Original Monitor 10 Crossover Re-building

jakelm

GV#27 wrote: »

You could try the 1 ohm resistor but the caps value should also change but to what?maybe try some thing smaller.

Yes that diagram is a first order filter but it is highly unlikely that those component values are anywhere near optimum.Sorry to be such downer.:(

I understand GV, going from 2nd or 3rd order crossover to 1st order, the values of the caps and coils would change. I will install a 1.5ohm resistor with a 7uF bypass cap, and see how it sound.

This is so much fun......:)

jakelm

GV#27 wrote: »

Yes that diagram is a first order filter but it is highly unlikely that those component values are anywhere near optimum.Sorry to be such downer.:(

How did you come to this conclusion?

The value calculator suggest that both , the tweeter and midwoofer, with the current cap and coil values (removing the first 12uF), have a roll off at about the same Fr. The only thing that has changed is additional filtering (which I wouldnt think is needed with these drivers) and dB slope. I have ran a sweep with the mw6503's , with no filtering, and it seems to have a very flat responce from 60hz-1khz. The peerless from 2khz to 17khz. Both in my custom enclosure. I can ussually spot peaks with my ears. And if you cant "hear" the peaks, then why worry about it? So why all the additional filtering?

jakelm

I am starting to figure out why some of my mods are making the speaker sound better. The 2nd order high pass in the original crossover was not built for the Peerless, it was built for the sl1000 (which has very different characteristics). And the low pass was not built for the mw6503's.

Systems

jakelm wrote: »

I am starting to figure out why some of my mods are making the speaker sound better. The 2nd order high pass in the original crossover was not built for the Peerless, it was built for the sl1000 (which has very different characteristics). And the low pass was not built for the mw6503's.

Yes that would be a problem.:eek:

I agree messing around with this stuff is fun.:)

Systems

jakelm wrote: »

How did you come to this conclusion?

The value calculator suggest that both , the tweeter and midwoofer, with the current cap and coil values (removing the first 12uF), have a roll off at about the same Fr.

For several reasons crossover values calculated from a formula rarely give the intended response because it assumes the driver is a pure resistor with perfectly flat frequency response well beyond the target crossover point.A real driver however is not perfectly flat and its impedance changes with frequency as well their natural rolloff's must be considered in the design.

Sumbrada77

Hey jakelm, sounds like you are really playing with the crossover. The differences in version of the crossover I have not having the Cap/resistor in parallel, only a resistor I think is one of the changes that was done for the Peerless as compared to the SL1000 and SL2000. Raising the resistor there from 2.7 ohm to 3.5 ohms along with Clarity Cap (1) has made the tweeter
clearer and very smooth with the mids and low mids much less muddy as compared to the unmodifed one. Easy to hear in A/B testing. Also, you asked about the 0.01uF bypass Cap in the modified 5b crossover I did. I listened to the speaker with and without the bypass Cap and it might just be my ears but I thought the bypassed version was smoother in the treble and less harsh, so I kept it in. The Solens Caps are not near as smooth and clear
as the Clarity Caps.

jakelm

GV#27 wrote: »

For several reasons crossover values calculated from a formula rarely give the intended response because it assumes the driver is a pure resistor with perfectly flat frequency response well beyond the target crossover point.A real driver however is not perfectly flat and its impedance changes with frequency as well their natural rolloff's must be considered in the design.

I understand GV. I only wish I had the proper tools to measure the Peerless and mw6503. Or at least have the original specs of the crossover with the peerless. The only specs I could find were the ones earliest with the sl1000 not the peerless. And we all know there is major differences between the sl100 and the Peerless. I can ony go by what my 7b's with peerless have, but the overall resistance of the speaker between the 7's and the 10's are much different. Being the 7's use 1 mw6500 and the 10's have 2 mw6503's. I know that Polk claims the mw6503's are replacements for the older mw midwoofers, but I hear major differences between them, so the crossover must be different. However, I have concluded that my best results would come from combining what I know about my 7's HP filter, and the LP filter in the diagrams for the mw6503's. That would probably give me my best crossover design for the 2 drivers. I guess trial and error, is unavoidable here.

jakelm

only a resistor I think is one of the changes that was done for the Peerless as compared to the SL1000 and SL2000.

No, in the 10's, there is a knotch filter with an additional resistor, In the 7's and 5's there is only one resistor in series. I have removed that second knotch resistor and left just the coil. And remember I am remoding this crossover for a center channel in a completely different enclosure, mixing a Peerless tweeter with mw6503's woofers, not the original mw6500's. So by ear I can tell the crossover points have to be changed.

The Solens Caps are not near as smooth and clear

Well solens wil have to do...lol

jakelm

I know something doesnt sound right. I bet if I have an analyzer the graph would look like the Rocky Mountains, high peeks, low valleys, thoughout the intire 20hz-20khz spectrum

Systems

jakelm wrote: »

Or at least have the original specs of the crossover with the peerless.

Yes it sure would be nice if you could find this info.

jakelm

For my Peerless , I just copied close to what my 7b's have. 2.5ohm with 12uF cap in series , .04 coil in knotch , simple 2nd order.

