Monitor 7 future upgrades. And an SDA question.

mikemokr

Hello all,

I bought Monitor 7s new circa 1987-88 (s/n 35XXX, Silver Coil tweeter ... in one thread when I last posted here nearly 12 years ago I said they were 7Cs but I have no idea how I determined that, nor whether it's true) and have gently used them ever since. Absolutely love 'em and will never get rid of them. Now I am curious about potential future mods - no rush as they sound as good as ever (even better over time in fact as I've upgraded the power to them, added a subwoofer, etc), but just figuring that with age will eventually come the need for upgrades.

From other threads like this one re M 10s ...
http://www.polkaudio.com/forums/showthread.php?155376-back-with-my-10-s

... I have a good sense of the range of mods. My main questions are how folks would prioritize them, a ballpark on what the parts would cost, and which mods I might be able to do myself, given that I can handle a soldering gun but have no expertise in speakers and generally am not great with my hands.

Sounds like replacing the tweeters would be pretty simple (RDO-194-1? With CP discount, what, maybe $60 or more like $100/pair?) but that perhaps upgrading some other things would provide more sonic bang for the buck. And, assuming I have the SL2000s now, I don't hear a problem with harshness at the high end as reportedly some perceive with these, but then again I'm at the age where my doc tells me I may not be hearing the very high end at all ...

Meanwhile, I've got my eye on a pair of SDA CRS+ that are for sale near me - single tweeter, with interconnect and the original stands. As I expect to set up a second HT system in the next year in a new game/hangout room I am starting to look for gear for it. The Monitor 7s might go down there because the room is too narrow for good SDA placement. The family room, where my current HT rig is, is 26x18, with the 18' wall where the CRS+ would be - wide enough with a couple feet to spare, as I understand it. My main questions here are power requirements - my new amp is 75 wpc, all channels driven, at 4 ohms (but in the M 7 specs its says the impedance is 8 ohm, for which my amp is rated 110 wpc) - and whether the CRS+ would be big enough for this room. I use the rig probably 70/30 stereo audio/5.1 movies, nothing at ear-bleeding volume. I figure since the M 7s are so pleasing there (especially with sub), the CRS+ should be fine too, but I'd appreciate input before I start trying to calculate the WAF for this prospective purchase


p.s. as I wouldn't be surprised to see westmassguy in this thread, I'll mention I'm an eastmassguy ...

Mystery

There are several threads on upgrade but new capacitors (and may be resistors) is the first thing to do followed by tweeters (RDO-194 or 198 withe extra 5.8uf capacitor), magnet epoxy, dynamat baskets etc...

If you are eying a pair of CRS+, forget upgrading 7's and save that for the CRS+.
Get the CRS+ and use 7's as surrounds or in a 2nd system.
CRS+ are much better than 7's.

75 wpc at 4 ohms and 110 wpc at 8 ohms???
It should be the other way around but if that 75 watts is real watts, then it's enough.

Jimbo18

I have a pair of Monitor 7C's, I am only sure because they still have the identification label on the back, and they have SL2500 tweeters in them. I was told that SL2500's would require the RDO198 replacement tweeter. If you have SL2000's, you would need the RDO194 replacement.

However, if you upgrade the caps, I have read that it's recommended you go with the values for the RDO198, as that seems to be considered the better sounding tweet. But of course, if you have SL2000's, doing that would require that you do buy the tweeters right away.

But Mystery has the best suggestion if you get the CRS+.

gmjungbluth

Monitor 7s are a lot of fun and do sound great.

Here is my list of prioritized mods:

1. epoxy on the MW magnets
2. gasket tape or moretite around the drivers' seals with the cabinet
3. tweeter
4. recap, new resistors
5. Larry's rings or hurricane nuts


Good luck and enjoy!

G

mikemokr wrote: »

Hello all,

I bought Monitor 7s new circa 1987-88 (s/n 35XXX, Silver Coil tweeter ... in one thread when I last posted here nearly 12 years ago I said they were 7Cs but I have no idea how I determined that, nor whether it's true) and have gently used them ever since. Absolutely love 'em and will never get rid of them. Now I am curious about potential future mods - no rush as they sound as good as ever (even better over time in fact as I've upgraded the power to them, added a subwoofer, etc), but just figuring that with age will eventually come the need for upgrades.

