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In Reply to: RE: Help with identifying horn sub posted by KanedaK on March 26, 2023 at 00:30:26
At least two appear to be slightly different at the final flare.
That is not a subwoofer (make one that is)
Follow Ups:
Got a BT-7 sub as my left channel from the original owner (replaced a Ricci OThorn sold to a friend), and awaiting assembly of a Danley TH-50 prototype clone.BT7 still works OK, but it looks like the German horns in the Photo are too short/small in comparison to be a low bass horn.
Planning on using twin Parts Express Dayton RSS390 HF4's in series, unless I read that I should look for others. These will require a custom retrofit to replace the IBM Servo motor and BELTS that wear out. That is one very musical sounding horn that will be fixed for a lifetime.
I agree that the OP should just build a real Horn Sub, tapped or full to get there. He sould stop being a total cheapskate (I'm a partial one myself) in the false hope that something not appropriate for the application will magically work. It's applied Science, not opinion.
Edits: 03/26/23
Hi Claude
Umm well that horn is much like the lab sub, same size, it's got the same mouth, expansion rate and so also the same 80 sq in throat. the lf knee would be in the 30's, in a corner maybe lower.
The Lab sub driver was as close as they could get to the ideal for that horn back then, as long as others are in the same ball park they would work too.
I don't have cabinet drawing handy for that anymore, that would have been in the late 80's but i do have a couple pictures and remember it well. Last time i checked those motors were well over a grand each with a minimum order.
Anyway you can remove the cooling system and motor stuff and with some creative saws all work you can probably carve out enough so that the 12's magnets face in using a 15 to 12 adapter plate. The 12's might have to be offset compared to the 15's, if it's possible not to cut into the rear volume the motor sits in, that would be better. When you take it apart, you will see what parts of it are the horn passage and what parts or in the cooling system.
Alternately, one can trace out the module and make a new one, just make sure it has the foam tape in tact.
Here is the module removed from the cabinet, facing into the beginning of the horn.
Let me know how it goes
Tom
A few miles away.
Ok that goes back a ways, before the popularity of subwoofers in the home.
That one's origin go back to Joyce Poole at Cornell U who was doing research on elephant communication using VLF sound. She wrote a landmark paper using the prototype speaker in National Geographic.
These were used for special effects, electronic organs and a pile were used in a Battle Field simulator for the Army. Nothing of that day that size went that low and that loud.
A review of an old one that found it's way into the home market
https://www.soundandvision.com/content/way-down-deep-ii-servodrive-contrabass
nt
I don't know how many tape drive capstan motors I've seen sent to scrap. I wish I knew about those subs in the 90s. Back then those motors were cheap or free now hard to get.
Now I use a pair of infinite baffle subs in a similar configuration.
Yeah, they were common once and we bought them made for us for about $220 in quantity. The last time i heard a quote, about 15 years ago, they were well over a grand and had a minimum order of 200pc.
That was an amazing motor, super low inertia, it could go from standing still to 6000 Rpm in about 20 degrees of rotation, it was literally a rotary commutated voice coil, the rotary equivalent of my first patent.
I searched on line just now and found the original 4vm62 motor on ebay for around $250 but was actually looking for a picture of the inside, the moving part is a hollow cylindrical basket of wire.
That was a heck of a driver even by today's standards, SD=266 sq/in, BL=27, Rdc .89 Ohms, Fs 20Hz.
Best
Tom
Can you link to that patent?
Back in the 90s when I worked on computer equiupment I collected several motors from disk and tape drives as well as printers. I built a few things the best was a large ribbon tweeter from CDC 9766 alnico magnets and 1/4" thick angle iron. It worked but didn't sound that good. I gave away most but still have some angular actuators and large voice coils from printers. Those voice coils can jump the gap with a 5lb weight and 12vdc.
Hi
I searched Google Patents but only found the Canadian patent for that.The evolution of that was the commutated voice coil idea, then the Servodrive (the rotary version of the commutated coil), then the full rotary woofer and motor, the Phoenix Cyclone was an example made under license.
The attached picture was part of a "large" one of those full rotary drivers. 8 of these were placed at the exit of a 20 foot diameter cooling fan at the Redondo Beach nuclear power plant to cancel the low frequency fan noise.
