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DIY Cabs--Source for plans, components, etc.?

Discussion in 'Amps and Cabs [BG]' started by emor, Jul 24, 2004.

  1. emor


    May 16, 2004
    I have spent some time checking out amp manufacturer's websites and doing some searching in the TB archives and have come to the conclusion that buying a complete (quality) rig that is powerful enough to play with a band is a bit out of my budget at this time.

    My thought now is to buy the head, and the components for the speaker cab and build the cab myself.

    I am a cabinetmaker by profession, (but don't know much about the science of speaker cabinet design) so building the cab is no problem as long as I have a drawing to work from.

    I would appreciate any suggestions for books, websites, etc., where I might find general info on cab design, and specific plans to work from. As with a lot of players, I'm looking for the biggest sound from the smallest possible package. (I am really intrigued by the Schroeder 21012--is it really comparable to an 18"?)

    I am also looking for sources to purchase speakers (and hardware) as well as reviews, comparisons and recommendations.

  2. K-Frog


    Feb 6, 2002
    Camden, AR, USA
    You'll find a good assortment of cab handles, corners, jackplates, etc. at www.steelsound.com

  3. Try this site: http://ldsg.snippets.org/index.php3

    Also get a Parts Express catalog www.partsexpress.com Their site is very good and they have all the parts you need.

    Get "The Loudspeaker Design Cookbook" (Parts Express sells them). Also they have a book on speaker projects for musicians, forgot the exact title.

    Download WinISD (shareware) to help model cabinets.

    Since you already must have a pretty good shop, you may be able to save a few dollars over used, but IMHO it won't be a huge savings. Plywood, feet, corners, carpet, glue, grills, handles, ports, jacks and jack plates, they all add up. And of course there's the time factor. (If you build cabinets already though, it won't take you as much time as somebody who's just learning how a table saw works)
  4. emor


    May 16, 2004
    Great! Just the kind of stuff I was looking for. :)
  5. My spread sheet has all the speaker data you can want. It will tell you which internal volume is correct for your driver.

    You *will* have to final-tune it with a DVOM and signal generator. The calculations will get you close, but the final tuning must be done manually.

    1) Figure out what sound you want
    2) Figure out how low you want to go
    3) Figure out how large a cabinet you can tolerate
    4) Pick a driver based on these needs, then build to fit.

    As for teenie cabs doing the job of an 18"... manure. Until such times as full measurements are published, it is just advertising manure. If teenie speakers could do the job of 18s, then all the PA companies would use them, instead of those big and heavy 18" cabs.
  6. Bongolation


    Nov 9, 2001
    No Bogus Endorsements
    You can probably blow off the books these days in favor of design programs, such as BassBox 6 Pro and many others, some freeware.

    Designing anything but the most exotic transmission-line, folded-horn cabs is pretty cut-&-dried with manufacturer's Thiele-Small parameters commonly available and well-designed speaker cab software.
  7. Doing a web search with words like "build design ported sealed bass cabinet" will bring you do some other DIY projects that are being shared. There are a variety of internal bracing solutions and joinery options available with these resources.

    WinISD Alpha is a downloadable design program which will help you with design parameters based on your chosen driver's Theile Small parameters.

    If you are at all interested in Eminence drivers (many companies use these in their own cabs- Fender, Ampeg and more) do yourself a big favor and check out avatarspeakers.com . They are a speaker cabinet maker who will sell the drivers they use seperately. Their prices simply cannot be beat. You will save about 30% on the Delta10, Delta12lf, and Kappa15lf.

    Remember that although the driver is an important decision the cabinet they are placed in make or break it. Have fun and good luck.
  8. Bongolation


    Nov 9, 2001
    No Bogus Endorsements
    Hey, speaking of drivers, would someone give me a good answer to this question?:

    Why are the better 12" & 15" drivers for car audio subwoofers unsuitable for bass cabs, or are they?

    I've asked this a couple of times before elsewhere and just got really moronic "ha-ha" answers.

    The good ones are generally better built for more demanding conditions than the typical stock stuff that comes in most bass cabs I've examined. The only thing I can think of is that as subwoofer drivers they may not have the low-midrange of at least some of the bass instrument units I've seen, but I haven't checked the frequency curves of any of them to confirm this.

    Though they have higher MSRPs than the typical bass instrument drivers, they are always loss-leadered and closed out at places like Fry's for about half of what it would cost to get instrument drivers, never mind the shipping costs and inconvenience.

    Thanks for any insight on this.
  9. I will try to end this hijack quickly.
    Car subs have a much lower efficiency than pro audio drivers. You would need a s^&*load of power to match the volume of pro audio.
    End hijack :spit:
  10. Car subs do not have the frequency response of pro audio bass drivers. They may go as low, but only respond up to 100-200Hz, typically. Additionally, where a good pro-audio driver may have a sensitivity (how loud it goes at a given power level, usually 1 watt with the sound pressure level measure 1 meter from the baffle) of 95-100dB/1W/1M, even the best car audio subs are down in the high 80's, or around 90dB for sensitivity. This is a huge discrepancy. Basically it means the car subs will need several times more power than the pro audio subs to reach the same sound pressure level.

