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Thread: New digs for a classic system

  1. #16
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by JohnK View Post
    In any case, your find is absolutely splendid. It's wonderful to see vintage systems in their original environ.


    I agree... I love that old stuff. Thanks for sharing it with us!


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  2. #17
    Senior Seņor boputnam's Avatar
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    Quote Originally Posted by Beowulf View Post
    ...here's how it sounded right before it was dismantled . . . the 075s were intermittent (just look at the L-Pads!) and the traces were taken without them.
    That, sir, is a damned respectable frequency response. I take it, without much, if any, EQ? Wow. There are guys here who would skin their teeth to get anything close to that.

    Those 375's are just there, unsupported at the motor? Aren't they like 20-something pounds?
    bo

    "Indeed, not!!"

  3. #18
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    Quote Originally Posted by boputnam View Post
    Those 375's are just there, unsupported at the motor? Aren't they like 20-something pounds?
    Those horns are very solid and as long as the wall panel is as well, 20-30 LBS. is no big thing.

    If they were mounted like that in cabinets, maybe???

    But again if you have handled those horns they are very solid with thick walls

  4. #19
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by boputnam View Post
    That, sir, is a damned respectable frequency response.
    Yeah... all the way out to 8KHz.

    Actually it is outstanding especially when considering it's vintage. I guess the drop off above 8KHz is due to the 075s being intermittent or being way off axis. I wonder how well that lens worked with them?


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  5. #20
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    Quote Originally Posted by Mr. Widget View Post
    . I guess the drop off above 8KHz is due to the 075s being intermittent or being way off axis.
    Widget
    Yeah, the L-Pads were crackly, and when the 075s were tested later, one side was kinda krispy, and the other side had very little output . . . as far as the trace is concerned, there was unlikely to be any sound at all coming from the 075s. And yes, this is without any EQ, about 25 degrees off axis from the 537-512.

    The 375 as originally wired had no LPF, that is, it was driven directly from the HF side of the N500. Its output to me looks exactly like some of the published data I've seen for the 2440, clearly showing two slopes . . . but with the upper one shifted down almost an octave . . . I'm attributing this to probable metal fatigue and/or corrosion in the original diaphragm surround, lowering its resonant frequency. I originally thought that the 250Hz peak might have been an artifact of the transition from the D130s to the horns, but looking at the photos makes me realize that the width of the bookshelves corresponds pretty closely to a 250Hz-ish wavelength, and this is most likely to be a resonance from this cavity.

    There are two things that really impressed me in this trace - first was how well the sensitivities of the D130s and the 375/537-512 matched each other - there's no attenuation on the horns. The other thing was how nicely the bass roll-off of the D130s seemed to be offset by their corner-loading in the room - below 125Hz-ish. Subjectively, it still sounds a bit bass-light, especially for a system with eight 15"s . . . but for mid-20th-century classical recordings (what it was built for), it's not really an issue, especially with judicious use of tone controls . . . which nobody frowned upon back then. What I was truly stunned by was how good this system sounded with speech . . . my jaw dropped when I heard an NPR newscast.

  6. #21
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Beowulf View Post
    What I was truly stunned by was how good this system sounded with speech . . . my jaw dropped when I heard an NPR newscast.
    World's greatest radio speaker?

    For years I had a pair of custom speakers out in my shop that were made up of Dynaudio, Focal, and B+W components... and a Dynaudio sub. When my audiophile friends would come over they would tease me about the overkill of the system since it played NPR about 90% of the time. Now I think I may have to upgrade to a new one now with 4 15s per side.


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  7. #22
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    Found The Article. It was wriiten by David Beatty. It describes Dr Lester Blender & system. There are pictures of two systems, the earlier mono system & the stereo system. The house is the earlier house. It is the November 1958 issue. I sort of figured that there probably was only one system like that in the world, & you found it!


    PM me & I'll send it to you.


    JK

  8. #23
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    The End is Near

    Finally, all of the cabinetry is completed, and most of it is installed, including the speaker cabinets. Couldn't be happier with the results . . . especially the perfect 1/4" gap all around the speaker cabinets themselves, which seems to have thoroughly decoupled them from the rest of the woodwork. The horizontal plane of the 2382s and the 077s ended up exactly at ear level when seated.