But whats get me is this. Polk used for the midwoofers, be it the mw6503's, mw6502's or the mw6500's, a 1.55mH coil and a 34uF cap (on 90% of their crossovers). They used the same 2nd order low pass for both the single 8ohm driver AND the paralleled 8ohm driver (which is 4ohms). Now we know darn well the crossover points change dramaticly when going from 8 to 4ohm, so why use the same crossover for both 8ohm and 4ohm?

I know, from what I was told, that the crossover point for the mw's is ~2khz. But every calculation I put in for 2khz, gives me values no where close to the values on the crossover. Be it Butterworth, LR, Bessel or Chebychev.

Sumbrada77

Hello jakelm, the crossovers in my 10s (Peerless) are different than the 10s schematics on here. If you look at the crossover you posted of the 10s here mine is: from fuse (+) a 2.7 ohm resistor then 12uF Cap in Series (no 2.5 ohm and 12UF Cap in parallel) then the rest is the same. 0.4 mH inductor and 2.7 ohm shunted (parallel) across the tweeter, 34uF cap shunted (parallel) across the woofers and 1.5mH inductor in series with woofers (+).
(-) line runs to a 3 point intersection with one side of the 2.7 ohm resistor, one side of 34uF Cap and 2 lines to the woofers (one for each woofer). I hope this helps! I have it drawn but not scanned in yet. Skip

jakelm

With Butterworth, 1.55mH and 24uf , using 4ohms, gives me 1170hz for the low pass. That seems low. I could increase that by another 1000hz. But since I can't change the huge 1.55mH coil, I guess I'm stuck.

jakelm

Sumbrada77 wrote: »

Hello jakelm, the crossovers in my 10s (Peerless) are different than the 10s schematics on here. If you look at the crossover you posted of the 10s here mine is: from fuse (+) a 2.7 ohm resistor then 12uF Cap in Series (no 2.5 ohm and 12UF Cap in parallel) then the rest is the same. 0.4 mH inductor and 2.7 ohm shunted (parallel) across the tweeter, 34uF cap shunted (parallel) across the woofers and 1.5mH inductor in series with woofers (+).
(-) line runs to a 3 point intersection with one side of the 2.7 ohm resistor, one side of 34uF Cap and 2 lines to the woofers (one for each woofer). I hope this helps! I have it drawn but not scanned in yet. Skip

Thanks Sum. Thats excacly how I have mine. Its just baffling to me why they would go with the same Lp 2nd order filtering for both 8ohm and 4ohm. There is a 1000hz different crossover point between my 10 crossover and my 7 crossover. With this difference I will never be able to get a correct tember match between my center (10) and mains (7b's)

jakelm

This is what I moded it to. Deleted bypass 12uF cap and deleted 2.7ohm knotch resistor.

This wil have to do. As close as I can get it without replacing the big 1.5mH inductor.

Sumbrada77

No problem jakelm, I replaced the first 2.7 ohm (2.5 ohm on yours) with a 3.5 ohm and left the rest the same. Just as a try. It seems better, could be from all the other updated pieces also. Did you hear a difference taking out the 2.7ohm connected to the 0.4 mH? i wonder if some of the differences are the original MW6500 9 (i have) vs the MW6503s. If they are a little stiffer it would make a difference.

Sumbrada77

I'm wondering if cabinet size, design is also changing its sound. Closed cabinets can be finicky to the drivers. From your experience I am sure you know better than I.

jakelm

Sumbrada77 wrote: »

No problem jakelm, I replaced the first 2.7 ohm (2.5 ohm on yours) with a 3.5 ohm and left the rest the same. Just as a try. It seems better, could be from all the other updated pieces also. Did you hear a difference taking out the 2.7ohm connected to the 0.4 mH? i wonder if some of the differences are the original MW6500 9 (i have) vs the MW6503s. If they are a little stiffer it would make a difference.

Taking out the 2.7ohm thats in series with the .04 inductor gave less attenuation for the tweeter, I think it sounds more "open".

There is a difference between the 6500 (which I have in my 7's) and the 6503 (which I have in my center). Stiffer, yes. Less range? I dont think so, but using the same crossover for both, I dont think is right, somethings needs to be changed. Looking at the version 2 crossover, Polk went with a 1.75mH inductor with a 27uF cap, for the 6503. I think this is correct. But like I said, unless I want to "try" to change out the 1.55 inductor, I am pretty much stuck with what I have.

jakelm

Sumbrada77 wrote: »

I'm wondering if cabinet size, design is also changing its sound. Closed cabinets can be finicky to the drivers. From your experience I am sure you know better than I.

I tuned ported my center channel. 1cuft enclosure with a 2" port 8"s long. So its tuned pretty low for a center channel. Like the Pr.

ben62670

jakelm wrote: »

I tuned ported my center channel. 1cuft enclosure with a 2" port 8"s long. So its tuned pretty low for a center channel. Like the Pr.

When are you going to post a pick of your franken polk center?

jakelm

I did. A while back. Post #39

http://www.polkaudio.com/forums/showthread.php?t=45852&page=2