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How do _you_ choose drivers?

Discussion in 'Archived Threads 2001-2004' started by Brian J Dupuis, Jul 12, 2001.

  1. Brian J Dupuis

    Brian J Dupuis Second Unit

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    Hello,
    First-time poster with hopefully a reasonably non-idiotic question. How do you choose drivers, from the seemingly endless array of available ones, for your projects? Do you go by respected manufacturer and choose from their offerings? Do you rely on peer reviews of particular drivers (as I see a lot of excitement surrounding the Shivas and Tempests around here for subwoofers)? Do you utilize your experience with T/S parameters and peruse countless lists of drivers to find the ones that match your selected criteria?
    I am soon to start my first DIY project (a subwoofer... seems easiest to get my feet wet and is my current need in my system) and am really just curious to know what experienced DIYers use as a 'filtering mechanism' amongst what, to a rather inexperienced newbie, looks like a bewildering quantity of (somewhat) similar offerings.
    Thanks in advance... I'll try to be less annoying than some rather demanding newbies I've seen around [​IMG].
    P.S. 'subwoofer' is not recognized by the spell checker for the Home Theater Forum. Struck me as ironic [​IMG].
     
  2. Jack Gilvey

    Jack Gilvey Producer

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    With experience, you do get a general feel for what a driver can do by looking at the T/S parameters. There is a vast array of drivers on the market, but this forum is very good for bringing those that are worth attention to the top.
    I don't have a lot of experience with multi-way speakers and crossovers, as I prefer the full-range route, but my personal "filtering mechanism" for sub drivers (which seems to be your interest) would be a low Fs (~20Hz), low Qts (~0.4) and reasonable Vas . There's an increasing number of really good drivers entering the market, the likes of which would have been extraordinarily expensive a few years ago. Fairly low-priced offering from Adire, Stryke, PE etc. are good examples of what the modern enthusiast has to work with.
    quote: Thanks in advance... I'll try to be less annoying than some rather demanding newbies I've seen around [/quote]
    You're already OK in my book, then, and rather perceptive. [​IMG] Some seem much more ready to "teach" than to learn.
    What type of project do you have in mind, as far as budget, size, performance goals?
    [Edited last by Jack Gilvey on July 12, 2001 at 09:07 AM]
     
  3. ThomasW

    ThomasW Cinematographer

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    Brian
    Welcome to HTF
    Chosing drivers is a wierd set of compromises. Any driver must have the desired performance characteristics (yes this is primarily the T/S parameters). Then it must be in the desired price range. If two drivers have the same or very similar performance characteristics; and are similar in price, then I chose by mfgr.
    One reason you see so many references to the Adire products is that they are an extremely good value for the cost, the performance is very good. Also the boys at Adire provide some of the best technical support/customer service in the business. They will literally help the customer custom design a personalized enclosure. In addition their drivers are a "known" item, they perform as per the published specs. In this business it's not unusual to receive a driver that tests out different than the published T/S parameters. This isn't the case with Adire products
    Hope this helps
    ThomasW
     
  4. Brian Bunge

    Brian Bunge Producer

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    Jack,
    That's how I decided to go with ACI's SV12. It has an Fs of 17.5Hz, Qts of .395 and Vas of 250 liters. These specs are somewhat similar to the Shiva (except the Shiva's Vas is 151 L), which is highly respected around here. I went with ACI long before I had heard of Adire but they are both very respectable companies.
    I've stuck with ACI for most of my DIY stuff since building my first SV12 sub. In this respect I guess I've gone more on company loyalty than anything else. ACI hasn't let me down yet!
    Nevertheless, I've been very tempted to take the Tempest plunge! But, I think my next sub project will be something along the lines of an 18" driver so I may take a look at what Adire will be offering in the future as opposed to ACI's SV18.
    Brian
    ------------------
     
  5. Dustin B

    Dustin B Producer

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    Another advantage to the Adire drivers is Adire provides a version of LspCAD that only works with their drivers. LspCAD is a very expensive by accurate program, and access to it allows you to do a much better job modelling your design. Plug in the Tempest or Shiva specs into another program and come up with a design, then see how the numbers differ when you do it in LspCAD. When you don't want to spend the money on software to get your design modelled as close to the real thing as possible this adds even more value to the Adire offerings.
     
  6. Brian J Dupuis

    Brian J Dupuis Second Unit

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    Thanks for the responses guys.
     
  7. ThomasW

    ThomasW Cinematographer

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  8. Brian J Dupuis

    Brian J Dupuis Second Unit

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  9. ThomasW

    ThomasW Cinematographer

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    Brian
    You don't double the volume of the box for an isobaric design. It's 1/2 that for a single driver. So this box is functioning as if the box were 124L.
    Yes it's mine, and yes there is a page, but it's not quite finished. I'll post a link tomorrow. Also there will be a stretch fabric grill cloth to cover the exposed driver.
    The last time I checked the XLS series there was something goofy about the T/S parameters, I'd need to look at them again because I can't remember exactially what it was.
    Also.... IMHO [​IMG] polycone drivers like the Titanic do not have a stiff enough cone. As a result you get cone breakup when trying to reproduce low bass. Drivers like the ones from Adire and the P.E. DVC clones of the Adire's have Kevlar epoxy bonded to paper. These are some of the stiffest cones I've seen in 40 yrs of speaker building.
     
  10. Jon Hancock

    Jon Hancock Stunt Coordinator

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    Uh, I see the little plastic doodads for clipping on the grille assembly- how do you get it on over the outside woofer? [​IMG]
    Seriously, a lot of good suggestions above for woofer selection. For selecting drivers for the rest of the frequency range, and choosing the system configuration, consider a few hopefully useful points:
    1). Operate drivers *within* their pistonic range. This is particularly critical in upper midrange and lower highs. Cone breakup and cones designed for gradual decoupling (curvalinear) in my experience don't convey they ultimate resolution in sound quality. In mid/woofer and mid/range drivers, good examples come from Eton, Focal, and Accuton. Look for "wrinkles" in the impedance curve (published or measured)- these are due either to cone or cabinet resonances. Stay away from the frequency bands where they exist.
    2) Select driver sizes and crossovers to achieve similar dispersion/directivity over the overal frequency range. Easier to say than to do. Look at off axis plots.
    3) If you don't plan on buying a pre-designed kit by someone reputable, expect to spend a moderate amount of money on measurement equipment and softare. CLIO Lite is a good starting point if money is an issue. If that's too exensive, you may want to stay with well designed kits.
    4) Room interaction is a critical issue- take it into account in the design if at all possible (woofer and mid woofer height above floor). Best of all, if you want to get a little out on the edge, consider a dipole bass design- it dramatically reduces room interaction in upper and midbass region. With more conventional systems, consider the use of a program like RPG Acoustics Room Optimizer for modeling room and listener locations, and optimizing LF respone considering both boundary mode and room mode interactions. At under $100, it's dirt cheap for the time and aggravation it can save you.
    5) Above all, have fun! This is a hobby, not regligion! Sometimes those of us who tend towards the intense forget that a little....
    Regards,
    Jon
     
  11. Jeff Rosz

    Jeff Rosz Second Unit

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    hello brian,
    if the wife wont go for that driver sticking out the side of the box, check out the design of the M&K subs atwww.mksound.com a lil more eye pleasing. good luck and welcome to the forum.
     
  12. Brian J Dupuis

    Brian J Dupuis Second Unit

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  13. ThomasW

    ThomasW Cinematographer

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    Brian
    Here's a link to info on the isobaric sub
    http://www.Klone-Audio.com
    Just click on the "Rava Too!" link. This is just barebones info so as to get something quickly uploaded for people to look at. Much more detail including CLIO measurements will be posted when available.
    Regarding the Peerless XLS drivers, the Qts for both is very low, and the Vas is relatively high. Plus the drivers are pretty darn expensive compared to the competition. Also I've never been a big fan of PR based subs. I've built and heard, what many consider to be the "better" of the PR designs, and find their transient response/bass quality to be lacking...
    Yes the M&K subs are isobaric configurations but they are also resistively loaded designs. This probably isn't something a novice would want to try to duplicate
    Regards
    Thomas
    [Edited last by ThomasW on July 13, 2001 at 06:58 AM]
     
  14. Jack Gilvey

    Jack Gilvey Producer

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  15. Brian J Dupuis

    Brian J Dupuis Second Unit

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  16. Jack Gilvey

    Jack Gilvey Producer

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  17. Brian J Dupuis

    Brian J Dupuis Second Unit

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  18. Jack Gilvey

    Jack Gilvey Producer

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    quote: I'm sure there's a point of diminishing returns here, so you don't want to overdo things, but anywhere between the 32l and 64l is the "sweet spot" for a Qtc between .7 and .6 and between good extension and better extension. Am I "getting it", or am I making invalid jumps in logic?[/quote]
    No, I think that's fair. A Qtc of .707, or "maximally" flat", will have the lowest F3 for a given driver, and good transient reponse. A Qtc of .577 (edit: actually 0.5), or "transient perfect", will have a higher F3, but a shallower rolloff, allowing more deep bass (and , of course, the transient superiority that the name implies). Some prefer higher (some car subs) and some prefer lower (Thomas' IBs). I think 6-7 is a good range, though. Some consider a very low Q (below 5) to be "overdamped".
    One thing I'm not particularly well-versed in is the effect of voice-coil heating when a sub is in operation. As I understand it, though, this phenomenon ,which occurs in medium to high-power operation, and can actually raise the Qts of a driver. Designing to a lower Q would be a way to avoid the sub rising above 7 in operation. (I think I've really simplified this, or just gotten it plain wrong [​IMG] ).
    I think that transient response really begins to suffer much above Q=.707, so you can see how beginning with a driver with a high Qts leaves little chance of winding up with a good sounding sub.
    [Edited last by Jack Gilvey on July 13, 2001 at 09:55 AM]
    [Edited last by Jack Gilvey on July 14, 2001 at 07:17 AM]
     
  19. Brian J Dupuis

    Brian J Dupuis Second Unit

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  20. Jon Hancock

    Jon Hancock Stunt Coordinator

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    One last grace note on the melody....
    Q is a reliabile indicator of transient response. Critically damped transient response occurs at a Q of 0.5. At this Q, at the Fb in the box, anechoic response is down 6 dB. With typical room gain and proper placement, response in room may be flat. This gives response that is comparable in tonal clarity and transient definition to IB sub, and pretty close to the same extension, without any extra "punch" that isn't in the original recording. If you want the most "ideal" response, this is the way to get it. Naturally, there are times one makes compromises in enclosure size and tuning due to other considerations, like space, but in my mind, this is the principle advantage of the isobarik, using the expense of an additional driver to provide something close to an ideal response profile in a small enclosure.
    Regards,
    Jon
     

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