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DIY cab? (1x15 + 1x8?)

Discussion in 'Amps and Cabs [BG]' started by CrawlingEye, Jun 28, 2003.


  1. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    Ok, so I've been considering doing something to change my sound. I'm really looking for something that'll give me a very smooth yet relatively bright sound.

    I've noticed in pretty much every cabinet that there's at least one fault. The BagEnd 15"'s I've tried are excellent with producing smooth lows but seem to be at a loss in punch and at any high frequencies, aside from using the coax, which to me sounds clacky. I'm guessing going DIY would be the chance for me to obtain my ideal cab.

    I'm thinking currently of using a 15" and an 8". Obviously the 15" would produce the lows and the 8" would be my high speaker.

    The thing is, I'm thinking of going 1x15 and 1x8, rather than doubling the 8"'s. I've tried going through the Cabinet Building 101 thread for info but can't find anything on this type of configuration. In the thread I found WinISD which I tried using but still won't give me the cabinet size or port size for the enclosure.

    I was thinking I could try and just add the dimensions given by WinISD together and come up with the cab size, but even if this would work, it still doesn't help me with the port size.

    The two speakers I'm looking at are the Eminence Omega Pro 15 and the Eminence Beta 8.

    Any help would be appreciated. Thanks. :)
     
  2. you should rather use a "cab-in-a-cab" design and have separate enclosures for the 15 and the 8 integrated into one larger enclosure0, because this will be far easier to design (your idea can almost only be done by trial-and-error)
     
  3. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    So I would just increase the size of the 1x15"'s suggested cab the size of the 1x8"'s suggested cab size and just make it a cab-in-cab design, just putting the 1x8" inside the 1x15"'s enclosure, porting both?
     
  4. well, if the 1x8 is in a separate enclosure inside the 1x15 enclosure it should work
     
  5. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    Another thing I'm noticing is that with the vent size, it's not showing an appropriate size for the 8". It just keeps saying that it's too short unless I make it in excess of 1 meter, which I don't think is an option.
     
  6. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    That might happen if you:
    1. make the 8 box bigger than .25 cu ft or
    2. try and tune it low.

    I hope you're not expecting a Beta 8 to run full-range with a bass signal; it'll fry pretty fast. To run a 15/8 rig you will need to either biamp or use a crossover. I had a Peavey 1516 that crossed over at 450hz using a pair of 8's .

    There are 8" drivers that will go low, but they don't go very high or get loud and the 15 would walk all over them because it makes a LOT more volume from a watt (like 98db vs 88 db).

    The Omega Pro 15 is a very nice driver; if you search Bgavin's posts he was going to use 3.76' I believe.
     
  7. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania

    In response to 1, I'm going with what WinISD suggests, I've put no input on the cabinet sizing.
    2. The speaker on Eminence's site is rated at a frequency response ranging from 55Hz to 4KHz. I'd say it could handle most frequencies for a 4 string, low E aside.

    According to WinISD the SPL of each are very similar and the 8" is only off by about 10dB. I'd say that's pretty close and very accurate for what I want to use it for.

    I just want it to act as a high frequency speaker. Kind of like a tweeter, in function.


    Thanks for the help so far, everyone.
     
  8. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho

    I'm afraid I pulled the .25 cu ft figure out of the air.


    "Handle" is the operative term. Accurately reproduce without distortion is likely to be something else on the low end as the speaker exceeds Xmax. WinSD does not take excursion into consideration unless it's changed since I last looked.


    10db would be perceived as about twice as loud, and require about 10x the power to equalize.


    The cheap way to do that is to get a high pass filter and put it inline with the speaker so it blocks lows getting to it.

    The Omega is a pretty high-end speaker and the Beta is a pretty low end speaker. You might have better luck with a higher quality speaker than the Beta, like a B-102 10".

    The beta is (quoting Eminence):

    Performance optimized
    for midrange use between
    400 Hz and 4kHz in multi-way
    systems. Also suitable for
    vocal P.A., keyboards, club
    systems, stage monitors,
    and bass guitar.

    and only has 3mm of excursion; a decent tweeter from 400hz up I'd say.
     
  9. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
     
  10. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I'm not a fan of the beta series either. But regardless of which 8" you decide to use, I'd certainly look to put a high pass filter on it. All you'll need is a capacitor (which are not expensive) inside the 8's cab and in the positive part of the speaker wire. This will give a 6dB per octave rolloff. If you choose the right frequency, this should be enough to keep the lows away from the 8 and prevent it from over-excurson damage. If eminence is saying 400Hz, I'd be setting the filter somewhere around 800Hz. So at 400Hz you're 6dB down, 200Hz you're 12dB down, 100Hz you're 18dB down.

    If being -6DB at 400Hz is not acceptable, a 12dB/octave works better and can be set to a lower frequency. But this involves expensive inductors. With a 12dB flter, you could bring the crossover point right down to 400Hz and you'd still be 12dB down at 200Hz, same as above, but at 3 or 4 times the price.
     
  11. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    oh I forgot to mention..... you'll need something to take the frequencies above 4k. A Horn maybe....
     
