Monitor IIa, ohm rating??

I just picked up today, a pair of these for $25 and am testing them out. They look pretty good and will be fine for the living room. One has a Pyle woofer and the other is a Rockford Fosgate Punch...and it seems like the Walsh tweeters on top aren't working, at least I can't hear anything coming out of them when I put my ear over them. One of the large mids is not working too...so some investigating is in order.

Are they 4 or 8 ohm?

My previous speakers were SM150's, and am trying to climb up the Infinity ladder and own some that are better.

What will be the hardest part to find if all these things are actually bad?

Thanks for reading this.

Pretty much everything you need is currently available on ebay if you are willing to spend the money which is substantially more than your initial investment and the IIa's really aren't much without all of the original drivers. With them however they are an amazing and until fairly recently unappreciated speaker. I bought mine in 1976.

ibanez59er said:

http://www.infinity-classics.de/technik/manuals/Monitor_IIA_technical_sheet.pdf

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Thanks for that page.
I pulled out the tweeters on top to ohm them and they showed open. But the terminals where the leads plug into don't seem to be going anywhere. I've attached a pic to show the top. Both tweeters are the same.

sansuigold99 said:

Thanks for that page.
I pulled out the tweeters on top to ohm them and they showed open. But the terminals where the leads plug into don't seem to be going anywhere. I've attached a pic to show the top. Both tweeters are the same.

Click to expand...

If you look under the driver at the base of the terminals you will (should) see a very thin wire going from the terminal under the magnet. What usually happens to these is that one of the the leads which is actually the end of the voice coil winding opens between the terminal and the voice coil or sometimes in a winding in the voice coil. They can be repaired and there are some AK members who have done it but I am not one of them as it takes a considerable amount of dexterity and good vision, neither of which I am blessed with at my rather advanced age. The only other option is to buy replacements which can be expensive. There is currently an ebay vendor who is selling rebuilt and what he calls "new" Walsh tweeters that incorporate some new design innovations of his. Even his rebuilts have new foil cones as the originals are easily and often damaged. I have no affiliation or experience with this vendor and so cannot speak to the veracity of his products. I have three pair of speakers that incorporate the Walsh tweeter and have been fortunate enough over the years to have accumulated enough spares to meet most contingencies.

i recently restored a pair of monitor IIa's. in my opinion, they are worth the effort and the expense to bring them back. during the process of my resto, we discovered anomalies in the factory schematic. the corrections are posted in this thread:

http://www.audiokarma.org/forums/showthread.php?t=520042

as coastsider said, there are many suitable drivers available on ebay right now. you are in luck in this respect, as it is unusual to see this many of the fairly rare drivers on the market at one time.

be aware though, many of the woofers being auctioned claiming to be for the monitor IIa, are actually not. the correct original factory woofers are "double-doped." that is, they have a thick tar-like doping over the voice coil to add mass to the cone, as well as a light doping on the rest of the cone which adds stiffness. there are also a pair of 902-1187 woofers on ebay right now. these are the infinity recommended replacement woofers for the monitor IIa. in any case, you do want a matched pair of woofers. also, be aware that though the monitor IIa are rated as 8 ohm speakers, the woofers themselves should read about 4 ohms on a meter.

my IIa's were missing woofers when i got them. in my restoration, i first installed some woofers from early production quantum jr.'s as stand-ins until i could source original style double-doped woofers. i was subsequently able to source double-doped woofers from a pair of 1001a's. my personal finding is the Qjr. woofers sounded significantly better in my IIa's. i know that goes against common wisdom, but it is my experience.

it could be the double-doped 1001a woofers are different somehow from the double-doped monitor IIa woofers, or it could be the technology had improved by the time the Qjr. were in production. common wisdom suggests all the double-doped 12" woofers were interchangeable, but i have to question that assumption at this point.

my paper-coned Qjr. woofers are also doped, but with a different stiffening agent. infinity also went to an oversized dust cap to add the mass over the voice coil, instead of the "tar" (which was full of asbestos). later production woofers went to a poly-cone which was an inherently stiffer material and didn't need doping to add stiffness. it is these that infinity recommended as replacements for the doped woofers.