    It's really interesting how HUGE the speaker cabinets are when they're sitting out in the open . . . something that 'normal' people would never have in their living room. But put a bunch of custom cabinetry around them, and they suddenly seem "very small", in the words of the homeowner.
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  9. #24
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    So now I'm building crossovers. I originally thought that I would use 2nd-order filters, but after taking some measurements and playing around with a couple of different active crossovers I have lying around, I think that 4th-order slopes seem to work much better. The trace below is just the D130s and the 375/2382, crossed over at 818 Hz, 4th-order Butterworth alignment, wired out of phase with each other, with 12dB attenuation on the horn.

    Also, since the mid horn has its own steep rolloff, I'm thinking that I'm going to run it without a LPF, and simply bring in the 077 at a (kind of) complementary slope.
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  10. #25
    Dang. Amateur speakerdave's Avatar
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    That's a nice looking installation. What is the crossover frequency between the 2235's and D130's. Also, I'm surprised that 2 D130's are necessary. Could you go into the reason for that? I do like the idea of a large diaphragm working the midbass, but I would have thought one would be enough over a pair of 2235's.

    David

  11. #26
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    Well, the main reason is that the old system had four 15" drivers per side, so the new system has . . . four 15" drivers per side. It did occur to me to halve the number of D130s, but once enough room was given to everything else, it wouldn't have really saved any space. And I had already sold the homeowners on so many other changes and a huge custom cabinetry bill . . . and it would have seemed weird to then justify why we weren't using all the speakers that we had.

    In a purely technical sense, having two probably provides a bit of vertical pattern control in the upper bass, reducing the effect of early reflections off of the floor. And if you don't buy that, it at least increases sensitivity, and since the crossover between the D130s, 375, and 077 will be passive, that's definately a good thing, as the 375/2382 is still 12dB hotter than the D130s.

    On the negative side, I noticed that when the D130s were crossed over to the horn at, say, over 1K, they produced some weird phase discontinuites (both audible and measurable) that I'm attributing to the interaction of the higher-frequency response from the two metal domes . . . this was one of the main reasons why I decided to go with fourth-order slopes, and keep the transition point just above where the 2382 starts to poop out. In retrospect, this could maybe have been avoided by putting an aluminum dome on the upper driver only, but I'm actually quite happy with the transition region as it is.

    As far as the crossover point between the 2235s and the D130s is concerned, it will be in the range of 90-125, but since this is made with an active crossover, I won't have to decide until the final tweaking. The D130s actually seem to extend lower than I anticipated from the calculated box tuning, so the deciding factors will probably be much more due to room interaction than driver response.

  12. #27
    Dang. Amateur speakerdave's Avatar
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    Thanks for that. I've also found I like to lower the crossover point when using multiple woofers and have wondered if it is because of phase issues in the higher frequencies they cover, that is higher than the range in which effective acoustic coupling is occurring.

    Perhaps the unexpected lower frequency response in the D130's results from acoustic coupling, which I think would increase response gradually in that setup from about 300 Hz down to about 150, and would be full from there downward.

    David

  13. #28
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    By 'acoustic coupling', I take it that you're referring to the coupling taking place in the airspace immediately in front of the woofers? I suppose that that could be . . . but for some reason I associate this phenomonon more with higher SPLs - like in big line arrays. But those D130s are indeed very close to each other, and close to the floor . . .

    I also have a bit of skepticism about the TS parameters I used for the calculations . . . since what I actually have are 16-ohm E130 cone kits in old Alnico D130 frames, and the published D130 TSPs are for 8-ohm versions. I tried to make some educated guesses about what would be different, which is why their box is bigger than a calculated Butterworth alignment for 8-ohm D130s. And there's the added bit that TS calculations only really work as intended if the driver behaves as a piston, and I thought the whole point of the "curvilinear" cone was that it doesn't. In contrast, the "2235" cabinet seems to measure very consistently to what the TS parameters predicted.

    But whatever the cause, in this case the deviations from the predicted behavior is actually an improvement . . .

  14. #29
    Senior Member jblwolf's Avatar
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    Great post!!
    I'm with Chad on the use of a lens on a 075,any comments on the affects of a lens on a 075?

  15. #30
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    outcome?

    So was there any followup from BeoWulf on the final outcome of this project? It is fascinating from start to finish! As an aside, I believe that David Beatty (claimed to be) the "oldest" JBL dealer in the country. Or is my memory faulty?

    I do remember their slogan: "Get the best and cry ONCE"

    I wonder what Dr. Blender paid for it all in the beginning, too. It would certainly be priceless to him, with his career cut short by MS and being confined to a wheelchair.

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