From other threads like this one re M 10s ...
http://www.polkaudio.com/forums/showthread.php?155376-back-with-my-10-s

... I have a good sense of the range of mods. My main questions are how folks would prioritize them, a ballpark on what the parts would cost, and which mods I might be able to do myself, given that I can handle a soldering gun but have no expertise in speakers and generally am not great with my hands.

Sounds like replacing the tweeters would be pretty simple (RDO-194-1? With CP discount, what, maybe $60 or more like $100/pair?) but that perhaps upgrading some other things would provide more sonic bang for the buck. And, assuming I have the SL2000s now, I don't hear a problem with harshness at the high end as reportedly some perceive with these, but then again I'm at the age where my doc tells me I may not be hearing the very high end at all ...

Meanwhile, I've got my eye on a pair of SDA CRS+ that are for sale near me - single tweeter, with interconnect and the original stands. As I expect to set up a second HT system in the next year in a new game/hangout room I am starting to look for gear for it. The Monitor 7s might go down there because the room is too narrow for good SDA placement. The family room, where my current HT rig is, is 26x18, with the 18' wall where the CRS+ would be - wide enough with a couple feet to spare, as I understand it. My main questions here are power requirements - my new amp is 75 wpc, all channels driven, at 4 ohms (but in the M 7 specs its says the impedance is 8 ohm, for which my amp is rated 110 wpc) - and whether the CRS+ would be big enough for this room. I use the rig probably 70/30 stereo audio/5.1 movies, nothing at ear-bleeding volume. I figure since the M 7s are so pleasing there (especially with sub), the CRS+ should be fine too, but I'd appreciate input before I start trying to calculate the WAF for this prospective purchase


p.s. as I wouldn't be surprised to see westmassguy in this thread, I'll mention I'm an eastmassguy ...

mikemokr

Belatedly, thanks much all. (Mystery, yes I got wattage/ohms confused ... and yes I believe it's a real 75 wpc)

Gotta see if I can do the CRS+ given a bunch of other recent purchases lately ...

F1nut

Do not use Mortite, period. In fact, there's no need to change the stock gaskets at all as long as they not damaged.

F1nut

Gotta see if I can do the CRS+ given a bunch of other recent purchases lately ...

Return the other purchases and get the CRS+.

westmassguy

Did someone mention my name LOL? I'm west of Woosta, so we don't talk funny out here. The 7s are arguably the best of all the Monitors from that era. Very balanced from top to bottom. The RDO-194-1s are drop-in replacements, so no modifications needed, and instant gratification. I'd opt for the 198s though, much more detailed, but will require modifications to the crossover. The tweeters are $48.00 each with free shipping, and well worth it. For the crossovers, I'd go with Sonicaps and Mills resistors. For the 198 Mod, you're looking at around $200.00+ for parts, unless they have a sale going on. Some prefer Claritys, and Mundorf Mox resistors, but they don't have the exact values that Sonicraft has for the Caps and Resistors.
As F1 says, don't replace the original gaskets unless you have to. Larry's Rings or Hurricane Nuts with Phillips Head machine screws or Cap screws, depending on your taste. Re-glue the magnet assemblies, either with epoxy, or Loctite Power Grab. Dynamat all the basket frames. Consider replacing the binding posts. Check and internally reseal the cabinets with the Loctite if necessary, and secure the Dacron batting above the PR opening.
On the other hand, the CRS+s are sweet, and don't show up that often around these parts, let alone with the original stands. They don't go as low as their big brothers, but when fully modded, they are impressive. If the 7s fill the room now, the CRS+s will do at least as well, and go deeper.
If you're up for the drive (I'm 90 miles from Bahston), I'd be more than happy to help you with any of the mods. PM me if you want.

westmassguy

Forgot to add, find out which CRS+s they are. Blade/blade or pin/blade on the interconnect. The crossovers are a lot more expensive to upgrade on the older blade/blade model.

mikemokr

Thanks very much WMG for the info and generous offer of help.

westmassguy wrote: »

Forgot to add, find out which CRS+s they are. Blade/blade or pin/blade on the interconnect. The crossovers are a lot more expensive to upgrade on the older blade/blade model.

