Cone midrange horn 101

I've been reading a fair amount but still can't quite get my head around it. JBL CMCD-81 was suggested to me and after reading everything I could find about it I'm now interested. Maybe more so on a CMCD-61. These, however, seem to be quite difficult to source and almost not used by hi-fi enthusiasts...so makes me wonder.

My understanding so far is 2" compression drivers have the great advantage of going up high in the treble (which I don't need), but might sound thin in the 300-500Hz region (which I do need).

Since I'm looking at 350/450 to 2500Hz for the midrange driver I'm wondering if a cone midrange horn might work. Maybe I don't need a phase plug to get to 2500Hz cleanly? What are the cone driver parameters that make it ideal for horn loading?

FWIW, it's an active system with digital crossovers and room correction. The tweeter is a Beyma TPL-150H. I was thinking of a 300Hz Tractrix or a Yuichi-type horn to try and reduce center-to-center distance to the tweeter.

Thank you!
 
Unfortunately, reducing the height of a mid horn introduces "pattern flip", the vertical dispersion becomes wider than the horizontal.

The advantage of a compression driver going high also comes with the disadvantage of reduced excursion of less than 1mm, which limits low frequency operation (350 Hz) to a fairly low level before high levels of distortion (or the nasty sound of the diaphragm hitting the phase plug) become objectionable.

Cone midrange eliminate the excursion problem dictated by the phase plug, and by using small cone drivers clean response from 250Hz to the limits of audibility are possible at very low distortion with no phase plug required.

The parameters for an "ideal" cone driver would be dependent on the horn type, cost you can afford, bandwidth, dispersion and SPL desired- there is no "one size fits all", though the 3.5" Tymphony TC9FD-18-08 "full range" driver (about $12) sounds amazingly good on the various horns I have tried it on. Having the ability to cover from 250 Hz to 16kHz cleanly from a single driver eliminates the center to center distance problems associated with a typical multiple horn set up.

The horizontal polar response of a TC9 on a 45 x 30 two part conical horn below is with no EQ applied, less than 6 dB of correction would be required to flatten it from 250 to 16kHz. The curves are at 5 degree increments, note the constant directivity with frequency- the horn sounds the same over it's intended coverage pattern.
The prototype horn was constructed in less than an hour from cardboard and tape (a plastic jug for the back chamber, I'd expect even better results with more attention to detail.
More details in post #860 here:
http://www.diyaudio.com/forums/multi-way/285030-bookshelf-multi-way-point-source-horn-86.html

Art
 

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Thanks. Please note I still want to use the TPL tweeter, so no need to play cleanly above 4kHz (steep xo @ 2.5kHz).

I realize the driver and the horn need to work well together. Maybe it's better to ask for good examples of midrange cone-driven horns for these frequencies? Maybe I can learn from those examples.

Budget is somewhat flexible. About U$300 per driver would be fine, maybe can stretch to 500 if it was really special. But there seem to be many good cone midranges under 300. Of course lower is better. Couldn't do U$1600 per driver I've come across for some BMS 2" midrange compression drivers :eek:

But at this point I'm more interested in learning about successful implementations of midrange cone-driven horns, with a keen interest on examples featuring lower height.
 
The TPL-150H is super efficient so you may need a pro mid cone like a PRV 5MR450-NDY or a Galaxy S5N just might be the ticket as they have high sensitivity and strong motors suited for horn loading. I have personally used the PRV and it will work cleanly up to 4.5k before experiencing fall-off which can be compensated with EQ. Both these drivers are well within your budget.

https://www.parts-express.com/galaxy-audio-s5n-8-5-neodymium-full-range-driver-8-ohm--290-020

https://www.parts-express.com/prv-audio-5mr450-ndy-5-midrange-neodymium-woofer-8-ohm--294-2705

Here is the 5MR450 in a 175Hz Bruce Edgar style tractrix (with EQ):

434944d1408971865-prv-5mr450-ndy-fast-applications-tractrix-cld-new-eq.png
 
I'm asking myself if Lewinski01 could have a look to a synergy design as he has already 2 x 10" drivers per speaker ! Beyma at the apex, lobying directivity solved as all is firering in the same wave guide ? Why not a 60x60° synergy wave guide ! (if the H horn of the TPLH is not keeped)

Also choice of the mids between the 10"s and the TPLH150 should be easilier ! c to c with fire port near in the wave guide near the apex.

Big + : he is active and can solve time domain and has already multi amp !

Just two cents !

Below 100 Hz not covered by the synergy design if the size stays "homable", multi little sub can solve room modes ! Hop voila, tout le monde happy ?!:) (everybody content !)
 
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JBL CMCD/PT or 2485

I've been reading a fair amount but still can't quite get my head around it. JBL CMCD-81 was suggested to me and after reading everything I could find about it I'm now interested. Maybe more so on a CMCD-61. These, however, seem to be quite difficult to source and almost not used by hi-fi enthusiasts...so makes me wonder.

My understanding so far is 2" compression drivers have the great advantage of going up high in the treble (which I don't need), but might sound thin in the 300-500Hz region (which I do need).

Since I'm looking at 350/450 to 2500Hz for the midrange driver I'm wondering if a cone midrange horn might work. Maybe I don't need a phase plug to get to 2500Hz cleanly? What are the cone driver parameters that make it ideal for horn loading?

FWIW, it's an active system with digital crossovers and room correction. The tweeter is a Beyma TPL-150H. I was thinking of a 300Hz Tractrix or a Yuichi-type horn to try and reduce center-to-center distance to the tweeter.

Thank you!

Study this.
https://www.jblpro.com/ProductAttachments/tn_v1n31.pdf
Note you will need to design/build a phase plug as well unless you use a compression driver with one already built-in.
For a KISS alternative, I would use the JBL 2485 for this application.
https://www.jblpro.com/pages/pub/components/2485.pdf
The horn needs to be big! See for example.
KPT - Jubilee® | Klipsch
Regards,
WHG
 
There is also the possibility of the tweeter not in the Apex of thr trhoat but further in the horn as you can deal with time delay.

Assuming matching the directivity lobbying between horn & drivers is staying one of the main problem :

Like xrk971 : you put a 3" to 4" cone driver at the Apex : less distorsion than a CD driver , more linearity (I speak Under the control of x here ?)

This apex driver solve the medium behavior between the Beyma and your two 10" per synergy (Trynergy) cabinet. I think to the ScanSpeak 10F/84G2400; xrk971 had 100 Db from this little gem (I purchased myself two of it:))... bingo, near the efficienty of the Beyma !

Should it be then possible to put the Beyma further in the horn at the front of the Apex/mid driver (after all we don't need more than 2500 K or less from the ScanSpeak) on a rod which can move to adjust a little the directivity of it in the waveguide (firering not directly for high efficienty treble is good most of the time to avoid also a too much hifi sound: on a rod, you can tilt on/off the TP150 to play on the radiation behavior into the horn/wave guide)? Of course you need FIR correction because tweeter is in front of the mid ! It' even possible with suffisant delay to put this rod at the mouth of the horn/wave guide : radiation of the Beyma is not made into the horn anymore (but here you need to match the lobyings off axis : Dangerous path again !
Basicly a Synergy is the horn you talk about in your first post but with firing ports into it for mid-bass range to image better than multiple horns! Kees member did it in his Trynergy with K-shape...
 
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Since I'm looking at 350/450 to 2500Hz for the midrange driver I'm wondering if a cone midrange horn might work.

I also have been searching for a high efficiency midrange to pair with TPL-150, and will try this before diving into midrange horn territory (or not when it turns out to work well enough):

CAM00083.jpg

This combination will have some 97 dB efficiency from 300 Hz upwards, and crossover to the TPL-150 will be around 1900 Hz to prevent the midrange from beaming.
Very short waveguide for the TPL-150 for vertical alignment with the midrange.
Sorry for the 90 degrees rotation.
 
xrk, what do you think of my scenario ? Possible according to you ? maybe more with a TC9 if a 350/400 low XO is looked for ?

The lesser mvt of a 3/4" driver in a trynergy wimm match better the low distorsion of the AMT and its subjective fastness...

Too bad there are no PR17Zo from Audax, maybe this one could match in direct radiation on a front bafle very well with the Beyma !
 
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and in the midle of the horn as it's pulsed air, AMT efficienty should not be increased maybe ?

The thing which is puzzled me here is : any thing in front of a driver (here in front of the SscanSpeak at the Apex) should act as a low pass passive filter... It can perhaps be solved by choosing in the depth of the horn the right distance between the cone at Apex and the AMT in front of it in the horn/wave guide ! Measurements needed !

Two rods in the vertical sense could not to hard to drill with a Beyma in the midle in suspension in the middle of the horn not touching the walls !

