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Got a POT in your Speaker-Level Crossover?... Improve it .

71.50.26.19

Posted on January 9, 2017 at 11:56:20
drlowmu
Manufacturer

Posts: 9706
Location: East of Kansas City
Joined: January 10, 2005






Read entire post in URL below please.

Jeff Medwin

 

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Hmmm.....got L-pads in mine...., posted on January 9, 2017 at 13:42:04
Steve O
Audiophile

Posts: 6712
Location: SE MI
Joined: September 6, 2001
...more like tandem/coordinated rheostats and not pots. What to do?

 

RE: Hmmm.....got L-pads in mine...., posted on January 9, 2017 at 13:48:25
freddyi
Audiophile

Posts: 3130
Joined: December 6, 2001
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

 

RE: Hmmm.....got L-pads in mine...., posted on January 9, 2017 at 14:07:57
Sidewinder
Audiophile

Posts: 134
Joined: April 13, 2001
Hi,
Where did you source your 16 ohm L pads? I need some for a Higara Vott xover.
Regards,
David

 

RE: Got a POT in your Speaker-Level Crossover?... Improve it ., posted on January 9, 2017 at 14:47:06
kyle
Audiophile

Posts: 1414
Location: London Ontario
Joined: September 29, 1999
The problem with the tandem pots is that you can never get perfectly matched sections and you will get a "chorus effect".
No wait, that only applies to tubes:-)

 

RE: Hmmm.....got L-pads in mine...., posted on January 9, 2017 at 18:29:50
drlowmu
Manufacturer

Posts: 9706
Location: East of Kansas City
Joined: January 10, 2005
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.

 

RE: Hmmm.....got L-pads in mine...., posted on January 9, 2017 at 18:39:58
Steve O
Audiophile

Posts: 6712
Location: SE MI
Joined: September 6, 2001
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.

 

RE: Hmmm.....got L-pads in mine...., posted on January 9, 2017 at 19:15:04
DaveV
Audiophile

Posts: 294
Location: SC
Joined: December 26, 2009
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.

 

RE: Hmmm.....got L-pads in mine...., posted on January 9, 2017 at 19:57:23
Steve O
Audiophile

Posts: 6712
Location: SE MI
Joined: September 6, 2001
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.

 

RE: Hmmm.....got L-pads in mine...., posted on January 10, 2017 at 04:14:55
freddyi
Audiophile

Posts: 3130
Joined: December 6, 2001
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

 

I WAS using L-Pads......., posted on January 10, 2017 at 06:51:58
Alpha Al
Industry Professional

Posts: 2438
Location: N. Carolina
Joined: February 16, 2004
Contributor
  Since:
December 3, 2015
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).

 

RE:.. Improve it - how about putting the resistance "before" the highpass? ., posted on January 10, 2017 at 10:20:56
freddyi
Audiophile

Posts: 3130
Joined: December 6, 2001
I've not measured but assume up to a point a single resistance placed "before" a crossover will work without seriously affecting response. It may be limited in useful range compared to the L-pad,

tapped autoformes are less linear than resistors - the little Klipsch size aren't too shabby if the crossover point is high enough
Karlson Evangelist

 

RE: Hmmm.....got L-pads in mine...., posted on January 10, 2017 at 11:01:29
drlowmu
Manufacturer

Posts: 9706
Location: East of Kansas City
Joined: January 10, 2005
A fixed resistive L Pad will avoid switch contacts, which is a good thing . Employ well chosen 10 Watt Rs.

Jeff

 

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