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Notes on building home made 1x15 speaker cabinet

Discussion in 'Amps and Cabs [BG]' started by Magman, Jan 4, 2005.


  1. Over the past month I've been working on a 1x15 cab. Its nearly done. Just thought I'd make some notes for others wanting to take a first dip into 'rolling your own'.

    I 3/4 inch oak ply I picked up at home depot. It seems fine, but did have shredding along the edges on one side when cutting it with cicular saw. This is ok if those edges are always on the inside but I ended up with much of my outer edges having this problem and then had to fill and sand with wood filler

    Biggest 'mistake' is that rear end is about 1/2 inch 'off' from the front. Now its painted black its not so obvious. I think this occured because of not putting 5 sides together at once (ie clamp/glue sides to bottom all at once to make sure its all square) - so I have to cut the top and bottom sides askew (a slight parallelogram shape) so they fitted properly. A bit of a 'red green show' situation :)
    This will have practical problems if I stack it sideways (a slope).

    If (when) I do this again I'll try get access to someone with a table saw to get easier consistent cuts as well.
    Used a cheap hand held jigsaw to drill holes in baffles.
    Front and back baffle were reinforced with extra strips of the plywood on top and bottom.
    Butt joints with glue and countersunk screws were used throughout the project.

    Internal dimensions are 24x20x18.
    Port is on the rear, 6 inch wide, 6 inch deep
    Speaker is Eminence Kappa Pro 15LF from Dave at avatar - for only 100 bucks. This is a pretty serious speaker, which brought a 'raised eyebrow' look to everyone I showed it too when I opened up its storage box.

    I put wadding I got from fabric shop on all vertical sides of the interior with glue and tacks.
    Speaker grill, speaker sealant putty, jack plate, cab corners and screw-on handles all purchased from partsexpress.

    Cabinet should be tuned to around to 40hz. Havn't tested properly yet, but initial tryouts indicate this is about correct.

    I'm very bad at wrapping xmas presents so carpeting a cabinet I knew I would make a mess of, so I decided just to paint in semi-gloss black paint.

    I fired it up just now and my son comes running down with a big smile on his face "YOU"RE SHAKING THE WHOLE HOUSE!"
    Then there were 2 big smiles :)
    I didn;t have the amp turned up far either.
    However, previous tests with no one in the house had showed that the 200watts the cab is getting get eaten up pretty quick.
    I'm still not sure what is needed for that real dubby earthshaking bass you get at some gigs, but I don;t think this is going to get there by itself.

    On top is my avatar B210. I will swap the rather unmusical tweeter out for the lauded Peerless HD100 tweeter and then I should have a rather nice full range mono-PA/bass rig. A tweak of my amps graphic EQ can pull out the peak in the woofers responce at 2k and smooth things out before tweeter takes over.

    To all those who say the b210 has plenty of bass - it does in the mid-bass (100 hz) which will shake your teeth, but not down in the 'real' low end.

    So far cab seems solid and works perfectly. It was definitely rewarding to build - there is something peculiarly satisfying about constructing a large ominous black box which spews out sound in large quantities. The wife has chosen to ignore the project. I said the experience will help me build better bookshelves for the house :)

    I was planning on building one of bill fitzmaurices Tuba24 subs, but thought it too complicated and
    best to start with something simpler. Glad I did. I think I would be a bit gun-shy about the tuba unless I can get a more woodworking experienced friend to help me. All those long angled cuts could be a pain with just a guide and circular saw.

    I'd like to build another cabinet but don;t really have an excuse too yet.

    MM
     
  2. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Chicago
    Congrats on your wall shaking creation...

    Before you buy a new tweeter for the B210, check out the thread on simply replacing the crossover...
     
  3. rllefebv

    rllefebv

    Oct 17, 2000
    Newberg, Oregon
    Congrats!! I too have a rig comprised of homebrew 1X15 cabinets, also using Kappa 15LFA's... I used the recommended internal volume specs from the Parts Express page, (3.9 Cu Ft), for each cabinet... Plenty loud! The two of them together are more than enough to get my low-end rocks off!

    I originally finished them natural, but after a couple of years went to black... I used a couple of cans of spray-on bed liner... Very durable, and a nice matte finish.

    -robert
     
  4. Thanks!

    I'll check the thread. I'm pretty sure that I'm just not hot on the current tweet, but could be wrong....
     
