I have a pair of Polk Monitor 5 speakers and really like the bass and midrange but the high grate my ears. Does anyone else have that problem. Is there something I can do about it?
Can you make a frequency response measurement?
Based on a photo, it appears that it has a metal dome tweeter and that it's old. Early metal dome tweeters had a strong dome resonance just below 20 kHz. If indeed this is the problem, you can notch out that frequency based on individual measurements for both speakers. Notching can either be done by adding a capacitor / inductor to the crossover or by using a DSP.
If the Polk Audio Monitor 5 is similar to the 7, the cause probably is the large 8 dB peak at 13 kHz: Polk Monitor 7 - Circa 1972 - A slow mod thread - Techtalk Speaker Building, Audio, Video Discussion Forum
Based on a photo, it appears that it has a metal dome tweeter and that it's old. Early metal dome tweeters had a strong dome resonance just below 20 kHz. If indeed this is the problem, you can notch out that frequency based on individual measurements for both speakers. Notching can either be done by adding a capacitor / inductor to the crossover or by using a DSP.
If the Polk Audio Monitor 5 is similar to the 7, the cause probably is the large 8 dB peak at 13 kHz: Polk Monitor 7 - Circa 1972 - A slow mod thread - Techtalk Speaker Building, Audio, Video Discussion Forum
Last edited:
Polk Audio are a splendidly well-documented company. 😎
POLK AUDIO - Speaker Wiring Schematics & More - ALL MODELS except SDA — Polk Audio
Looks like a 6.5" midbass with an 8" ABR, which made it look more than it really was. Must be 4 ohms with that crossover near 1.8kHz. 1" tweeter must struggle there, but nothing very intimidating in that crossover. Seems to be 1" voicecoil on the MW6502 midbass, and a cloth dustcap. Sort of thing that does vocals well.
Seems people were a bit dubious about that tweeter. You could rebuild/redesign this speaker very easily.
POLK AUDIO - Speaker Wiring Schematics & More - ALL MODELS except SDA — Polk Audio
Looks like a 6.5" midbass with an 8" ABR, which made it look more than it really was. Must be 4 ohms with that crossover near 1.8kHz. 1" tweeter must struggle there, but nothing very intimidating in that crossover. Seems to be 1" voicecoil on the MW6502 midbass, and a cloth dustcap. Sort of thing that does vocals well.
Seems people were a bit dubious about that tweeter. You could rebuild/redesign this speaker very easily.
Attachments
12uF 100V NP electrolytic, I'd reckon. And 33uF 100V NP electrolytic, of course. Cheap as anything.
But I'm not sure it'll fix it.
I'd redo all the connectors to fresh metal to start with. If the tweeter is no good, that is going to be hard to fix. Most of them don't dig that low.
You need to measure the DC resistances for a start with replacement drivers.
You could fit a Zobel around 7.5R/1uF across the tweeter. Might tame the top a lot, but people actually often confuse midbass cone breakup with tweeter problems. You could just put your hand over the tweeter and see if the distortion is in the bass. And that can be voicecoil rubbing, fixed by turning the midbass 90 degrees.
But I'm not sure it'll fix it.
I'd redo all the connectors to fresh metal to start with. If the tweeter is no good, that is going to be hard to fix. Most of them don't dig that low.
You need to measure the DC resistances for a start with replacement drivers.
You could fit a Zobel around 7.5R/1uF across the tweeter. Might tame the top a lot, but people actually often confuse midbass cone breakup with tweeter problems. You could just put your hand over the tweeter and see if the distortion is in the bass. And that can be voicecoil rubbing, fixed by turning the midbass 90 degrees.
I don't know these particular tweeters, but some metal domes use a foam plug supporting the center of the dome for resonance control. (JBL`s titanium domes comes to mind) IF they use such a solution and this foam plug has detoriated, they would probably behave like you describes.
Polk makes replacement tweeters that sound much better. The one you want is the RDO-194.
As for caps, any decent film cap would work, but I'd avoid Dayton/Bennic.
As for caps, any decent film cap would work, but I'd avoid Dayton/Bennic.
Agree with Face. The Polk 6.5 is well behaved and a factory replacement would just drop in. I would go budget film cap (in series) and try 3 ohms in place of the 2 ohm.
Face, why avoid the Dayton/Bennics - don't they fit in the set of "(almost) any decent film"? Mundorf MCap Supremes or Duelands might be overkill, but I'm not sure that the Bennics would be any worse that stock 'lytics.
I have the sl2000 tweeters. A simple solution that worked for me (your milage may vary) was to use a capacitor on the tweeter as high pass filter. What it did was reduce the bump in the response at the peak in the bottom of the range of the tweeter. I experimented with a few different values but it worked well enough that I did not get replacements. I am not sure of the values anymore it's been years.