Have a POT ( potentiometer, rheostat) in your Crossovers ?
Do you have POT ( Potentiometer) in your Speaker-Level crossover ??……..
or, ........ helping out many ALTEC OWNERS
The “ideal” Altec speaker – level crossover would NEVER EVER use a potentiometer or a rheostat to pad down the tweeter level, to match our less-efficient woofer. If you currently use a crossover with a potentiometer, you are seriously degrading your ALTEC’s potential fidelity and in-the-room performance.
The finest solution to this degrade is to change out the POT for a fixed value wirewound power resistor, that is properly soldered in place, using good solder. I realize, many want to keep a POT, for the ease of adjustability, so here goes :
The problem with any potentiometer ( rheostat ) is the wiper arm to resistive element interface. First, the contact area between the wiper arm’s conductive material, and the pot’s resistive area is a small one,. Second, it employs a mechanical connection, not a soldered one, and this connection is MOST inadequate electronically.
Due to this small ( inadequate) contact area, music’s instantaneous peak currents, during playback, are truncated, emasculated, and distorted. Dynamic range, and fidelity suffer. High frequency noise, distortion, and audible irritants occur due to the wiper-element interface, what is called the diode effect, from the mechanical connection, NOT equaling a soldered-in power resistor..
The best solution with speaker-level crossovers is to place just one speaker in the middle of the listening room, and select a compromise Ohmic value resistance, to pad down the tweeter. Both speakers should then have installed in them a high quality, higher power ( 10 Watts or more) resistor, equal values for each speaker, soldered in place, to pad the tweeter .
Such ALTEC speakers then need to be placed in the room, with symmetrical corners and side walls. The end-user should methodically, over time, position the two ALTECS by listening to music, so to find the best sounding speaker location, and overall balance, in the end-user’s listening room.. Only a few of you on this Forum may be willing to do this. I intend to do this in Q1/2017.
OK, I would like to show you all a FAR better way to employ a POT in your speaker level crossover. For a large number of discriminating listeners, this is an easy, reversible DIY implementation.
My most trusted audio friends like the sound of Ohmite resistors. For decades, Ohmite has made a 25 Watt “H” Series 25 Watt potentiometer, a good sounding and nicely engineered part. “ H “ stands for “ heavenly “ .
In January 2017, I found I can achieve easy and substantial sonic benefits, by using TWO such pots, where one previously existed. The two are mounted in what is termed “ dual ganged” or “ in tandem “ or “ concentrically ”.
These two Pots are then electronically connected in parallel, at each of their three terminals. The pots' Ohmic value needs to be doubled, due to paralleling, and the Ohmic values should be EQUAL to each other. For example, if your circuit calls for a 20 Ohm pot, parallel two 40 Ohm “ H” 25 Watt pots, which becomes a 20 Ohm 50 Watt rated pot.
The HUGE advantage is that you now have two wipers, to pass the audio signal to the driver. Law of Squares, you can now pass two squared, or four times the instantaneous peak currents, inherent in music playback. Audible distortion goes down, you have less inherent diode effect.
So, what did “I” hear, going to two paralleled pots the first time, on January 4, 2017???
- a far more natural sounding presentation
- better harmonics and colors of the instruments
- far better inner - detail
- audibly better dynamic delineation
- far less distortion in the entire tweeter range
Can I ever go back to a single potentiometer in a speaker level crossover?? You have to be kidding me, NO WAY ! I will eventually go a fixed, soldered-in resistor. Maybe a 10 Watt Ohmite , they have an “ Audio Gold ” series, and I use Wonder Solder ( Mike Percy ) for solder connections.
In my next post, I can perhaps put forth some ideas of how to most economically execute this.. Ohmite makes a “ rheostat tandem coupling kit ”, part number 6532 which it sells for about $65 a throw, and I will show you how to DIY duplicate it functionally, at ACE hardware, for less than two dollars in carefully selected hardware store parts. Stay tuned., that’s another post, with photos, if there seems to be sufficient sincere interest.
Low Ohms, …………Jeff Medwin
Originally Posted by BillWojo
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