Want to Buy: Monitor 7, Series 2 crossover

fiddlerman

I'm looking to purchase a Series 2 crossover for a Monitor 7. Does anyone here know where I can locate one?

This connected to an SL-2500 tweeter. It has quite a few more capacitors than the earlier Model 7 crossovers.

Thanks in advance for your help!

Here's a photo of what it would look like:

Nightfall

Nothing I can find on Ebay right now, I'll try to remember to keep an eye out for you.

Also be advised of the possibility the two different models used two different mid woofers. Might not be just replacing crossovers and tweeters.

zingo

How about building a new pair of crossovers with matching components? They won't be stock Polk, but they will sound better, and they will also be the same between the two speakers.

fiddlerman

If I can't find a matching crossover, I'm planning on building on top of my existing crossover so it matches the newer one. The problem is where to put the extra capacitors. There'd have to be some serious rewiring done.

fiddlerman

Thanks, Nightfall!

I'm actually running this new crossover right now with an SL-2000 tweeter and it doesn't sound half bad. This is perhaps heretical to say, but if you didn't tell me, I probably wouldn't be able to tell the difference. In other words, I'm trusting any possible mid-driver discrepancy won't be a huge issue.

One thing, though. I seriously need to crank my bass knob to get a lively response (three o'clock), something I hope new caps will alleviate.

Nightfall

You might be interested in the bigger guys, are these your only Polks?

fiddlerman

Cost is the issue. I'm already in $15 for the first crossover and $100 for a pair of RD0-198s. Speakers were about $40 (craigslist). It'd be nice to keep everything below $200. I don't want to chase my tail through the looking glass.

zingo wrote: »

How about building a new pair of crossovers with matching components? They won't be stock Polk, but they will sound better, and they will also be the same between the two speakers.

\

Nightfall

fiddlerman wrote: »

This is perhaps heretical to say, but if you didn't tell me, I probably wouldn't be able to tell the difference. In other words, I'm trusting any possible mid-driver discrepancy won't be a huge issue.

Your listening skills will improve over time as you learn and your equipment improves.

zingo

fiddlerman wrote: »

If I can't find a matching crossover, I'm planning on building on top of my existing crossover so it matches the newer one. The problem is where to put the extra capacitors. There'd have to be some serious rewiring done.

Get some through-holed plated breadboard, buy the a pair of 12uF caps, 27uF caps, 8uF caps, 2.7ohm resistors, and use the inductors from the old crossovers. Solder it all together based on the schematic provided on this forum, and screw them back into the original position!

fiddlerman

Seems reasonable enough.

fiddlerman

Zingo, I see you have studied the schematic. I can probably build all this on top of the existing crossover chassis.

I don't see a polyswitch in this newest crossover. I guess that something they just cut out of the new design.

I'm ordering the components through Parts Express, which is supposed to be a reputable outfit. My electronics friend mentioned 1 % polypropelene and sonocaps as possible options. Any advice you can give me on that?

Also, Mills or Munsdorf resistors seem to be the order of the day.

Nightfall

Sonicaps, Mills, and Mundorf are all often recommended here.

zingo

At Parts Express, Dayton Audio film caps and Mills resistors would fit your needs, are reasonably priced, and have the values you are needing. A call to Sonicraft would get you set up very nicely for a little more money, and they can make plenty of recommendations within their stock at a given price point.

fiddlerman

Would you recommend polypropylene caps?

fiddlerman

I'm pretty committed to the Polk 7s, Nightfall. 10s were an option, but I decided to go for flatness, accurate imaging and clarity over a big bottom. Also, they fit well in my living room (though the better half already thinks they're too big). My ideal for bass reproduction would be the original Large Advents, which did not have outstanding treble but really set a standard for full but natural bass. I know the 7s won't match that, but I'm experimenting with the tone controls and speaker placement and hoping new caps will bring things out. For my jazz and classical, I don't need massive, just natural and rich-toned.

fiddlerman

Real quick, why are "mylar" caps specified? Do they still exit, should I search specifically for them, and what may be a suitable contemporary alternative?

Nightfall

fiddlerman wrote: »

I'm pretty committed to the Polk 7s, Nightfall. 10s were an option, but I decided to go for flatness, accurate imaging and clarity over a big bottom. Also, they fit well in my living room (though the better half already thinks they're too big). My ideal for bass reproduction would be the original Large Advents, which did not have outstanding treble but really set a standard for full but natural bass. I know the 7s won't match that, but I'm experimenting with the tone controls and speaker placement and hoping new caps will bring things out. For my jazz and classical, I don't need massive, just natural and rich-toned.

They are a lot of peoples favorites and a great speaker. I misjudged your bass comment.

zingo

Mylar were the best available at the price point at the time, but a film/metalized poly cap is what you want now. They skys the limit when it comes to crossover component prices, so pick a dollar amount, and find what fits into that. New components will automatically sound much better than the old stuff; even before buying exotic parts.

westmassguy

Fiddlerman, this is your third post on the same subject more or less. You have the two, complete, original, MATCHING crossovers.
You purchased one additional Series 2 crossover, which doesn't match the two you already have. I sent you replacement binding posts, so the one original crossover with the broken binding post will be fully functional once you install the replacement binding post. Instead of buying yet another Series 2 crossover, rebuild the two originals that you already have. If you go conservative, with Dayton MP Caps, they will all fit on the existing board, if you mount the replacement resistors on the bottom or the circuit board. You can use 1% Dayton MP Caps for the H-Pass/Tweeter section, and 5% Dayton MP Caps for the Lo-Pass, woofer section. Dayton doesn't make a 5.8uf cap. The closest they have is a 5.6uf, or you can parallel a 2.7uf and 3.0uf which will get you even closer to the 5.8uf. For the Lo-Pass, Dayton makes a 33uf 5% which will work fine. The Poly switch and 2 ohm resistor can be handled two ways. You can replace the Polyswitch with a 0.5 ohm 12 watt Mills Resistor, and replace the 2 ohm Sandcast Resistor with a 2 ohm 12 watt Mills Resistor. The alternate, would be to jump out the Polyswitch with a piece of #16 or #18 gauge copper wire, and replace the 2 ohm Sandcast Resistor with a 2.5 ohm mills 12 watt Resistor. Once again, all resistors should be mounted to the bottom of the circuit board to make room for the Caps. You will also need to replace the small 0.22mh Inductor (Coil) with a .27mh inductor, with a DCR of 0.5 ohms.
If you'd like to go with better quality MP Caps in the H-Pass section, Sonicap makes the exact value, 5.8uf Cap, and the 12uf Cap. The Sonicaps will also fit on the existing Circuit board without the need for an additional risers or remote mounted boards. The Dayton 33uf MP Cap can still be used in the Lo-Pass Section along with the Sonicaps.

fiddlerman

WestMassGuy,

Yes, my thoughts on this are evolving, and in no small way because of your guidance and suggestions.

I would not have opted for the RD0-198s over the RD0-194s without having first heard your opinion on the matter. But now that I have, I'd glad I did. I'm going to have some very special speakers.

If you read my posts, you will see that I am planning on using my original crossover chassis to mount the electronics for the upgraded crossovers. After all, they have indentical matching inductors. The odd SL-2500 crossover will be put back on the market, but if I were to find a second one, I don't see why I wouldn't just snatch it up and then swap out the electronics on both. After all, they're already set up. But for the time-being, any discussion of the new crossover is academic. I'm going to upgrade the old ones, so everything's cool.

Having looked at the schematic for the revised crossover (schematic_m7s_rev2.pdf‎), I have taken inventory and found the matching values for two of the three capacitors in the Dayton line --12 and 27 uf caps. (I'm passing on the Sonicaps -- those will blow my budget.) There is no exact match in the Dayton line for the 8 uf, but there is an 8.2 uf, so I'm wondering if I can get away with using it. (This particular cap is wired to to the 2.7 ohm resistor, BTW.)

As far as I can see, there is no polyswitch on the SP-2500 crossover, so I'm wondering if we are looking at the same schematic. Mine is dated Mar 26, 1980. I could be reading this wrong, but I believe they removed that dubious feature for the SP-2500.

I am relieved to discover that both schematics list the HW6502 woofer, so I'm in the clear there.

This has been an adventure in learning. Of course, the real adventure begins when my new tweeters arrive and I get to fire up the soldering iron. Can't wait to put this all together.

Thanks,

F

westmassguy

fiddlerman wrote: »

WestMassGuy,

Yes, my thoughts on this are evolving, and in no small way because of your guidance and suggestions.

I would not have opted for the RD0-198s over the RD0-194s without having first heard your opinion on the matter. But now that I have, I'd glad I did. I'm going to have some very special speakers.

If you read my posts, you will see that I am planning on using my original crossover chassis to mount the electronics for the upgraded crossovers. After all, they have indentical matching inductors. The odd SL-2500 crossover will be put back on the market, but if I were to find a second one, I don't see why I wouldn't just snatch it up and then swap out the electronics on both. After all, they're already set up. But for the time-being, any discussion of the new crossover is academic. I'm going to upgrade the old ones, so everything's cool.

Having looked at the schematic for the revised crossover (schematic_m7s_rev2.pdf‎), I have taken inventory and found the matching values for two of the three capacitors in the Dayton line --12 and 27 uf caps. (I'm passing on the Sonicaps -- those will blow my budget.) There is no exact match in the Dayton line for the 8 uf, but there is an 8.2 uf, so I'm wondering if I can get away with using it. (This particular cap is wired to to the 2.7 ohm resistor, BTW.)

As far as I can see, there is no polyswitch on the SP-2500 crossover, so I'm wondering if we are looking at the same schematic. Mine is dated Mar 26, 1980. I could be reading this wrong, but I believe they removed that dubious feature for the SP-2500.

I am relieved to discover that both schematics list the HW6502 woofer, so I'm in the clear there.

This has been an adventure in learning. Of course, the real adventure begins when my new tweeters arrive and I get to fire up the soldering iron. Can't wait to put this all together.

Thanks,

F

As I told you originally, the values between the two series are different. In order to convert your two older crossovers to accept the RDO-198, you need to look at the Monitor 5b SL3000 mod (schematic_m5b_sl3000mod), for the correct values you need. I mentioned this before. Do not go by the values on your newer crossover, or the Monitor 7 rev2, with the SL2500.

fiddlerman

Roger that. But I'm somewhat confused here: if the RD0-198 is the drop-in replacement for the SL-2500, why wouldn't I just use the SL-2500 crossovers?

westmassguy

fiddlerman wrote: »

Roger that. But I'm somewhat confused here: if the RD0-198 is the drop-in replacement for the SL-2500, why wouldn't I just use the SL-2500 crossovers?

You certainly could, but you only have one. You would have to buy a matching Model/Rev 2 Crossover, and still be faced with upgrading all the caps. What I'm saying is, you already have two functional crossovers that can be upgraded to "TL" status.
Why spend additional money on another rev 2 crossover, when the ones you have can be modified

fiddlerman

WestMass, I take your word on the proper crossover schematic. I'm sure you've done this mod quite a few times with great success. If it's mo' betta, I'm for it.

Looking at the SL-3000 upgrade schematic, I find its architecture to be practically identical with the SL-2000 XO, so it's a very easy swap, apart from bridging the resistor.

Thanks,

F

BTW. I wasn't planning on purchasing a second XO, but on rebuilding my original ones from the ground up. The only question was which design to use. It seemed logical to use the SL-2500 upgrade schematic, which is designed specifically for a M7, rather than the SL3000 design, which is designed for an M5. I guess there's no practical difference between the 5 and 7 except the cabinet size.

westmassguy

It's essentially the same crossover. You'll also need the small inductor for the Hi-Pass. Parts Express has all those parts