60 Degree DIY Mid Hi - AKA PM60

Peter Morris said:
A couple of comments ...

The quick sim I did indicates the 12NDH-4 would be one of the best choices you can get for the PM90/60.

If you use the XT1464 horn in the standard configuration only BMS driver will fit. (also check that the 4594 will still fit with the 12NDH-4).

B&C DCX464 /HF950 will fit I think, but check. Also the 464 with the PR614 may fit - but check I have not tried it.

I think the Ciare PR614 is possibly a better horn than the XT1464 ... BUT ... the XT1464 is bigger and goes lower which is an advantage in the PM60.

The difference between the PMA60 and the PM60 is the mids (100 - 700Hz} have a 5-6 dB output advantage.
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Peter just to confirm we are talking about the -4 not the -3 correct? The -4 has a slightly higher motor force, however the -3 has greater sensitivity and lower Mms and the -3 has a ruler flat response of 100-101db from 100-1k

Thoughts between the two? I have on hand a pair of -4s but need to make a decision quickly if I’m going to go to the -3

Positive is that the depth of the Ciare PR614 is only about 186mm, which is about 22mm shorter than the XT.

The Ciare horn is appx 100mm shorter than the XT (and 50mm narrower) will this have any negative impact on the proximity center to center of the mid to HF cohesion at ~650hz?

Where is everyone crossing the BMS (not B&C) to the NDLs?

Thanks again.

Sent from my iPhone
 
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The 12NDH-4 produces a good response in the PM90/60, the 12NDH- 3 gives an even better / smoother response but has less X-max. I guess it becomes a matter of where you want to cross to the subs etc. etc.

In the PM90/60 the response will not be flat, quite bumpy and MUST be EQ-ed flat. Because every thing is operating in the piston range you can fix it with EQ without any problems ... i.e. not sounding processed as some people say.

In the PMA60 the low/mid response will be flat.

What I don't know is how well the Carie PR614 will perform if you cross it lower than the recommended 800Hz. The PM60/90 needs to be crossed at 700Hz or less.

I am crossing it at about 680Hz on the PMA60 but its a big compression driver not having to do a lot of work. With the PM90/60 it will need to do a lot more work to keep up to the 2 horn load 12's. Not sure how the PR614 will go, it was not available when I started the project. I don't expect the spacing to cause directivity problems, its just the the horn MAY not provide enough loading for the driver if you cross too low - in this case I don't know.

The XT is specified to be useable from 500Hz, and I know RCF use the HF950 as low as 650Hz so these will work with the PM90/60.

The PMA60 was designed and built during COVID and as such I have had very little opportunity to test it in every application.
 
Peter thanks much! Im going to put the 4594 on the Ciare horn and take some measurements and post them here. They will be crude as Im not a pro, but usable. I will A/B with the XT1464 for comparison.


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What is the net volume of the woofer chamber and tune with the ircular ports? I’m doing a final check on driver specs and want to ensure excursion is controlled and see what it will look like on the sim.

Ideally Im looking for about 2cuft and 95-97hz tune for this driver


Sent from my iPhone
 
Chris Burns said:
What is the net volume of the woofer chamber and tune with the ircular ports? I’m doing a final check on driver specs and want to ensure excursion is controlled and see what it will look like on the sim.

Ideally Im looking for about 2cuft and 95-97hz tune for this driver


Sent from my iPhone
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From memory there is about 55 -60L inside the PM90/60 but its tuned lower than that - you need to do a SIM with horn response as I suspect 95 - 97 is too high, it needs to be more like 60- 70Hz depending on the driver to get a useful response.
 
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Peter Morris said:
From memory there is about 55 -60L inside the PM90/60 but its tuned lower than that - you need to do a SIM with horn response as I suspect 95 - 97 is too high, it needs to be more like 60- 70Hz depending on the driver to get a useful response.
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I believe we settled on 80 Hz once upon a time.

