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Drivers for 811b's ?

kyle said:
The seleniums recommend a 2K crossover. Not much point in putting them on an 811. The much smaller horn on a 604 is usually crossed at about 1500. Is this a power handling related point?
Click to expand...

I put the D210Tis on a 500/800Hz (depending on whose specs you read- the same horn was available from three different suppliers, under different brand names) rated horn (in the Seeburg project), and measured them on LEAP/LMS... no audible signs of distress down to 600Hz! I used a low-electrical-Q crossover, to give an acoustical crossover of about 1100 Hz (but, if you do the numbers ELECTRICAL f3 point is up around 4Khz or so, which gives MASSIVE power handling), with a notch filter down at resonance on that horn (which looked to be around 700 Hz). Anyone who heard the Seeburgs, can tell you they had ABSOLUTELY NO problem with midrange rasp, harshness or noise!

You have to remember... the Seleniums were made to be CHEAP PA drivers... and to handle the high distortion levels and high absolute SPL levels, you HAVE to limit the bottom end. To that end, I'd NEVER use an Altec 808 or 806 below 2KHz, in a modern PA system... they'll blow up just as fast as the Seleniums (this I KNOW from experience with what customers bring me to repair, after they blow them up)!

Can't find the graph I made of the D210Ti on the horn I used... but I can tell you, it was an absolutely flat (within +- 3dB) tilted line, from 700 Hz up to about 19.5KHz. The tilt was the normal "bottom end gain" of ANY horn vs. a driver in "free space"... and was EASILY dealt with by the combination of a low-electrical-Q highpass and a shelving circuit (cap/resistor parallel pair) at around 12KHz and up. Made it flat as a board, from 1200-20000 Hz, for all intents and purposes...

Given the similarity of the horn I used to the Altec 811, I'd expect similar results to be EASILY obtained with that horn... the Altec may even have slightly MORE low end gain... which allows even more electrical "power filtering" on the bottom, increasing power handling EVEN MORE...

Regards,
Gordon.
 
Gordon,
If you don't mind what was the horn you used similar to the 811? Given the price (currently 31.00)I've ordered a couple of the Selleniums to play with.
 
I'll let you know when I find out who the current OEM for the horn I used is, now. It's changed brand names again. I'm supposed to be getting a pair of the new versions in, any day now...

Regards,
Gordon.
 
dgwojo said:
Very tough to compare the 902 and the Selenium on my 511B horns, the 902 sounds slightly more efficient, like the old days, louder is better to my ear but the 902's lack the highs I hear in the Seleniums, the 902's seems stronger in the midrange but that might be due to the efficiency mismatch.
Click to expand...
902 requires HF compensation to tame the forward midrange and boost the highs. I'd use 30923 after the Eminence crossover (and L-pad attenuation, if any,) and adjust R-2 as required for flattest response:

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GordonW said:
Can't find the graph I made of the D210Ti on the horn I used... but I can tell you, it was an absolutely flat (within +- 3dB) tilted line, from 700 Hz up to about 19.5KHz. The tilt was the normal "bottom end gain" of ANY horn vs. a driver in "free space"... and was EASILY dealt with by the combination of a low-electrical-Q highpass and a shelving circuit (cap/resistor parallel pair) at around 12KHz and up. Made it flat as a board, from 1200-20000 Hz, for all intents and purposes....
Click to expand...
Post your circuit schematic here, Gordon, and I'll measure it with the Selenium D210Ti on 811B and 511A horns.... :yes:
 
OK, let's see how good the D210Ti is.

I planned to do my next project "on the cheap" by using a pair of refoamed LE14A's, the JBL mid/hf waveguides, a pair of 104H-2's as mid range drivers, and a pair of Selenium D210Ti drivers as HF's. I couldn't wait to package everything in cabinets, and wanted a quick idea whether I was on the right track, so I fired up the system as shown in the photo's in my shop.

The 104H-2's are not contained in their normal subenclosures, and the woofer is just resting it's magnet on a roll of tape to keep it upright on the bench. Crossover points are 900 Hz and 3500 Hz. Even though nothing is baffled or cabineted, it sounded pretty impressive. Enough so, that I ordered another pair of Seleniums with 1 3/8"-18 TPI mounting. Maybe this project will become two projects if the Selenium will perform down to 1.2 KHz as Gordon and dgwojo suggest.

I will be sending the bolt on pair of Seleniums to Zilch in the next couple days to measure, and will probably send him the screw ons when they are received as well. I didn't measure any FR's since the lashup was so discombobulated, but for $31 each, they seem pretty impressive at first listen. A little brighter maybe than the BMS drivers, but maybe that should be expected since they have titanium diaphragms versus the BMS mylar. I really do love the sound of the BMS drivers, and hope the Seleniums will grow on me as well. And they seem to be quite efficient as well.
 

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WHOA! The latest project at JackLab, conceived in these very AK Speaker Forum pages, is REVEALED...! :banana:
 
Zilch said:
902 requires HF compensation to tame the forward midrange and boost the highs. I'd use 30923 after the Eminence crossover and adjust R2 as required for flattest response:

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Click to expand...

