New DIY Mid High (90deg) - AKA PM90

[Peter Morris]

Stef, I can bring you in contact with Christian (from Germany) if you like. Christian built the PM90 with the ND950. Send me a PM.

I think Peter Morris used the 12NW76 (or was it the 12NDL76?) in one of his builds, but he liked the RCF more.


Sent from my iPhone

I used the 12NDL76 in my 60 degree boxes, its a little difficult to compare as my 60 degree boxes have a slightly longer mid horn than the original PM90's. This was to accommodate the extra length of the XT1464 horn compared to the HF950.

The longer mid horn in the PM60s works slightly better but I suspect the RCF is a slightly better driver in this application.

 

[Peter Morris]

Does anybody have any experience with the RCF ND950 1.4 compression driver?
I've read an article about a German company that build the PM90 with the ND950.
I also thought RCF used the ND950 in the newer ART745A from 650 Hz and up.
I'm aware that the ND950 can be fully used from 800 Hz, but I am curious of it will go a bit lower.

Also would the B&C 12NW76 be suited driver for the low/mid?

Thanks for any info!

AFAIK, RCF use the HF950 horn in their new TT5A and TT2A. The TT5A uses the ND950 compression driver and the TT2A uses ND850.

The TT5A crossover is 650Hz, the TT2a is 750Hz.

The ART745A uses the ND940.

I own some TT2A's and they are excellent, very natural sounding. When you compare these to the PM90 using the BMS4594HE you immediately notice how pristine the PM90's VHF is compared to the RCF. The PM90s sound noticeably better. It would be interesting to compare how the two compare at high SPL levels in the field.

http://www.audioxpress.com/article/Test-Bench-RCF-ND950-Neodymium-Compression-Driver-and-HF950-Horn

 

[Stef Smits]

Thanks for the reply!

I think I'm going to sell the B&C's and buy some RCF's for the low/mid section.

I'm very curious how the ND950 will perform in de PM90.

 

[Peter Morris]

Thanks for the reply!

I think I'm going to sell the B&C's and buy some RCF's for the low/mid section.

I'm very curious how the ND950 will perform in de PM90.

I think you will find only a very small difference between the B&C and RCF 12" drivers. I'm not sure you will notice much of a difference.

Also if you try the ND950 its diameter is slightly bigger - 146mm Vs 133mm, so make sure it will still fit.

 

[Stef Smits]

The B&C driver I have is the 12nw76 not the 12ndl76.
The nw has a higher xmax (8mm) and a bit lower qts value.

I also had a reply from Christian who build the pm90 with the nd950. De rcf was up for the job and was able to play from 600 Hz. I think I will cross it a bit higher, just to ve safe.

 

[Peter Morris]

The B&C driver I have is the 12nw76 not the 12ndl76.
The nw has a higher xmax (8mm) and a bit lower qts value.

I also had a reply from Christian who build the pm90 with the nd950. De rcf was up for the job and was able to play from 600 Hz. I think I will cross it a bit higher, just to ve safe.

I think 600 Hz is getting a bit low for that driver on the HF950 horn ... The HF950 has a cut off frequency of 400Hz and you are getting close. I do not have any figures on the acoustic impedance of the horn, but I suspect RCF knows exactly whats appropriate and they cross that driver & horn at 650Hz in the TT5A.

The 12NW76 will work but the response is getting a bit too uneven on the sim ... you could try it.

 

[Stef Smits]

I'm going to play safe, and buy some MB12N351's.

Ps: the ND950 will fit in the original plan.
Are there any descent schematic's available?

 

[Jim dee]

Are there any descent schematic's available?

Something I had wondered as well, if you read back though the thread somebody was working on accurate plans, in any case I know Peter has also earlier in the thread given pretty good info to where certain panels come together in the box and there distant from external walls etc. Shouldn't be too hard to piece it all together from those details if one must.

 

[Max Warasila]

Something I had wondered as well, if you read back though the thread somebody was working on accurate plans, in any case I know Peter has also earlier in the thread given pretty good info to where certain panels come together in the box and there distant from external walls etc. Shouldn't be too hard to piece it all together from those details if one must.

