An in-depth Infinity Monitor rebuild (IA?)

[13stoploss]

Infinity Monitor (IA???) rebuild thread. Serial #XXXXXXX and XXXXXXX. (will add later)

I found these speakers on my local Marketplace in 2023. Negotiations fell a part, but not in a bad way. Just didn't work out. My interest stems from a pair that I had found while living in the DMV (D.C./Maryland/Virginia) in the twentyteens (lol) for $500, but they sold before I could get them. Earlier this year, in Sac, a local friend asked me if I'd ever heard them. He wasn't too pleased with the sound of the ones he picked up, and it turned out to be that same pair I had almost bought. Though my friend wasn't the one who bought them from the guy I talked to, my friend admitted to paying $50 for them, and basically handed them to me to see what I thought.



Despite a minimal cosmetic refresh job, the speakers were in rough shape. The cabinet materials didn't hold up to time and aren't well built, and the front baffles were in serious disrepair. The doped 12" woofers—I suspect from the Monitor IIA?—played deep and boomy in the cabinet. The mid-tweets were overly bright and dominant, and the famed Walsh super tweeters—mis-matched in the photos, a taller gold and a shorter silver—added little more than static to the mix. The crossovers were a jumbled mess of mismatched wire colors and at least one exploded-but-replaced resistor.

Still, I thought they were worth rebuilding.

 

[13stoploss]

I'm the ESS guy who rebuilt the Transars and the "another ESS AMT Pyramid rebuild." Full disclosure: I once ran ESS social media, before I wrote for SoundStage! and Stereophile.

Like with all speaker rebuilds, the first step is to listen. As I mentioned in the post above, the Monitors had some serious physical and functional deficiencies. At first listen, they were boomy and boxy sounding. Deep and bloated. Over 10-14 days, they began to mellow, such that the boominess subsided a bit and the mid-range tweeters began to dominate the musical space. The "Walsh" tweeters added nothing.



First up? Dismantle.

In this photo (below), you can see glue in the driver beds. Not as easily seen is that the 12" woofers have been out many times and re-drilled into the mounting bed several times. That's gonna need some fixing. Not a fan of particle board motor boards/front baffles. It might be dense (and cheap), but for these, it's weak and literally flaking away. Few other tidbits: One cabinet has two small veneer tears; the black mesh cages aren't my thing, and worse still is that they're fastened by staples which have rattled loose over the years and vibrate at some frequencies; I mentioned not being impressed with the cabinetry: there are panel gaps and inexact spacings; lastly, the velcro strips... overall, this is a pretty chintzy presentation for a supposed premier speaker system...

Up top (below) is one of the worst offenses: the Walsh tweeters were secured by glue! What a mess.

Dickin' around, man. Just couldn't get it loose, so I busted out the old Army heat gun (thanks, Drill Sergeant!). I attempted to heat up the glue, and it began working, but I didn't have a third or fourth or fifth hand and eventually began scorching the aluminum cone, even as I tried shielding it from the heat with several index cards.

Fnck.

 

[13stoploss]

Since there was very little info on AK for Infinity Monitor that wasn't "IIA," I joined the "Vintage Infinity Speakers" Facebook group to gather more information, including a recent history of these exact speakers in my area. Nothing salacious, just good tracking info from previous owners.

Ultimately, I decided to repair and replace/trade my mis-matched (one silver, one gold, both different mounting plates) Walsh tweeters with Dr. Mike, that guy on eBay, familiar to Infinity users. He's... an interesting guy... but he was accommodating and more than fair, and I appreciated his effort and time. All I can say is that USPS "insurance" is a scam. You will not win when they damage your goods. Ask me how I know...

Well, I can't upload any photos, but it looks like a screenshot of an image worked! Below are the new Walsh tweeter cones affixed to new and matching drivers on matching mounts, something mine didn't originally come with.



Another screenshot of an image that I had to reduce the pixel size of twice... Once I removed the tweeters from the top of the damaged cabinet, I decided that the cabinet mounting points were going to need some fortification. In fact, this was true of literally every driver mounting point.

I stuffed toothpicks into every hole and broke them off flush. Then I clipped the pokey shards flat and filled with wood glue. After a light sand, I first used an oil-based wood filler to fill the flaking particle board at the mounting surface with the intention of sanding flat. This filler doesn't dry hard. Oops.



I also used some of that oil-based wood filler on the front baffles to seal in the flaking motorboards. In hindsight, I used it too sparingly. This was a fantastic idea, one that I came back to later. Unseen is that I literally removed like 2,900 staples holding on the velco strips that hold the black grilles.



Still rolling with what seems to be working, more screenshots of iphone images edited in Photoshop!

Here's the other cabinet. After cleaning it up, you can better see the damage to the mounting surface and how I'm filling and lightly sanding to flatten.



