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Bookshelf Infinity SM input?

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Doc Rock

Active Member
Ran across a pair of Infinity SM (I think maybe 85, can't remember, but it was2 numbers with one being an 8) recently and have been thinking about going back for them. They're nice and solid to the "knuckle test". They have the polycell tweeters and what appear to be the original woofers, but the woofers have a few holes in the foam surrounds. The grillcloth had a little wear. The price was pretty nice. I think the woofers are 8" (might be 6"). I have some 8" fullrange drivers that need a home, so I could play with that while I get the originals refoamed. Any input on these? I know next to nothing about Infinity speakers, but have read that these were the "entry level" line.
 
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Can anyone give me some info on the polycell tweeters also - how well do they perform and what type construction are they? Thanks.
 
take a look at the INFINITY page:

http://www.infinitysystems.com/home/products/product_detail.aspx?prod=IF40014W&CheckProduct=Y&Language=ENG&Country=US&Region=USA

As you have read, that "SM" series is not very appreciated by infinity fans, as they was "entry level" speakers, but the "not good" SM122 that I've heard, sounded very good to me in those years...

If you are going to compare an Infinity speaker against any other, you should get any vintage infinity featuring EMIT tweeters.

regards.
 
Well, I took the plunge. They are the SM-85s. I'm a bit disappointed because as I stated earlier I was hoping to use these to drop some other speakers into to try them out, unfortunately they are larger and won't quite fit into the holes (although they're also 8" speakers). One side seemed like the tweeter might be out initally, but now seems to be working. I checked the resistances on that speaker and the woofer measured 4.7 ohm and the tweeter was 22, so I'm assuming the tweeter is some sort of piezo design. This is a ported cab, with no internal stuffing and no bracing. Its made of fairly thick pressboard (or grainy MDF, I'm not sure). Since the cab is only about 1 cu/ft volume, the lack of bracing is probably not a huge issue. There is a small crossover board at the back I haven't looked over yet, but it is too small to have much in the way of "high end" components. They have the ubiquitous plastic spring terminals at the back. There are a few small holes and tears in the foam, but it would probably make more sense to try to repair whats there rather than refoam, since its mostly intact, and these are cheapies. The speakers have reasonably hefty magnets.

How do they sound? They're pretty bright. There is a bit of hollowness to the sound, probably related to the lack of any stuffing. There is of course no low bass, and the upper bass is kinda light and undefined. Still, for $60 a pair I can't complain much.

Now to decide whether to reversibly mod them, do the "full monty" and cut a larger hole for my other speakers, or move them on to the next owner.
 
It seems you know a bit about speakers ... Give them a try, without expendig extra money.... Seal those small holes, take the crossover, look if there is any electrolytic cap that should be replaced, clean every contact (You noted a intermittent tweeter...)

Check also that the drivers are properly connected (I mean "polarity") (I have a pair that was INCORRECTLY wired by a tech that didn't know that some drivers should be polarity reversed, and he wired everything in phase, where some drivers should be reversed)

You can post a schematic of the crossover you have.

REGARDING THE BASS.... well, the specs says "42Hz".... Same that my infinity Qb (10" Q woofer)... THAT SHOULD GIVE YOU A QUITE DEEP BASS for an 8" ....
 
I'm sure if I can repair or refoam the woofers I'll gain a bit of bass, just not optimistic it'll be a huge amount as they're largely intact. I'll probably end up buying a refoam kit before too long, in the meantime I'll probably end up just gluing the tears for now.
 
Did my best to repair the current surrounds with some glue, and added some Acoustistuff fill (just about 1/4 of the total volume, placed behind the woofers). I think they sound somewhat better, but still very hot treble. I'll probably order a surround repair kit soon and try that. I'm thinking of adding something to the crossover to pad the tweeters slightly - anyone have a crossover schematic? I decided not to add bracing, as these have fairly thick walls and aren't big enough to have much flex as is. I pulled out a crossover and glanced at it - it seems to have reasonable component quality for such a small crossover board. Once I get a schematic I'll probably upgrade the smaller caps as well.

