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Cabinet Building question

Discussion in 'Amps and Cabs [BG]' started by Crockettnj, Oct 15, 2005.


  1. Crockettnj

    Crockettnj

    Sep 2, 2005
    North NJ
    hello,

    1) Trying to find the volume displaced by the peerless 831759 "len Moskowitz" 10" speaker. I looked around and have still been unable to find this data.

    I have heard I could compensate for the volume that the driver takes up by adding acoustistuff or other damping material inside- is this myth? Either way, i prefer to factor in the exact speaker volume.


    2) Also, If i deceide to go with 2 ports instead of 1, is the length of each new port 1/2 the length of the original longer port? (assuming all are same diam)



    thanks in advance.
     
  2. The answer to question 2 is: NO
    I suggest you to use a program like winisd to calculate port length.
     
  3. rpatter

    rpatter Supporting Member

    Sep 18, 2004
    Round Rock, TX
    That must have been discontinued a while back. I couldn't even find it on the the discontinued drivers page of the Peerless site. Anyway I did locate the t/s params in an old catalog:
    fs: 21.7
    Qts: .28
    Vas: 121.9 liters

    Depending on the size of your port, you probably want to go with two. Stuffing with dacron, fiberglass, etc will increase the apparent volume of the cabinet 10-20% depending on how densely you stuff it. 1/2 lb per cu. ft. should compensate for the driver without affecting the tuning too much.

    To add a second port of the same diameter, you will need to double the length and then some. I can't remember the correction factor off the top of my head. Are you using the design right out of Len's Speaker Builder article or do you have a program you are using to do your calculations? PM me if you have any more questions, I'd be happy to help you in any way I can.

    Ralf
     
  4. Crockettnj

    Crockettnj

    Sep 2, 2005
    North NJ
    Hey, thanks for the fast response.

    I am not using lens article exactly, however i have gleaned a bunch of info off the net about his article, and decided that it's a nice fit for a little practice cab. Plus, i want to get some cab building experience under my belt. ;-)

    i have the woofer (ebay) and the wood (home depot) and will grab the mid when i see one (or when a certain someone on here decides to sell one to me!) The corssover will be bought or made by the local digital electronics class. Havnt decided yet.

    OK- i am using WinISD online but have occassional access to WinPro (from linear team). So i am not going blind, but i am frankly shocked at home much volume i am "losing" after i deduct bracing and port and cab walls etc. I dont know how Len built a 1.6 ft3 cab and still used this driver in an optimal flat alignment. On paper I am getting down near 1 cubic foot net volume. (??!!) And that's starting with a 1.7 ft3 cab. Hence my question on damping materials "adding" volume.

    I am not a 5 string player, so an f3 of 41 would be fine, as opposed to len's 35 or so. Therefore i think i can lose some volume safely, but i want to calcualte them exactly. Lacking the driver volumeinfo, i am going to measure it try to figure it myself tomorrow. ugh.

    ANYONE who has an decent estimate on this , I'd appreciate it.

    ps- i will be IM'ing you when i solidfy things a little more and have some more time.

    thanks a ton.

    Has there ever been a "len's cab" thread on here? I see mentions of it, but nothing dedicated.
     
  5. Ralf, please post Qes, Qms, and any other data you have for this driver. I have it in my spread sheet, but some of the data is missing.

    Crockett, download my spread sheet and sort it by F3 to find what you are looking for. Typically, an F3 of 41 Hz requires a big box to be efficient, or a small box that is very inefficient.

    Look into the combination of Eminence's Omega Pro 12 and their Alpha 6. This works very well in a reasonable (Len-sized) cabinet, and performs very well. F3 is around 60 Hz, which is reasonable.

    There is vigorous discussion about most basses not generating much of a fundamental, meaning they generate the strongest signal in the 2nd harmonic. If this is the case with your bass, 82 Hz is the lowest (strong) note from your 4-string. An F3 of 60 Hz is more than sufficient to produce a very strong sounding bottom with your bass in this case.
     
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    I agree with Bruce for the most part, though for a practice size cab I think a BP102 would be plenty of driver, or perhaps a B102 to make a mid-driver unnecessary.
     
  7. Crockettnj

    Crockettnj

    Sep 2, 2005
    North NJ
    Bruce-

    thanks for your input. I certainly have download3ed your spreadsheet, and sorted via f3 and other parameters. I have to say that spreadsheet is a wealth of info. truely a terrific resource. I also noticed, much to my chagrin, that you dont have the driver displacement volume!

    i cut and pasted your post regarding the eminence 12's and the 6 from a thread a little while back. I liked the sound of it then, so to speak. Frankly it sounds like a better cab for gigs than the one i am building. Thats's OK though, this cab is for practice- both in building and in using it. However I have already purchased the 759. Hell, I could just buy an aguilar gs112 or acme 1 and be fine. Part of it is that I like to tinker. I like projects.

    The lower efficiency of the peerless driver shouldnt be an issue . this cab is for practice only, and I used an SPL meter in practice for the last couple weeks and found that the max of this cab (about 112db given full 200 watts) is well withing my needs.

    No, this is a small practice cabinet. Len did it with 1.6 ft3 overall using 3/4 MDF. I am using 1/2 ply and 3/4 inch cove moulding as bracing, so I shjould be able to acheive somehting similar to his, if not slightly SMALLER. I am jsut a little stumped on how to determine the volume of that damned speaker!

    If you come across anything, bump this thread. also, if you know of another speaker that is a reasonable shape/size, I could use the Vdr of that one.
     
  8. Crockettnj

    Crockettnj

    Sep 2, 2005
    North NJ
    I just read one of the links someone gave me and saw that someone said an average volume of 10" drivers is 1.5 liters displacement.

    IYO is this in the ballpark, and if so, am i jsut splitting hairs here on a difference I wont even be able to hear anyway?
     
  9. Crockettnj

    Crockettnj

    Sep 2, 2005
    North NJ

    Bill-

    Thanks for the reply. The bp102 was on my list a while back, actually as a 210. However, I got a good deal on the peerless driver already (ebay).

    Once i sell both of my 115's, and i start looking for cabs to use in gigs, i am pretty sure I am going to go with 1 or 2 used aggie 112's. They seem perfect for my needs, it would be modular, small enough, full range for 4 string, and teh used price is usually a tad under 300.

    This project is purely for practice and to say "i made it" but i dont want to jsut slap it together without predicting the outcome to some degree of accuruacy.

    Thanks again.

    On a side note, that post bruce made about (and i am paraphrasing) the second harmonic possibly being more dominant than fundamental is very interesting. My bass is swamp ash and it really is very bright- much more so than my pbass. I wonder if the 2 are related?
     
  10. rpatter

    rpatter Supporting Member

    Sep 18, 2004
    Round Rock, TX
    So far all I have is Qts. I'll keep rooting around for old catalogs.

    Ralf

     
  11. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    That will have a lot to do with the high frequency tone but very little to do with the fundamental vs 2nd harmonic/3rd harmonic balance, which is mostly a property of string length versus wavelength.
     
  12. rpatter

    rpatter Supporting Member

    Sep 18, 2004
    Round Rock, TX
    Found it!

    fs: 22.4
    Qes: .3
    Qms: 2.84
    Qts: .27
    Vas: 121.9 liter
    Cms: .9
    Mms: 56.2
    Xmax: 7.5
    SD: 310 sq cm
    Re: 2.6
    Le: 1.8
     
  13. What is the source document? If PDF, can you email to me?

    I have made the changes to my spread sheet, and noticed some of yours disagree with what little I had.

    I put all of yours into the spread sheet, hence wanting to know the source for the data...
     
  14. My problem with the BP102 is the cabinet volume. It requires a minimum of 2.2 cubic feet for proper performance, with an F3 of 39 Hz. SPL is only 91, which is pretty anemic.

