MCA15RCY replacement - diyAudio
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Old 23rd June 2009, 06:22 PM   #1
gbadaut is offline gbadaut  France
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Default MCA15RCY replacement

I'm using a seas MCA15RCY driver as a medium in a 3 way speaker with an OWI for the highs and an ATOHM D300P04 for bass. The cutoff frequencies are 300Hz and 2.5kHz. It is working fine until a level (volume) at witch the medium start to distort.

I am thinking about replacing the MCA15RCY with another driver like the Seas Excel W15CY-001. More linear excurtion capability, less harmonic distortion. Magnesium instead of paper. But it is a bass/medium driver. So can i expect this driver to be sonicaly better than the mca15rcy when used as a midrange ?

Do you know any other really good driver for that application ?

Thank you.

Guillaume.
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Old 23rd June 2009, 08:17 PM   #2
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have you tried to use steeper crossover slopes? 48db for example
IMO, if you change to magnesium mid drivers, crossover has to be even steeper, plus you'd need a notch filter at 8k.
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Old 23rd June 2009, 11:12 PM   #3
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Default Re: MCA15RCY replacement

Quote:
Originally posted by gbadaut
I'm using a seas MCA15RCY driver as a medium in a 3 way speaker with an OWI for the highs and an ATOHM D300P04 for bass. The cutoff frequencies are 300Hz and 2.5kHz. It is working fine until a level (volume) at witch the medium start to distort.

I am thinking about replacing the MCA15RCY with another driver like the Seas Excel W15CY-001.
...
Metal is not a good idea.
What about de C-Quenze 15 H by Audio Technology (15 H 52 06 13 SD)

Maybe there is also a problem with the (power W) components of the xover. Does the mid has any resistor by the way(?) (5/10W), caps with low voltage(63/100V), or inductors with a thin diameter (0,6<1mm) or bad quality cable connections since it should work good for ~100W.
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Old 24th June 2009, 08:05 AM   #4
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Salut Guillaume !



Your crossover have a problem. No saturation with the MCA15 at high level in this project : Astasia Prject - 3 ways loudspeakers

I always play music loud
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Old 24th June 2009, 09:36 AM   #5
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300Hz is too low point for XO MCA15
500Hz or 600Hz is more preferably, but it is too high for 12" bass

If you don't want adjusting XO point, you need quality midwoofer driver like a W15LY. Or maybe with 12" on bass will be more logical go to 6,5" like SS 18W/8531
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Old 24th June 2009, 10:28 AM   #6
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I would say again, after looking at the xover, check and post the power for M resistors as that should workout (half) the problem.

R2_M=4R7 should be ~/>20W (if not, use 4 power resistors)
R3_M=2R2 should be a good power resistor let's say ~/>10W
R1_M=2R0 should also be, a good power resistor ~/>10W (I'm not measuring or calculating)

Peak power is always a problem as it can be > 100W. If you have 50 volt RMS, can be 70 volts peak, you get ~400 watts across an 6 ohm load. That's why resistors need to be rechecked carefully... now apply the power you use to R2 rating (and to all components).
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Old 24th June 2009, 01:10 PM   #7
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Quote:
Originally posted by jerome69

Your crossover have a problem. No saturation with the MCA15 at high level in this project : Astasia Prject - 3 ways loudspeakers

I always play music loud
Jerome,
Do you mean the xover needs to be redesigned for different components (I think you mean this), or just (there is) some compensation for different saturations on compression, or both.

Guillaume,
If you get a xover and use different speakers, from what was intended, unless you have very close parameters, it needs to be redesigned and tested. I would disconnect the MID from the xover and connect it to the AMP and listen. That should be your image of a good performance having in mind that the woofer and tweeter are not connected. Post after you do some testing, don't use to much power (be reasonable here) the sound should come clean. ~89dB from 200Hz to 3K0Hz. (Do you have a small closed box with the mid?) The MID is your MAIN speaker here not an ordinary mid speaker. A lot of people in DIY fail to realize. Now after this testing if you don't like you can start looking for a different MAIN speaker.
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Old 24th June 2009, 02:01 PM   #8
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Quote:
Originally posted by Inductor
Jerome,
Do you mean the xover needs to be redesigned for different components (I think you mean this), or just (there is) some compensation for different saturations on compression, or both.
Yes I mean The Guillaume crossover need to be redesign correctly.
The MCA15RCY can easily go down 200Hz but the electrical crossover should be 18dB.
The ATHOM D300 P04 , like a lot of 12", can works as high as 500Hz, .

The project, which I give the link, is an other project and I listen to it at high level and I never notice any compression on the MCA15 (500Hz LR2).
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Old 24th June 2009, 02:38 PM   #9
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With a sealed box volume of 4.2 litres, giving a Q of 0.5. A second order electrical filter can provide a 4th order acoustic LR @ 300hz. The driver will fail from thermal overload way before you run out of excursion.

If you're getting some sort of excursion related problems, I suggest you change the xover.
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Old 24th June 2009, 10:50 PM   #10
gbadaut is offline gbadaut  France
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There is no resistor in the direct path of the midrange. Condensators are SCR 400V and self are good quality air-core. I don't think there is anything wrong in this area.

The output of the amp never go higher than 30V peak. This gives a peak power in the 10 ohm resistor of sqrt(30*30/10)=9W max. The resistor is 10W and always stay cold.

If I disconnect the highs and the bass, I hear the distortion, when just playing the mid.

The crossover between the bass and the (mid+high) is done digitaly with the LspCad emulator. This allow me to draw the filter on my computer screen and to immediately ear the result.

I just tried an LR4 crossover and raised the frequency until the distortion disappeard. It seems to me that the sound begins to be really clean from about 400Hz and above. I 'm not sure that the bass driver is able to follow. Perhaps I'm wrong.

Will the W15LY be as good as the mca15rcy for this application ?

Guillaume.
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