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BMS Drivers

Well, my silly questions about mounting them were pretty silly, it only took about 5 minutes for the pair (BTW, I used lock-washers, with plenty of room). I set them up without the Behringer (waiting for the Fisher, to feed the BMSs with tubes), fed by the Sansui AU/TU-717. The first thing I noticed, obviously, is their efficiency, as you guys mentioned, so I adjusted the tone controls. Man, these things are sweet-sounding. :thmbsp: With the treble at 9:00 & bass at 1:00, everything just came together perfectly. The best sounding treble I've ever heard, excellent mids but no midrange shout, & it seems like everything's balanced just right, including the bass. I was kinda nervous about plunking down the money for these, but I'm glad I did, no regrets at all. :smoke:
 
"Without the Behringer," what are you using for a crossover?

You cannot run these full range.... :nono:
 
Zilch said:
"Without the Behringer," what are you using for a crossover?

You cannot run these full range.... :nono:
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LOL, I hope I don't ever lose THAT much of my mind. :D I'm just using caps right now, very similar to EPI/Genesis setup. 16 uF, so crosses pretty darn close to 1200 kHz or Hz, whichever one's right. :yes:
 
Cool! Had me worried for a bit there! :yes:

I have completed validating the compensation filters for 4552nd on 811B, but still have to do the schematics for everyone. Here are the curves, blue is the LCR tank filter I developed for 846B Valencia nearly a year ago, and violet is 30923 with R-2 = 20 Ohms. The results are very similar and flatten the response to within +/- 2 dB. You can see it requires only ~5 dB of compensation to accomplish this using BMS drivers. 30923 is ~1.5 dB brighter between 1.5 and 2.3 kHz:

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spaceman said:
The best sounding treble I've ever heard, excellent mids but no midrange shout, & it seems like everything's balanced just right, including the bass. I was kinda nervous about plunking down the money for these, but I'm glad I did, no regrets at all. :smoke:
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We're four for four, now, and the Zilchster is breathing easier.... :thmbsp:
 

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BMS Compensation Filters

Take your pick:
 

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Zilch said:
We're four for four, now, and the Zilchster is breathing easier.... :thmbsp:
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Well, it's not hard to take a calculated risk, on your recommendations, you know your stuff, & just proved it again. :thmbsp: Listened to "Breakfast With The Beatles" this morning, & turned the bass down to 9:00 to match the treble, & it's much better yet. I can hear everything very clearly, which takes some getting used to. :music:
 
811B vs. 511A

Does BMS 4552nd play lower on 511 than 811?

Not appreciably, and the overall response is a bit smoother on 811B:

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spaceman said:
Listened to "Breakfast With The Beatles" this morning, & turned the bass down to 9:00 to match the treble, & it's much better yet.
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Add one of the compensation filters above, and it's going to get even better.

I'd do the modified 30923 T- Filter. It's cheaper (~$12.50 a pair) if built using Dayton caps and 10W NI resistors.

spaceman said:
I can hear everything very clearly, which takes some getting used to. :music:
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It's going to be interesting to know if anyone feels that flattened Altec response is as dull and boring as is oft postulated here on AK.... ;)
 
Zilch said:
Cool! Had me worried for a bit there! :yes:

I have completed validating the compensation filters for 4552nd on 811B, but still have to do the schematics for everyone. Here are the curves, blue is the LCR tank filter I developed for 846B Valencia nearly a year ago, and violet is 30923 with R-2 = 20 Ohms. The results are very similar and flatten the response to within +/- 2 dB. You can see it requires only ~5 dB of compensation to accomplish this using BMS drivers. 30923 is ~1.5 dB brighter between 1.5 and 2.3 kHz:

attachment.php


We're four for four, now, and the Zilchster is breathing easier.... :thmbsp:
Click to expand...

Hi Mr. Zilch:

I've been lurkin' on this thread since its beginning but your post above has gotten my curiosity up.