    This driver runs out of steam above 2KHz, so a supplemental driver is required.

    The Omega Pro 12 is a whole lot more driver down to 70 Hz, and in a much smaller cabinet. In QB3 (1.1 cubic feet) it has an F3 at 61 Hz, and is +3dB more SPL than the BP102. The Omega Pro 12 also requires another driver above 1,200 Hz.
     
  15. rpatter

    rpatter Supporting Member

    Sep 18, 2004
    Round Rock, TX
    Sorry, no PDF. I checked BassBox Pro and sure enough, it was in there. I'll keep looking for old catalogs anyway, just as a reference. Ironically, a couple of months ago I cleaned out a bookshelf and got rid of a bunch of Madisound, PE and Solen catalogs going back almost 10 years.

    Ralf
     
  16. Thor

    Thor Moderator Staff Member Gold Supporting Member

    I am in the middle of building the Len Moskowitz Compact
    Bass Speaker cabinet as well.

    I have not posted a thread, but I am about 1/2 done with
    the project.

    I have a copy of Len's original published article, which is interesting as it is complete with freq plots and diagrams.
    You can contact Len directly and he will send you one.
    He restricts reprinting of the article specifically, but will
    send it for free with a SASE.

    I was going to post a 'build thread' when it was done, but go ahead if you are ready and I will add mine later. The project
    went on hold for the summer... yard work and that stuff.

    I also have the driver out in my laundry room, but I don't
    think a spec sheet was with it. I will double check tonight. Also, Madisound still has a few of the 1646 mid-drivers left, but only a couple. That was when I spoke to Larry Hitch there a couple of months ago or so.

    Note that Len's article was published in Speaker Builder in
    February on 1994. There has been a wealth of material
    added to the 1x10" paradigm since. He used 'Perfect Box' for the box design. WinISD may have lead him down a different path today, who knows. But since he published in early 94, I would expect he built this in 1990 or 1991, given publishing review lead times.

    On page 16 of the article, Len Moskowitz states

    Also, I sourced all the materials required for the project,
    if you would like the sources PM me, or I can post them.

    Following Len's logic at the time, first he decided on a
    approximate size he wanted to lug around, (page 11), then
    he investigated what woofers were available in 10 inch and
    spotted the Peerless 1759 which was marketed to the
    homeaudio marketplace. His criteria, (see here
    http://www.core-sound.com/bottom-article.html
    for those who are not familiar with it) included low Fs
    22.4hz, 'reasonable' efficiency (91.4Db for 2.83 V @ 1m)
    and acceptable cost ( $65).

    The results from Perfect box he published were:


    At the time it suited him quite well. I need a small practice cab at home as well, and met my needs for a
    first DIY cab. Ironically, I did the 2x12 build below in the
    middle of this project. I got sidetracked as I needed a
    cab in out band space.

    A taste of the build is below:
     
  17. Thor

    Thor Moderator Staff Member Gold Supporting Member

    ... and here:
     
  18. Crockettnj

    Crockettnj

    Sep 2, 2005
    North NJ
    Thor, glad someone else is undertaking this project! Seems like we have damn near the same goals- i small low practice cab, but also to DO it to gain experience.

    dont be shy in posting a HOW TO thread when you are done- then we could ask the members for advice on how THEY would improve upon his components/design given the same goals... in the year 2005.
     
  19. Crockettnj

    Crockettnj

    Sep 2, 2005
    North NJ
    bump


    thor, any pics on the finished cab yet?
     
  20. Thor

    Thor Moderator Staff Member Gold Supporting Member

    No Crock, I had to put it aside for a while as my
    house is under construction and I needed to store
    a lot of stuff in the space that I normally use as a
    work area. Unfortunately, I really need a practice cab at
    home, so the sooner I can get back to normality, the better.

    But once we are back on track, I will fire up some pics.