Any way to tell from this?

http://images.craigslist.org/01515_3v3ZKHiHizI_600x450.jpg

And now that I look at that more closely, I notice that there's a hole where one of those three nipple-like things should be (all three are there in the photo of the other speaker). What is that and what issues might there be with it missing?

TennMan

I see two extra bolts sticking out the back of those CRS that I haven't seen on a CRS before. Before purchasing them I would want to know why those bolts are there. Look at the back of the photo of my CRS+ below and you will see what I mean.

westmassguy

TennMan wrote: »

I see two extra bolts sticking out the back of those CRS that I haven't seen on a CRS before. Before purchasing them I would want to know why those bolts are there. Look at the back of the photo of my CRS+ below and you will see what I mean.

Good eye's Ronnie. There's definitely something amiss. The IC socket on the 87'-89' CRS+ should be located in the binding post cup. The hole next to the binding post would have had the 86' blade/blade socket, or a plug for later models. They appear to be the later models, but those bolts coming out the back are not original, and should be investigated. Obviously, someone has been mucking around inside.

Mystery

mikemokr wrote: »

Thanks very much WMG for the info and generous offer of help.
Any way to tell from this?
http://images.craigslist.org/01515_3v3ZKHiHizI_600x450.jpg

Looks like a pin/blade as the IC cable is pretty thin but that's just a guess.
Blade/blade has thicker cable.

TennMan wrote: »

I see two extra bolts sticking out the back of those CRS that I haven't seen on a CRS before. Before purchasing them I would want to know why those bolts are there. Look at the back of the photo of my CRS+ below and you will see what I mean.

My guess is they were used to hang them.
If something internal, then I'd definitely inquire about them.

mikemokr

Real good catch - thanks TennMan.

FYI the left channel speaker has three bolts (though it looks like no nut on the bottom one):

http://images.craigslist.org/00E0E_dNLP8RcE2F7_600x450.jpg

Per my earlier link the right channel has two bolts and an apparent hole where a third may have been.

If the bolts only were used for hanging, would that be a fatal flaw? If the seller isn't the original owner and doesn't know why they're there, steer clear or ??? What about the hole with no bolt in one and what may be a hole partially not covered because of the absence of a nut in the other - how might those affect the sonics?

I realize the stands and IC have value but from what I gather that might be around half the asking price, which is $300. The listing says the speakers sound "beautiful" and are available for demo before purchase. The seller is maybe 25 miles from here so that certainly would be feasible. These have been listed for at least a month, which does make me wonder ... but price has not come down in that time.

Mystery

I'd pass at $300 and wait until the price drops down unless you are in a hurry.

The nuts/bolts may be to hold the PR if the baffle was damaged but can't tell.
If all drivers/PR are original, nuts/bolts can be removed.

westmassguy

Those bolts would have to be removed, holes filled, and possibly recovering the back with new textured vinyl. God knows what they're there for, possibly an articulated arm from the wall? As Mystery said, if they're there to re-enforce the front baffle, those cabs have big problems. I'd venture the crossovers were monkeyed around with too.
I'd pass, unless he lets you take a look inside.

TennMan

The bottom hole in your second photo is normal although it might have been drilled out larger for the bolt. My CRS+ has that hole but it is plugged from the factory. If you look at the photo I posted earlier you can see the cover that is over the hole. That hole is where older model CRS had the IC cable connector installed. The IC cable connector was moved to the terminal cup in latter models.

mikemokr

Yep, see that plugged hole in your CRS+ and understand now what you and WMG are saying re former location for the IC connector.

No hurry. And the problem with me taking a look inside is, honestly, I'm not sure what I'd be looking for, especially if something more subtle than baffle reinforcement.

Very helpful - thanks again everyone.

mikemokr

Might as well link to the photo of the fronts while I'm at it.

http://images.craigslist.org/00v0v_j0UvpZMOVY_50x50c.jpg

Judging by my Monitor 7s and photos I've seen of the CRS+ including in Polk literature, I cannot detect any mods from this view. I may well be missing something though ...

