neither is practical for full range electric bass due to cabinet requirements and limited Xmax.

    OP, what Duke is showing you are the obstacles one faces when trying to juggle between cost, size and bass extension.
    If the objective is small size and light weight, S2010 is perfect if one can live with an F3 at 70 Hz.
    If you need more HF extension, add an Alphalite 6a and PXB2:500 internal crossover.
    This is still a 23w system to 41 Hz, but essentially flat from 70 to 5000 Hz.
  17. sifi2112

    sifi2112

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    Many thanks for your replies guys (Duke esp) I'm gonna use this grille for h x w & will work out the depth, add a single port but maybe cut it back as suggested :)
  18. daveihde

    daveihde

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    Have been following this thread with much interest, also Duke's TB110, as a small/light cab is what I'm looking for. My thought was to build this box and add the Alpha 6 for smoother mids, don't think I need the tweeter. I play a 5, so more oomph on the bottom would be nice.

    What I really want is a Fearless 110, but frankly, I cannot handle the pricetag. Am wondering if swapping in the Kappalite 10LF for the Basslite 2010 would make enough difference in bass extension and output to justify twice the cost of the driver? I assume I'd need to build a bigger box; has anybody done the calculations and willing to share?
    Thanks, Dave
  19. rogypop

    rogypop

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    You should be looking at bp102.
  20. sifi2112

    sifi2112

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    I've finally got it done :) .... tho it does have an unknown driver that was given to me (looks like an Eminence of sorts) ... it actually sounds pretty good, I've only played at moderate volume & compared to an Eden N8 cab it sound better so far.

    I'll crank it a bit tomorrow but it was never destined for gigs but who knows (I can always replace/upgrade to a Basslite etc) .... thanks again for your input guys & a special thanks to Duke ! :)

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