mcheinstein
Active Member
Hi all, I came into a pair of rough looking Infinity Monitor Ia speakers that I've been fixin' up. I wanted to share some of my results and maybe get some help along the way! I'm definitely not an Infinity guru by any stretch of imagination, but I thought this would be a cool project, and, given the dearth of resources on these rare units, be an informative post at the very least. This is my first speaker restore project, so go easy on me!
Here they are once I dragged them home. I was able to snag them for $100 bucks, but was very hesitant to spend the dough. The guying selling them inherited them from a buddy who unfortunately passed away, who had remembered hearing them in action and working fine, but didn't have an amp to power them and test if they were still working. He did know, however, that the walsh's and the mids were original. The woofers obviously were not original (cheap pyle's put in their place). I brought a cheapo amp, and a multi-meter, with me when I first looked at them. All the drivers, including the Walsh's, were producing sound. The Walsh's looked good (besides the rotted out foam), no dents or scratches. Sound from mids and tweeter were scratchy due to the dirty mid-range and tweeter pots on the cross over. I took a risk, didn't open the cabs to test driver impedances, and loaded them in my car!
Close-up of the left unit. They're cosmetically in rough shape, but at least the mids and Walsh's were fine. Foam grills melted long long ago. I figured if I screw everything up with these, I can always part the Walsh's out and sell on the bay! Speaking of the bay, I was super lucky because I was able to find a pair of the original double doped woofers on the bay first search!
The original woofers are 12" paper cones with tar doping in the center to optimize the stiffness to mass ratio. These puppies were rated to go down sub 30 hz in the cabs and known to produce prodigious bass. Apparently, they can be quite hard to snag (from my research), but I guess I was lucky and had no problem getting them.
The infinity guys took their filling seriously!! These things are stuffed to the brim with the stuff. In this pic, I've removed the pyle woofer and soldered in the original woofer. The woofer wires are also wrapped in polyfill. To get at the cross over, you have to push the polyfill up and out of the way, and you'll see the cross-over at the back of the cab.
After I shoved all the polyfill up into the top of the cab (be careful of the other wires going to the other drivers), I was able to check out the cross overs. There are two pots, one for the mid range and one for the tweeter. I liberally applied de-oxit to both. I decided to indulge myself also and bought some Dayton 1% 25uF 250V precision caps to replace the 40+ year old electrolytics plugged up to the mids (originally rated at 100V). I also disconnected the walshs and tested their impedance at 8.1 ohms.
The rotted foam in the Walsh's also HAD to go. After a lot of research on this site and other forums, I decided to be a cheapo and get some $5 shop-vac filters from home depot rather than shelling out $30 for the good stuff from foam factory. Someone else had compared the two and said they looked pretty similar spec wise and sounded good, so I said why not. Second pic has the new foam in place. Something interesting about the Ia line is that they have metal wire protecting the walsh from the front, sides, and top. It also has the bracket going over it with a pin in the center that goes into the foam and keeps it centered on in the tweeter cone. The more common Monitor IIa Walsh's are less protected and have a center rod to help keep everything centered.
The cabs were pretty rough looking on the outside, but nothing a little restor-a-finish and wax couldn't fix! See the left vs the right... guess which one I already treated. I also carefully spray painted the wire enclosure protecting the Walsh's with black spray paint to spiff them up.
New grills also were in order because the rough looking cosmetics of the front (just hide it all right?). I decided I wanted the Walsh's to appear visible because of their unique look, so I designed a grill that should go up to the Walsh's, and then a square grill to also go on top of the cabinet. Here's the simple frame for the grill I whipped together (not a great woodworker) before I covered them with black grill cloth ordered from parts express.
The final speaker with the front and top grills on. I was able to source some small infinity badges that are in the bottom left hand corner of each grill (hard to see in this pic), but not the original badges unfortunately.
I have them paired with a Marantz 1200 (built at roughly the same time as these), and Jesus does this system kick! The bass is pretty unbelievable. I get a meaningful response on these down to 22 Hz! Tight and punchy too. Imaging is good, real broad sound stage, nice 3d effect too, especially on centered vocals. Detailed, but very easy at the same time. Everything sounds very natural, especially the highs. You can hear the warm resonance of an acoustic guitar, but also still get the fingers slipping on the strings sounding right. My Thiel CS2s are more detailed and have a bit more defined of a sound stage, but these infinities make them feel stiff. It's like the Thiels are transmitting exactly what's at the microphone for an instrument, while the infinities are sitting a foot or two away. The infinities sound shockingly good for their age. I haven't found anything that sounds bad on them per se. I would describe them as all rounders, maybe spiking a bit on the low end and high end coverage/clarity, but all in all a very pleasing and easy speaker to enjoy. Plus, my wife likes them, so they're here to stay!