as for the braun midrange (it was a braun midrange, not a peerless as many suggest), there are several on ebay right now. they were also used on infinity's quantum series. these can also be repaired, and there are several threads on AK detailing the process. again, the repair process requires good eyesight, manual dexterity, and patience.

as coastsider mentioned, the walsh tweeters can be repaired (details in the big "walsh tweeter design/rebuild" thread). in your case, with open voice coils, and damaged cones its probably better to replace. there are refurbished originals with new cones on ebay. they look good, but as a product, they are something new and don't have a track record yet. the same vendor has "new" walsh tweeters with titanium drivers, which have met with approval from at least one AK'er.



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loquatious said:

as coastsider said, there are many suitable drivers available on ebay right now. you are in luck in this respect, as it is unusual to see this many of the fairly rare drivers on the market at one time.

be aware though, many of the woofers being auctioned claiming to be for the monitor IIa, are actually not. the correct original factory woofers are "double-doped." that is, they have a thick tar-like doping over the voice coil to add mass to the cone, as well as a light doping on the rest of the cone which adds stiffness. there are also a pair of 902-1187 woofers on ebay right now. these are the infinity recommended replacement woofers for the monitor IIa. in any case, you do want a matched pair of woofers. also, be aware that though the monitor IIa are rated as 8 ohm speakers, the woofers themselves should read about 4 ohms on a meter.

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That pair of woofers that are currently listed on ebay as Monitor IIa woofers with doping on only the inner portion of the cone are actually woofers that were installed on some very early examples of the 3-way Monitor's that Infinity produced and so are misidentified in that respect, and as loquatious suggests, would not make suitable replacement woofers for a pair of Monitor IIa's.

Infinity also used another woofer in some of the early Monitor Jr's that was originally used in the 2000A electrostatic speaker. Here's a photo of one of a pair that I got with some Monitor Jr's some years back.



Even among the numbers of spares of the double doped 12" woofers that I have there are minor differences in the spot on the cone where the doping goes from heavy to light so there apparently was lots of trial and error and mixing and matching going on with Infinity back in the early days

I couldn't stand to look at those two mismatched woofers any longer...so I picked up those poly replacement woofers. Seems like those early doped woofers gave up the ghost early in their life(?), so went with the "factory replacements". There goes my repair money, will have to wait for a miracle to be able to get those nice Walsh tweeters.
It does my heart good to hear you, Loquatious (will have to look that one up), say they're worth it in the end to restore back to original equipment. You don't want to know what was rolling around in my head trying to figure out a way around those expensive Walsh things!

i think you will find the 902-1187 woofers will sound fine. they are the recommended replacements, after all, and the price you paid was fair. i thought about grabbing those myself. don't let pricing of replacement drivers scare you off. at the price you are into the project, you are still doing well. market value of 70s infinitys seems to be climbing (and so are the prices of spares). the monitor IIa's are some of the most desirable of the walsh equipped models. for reference, there are a pair for sale on craigslist in LA that have the same replacement 902-1187 woofers in them, current asking price (as of this post) $900.




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Well, I'm starting at the bottom here with 5 drivers needing the boot. Can you really hear those Walsh super tweeters? I will be doing these right. I haven't seen the crossovers yet. I bought them from the original owner, who didn't do anything with them.

I do believe you stated you removed(utterly and completely) the Walsh tweeters from the cabinets and applied an audio signal but heard nary a sound?
They are crossed over in the cabinet rather high and produce an airy ambiance rather than crashing cymbals.

i've commented on this before, but it bears repeating.

the walsh are super tweeters, acting only above 10,000hz. walshes are very subtle. they color the sound, rather than beat you over the head with it. they add a "sparkle" and "spaciousness" to augment the dome tweeter. its hard to describe, but you are "aware" of what they are doing more than you "hear" it. many people simply can't hear the highest frequencies and assume their walshes are not working, when in fact, they are functioning as intended. in practice, its better to check the functionality of a walsh with a multimeter, than an ear. however, you can feel a working walsh vibrate by lightly touching the cone while its playing.

none of the caps in my IIa's were electrolytic, so they didn't need replacing due to age. i did replace them due to the sloppy 20% tolerance of the original caps. i went with dayton 1% audio grade caps, figuring the closer i got to the spec, the better. working on the crossover in place requires the flexibility of a contortionist, but can be done.

your cabinets look to be in good nick. did you get the fabric tops as well as the wood ones?