Still working on a good set of drawings for the 60deg version. I have most of it drawn, but not a published pdf yet. There's no reason to change them for the 90deg version unless you desperately need 1kg less weight per box. For the record - there's no good way to build the back corners without some excellent and very expensive CNC, Peter's method of cutting it off after the fact remains the best way I've found.

 

[Andy Turner]

Been doing some measurements with my new Audiometica Clio Pocket set, and did some intense listen and measuring at different levels in a very big room.
I came to the conclusion that I got a better result moving the microphone around to different listening positions in the room to hunt those 'nasty' frequencies that doesn't show at on-axis 1 meter distance measurements.
Peaks was gently pulled down as discovered, resulting in quite a few eq's :0)

I have done two teatre jobs and a demo with 12x18" Bandpass with 20Kw amps and the output was crazy :0) Only signal lamps on my amps was lighting up. The headroom is enormous.
One of the very good things about this box is it's long throw properties without loosing low mid substance. Voices, toms and snare keep sounding 'full' at greater distances.

If you like, I will share the export (OQP) file from Powersoft. Could be fun to compare ;0)

Enclosed is an example of my method: (MH90_freq_resp_red is raw. Green is after eq. Yellow is 25degr 2m. Black is 25degr 4m after eq) The final measurment is not included thus not corresponding to the eq settings further down in this post.



" location w/o front foam.

 

[Bennett Prescott]

I think 600 Hz is getting a bit low for that driver on the HF950 horn ... The HF950 has a cut off frequency of 400Hz and you are getting close. I do not have any figures on the acoustic impedance of the horn, but I suspect RCF knows exactly whats appropriate and they cross that driver & horn at 650Hz in the TT5A.

If you need a lower cutoff you could always try our new DE1090TN, a 4" diaphragm on a 1.4" throat - also not expensive or heavy.

http://www.bcspeakers.com/products/hf-driver/1-4/8/de1090tn

 

[Peter Morris]

If you need a lower cutoff you could always try our new DE1090TN, a 4" diaphragm on a 1.4" throat - also not expensive or heavy.

http://www.bcspeakers.com/products/hf-driver/1-4/8/de1090tn

Hi Bennett,

The DE1090TN looks very interesting and I would love to try some. In this case the cut-off frequency I was referring to was the horn flare.

FWIW I'm crossing my 90 degree boxes at 700Hz and the 60 degree boxes at 650Hz.

 

[Stef Smits]

Does anybody have some experience with the BMS 2230? Somebody offered me a pair of BMS 4592 drivers.
They would do the job, but there are not many suitable horns.

The 2230 can be used down to 700 Hz so it would be on the edge..

 

[Peter van Gils]

Does anybody have some experience with the BMS 2230? Somebody offered me a pair of BMS 4592 drivers.
They would do the job, but there are not many suitable horns.

The 2230 can be used down to 700 Hz so it would be on the edge..

The BMS 2230 horn is too short / cut off frequency too high. You want to have the cut off frequency almost factor 2 lower than the x-over frequency. The RCF HF950 has a cut off of 400 Hz and is already falling off several dB at 700 Hz. The 12" horn can't go higher, so for this design you need a long HF horn... I only know 1.4" horns that are commercially available *and* fit (in) the DIY...


Sent from my iPhone

 

[Peter Morris]

The BMS 2230 horn is too short / cut off frequency too high. You want to have the cut off frequency almost factor 2 lower than the x-over frequency. The RCF HF950 has a cut off of 400 Hz and is already falling off several dB at 700 Hz. The 12" horn can't go higher, so for this design you need a long HF horn... I only know 1.4" horns that are commercially available *and* fit (in) the DIY...


Sent from my iPhone

Exactly – To keep the box size down the LF horn was folded with a mouth above and below the HF horn.

This impacted on the maximum operating frequency of the MF horn limiting it to around 700Hz. At high frequencies the bends would cause issues and the dipole exits would cause the vertical pattern to narrow too much and eventually some unwanted MF lobes would occur.

The problem was finding a horn and driver that would happily go that low and physically fit in a box that was small enough to be pole mounted.

This is one of the reasons the 4594 and HF950 were selected. I don’t know of any other commercially available horns or drivers that will work. Some of the new large format B&C, 18sound and RCF drivers may work but I have not tried them. In general the lowest recommended manufactures crossover frequency is around 800Hz for these drivers.

