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Author Topic: Meyer JM-1  (Read 3743 times)

Jim McKeveny

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Meyer JM-1
« on: February 12, 2014, 07:55:47 am »

Does anyone have experience with this model?

I originally viewed it as a grownup L'Acoustics ARCS, but then I looked closer: The HF is crossed over at 520hz? That is a lot of spectrum for a diaphragm to cover, especially at high power levels. Breakup modes and IM distortion are pretty big beasts to slay across that many octaves..

Any thoughts?



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Art Welter

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Re: Meyer JM-1
« Reply #1 on: February 12, 2014, 04:22:07 pm »

Any thoughts?
I have not heard the JM-1, but have heard the 50x40 CQ-2 which also uses a 4" diaphragm 1.5" exit, but crossed at 900 Hz above a 3" voice coil 15.
It certainly had plenty of high end, but sounded pretty hashy when driven at all hard.
Light jazz sounded OK, but with a full band with plenty of mid/high content reminded me of why we started using low mid drivers to reduce bandwidth on mid/HF many decades ago.

The JM-1 uses a narrower, deeper 20x60 horn which should load lower, and is above a presumably less sensitive 4" coil 15" woofer, which would make excursion demands on the HF somewhat comparable, though in a 4 or 5 wide array where the woofers tend to sum while the HF remains discreet, I'd think they would start to sound even more (dis)stressed than what I have heard of the CQ-2.

The breakup modes sound worse the louder they are driven, so for quiet, short throw shows they could be perfectly acceptable, but they would not be on my short list if loud and clean was the goal.

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Thomas Dameron

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Re: Meyer JM-1
« Reply #2 on: February 12, 2014, 04:57:46 pm »

M2D are the same idea.  It makes for a nice sounding speaker but not a very loud one.

thomas d.
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DavidTurner

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Re: Meyer JM-1
« Reply #3 on: February 12, 2014, 10:48:32 pm »

I have heard them sound really good....

I have not heard the JM-1, but have heard the 50x40 CQ-2 which also uses a 4" diaphragm 1.5" exit, but crossed at 900 Hz above a 3" voice coil 15.
It certainly had plenty of high end, but sounded pretty hashy when driven at all hard.
Light jazz sounded OK, but with a full band with plenty of mid/high content reminded me of why we started using low mid drivers to reduce bandwidth on mid/HF many decades ago.

The JM-1 uses a narrower, deeper 20x60 horn which should load lower, and is above a presumably less sensitive 4" coil 15" woofer, which would make excursion demands on the HF somewhat comparable, though in a 4 or 5 wide array where the woofers tend to sum while the HF remains discreet, I'd think they would start to sound even more (dis)stressed than what I have heard of the CQ-2.

The breakup modes sound worse the louder they are driven, so for quiet, short throw shows they could be perfectly acceptable, but they would not be on my short list if loud and clean was the goal.
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Art Welter

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Re: Meyer JM-1
« Reply #4 on: February 13, 2014, 03:37:19 pm »

I have heard them sound really good....
David,

At what distance, SPL and relative humidity percentage?

Art
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Jon Arneson

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Re: Meyer JM-1
« Reply #5 on: February 13, 2014, 04:19:04 pm »

I have not heard the JM-1, but have heard the 50x40 CQ-2 which also uses a 4" diaphragm 1.5" exit, but crossed at 900 Hz above a 3" voice coil 15.
It certainly had plenty of high end, but sounded pretty hashy when driven at all hard.
Light jazz sounded OK, but with a full band with plenty of mid/high content reminded me of why we started using low mid drivers to reduce bandwidth on mid/HF many decades ago.


One of the advantages of the JM-1P's two-way design with relatively low crossover frequency (besides saving on cost and weight, although neither are terribly low!) is that it maintains its 60deg vertical coverage pattern to within +/-10deg down to 450Hz. The deep horn, a well-matched amp, and some clever signal processing tricks keep the compression driver happy by controlling excursion and distortion.


Quote
The JM-1 uses a narrower, deeper 20x60 horn which should load lower, and is above a presumably less sensitive 4" coil 15" woofer, which would make excursion demands on the HF somewhat comparable, though in a 4 or 5 wide array where the woofers tend to sum while the HF remains discreet, I'd think they would start to sound even more (dis)stressed than what I have heard of the CQ-2.


How so? LF summation in an array increases LF headroom. It doesn't add to the demands on the HF section, which is naturally more efficient than the cone as you mention. Maybe I'm missing something here.


Quote
The breakup modes sound worse the louder they are driven, so for quiet, short throw shows they could be perfectly acceptable, but they would not be on my short list if loud and clean was the goal.


Breakup modes of the HF diaphragm are related to several factors, but I don't think crossover frequency is one of them. If and when they occur in certain designs it's well above 520Hz, 900Hz, 3.24kHz, or whatever your "ideal" x-over freq is. More like >7kHz where wavelength < dome diameter.

