PM 60 & 90 settings and alternative drivers.

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Peter Morris

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May 8, 2011
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I have had a lot of requests for settings and alternative drivers that are a little cheaper.

When I have a bit of free time I will post up my Lake LM26 settings. Unfortunately I only have Lake processing and there can be a lot of variation between different processors with the same settings - so I’m hoping people may be willing to post what they have done to help others :)(y)

Suggestions to reduce cost –

Compression drivers
BMS 4594HE – BMS 4594

BMS 4594 with passive crossover

B&C DE1090TN - https://bcspeakers.com/en/products/hf-driver/1-4/8/de1090tn

RCF ND950 1.4 https://www.rcf.it/en_US/products/product-detail/nd950-1-4/292823

There is one other option that is looking fantastic - https://www.bcspeakers.com/en/products/coaxials-hf/1-4/16/DCX464-12
This new driver looks like it may even surpass the BMS in terms of output and sound quality, and hopefully at the normally sensible B&C price. Make sure you check its clearance especially with the 60 degree version.


DCX464 00 etc2.jpeg


12” Mids
B&C 12NDL76 - https://bcspeakers.com/en/products/lf-driver/12-0/8/12ndl76
 
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I have my own personal biamp tunings for a Lake LM44 (90deg) and iTechHD(60deg), as well as Tri-amp tuning for an HD(60 deg). I used FIR designer for raw coefficients on the HD and I should be able to help convert between those as needed. I also have access to BSS processors if someone wanted to use those.






 
Hi Peter, great call to start another thread specifically on these topics!

I know you did cover this in the other threads but would you mind giving another run down on the equipment and process's you use and go through to make a filter/filters for these box's. I am nearly finished my box's and will embark on this journey then. I have virtually zero experiance at doing this so to know where i should perhaps be trying to go will be invaluable for me I am sure.

Perhaps also this is a great time/place for you to repeat suggested crossover points and basic suggested peq settings.

Again thanks for the great design and other knowedge you share, your a top bloke thats also for sure!
 
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I'd be very curious to hear your process as well. I've been doing an intensive process of creating settings for a new B&C 14" coax driver by doing transfer function measurements and flattening the curve based on that, listing to music playback and finally doing the time honored shouting at it with an SM58. I've simply been redoing the process from the beginning several times to be sure I'm not getting too far down a rabbit hole with extreme processor settings and comparing to speakers that I already have settings for. I also compare between my standard monitor racks loaded with Ashly 4.24c processors and Lab Gruppen IPD amps with their own ( not Lake ) processing.

Jim dee said:
... would you mind giving another run down on the equipment and process's you use and go through to make a filter/filters for these box's. ...
Click to expand...
 
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A couple of comments about the PM90/60 design
  • The PM90/60 is designed to be pole mounted and produce extreme SPL and sound quality – as such there are some compromises; its complicated to build and process and the drivers are expensive.
  • Its only designed to be used above 100Hz.
  • All the drivers (MF, HF & VHF) operate in their piston range
  • Because of the bent mid horn, the mids should not operate above about 750Hz
  • The mids are not designed to be flat without significant DSP correction.
  • Because the 12” drivers are operating in their piston range you can correct their response with a DSP and they will still sound good.
  • The choice of the BMS4594 other than sound quality was its ability to operate at the very low crossover frequency needed. This is what limits the number of other suitable compression drivers and horns.
 
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Peter i hope all is swimmingly good for you(y),
You made mention of the B&C 12NDL76 & the 2NDL88 in the design thread, the latter for a bit more power handling.
do you think it would handle as well at the top & bottom end as well as the 76 or others.
in general i was wondering what the differnces would be for all the compromises(genaral spl,sound quality, upper-lower limit)
It must be a real pain having such a design compromised by others, however i'm sure that those that do only intend to do so till funding allows perfection:(. of cause the spare drivers will come in handy for other projects & imediate spares in case of disaster.
rather than killing you to answer all that in one go i'll pick the 12" Driver differences as my question including the fitted choice you made and leave space for other to chime in.
ps no mad hurry sir.
 
These drivers all look good -

- RCF MB12N301 & MB12N351

- B&C 12NDL76

- FaitalPro 12FH500 & 520

- Eighteen Sound 12ND830


B&C 12NDL88 is an excellent driver but T/S parameter are not ideal for this box, but it should work.

You need a driver that is suited for horn loading (in this box). Typically it needs a high BL product and relatively low moving mass. It must also have sufficent Xmax to be able to produce full SPL with a nominal crossover point of 100Hz.

If you choose a driver that is designed for bass applications the response will typically have large peaks and troughs in this horn.

Newer drivers designed with FEA optimized magnetic circuits, demodulating ring(s) to reduce distortion, optimized non-linear behaviour etc. will be better.

Here is an example of the tests and measurement that you can do - https://www.audioxpress.com/article/test-bench-b-c-speakers-21ds115-21-inch-woofer (an excellent B&C 21" bass driver)
 
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You can use 3 over 6 if your application requires the wide coverage that 3x60 or 3x90 degrees (depending on which horn you installed)gives you.
Don't make the mistake of thinking you can point all 3 in the same direction and get 3x the volume of one box however - sound unfortunately doesn't add up like that.
Comb filtering (AKA destructive interference) will mean the net gain above a few hundred Hz is much less than that, and there would be a significant loss of clarity and consistency of frequency response across the coverage pattern too.
 
Because overlapping the coverage of the horns will lead to comb filtering, which takes away from your clarity & coherence, so yes, Roger's pretty much right.
Realistically, there will be a little bit of wiggle room around that ideal splay angle where any negative effects are not too bad, but it won't be a big margin.
 
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