Zilch,
I might have some of those 30923's lying around, I know I gave one to Punker X to duplicate for his speakers, Dave. :yes:
 
dgwojo said:
Zilch,
I might have some of those 30923's lying around, I know I gave one to Punker X to duplicate for his speakers, Dave. :yes:
Click to expand...
COOL! Hook it up and tell the forum if you can hear the difference.

It's easy to mock one up if you can't find it. That's the "T-filter" used in M19, late 604, Markwart, et al. :yes:

Tom Brennan uses a simplification of the circuit for compensation, similar to what Gordon used with Selenium.

I have done sims of both approaches in comparison, but nobody's asked for that level of detail.

[Yet.... ;) ]

Edit: Here is a SPICE sim of what that filter does as R-2 is varied:
 

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GordonW said:
The only place I've had problems with the D210Ti is trying to use the screw-on version on the back of an Eminence Beta 10 CX. Think there's some sort of throat mis-match there... BIG dip at around 6KHz. I'm going to try the bolt-on version with a bolt-on/screw-on adapter, and see if I can shake up things a bit...

Regards,
Gordon.
Click to expand...
Gordon,
The threaded version is on sale under the deal of the day for $25 again, I got PE to substitute the bolt-on for the same price last year. This sale might last longer since it's the weekend??

Part Number 264-235
List Price: $50.00 EA
Price: $42.00 EA
Special Price: $25.00 EA


264-235

264-235L.jpg
 
Selenium D210Ti on Altec 811B

Drivers courtesy AK member Jackgiff:

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Edit: Model 19 crossover has an even better contour, and dials it in +/- 2 dB, Cyan.

Impedance curve also attached....

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macaltec said:
I dunno 100% what I'm lookin at but it don't look too bad for the money. I ordered 4 of em yesterday (just to have)
Click to expand...
Hi, Mac.

It's in the legend there. I got them within +/- 2.5 dB in a matter of just a few minutes, just as Gordon suggested would be the case. :yes:

Red curve is the uncompensated response, down 10 dB at 20 kHz. They do have VHF extension, but are either "Shouty" or "Dull" without EQ, depending on their relative level with respect to the LF.

The slope is basically linear. Pushing the "CD Horn" button on Behringer CX3400 engages its built-in boost, making the Green curve. A little bright.

So, I kludged together a 30923 T-filter. It was also too bright. Adjusting R-2 to 15 Ohms got me flatter response. It could be optimized more for this driver via tweaking C-1, probably.

Mating this with a LE14 woofer to play full range, and dialing the 24 dB/octave frequency on CX3400 up and down, 1.2 kHz seems to be about the lower limit. Whether that's defined by the horn or the driver, I don't know at this point.

Also, note that in the system balancing, my LF is playing hotter by a couple of dB; I've dialed down the HF a bit because Ti can sound somewhat harsh when absolutely flat. The compensation contour needs to be adjusted to generate a tilt. I'll let AutoEQ do that, eventually, and see how it sounds.

Gonna drag out the M19 crossovers and see what I can do with those, now.... :thmbsp:
 
I'm on the edge of my laptop to see the results on that, Zilch. Is there anyway to treat the diaphragm of these Selenium to eliminate the harshness? Do you think you can come to an electrical solution to eliminate the lesser qualities? (I guess that last question is a bit rhetorical but it might be answerable?)
 
Just to throw more into the mix, how would 2420's with adapters work on the 811-b, I'd like to change out my 2345's?
jaybird
 
Zilch,
Great graphs, I'm not getting any of the harshness in my systems with a Sony STR-7065 receiver and 511B horns. I'm still impressed, best $25 each I spent in a long time, the high-end spike will work well for me behind the movie theatre's perforated screen, yes!! I received a pair of threaded versions today from PE in case I want to swap out the JBL drivers on the theatre's JRX-125's, the blogs on PE suggest that as an upgrade. :yes:

125.jpg
 
Seleniums look pretty good so far

Zilch, those Seleniums measure pretty good on the Altec 811B horn. Their curves look much better than the uncorrected Altec 806A's, if my memory serves correct. The factory curves show them on a HL14-25 horn (whatever that is) being about +/- 5 db from 1 KHz to 20 KHz, which agrees numerically with your measurements on the 811B horn, with the peaks being in different spots. I suppose the different horn loading can produce that effect.

All in all, they look pretty useable so far. The driver has adequate SPL to tolerate the EQ needed to flatten their response, while leaving enough to match most woofers (mine will be LE14A's). Now the big test is, how do they perform on the JBL $10 waveguide? Maybe that needs to be on a new thread, since this one is specifically about Altec 811B's.

The titanium dome sounds different than the mylar domes used in BMS drivers, but not so drastically different to my ears. Maybe just a little brighter, while the BMS is more mellow. Hopefully with the proper EQ, they will provide a cheap answer for cost cutting DIY'ers. And it will need some serious listening to see if the response at 1.2 KHz is really all that good. After all, Selenium recommends minimum crossover at 2 KHz, with 12 db/octave slope. Maybe they know something?
 
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