Closed Thread
Page 3 of 29 FirstFirst 1234513 ... LastLast
Results 31 to 45 of 427

Thread: Quick & Dirty 4430-Inspired Two-Ways Part II

  1. #31
    Administrator Mr. Widget's Avatar
    Join Date
    Apr 2003
    Location
    San Francisco
    Posts
    8,274
    Quote Originally Posted by Zilch
    Mr. Widget has CLIO FR curves on the three different crossover component combinations we have tried, which he'll likely post here soon. You'll see the results of the tweaks we've tried so far at higher resolution than I can achieve with simple 1/3 octave RTA.
    Sorry about the delay. Here is the plot of the three networks.

    Widget
    Attached Images Attached Images  

  2. #32
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,985
    And here's the filter sims and driver/horn response curves. Looks like we've got some control here.

    Two peaks to tame. One of them's kinda random, tho.

    We've certainly got the HF extension we hear and see on RTA. Maybe a little too much, even.

    Just need impedance curve now. Gonna be a statistical exercise, n=6....


    Edit: What's going on here?

    Top graph shows computer simulations of the "AM" high frequency crossover design we're using with 2431H drivers on Progressive Transition (PT) waveguides. Three versions are shown, reflecting minor circuit "tweaks" (discussed earlier here) to lower the high pass frequency slightly for more seamless mating with low frequency driver (2235 or LE14) response as filtered by the orange curve at the left there.

    Second graph is actual measured frequency responses of 4 different 2431H drivers mounted on PT-F (compact) waveguides.

    Bottom curves are the results just posted by Mr. Widget, the three crossover tweaks as they are reflected in actual performance on 2431H #1 (red curve in middle graph). What we've done with the crossovers, as shown in the computer simulations, is apparent also in the actual performance of the driver and horn.

    Driver/horn response and crossover filtering combine to provide "precipitous" rolloff below 1 kHz.

    Further improvements will likely have to be approached statistically, as there is considerable variability in driver/horn performance in the VHF region, as shown in the second graph. This particular driver/horn exhibits a substantial peak at about 13.5 kHz (what Guido was referring to from the JBL specs?), and runs maybe 2.5 dB too "hot" above that, assuming flat response is the objective....
    Attached Images Attached Images    

  3. #33
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,985

    A little more explanation:

    For many, the brain glazes over at the sight of response curves and crossover schematics. Perhaps this little bit more information will help clear the hyper-technical fog over this:

    To make the HF driver "play" with the woofer, we could power them each from a separate amp (biamp) and apply the requisite boost in the high frequencies to level out the HF response using active equalization. We'd rather just hook them both to the same amp and have them work right together, tho, and that means use a passive filter crossover network. 4430 does it separately for mid- and high-frequencies; we're doing it "all-in-one" here.

    Since passive networks don't add any power to the system, we can't boost anything, only cut. Fortunately, HF compression drivers such as the 2431H we're using here are WAY more efficient than the woofers we're mating them with. 2235H has a sensitivity of 93 dB, for example, and 2431H is up around 110 dB (actual spec unknown).

    Thus, we have something like 17 dB of excess SPL available in the HF driver to do the requisite deed when driving both woofer and HF driver from the same amp souirce. All we have to do is progressively attenuate the power delivered to the 2431H from 20 kHz downward to match the SPL of the woofer at the crossover point (1 kHz, in this case). The inverse of the driver response curve above tells us, generally, what the crossover must do to accomplish this, such that the end result is a seemless flat response throughout the range of interest.

    The crossover voltage drive curve (top graph) is what we're using to do it. We try to adjust the values of the components in the filter to "shape" the curve (the resultant attenuation varying with frequency) to make the HF driver perform as desired. You can see we have essentially 0 dB attenuation at 20 kHz, there. Response at all frequencies below that is cut by varying degrees, as required, to yield flat output.

    The result is shown in the combined response curve (bottom graph), where we measured the actual performance of crossover, driver, and horn playing together. Looking at the various curves, we only use up ~13.5 to 15 dB of the available 17 dB HF driver "headroom" to do it here. That's a good thing; if much more were required, we'd run out of SPL and end up giving up response somewhere.

    Well, that's the "Quick and Dirty" synthesis of what's going on with this: Graph A + Graph B = Graph C = sounds GOOD!! Hope that helps.

