Interesting old speaker w/dual L-pads - diyAudio
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Old 16th October 2014, 08:30 PM   #1
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Default Interesting old speaker w/dual L-pads

While I was cleaning out the house I grew up in recently I had a look at our old stereo system. One interesting thing I found was the Synergistics speakers, a brand no one has ever heard of. My Father bought these in the mid-70's and they were probably a mid-quality range item at the time. The drivers were all flush mounted, the midrange is housed in a closed chamber made of a heavy cardboard tube, and the acoustic suspension cabinet is well stuffed with fiberglass. These speakers have some interesting features I have not seen before. I am curious if any of you have come across anything like these before.

The drivers are all paper cones. The midrange unit has a dual cone and is of Belgian manufacture. I don't know what Belgian company was in the speaker business at that time. The tweeter is a typical 2" paper cone. The woofer does not have markings indicating origin, and it does not have a ferrite magnet like the mid and tweeter have. It looks like it may be an Alnico magnet inside a steel "cage". Finally, the crossovers for both the midrange and tweeter have adjustment pots on the rear plate. This looks like two L-pads. I'm guessing they must have been thinking you could compensate for room size or near wall placement with this adjustment system. I have never seen dual L-pads used.
See the the attached pictures.

The woofers have thick and sturdy paper cones with a lot of raw pulp texture on the back, and the dust caps are linen. You can see the end of the steel pole piece through the caps. The bass is probably the best feature of these speakers - very strong and decently deep, probably 40 Hz. If those woofers were run with a cross-over instead of full range I bet they could sound quite good. I might save them for a project, maybe garage speakers or something.
Attached Images
File Type: jpg Synergistics1.jpg (16.9 KB, 136 views)
File Type: jpg Synergistics2.jpg (49.4 KB, 133 views)
File Type: jpg Synergistics3_mid.jpg (54.8 KB, 132 views)
File Type: jpg Synergistics4_mid-Belgium.jpg (41.7 KB, 131 views)
File Type: jpg Synergistics5-nameplate.jpg (14.4 KB, 129 views)
File Type: jpg Synergistics6_Adj-XO!.jpg (38.4 KB, 64 views)
File Type: jpg Synergistics7_XO-detail.jpg (69.2 KB, 64 views)
File Type: jpg Synergistics8_Woofer-no-ferrite.jpg (59.6 KB, 68 views)
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Old 16th October 2014, 09:27 PM   #2
system7 is offline system7  United Kingdom
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Fascinating old clunker there. I like it! Nice photo essay too.

I suppose it's made in the USA, but the mid is a Dutch Philips AD 5061 M8 on 6uF HP filter. Google it. Almost a full ranger. Can be ferrite or AlNiCo magnet.

The bass looks quite decent too. Rubber roll surround that might come up nicely with some silicone grease. Those linen dustcaps work well, IMO. Like no dustcap at all acoustically.

Cone tweeter on 3uF HP filter. Nothing wrong with that. Could even be that classic Peerless mylar cone used by Mc.Intosh a lot.

Many speakers of this era used series crossovers. Yours is quite simplistic, but you could do a lot with it to improve it IMO. I think you could get it sounding very good.

Simple parallel crossovers discussed here: SEAS Kit 503

Below is a 4 ohm Tandberg HiFi 15 design from this era, which used a series filter on a similar driver compliment. A lost art, IMO. Old speakers always interesting. Thankyou for sharing.
Attached Images
File Type: jpg Tandberg HiFi 15 Front.JPG (22.1 KB, 57 views)
File Type: jpg Tandberg HiFi 15.JPG (51.2 KB, 34 views)
File Type: png Tandberg HiFi 15.PNG (10.2 KB, 48 views)
Good Night, and Good Luck. Best regards from Steve in Portsmouth, UK.
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Old 16th October 2014, 09:35 PM   #3
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But the mid has "made in Belgium" printed on the back

Otherwise faultless.

Looks like simple parallel 1st order for both mid and tweeter. Unless there are some coils I'm not seeing.
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Last edited by mondogenerator; 16th October 2014 at 09:37 PM.
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Old 16th October 2014, 09:59 PM   #4
kevinkr is offline kevinkr  United States
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The name sounds vaguely familiar, might have been someone's house brand. I've certainly seen far worse in that time frame..

A lot of 3 way speaker systems of that era had L pads for the mids and highs, indeed my diy Onken based system does too. (I keep meaning to replace them with fixed resistors, but in 7yrs since I designed these XO never have)

Technically in your speakers they are rheostats since there are only two wires connected, so not really L pads.. The cross over frequency probably varies pretty significantly depending on how the pots are set. These might really benefit from a decent XO, but you'd have to do some basic measurements first.

The caps look more typical of 1960s vintage bipolar electrolytics, but were perhaps left overs in the manufacturer's inventory or perhaps they made that style for longer than I realized.
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Old 16th October 2014, 11:16 PM   #5
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The woofer looks a lot like the CTS 12" we used to use at Infinity, back in the early '70s. Cost us about $12 each, and worked pretty well, if you didn't abuse it. Cone breakup is around 1200 Hz.
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Old 16th October 2014, 11:44 PM   #6
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Ah, of course, Philips! It makes sense they would have some manufacturing facilities in neighboring countries. Do I detect a note of international rivalry there monodegenerator? ;-)

I think it is right that the pots wired as they appear to be would be affecting the X/O points. I did not see any coils hidden in there behind the fiber bats so this must be a woofer running full range, a mid high-passed on the low end and also left full range on the top end, and a tweeter high passed on the low end. All 1st order. Ginning up a series crossover for it would be a fun exercise. Don't know if I can find the time for it.

Thanks for the insights, all!
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Old 17th October 2014, 03:17 AM   #7
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Looking at the front baffle I think the mid and tweeter may have been replaced at some stage
Is that perhaps a Phillips mid? Looks sort of familiar
If the tweeter has been changed the original may have been a paper coned oval
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Old 17th October 2014, 03:35 AM   #8
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On 1st siting,i'd guess the tweeter is the very nice Peerless unit.

Any numbers at all on the woofers.

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Old 17th October 2014, 01:42 PM   #9
kevinkr is offline kevinkr  United States
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I've definitely seen and heard these somewhere, just not sure when and where..

I believe those are the original drivers, not changed out.

They manufacture(d) many things in Belgium, including automobiles interestingly enough. (Adzam aka Belgian Mazda made good vacuum tubes.)
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Old 17th October 2014, 02:30 PM   #10
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I bet a coil on the woofer, a coil and larger cap on the mid and wiring the L-Pads properly would go along ways to making these sound Jim Dandy.
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