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tubed said:

I do believe you stated you removed(utterly and completely) the Walsh tweeters from the cabinets and applied an audio signal but heard nary a sound?
They are crossed over in the cabinet rather high and produce an airy ambiance rather than crashing cymbals.

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I put my cheap digital ohm meter on them and, using all the ranges, they showed open, no continuity. And with my ear right up to them, couldn't hear anything. Should I try wiring direct to speaker wire and give a listen, or will that harm them?

loquatious said:

i've commented on this before, but it bears repeating.

the walsh are super tweeters, acting only above 10,000hz. walshes are very subtle. they color the sound, rather than beat you over the head with it. they add a "sparkle" and "spaciousness" to augment the dome tweeter. its hard to describe, but you are "aware" of what they are doing more than you "hear" it. many people simply can't hear the highest frequencies and assume their walshes are not working, when in fact, they are functioning as intended. in practice, its better to check the functionality of a walsh with a multimeter, than an ear. however, you can feel a working walsh vibrate by lightly touching the cone while its playing.

none of the caps in my IIa's were electrolytic, so they didn't need replacing due to age. i did replace them due to the sloppy 20% tolerance of the original caps. i went with dayton 1% audio grade caps, figuring the closer i got to the spec, the better. working on the crossover in place requires the flexibility of a contortionist, but can be done.

your cabinets look to be in good nick. did you get the fabric tops as well as the wood ones?



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No I didn't. I can call and ask if he still has them. I don't know much about these...did the fabric go in place of the wood tops?

sansuigold99 said:

I put my cheap digital ohm meter on them and, using all the ranges, they showed open, no continuity. And with my ear right up to them, couldn't hear anything. Should I try wiring direct to speaker wire and give a listen, or will that harm them?

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If they are already faulty you couldn't hurt them by putting audio through them.
Turn the bass and midrange down and apply a signal, if they are good you will hear sound.
Carefully
Good Luck.

sansuigold99 said:

...did the fabric go in place of the wood tops?

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The Monitor IIa's when purchased new were delivered with both wood and fabric tops.

The four page color brochure states "When we created the Monitor IIa we frankly couldn't come to agreement on one styling point. Some of us preferred the black cloth top which continued the look and aesthetic flow of the removable front grill and provided perfect acoustic transparency for the Walsh tweeters. Others preferred the oiled walnut top which, while having a slight effect on the dispersion of the Walsh, gave the Monitor IIa an additional artistic practicality as a pedestal for a favorite piece of statuary or art object.

So we decided in favor of both. Every Monitor IIa comes with both a black cloth top and a hand rubbed oiled walnut top, for you to use or not use at your pleasure. These tops easily, quickly and ingeniously snap into position. Infinity is the only company in the audio field to offer you this aesthetic flexibility - in addition, of course, to magnificent sound."

You've got to love those silver-tongued ad agency copy writers.

In most cases when IIa's are purchased now the cloth tops are long gone.

I've always used the "hand rubbed oiled walnut tops" on my IIa's but have had the cloth tops well protected and stored away for 37 years. Maybe I should get them out to see if they actually do provide "perfect acoustic transparency for the Walsh tweeters". It's worth a shot.

yes, those infinity copywriters do wax poetic. i have tried both tops, and have to give a very slight edge to the fabric ones for letting the walshes "breathe" a bit more. however, my wood ones are the ones in regular service, simply because i think they look better and are easier to dust.


to the op: even a cheap multimeter should show a reading if you do have continuity. i'd guess you do have continuity issues, which seems to be a pretty common problem with walsh tweeters. so common, that i waited until we (the AK'ers on the infinity forum) had figured out they could be repaired (the big wash tweeter thread), before i bit the bullet and bought some walsh-equipped infintys.

i'm the 3rd owner of my IIa's. i'm in california, and my IIa's came from georgia, so i never got to see them in person or hear them prior to purchase. they were a crapshoot. the guy i bought them from had bought them as a project (with no woofers in them), but got scared off by the rarity of the original woofers. he never played them, and wouldn't pull the walshes to check them on a meter for me.