If the reason for the 97 Hz tune is because you're afraid of hitting excursion limits, I would reconsider. Remember that you'll likely cross the driver over at 80-100 Hz anyway, so eventual response be 3dB down (and at half excursion) at the x-over frequency. Ultimately, I think you will get a much better sounding result by tuning lower than you think you will crossover. It will also make time aligning crossovers easier.
 
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Hi Max

You are 100% correct, the original PM90 was tuned at 80Hz (I had to look it up :-). After that every one want a 60 degree box. It used the 18sound horn and the box had to be made deeper and a bit wider. This increased the volume a little. The port size was unchanged so it was tuned lower. I will do an impedance sweep and check.

And ... yes you will get a better by ensuring you still have output below the crossover point.
 
Hi all, is there anyone UK based who would be able to provide me a quote for a flat pack for a PM60? If anyone can point me in the right direction that would be much appreciated. Many thanks in advance.
 
Carl Klinkenborg said:
Apologies if I missed it, but in the DCX464 is there a delay required between the mid and HF sections due to diaphragm spacing as in the BMS?
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Hi Carl, i have a DCX464 on a 18sound horn in front of a messure setup now.
If you want i can make a transfer mes. Just give me the filter type and freq you want to use.
filtering wil be on an powersoft X platform.
 
I finally heard from B&C:

Hello,

the MF section on the DCX464 is delayed about 50 microseconds (0.05 ms) versus the HF section due to the different MF and HF sound path lengths inside the driver. Compensation of this delay may be useful or not, depending on the filter design which brings its own phase shift at crossover frequency. Let consider the FB4648 that is the passive crossover specifically designed for the DCX464-8 coupled with its horn ME464. The MF and HF filtered responses intersect just below 4 kHz at a level about 6 dB lower than the MF+HF summed level. This means that at the crossover point the MF and HF filtered section are in phase. This is possible because the phase shift introduced by the passive crossover compensates the one introduced by the two sections of driver alone.

Hope this helps to clarify this matter.

Best regards, Giacomo Bartolini
 
Hi yes, exactley it is 0.05
This diffrents from 0 degrees on this frequency is making 50 degrees phase shift.
The filters was 24LR 630hz and 24RL 3200hz
 

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Jan Jaap Derksen said:
Hi guys. Due to the Covid lock down in our country i was not able to finalize the cabinets till now. Also a proper test i could not yet do.
As you can see i build 2 cabinets with fully intergraded pascal xpro-2 amp (i bought this amp before i chanched over to the DCX464 :cry: otherwise it would be the xpro-3)and an additional dsp sound board with FIR filtering. Analog input and AES . I extend the cabinet at the back with 35mm to fit in all stuff.View attachment 209387

The speakers are B&C 12NDL76 16 ohm each and put these paralel to each other. I chose 16ohm to use the maximum power of the amp into the speakers and as you can see at the pictures i have made at the back side a speakon output for second slave cabinet. (to build in the futhure)
The B&C dcx464 i made a passive crossover at 4000hz. The exact weight of the cabinet is at the moment 38.89kg. This is pretty heavy but not as bad as i thought it will be.
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:D:D:D:DI love this. Would love to see more pictures as well as ,I would love to see the designed CAD file is possible as well🙏🙏🙏
 
Hi, I'm currently planning on building a pair of your 60 degree mid highs. I'm thinking I will build just a pair to start but will probably want to add another pair in the future. I'm just wondering if most people buy the 12NDL76 16ohm version or 8 ohm version when planning to run two pm-60's a side in parallel? I don't want to buy the 8ohm mid drivers only to find out i need to switch to 16 ohm versions if i want to double up later. Any feedback is greatly appreciated!

Cheers, Leif
 
I have bought 8ohm drivers with a view to a second amp, or a single 2ohm capable amp if I ever build another pair the future. You would need to buy an amp with huge voltage output to be able to drive an 8ohm load, but I say this as someone for whom huge dynamic headroom is key.
 
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