    Using the fact that it takes a doubling of power for every 3dB increase in sound level (a noticeable change), think about this. With a car audio sub that has say, 89dB sensitivity at 1 watt, here's how it goes:

    1 watt ------- 89 dB
    2 watts ------ 92 dB
    4 watts ------ 95 dB
    8 watts ------ 98 dB
    16 watts ----- 101 dB
    32 watts ----- 104 dB
    64 watts ----- 107 dB
    128 watts ---- 110 dB
    256 watts ---- 113 dB
    512 watts ---- 116 dB
    1024 watts --- 119 dB

    So at a kilowatt, we're at 119dB

    For a pro-audio driver, rated at 98dB sensitivity (not uncommon),

    1 watt ------- 98 dB
    2 watts ------ 101 dB
    4 watts ------ 104 dB
    8 watts ------ 107 dB
    16 watts ----- 110 dB
    32 watts ----- 113 dB
    64 watts ----- 116 dB
    128 watts ---- 119 dB
    1024 watts --- 128 dB

    Notice with a kilowatt here, we're at 128 dB. This is almost 10 dB higher than the same power applied to the car audio sub. 10dB is a doubling of volume. Also note that to achieve the same 119 dB sound pressure as the car audio sub did at 1024 watts, the pro audio driver only required 128 watts. The car audio sub required nearly 10 times the power for the same sound pressure level.

    You can see how this works out in all situations.

    Hopefully this answers the question.
  11. You missed one point: frequency.

    The pro audio drivers are indeed more sensitive. But to get down as low as a car subwoofer, they have to have an enormous cabinet. An Eminence Delta 15a is flat to 30 Hz... when operating in 20 cubic feet.

    The sensitivity difference is the tradeoff between low frequency extension and cabinet size. If you want flat to 31 hz, you either feed it a lot of power, or put it into a huge cabinet. In physics, there is no free lunch.

    I own (4) 15" car subs (Rockford RFR-2215) that are flat below 31 Hz. Yes, they require a lot of power... so what. Yes, they have little response above 125 Hz, but that is why they are "subwoofers". I bi-amp mine.

    As for the power chart above, it does not compensate for power compression, nor the fact that most drivers will not accept full power below 100 Hz because of cone over-excursion.
  12. Bongolation


    Nov 9, 2001
    No Bogus Endorsements
    This is very interesting and I'm glad to see I was on the right track about frequency bandwidth being a factor. I had wrongly assumed, though, that the car stereo drivers would be of higher efficiency.

    Looking about, I see that the issue of sensitivity ratings is a complex one. Ratings have to also state the exact parameters used in measurement, as there is so much wiggle room otherwise that the figure is probably meaningless.

    Note that the Eminence tables in the above link show nothing below 200Hz, even for their 18" drivers.
  13. JBL and ElectroVoice were always full disclosure manufacturers. Eminence publishes response plots for all their drivers, and states how they are measured. You can take this as accurate.

    Phil Jones is the only one I'm aware of that publishes actual response plots for his cabs. The rest just claim the moon for specs, but this is just bullsh!t without proof.

    Car subs are designed to go low, in a small space. These two requirements for the 3-way equation guarantee the 3rd: inefficient.

    What is more important is understanding how much wattage your driver can accept at 40 Hz before over-excursing or melting. Then you can calculate the amount of acoustic power it will produce.
  14. These are indeed things I didn't include. Thanks for adding those on. I figured power compression wasn't necessary, but the frequency response vs. box volume is a pretty big deal.
  15. Bongolation


    Nov 9, 2001
    No Bogus Endorsements
    OK, so back to the original question: Does anyone have a good source for plans for more exotic bass cabs? I've been googling all morning to no avail.

    I was thinking of maybe a folded horn or something sexy and beyond the typical simple ported enclosure.

    I've seen no programs for designing anything that complex so far.
  16. Chasarms

    Chasarms Casual Observer

    May 24, 2001
    Bettendorf, IA USA
    I'd be interested to read if any one out there actually was able to conclude that building your own cabinet was a cost-effective alternative to purchasing a factory-built one.

    There are plenty of reasons out there to build a cabinet including sound, power handling or simply the satisfaction of knowing that you built it yourself.

    But in nearly 20 years of bassin', I must have looking into building my own cabs at least a half dozen times, and everytime, the cost ends up adding up to be more than I could have bought one already made. IME, economics is not a reasonable motivation to go the roll-your-own route.
  17. Petebass


    Dec 22, 2002
    QLD Australia
    I've saved money on building cabs but only when I got a great deal on some part of it, or I manage to get get some freebie parts. It's not any cheaper unless you've got some of the obstacles removed. In this case, he's a cabinet maker which means he can probably save on the timber, he's already got the tools needed, and he's got a better chance of getting the construction right than most people :)

    As for the designs plans, you're not ready. You have to narrow down what you want. There so many thousands of speaker/cab combinations possible that it's just too much to ask that we guess for you.
  18. Bongolation


    Nov 9, 2001
    No Bogus Endorsements
    I always tell people it's totally a fool's errand and all the homebuilt boxes I've seen seem to look awful in the bargain.

    In terms of build and finish, I can build a cab better in my sleep than the overpriced junk I've been buying from "name brands." I used to work for a boutique sound reinforcement speaker manufacturer NYC and know what's involved in making a good box.

    I think actual acoustic design is minimal in most commercial bass boxes and the drivers are not that hot, either.

    I'm thinking that in the absence of any red hot deals on new commercial cabs, I can probably build a better box in almost all respects and come out slightly ahead on cost.

    Normally, I'd say the average guy would be nuts to build a box and if I didn't personally have a lot of experience with that sort of thing and a lot of time on my hands, I wouldn't either.