Using 2 mw6503's with peerless tweeter...Which crossover?

[jakelm]

Hi all. Its been a while since I've visited. I'm glad to be back.

I have 2 mw6503's and a peerless tweeter....I currently have 7b's with peerless as left and right channel and I'm thinking of building a center channel with the 2 mw6503's and the peerless to complement the 7b's. The crossovers in mind or the ones used in the 10's. Polk has 2 different crossovers, one is for 10b and the other for 10 series 2. I was wondering whch would be best for me mw6503's as a center channel?

M10B BE1000-A $46.40 ?
M10 SER 2 BE1000-B $49.60 ?

Now the mw6503 was used in both the 10B and the series 2, but the peerless wasnt. So my question again is with both the mw6503 and the peerless which would be best?

Thanks
Jake

P.S. I did post this in the vintage section, but since this is a DIY job, I figure it would go here too. I appologize for the multipost.

[schwarcw]

Jake,

Use the crossover that was designed to play with the Peerless tweeter. This will be you most critical timbre match. Sounds like a cool project. Are you going to use a passive radiator in you custom center? Good luck and let us how how it sounds.

[jakelm]

Thanks Carl

No.This center channel is designed without the low end of a PR. In stead a tuned port will be used. The problem I have is that I cannot find an original Monitor 10 crossover that was used with the peerless. So my other option is to purchase a new one from polk. My guess (or my hope, I should say) is that the crossovers did not change much between the series. The crossover points should be pretty close. So with no luck finding the excact xover, I was hoping from the 2 choices Polk offers, someone would know the best guess.

Im hoping (if I get the encloser right) that the tember match would be closer than anything out there on the market. The trickiest part is going to be the tuning port. I think I will build different lengths and try them out and see which comes closest to the 7b's. I might not need a port at all. But we will see.

Jake

[schwarcw]

Hi Jake!

Checkout this link on the Forum http://www.polkaudio.com/forums/showthread.php?t=38755

This thread shows the schematic for the Polk Monitor 10's with and without the Peerless. Compare the two schematics for the crossover with the 6503 driver. Use the cap, resistor and inductor (coil) values for the 6503 and the same from the other schematic for the Peerless. You can then select a crossover from Polk that would require the least modification to match your Polk center "hybrid". The other thing to figure out is how to match the cabinent volume. You may have to build a deeper cabinent to maintain the volume needed for your design. Call Polk Customer Service and talk with Ken Swauger. He will give you some sound guidance.

Carl

[jakelm]

24"w x 8.25"h x 12.5d Which I beleive with a proper port will sound excellent.

The crossover are more different than I thought.

Im trying to figure out the xover point for the tweeter. Seems like the original xover allowed the peerless to handle lower hz. Or is it the opposit. I think I will get the 10B xover and see how it sounds. Unless some one knows of a 10 or 10A xover avaliable.

Jake

[jakelm]

Well this puts a damper on things......Polk does not handle the 10b or 10series 2 xovers anymore....I really didnt want to have to build one. Ah well..here goes nothing.

Jake

[schwarcw]

Hi Jake! All is not lost there are not a whole lot of components to the crossover you need. As I mentioned, pick out a crossover from the link that most resembles your design. Parts Express or any company can supply a board, binding posts, inductors, caps and resistors. Good luck! Keep us posted!

[jakelm]

OK just finished the box...Talk about polkenstien!!.:D .lol.. but it sounds great...I ended up with 22"w x 8.5"h x 12"d with a 2" port approx 7" long on the back side. This box is huge compared to my CS1. Just found an original m10 xover with the fuse on ebay....bought it...hope it works. I'm using my Monitor30 xover for the time being and it sounds awsome. Big difference in the peerless tweeter compared to the other dome tweeter in my CS1 center. The vocals in the center just seem to be more natural. The only thing I'm having trouble with is finding a grill to cover the front. I'll have to biuld one, I dont know how that will come out. I painted it a rot iron grey, same color as my Mitsubishi, but will venner it as soon as I can. You cant tell with the lights out ;) but a grill and veeneer are my next step, after I install the xover.

Jake

[jakelm]

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250010365116

Thats what I found on ebay

Jake

[jakelm]

Just ordered a grill kit from partsexpress. Now once I have the grill up..you think it would upset people if I slapped a polkaudio logo on it...lol :p

Jake

[Polk65]

Excellent project. The RTA 8 / RTA 8TL are worth considering for a vintage center with port. RTA 8 - http://polksda.com/rta8t.shtml

Was this a lucky bid on your part? Looking over the schematics (http://www.polkaudio.com/forums/showthread.php?t=38755) posted by Doro this appears to (my eyes) the correct crossover for the HF1000 or Peerless tweeter. More at post #33:
http://www.polkaudio.com/forums/showthread.php?t=32671

[jakelm]

If my memory serves me right, the xover with the fuse was the same xover used with the peerless. And what led me to believe also with this xover was the 12uf cap. 2 12uf caps were used with the peerless.

[jakelm]

Polk65, thats pretty much what I build, except for the peerless instead of the silk dome and the width (if layed sideways) is not as long (22"w), the port is in the back.

Jake

[jakelm]

Just installed the m10 crossover...works well. The speaker now seems alot brighter. I'm not sure if its a good thing or a bad thing. No distortion or anything just brighter.

I hope I got the wires right. White is negative? Black is positive?

Jake

[jakelm]

I'll try to take some pics.

Jake

[Polk65]

The black wires connect to the terminals with a red dot. Blue wires are the counterpart for SDA dimensional drivers.

The crossovers are different. A photo of your 7 crossover may help with suggestions of what to change. I have some spare crossover parts that I can send if you or a friend can solder.

[jakelm]

The black wires connect to the terminals with a red dot.

Thanks Polk65: I asssume you mean (red dot) is positive. So black is positive. My mw6503's are labeled +/-.

Another thing. I noticed on the schem of the m10 that the midwof (mw6501's) are ran in parallel with each other not series. But would this be the same for the mw6503's since the mw6503's ohms have changed alitlle. My understanding is the ohms on the newer mw6503 is a tad lower. Should I keep it in parallel (positive to positive, negative to negative)?

Thanks
Jake

[Polk65]

+ or red dot goes to the black wires. That m10 crossover is designed for drivers in parallel so keep it that way. Getting your center crossover design closer to your mains is what to aim for. From looking at the schematics, I think the issue is in the tweeter circuit. Post a pic of your crossover if you can.

[jakelm]

The crossover is here... My understanding from the scem is the tweeter wires come from the 12uF cap (left of xover from pic) black= pos and white= neg. And midwoofer wires come off the side(or top in pic) again black=pos and whit= neg. Correct?

[jakelm]

This is the current wire config...excuse the bad drawing

[jakelm]

schematics (http://www.polkaudio.com/forums/showthread.php?t=38755) posted by Doro this appears to (my eyes) the correct crossover for the HF1000 or Peerless tweeter. More at post #33:
http://www.polkaudio.com/forums/showthread.php?t=32671


Polk65: I just read again what Ken had to say between the m10a xover and the 10b xover. My undertsanding of the schem of my xover is that it is a 10a with a 2.5ohm resistor. I still dont understand why it seems so much brighter than my 7b's, the tember especially in the higher fr should be very close to one another. Could I replace it with a 3ohm to smoothin it out even more? Or am I looking at the wrong thing?

Unless its the output of my reciever for the center channel.

Jake

[jakelm]

Ok now I'm confused on something. The original 10's and the original 7's had the peerless tweeter, correct?

On the schematics of the original 7's there is a 2.0 ohm resistor with the 12uF cap. There is a 2.5ohm resistor with the 12uF cap on the original 10's. Now if there is the same peerless, why is there different resistors?

I'm listening to my 7's compared to the the center I built, right now. There is a major difference in the highs. The highs in the center with the 2.5ohm resistor is alot louder than the 7's (and less mid). Now I did not pull the xover out of the 7's but I'm pretty sure is the original, because of the fuse in the back. To my knowlege there is only one style crossover with the fuse (the original). The others are revised and different generations.

Whats going on?

Jake

[Polk65]

The original 10's and the original 7's had the peerless tweeter, correct?


Yes. Check out brochure #2 1984 Original Monitor 7/10 Brochure (836K) (http://polksda.com/srsad.shtml)



On the schematics of the original 7's there is a 2.0 ohm resistor with the 12uF cap. There is a 2.5ohm resistor with the 12uF cap on the original 10's. Now if there is the same peerless, why is there different resistors?


I suppose the 2.5 value is used to tame the tweeter down a notch since the midrange has gained sensitivity with the addition of another driver.



I'm listening to my 7's compared to the the center I built, right now. There is a major difference in the highs. The highs in the center with the 2.5ohm resistor is alot louder than the 7's (and less mid). Now I did not pull the xover out of the 7's but I'm pretty sure is the original, because of the fuse in the back. To my knowlege there is only one style crossover with the fuse (the original). The others are revised and different generations.


In the photo of your Monitor 10 crossover, resistor (B) is clearly 2.7 ohms. Resistor (A) is hard to read. Is this 2.5 ohms or 2.0 ohms? If it's 2.0 this would make the Peerless overly bright. There were several changes and part substitutions. Don't assume that your Monitor 7 crossovers match the posted schematics.

In the other thread, Ken mentioned that the tweeter will be brighter with a 2.0 ohm resistor versus 2.5 ohms. While looking over some other monitors which used Peerless tweeters I noticed that 2.7 ohm resistors were used. Try swapping the 2.5 ohms resistor (A) with 2.7 ohms resistor (B). This will tame the tweeter a notch and should wake up the mids.

I'm learning from this and starting to enjoy this project. If I make mistakes hopefully you or someone else will catch it.

[jakelm]

Is this 2.5 ohms or 2.0 ohms?
.


It is 2.5ohms.

[jakelm]

What if I leave the 2.7 where it is (B). And just replace the 2.5ohm (A) with a 2.7. What I will do is pull the xover out of one of my 7's and see what size resistor. If its the same, I will try swapping tweeters from my 7's to my center and see if its the driver. If it isnt the tweeter then I will try swapping the 2.5 ohm resistor with a 2.7 ohm.

[jakelm]

I suppose the 2.5 value is used to tame the tweeter down a notch since the midrange has gained sensitivity with the addition of another driver.



Why would the tweeter be tammed a notch when more bass is added? Seems it would be the oposite, with increasing the highs to keep it flat with the mids and lowes.

[jakelm]

I do have this hooked up right , do I? The tweeter comming of the 12uF (D) and the mids coming of the 34uF (F)?

[Polk65]

My understanding from the scem is the tweeter wires come from the 12uF cap (left of xover from pic) black= pos and white= neg. And midwoofer wires come off the side(or top in pic) again black=pos and whit= neg. Correct?


The wires from the yellow 12uF Mylar cap (D) go to the tweeters. Black is positive (+) red dot for both.



What if I leave the 2.7 where it is (B). And just replace the 2.5ohm (A) with a 2.7. What I will do is pull the xover out of one of my 7's and see what size resistor. If its the same, I will try swapping tweeters from my 7's to my center and see if its the driver. If it isnt the tweeter then I will try swapping the 2.5 ohm resistor with a 2.7 ohm.


That's a good plan but I hate solder fumes.



Why would the tweeter be tammed a notch when more bass is added? Seems it would be the oposite, with increasing the highs to keep it flat with the mids and lowes.


This depends on the mid-woofer driver(s) sensitivity. I don't know the driver specs but after combined, they could be more sensitive than the tweeter. The rule I believe is, when two 8ohm drivers are connected in parallel they have a combined gain of 6 dB. Let's say the tweeter is rated at 92 dB, and the mids are each 88 dB. With one mid you would want to tame the tweeter. Combining the mids in parallel increases their sensitivity so in this example, two mids rated at 88 dB would increase to around 94 dB so you would want to tame them.

[jakelm]

This depends on the mid-woofer driver(s) sensitivity. I don't know the driver specs but after combined, they could be more sensitive than the tweeter. The rule I believe is, when two 8ohm drivers are connected in parallel they have a combined gain of 6 dB. Let's say the tweeter is rated at 92 dB, and the mids are each 88 dB. With one mid you would want to tame the tweeter. Combining the mids in parallel increases their sensitivity so in this example, two mids rated at 88 dB would increase to around 94 dB so you would want to tame them.

If the 7's have the peerless and the resistor is 2.0. The xover I have for my center has a 2.5ohm resistor, wouldnt that make the peerless in the center "softer" than the peerless in the 7's, not brighter?

Thats what confuses me, my center has a larger ohm resistor, yet a brighter tweeter.

I'm saying this yet without pulling my 7's xover, to make sure. (At this point I'm assuming about the resistor on my 7's).

I have never heard the 10's personally. With the same driver, are they normally brighter than the 7's?

[jakelm]

Of wait a minute here....just noticed something.....

On the specs of the original 7's,,,,If you look at the notes at the bottom right. It states " 'A' : 2.0ohm was 2.7ohm; deleted"

I might have a 2.7ohm in my 7's

that would make since for the reason I have a brighter center chanel

[jakelm]

What I need to do is pull the 7's crossover and make sure they are the same...If they are not, I will put the same xover in the center as are in the 7's

[jakelm]

Ah HAH!!...The original 7's had a 2.7ohm and the original 10's had a 2.5ohm. This would make my center brighter.

I feel like Sherlock Holmes

[jakelm]

Picture of my 7b's w/peerless.
A=4.5ohm---> (is this going to my mids????)
B=2.7ohm
C=12uF
D=12uF?? (not sure, it should be, but cant read it)
E=.23mH

So compared to the 10 xover, how do I get the tweeter to match?

Jake

[jakelm]

Would I replace the 2.5ohm with this 2.7ohm?

I swoped the resistors like you told me. But if I were to replace the resistors, would these work? http://www.mouser.com/catalog/specsheets/XC-600041.pdf

I shop at mouser.com but I am having problems finding the reisitors with the exact same specs. I think Polk used 5w 10% cement resistors. All I can find is 5w 5%. Would that work?

Jake

[Polk65]

Jake,

First, I'm not all that experienced with this. Second, with a custom center you are going to have to experiment.

A few things to check aside from the crossover. Verify that your receiver or processor has the same volume levels set for left, center, and right speakers. You may need to adjust the center speaker angle up or down a little bit. Speaker wire and amplifier power could also be possible issues but not likely here.

SHORT ANSWER: Change resistor 1 ( 'A' in your Monitor 7 photo ) from 2.5 ohms to something between 3.0 ohms and 4.0 ohms to your liking. When you increase this value your center's tweeter will become quieter than your Monitor 7's.

LONG ANSWER: Depending on how close of a match you would like your center to be it can take alot of effort. Each part that you change has subtle effects on how the tweeter sounds so getting it just how you like it will take time.

I decided to jump from looking at schematics to a mock setup similar to yours. Testing was done at low to moderate levels at a distance of only 4 feet from my workbench in both stereo and mono. The results will be different for you in a large room and with your speakers.

I took my pair of Monitor 5jr's apart and changed the crossover values to those in the "original Model 7" schematics. They have MW6502 mid-woofers and the sl2000's were replaced with Peerless tweeters which mounted pretty flat with two screws at opposite corners.

resistor 1 = 4.5 ohms
resistor 2 = 2.7 ohms
capacitor 1 = 12uF mylar
capacitor 2 = 34uF electrolytic
capacitor 3 = none
inductor 1 = 0.22mH (0.23 is used but I only have 0.22 available)

One of my Monitor 10's became the third candidate. The crossover values were changed to those similar in other Monitor 10's. Peerless tweeters went in the same way as above.

resistor 1 = 2.5 ohms with (capacitor 3) 12uF electrolytic capacitor in parallel
resistor 2 = 2.7 ohms
capacitor 1 = 12uF mylar
capacitor 2 = 34uF electrolytic
capacitor 3 = 12uF electrolytic
inductor 1 = 0.40mH

resistor 1, capacitor 2, capacitor 3, and inductor 1 were changed to different values many times and I gave each change a listen.

resistor 1 was tested with many values but I found 3.0ohms - 3.5ohms sounded good. Experiment here and see what you prefer.

resistor 2 with the value of 2.7 ohms seems to be a constant in the Monitor 5, 7, 10 and RTA 11's(*). Observing this I decided to leave this alone even though it goes to the tweeter inductor. You may want to try some higher resistors and see how it sounds to you. The Monitor 10 with sl2500 tweeter and RTA 11tl remove resistor 2 and one side of inductor 1 replaces it. If you try this you may need to increase the value of resistor 1.

capacitor 1 like resistor 2 also seems a constant so I didn't bother changing it. Later Monitor 10's and RTA 11's(*) used 16uF which you might want to try.

(*) I looked at RTA 11t's and RTA 11tl's because some of their values are similar to the Monitor 10's.

capacitor 2 is nearly always 34uF in the above series speakers with some exceptions like the Monitor 5A and Monitor 10 (the version with sl2500 tweeter). I tried this with a 27uF mylar (Monitor 5A use mylar and Monitor 10 with sl2500 use electrolytic) but did not notice much of a difference. You might also give this a try.

capacitor 3 runs in parallel with resistor 1. At first I used it then removed it. Try it and see what you like.

inductor 1 was swapped with 0.22mH, 0.3mH, 0.4mH and I noticed subtle differences. Coblio wrote (http://www.polkaudio.com/forums/showthread.php?p=538732) that he liked the air core inductors from Madisound http://www.madisound.com and are a good bang for the buck.

Replace the ceramic resistors with Mills 5% wire wound resistors from Parts Connexion. http://www.partsconnexion.com/catalog/resistors.html

After thinking about other models which used one Peerless tweeter and two MW6503 mid-woofers I thought of the original SDA CRS speaker. It came with Peerless tweeters and was later changed to the sl1000 (silver face with Polk Audio stenciled in black letters). These have a slightly different sound than the sl2000. The sl1000 came out just after the Peerless were being used and are about the same size. So with this in mind I decided to try some of the original SDA CRS stereo crossover values for your project.

(SDA CRS stereo crossover)
resistor 1 = 5.6 ohms with (capacitor 3) 0.5uF mylar capacitor in parallel (*1)
resistor 2 = 2.7 ohms with 27uF electrolytic capacitor in parallel (*2)
capacitor 1 = 12uF mylar (and 750pF silver mica in parallel)
capacitor 2 = 20uF electrolytic (*3)
capacitor 3 = 0.5uF mylar (*1)
inductor 1 = 0.40mH

(*1) I did not have this part and substituted 0.47uF electrolytic
(*2) I tested with a 27uF mylar capacitor and it seemed smoother than 20uF electrolytic
(*3) I did not test this value because I felt it was a lower value due to only one mid-woofer being used

I felt these changes smoothed the response but made it sound quieter and less bright than your Monitor 7's.

In the end, I decided these were too many changes and additional cost so I decided on just changing resistor 1 to 3 ohms and removing capacitor 3. Finding what sounds best to you will take experimentation.

resistor 1 = 'A' in your Monitor 7 photo
resistor 2 = 'B' in your Monitor 7 photo
capacitor 1 = 'C' in your Monitor 7 photo
capacitor 2 = 'D' in your Monitor 7 photo
capacitor 3 = wired in parallel with 'A'
inductor 1 = 'E' in your Monitor 7 photo

SDA CRS stereo crossover from June 1984 (for reference)

[jakelm]

Thanks for all the info Polk65, I will read it carefully. I'm thinking just changing the value of resistor A to a higher value and leave the mids at 2.5ohm, and see how it sounds. Resistors are cheap. The caps are 12uf in the m10 which will be left alone.

You are fantastic , bringing me all of this great info...This will help me out a bunch.

Thanks
Jake

[jakelm]

Jake,



I took my pair of Monitor 5jr's apart and changed the crossover values to those in the "original Model 7" schematics. They have MW6502 mid-woofers and the sl2000's were replaced with Peerless tweeters which mounted pretty flat with two screws at opposite corners.

resistor 1 = 4.5 ohms
resistor 2 = 2.7 ohms
capacitor 1 = 12uF mylar
capacitor 2 = 34uF electrolytic
capacitor 3 = none
inductor 1 = 0.22mH (0.23 is used but I only have 0.22 available)


I could not find this. I could not find the schem with the 4.5ohm resistor 1. As a matter of fact I could not find any schem with the 4.5ohm in it.

Jake

P.S I emailed Ken to see what his thoughts were...But I think your right...leaving everything alone and changing the resistor A to a higher value (between 3.0 and 3.7ohm)

[jakelm]

Does the 4.5ohm on the 7's xover go to the peerless?...If so..thats a big difference than the 2.7ohm on the 10's.

cap 2 is the only other difference in the 7's and the 10's. In the 10's its 12uF, in the 7's its 34uF. What affects does this have on the mids?

Jake

[jakelm]

A couple of pics of the final project. Notice I went with the PExpress cabinet, which I must say is a very well built cabinet.

[jakelm]

Sorry the pics are so bad...not the greatest camera. The box is 22"w x 9"h x 13.5"d. Which is approx 1cuft, so no port and stuffed lightly. Sounds absolutly fantastic, especially with my new HK635. Absolutly seemless transition between the 7's and the center.

Jake

[jakelm]

Just replaced the crossover (original monitor10) with a 10A crossover, sounds much better. The 10A seems to have the same specs. Only difference is the color of the caps, the original 10 had black smaller caps with a large yellow one, while the 10A has blue caps. I'm starting to think the original 10 crossover was infected or defected, because the new 10A crossover has a much smoother sound.


Jake