• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Let's share old, cheap-ish speakers with good measurements

Destination: Moon

Senior Member
Joined
Feb 28, 2021
Messages
478
Likes
314
Location
Western USA
I'm not sure how these measure but since there seems to be a lot of old infinity speakers, here's ours.
Infinity Modulus. Still running the original sub too.
 

Attachments

  • 20210618_085600~2.jpg
    20210618_085600~2.jpg
    217.1 KB · Views: 183

antennaguru

Senior Member
Joined
Jun 16, 2021
Messages
391
Likes
416
Location
USA
I was able to pick up a pair of IMF Electronics CM2 (Compact Monitor 2) loudspeakers a few years ago for an inexpensive price. These are a 50 year old pair of modest size bookshelf/stand-mount speakers that are a 2-Way with an 8 inch woofer and a soft dome tweeter. The speakers were working and the drivers were fine so I renovated them by pulling the woofers and then the crossover networks, and replacing all of the capacitors with matched replacements from Falcon Acoustics in the UK. Even though the woofer voice coils were not rubbing I inverted the woofers when I re-installed them - to offset 50 years of gravity on the suspensions and spiders. I also refinished the walnut veneer with a couple of coats of Tung Oil Finish. They are a resistive aperiodic bass reflex design and sound very good.

The closest contemporary speaker to these would be the Harbeth 30 which are the same size cabinet with the same size drivers, but with a high Q tuned port for the bass reflex tuning. I prefer the way the IMF CM2 sound, as they have smoother midbass response to my ear.
 

antennaguru

Senior Member
Joined
Jun 16, 2021
Messages
391
Likes
416
Location
USA
I was able to pick up a pair of IMF Electronics CM2 (Compact Monitor 2) loudspeakers a few years ago for an inexpensive price. These are a 50 year old pair of modest size bookshelf/stand-mount speakers that are a 2-Way with an 8 inch woofer and a soft dome tweeter. The speakers were working and the drivers were fine so I renovated them by pulling the woofers and then the crossover networks, and replacing all of the capacitors with matched replacements from Falcon Acoustics in the UK. Even though the woofer voice coils were not rubbing I inverted the woofers when I re-installed them - to offset 50 years of gravity on the suspensions and spiders. I also refinished the walnut veneer with a couple of coats of Tung Oil Finish. They are a resistive aperiodic bass reflex design and sound very good.

The closest contemporary speaker to these would be the Harbeth 30 which are the same size cabinet with the same size drivers, but with a high Q tuned port for the bass reflex tuning. I prefer the way the IMF CM2 sound, as they have smoother midbass response to my ear.

I thought I should add a picture of this renovated 50 year old pair of loudspeakers, that are quite comparable to the modern day Harbeth 30 (30, 30.1, 30.2) that cost several thousand dollars. The IMF's Aperiodic Bass Reflex Loading is via the black foam covered opening at the bottom of the cabinet. That thin layer of very open (not dense) black cosmetic foam covers a deep wide rectangular opening under a baffle that is filled with a dense foam, the very rear of which is open to the woofer back wave:

IMF CM2 by antennaguru uda, on Flickr

http://www.imf-electronics.com/Home/imf/speaker-range/compacts/compact-monitor-ii

From Stereophile is this measurement of the Harbeth 30.2 Anniversary ($6500 MSRP) showing the pronounced mid-bass hump:

Harbeth 30.2 Anniversary $6.5K by antennaguru uda, on Flickr

Here is some Pink Noise played through the IMF CM2 and recorded with a BOYA measurement microphone plugged into my iPhone running an Audio Spectrum Analyzer App. Please note the reduction of the mid-bass hump and otherwise similar response:

IMF CM2 Pink Noise Slow by antennaguru uda, on Flickr
 
Last edited:

Bluey

New Member
Joined
Aug 12, 2021
Messages
4
Likes
0
I was able to pick up a pair of IMF Electronics CM2 (Compact Monitor 2) loudspeakers a few years ago for an inexpensive price. These are a 50 year old pair of modest size bookshelf/stand-mount speakers that are a 2-Way with an 8 inch woofer and a soft dome tweeter. The speakers were working and the drivers were fine so I renovated them by pulling the woofers and then the crossover networks, and replacing all of the capacitors with matched replacements from Falcon Acoustics in the UK. Even though the woofer voice coils were not rubbing I inverted the woofers when I re-installed them - to offset 50 years of gravity on the suspensions and spiders. I also refinished the walnut veneer with a couple of coats of Tung Oil Finish. They are a resistive aperiodic bass reflex design and sound very good.

The closest contemporary speaker to these would be the Harbeth 30 which are the same size cabinet with the same size drivers, but with a high Q tuned port for the bass reflex tuning. I prefer the way the IMF CM2 sound, as they have smoother midbass response to my ear.
My CM2's which I bought in the early 80's are still working fine, the only thing I've replaced being the brown foam front covers and black foam at the bottom of the speakers, both of which eventually fell apart. However, the veneer on top of the cabinets could do with refinishing, so I wondered what you might recommend prior to applying Tung Oil Finish.
 

antennaguru

Senior Member
Joined
Jun 16, 2021
Messages
391
Likes
416
Location
USA
My CM2's which I bought in the early 80's are still working fine, the only thing I've replaced being the brown foam front covers and black foam at the bottom of the speakers, both of which eventually fell apart. However, the veneer on top of the cabinets could do with refinishing, so I wondered what you might recommend prior to applying Tung Oil Finish.

Hello! My cabinets had a few veneer chips on the lower edge that sticks out and a bunch of white scrapes where it looked like someone carrying them brushed against a white painted hallway. The biggest defect was that most of the circular hook fasteners for that old grill foam were still stuck on the cabinet fronts, and those fasteners that had fallen off left a hardened glue residue behind. I was able to find the new replacement black open cell foam I used that's only about 3/8 inch thick to install in front of the dense ugly green foam at a tropical fish supply house for use in aquatic filters. I used Isopropyl Alcohol on 3M Scotchbrite fine grit pads, brushing with the grain to get off everything except those dots of hard glue from the hook discs. For those I laid the speaker cabinets on their back and kept wetting the glue with Alcohol until it finally relented its grip and let me scrape it off with a plastic chisel looking tool for removing emblems from cars - bought from an automobile refinishing supply catalog. However you could easily make one by cutting down a plastic ice scraper to 1 inch wide and using a file to apply a chisel point to it. Alcohol and those two mechanical approaches got all of the junk off, plus the 3M pads acted like a very fine sandpaper. The next day I applied a coat of Tung Oil finish, and a second coat the following day. Last step for the veneer chips: I filled them with a Minwax scratch crayon/pencil that was the correct tone - it's basically a colored wax pencil you can buy at a paint store and use like a crayon. The re-finishing job has held up and they still look and sound nice today!

I would recommend recapping the crossovers as the caps are available inexpensively in a set from Jerry at Falcon Acoustics in the UK. He matches them and it's easy enough to remove the circuit boards which are held in place by tye-wraps that can be cut to release the boards and then replaced upon re-installation. These were meant to be serviceable. I have heard of old caps exploding, and certainly my old caps had drifted in capacitance value.
 
Last edited:

Bluey

New Member
Joined
Aug 12, 2021
Messages
4
Likes
0
Hello! My cabinets had a few veneer chips on the lower edge that sticks out and a bunch of white scrapes where it looked like someone carrying them brushed against a white painted hallway. The biggest defect was that most of the circular hook fasteners for that old grill foam were still stuck on the cabinet fronts, and those fasteners that had fallen off left a hardened glue residue behind. I was able to find the new replacement black open cell foam I used that's only about 3/8 inch thick to install in front of the dense ugly green foam at a tropical fish supply house for use in aquatic filters. I used Isopropyl Alcohol on 3M Scotchbrite fine grit pads, brushing with the grain to get off everything except those dots of hard glue from the hook discs. For those I laid the speaker cabinets on their back and kept wetting the glue with Alcohol until it finally relented its grip and let me scrape it off with a plastic chisel looking tool for removing emblems from cars - bought from an automobile refinishing supply catalog. However you could easily make one by cutting down a plastic ice scraper to 1 inch wide and using a file to apply a chisel point to it. Alcohol and those two mechanical approaches got all of the junk off, plus the 3M pads acted like a very fine sandpaper. The next day I applied a coat of Tung Oil finish, and a second coat the following day. Last step for the veneer chips: I filled them with a Minwax scratch crayon/pencil that was the correct tone - it's basically a colored wax pencil you can buy at a paint store and use like a crayon. The re-finishing job has held up and they still look and sound nice today!

I would recommend recapping the crossovers as the caps are available inexpensively in a set from Jerry at Falcon Acoustics in the UK. He matches them and it's easy enough to remove the circuit boards which are held in place by tye-wraps that can be cut to release the boards and then replaced upon re-installation. These were meant to be serviceable. I have heard of old caps exploding, and certainly my old caps had drifted in capacitance value.
Thanks for that comprehensive feedback. Fortunately, my cabinets have not suffered much in the way of veneer chips. The six circular velcro fasteners are fine and do a good job of holding the new acoustic grill foam covers I bought from Speakerbits in Melbourne. I just wonder whether the Tung Oil Finish will provide a uniform appearance to the tops of the speakers or whether I need to use coloured wax beforehand? Thanks also for the tip regarding recapping of the crossovers.
 

antennaguru

Senior Member
Joined
Jun 16, 2021
Messages
391
Likes
416
Location
USA
Thanks for that comprehensive feedback. Fortunately, my cabinets have not suffered much in the way of veneer chips. The six circular velcro fasteners are fine and do a good job of holding the new acoustic grill foam covers I bought from Speakerbits in Melbourne. I just wonder whether the Tung Oil Finish will provide a uniform appearance to the tops of the speakers or whether I need to use coloured wax beforehand? Thanks also for the tip regarding recapping of the crossovers.

The Tung Oil finish is basically an oil with some varnish mixed in, so it goes on with a cloth like oil and soaks in but it hardens due to the varnish compounds to last much longer than just an oil finish. It won't stick to the colored wax fill pencil fill which is why I suggested that step comes last after the Tung Oil is dry. Speaker tops often have some challenges such as water marks from beer bottles set there, and even burn marks from cigarettes that rolled out of an ash tray placed there. Those are both harder to remove but the Alcohol on the pad will minimize much of it and specialty techniques are needed for what's left.

When I has in college in the 70s and early 80s getting my degrees, I sold many of the speakers that I had built to colleagues who heard them and wanted a set. The were all 2-way-8 designs and the cabinets varied slightly in dimensions with around two internal cubic feet of volume, and a selling point was that I wrapped the particle board cabinets with Formica brand laminate in a wood grain finish meant for countertops. Those tough Formica clad cabinets looked good while laughing off wear and tear from constant moving, beer bottles and you could even snub out a cigarette on the Formica cladding with no mark. If your speaker tops are really bad when you get done then my recommendation would be to start over with Alcohol on 3M pads to get the finish off. Then source some Formica laminate with a wood grain close to what's on the cabinets. Cut it roughly to size with a slight overhang all around, and then coat the speaker top and the back of the Formica with contact cement. Let the contact cement dry for 20 minutes and set the Formica on the speaker top. Press it firmly down for good adhesion using the heel of your hand, a rubber roller or a small rubber mallet. Then run a router with a laminate trimming bit around the edge, and you'll have a super durable and long lasting speaker top. Some of those speakers I built over 40 years ago are still around today, and very presentable. I have noticed some current speaker manufacturers are setting a durable black top on their speaker cabinets to avoid this very problem. Today Formica is available as "Color-Core" so the color of the top goes all the way through the laminate so its edge when trimmed is the same color as the top, so very suitable still after all of these years. BTW, IMF used Formica on some of their larger cabinets to stiffen the panels while providing a more durable wood-like finish. I didn't know about that back then and though using Formica was one of my personal trademarks...
 
Last edited:

Bluey

New Member
Joined
Aug 12, 2021
Messages
4
Likes
0
They are not that bad, just a little mottled/speckled compared to the sides of the cabinets, as can be seen in the photos, so perhaps the Tung Oil Finish is all that's required. I have some Gilly's dark floor polish but I suspect that may present a problem with adhesion of the oil. I also have some Danish Oil but don't know whether that's the same or as good as the Tung Oil Finish.
 

Attachments

  • IMG_6239.JPG
    IMG_6239.JPG
    290.3 KB · Views: 122
  • IMG_6238.JPG
    IMG_6238.JPG
    229.9 KB · Views: 105

antennaguru

Senior Member
Joined
Jun 16, 2021
Messages
391
Likes
416
Location
USA
Fornby's Tung Oil Finish is inexpensive and gives a reliable finish without darkening the wood, as you can see in the picture of my speakers. Your speaker tops are not that bad and some 3M fine abrasive Scotchbrite padding with alcohol, with the grain, and then wiping with a clean white cotton cloth, will even up and prepare the wood for the application of a Tung Oil finish. I would plan on doing the whole speaker cabinet and not just the top. As I mentioned the Tung Oil finish hardens after application as it is a combination of oil with a varnish-like finish agent (in theory it's extracted from the Tung tree nut). Many Teak Oils and Danish Oils are just Oil so leave only a very temporary effect, similar to applying Orange or Lemon Oil to furniture. They would need to be removed with alcohol before applying an actual finish product. Plain Oils are fine to use occasionally AFTER applying a hardened finish product. The only other such finish product I know that is like Tung Oil in the manner in which it also hardens and leaves a more permanent finish is WATCO Teak Oil. Other than those two I cannot recommend any others for a simple re-finishing application as I described.

You can also go ask a specialist in a paint store, which would probably be better than getting an electrical engineer's opinion of wood finish products. I'm an EE, and even though I have done a lot of wood working and finishing I am only accustomed with using products I have already used and learned to trust.
 

Bluey

New Member
Joined
Aug 12, 2021
Messages
4
Likes
0
Perfect! I shall try the 3M abrasive Scotchbrite padding with alcohol followed by the Tung Oil Finish. Thanks again for your recommendations.
 

amadeuswus

Active Member
Forum Donor
Joined
Jul 8, 2019
Messages
277
Likes
265
Location
Massachusetts
I haven't been able to find measurements of the Energy Connoisseur C-4. Perhaps this speaker wouldn't be quite as smooth as some of the others in the series (large mid-woofer). But here's a pair on Craigslist in the Boston area if anyone wants to spend $120 to find out:

https://boston.craigslist.org/gbs/ele/d/belmont-energy-connoisseur-c4-speakers/7427454693.html (not my listing)
 
Top Bottom