Originally Posted by Zilch
Sure:
http://sound.westhost.com/beginners.htm
I have parts on order for the BMS 455x/846B compensation filter. As soon as they arrive (later this week, probably,) I'll build one up and test, then I'll post a parts list so anyone can build a pair.
Rock on Zilch!Sounds like a plan.
Jackgiff and Zilch I don't fully understand the expalnation about the fliter used for the BMS drivers .
Jackgiff wroteThe plot Zilch published seems show quite the opposite a drop in the midrange and a boost at HF. If not, how a 3dB boost in the midrange could sound dull and flat ? And the 3 dB boost at 20kHz is surely inaudible for most of us (and the comparo listeners?).The series connection across the driver actually gave a 3 db boost to the midrange, and cut the HF at 20 KHz by 3 db. Getting it wired correctly makes a large difference.
Do I miss something?
Chris
Yes, I think so.
The plot at post #730 is the voltage drive, not the frequency response.
The intended curve is the yellow. Green is what the incorrect connection provided for the Comparo.
There was a communication problem, as much on my part as Jack's. A parallel notch filter is connected in series with the driver. A series notch filter goes in parallel with it.
The complete compensation filter is a parallel notch providing the primary compensation (the yellow curve) plus a series notch squashing the 19 kHz spike.
None of this is to say that the participants would necessarily have liked the result better; it's just Mr. Widget's caveat at work here: "If all the systems are working properly...."
We're still working out how to proceed in addition to fixing that part. Jack is getting set up with measurement instrumentation which will "normalize" the test conditions for the several examples under evaluation.
Both of the correctly wired Vals with BMS 4550 drivers are now back in the house, and playing as I type. They do sound much fuller in response than before. Probably the reason I previously liked the BMS without the filter was because the series connection across the driver cut the HF range. Compared to the other Vals, it lacked the "sizzle." And it also didn't cut the midrange enough. With the drivers now playing flat, adding the filter definitely helped their response.
+3 db in the midrange and -3 db in HF doesn't sound like a really big deal, but the difference is obvious. Even with the bad connection, the BMS sounded better than stock, which is down some 20 db in HF, but it wasn't up to the other Vals in the comparison. I believe it will now hold it's own with the competition, if not prevail. Storm, Andy, Jeff and Tom, if any of you are going to be in Prescott, please let me know. I would like to have you over for a beer (or Coke, in Storms case) and a listen. I think you will find the BMS Vals much improved. You may not like the sound of Mylar diaphragms, but they are nice in my book.
Jack Gifford
The proof will be in how you decide to upgrade your third pair. I suspect you'll want to do more comparative listening to decide that, now, along with the measurements.
As you know, I like the smoothness of the Mylar. There's also the "flatness" issue. Some long-term Val owners may prefer more forward midrange like they're used to. The compensation is easily adjusted to provide that. In fact, an additional control could be added for that capability, to adjust the "slope" of the compensation as in Modell 19....
All, I've been running a signal through the system since Sunday and it's changed. I feel everything's pretty well burned in now and the BMS drivers sound even better (better transparency). That's probably as much a function of the speaker cable burning in too. Anyway, I totally agree that the BMS drivers need compensation. They are definately more fwd sounding now, and while not "shouty" like the stock drivers, they are a bit in your face. Jack, I guess you're pretty happy with the results of the Zilch mods, so I think it's time to pile on. Any recommendations on parts manufacturers? I'm think i'll go with the Sonic Craft caps for the x-over. Thanks.Rock on Zilch!
The BMS drivers sure do change the characteristics of the Vals, don't they? The LCR filter flattens out the response curve, and makes them much more civil. The pair of mine which has the BMS drivers is in the master bedroom, and I just turn them up so they are audible in the living room. Pretty fine sound. The highs are not so overly dominant as some systems I have heard, but the detail in the HF is there. I just used the Dayton metallized polypropylene series available from Parts Express. I don't know whether the quality of the high priced capacitors is worthwhile, but the Daytons are well worth the price. I am sure you will love the BMS drivers even more when the FR is controlled. I sure love mine.
Jack Gifford
Jack, yes they do....very much so, it's different. You are right, they really do carry sound. I think these would do well in a big, big room.The BMS drivers sure do change the characteristics of the Vals, don't they? The LCR filter flattens out the response curve, and makes them much more civil. The pair of mine which has the BMS drivers is in the master bedroom, and I just turn them up so they are audible in the living room. Pretty fine sound. The highs are not so overly dominant as some systems I have heard, but the detail in the HF is there. I just used the Dayton metallized polypropylene series available from Parts Express. I don't know whether the quality of the high priced capacitors is worthwhile, but the Daytons are well worth the price. I am sure you will love the BMS drivers even more when the FR is controlled. I sure love mine.
Jack Gifford
Any particular inductors you are using? I don't think I need to get carried away with the high dollar ones here either. Thanks much!
I just used the Jantzen air core inductors, also available from Parts Express.Any particular inductors you are using? I don't think I need to get carried away with the high dollar ones here either. Thanks much!
Jack Gifford
My parts aren't here yet, but this is what I ordered:
2 ea. 027-558 Solen 6.2 uF
2 ea. 027-906 Jantzen 0.47 uF
2 ea. 255-022 Jantzen 0.15 mH
2 ea. 255-052 Jantzen 1.5 mH
2 ea. 005-4 Mills 4 Ohm
2 ea. 005-12.5 Mills 12.5 Ohm
2 ea. 005-20 Mills 20 Ohm
That's about $45 for the two filters.
$30 if you use Dayton caps and resistors.
I'll tell you how many turns to unwind off the 0.15 mH to get the requisite 0.13 mH once I get mine.
This list untested at this point.
Final list after I build 'em....
Jack and Zilch...most excellent, thanks.I'll anxiously wait to hear the results. Oh yeah, this is for the 8ohm version correct?
Thanks for that electronics 101 link in an earlier post, that was very helpful; even I was able to understand it.
Yes, 846B.Oh yeah, this is for the 8ohm version correct?
Remove 5.5 turns from the outside of 0.15 mH inductor (the small one) for the 0.13 mH required. Scrape the insulating enamel off the cut end with a utility knife/box cutter/razor blade.
I don't know what the proper phase connection is for the driver in the Valencia cabinet. Jack'll have to tell us once he gets his RTA running. Reversed phase is correct for my test setup.
I may get them on boards tonight or tomorrow....
Edit: Done. See bottom pic below:
Thank Zilch!
What about for 846a- 16 ohms. Is there a board of parts and schematic yet?
Signed,
Patiently waiting.
smk.
One step above: "Two Tin Cans and a String!"
Longtime Alaskan Low-Fi Guy - E=MC² ±3db
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