  4. #34
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,985

  5. #35
    Senior Member Guido's Avatar
    Join Date
    Apr 2003
    Location
    Germany
    Posts
    2,495
    Well explained! It's good for our not THAT experienced members.
    BLS Reference on Passlabs XA 30.5 + Everest DD66000 clone on Pass XA 100.5

  6. #36
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,985
    Quote Originally Posted by Guido
    It's good for our not THAT experienced members.
    Yeah, that'd be ME!

    It's only my second pass down this path....


    Infredible was just here with his stack of astounding test disks puttin' the Q&D's through their paces. I'm pleased to report that no apparent damage occurred to the either the house or workshop. Gonna take a day or two for me to decompress....

  7. #37
    Senior Member Guido's Avatar
    Join Date
    Apr 2003
    Location
    Germany
    Posts
    2,495
    Quote Originally Posted by Zilch
    Infredible was just here with his stack of astounding test disks ....
    Which one, which one
    BLS Reference on Passlabs XA 30.5 + Everest DD66000 clone on Pass XA 100.5

  8. #38
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,985
    Peggy Lee, Dave Crusin "Migration" (see thread "What's playing now"), Andreas Vollenweider....

    Infredible's complete test kit is proprietary, of course; the ride'll make yer nose bleed.

    Johnaec brought lotsa Little Feat, others, mostly new to me, expanding horizons here.

    Mr. Widget has some good ones I gotta get, too....

    It's great fun when forum members bring their favorites to try. You get to hear lotsa different stuff you wouldn't normally hear on your system, and you can turn them on to your own arcane "specialties" at the same time.

    Mine? Presently "Red Hot & Blue" Cole Porter compilation, Chico Science (Brazilian), "Amused to Death" (a reminder not to mix politics and rhythm), "Up" (which I don't understand), Brian Ferry "Frantic," and an array of Pink Floyd, of course.

    Back to regular programming AFTER this brief musical interlude....

    ["Soon be oh vah, soon be oh vah...."]

  9. #39
    Senior Member stevem's Avatar
    Join Date
    Mar 2004
    Location
    New Jersey, USA
    Posts
    278

    PT Waveguides

    I too have been playing around a bit with some of the various JBL waveguides, so for what it’s worth, here are some of my first impressions. To provide a frame of reference, my speakers are a three way tri-amped design consisting of a pair of 1401Nd woofers per side in a ported enclosures, a 2012H mid in a sealed enclosure (I plan to try ported soon), and a 2450SL compression driver on a 2332 horn. This horn and driver were designed together, and there is no “transition tube” as found on most JBL HF drivers. The 2450SL is almost identical to the 2451, and similar to the 2450, except this driver does have the transition tube.



    My listening room is not very good acoustically. It is 12’ wide by 24’ long, which is an even multiple and not a good thing. There are big built-ins at one end, which shorten the room by about 3’ making it effectively 21’ long. The real killer is the ceiling, which is only 7’2’ high. The walls, floor and ceiling are very rigid, which produces a lot (too much) bass. I have diffusers and bass traps in strategic places, which helps a great deal. The floor is carpeted.



    I wanted to try out the PT waveguides because when I read JBL’s technical paper on them, I could see that they are also designed to be used with drivers without transition tubes. I think they even did some of their testing with the 2450SL. Before my current speakers, I was using a DIY 4430 system with the 2344A and 2426H for the HF and a 2235H for the LF. I decided to try the 100x100 degree 12”x12” waveguide first, as that was the same size and dispersion pattern as the 2344A in my prior system. I found the tonal balance of this set up surprisingly similar to the 4430 clone, but with more detail and immediacy. I realized, though, that I preferred the sound of the 2332, probably because it’s pattern is narrower (I think it’s about 90x50 degrees) and doesn’t bounce off the side walls as soon. It also seems to bounce off the ceiling far enough back for the first reflection not to reach the listening position. This pattern gives instruments a warmer and more natural tonal balance. I also didn’t like the 100x100 as much because the highs seemed farther away from the midrange (because it’s larger than the 6”x12” 2332), and the speakers become physically higher. They didn’t sound as coherent from my listing position.