FWIW I cross my 90 degree boxes at 700Hz.

 

[Don J Davis]

Had a chance to use the 90 deg boxes yesterday at Camp Pendleton. Just a pleasure to use these. They are very responsive, get loud and don't distort.
There were more people in attendance than they originally told us but the coverage was still good. It was a fun day serving our Marines.

 

[Boyd Williamson]

I had an idea for this box that I thought might be of interest... seeing as this is a symmetrical design, it occurred to me that both ends of the cab could have 'top-hat' speaker pole mounts, one of which could be a custom job with a say, 7 deg downward tilt, and be mounted further forward to maintain the C.o.G.

I've encountered the down tilting capability on a few commercial speakers now, and in certain rooms & situations I quite like it. Having the flexibility to do so by flipping the box seems kind of neat to me. I considered if they could both be on the bottom of the cab, but figured it might obstruct the braces too much.

Sadly it seems a 'spec' pair of these cabs might be a while off for me yet. So, in the spirit of D.I.Y. I'm considering having a crack at a test box with a pair of Eminence 3012HO's I have on hand, and a Radian 745NEOPB (which will 'supposedly' handle a 500Hz xover @ -24db/oct, or 900Hz @ -12db/oct) Hopefully this will work ok at ~700Hz -24db/oct in practice. Any idea on how well the 3012HO might work in the midbass horn section?

It might seem like sacrilege, but at the moment I don't 'need' the ultimate in performance for what I'm doing, so any improvement over my current D.I.Y. cabs, and I'm winning ~~:smile:

 

[Peter Morris]

I had an idea for this box that I thought might be of interest... seeing as this is a symmetrical design, it occurred to me that both ends of the cab could have 'top-hat' speaker pole mounts, one of which could be a custom job with a say, 7 deg downward tilt, and be mounted further forward to maintain the C.o.G.

I've encountered the down tilting capability on a few commercial speakers now, and in certain rooms & situations I quite like it. Having the flexibility to do so by flipping the box seems kind of neat to me. I considered if they could both be on the bottom of the cab, but figured it might obstruct the braces too much.

Sadly it seems a 'spec' pair of these cabs might be a while off for me yet. So, in the spirit of D.I.Y. I'm considering having a crack at a test box with a pair of Eminence 3012HO's I have on hand, and a Radian 745NEOPB (which will 'supposedly' handle a 500Hz xover @ -24db/oct, or 900Hz @ -12db/oct) Hopefully this will work ok at ~700Hz -24db/oct in practice. Any idea on how well the 3012HO might work in the midbass horn section?

It might seem like sacrilege, but at the moment I don't 'need' the ultimate in performance for what I'm doing, so any improvement over my current D.I.Y. cabs, and I'm winning ~~:smile:

The 3012HO would work but I don’t think it would be a good choice, its BL product is too low and there is a resonant peak in the DIY when I modelled it with the 3012 around 90Hz that may cause some problems.

The best cost effect solution is the B&C 12NDL76. I don’t think the 745NEOBP will have enough output to keep up with the mids when crossed at 700Hz – the 951 may be an option as would be B&C’s new DE1090TN … an excellent looking driver.

http://www.audioxpress.com/article/t...ression-driver

http://www.usspeaker.com/B&C-DE1090tn-1.htm

I like you idea with the top hat - interesting ~:-o~, the only thing to note is the box will weigh around 35kgs and you will need a very heavy duty pole mount / top hat https://www.parts-express.com/penn-e...stand--245-019

 

[Andy Turner]

Would anyone be interested in buying a pair of these boxes?


Drivers are:
BMS 4594HE with passive filter and RCF MB12N351

Pole-mount
Painted with Black Tuff Cab Pro
Speakon 4

Used once for theatre with Powersoft K dsp.

Asking price is 2500 euro + shipping. Negotiable :0)

Powersoft K6 and K8 can be included.

 

[Chris Michael]

Hi Peter
I was about to build an SMT 212, When I came along this great design. I have some Beyma 12p80nd-v2 that was meant for the SMT 212, but I am convinced that your design is much better so I wonder if the 12p80nd-v2 is usable in your design?