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In Reply to: RE: Got a POT in your Speaker-Level Crossover?... Improve it . posted by drlowmu on January 09, 2017 at 11:56:20
...more like tandem/coordinated rheostats and not pots. What to do?
Follow Ups:
So, you have two wipers and two resistive elements, cross wired? AS in a ladder attenuator using pots??That would be pretty good, since its NOT a single wiper, as in some ALTEC speakers, that causes the problem I have addressed.
A sonic improvement for you might be to measure the ohmic values, and employ soldered in wirewound power resistors, eliminating the mechanical interface of the wipers to resistive elements handling speaker-level ( powerful ) signals.
Edits: 01/09/17
Actually, with an Lpad one wiper is in series and one in parallel with driver. Presents what appears to be a constant upstream impedance. Fixed resistors might be the easiest soln but stepped using decent switch is attractive too.
Edits: 01/10/17
I switched to fixed resistors for two reasons:1: I did not like what they did to the sound.
2: To achieve the attenuation I needed, the L-pad needed to be set between 1 and 2 (on a scale of 0-10), making it difficult to match L and R settings.I determined the amount of attenuation needed by using a sound level meter, measuring the difference between wide open and what I liked. I also took AC voltage measurements at the driver, and converted that to dB's.(the results were amazingly close).
Edits: 01/10/17
The two identical pots would be wired in parallel, not an L-pad.
So you have two wipers carrying the signal but now you have to consider the
paralleled resistance and pick the pots accordingly.
I was describing an Lpad. A pot (or parallel pots) cannot present a reasonably constant impedance to upstream components whereas an Lpad pretty much does. As a result, my inclination is to either construct a fixed Lpad out of two appropriate value resistors OR find a quality multi pole/multi position switch and construct a stepped Lpad (vs common continuously variable type made of two way different value rheostats .
A fixed resistive L Pad will avoid switch contacts, which is a good thing . Employ well chosen 10 Watt Rs.
Jeff
maybe the common tandem 100 watt per section L-pad in 16 ohms and paralleled would offer some theoretical improvement ? (I've not looked at the inductance of one)
it nothing else, this would take some power without smoking
Karlson Evangelist
Hi,
Where did you source your 16 ohm L pads? I need some for a Higara Vott xover.
Regards,
David
hi David - seems like I used to see tandem 16 ohm L-pads - but can't locate any now - Parts Express and MCM carry decent mono units.see if these search links work
MCM L PADS
Parts Express L PADS
Karlson Evangelist
Edits: 01/10/17
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