When you made these measurements with the two types of comp networks, did you include the upstream Xover too? The reason I ask is that thru experimental meas and modeling, I've found there's significant interaction betw the comp network and the Xover. IOW, what may measure flat with the driver/comp network driven directly by a low impedance source becomes less than flat when the Xover is inserted betw the source and the network/driver. Lots of tweaking is then reqd , at least IME.

Interestingly, as you noted, I too find the bridged "T" network can be made to closely simulate the original parallel resonant network...on paper...meas forthcoming. However, tentative resistor values are different than your suggestions. If meas are promising I'll probably end up leaning towards the "T" network for four reasons:
1. It presents a much more constant impedance vs freq to upstream Xover compared to parallel resonant circuit. Hopefully, no impedance correction network will be nec.
2. It's less complex than the resonant network...much less complex if one includes impedance correction.
3. It's much less costly than the resonant network. Priced low gauge air core copper coils lately? Ouch.
4. It's inherently non-resonant. For reasons I can't properly convey, I have a fear of electrically resonant speaker Xover circuits.

Now, besides the 4550 vs 4552 issue, I have the "T" network vs the resonant network issue to contend with. I'm developing a new appreciation for speaker/Xover design.
 
Hi, Steve!

Spaceman's using the same Behringer analog active crossover as I have used to measure the compensation networks, so there's no intervening passive crossover involved. That's not to say different amps will necessarily play them precisely the same, though.

The bridged "T" filter was used by Altec with various passives, and incorporated into the Model 19 and other stock crossovers, so, while those crossovers do behave somewhat differently in detail than what I have shown above, I'm confident it will provide the requisite compensation.

I look forward to learning more from the work you are doing. Crossover design at this level is indeed challenging! :thmbsp:

Note 1: I just measured 4550 vs. 4552 on 511A, and 4550 does indeed play a bit lower, though not substantially so. For 800 Hz, it's a tradeoff between stronger performance in the crossover region and perceived improvement in the VHF with 4552nd. In any case, 500 Hz is not happening with these drivers, even on 511A horns.

Note 2: Did you see Skywave doing the "Helper" woofer thing with his 9844s? I'm not sure what the outcome of his (semi-) final testing and evaluation of the alternatives will be, but it certainly has been interesting, particularly how Altec used N800-F with 8-Ohm drivers.... :yes:

Note 3: As a crossover designer, you might be interested in this thread:

http://audioheritage.org/vbulletin/showthread.php?t=20426
 
I had a chance to listen to the BMS drivers tonight for about an hour, I thought I'd throw them a curve by playing some Willie Nelson "Cowboy" songs from the Electric Horseman movie. This is the first time Willie's "S's" didn't get smeared, I found it super enjoyable to not hear those raspy sand paper scraping S's at the end of some of his words when he sings. I can't believe how nice these drivers sound, anyone from the group buy ready to sell me their pair?? :scratch2:

willie.jpg


Disc 3;
1. My Heroes Have Always Been Cowboys
2. City Of New Orleans
3. On The Road Again
4. Mamas, Don’t Let Your Babies Grow Up To Be Cowboys
5. Whiskey River
6. Red Headed Stranger
7. South Of The Border
8. So You Think Your A Cowboy
9. A Horse Called Music
10. If You've Got The Money, I've Got The Time
11. Midnight Rider
12. Good Hearted Woman
 
Willie's Mr. Smooth, he is. :thmbsp:

No trading allowed in this thread Wojo. :nono:

[I kinda think it's moot, tho.... :p: ]
 
Zilch said:
Hi, Steve!

<snip>

Note 2: Did you see Skywave doing the "Helper" woofer thing with his 9844s? I'm not sure what the outcome of his (semi-) final testing and evaluation of the alternatives will be, but it certainly has been interesting, particularly how Altec used N800-F with 8-Ohm drivers.... :yes:

Note 3: As a crossover designer, you might be interested in this thread:

http://audioheritage.org/vbulletin/showthread.php?t=20426
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Hi Zilch:

Yes, I saw Skywave's work with the helper woofer concept. Actually, I've seen this concept used in a few commercial speakers also. I've got a pair of B&W DM1400s with two 7" LF drivers and one HF soft dome in a sealed box. When current, they were usually refered to as "2-1/2 way" speakers because the bottom LF driver comes in at much lower freq than upper LF driver. The xover also incorporated some form of electronic time alignment. Net result is that the xover is extraordinarily complex for a relatively low end speaker.

