Picked up a pair of massive vintage speakers and I have questions. Cabinet dimensions are 35"H x 24.5W x 19"D. Tweeters are Altec 806A with H 811 B horns. But the 15" woofers have no markings other than the "866" printed on the inside of the cone. Any ideas on the maker/model? They appear to be field coil drivers. There are two sets of wires coming out of each speaker with two different connectors (field coil power supply?). And what is up with the cardboard rocket launcher tubes built into the cabinet?? They appear to be some sort of down firing ports.
Frankenstein Valencias?
- Thread starter hjs
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bowtie427ss
Lunatic Member
That's an 18 inch woofer. Put a ruler on it.
Basket is the same as used on Jensen built Western Electric 4181-A
I can't make a positive ID, but it has some hallmarks of scarcity and goodness.
I suspect it's something special.
Did you get a power supply with them?
The firecracker tubes are interesting, some kind of aperiodic port?
Basket is the same as used on Jensen built Western Electric 4181-A
I can't make a positive ID, but it has some hallmarks of scarcity and goodness.
I suspect it's something special.
Did you get a power supply with them?
The firecracker tubes are interesting, some kind of aperiodic port?
I stand corrected. It is an 18" woofer (frame edge to edge). Unfortunately no power supply. I think you're right about the tubes and I too suspect the woofer is something special. I just hope I can figure out how to listen to it at some point. If it is field coil then the power supply will be a challenge.
The round tubes are to improve laminar flow/reduce turbulence through the port. People do similar by stuffing soda straws into the ports.
https://www.audioasylum.com/message...ng-straws-in-a-port-work-amp-how-to-do-better
https://www.audioasylum.com/message...ng-straws-in-a-port-work-amp-how-to-do-better
bowtie427ss
Lunatic Member
It'd be interesting to know the resistance across the black wires going into the motor cover.
No chance of chasing down the field supply that was used with these?
Without narrowing down an ID, it might be difficult to determine the necessary voltage and current for the field.
No chance of chasing down the field supply that was used with these?
Without narrowing down an ID, it might be difficult to determine the necessary voltage and current for the field.
I measured the resistance across the black wires in both speakers and it is a consistent and surprisingly low 15.5 ohms. From the research I've done it should be more like 500 ohms if it is the power to the field coil. But I think it must be the power as the brown wires connected to them go directly to a separate, four prong plug (though the brown wires connect to only two of the four prongs).
Other measurements:
Resistance across woofer white wires is 6.5 ohms
For the Horn driver the resistance across the terminals is 8.6 ohms.
Thoughts?
bowtie427ss
Lunatic Member
The Jensen and WE's are a 24 ohm field. What was variable was the voltage, some were 24V and some were 110V.
That, by itself suggests an 8 ohm VC.
That's a bit of an odd number, Altecs usually measure around 6.7 for an 8 ohm coil and ~11.7 for a 16 ohm coil. Could be an aftermarket diaphragm. Did you measure both?
bowtie427ss
Lunatic Member
From an old post on the Lenco Heaven forum:
Not suggesting this as an ID so much as provenance that other companies used the same/similar basket.
Not suggesting this as an ID so much as provenance that other companies used the same/similar basket.
Franknfurter
Member
Get a dayton dats V3 and some (laboratory) power supply and measure the T/S parameters which will change with different currents, thats it.
Note: Only current counts for field strength, nothing else. Be aware that current/field strength changes until field coil is heated up to max., which can take 3 hours.
When you found the needed current, it's not so hard to construct a PSU with eg 20% spread, so you can play with Qe ...means, enlarge/shrink your box volume electrically.
A stabilized current source PSU is the way to go then, to avoid Qe change during heat up ...
Note: Only current counts for field strength, nothing else. Be aware that current/field strength changes until field coil is heated up to max., which can take 3 hours.
When you found the needed current, it's not so hard to construct a PSU with eg 20% spread, so you can play with Qe ...means, enlarge/shrink your box volume electrically.
A stabilized current source PSU is the way to go then, to avoid Qe change during heat up ...
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It's an improvement in turbulence reduction, but IME- there's a trade-off, in that it reduces the effective output of the port somewhat, due to increased effective flow resistance in general. Just not as much "port gain" as a big, open port, especially one with proper end flaring. The low bass is "there", but not REALLY "there", with enough energy to match the rest of the sonic spectrum, in many cases.
Regards,
Gordon.