  12. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    I don't really care for frequencies above 4k, so that won't really be needed. :)
     
  13. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    Hrm, I think I'm going to change it to the Alpha 8. It seems to be the only other 8 that they make and the better of the few.

    Any thoughts on this in comparison to the Beta?

    I have a question on vendors for speakers?
    It seems a bit difficult to find them, so far I've found only one, which seems to have a bit high of prices.

    I have two questions as well, would it be a wise idea to tune the 15" to 41Hz since I play only a 4 string, or should I tune it lower?

    Also, what do you think should be ideal for the 8" as far as cabinet tuning frequency goes?

    or for both, should I just stick with what WinISD tells me?
     
  14. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    I don't know about the Alpha 8. It does have the advantage of having it's own sealed back section so you won't have to worry about a seperate cab-in-a-cab for it. But that's where the good things stop. Sensitivity at 1k is a good 6dB down on the Omega so you'll bearly hear it. QTS of 2.07 is exremely high. Generally drivers with a low QTS are higher quality. 0.4 is considered high.....

    My advice - look at 10's instead. Or look at other brands of 8's.......

    The speaker has a resonant Frequency (Fs) of 39Hz. If you were using a SBB4 alignment, then you'd tune the cab to 39 Hz. Playing a 4 string, you'd never get that low so you'd have no problems with speaker over-excursion.

    Win ISD doesn't use SBB4, it uses a "flat alignment". So it will probably suggest you tune it higher. If the suggested frequency is higher than 45Hz, go to SBB4. You'll have to re-calculate the cab volume though.

    Win ISD can be tricked into SBB4. Manually type in the cab volume as 106.39 litres, then ask it to tune the cab to 39Hz. Viola, it will spt out the vent details for you........
     
  15. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    Ok, so in short, ideally I should get something like the Eminence Delta 10A (10") and the Eminence Omega Pro 15 (15") for my speakers, running them each in parallel (producing a 4ohm load) and use a passive 2 way 1st order filter with a 3.30mH inductor and 24uF cap, which should cut the 15" at a 6dB loss at 400Hz and 12dB at 800Hz, while doing the reverse for the 10", it should cut the 800Hz by 6dB and the 400Hz by 12dB.

    And Pete, I'm not quite sure I understand "SBB4"?

    Could you elaborate? It could be because it's 5am and I've been up all night playing around and reading things on this new cab planning.
     
  16. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Omega + Delta 10 is looking much better. We're back to a cab-in-a-cab though. So the delta will need calcs for box size and porting.

    But now that we've picked a different mid-high driver, all that crossover talk needs to be re-visited. Why? Because the Deltas have a much lower resonant frequency (65Hz). So crossing it over at 800Hz kindaseems like a waste of a good speaker that is capable of much more. This this can produce some really good mid-bass, so we may as well let it.

    If it were me, I'd be steering away from a 2 way crossover. Instead I'd put a seperate filter on each speaker, each one with a different frequency. As far as I know, there's no reason to cross them Both at "x" frequency.

    I guess I'd put a low pass filter on the 15 at say 400Hz (for an 8 ohm speaker, that means an inductor of 3.3mH, make sure it has an air core).

    But for the Delta 10, I'd use a high pass filter at 130Hz, one octave above Fs (so a capacitor of 260uF for 8 ohm speaker). To me this opens up a whole bunch of frequencies in the midrange that are instrumental in cutting through the mix. And given that there's only 1x10, this is probably more important than if we were using the more traditional 2x10's.

    SBB4:- Back when the pioneers of Acoustic design were working all this stuff out, several trains of thought popped up along the way. Each train produced it's own set of formulas and idea-ologies. The result is a set of different alignments with different box sizes, and overall chacteristics. SBB4 is the alignment everyone uses because it sound good and the box sizes aren't too enormous. The flat alignment used by Winisd produces a slightly larger box in must cases, a slightly higher tuning frequency, and a slightly higher group delay (ie muddy bottom). There are other alignments but this post is already too long.

    For example the Delta on WinIsd is probably 15.7 litres and tuned to 81Hz. With SBB4, it would be 14.6 litres and tuned to 65Hz, whis is also the speakers Fs.

    The Omega on WinIsd is probably 122.6 litres and tuned to 45Hz. With SBB4, it would be 106.4 litres and tuned to Fs being 39Hz.

    Use Winisd to plot all 4 of these and you will see the different frequency responses in the low end. Have a look at the Group delay graph and you'll find SBB4 has the better result.


    Don't fret, both aligmnets sound quite good.
     
  17. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    PS:- Good to see someone doing their homework and designing the cab properly. Onya CrawlingEye :)
     
  18. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    Thanks, I think I'll try your suggestions with the SBB4. :)

    I appreciate all the help from everyone.
     
  19. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    We want the occasional update....... pics if possible :)
     
  20. HeavyDuty

    HeavyDuty Supporting Curmudgeon Staff Member Gold Supporting Member

    Jun 26, 2000
    Suburban Chicago, IL
    A suggestion? Try to find an old Peavey 1516 cab to try first - it's a 2x8 + 1x15. I have one that I leave at my guitarist's place with my 400RB, and it's amazingly good. They can be had cheap - probably cheaper than it would cost you to build.