Monitor 7Cs

bigaltx24

I picked up a set of Monitor 7Cs last week for a great price. They are in good shape, all the drivers work, and they sound real nice. I was thinking about recapping the crossovers, getting rid of the polyswitch, dynamatting the MWs etc.

Last Saturday I stopped by to see the tech that's working on an receiver for me. I mentioned that I had picked up a pair of 7Cs, the tech said that he loved the old Polk monitors, especially the 7s. I told him I was going to redo the crossovers and he told me to leave the 12uf mylar cap alone, just replace the 34uf electrolytic. He said he had recapped a couple of pair and that in his opinion changing the mylar to a film cap changed the voicing on these too much and both times he went back to the mylar.

Even those these have the SL2000 tweets, they don't seem near as peaky and grating as the ones that used to be in my 1Bs. I sat down tonight and did some serious listening to these little suckers and really like what I heard. Anyone have any experience leaving the mylars in these things?

westmassguy

The 7s are the sweet spot in the Monitor line. Very balanced from top to bottom.
Ask yourself: why, in almost every case, were the Mylar Caps Bypassed with small Silver Mica Caps? Answer: They suck, by todays standards and technology. Perhaps the combination of the poor quality Mylar, tempered the god-awful SL2000 Tweeter's 5db resonance peak. Quality Metalized Polypropylene Caps in combination with new RDO-194-1 or RDO-198-1 Tweeters, will blow the socks off the older tech.
There are some who prefer to conserve, when rebuilding crossovers, and will only replace defective components with like parts, while leaving the still functioning parts in place. That's fine, if you prefer the sound of older tech, are restoring a speaker to it's original state, or you're partially deaf. I'll opt for quality MP Caps and New Tweeters for the Vintage Polks every time. SL2000s are like fingernails on a chalk board to my ears.

bigaltx24

It surprised me but the mylar is not bypassed. I will probably pull a pair of RDO-198s out of my 1Bs and give them a try.

Mystery

I haven't upgraded 7c's but 7a's sounded very muddy.
even the highs were muffled until I replaced all caps and resistors.
After that, they sounded clean and clear.
So those caps can go bad.

Sl2000 is pretty decent at normal volume but when cranked up, it starts to become harsh.

teekay0007

bigaltx24 wrote: »

I will probably pull a pair of RDO-198s out of my 1Bs and give them a try.

The 198's are not a drop-in replacement for the SL-2000. To use the 198's here, you'll have to do some other crossover mod's first. The drop-in replacement for the 2000 is the RD-0194.

WMG is your man for knowing the crossover mod's of which I speak.

westmassguy

bigaltx24 wrote: »

It surprised me but the mylar is not bypassed. I will probably pull a pair of RDO-198s out of my 1Bs and give them a try.

They will not sound right. On the 7s, a shunt cap and new inductor must be installed in the Hi-Pass circuit to match the electrical requirements and frequency response of the 198s.

Mystery

westmassguy wrote: »

bigaltx24 wrote: »

It surprised me but the mylar is not bypassed. I will probably pull a pair of RDO-198s out of my 1Bs and give them a try.

They will not sound right. On the 7s, a shunt cap and new inductor must be installed in the Hi-Pass circuit to match the electrical requirements and frequency response of the 198s.

I thought 7's only needed additional 5.8uf cap.
Other upgrade threads don't mention inductor change.

westmassguy

Mystery wrote: »

westmassguy wrote: »

bigaltx24 wrote: »

It surprised me but the mylar is not bypassed. I will probably pull a pair of RDO-198s out of my 1Bs and give them a try.

They will not sound right. On the 7s, a shunt cap and new inductor must be installed in the Hi-Pass circuit to match the electrical requirements and frequency response of the 198s.

I thought 7's only needed additional 5.8uf cap.
Other upgrade threads don't mention inductor change.

Then they didn't follow the schematic. There is no Monitor 7 SL3000 Schematic, you have to follow the Monitor 5B SL3000 Schematic, which shows a .27mh Inductor, @.5ohms, and the 5.8uf Shunt Cap.

cnh

The older you get the LESS you can hear the flaws of the SL-2000s on Monitor 7s, in particular. And you almost come to appreciate the spike because you can only hear a little above that frequency? lol

You youngsters can hear above 15Khz, but I'm hanging by my fingers off the ledge of a skyscraper referred to as 15Khz and my grip is failing day by day!

As far as restoration; I don't like to alter the original much. How can a speaker be vintage if the crossover has been reworked so much that it's not longer a Monitor? Then again I'm a very "nostalgic" fellow. I love that OLD sound, it relaxes me.

Enjoy, whichever direction you take!

cnh

voltz

A lot of the crossover upgrades are to replace old worn out & maybe leaking cap's. so its just putting in some better ingredients to keep them going, but yes it does change the sound a little or tighten it up. but I do understand how you feel and think that is pretty cool too.

bigaltx24

cnh wrote: »

The older you get the LESS you can hear the flaws of the SL-2000s on Monitor 7s, in particular. And you almost come to appreciate the spike because you can only hear a little above that frequency? lol cnh

I know that's my problem, I've spent way to many years in machine shops and around race tracks. But I guess it is kind of a blessing, unless a tweeter is just god awful, it will sound fine to me.

I'm going to do a recap but leave the SL2000s in for now. Maybe try some RDO194s in the future.

Mystery

bigaltx24 wrote: »

cnh wrote: »

The older you get the LESS you can hear the flaws of the SL-2000s on Monitor 7s, in particular. And you almost come to appreciate the spike because you can only hear a little above that frequency? lol cnh

I know that's my problem, I've spent way to many years in machine shops and around race tracks. But I guess it is kind of a blessing, unless a tweeter is just god awful, it will sound fine to me.

I'm going to do a recap but leave the SL2000s in for now. Maybe try some RDO194s in the future.

Does that apply to men only?
I see a lot of older women screaming at their husbands but the husbands don't scream back for her to hear.
Or is that just the way it is?

bigaltx24

Part of it is just aging, but it's more prevalent in men because we tend to spend more time around loud things than women do.

bigaltx24

I recapped these with Daytons yesterday and replaced the polyswitch with a 1/2 ohm Mills. It did change the character of these speakers, but for the better. The highs are smoother and cleaner but the biggest difference was in the mids. After I did the first speaker I hooked both up to listen to the difference. The integration between drivers on the modded speaker was spot on, on the untouched speaker the upper mids were very weak.

voltz

give those new Cap's some burn in and they well get even better, 200+ hours sure made mine a lot better.
Have fun with those speakers!

Faustin

voltz wrote: »

give those new Cap's some burn in and they well get even better, 200+ hours sure made mine a lot better.
Have fun with those speakers!

^^^^
I agree with the burn in time. I recapped mine a few weeks ago and have been letting them play on a soft volume. They have really opened up and I really like there sound.

smglbrth

Trey redid my crossovers last year with Clarity Caps/Mills. Already had the 0194's in them and they are a sweet song for sure...