  5. thanks!
    yeah - accounting for volume of port and driver my cab is about 4 cubic feet also.
    a second would be mad - I;d thought about getting a second amp to run the 2 15's, and then running the 10's through my first amp with the low bass rolled off - a very simple biamp setup.
    and how much louder does adding the second cab make the whole thing?

    how much power do you put into them?
     
  6. Those internal measurements yield a gross internal volume of 5.0 cubic feet. Subtract 0.16 for the driver displacement, and a teenie bit for the port, and you still have an over-large cabinet. See my spread sheet for details.

    In a nut shell, this will yield an EBS (extended bass shelf) type alignment, and is typical of Avatar Speakers designs. EBS extends the bass response but results in a significant increase in group delay (mud) at the tuning frequency.

    This is a very nice driver. It falls midway between the very punchy high-end JBL, and the el-cheapos on the low end. Both the LF and the improved LF-2 version are roll off above 1,000 Hz. You will need another driver(s) to operate between 1,000 and 7,500 Hz.

    Eminence makes an inexpensive 800 Hz crossover that will do the job for 8-ohm loads. If you are using a 4-ohm 2x10 for the highs, the Eminence crossover will be mismatched.

    Precision cuts are very do-able with a circular saw and straight edge. I've built a number this way. The down side is it is time consuming to precision measure and clamp the straight edge. The advantage of a table saw is that all common widths can be cut on a fast and repeatable basis.
     
  7. ooops!
    must have got my math a bit wrong somewhere....*blush*
    maybe calculating volume of driver.

    So I've got a bit of a lop sided mud box now <laugh>.

    having said that, in winISD at least, with a tuning of 40hz, group delay isn;t affected *too* much by the difference between a 4cft or 4.8cft box -- 2ms. ( 12ms vs 14)

    BGavin, when would you say that group delay becomes a noticable problem - after 6ms? 10ms?

    be interesting if I build a second unit to use a smaller box with a different alignment and hear the difference.

    Using a clamped guide with circular saw is exactly what I was doing. Its a bit fiddly but generally seemed to work... however, in general I found it tricky to get perfectly identical cuts - sometimes of the boards ended up very slighty 'off' (a milimeter or so). Practice makes perfect though (along with care and patience).

     
  8. If I have 2 woofers with different alignments (and thus different group delays), does this create even more mud as delayed frequencies are out of sync? (at least with one woofer, its in sync with its own delay and theres no interference).
     
  9. ...actually the internal depth is less than 18 inches..probably about 16.5 ..I didn;t have my original plans to hand when writing post last night and remeasured the cab and forgot to deduct thickness of board on the depth measurment.
    Doh, sorry.
    I estimate that still puts me a bit over 4cft deducting port, driver and bracing.
    To work out driver volume - best to treat it as a cone?

     
  10. I just read that thread.
    Now I'm reconsidering wether I need a new tweeter!
    Thanks for directing me to this: I'll probably just wire an inductor across the tweeter as suggested to increase roll off slope. As a first measure at least.


     
  11. 25 msec is very sloppy and noticeable. Compare this to < 6 msec, which is the realm of the sealed box, and very tight. A larger sealed box (D2) has lower delay numbers and is the "optimum" for flat delay. The smaller B2 alignment has the max low frequency extension for a sealed box, with a tiny bit worse delay, but better power handling. All will sound significantly tighter than a vented box, because the port is always at least 90 degrees behind (delayed) from the driver. It is the nature of vented boxes. In a well designed system, nearly all the output comes from the port at the tuning frequency, so the lag isn't much of a problem.

    You can always fill the extra space with a sealed box made from ply that won't flex. This is an easy way to reduce cabinet volume, but will affect port tuning. The 15LF-2 driver is looking for 2.5 cubic feet (net), when tuned to 35 Hz.

    Group delay isn't a problem if it occurs below your playing range. If you plot the delay for 35 Hz tuning, you will find it significantly less at 41 Hz and higher. It's all about trade-offs.

    A very low tuning can put the upper resonance right at the bottom of your playing range. This is typically 1/2 octave up from Fb, and coincides with maximum cone movement. If this occurs at the bottom of your operating range, the cone is moving the hardest (farthest) at the most severe frequency it has to produce. Cone excursion increases 4x for every octave down.