One issue I'd be concerned about with Skywave's arrangement is the unknown effect of having what amounts to a passive radiator in place in addition to the port at freq above system resonance. What about phase shift introduced by the inductor as the aux LF driver begins to rec drive? Too many things for me to get my mind around.

I finally got around to reading that thread. Seems that there was an underlying or secondary agenda regarding what pros do with issues being discussed or something like that but the moderator cleaned it up so good I couldn't really figure out what the underlying issue was.

Anyways, I was mildly surprised at how the pros were able to take images of driver/horn response you provided, somehow plug this info into LEAP and come up with compensation circuit topology and part values. And then they comment on the output as if they'd actually heard the suggested circuit/driver combinations.

One observation is that LEAP seems to be geared towards the RC shelf type filter for basic response shaping, much like the Altec bridged "T" filter. Then it adds a pile of additional series resonant filters across the driver to tame peaks. There also seems to be a desire to incorporate the basic xover design into the compensation scheme. IOW the order, alignment and specifc xover F are the main part of the compensation with the additional filters for tweaking. OTOH, I could have "misinterpretated" that part because I find rambling, moderator edited threads sometimes difficult to follow.

Oh, based on what I read in that thread, the label "designer" is kind. "Grasshopper" is probably closer to the truth.
 
The designer supplies the topology, Steve, and in that case, it was ultimately me with "Hard Way," after a couple of false starts.

LEAP then computed the requistie component values to generate the desired output from the raw driver response, which I also supplied. You see the resulting measured response of the actual built circuit there, success on the first try.

It works great with the active crossover I used to conceive it, but I'm having to tweak a bit once I converted to passive and installed L-Pads.

LEAP will work with whatever design is specified; the T-filter bias derives primarily from my having done that part. :yes:
 
Zilch said:
Willie's Mr. Smooth, he is. :thmbsp:

No trading allowed in this thread Wojo. :nono:

[I kinda think it's moot, tho.... :p: ]
Click to expand...
Nope, no buying or selling, just trying to convey that I really like them!! Who knows, maybe once people get their tax returns they'll want to start another thread for another group buy??

Tonight I'll try a remastered Zepplin CD, Stairway to Heaven and Going to California are my favorites for testing drivers with Led Zepplin!! :music:
 
dgwojo said:
Nope, no buying or selling, just trying to convey that I really like them!! Who knows, maybe once people get their tax returns they'll want to start another thread for another group buy??

Tonight I'll try a remastered Zepplin CD, Stairway to Heaven and Going to California are my favorites for testing drivers with Led Zepplin!! :music:
Click to expand...

Well crap...I'm gonna get killed for this but count me in on a duplicate group buy if it comes to fruition...I guess I can have them delivered to the office!

Russellc
 
Russellc said:
Well crap...I'm gonna get killed for this but count me in on a duplicate group buy if it comes to fruition...I guess I can have them delivered to the office!

Russellc
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They're so small she'll never see them!! :yes:
 
Zilch,
Would the 4540ND's work good on these?? I have few to chose from in my living room!! :music:

SLT_20080330_01.jpg
 
JRX?

That's the $10 El Cheapo JBL PT Waveguide in those.

I do have a comp filter worked out for 4540nd, tweeting sweetly above 2 kHz.

Borrow one of those waveguides, put 4552nd on a throat adapter and drive it with a Model 19 crossover. In about two minutes, you'll be borrowing another one. :p:

With Selenium D220Ti on them, they're EconoWave, of course. Same filter will work for those, as well.... :thmbsp:
 
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