Acoustic Control Corp 626 -any info out there?

JayMX

So I have a problem with purchasing old speakers... and this time they weren’t Polks... but I know there’s a lot of knowledg in this group so I figured I’d float some questions...

Today I was browsing the local thrift store and came across a heavy pair of old cabinets I’d never heard of. Acoustic Control Corp 626's for $10ea. Someone has kindly painted the walnut cabinets black and replaced the 12's (I find reference online that the originals may have been made by “Eminence”, one photo I found showed a square magnet) with some nasty (cheap) Realistic drivers. Is there anyone here familiar with the mfg? From what I find online, an older California based hi-if company (CSI) was purchased in the 70's by Acoustic, who built (and still builds) guitar amps and cabinets. I’d really like to find a pair of original drivers or, an equivalent set for when I douse the Realistics in gas and have a sacrificial burning to the Audio Gods....

Thoughts? Thanks all!

What they should look like (photo from Google search):


The cabinets I picked up which will be refinished and re-worked:

xschop

Are you planning an original restore or resto-mod?

mhardy6647

well, the tweeter is one of the early, venerable Philips polycarbonate dome drivers. Some folks hate 'em; I actually rather like them.http://www.troelsgravesen.dk/WWDT.htm

As to the MR and the woofer, check the back for EIA manufacturer codes if you can find any photographs of the original's innards. Or dig deep on other hifi fora. Eminence's EIA code was (and is) 67. CTS is 137. Those, I reckon, are the most likely suspects for something like these. The problem is that, even if the woofers were made by Eminence, they could have been any of dozens of 'standard' models, or it's just as likely they were bespoke (so to speak) OEM drivers made to the loudspeaker company's specification.

EIA codes (one of many sources): https://www.tedweber.com/speaker-codes-application/ (see also their link to more codes on that page!)

I will say (not that you asked) that I'm not seeing much there of interest -- although the boxes look well constructed. Per the reply immediately above -- it might be well worth repurposing the boxes with good, modern drivers and an appropriate XO design to make the most of what's there. One may calculate the volume of the box and the port volume to work out the tuning of the BR, and work backwards to identify a woofer with appropriate Thiele/Small parameters. The sensitivity of the chosen replacement woofer can be used to identify appropriate MR and tweeter drivers. www.partsexpress.com (and their speaker builder forum) and www.madisound.com are outstanding resources for loudspeaker DIY -- and there are others as well.

HTH, if only a wee bit.

mhardy6647

Does that crossover "network" only consist of two capacitors and a pair of L-pads? Or are there also one or two inductors (coils) in there?

I can't tell for sure from the photo... if there are only two first order XO elements for the MR and tweeter, that's pretty... primitive... for a three-way.

FestYboy

Also, just from the pics, and rough math in my head, that port appears to be tuned for 80-100hz (awful). Elbow it extend it and add a flare internally. Is there any internal bracing to speak of?

JayMX

Thanks guys. I grabbed the cabinets because of the positive comments I found from internet searches and the quality construction. I really hadn't made a plan yet, but resto-mod looks like the better route. A full restore might be tricky and not be worth the $$. The cabinets are in quite good shape and with a little sanding and finishing should look very nice.

As recommended above I'll do a little math and look into some new drivers. @mhardy6647 - yes, that's all the "crossover" consists of. Might be fun to build something new. @FestYboy, yes re-tuning the port may be in order, and there is a decent brace between the front and back directly between the tweeter & 12".

Fun project all around! I appreciate the insights.

xschop

Is the midrange open-back?

JayMX

xschop wrote: »

Is the midrange open-back?

Nope, it’s really interesting. They’re actually loaded in their own cardboard tube “enclosures” which are sealed on the back. The mids actually sound really smooth.



Also I sanded one of the cabinet bottoms and oiled the walnut just to see how they are going to look. Sexy stuff under that old black paint...

FestYboy

Nice pictures, that better look at the insides makes me rethink the port tune (longer than I initially thought). Putting in the elbow in will get the mouth away from the batting (good thing). Not sure the batting is even needed with a different woofer. Should make for an interesting build, lots of tinkering!

xschop

Nice grain. I asked about modding and mids because I saw a resto-mod where the guy top-mounted the midrange on the cabinet in an open back tube. Sounded superb.

What are the cab dimensions?

JayMX

xschop wrote: »

What are the cab dimensions?

Interior dims: 8 1/8”deep, 14 1/4” wide, 22 1/2” tall. The mid “enclosure” is 3 3/4” deep & 5 1/4” dia. Port is 7” deep & 3 3/4” dia.

xschop

Close to CRS volume... Just sayin
I'm with Festy, that port just looks odd.

FestYboy

JayMX wrote: »

xschop wrote: »

What are the cab dimensions?

Interior dims: 8 1/8”deep, 14 1/4” wide, 22 1/2” tall. The mid “enclosure” is 3 3/4” deep & 5 1/4” dia. Port is 7” deep & 3 3/4” dia.

Did the math: that port is tuned for 45Hz, definitely not low enough. You'll need to double the length to get into the mid 30s, elbow required. Or another option: make the port 2.75" in diameter and run the same length to get to the mid 30s

JayMX

Got more info. Confirmed that the original 12's were by Eminence. On the square magnets the following was stamped: 130058 67-8009. Eminence tech support told me that they were too old for any good records, except that they were 4ohm, with a 2” voice coil and a 30oz ceramic magnet. Based on the cabinet volume ~2200cu in (total minus “mid-enclosure”) does anyone have any driver recommendations?

mhardy6647

4ohm, with a 2” voice coil and a 30oz ceramic magnet.

Well, that's helpful & interesting -- fairly beefy woofer. They couldn't tell you the sensitivity, Fs, or what kind of surround it had?

the woofers you "confirmed" were made the 9th week of 1980 (but you probably knew/figured that out already)

So 2200 in^3 = approx. 1.27 ft^3

-- and the ported enclosure is tuned to 45 Hz from the factory.
I am guessing (and this isn't a particularly educated guess!) that the Fs of the original woofer might have been ca. 60 Hz (i.e., a "pro sound" kind of driver)?

Looks like the sensitivity of that (4 ohm version? it should be marked on the magnet) of the Philips "world's worst dome tweeter" is ca. 90 dB (@ 2.83 VAC @ 1 meter?) based on the curves at http://www.troelsgravesen.dk/WWDT.htm

So, you want a woofer with sensitivity in that neighborhood, too (although of course the MR & tweeter can be padded down a bit if need be).

Do you (the OP) know anything about the MR drivers?

JayMX

@mhardy6647, awesome info. Thank you! The woofer number I found referenced on another thread about these old gals. The surrounds were foam and from what I can see they had a paper cone. I’m making an assumption that they were consistent with loading the same drivers in all of the 626's.

The tweeters are actually Matsushita Heavy Industries (Panasonic) EAS-9KH05S. They’re 8ohm. The “grill” and front cover plate are a litttle different. However, the magnet and mounting plate for the soft dome/wiring wiring looks identical to the Phillips unit you referenced. So I’m sure they’re very similar... not sure who knocked who off first?

The MR's are a mystery as they’re sealed up in their little cardboard cocoons and I can’t find a way to extract them without damaging the mounting.

More sanding tonight revealed more beautiful walnut... Excited to rehab them, love this hobby. Thanks for all the insights!

mhardy6647

The Panasonics are a clone/knock-off of the Philips. Indeed, I have a pair of the Japanese ones, too(sold by Lafayette, but almost certainly Panasonic/Matsushita OEM) -- although the ones here have a different colored dome (milky instead of clear plastic) compared to the Philips.

I looked at current 4 ohm Eminence drivers on Parts Express last night - but they're way more serious drivers than what you'd want to put in those little boxes; and they're also more expensive!

pkquat

These remind me of a Klipsch Heresy sized cabinet. Would one of those replacement drivers work? They should be high efficiency. I have heard there is a port mod for them to give them deeper bass and a fuller range. These look closer to the ported "pro" version of the Heresy (KP-120?) that were mated to large theater sub boxes. These had a high port frequency and roll off, but could vibrate just about anything in their frequency range.

JayMX

They sure take teak oil nicely.,.

pkquat

WOW!!!

JayMX

Finally had some time today to get these cleaned up and running, ended up needing tweeters but found an affordable pair on eBay. The walnut cleaned up beautifully. They sounded better up off the floor, but my Monitor 7 stands don’t fit them very well... might build some low profile stands to raise them up 4” and a ~5deg tilt.

Even with the RadioShack 12's loaded in them they actually sound surprisingly warm and smooth. The L-Pads help to tame the tweeters. I think some 12's with white cones would look pretty cool in the cabinets. We'll see how much $$ I can justify dropping into them... I mapped out the crossover, which I may re-cap because it’s super simple. However, I may add a low pass filter for the woofer. The mids are crossed over at ~1.3K so maybe low pass at 500? Thoughts? Thanks again for all the input!

mhardy6647

In terms of mucking about with the XOs, I offer a suggestion.
If (if!) you think you might have a go at this sort of thing again a few times, you might want to consider in investing in something like this:

https://www.parts-express.com/behringer-dcx2496-ultradrive-pro-digital-24-bit-96-khz-loudspeaker-management-system-cros--248-669

You'll need a couple of more amplifiers as well -- but you can play with crossover points & slopes easily.

There are also amplifiers with DSP and standalone DSPs that might be very useful in empirically optimizing XOs.

JayMX

@mhardy6647 - I have some buddies in the pro audio world and actually was thinking about borrowing a couple of amps and some parametric eq's and do exactly what you’re suggesting. When (if) I find some 12's, I’ll bi-amp and sweep them a little, play with slopes then build a low pass circuit to match. Love this stuff!

mhardy6647

I think it would be a fun exercise if one has the bandwidth (so to speak!) and inclination.



I've been inching towards doing the same thing with my Frankenaltecs.

ricksiri

I have an original pair of 626's. I recapped the crossovers and re-foamed the woofers. Purchased in Los Angeles in 1976.

JayMX

I sold my pair to a friend but if anyone ever comes across a pair of the original 12's let me know. I would still like to make them right for him.

parkway233

Thanks JayMX, mhardy6647 and all for posting concerning the Acoustic Control Corp 626 speakers. I picked up a pair of these heavy speakers for $25 over a year ago at a Goodwill. The walnut cabinets are a bit scratched, but the drivers looked okay. However, the speakers never really sounded that good to me. I couldn't figure it out, but the sound was just off in either one or both speakers. Thanks to the posts on this forum, I decided to take them apart and recapped them. From the information provided above, my woofers in these speakers are Eminence made in Aug, 1977.


In fact, the speakers were labeled on the inside as being constructed in Aug, 1977.



Well the original caps are shown here:


I replaced them with new caps for a total expense of $5.00, put it back together, and...wow, the speakers sound beautiful now! I had never done this before and I was amazed at the difference. After 41 years, I guess, one or more of those original capacitors were just not as good as they used to be.


Thanks again to everyone for giving me the information I needed to pursue saving these speakers.

JayMX

Brother, I would pay good money for a pair of those original Eminence drivers. Even with the nasty old mismatched replacement 12's that were loaded in the pair I reworked, they were great. I'm sure the original drivers would make them that much better for my friend. Rock on!!