    The next waveguide I tried was the 60x40 degree 6”x12” unit. (Zilch had mentioned in an earlier post that the 90x50 degree 6”x12” unit is not available, and he appears to be right. Too bad because this one is probably just right for me). This unit has a similar spectral balance as my 2332 horns, in that it's warm sounding, but they are a bit to “beamy” and up-front sounding for my tastes. The sound character also changes when you stand up, or walk to the back of the room. It’s a very clean and detailed sound, and some of you may like it, but to me it’s a little too much like wearing headphones. By comparison, the 2332 sounds more laid-back, with no beaming at all. I can’t say that the 100x100 unit beamed, but I was more aware of the highs and where they were coming form. This might just have been due to the added distance from the mid. I’m guessing the the more diffuse sound from the 2332 is caused by the diffraction slot used as part of the horn’s design. Non of the PT waveguide use this feature, and this may account for some of their “more direct” character



    There is also a 90x50 degree horn in the 12”x12” size, but I’m a little reluctant to try it because of the height issue. I would like to try a 6”x12” version, but as I said, it’s not in production.



    For EQ, crossover and delay I use a BSS Omnidrive FDS-266t, which is a great unit. I measure the speaker’s response using an Audio Control SA3050A spectrum analyzer and pink-noise generator. My amps are all Bryston ST series. Of course, the above opinions are purely subjective, and are heavily influenced by my listening room and tastes. As always YMMV.

  10. #40
    Administrator Mr. Widget's Avatar
    Join Date
    Apr 2003
    Location
    San Francisco
    Posts
    8,274
    Very interesting info.

    My current horns are of a narrower type as well and seem to give a more coherent image. Mine are 80° X 30°. I have no idea if this is why I like them or not. My previous horns which I also really liked were the 2397s which are quite wide in dispersion... they are narrow vertically though... just some ramblings.

    Widget

  11. #41
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,985
    With that low a ceiling, the 90° x 50° is likely the better choice. I do have some alternatives coming in with that pattern, but we need to keep after them to make the PT-F version. I'll report on the PT-H as soon as it arrives.

    I agree, the 60° x 40° is "beamy." If I had a HT setup, it might be just the ticket.

    You might want to try the really cheap 90° x 50° PT waveguide for 1" drivers. It'll screw directly on your 2426H's. Part #338800-001. $9.00 each, IIRC.

    Nope, $9.90. http://www.jblproservice.com/pdf/Hor...%20List%20.pdf

    For clarity, you're using 2450SL, not 2431H, correct?

    Several other members have commented upon how remarkably similar the PT waveguides and the 2344A here sound....

  12. #42
    Senior Member stevem's Avatar
    Join Date
    Mar 2004
    Location
    New Jersey, USA
    Posts
    278
    Yes, I'm using the 2450SL for the highs. I should also mention that this driver with the 2332 horn takes 10db of boost to flatten it out to 20khz. With the PT waveguides, it seemed to require considerably less boost, and I'm not sure why that should be. Any ideas?

  13. #43
    Administrator Robh3606's Avatar
    Join Date
    Apr 2003
    Location
    Destiny
    Posts
    7,467
    Different horns will require different compensation. I am not familiar with either but from you description in sounds like a wide dispersion CD horn VS. a more tightly controled patern horn. If you look at the biradials in general the wider the patern them more electrical compensation is needed for flat on axis response. Look at a 2344 and a 2370 at two extremes. The 2344 is 100x100 and needs a good amount of compensation to get flat on axis response. Basically the curve for this horn mirrors the compresion driver without a horn. On the 2370 it's 90x40 and the response is much flatter without any compensation in the crossover. Starts rolling off around 7-8k which can be adjusted to increase output in the last octave with the addition of a shunt capacitor say 1uF in the crossover like the L200B crossover.


    Rob

  14. #44
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    9,985
    Quote Originally Posted by stevem
    With the PT waveguides, it seemed to require considerably less boost, and I'm not sure why that should be. Any ideas?
    As Rob says, each horn design requires different compensation. PT's are "hotter" around 8kHz than 2344A, for example, and even within the family, the 60° x 40° more so than the 100° x 100°.

    I used AutoEQ on the Behringer UltraCurve with a "stock" PT crossover (from AM6212/00) to get them playing close enough with 2431H to compare sonically....

  15. #45
    RIP 2009
    Join Date
    Feb 2004
    Location
    Rohnert Park, CA
    Posts
    3,790
    OK - here's a quick 3D version of Zilch's "trapezoid" cabinet. Until I get something better to use I plugged in a 2332 horn, (same size opening as the drawings Zilch gave me), and a 15" LF. I'll try to get some renderings with materials instead of plain colors sometime in the near future.

    John
    Attached Images Attached Images  

Closed Thread

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Quick & Dirty 4430-Inspired Two-Ways Part I
    By Zilch in forum Lansing Product DIY Forum
    Replies: 449
    Last Post: 03-05-2006, 04:41 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts