Retrofitting Monitor 7Bs with Peerless tweeters.

fiddlerman

Hi All,

I recently purchased a pair of Monitor 7Bs, a craigslist steal for $35. These came with the beveled fronts, crossovers without the external fuse and the dreaded SL-2000 tweeters

I'm finding the SL-2000s a little too aggressive, so I have located a pair of Peerless tweeters on eBay and hope to have them in hand soon.

I'm aware that I will have to made modifications to the tweeter hole in the front of the speaker and am planning to saw out a larger opening to accommodate what I assume will be a larger circumference magnet.

My question is, what modifications do I need to make to the crossovers in order for them to be compatible with the Peerless tweeters? My guess is it's a different resistor, which would alter the crossover frequency.

Can I retrofit my current crossovers or will I need to search for a pair of vintage 7A crossovers?

Lastly, is this a worthwhile project (since the used Peerlesses are cheaper than a new pair of RDO-194's)? It seems I'm searching for a legendary sound akin to a sonic holy grail. Is this a fool's errand or am I on a reasonable trek?

Any assistance or advise will be gratefully accepted. Thank you in advance.

Fiddlerman

F1nut

Forget the Peerless, order the RD0194-1. It's a much better tweeter, fits perfectly and requires no crossover changes.

Mystery

Either leave them as is or replace with correct replacements (RDO-194).
You can sell the SL-2000's and recoup more than half of the RDO-194 cost.

westmassguy

Peerless were great tweeters, but they're 30+ years old now. As F1 and Mystery have said, the RDO-194-1s are much better. If you plan on recapping the crossovers, you can also modify them for the RDO-198-1, which is even better than the 194.

fiddlerman

What particular qualities make the 198s better speakers?

westmassguy wrote: »

Peerless were great tweeters, but they're 30+ years old now. As F1 and Mystery have said, the RDO-194-1s are much better. If you plan on recapping the crossovers, you can also modify them for the RDO-198-1, which is even better than the 194.

Nightfall

For reference there are also new Peerless tweeters, albeit made by another company.

http://w.mawebcenters.com/midwestspeaker/ecommerce/home-audio/tweeters/mw-audio-mt-4115-1-inch-dome-tweeter.html

Out of curiosity, to the knowledgeable here, what does age do to a tweeter?

westmassguy

fiddlerman wrote: »

What particular qualities make the 198s better speakers?

Smoother response, more detail, more musical.

westmassguy

Nightfall wrote: »

For reference there are also new Peerless tweeters, albeit made by another company.

http://w.mawebcenters.com/midwestspeaker/ecommerce/home-audio/tweeters/mw-audio-mt-4115-1-inch-dome-tweeter.html

Out of curiosity, to the knowledgeable here, what does age do to a tweeter?

The Peerless have treated cloth domes, which can deteriorate with age, and they also contained ferrofluid, which can oxidize.

Nightfall

Interesting. I wonder what would be involved in cleaning out the old fluid and replacing it?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=340-544

Does ferrofluid serve any other purpose than heat dissipation resulting in increased power handling?

westmassguy

Nightfall wrote: »

Interesting. I wonder what would be involved in cleaning out the old fluid and replacing it?

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=340-544

Does ferrofluid serve any other purpose than heat dissipation resulting in increased power handling?

I don't believe that would be possible with the Peerless, since the dome is glued directly to the front steel bezel. You would end up destroying the fabric, not to mention the fine coil wires. Ferrofluid serves two purposes, first it allows heat to transfer from the coil directly to the surrounding metal, thereby increasing it's power handling, and second, it can help to mitigate resonances at or near where the coil is bonded to the fabric.

Nightfall

westmassguy wrote: »

I don't believe that would be possible with the Peerless, since the dome is glued directly to the front steel bezel. You would end up destroying the fabric, not to mention the fine coil wires. Ferrofluid serves two purposes, first it allows heat to transfer from the coil directly to the surrounding metal, thereby increasing it's power handling, and second, it can help to mitigate resonances at or near where the coil is bonded to the fabric.

Maybe I should have been looking for SL2000's instead of Peerless all along? I may give the mid west replacements a try some day. Thanks for your knowledge.

Apologies to OP for the derailment.

westmassguy

Nightfall wrote: »

Maybe I should have been looking for SL2000's instead of Peerless all along? I may give the mid west replacements a try some day. Thanks for your knowledge.

Apologies to OP for the derailment.

Run, don't walk away from the SL2000 Tweeters. Unless your hearing is limited to 10KHz. The SL2000, and to a lesser degree the SL1000 have a nasty resonance peak around 12-13 KHz. Some seem to like it, but to my ears it's like finger nails on a chalk board. I've had several of my customers give high marks for the Peerless clone that Midwest Sells. I was also told, that Polk Customer Service recommended the Midwest Clone as the replacement for the Peerless.

Nightfall

westmassguy wrote: »

Run, don't walk away from the SL2000 Tweeters.

My comment is more in reference to the ability to switch to RDO's.

westmassguy wrote: »

I've had several of my customers give high marks for the Peerless clone that Midwest Sells. I was also told, that Polk Customer Service recommended the Midwest Clone as the replacement for the Peerless.

This is reassuring.

fiddlerman

Could you kindly point me towards information about modifying the crossovers to accept the SD0-198s?

Thanks!

westmassguy wrote: »

Smoother response, more detail, more musical.

westmassguy

fiddlerman wrote: »

Could you kindly point me towards information about modifying the crossovers to accept the SD0-198s?

Thanks!

http://www.polkaudio.com/forums/showthread.php?38755-POLK-AUDIO-Speaker-Wiring-Schematics-amp-More-ALL-MODELS-except-SDA
Look for the Monitor 5B SL3000 Mod. Your crossover should be the same as the original 5B, except for the fuses. Since your 7Bs have fuses, the resistor will most likely be the original 2.7 ohm instead of 2 ohms. When rebuilding your crossovers, you'll be replacing the 2.7 ohm, 5 watt Sandcast resistor with a Mills MRA -12 or Mundorf Mox 2 ohm. You'll be adding a 5.8uf cap (shunting the resistor), and changing the 12 uf cap. Both should be Metalized Polypropylene. The Hi-Pass Shunt inductor must be changed from 0.23mh to 0.27mh 0.5 ohms. If you can't find the 0.27mh inductor with a 0.5 ohm value, you'll need to pad it with a resistor, to total 0.5 ohms, otherwise the voicing of the tweeter will not be correct. The Lo-Pass 34uf Cap should also be replaced with a Metalized Polypropylene.

westmassguy

Misread your original post, your 7s don't have the external fuses. The Polyswitch should be removed, and replaced with a 0.5 ohm resistor, same quality Mills or Mundorf.

StantonZ

I recently replaced some SL2000s with RDO-194s and am very happy. I also replaced the polyfuse with a 0.5 Ohm resistor when I re-built my cross-overs. The polyfuse resistance was well over 1 Ohm; that did as much for my highs as re-capping did for my lows.

fiddlerman

I want to thank everyone for contributing to this discussion. I have some deciding to do now -- the 194s or the 198s -- but I've definitely opted against buying the used Peerless tweets.

This brings up an interesting issue as regards vintage audio: the mystification that surrounds certain audio legends. Any discussion of Monitor speakers will eventually bring up the subject of Peerless tweeters and how coveted they are. Yet it's entirely possible that Monitors with the 194 or 198 upgrade might sound as good or even better than the Peerless. However, they are not surrounded by the same wow factor, probably because they can be easily accessed. Do the 194s sound better than the Peerless? Of course there is no way to tell, or to easily compare subjective experiences, or to separate anyone from their proprietary opinion regarding their own personal property. Thus the Peerless became my personal holy grail, until I was talked down from my quest by you guys.

The truth is out there, but it's certainly an elusive thing.

I'll probably opt for the 194s. I don't want to spend too much money on this pair of speakers, so I will probably take the safe option. But I'm living with the SL-2000s right now and it's not too bad. Orchestral strings can sound a little shrill and sometimes I'll hear some edginess in a jazz vocal. But mostly these speakers have been a revelation, a huge upgrade from my Cambridge Model Sixes. I feel like my entire music collection has had a scrim raised from it. It's like the restoration of the Sistine Chapel. I'm amazed by how my detail I have been missing and how lively and present everything feels.

westmassguy

The 194s are a no brainer, pop them in, instant gratification. The Monitor 7s Are arguably the most balanced of all the Vintage Monitor Series. Crossovers can come later, but everything is cumulative. There are other upgrades for the Monitors, Dynamatting the Drivers, Gluing the Magnets, Hurricane Nuts, or Larry's Rings. All can be done at once or spread out when you have the time and the dough.

westmassguy

DSkip wrote: »

If you want all-original, plug and play speaker, then Peerless is the way to go. If you don't mind throwing more money into them, then RD0's are the way to go. The Peerless have the 'mystique' because they were most favored stock form of the speaker.

How do you figure the Peerless is plug and play? They're 7Bs, with the original SL2000s. He'd have to modify the crossover, the tweeter opening, and modify the recess in the baffle to accommodate the Peerless. The RDO-164-1 is as plug and play as it gets.

Nightfall

westmassguy wrote: »

How do you figure the Peerless is plug and play? They're 7Bs, with the original SL2000s. He'd have to modify the crossover, the tweeter opening, and modify the recess in the baffle to accommodate the Peerless. The RDO-164-1 is as plug and play as it gets.

I think he means zero upgrades. Buy them and play them.

westmassguy

Nightfall wrote: »

I think he means zero upgrades. Buy them and play them.

That makes no sense. You cannot put Peerless Tweeters in 7Bs without modifications.
The RDO-194 will drop in with zero modifications

Nightfall

westmassguy wrote: »

That makes no sense. You cannot put Peerless Tweeters in 7Bs without modifications.
The RDO-194 will drop in with zero modifications

I also don't think he means with these 7Bs, he means find whatever pair you're looking for with Peerless to begin with if you're not planning on modifying or putting money into the speakers.

fiddlerman

Stanton,

When you say changing the polyfuse for a resistor "did as much for my highs," do you mean smooth them out or boost them?

After installing the RD0-194s, I plan on recapping my crossovers and the polyswitch is an issue to be contended with.

This polyswitch is a substitute for the original fuse used in the earlier crossovers, I assume, and is some kind of protection against spikes?

westmassguy

fiddlerman wrote: »

Stanton,

When you say changing the polyfuse for a resistor "did as much for my highs," do you mean smooth them out or boost them?

After installing the RD0-194s, I plan on recapping my crossovers and the polyswitch is an issue to be contended with.

This polyswitch is a substitute for the original fuse used in the earlier crossovers, I assume, and is some kind of protection against spikes?

fiddler...when the Polyswitches have tripped a few times, their resistance increases. Excessive use of the gain/volume knob usually causes this. Continued tripping only makes matters worse. The Polyswitches only protect against excess current going to the tweeter. They won't trip due to DC for example, so their usefulness is debatable. That's one of the reasons most of us remove them, and replace them with a 0.5 ohm Mills or Mundorf Resistor. We also have quality amplification to go along with the switch-out.

zingo

I have redone the crossovers on quite a few pairs of vintage Polks including my current SRS 2s, and have also just removed the poly switch. I never found it necessary to replace it with a resistor, although it does have a small resistance, and removing it has always been an improvement in high frequency fidelity and clarity.

Usually I just twist the polyswitch so the legs of it contact each other and short, solder them together, then cut off the body of the switch above that.

westmassguy

Some people like the additional treble boost, however, the 0.5 ohm resistance is part of the overall resistance of the Hi-Pass circuit. Whether it's the provided by the polyswitch, or the resistor directly downstream. By jumpering or removing it, you're changing the voicing of the tweeter.

fiddlerman

I don't think I would make any mods that would accentuate the highs in my system, particularly after I've just installed tweeters to attenuate said highs.

I had another bad scrape with my SL-2000s today: Carole King's "Tapestry," remastered version. There is no way she sounded that screechy and sold that many millions of records. So something must be wrong with my speakers.

westmassguy

DSkip wrote: »

This is what I meant mass. I was talking about a prospective purchase. I could've been a bit more clear with that delivery, no?

I understand now, but even the Peerless models can benefit greatly from crossover upgrades.

westmassguy

fiddlerman wrote: »

I don't think I would make any mods that would accentuate the highs in my system, particularly after I've just installed tweeters to attenuate said highs.

I had another bad scrape with my SL-2000s today: Carole King's "Tapestry," remastered version. There is no way she sounded that screechy and sold that many millions of records. So something must be wrong with my speakers.

fiddler...you should have the replacement binding posts in a day or two. Are you using one of the newer crossovers with the older one?