luckily, both previous owners had kept both tops, and the original boxes, which indicated to me they probably did take care of the speakers (even though the 1st owner tossed the original woofers when the foam went). in fact, i never would have bought them if the original boxes weren't available to ship them in, as there is a better than 50/50 chance walshes don't survive shipping. somehow i got lucky, and both of my walshes survived the trip west, had continuity, and decent cones (that said, i paid a lot more for my IIa's than $25. – and the shipping from georgia cost as much as the speakers).

in your case, it looks like the previous owner didn't give the walshes the respect they need. now, even if you restore continuity by unwinding a coil and re-soldering, your walsh cones are so damaged that you still have to replace the cones (thankfully you can now do that, six months ago replacing cones was not even an option). also, the impact that crushed your cone may have damaged the spider, which could add another issue. given just new cones will cost $150, it would be most cost effective to just source replacement walshes.

i know you just dropped some coin on the woofers, and you still need walshes and maybe a mid (did you ever check the mid on the meter?). recapping is also an option, and will add yet more expense. i know it is adding up, and might seem daunting. but i think, if you are patient, you can do all that and still be into the speakers for less than current market value. by the time you're done you'll have some nice vintage infinitys to enjoy (or, if you decide you don't like them, you're not into them for more than they're worth).




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sansuigold99 said:

No I didn't. I can call and ask if he still has them. I don't know much about these...did the fabric go in place of the wood tops?

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That was good timing...the seller just emailed me saying he found the fabric tops for them and they're in good shape, so I'm picking them up tomorrow!

Hooking the Walshes up directly netted no sound either. I'm just hoping I can hear those things when hooked up in concert with all the other drivers...but like you said Lo-q, they will be more sensed than heard. When I read your description to my better half, her eyes kinda rolled...hopefully she's a believer in the end! I'll have to put on her Engelbert Humperdink and see if she thinks he's really in the room with her.

I pulled out the mid that didn't work and ohmed it; it was open like the tweets. One of the wires on the front has cracked shell material but seems like the wire is there. Is there anything else I can check?

there is a lot of info here on AK about both the walsh and the mid. tons of info about repairing these drivers in these threads:

http://www.audiokarma.org/forums/showthread.php?p=7037947

http://www.audiokarma.org/forums/showthread.php?t=457391


your walshes clearly have open circuits. your other walsh doesn't look bad. with a new foam cap, it would look new (see post 113 of the above). what's up with the gray blob at the base of each cone? like plumber's putty. thats not factory, and something i've never seen. i'd ask the original owner about why he did that. looks like he was trying to dampen the cones somehow. but, to address what?


i have several sets of vintage infinitys. some stuff from the mid 70s, some from the early 90s.

is the monitor IIa the best infinity i own? no.

i really like the IIa's, but i'll be honest, my stuff with the emit tweeters walks all over my early stuff. if you are expecting emit performance from a walsh, it simply ain't gonna happen. the emit is just better technology. however, the walsh was cutting edge tech in it's day, as was the doped woofer. the outsourced drivers were top notch as well. i can say the IIa's do everything well, and sound good (and look good) doing it.

tell your better half i've never listened to engelbert humperdink on my monitor IIa's (or, admittedly, on anything else), so i can't comment directly on using him as a yardstick, but i do listen a lot, and to a lot of different stuff, and think she should be pleased with the upgrade from your SM's. and don't hesitate to point out the monitor IIa's are going up in value, whereas the SM's are going down, so the IIa's are a better investment.



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If the Emit is a more advanced tweeter and better performing, (here comes my dark thought) I should replace the Walsh with it...if I didn't care about originality. Have we seen that done? Of course I wouldn't hack up the cab so as to not be able to put a Walsh in when I could afford it.

Yeah, Engelbert isn't the most acoustically thrilling music, but his voice my wife would like.

I am thrilled to have so much information to take in that is so pertinent to my project. I am staying up too late reading all this stuff.

I picked up those fabric tops and they are nice, as I imagine most are since they were probably put away.