A place for discussion of general audio, music and related topics.
September 19th, 2021, 12:32 pm
I needs quality resistors for building speaker level attenuation network (lpad).
Also need quality resistors and caps for passive line level crossovers.
Walt?
September 19th, 2021, 12:36 pm
You could always consider a Mobius resistor except I don't know if anyone make one -
https://en.wikipedia.org/wiki/M%C3%B6bius_resistor
September 19th, 2021, 1:02 pm
I like these resistors
https://www.madisoundspeakerstore.com/compare-mundorf-mox-resistorsSolens good enough for woofers
Midrange and tweeters need something better and there are too many to choose from and what ever you choose someone will say there is something better
September 19th, 2021, 1:29 pm
Mills or IRC Non inductive wire wound.
Avoid Caddocks, sort of shout, a very annoying treble.
Low level I still very much like IRC Metal glazed from Handmade Electronics.
September 19th, 2021, 2:49 pm
Cogito wrote:I needs quality resistors for building speaker level attenuation network (lpad).
Also need quality resistors and caps for passive line level crossovers.
Walt?
More recently I upgraded my add-on tweeter. Same driver (JBL 077 slot tweeter with a ring diaphragm), but now installed in a really cool JBL C-41 Angelus enclosure. Since I was going that far with it I also went first class with crossover parts and a custom extruded aluminum back plate to mount everything on. Why not? It's a one time cost if everything works out as planned.
In this case I am crossing over at about 5,000-Hz. with 2.936-ufd caps. comprised of Miflex Paper/Polypropylene/Oil capacitors with copper-foil plates bypassed with mil-spec hermetic Teflon bypass capacitors to get to the desired value. I used pretty standard inductors to create Butterworth 2nd order crossovers. My post for level adjust are 200-ohm Memecor 25-watt aviation grade pots with a .85-ufd Teflon bypasses across the pots. My damping resistors are Mills non-inductive WW 400-ohm resistors. The project wasn't cheap, but OH the improvement!! The add-on tweeters are connected to my main speakers with Andrew Heliax plenum-rated coax.
Before I committed to my parts choices and installation (the Miflex caps are expensive so better to do trials first) I performed trials on the bench "road-testing" everything I had in my inventory against the Miflex caps. To make a long story short -- it wasn't even a contest.
My main horns were done a long time ago and the primary capacitors are Russian 4-ufd Teflon/Oil hermetics with polystrene bypasses together with 5-ufd hermetic polycarbonate caps. I am seriously thinking about replacing the 5-ufd caps with Miflex caps. The polystyrene caps may not make the cut either. Does it ever end???
If you wish to get the Russian Teflon/Oil hermetics (they're damn good to say the least) I have inventory (I got them when they were available) and can provide matched pairs. Smaller value hermetic Teflons are on eBay. The Miflex caps were obtained from Parts Connexion. The 4-ufd Russion caps are about as big as beer cans and the Miflex caps are large as well.
If you want greater detail -- just ask.
Cheers, and a pint of your favorite APA!
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- MIFLEX Capacitor Data Sheet.pdf
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- Add-on Tweeter Details.pdf
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September 19th, 2021, 4:18 pm
Madisound site says,
In contrast to normal wire resistors, metal oxide film resistors exhibit no residual inductivity. Therefore, in all cases where impulse velocity is important, in the middle range for example, metal oxide film resistors should always be chosen. The design which we supply has a continuous load capacity of 10 Watt, but can handle a much higher load in the impulse range.
I wonder why they are not recommending these for bass and sub-bass where impulse are very high.
Thanks.
September 19th, 2021, 4:38 pm
SoundMods wrote:More recently I upgraded my add-on tweeter. Same driver (JBL 077 slot tweeter with a ring diaphragm), but now installed in a really cool JBL C-41 Angelus enclosure. Since I was going that far with it I also went first class with crossover parts and a custom extruded aluminum back plate to mount everything on. Why not? It's a one time cost if everything works out as planned.
You ring tweeters look fantastic in the new cabinets. Congrats.
My post for level adjust are 200-ohm Memecor 25-watt aviation grade pots with a .85-ufd Teflon bypasses across the pots.
Interesting. How do you rate them in comparison with quality fixed resistor LPAD network?
If you wish to get the Russian Teflon/Oil hermetics (they're damn good to say the least) I have inventory (I got them when they were available) and can provide matched pairs.
Thanks. The crossover I will be using is strictly at line level, so I don't need high voltage caps. I already testing the crossover in a breadboard and it works fine. Need to get quality parts to build the crossover network and fine tune it.
Once I have the room acoustics done, I might move the LPAD network to line level crossover. Line level crossovers have 10K impedance, so a small change in impedance with LPAD network will be better than big impedance change in 8ohm speakers, I think.
September 19th, 2021, 4:50 pm
Cogito wrote:SoundMods wrote:My post for level adjust are 200-ohm Memecor 25-watt aviation grade pots with a .85-ufd Teflon bypasses across the pots.
Interesting. How do you rate them in comparison with quality fixed resistor LPAD network?
For line level I would recommend a shunt attenuator (see attached) with a shunt attneuator you have only to deal with the quality of one fixed resistor -- failing that -- something along the lines of a Spectrol WW pot or Penny & Giles conductive plastic pot. I have experience with both.If you wish to get the Russian Teflon/Oil hermetics (they're damn good to say the least) I have inventory (I got them when they were available) and can provide matched pairs.
Thanks. The crossover I will be using is strictly at line level, so I don't need high voltage caps. I already testing the crossover in a breadboard and it works fine. Need to get quality parts to build the crossover network and fine tune it.
You haven't said if your passive crossover is going to feed tubes or SS electronics. My preference is Electronic Concepts polycarbonate caps and/or Teflon caps. Another possibility is the V-Cap OIMP series.
Whether polycarbonate or OIMP caps they need Teflon bypasses and that configeration is competitive with a straight wire.
September 19th, 2021, 7:03 pm
Cogito wrote:I needs quality resistors for building speaker level attenuation network (lpad).
Also need quality resistors and caps for passive line level crossovers.
Walt?
Since you are going line level -- my direct experience with resistors in the signal path that can best serve are in order of importance -- WW Bobbins -- Vishay Bulk Film -- Dale metal film -- Roderstein metal film.
In another thread I talked about a shunt attenuator where there is no pot or stepped attenuator in the signal path -- just a high quality resistor such as that noted above.
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![Bobbin teardown.jpg (101.77 KiB) Viewed 9594 times Bobbin teardown.jpg](./download/file.php?id=2127&t=1)
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![Precision-Wirewound-Resistors1.jpg (51.48 KiB) Viewed 9594 times Precision-Wirewound-Resistors1.jpg](./download/file.php?id=2125&t=1)
September 19th, 2021, 10:02 pm
Walt,
While searching for shunt attenuators, I found this from GoldPoint. They say, source sees variable impedance with shunt regulators.
https://goldpt.com/attenuator_types.htmlI would not find bobbin type WW resistors. However, I found .3W Riedons on digikey.
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