Monitor 7B crossover upgrade questions
MrGeology
Posts: 83
Someone had sent me a schematic for my 7B's and I purchased a 2 ohm Mills, 33 uf Jantzen and a 12 uf Dayton (1%) to do the upgrade.
However when I pulled the crossover it had a 2.7 ohm and a 4.5 ohm resistor (crossover dated early 1983).
The caps would not fit unless the resistors were removed, so I used the 2 ohm mills where the 2.7 was and wired a 2 ohm and a 2.5 ohm resistor in series (some Daytons that I had on hand) and mounted them on the backside of the crossover to replace the original 4.5 ohm.
Obviously will be getting new Mills resistors next payday as I only did this to make sure the new caps would actually fit on the board and make it through the cabinet (it was VERY tight, but did fit).
It sounds good at low to mid volume but I won't turn it up until I get a bigger resistor to replace the original 2.7 ohm.
I have 3 basic questions:
Is a 2.5 ohm Mills close enough to the original 2.7 ohm, or do I risk damaging the Peerless tweeter?
Is the 33 uf cap close enough to the 34 uf original?
Or, would it be worth it to build my own crossover using the single 2 ohm resistor schematic?
I can wind my own inductors (I have a spool 14 gauge magnet wire) and have built several crossovers in the past.
However when I pulled the crossover it had a 2.7 ohm and a 4.5 ohm resistor (crossover dated early 1983).
The caps would not fit unless the resistors were removed, so I used the 2 ohm mills where the 2.7 was and wired a 2 ohm and a 2.5 ohm resistor in series (some Daytons that I had on hand) and mounted them on the backside of the crossover to replace the original 4.5 ohm.
Obviously will be getting new Mills resistors next payday as I only did this to make sure the new caps would actually fit on the board and make it through the cabinet (it was VERY tight, but did fit).
It sounds good at low to mid volume but I won't turn it up until I get a bigger resistor to replace the original 2.7 ohm.
I have 3 basic questions:
Is a 2.5 ohm Mills close enough to the original 2.7 ohm, or do I risk damaging the Peerless tweeter?
Is the 33 uf cap close enough to the 34 uf original?
Or, would it be worth it to build my own crossover using the single 2 ohm resistor schematic?
I can wind my own inductors (I have a spool 14 gauge magnet wire) and have built several crossovers in the past.
"One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States
-James K. Polk, 11th President of the United States
Comments
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Some will say the values are close enough, I'm not one them.
Dayton for the 12 was a mistake, horrible caps. Sonicap are a good choice for all the caps in the exact values you need. You will find them at Sonic Craft where you will also find Vishay Mills resistors in the exact values required.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Thanks @F1nut, the resistors are a definite go from there. However my income does not allow for $300 for 4 caps, WAY out of my price range.
Looking through the cap inventory at Sonic Craft now, any other cap brand recommendations?
I agree the Dayton 5% caps aren't the best on a tweeter, was hoping the 1% would be better with the heavier gauge leads."One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States -
I may go with the Sonicap 12uf for the tweeters. Will have to spread it out over a couple of months that way though.
As for the 34uf caps, maybe I could go with a 16uf and an 18uf?"One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States -
The Sonicap for the 12 and using something else for the 34 is often done. Splitting the value is best done evenly, so two 17's of whatever works for your budget.
It's not really the tolerance or leads that create the sound signature, it's what is inside.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Splitting the value is best done evenly, so two 17's of whatever works for your budget.
Yeah I have read that splitting the caps should be done as close to evenly as possible. There doesn't seem to be any 17uf caps on the market so would have to go 16+18 (Solen)."One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States -
Sonicap has 17's, but you might as well go with a 34. Anyway, the Solen idea will work just fine and be a lot more budget friendly.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Thanks F1, I appreciate it.
Contemplating just replacing the resistors and the 12uf and leave the 33uf in until I can afford the Sonicap 34's, because the 7B's really are some awesome speakers that will not be going anywhere!"One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States -
You have a plan
The 7B is one of the best speakers Polk ever made, IMO.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
As the drivers are out for realignment, decided to finally do this.
Unfortunately had to spend the money I was saving for the 34uF Sonicaps on a new (circa 1980) 6500 and various shipping costs.
May be around Christmas before I have enough for the 34uF Sonicaps at this point. Hoping it will all be worth the effort.
Thanks again @F1nut , for the sage advise."One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States -
A little food for thought. The original electrolytic capacitor likely had, at best +/-20% tolerance, maybe worse. The Jantzen are +/-5%. That 1.65μf either way. So your 33μf may actually measure 34.65μf. Beyond that, you have a far better cap than the woofer part of thecrossover needs.
The tweeter is worthy of a film cap, but for the woofer an electrolytic is fine. Guarantee that if you did blind testing, probably nobody can find will be able to tell a difference between a high quality electrolytic capacitor(Not ripoff priced "audiophile" electrolytics. I like Nichicon) and a film capacitor for the woofer.
My Klipsch Heresy speakers, the current version retail for around $3,000, use an electrolytic for the woofer. The number one go-to guy for Klipsch crossover upgrades and repair acknowledges that there's no need to replace the woofer capacitor with a film capacitor. He's done it and couldn't hear a difference. I've done it and I can't
hear a difference. Right now I'm listening to 5Jr+ that I recently recapped using a Nichicon ES electrolytic for the woofer. Sounds excellent. -
I think it depends where the woofer crosses over to the tweeter.
A Monitor 7B crosses over at 3K. That's well into the midrange and a better
quality cap 'should' be heard... -
A little food for thought electrolytics have a definite lifespan due to the electrolyte used. Film caps do not.
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Conversely, it may measure 31.35uF, which is way off.So your 33μf may actually measure 34.65μf.
