BMS Drivers
- Thread starter dgwojo
- Start date
Alrighty, boys & girls, here's the drill. Celt and I have discussed moving this thread to Speakers, and we're both fine with it, as long as there's no further discussion of buying or selling, whether it's between each other, flipping the drivers somewhere else, or whatever.
I agree with Zilch that there's probably going to be a ton of interesting ideas regarding who's building what, so have at it! I've edited the thread title to just "BMS Drivers".
Be good, now!
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Heh, heh....
And RTA moves up in priority at WojoLab....
Zilch, I hate to admit it but my RTA is my ears, I don't have anything to analyze with!! I'm hoping to find some time over Easter to try the BMS drivers with Mantaray horns and different woofers, 1st I have to remove the 604-8H's and the bass port baffle on top!! This will kill me thinking about it all week..
I like them because every side including the top and bottoms are finished in oak, they were built by a sound guy in Iowa for 515B woofers and 902-16 horn drivers. :yes:Mmm, those oak cabs sure are purty. :thmbsp: Don't feel bad, at least you can look at yours, & caress them, &...
Yup, BMS 4552nd plays nicely on MR931, available new and inexpensively from GPA. I'm running them with M19 XOs, but will get more serious about an optimum filter for my next "Lowboy" project.
The asymmetric dispersion is a clever concept. I'm anxious to experiment with it in cabinets like JBL C36. Seems ideal for high mounted surrounds, as well.... :yes:
The asymmetric dispersion is a clever concept. I'm anxious to experiment with it in cabinets like JBL C36. Seems ideal for high mounted surrounds, as well.... :yes:
Well got the bolts last night and got them installed this morning. Put them in my 19's. As mentioned before had to turn the L-pads way down. It will be interesting to see where others have to set theirs. Just initial listen testing I put the MF just above Min and the HF to about 9 o'clock.
May need some more tweaking, but pretty favorable. Much better HF extension. Long term listening will tell if they have the "Ice Pick" affect.
Zilch: You mention adding an additional L-pad on the model 19... Can you elaborate?
May need some more tweaking, but pretty favorable. Much better HF extension. Long term listening will tell if they have the "Ice Pick" affect.
Zilch: You mention adding an additional L-pad on the model 19... Can you elaborate?
Mike,
I'm using that upgraded, single Lpad Eminence at 800hz, it's down to 9 O'clock and I might still lower it, efficient little buggers!! For laughs I wired them both with reverse polarity, that was really bad. I wired them back to normal and moved the horn mounting flange of the 511B back 6" on the A7 cabinets and they sounded really good in that position, I need to find out exactly where the voice coil plane is on these against the 515-8LF woofer, time to pop the backs on the A7's and do some measuring. I listened for 45 minutes last night and all is great, no fatigue!! Dave.
Yes, because of the increased sensitivity of the BMS over the Altec drivers, you should pad them down in order for the M19 crossover to operate in the range of the "Optimum" settings on the controls. Where you are running them, i.e., with the HF at 9:00, confirms this. HF should be nearly full on to use the M19 compensation to its best advantage.
I have posted the difference in sensitivities per the specs here somewhere, and Steve O has documented similar in his posts on using these drivers.
6 dB would be a good starting point: Put 8 Ohms across the driver, then 4 Ohms in series before it. That should move your crossover control settings up.
To get it precise, install an adjustable L-pad between the crossover and the driver and adjust it until the crossover control settings fall within the "Optimums." Then remove the adjustable L-pad, measure its resistance values (terminal 1 to 2 = parallel, terminal 3 to 2 = series,) and install a fixed L-pad comprised of the closest stock-value resistors to the measured values.
Use 10- or 12-Watt non-inductive wirewound resistors, such as the Dayton or Mills types available from Parts Express.
The same approach would be applicable here, i.e., an additional fixed L-pad to move the adjustable one up into its "Normal" operation range above 12:00.
However, first read again Steve O's posts about HF compensation. The BMS drivers have somewhat flatter frequency response than the vintage Altecs, so a simple substitution in Altec systems which do not incorporate HF compensation will reduce the excessively forward midrange characteristic of Altec drivers, once the overall levels are balanced between woofer and horn.
To use the BMS drivers' extended HF response to fullest advantage, however, install HF compensation such as is provided by Altec's 30923 supplemental EQ and attenuation circuit. It's just three resistors and a capacitor. You can fine tune the amount of compensation by adjusting R-2 as desired, but the stock value is a good starting point. It's the same circuit as is used in Model 19 for this purpose.... :thmbsp:
spaceman
Registered Lunatic
Thanx for posting the correct size bolts, saves me some time, I'm sure. :thmbsp: I picked up some lugs & other things yesterday, & the drivers just got here a bit ago,
so I'm on a mission to aquire said bolts this afternoon.
You're welcome, everyone should have their drivers by now, I hate to admit it but I'm already dreaming about getting more of these drivers for my other 3 pairs of A7's, pretty weird aye?? :sigh:Thanx for posting the correct size bolts, saves me some time, I'm sure. :thmbsp: I picked up some lugs & other things yesterday, & the drivers just got here a bit ago,
justrideit
Busy, busy, busy
Got mine today. Heavy little buggers. Very nice looking. I look forward to getting them hooked up. Thanks Dave!
Not at all weird....
Listened to mine all day yesterday, not fatiguing at all. Had to do some more fiddling with the L-pads. Right now I have them both near 8 oclock. Does't sound right with either one at full min, and still fell like there's too much top end, so will be playing with and additional L-pad and resistors.
Might be time for dual woofers?? :scratch2: Remember, the 511b horns are even louder!!
skywave-rider
Slumming in Akihabara
Mine have arrived.:thmbsp:
http://audioheritage.org/vbulletin/showthread.php?p=128826&#post128826
http://audioheritage.org/vbulletin/showthread.php?p=128750#post128750
Set the requisite compensation with the stock crossover controls, and then balance with the woofer using the supplemental L-pad. :yes: