New DIY Mid High (90deg) - AKA PM90

Ethan Greaves

New member
Jan 7, 2021
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Brisbane
Hey all - can anyone advise if the DCX464 will fit with RCF MB12N351's ? Does it require a spacer on the front (i.e. where the HF950 joins in order to pull it forward away from 12's internally). The RCF MB351's have +5mm on the outer diameter but 280 (vs. 283mm) on the internal mounting diameter so maybe it will just work ?
 
Oct 25, 2018
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Bideford, Devon. UK
I'd be up for a flat pack kit if you've figured out your CNC yet?!
Hi Miles, thank you for your interest. It is up and running sufficiently well for my wife's non-critical profiling, however I need to improve the stiffness of the machine before offering subcontract/flatpack work. Whilst I was aware it had been DIY-built on a budget, I had not appreciated that it was a desktop design scaled up to half-sheet size with no conception of rigidity requirements. Deflection in the X-axis by thumb pressure is several millimetres... I have most of the materials and a water cooled HF spindle to rectify this, but other essential jobs which have come along means it won't be rebuilt to the accuracy I require for many months. Sorry to disappoint, however I will be in touch when I can offer kits.
 

Max Warasila

Graduate
Feb 20, 2013
1,195
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48
Richmond, VA
Hi Miles, thank you for your interest. It is up and running sufficiently well for my wife's non-critical profiling, however I need to improve the stiffness of the machine before offering subcontract/flatpack work. Whilst I was aware it had been DIY-built on a budget, I had not appreciated that it was a desktop design scaled up to half-sheet size with no conception of rigidity requirements. Deflection in the X-axis by thumb pressure is several millimetres... I have most of the materials and a water cooled HF spindle to rectify this, but other essential jobs which have come along means it won't be rebuilt to the accuracy I require for many months. Sorry to disappoint, however I will be in touch when I can offer kits.
It's always one axis which has a slipping problem or excessive deflection. On our old one it was Z axis deflection, so you wouldn't get straight vertical plunges.
 
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Miles Harrison

New member
Feb 17, 2021
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uk
Thanks Carl, I do have a local CNC company that I have used before so I may approach them again. But would rather use a forum member. Am I correct in thinking that if I send them the .DWG file from this thread that they will have everything they need in there? (I'm ok with woodworking but not the computer file side of things!)
Hope you get the machine sorted soon!
 

Jim dee

Freshman
Jul 12, 2015
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New Zealand.
where can i find the complete plans for this speaker? I would like to build a pair but i can't seem to locate the plans. thanks
The search function found me a link in the threads to a drop box link of the plans i used to build mine, it took 60 seconds from hitting enter to viewing the plans. The only thing to note is that you may need to stretch the design just slightly to fit teh B&C coaxial(between teh mid dirvers) instead of the BMS coaxial the design was designed for(both drivers work fine), i think this just applies when using the 60 degree horn though I cant remember exactly. Good Luck.

https://www.dropbox.com/s/h16is6mbjig6fcy/pm90_current.pdf?dl=0
https://www.dropbox.com/s/8vvhnwc5x73eos1/pm90_current.dwg?dl=0

Theres is one other thing worth mentioning. The pole mount location is not centered as far as weight is concerned, there is more weight behind the pole mount so this may be something you will need to adjust if you intend to use a pole mount.
 

ross johnson

New member
Mar 21, 2021
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louisiana
thanks so much for finding the plans. I kept searching and getting lost reading more threads but never finding the plans.

I'm looking to make the 90 degree versions to use with Keystone subs. didn't know which speakers and horns were proven to be best but I'll search and read more to find out.
 

ross johnson

New member
Mar 21, 2021
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louisiana
just priced the speakers and horn driver and I think this is out of my price range. lol. looking at other options for now but I will circle back here in the future.
 

Stef Smits

Freshman
Apr 4, 2017
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just priced the speakers and horn driver and I think this is out of my price range. lol. looking at other options for now but I will circle back here in the future.
You could go for a cheaper HF driver. DE1090Tn and ND950 1.4. Would also do the job, at the cost of some soundquality against the BMS/B&C coax.
 

sal mirabile

Freshman
May 8, 2013
23
12
3
haven't been in here for a while. it's good to see this thread is still very much alive.
2020 was a ridiculously tough year and as a result, haven't finished the PM60s i built last year. I've still got the ND950 drivers and subs to buy to finish them off. hopefully this summer will be a good one for sure!

what DSP are you guys using? Was thinking of freeDSP Aurora...any thoughts on this unit?
 

Art Welter

Senior
Jan 11, 2011
838
23
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Florida
would it do the cabinet any justice going with eminence speakers to reduce the cost?
Peter's design uses the 12" in their piston range, crossing over at 630 Hz. That low of a crossover requires a co-ax mid/hi driver to "keep up" with the output the dual 12" are capable of.
Eminence does not make a co-ax mid/hi driver. Using their 1.4" 3" diaphragm HF drivers would work in the design, but would run into excursion limits (diaphragm hammering the phase plug) at a SPL well below the output capability of the 12" drivers.
If the crossover frequency were raised to around 1200 Hz, a standard 3" diaphragm HF driver's output could potentially "keep up" to the 12", but the 12" would be required to operate almost an octave above where they sound the best.

Bottom line- reduced SPL, or reduced sound quality.

Art
 
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Stef Smits

Freshman
Apr 4, 2017
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All eminence options are definately not optimal. The one thing that could come close to working in the PM60/90 is probably their new N314X HF driver (I'm also curious about that one, but its so damn expensive in the EU). They claim a 800Hz possible crossover like various other offerings that do work in the PM60/90 (ND950 and DE1090TN).
 

Roland Clarke

New member
Feb 22, 2018
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Hastings
Peter originally used Dolby lake, but I believe he now uses the Linear Research ASC 48, or the amp equivelent. I have mine run on the Linear Research, 48M20. The obvious benefits are these all include FIR filters. You could do much the same with powersoft and their Armonia software. Various other companies offer fir filter options. These will allow to to achieve not only a good tailored response probably around +/- 1.5db, but also linear phase response, which most people find subjectively, better.
 
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Stef Smits

Freshman
Apr 4, 2017
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Note that don't necessarely need FIR. You can get decent results with IIR also (that even means you can get it to work with a dcx). Though, FIR filtering will give you that extra which can make a box just that bit better then most others.