Each of those had the displacement of 6x 18 inch woofers moving an inch peak to peak. The noise canceling system was in place for about 2 weeks before the earthquake knocked the power plant off line for good
https://patents.google.com/patent/US4531025A/en?q=(tom+danley+subwoofer)&oq=tom+danley+++subwoofer&page=1https://patents.google.com/patent/CA1199875A/en?q=(tom+danley+subwoofer)&oq=tom+danley+++subwoofer&page=1
https://patents.google.com/patent/US4763358A/en?q=(tom+danley+subwoofer)&oq=tom+danley+++subwoofer&page=1
https://www.diymobileaudio.com/threads/phoenix-gold-cyclone-12-in-rotary-subwoofer-rare-working.453370/
I was thinking, i might have something like the motor you mentioned, I think it was from a very old hard drive memory, i mean old!. This was maybe a 6 or 7 inch square alnico magnet and a 4 inch voice coil made of very heavy rectangular wire. There were two rods that guided the VC. Somewhere in my old house i have that and intend to pick it up when i finish moving.
Edits: 04/06/23
This is a good resource for those who might be searching these ideas and concepts.
"I was thinking, i might have something like the motor you mentioned, I think it was from a very old hard drive memory, i mean old!. This was maybe a 6 or 7 inch square alnico magnet and a 4 inch voice coil made of very heavy rectangular wire. There were two rods that guided the VC. Somewhere in my old house i have that and intend to pick it up when i finish moving."Yup, those are the beasts. I gave mine the scrap man. I have small neo magnets from DEC RA81 disks that are much more powerful.
Back in the 90s early 2000s these types of things were very expensive to build. I was thankful for the scrap computer parts they were ahead of audio designers.
The RA81 heads were moved by a moving magnet angular actuator. In the picture if you look carefully into the gap the thin copper strip on the left was the coil and the thin white strip on the right are the magnets. The coil is a oval "race track". The magnets are glued to the rotator and rotate to the current in the fixed coil. A DIYer could build these today, maybe leverage a modern brushless DC motor. "PowerSoft has a subwoofer that basically flattens that design principle into a linear design.
Once I built midbass using AE TD15S and manifold mounted subs using AE IB15s I gave up experimenting with this junk. I have far more low distortion high output bass than I can use.
Edits: 04/09/23 04/09/23
Hi
If you wanted to get a feel for what your motor would be if converted to linear motion (like a belt assembly) or rotary radiator, if you measured the torque per current you can do it. A loudspeaker motor has a BL and Rdc, a figure of merit is BL^2/Rdc. It is how many meters of conductor times gap strength T AND it is how many Newtons of force per Amp the motor produces.
For the rotary system, those motors are often rated in how many ounce / inches of torque they produce per AMP.
IF one had a motor that produced 10 oz/in/AMP, if one had a 1/4 inch radius instead the motor produces 80 oz of force.
Anyway, looks like a cool motor!
Wow. Cool stuff. "Finish moving" is a relative term I'm practicing now. LOL.
It makes a funny noise with the Heartbeat from Pink Floyd's opening track from Dark Side of the moon, but it's working OK for now.
So twin 12" LAB drivers would do the trick, aye? 6 ohms in parallel or the 4 ohm versions in series?
How about the drivers from DTS-10's which I had before?
Thanks for the tips. It's worth the investment for music bass, which I don't need to get to 20 Hz. (even 4k blue rays seldom go that low, very few).
It's on the list but may be a while yet too many projects and dealing with medical stuff.
Hi Claude
Those driver would actually work a little better if you have them.
Don't forget below the horn cutoff, you still have a sealed box which will have nearly the same roll off slope as the room gain slope. IF your room isn't too big, using that room gain slope compensating the sealed box roll off will deliver the only free lunch in audio, low bass for free.
Hope the medical issue clear and life smooths out.
Take care
Tom
Did you mean twin Parts Express Dayton RSS390 HF4's in series will work?or 4or 6 ohm LAB 12's (or LAB 15?). None purchased, so whatever you say specifically.
We can do this via Email if you prefer, but this could benefit other BT7 owners, yes?
I will make them work in the lumber. TIA Tom.
Claude
Edits: 03/28/23
Hi Claude
Hey if you still have my email, send me an email
Tom
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