To imply that the JM-1P may suffer from HF breakup modes specifically because it's a two-way design (or because you heard "hash" come out of a CQ) is a bit of a stretch IMO.






Jon Arneson


MSLI
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Art Welter

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Re: Meyer JM-1
« Reply #6 on: February 13, 2014, 05:03:17 pm »

LF summation in an array increases LF headroom. It doesn't add to the demands on the HF section, which is naturally more efficient than the cone as you mention. Maybe I'm missing something here.

Breakup modes of the HF diaphragm are related to several factors, but I don't think crossover frequency is one of them. If and when they occur in certain designs it's well above 520Hz, 900Hz, 3.24kHz, or whatever your "ideal" x-over freq is. More like >7kHz where wavelength < dome diameter.

To imply that the JM-1P may suffer from HF breakup modes specifically because it's a two-way design (or because you heard "hash" come out of a CQ) is a bit of a stretch IMO.
Jon,

You are correct, HF breakup "hash" will occur related to diaphragm size, and is independent of the crossover point, which simply requires more excursion for a given SPL from the diaphragm when used lower. One can limit excursion (and SPL) to keep diaphragm excursion related distortion to an acceptable level, which in general in our industry seems any amount less than heard when the diaphragm is not hammering the phase plug.

Since the HF section dispersion is well defined, it does not benefit from the LF summation in an array, which as you say, increases LF headroom.
Since the natural inclination for many operators is to run systems at the limits of headroom, and the HF does not gain any headroom, the breakup modes are pushed harder (and sound worse) when trying to "keep up".

Does the JM-1 use clever signal processing tricks controlling distortion absent in the CQ2?

What signal processing algorithms are capable of eliminating breakup mode and excursion related distortion?

Could you share the THD distortion  charts of the JM-1 HF section at full rated power and it's rated 138 dB?

Art
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Ivan Beaver

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Re: Meyer JM-1
« Reply #7 on: February 13, 2014, 06:49:46 pm »


One of the advantages of the JM-1P's two-way design with relatively low crossover frequency (besides saving on cost and weight, although neither are terribly low!) is that it maintains its 60deg vertical coverage pattern to within +/-10deg down to 450Hz. The deep horn, a well-matched amp, and some clever signal processing tricks keep the compression driver happy by controlling excursion and distortion.


Jon Arneson


MSLI
Just doing the "simple math" and allowing the horn to be 70 (60+10) then it will lose pattern control slightly above 1000Hz.  For 450hz it would have to be twice as large.

Of course the 20 horizontal would lose its pattern control an octave higher.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Jon Arneson

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Re: Meyer JM-1
« Reply #8 on: February 13, 2014, 07:31:18 pm »

Jon,

You are correct, HF breakup "hash" will occur related to diaphragm size, and is independent of the crossover point, which simply requires more excursion for a given SPL from the diaphragm when used lower. One can limit excursion (and SPL) to keep diaphragm excursion related distortion to an acceptable level, which in general in our industry seems any amount less than heard when the diaphragm is not hammering the phase plug.


I keep re-typing a few sentences about horn design / compression driver excursion / distortion but worry I'm veering into trade secret territory... Agreed the diaphragm hammering the phase plug is a universally-accepted threshold of unacceptable distortion!

Quote
Since the HF section dispersion is well defined, it does not benefit from the LF summation in an array, which as you say, increases LF headroom.
Since the natural inclination for many operators is to run systems at the limits of headroom, and the HF does not gain any headroom, the breakup modes are pushed harder (and sound worse) when trying to "keep up".


Sounds like more of an "enough rig for the gig" problem than a loudspeaker headroom problem. Or operators looking to get a particular "sound" from the speakers by pushing them to the limit.

Quote
Does the JM-1 use clever signal processing tricks controlling distortion absent in the CQ2?


Both products share some dynamic limiting techniques but the JM-1P incorporates some new ones we've developed in the years since the CQ's first release.

Quote
What signal processing algorithms are capable of eliminating breakup mode and excursion related distortion?


None that I am aware of since these are non-linear effects. But they can be minimized or prevented when the acoustics, amp, and signal processing are all designed together.







Jon


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Jon Arneson

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Re: Meyer JM-1
« Reply #9 on: February 13, 2014, 07:53:22 pm »

Just doing the "simple math" and allowing the horn to be 70 (60+10) then it will lose pattern control slightly above 1000Hz.  For 450hz it would have to be twice as large.

Of course the 20 horizontal would lose its pattern control an octave higher.


Maybe there's more to the design than you're aware of, Ivan.

There are methods - some well-known, others we've patented - that allow one to extend the vertical directivity of a two-way system well below the horn's natural cutoff frequency.

Why don't you look at the JM-1P in MAPP or Ease if you don't believe the spec I quoted.




Jon

« Last Edit: February 13, 2014, 10:46:32 pm by Jon Arneson »
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