BS!!!Beyond that, you have a far better cap than the woofer part of thecrossover needs.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Conversely, it may measure 31.35uF, which is way off.So your 33μf may actually measure 34.65μf.
Well, the circuit was designed for electrolytic capacitors, which as I previously stated had at best +/-20%. We are both old and there is no way that our hearing can tell the difference in a capacitor on woofer that is off by 1μf. It is what it is man.
BS!!!Beyond that, you have a far better cap than the woofer part of the crossover needs.
It's funny that my Klipsch Heresy speakers use an electrolytic cap for the woofer. Bob Crites, the #1 guy for Klipsch upgrades acknowledges there is no need to use a film capacitor for the woofer. Why? Because you can't hear any difference.
Though I'm sure you know more than Paul Klipsch. What speaker company did you found? What speakers do you manufacturer that people pay $15,000 for?
That's what I thought.
Two adults can have different opinions, mine back by fact, without having to act like a man child.
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My...my, your panties get twisted in a flash.
Paul Klipsch was damn near deaf as evidenced by his ear bleeding speakers.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Here’s why a Polk Monitor 7B speaker needs a good cap for the mid woofer.
Look at everything under the 3k crossover point.
Why would anyone ignore all that music?
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That's a good one. Mine's more colorful lol. Also, it is said that the "sacred area" of human hearing sensitivity is 700 Hz to 2,800 Hz, where we pick up on any little subtle detail.
George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Jensen did the study below in the mid 1940s.
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Personally prefer film caps. Electrolytic caps will increase in value over time if they are not driven with 50% or more than their rated voltage, and will decrease over time if driven with more than 70% of their rated voltage (can't remember the exact percentages but hopefully you get the idea).
Here is the reading on the original electrolytic 34uF cap from one of the 7B speakers.
Unfortunately did not take a screenshot of the Jantzen 33uF cap before installed, however do recall that it was around 32.9 uF
"One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States -
That's interesting thanks! Note that Polk specified DF less than or equal to 3% at 1kHz for the crossover capacitors in the Monitor 7 Series II.
10.85% would be just a tad bit out of spec lol.George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
One way useful life of electrolytic capacitors is determined is when DF has exceeded 3x initial acceptable tolerances. So 3% x 3 = 9%. That 10.85% above would then indicate useful life has been exceeded.
https://resources.altium.com/p/electrolytic-capacitor-lifespan
George / NJ
Polk 7B main speakers, std. mods+ (1979, orig owner)
Martin Logan Dynamo sub w/6ft 14awg Power Cord
Onkyo A-8017 integrated
Logitech Squeezebox Touch Streamer w/EDO applet
iFi nano iDSD DAC
iPurifier3
iDefender w/ iPower PS
Custom Steve Wilson 1m UPOCC Interconnect
iFi Mercury 0.5m OFHC continuous cast copper USB cable
Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
Custom Vibration Isolation Speaker Stands and Sub Platform -
Just a quick update.
The Sonicap does, in fact, produce cleaner highs through the tweeters than the Dayton 1% that it replaced. Not sure what fancy word describes the difference, just sounds more refined now."One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States -
Experimented with the 18uF + 16uF = 34uF idea.
Did a few hours of side-by-side comparisons, swapping 3 different drivers into each cabinet and taking notes. In all cases, the 34uf crossover sounds noticeably better in vocals, piano, guitar and especially near the 3kHz range than the 33uF crossover.
Here is an impedance sweep overlay of each crossover with the same driver in M7B cabinets. The experimental 34uF crossover is the one labeled Cabinet B in the overlay.
The pronounced separation in the impedance curves seen between 400Hz to 3.5kHz is VERY noticeable audibly, and personally prefer the 34uF cap every single time. Not sure, but it almost sounds like the 33uF crossover may be producing up to about 3.5kHz in the midwoofer, it just does not sound as well crossed as the 34uF crossover.
As for the 12uF caps they both produce very clean and refined highs and could not pick one over the other.
Once they both have 34uF Sonicaps will choose which 12uF cap goes best with the rest of it so they will be matched to each other."One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States -
Another data point for you guys: when I rebuilt my XO, the 34 micro-Farads (bass leg) capacitor measured 36.8 micro-Farads (this was after 20+ years).
The SoniCaps I put in (all of them) sounded much better IMHO; I can't believe they cost like twice as much now as they did then!Yamaha RX-A2050 AVR (5.0.2); LG OLED77C2 4K TV(4) Polk Monitor 10B's w/SoniCaps, Mills, and RDO-194 tweets (R/L F/R)(2) Polk RC80i (Top Middle)Polk CS300 center channelAnalog: B&O TX2 Turntable, Nakamichi Cassette Deck 1Digital: Pioneer CLD-99 Elite LD, Panasonic DMP-UB900 UHD Blu-RayBedroom: Arylic Up2Stream AMPv3 driving Polk Monitor 4's w/peerless tweets -
Another data point for you guys: when I rebuilt my XO, the 34 micro-Farads (bass leg) capacitor measured 36.8 micro-Farads (this was after 20+ years).
The SoniCaps I put in (all of them) sounded much better IMHO; I can't believe they cost like twice as much now as they did then!
The two original 34uF caps from my 7B's:
Even the 33uF Jantzen sounds better than either of those lol.
Can't wait to get Sonicaps!"One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States -
Finally got the Sonicap 34uF's last weekend. Here is how they look in DATS for those interested.
Compared to the Janzten 33 uF that has been in use for the past several months.
"One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States -
And the Sonicaps in the crossovers.
Now for a few hundred hours of burn in time...(just over 100 hours currently).
Sounding AWESOME so far."One great object of the Constitution was to restrain majorities from oppressing minoritites or encroaching upon their just rights."
-James K. Polk, 11th President of the United States
