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[g'bye, Dick Rees]

Warning:

Satirical picture saves 1,000 words

http://img04.deviantart.net/52e6/i/2011/187/e/1/rusty_mercedes_benz_200_d_by_flame_cze-d3l6p7e.jpg

[Pierre Olivier]

Yes, Mike, I have read all about the different origins of the drivers, and how they are NOT interchangeable with the Meyer-modified units. I have personally removed the jumpers on the HF protection network in the two boxes we use. We are located east of sherbrooke, Quebec.

One thing I have observed is that the cones in the MS-12 tend to be quite "outward". Maybe it's from the years of beign suspended in the air with a slant towards the ground. I tend to think this would place the voice coil in a not-so-optimal place relative to the magnetic field...

[Ivan Beaver]

One thing I have observed is that the cones in the MS-12 tend to be quite "outward". Maybe it's from the years of beign suspended in the air with a slant towards the ground. I tend to think this would place the voice coil in a not-so-optimal place relative to the magnetic field...

Cone sag can happen when drivers are mounted like that.

The old Maryland Sound Clams were notorious for that.  Half the drivers would be "out" and the other half "in"

I have never measured the sonic effects due to the coil being not centered in the gap.

I am sure there would be a measurable difference.  How much is the question.

With cones that are "out" there would be a greater chance of the driver jumping out of the gap and getting physically damaged when pushed hard or below the tuning of the cabinet.

[Doug Fowler]

If I remember correctly the original HF driver was made by Yamaha, the diaphragm no longer available but a replacement from Radian is. Determine what's in each HF driver and if the jumpers have been removed. I believe the M1A is required as the crossover point varies with level. When properly maintained there are few small boxes that sound as good..even better than current product.
I have a fanatical client who continues to use them every week...paired with Chevin power.
 Where are you ?

The xover point does not vary by level.  That's a long standing myth. IIRC Apogee used a variable xover, but I'm not certain.

[Ivan Beaver]

The xover point does not vary by level.  That's a long standing myth.

I first read about the "shifting xover w/freq in Meyer processors" back in the 80s.

I "think" it was the Audio Cyclopedia-but not sure.

As I "understood it", the HP on the HF driver would go higher so less power and excursion was going to the HF driver (the limiting factor)

[Doug Fowler]

I first read about the "shifting xover w/freq in Meyer processors" back in the 80s.

I "think" it was the Audio Cyclopedia-but not sure.

As I "understood it", the HP on the HF driver would go higher so less power and excursion was going to the HF driver (the limiting factor)

I would like to measure one to be sure. 

[eric lenasbunt]

The OP mentioned a host of issues in the OP, but doesn't understand what is wrong. Amps needed repairs, one woofer has a known issue, seems like there are a host of issues.

If you are going to keep these I would say get them factory serviced and up to spec. Otherwise there is really no point. Obviously something is wrong, UPA-1A sound quite nice and flat typically.

Problem is it sounds like could be speakers, processor, or amps. I would want to narrow down by sweeping the speakers with a known working amp and no processor, then adding the processor and sweeping again, then add the newly repaired amp. At some point you will notice a difference OR the speakers themselves will turn out shot.

[Ivan Beaver]

I would like to measure one to be sure.

Of course-just because it is in print does not mean it is true.

It was just a little one or two line statement.  I don't remember the section it was in-other than the loudspeaker section.

[Pierre Olivier]

The OP mentioned a host of issues in the OP, but doesn't understand what is wrong. Amps needed repairs, one woofer has a known issue, seems like there are a host of issues.

If you are going to keep these I would say get them factory serviced and up to spec. Otherwise there is really no point. Obviously something is wrong, UPA-1A sound quite nice and flat typically.

Problem is it sounds like could be speakers, processor, or amps. I would want to narrow down by sweeping the speakers with a known working amp and no processor, then adding the processor and sweeping again, then add the newly repaired amp. At some point you will notice a difference OR the speakers themselves will turn out shot.

You got a point. I'm working on a setup so I can measure the frequency response. I did try to get the system as straight as possible before conducting listening tests: I checked the electronics for proper operation, and made sure the two speakers had identical components and were setup the same.
I would tend to rule out amps and processors, because (1) I have tested them, and (2)both sides sound the same. TDM crossover has been bypassed, and that has changed nothing. Defective speaker has been replaced. So yes, I must now conduct frequency tests to know more. What I had hoped to learn by posting here is: are there known issues with those speakers that can lead them to deteriorate and not sound good.

As for sending them for service, as much as I'd like to do that, it won't happen: Just to send them speakers to California from Quebec will cost more than what we paid for the kit...

[Pierre Olivier]

OK, we have sweeps. I jury-rigged a setup with a portable PC running "Audio Tester 3", Tascam "FireOne" firewire audio interface and MKH-40 microphone. Microphone was one Meter from speaker, mid-point between woofer and horn. Output of FireOne was fed into input of M1A controller. We have two sets of graphs, one made with a 200-point sine sweep starting at 100Hz, 2dB grid. The other with pink noise, 5dB grid.

Looks like the two horns are holding up reasonnably well, except in the upper octave where the left channel's peak at 11K is quite mean. Both sides sharply fall off after that: I wonder if that had somethinh to do with the (deteriorating) foam lens.
Crossover seems good, but below that the woofers really don't perform very well: Quite different from side to side, a dip between 700-1K, and an apparent 2-4dB lack of output especially on the left channel, more evident on the sweep graph. The left channel's woofer is the one with the "outward" cone.
Please excuse the low quality of the graphics, this was hastily done.
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