TennMan

mikemokr wrote: »

Might as well link to the photo of the fronts while I'm at it.

http://images.craigslist.org/00v0v_j0UvpZMOVY_50x50c.jpg

Judging by my Monitor 7s and photos I've seen of the CRS+ including in Polk literature, I cannot detect any mods from this view. I may well be missing something though ...

I can't detect any mods from that view either. The photo is about the size of a postage stamp.

mikemokr

heh, don't know how that happened ... trying again

http://images.craigslist.org/00v0v_j0UvpZMOVY_600x450.jpg

westmassguy

Front's look nice, but the other issues need further investigation

mikemokr

yep, I have an email out to the seller

F1nut

Those bolts were installed for a mounting bracket, no biggie and no need to remove them, just make sure they are sealed well. If there was any damage to the front or rear it would show on the exterior.

$300.00 is a steal, buy'em.

mikemokr

F1nut wrote: »

Return the other purchases and get the CRS+.

Even my wife laughed at that ...

I have had an initial conversation with the seller but for a couple reasons including that he was on a cell while driving, it was difficult for me to understand some things e.g. the explanation for the bolts.

He did say the speakers were his son's and, interestingly, that his son replaced the tweeters with tweeters he'd ordered directly from Polk. Now the stock tweeter for the CRS+ was the SL2000 (per the Polk manual) and the replacement is the RDO-194-1, of which I found this photo in another thread here:

http://www.polkaudio.com/forums/attachment.php?attachmentid=43222&d=1253119265

However, that dome is black while in the seller's photo they are silver (and as far as I can tell they look like the SL2000s in my Monitor 7s):

http://images.craigslist.org/00v0v_j0UvpZMOVY_600x450.jpg

On the one hand, if the speakers were owned by someone who cared enough to upgrade the tweeters, I'd see that as a positive. OTOH, if the seller says they were upgraded and in fact they were not ... danger Will Robinson. Are there any other possible tweeter upgrades that would have resulted in silver domes? I have searched but not been able to locate a photo of the RDO-198-1 in case the crossovers were modded too. I suppose one other possibility would have been a repair very early on that simply subbed new SL2000s for old.

I'll probably check the speakers out tomorrow or Saturday.

F1nut

The tweeters in your linked photo are SL2000's. Perhaps an older photo?

Are there any other possible tweeter upgrades that would have resulted in silver domes?

No.

I have searched but not been able to locate a photo of the RDO-198-1 in case the crossovers were modded too.

The RD0194-1 and the RD0198-1 look the same. The only way to tell the difference is the terminals on the back.

mikemokr

F1nut wrote: »

The tweeters in your linked photo are SL2000's. Perhaps an older photo?

That occurred to me. Then again, if the photos with the listing aren't current, who knows what else might be different about the speakers. I guess I'll find out in the next day or two.

leftwinger57

Could those bolts be for a hook and eye hanging system of some kind? Are both speakers holed the same? Why on the vertical unless it was in a club house of some kind? One other thing comparing pictures besides that top centered hole on the frame is that another small hole down in the script on the left which I did not see in Tennman's pic? Lots of questions right.

mikemokr

Hmm, now that I look yet again I see two and possibly three small holes in and near the script on the R channel and two on the L. Curiouser and curiouser.

Now another n00b question (I am done battling with the forum search engine for today) - what would be involved in opening up the speaker to see the insides? Unscrewing/removing the terminal cup and (carefully, so as not to lose the fluid) PR? Anything else? And speaking of the PR, how would I know if fluid wasn't lost during the installation of these bolts and what not?

Currently/belatedly studying the SDA buyer's guide in the handbook on VR3's site. Great stuff, as I'm sure the regulars here are well aware.
http://vr3mods.com/uploads/SDA_Handbook_2011_Rev3.pdf

F1nut

The only fluid inside any SDA speaker is air.

The best way to get an inside view is the remove one or both of the mid-drivers. You'll need a Philips head screwdriver.

mikemokr

F1nut wrote: »

The only fluid inside any SDA speaker is air.

OK, that sound you hear are apparent jokes I'd read in another thread whooshing way over my head ...

The best way to get an inside view is the remove one or both of the mid-drivers. You'll need a Philips head screwdriver.

Great, thanks. Maybe I'll experiment with this operation on my Monitor 7s.