These would sound pretty good in a smallish room near the corners with a dark sounding tube amp. If you have a cheap solid state amp steer clear unless you need to compensate for some high frequency hearing loss or have some EQ available.
 
That is pretty much my take on my SM-82's. Way to hot on the top end, and I could never get the bass output that I was expecting out of them. My other pair of cheapies with 8" drivers, Advent Prodigy II's, put them to shame in that area.
 
I have owned a pair of SM-122s since new, and still like them. Liked them enough to repair the woofer foam when they crumbled versus buying a replacement (nothing I came across seemed to work as well for large sound / big room music and HT. Don't know much about the smaller SM though.

Most if not all of the SMs by now have crumbling surrounds. When mine went, I discovered the odd size woofer in mine (sounds like you discovered this as well). Standard refoam kits do not fit, so I am guessing that Infinity in those days made the SMs out of metric drivers (perhaps from Asia) to cut costs. Anyway, my foams had to be cut and glued together to fit right. Also, mine were glued to the underside of the cones...good luck doing that again (I paid a speaker repair shop to do this). Also, I discovered the difficulty in finding drop-in replacements for the odd size drivers.

To me the SM woofers are only o-k, but I really like the polycell tweeters. Mine say "High Output" on them, but I have seen some that do not. I do not know the sound difference (if any), but I like mine. To my ears, Cerwin Vegas had better woofers in the day, but I liked the Infinity tweeters in comparison.

Good luck working on yours.
 
Yamahalic said:
To me the SM woofers are only o-k, but I really like the polycell tweeters. Mine say "High Output" on them, but I have seen some that do not. I do not know the sound difference (if any), but I like mine. To my ears, Cerwin Vegas had better woofers in the day, but I liked the Infinity tweeters in comparison.
Click to expand...

Having heard both, the type that says "high output", and the ones that just say "polycell"; I think there is no difference between them. I agree with your ears. I like the bass from the CV's woofers better, but the highs from the polycell is superior to the CV's tweeters. To me, the Polycell sounds very similar to many decent Silk Dome Tweeters, that I have heard.
 
techsui said:
That is pretty much my take on my SM-82's. Way to hot on the top end, and I could never get the bass output that I was expecting out of them. My other pair of cheapies with 8" drivers, Advent Prodigy II's, put them to shame in that area.
Click to expand...

I have these speakers and this post captures my opinion exactly. It's like those tweeters are trying to bore a hole through my head...Ouch! I would love to find a way to tame those tweeters.
 
To tame the tweeters, you need a better woofer. The stock ones may have too low an SPL signal to match the tweeter output. Pollycell tweeters are outstanding when they are balanced against a good woof.

I have found that the first improvement in smaller two way Infinities is to rebuild the crossover. The old electrolytic caps are robbing current from the woofs. Put in modern poly-film caps and they will wake up some. However, I've also had good luck replacing the 8" woofers in the RS3000's with HKM/Westra German made woofers. That is a much better balance :)

Here's the specs:

HKM/Westra (this is the closest match for the 902-2666 and a great woofer). Slightly different voicing due to treated paper cone, in lieu of Infinity Poly-Cone. Specs are:

4 ohms
Power 60 watts RMS (110 watts Peak) 120 Watts RMS in a home serial application (230 watts peak)
1 1/2 inch voice coil
SPL is 90db 1000 Hz. at 1 watt/meter
Fs is 33.6402 Hz
Revc is 3.3844 ohms
Qms = 3.4342
Qes = 0.5628
Qts = 0.4836
Le = 0.4187 mH ( @ 1 kHz.)
Vas = 40 liters
Cms = 0.0200 uM/Newton
Bl = 1193.6470 N/A
Freq. Response 30 Hz. to 3,500 Hz.
Size - 8 1/16 inches ( 205 cm ) dia. - Fits into a 7 inch hole opening - 3 1/4 inch mounting depth

Very close to 902-2666 in sound and efficiency curve. Slightly smaller so need new mounting holes. Good match for the 902-2722 (or other PolyCell) tweeter using the RS-3000 crossover.