Here they are once I dragged them home. I was able to snag them for $100 bucks, but was very hesitant to spend the dough. The guying selling them inherited them from a buddy who unfortunately passed away, who had remembered hearing them in action and working fine, but didn't have an amp to power them and test if they were still working. He did know, however, that the walsh's and the mids were original. The woofers obviously were not original (cheap pyle's put in their place). I brought a cheapo amp, and a multi-meter, with me when I first looked at them. All the drivers, including the Walsh's, were producing sound. The Walsh's looked good (besides the rotted out foam), no dents or scratches. Sound from mids and tweeter were scratchy due to the dirty mid-range and tweeter pots on the cross over. I took a risk, didn't open the cabs to test driver impedances, and loaded them in my car!
Close-up of the left unit. They're cosmetically in rough shape, but at least the mids and Walsh's were fine. Foam grills melted long long ago. I figured if I screw everything up with these, I can always part the Walsh's out and sell on the bay! Speaking of the bay, I was super lucky because I was able to find a pair of the original double doped woofers on the bay first search!
The original woofers are 12" paper cones with tar doping in the center to optimize the stiffness to mass ratio. These puppies were rated to go down sub 30 hz in the cabs and known to produce prodigious bass. Apparently, they can be quite hard to snag (from my research), but I guess I was lucky and had no problem getting them.
The infinity guys took their filling seriously!! These things are stuffed to the brim with the stuff. In this pic, I've removed the pyle woofer and soldered in the original woofer. The woofer wires are also wrapped in polyfill. To get at the cross over, you have to push the polyfill up and out of the way, and you'll see the cross-over at the back of the cab.
After I shoved all the polyfill up into the top of the cab (be careful of the other wires going to the other drivers), I was able to check out the cross overs. There are two pots, one for the mid range and one for the tweeter. I liberally applied de-oxit to both. I decided to indulge myself also and bought some Dayton 1% 25uF 250V precision caps to replace the 40+ year old electrolytics plugged up to the mids (originally rated at 100V). I also disconnected the walshs and tested their impedance at 8.1 ohms.
The rotted foam in the Walsh's also HAD to go. After a lot of research on this site and other forums, I decided to be a cheapo and get some $5 shop-vac filters from home depot rather than shelling out $30 for the good stuff from foam factory. Someone else had compared the two and said they looked pretty similar spec wise and sounded good, so I said why not. Second pic has the new foam in place. Something interesting about the Ia line is that they have metal wire protecting the walsh from the front, sides, and top. It also has the bracket going over it with a pin in the center that goes into the foam and keeps it centered on in the tweeter cone. The more common Monitor IIa Walsh's are less protected and have a center rod to help keep everything centered.
The cabs were pretty rough looking on the outside, but nothing a little restor-a-finish and wax couldn't fix! See the left vs the right... guess which one I already treated. I also carefully spray painted the wire enclosure protecting the Walsh's with black spray paint to spiff them up.
New grills also were in order because the rough looking cosmetics of the front (just hide it all right?). I decided I wanted the Walsh's to appear visible because of their unique look, so I designed a grill that should go up to the Walsh's, and then a square grill to also go on top of the cabinet. Here's the simple frame for the grill I whipped together (not a great woodworker) before I covered them with black grill cloth ordered from parts express.
The final speaker with the front and top grills on. I was able to source some small infinity badges that are in the bottom left hand corner of each grill (hard to see in this pic), but not the original badges unfortunately.
I have them paired with a Marantz 1200 (built at roughly the same time as these), and Jesus does this system kick! The bass is pretty unbelievable. I get a meaningful response on these down to 22 Hz! Tight and punchy too. Imaging is good, real broad sound stage, nice 3d effect too, especially on centered vocals. Detailed, but very easy at the same time. Everything sounds very natural, especially the highs. You can hear the warm resonance of an acoustic guitar, but also still get the fingers slipping on the strings sounding right. My Thiel CS2s are more detailed and have a bit more defined of a sound stage, but these infinities make them feel stiff. It's like the Thiels are transmitting exactly what's at the microphone for an instrument, while the infinities are sitting a foot or two away. The infinities sound shockingly good for their age. I haven't found anything that sounds bad on them per se. I would describe them as all rounders, maybe spiking a bit on the low end and high end coverage/clarity, but all in all a very pleasing and easy speaker to enjoy. Plus, my wife likes them, so they're here to stay!