If you look closely in the below, you can see some of the toothpick-filled holes glued over and sanded. I also hand-rubbed wood glue over the entire mounting surface to kinda harden the flaking surface. That worked very well, too.



Below: I delicately managed placing the tweeters into their mounting holes to see where I needed to continue building up, sanding, and trimming (utility blade). Here, you can see that the Walsh tweeter still sits above the mounting hole. If you look closely at the filler, you can see old black spray paint atop the soft and non-dried oil-based filler. This was my first hint that that stuff wasn't going to cut it.



Moving on to the good stuff, man. This is what I should've used from the start: Kwikwood epoxy wood filler. The trick to using this stuff is keeping your fingers wet. Knead the dough, make it soft and pliable and smearable, then spread it all over, pressing it flat and into the spaces. Build it up, don't worry about the rise and bulbous ridges—those will be sanded.



Getting there! You can see the driver sitting mostly inside the mounting hole, but ugly and not flush or smooth.



This part (below) took a lot of time, and I only worked on weekends. Patience. I built up the filler, sanded, built up, sanded, repeat. Over and over until the drivers in both cabinets fell into place and also sat in their seats smoothly.



This, the below, is my "perfect is the enemy of good" shot. The interior mounting circumference, the part outside and nearest the plastic mounting ring, isn't perfectly round, but my eyes move toward the finish, the part that transitions from the particle board to the Quikwood. That's smooth. Very, very happy with how that turned out. At this point, I felt ready for paint.

Also, note: Look at the front surface of the motorboard, beneath the black painted portion of the top. You can see how the particle board is literally flaking away. Literally. To the touch. <shrug>

 

[13stoploss]

I'm a firm believer in careful cabinet repair. But what you can do today isn't the same as what was available 10 years ago. Also, I've found that some products I had on the east coast years ago aren't available now in CA. Not a huge issue, just mentioning.

On cabinet repair, if the veneer is in tact, and if the speaker's skin is old enough, then the repair is simple: Scrape and sand. No stain remover necessary.

Scrape, don't sand. Scrape, then sand.

If your finish is old and dried, scrape it. Sanding will go through the old, cracked finish and remove the thin wood veneer underneath it. Scraping the top finish gives you the opportunity to repair the original veneer, leading to a more simple stain and finish on the original veneer.

[MORE]

I began restoring the front baffle's driver mounting beds. I removed the glue and sticky stuff, and then stuck a toothpick into each hole and then broke them off flush, then filled each nook and cranny with wood glue (below).

On the mids (below), I applied a more liberal amount of wood glue over the whole hole. On this specific photo, I couldn't see the original mounting points. On the upper, outer edge, you can see that I also used an oil-based wood filler to fill in the flaking motor board. It didn't work well. Nothing will stop these pieces of shlt from splintering away.

 

[13stoploss]

IV of V (?)

 

[13stoploss]

Reserving a Vth.

 

[pauldrewry]

 

[13stoploss]

Anyway, these speakers are done and I wanted to share the photos and a writeup, but apparently you can't upload .heic, .png, or .jpg photos. So...

Edit: My workaround is taking screenshots of the images. When those don't upload, I edit in Photoshop and reduce image down to 700-750px on the longside at 144ppi.

Stupid, but this seems to work.

 

[krautmaster]

Anyway, these speakers are done and I wanted to share the photos and a writeup, but apparently you can't upload .heic, .png, or .jpg photos. So...

Convert them to a JPEG and limit size to 1200x900, should upload fine... I'd like to see the finished project.

 

[13stoploss]

Convert them to a JPEG and limit size to 1200x900, should upload fine... I'd like to see the finished project.

I'm not even able to use 900px on the long side at 144ppi. I'm barely getting by at 700-750px at 144 ppi.

 

[Torin Krell]

These are similar Infinity IIa speakers I came across a while ago. It has what looks like the addition of a peerless tweeter.

 

[13stoploss]

Still working on posting how I got to here, but here's the current done'ish. Just need to put all the staples and velco back, and then tidy up the pedestals.

 

[krautmaster]

Still working on posting how I got to here, but here's the current done'ish. Just need to put all the staples and velco back, and then tidy up the pedestals.

View attachment 3575090


View attachment 3575091

Looking good (Excellent actually) !

 

[hpm40]

Beautiful wood after removing the old finish. Excellent work. They look amazing. How do they sound ?

 

[13stoploss]

Beautiful wood after removing the old finish. Excellent work. They look amazing. How do they sound ?

Not good, and I finally figured out why. More to come.

 

[Maxamillion]

Why not post this on the dedicated AK Infinity Forum a little further down the home screen? It would be a valuable addition to the Infinity knowledge bank being collected there.
Nice work, by the way.