I understand that these are no longer available, but ones with similar specs should work nicely. To better match a somewhat hot tweeter, I'd be looking for an SPL of 91 or better.

All Infinity box cabs can really benefit from front to back bracing. A 1x1 stick from the top of the woofer cut-out to the back panel will do nicely. Catch the end of it with the top speaker screw and a black drywall screw in the back and you'll hardly see it.

Better and bigger Infinities are filled with polyester stuffing and a piece of course muslin as a fiber filter behind all drivers. The SM line was built to a real tight price point, so these "add-on" were left out. But they will add performance. Pillow stuffing from the yardage store will do fine and it is cheap.

SM's do have some performance left in them. Just need to search around for the balance. The Pollycell tweets are the best feature, they just need to be balanced.

To read a bit more on how I arrived at this info, read here: http://www.audiokarma.org/forums/showthread.php?t=124136&highlight=sing :)
 
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Quick update - tonight I refoamed the woofers and gave another listen.
WOW! Night and day! They have significantly more bass and some more mids than they had before. Apparently the old foam was both stiffer and more porous to air, hampering their performance. They still have a prominent treble, but the balance is now much better. Overall these are nice little speakers.

If anyone has a set of older speakers with old foam and feel they're missing the bass, I'd highly recommend tracking down a refoam kit and giving it a try.
 
The crossover is on a small board attached to the jack plate, and components are packed on there pretty closely. I think the only mod short of building a new one might be replacing the small cap, but I haven't done that yet. It would be nice to have a schematic available to save the trouble of figuring it out if I wanted to build a better quality one, but I doubt I'll go to that much effort on these. The inductors are iron core, so I'm sure it could sound better with a rebuilt crossover with all improved caps and air core inductors.
 
Doc Rock said:
Well, I took the plunge. They are the SM-85s. I'm a bit disappointed because as I stated earlier I was hoping to use these to drop some other speakers into to try them out, unfortunately they are larger and won't quite fit into the holes (although they're also 8" speakers). One side seemed like the tweeter might be out initally, but now seems to be working. I checked the resistances on that speaker and the woofer measured 4.7 ohm and the tweeter was 22, so I'm assuming the tweeter is some sort of piezo design. This is a ported cab, with no internal stuffing and no bracing. Its made of fairly thick pressboard (or grainy MDF, I'm not sure). Since the cab is only about 1 cu/ft volume, the lack of bracing is probably not a huge issue. There is a small crossover board at the back I haven't looked over yet, but it is too small to have much in the way of "high end" components. They have the ubiquitous plastic spring terminals at the back. There are a few small holes and tears in the foam, but it would probably make more sense to try to repair whats there rather than refoam, since its mostly intact, and these are cheapies. The speakers have reasonably hefty magnets.

How do they sound? They're pretty bright. There is a bit of hollowness to the sound, probably related to the lack of any stuffing. There is of course no low bass, and the upper bass is kinda light and undefined. Still, for $60 a pair I can't complain much.

Now to decide whether to reversibly mod them, do the "full monty" and cut a larger hole for my other speakers, or move them on to the next owner.
Click to expand...

I just picked up a set of SM 85s with new foam sourounds for $100 , matched up with a 1989 Denon DRA 625R reciever from my friends store & ..damn.....I'm impressed....these things kick ass ....loud & clear!
 
Doc Rock said:
Ran across a pair of Infinity SM (I think maybe 85, can't remember, but it was2 numbers with one being an 8) recently and have been thinking about going back for them. They're nice and solid to the "knuckle test". They have the polycell tweeters and what appear to be the original woofers, but the woofers have a few holes in the foam surrounds. The grillcloth had a little wear. The price was pretty nice. I think the woofers are 8" (might be 6"). I have some 8" fullrange drivers that need a home, so I could play with that while I get the originals refoamed. Any input on these? I know next to nothing about Infinity speakers, but have read that these were the "entry level" line.
Click to expand...

Hi....just picked a pair of 85s with new sourounds & tweeters & hooked them up to my 1989 Denon DRA 625 reciever & they sound amazing.....loud & clear for $100
 
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