P. solution with the Audax should be easier... but maybe in theory has not the advantage of the synergy point source design...

We reviewed tons of 6" to 8" driver for the Beyma... Some good candidates... as Linesource member showed in many scenario WMT...

It's not so easy to start from a high efficienty treble AMT to design a speaker : good challenge !
 
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back on topic : cone loaded mid range horn

If I did not already have the drivers I do (PR 170zo), I would seriously consider these (listed below). At first glance it seems the response is tilted, BUT, that is exactly what we want for horn loading. A proper horn will "lift" the lower range of the response, AND with a larger throat, will decrease the load as the frequency inclines, thus smoothing the response. I would also be VERY tempted to run this mid range up much higher than 2.0 or 2.5K. The reason being, to insure MOST of the fundamentals AND associated harmonics emanate from as close to a point source as possible. Realizing it can be considered counter-intuitive, but as the crossover frequency increases, it's effects and localization actually diminishes and becomes less of a distraction.

High efficiency 6" cone midrange, ideally suited for three and
four way systems. Very smooth response from 400 Hz to 8 kHz.
An aluminum phase plug increases axial sensitivity and
controls high frequency dispersion.


p.s. If pattern flip is of a concern, then simply opt for the square mouth version of the Edgar- Tractrix
(but personally, I would choose the rectangular aspect ratio)

http://www.parts-express.com/pedocs/specs/294-650-bc-speakers-6pev13-specifications-44875.pdf
 
The TPL-150H is super efficient so you may need a pro mid cone like a PRV 5MR450-NDY or a Galaxy S5N just might be the ticket as they have high sensitivity and strong motors suited for horn loading. I have personally used the PRV and it will work cleanly up to 4.5k before experiencing fall-off which can be compensated with EQ. Both these drivers are well within your budget.

https://www.parts-express.com/galaxy-audio-s5n-8-5-neodymium-full-range-driver-8-ohm--290-020

https://www.parts-express.com/prv-audio-5mr450-ndy-5-midrange-neodymium-woofer-8-ohm--294-2705

Here is the 5MR450 in a 175Hz Bruce Edgar style tractrix (with EQ):

434944d1408971865-prv-5mr450-ndy-fast-applications-tractrix-cld-new-eq.png

Thanks all for the very constructive feedback. It's taking me a while to read, digest and come back. But it's being fruitful!



Xrk,

This is very helpful!

What's a rule of thumb to use as far as sensitivity increase when horn loading? What's the sensitivity in your graph from 300 to 3000Hz with the Edgar tractrix? Harmonics level seem to be super low. Nice!

The PRV data is a bit confusing as they publish frequency response measured at 2.0V at 1m (as opposed to 2.83V), and they don't seem to publish a sensitivity figure. At 2V sensitivity seems to be around 93dB in the 300 to 3000 Hz range.


Also, when you say "strong motors", is it appropriate to use motor strength = Bl^2/Re?
PHLs typically have high Bl^2/Re, although they have high Le (0.5 to 0.6 mH). This PRV has VERY low Le of 0.02 mH. How important is low Le for horn loading?
 
I'm asking myself if Lewinski01 could have a look to a synergy design as he has already 2 x 10" drivers per speaker ! Beyma at the apex, lobying directivity solved as all is firering in the same wave guide ? Why not a 60x60° synergy wave guide ! (if the H horn of the TPLH is not keeped)

Also choice of the mids between the 10"s and the TPLH150 should be easilier ! c to c with fire port near in the wave guide near the apex.

Big + : he is active and can solve time domain and has already multi amp !

Just two cents !

Below 100 Hz not covered by the synergy design if the size stays "homable", multi little sub can solve room modes ! Hop voila, tout le monde happy ?!:) (everybody content !)

Hello Eldam.

Honestly, I'm not tempted to go down that path. The two 10" I have are bass drivers, so I would need to buy 2 midranges to fit the Synergy concept to experiment. Not clear what the benefit of that would be vs. experimenting with direct radiators and horns in a 4-way system. At least for the time being. I'm not experienced enough to attempt a cutting edge design...that should be left to more experienced folks - or folks with more disposable time. Busy working schedule and 3-kids don't leave much time to work on audio.

cheers
 
Study this.
https://www.jblpro.com/ProductAttachments/tn_v1n31.pdf
Note you will need to design/build a phase plug as well unless you use a compression driver with one already built-in.
For a KISS alternative, I would use the JBL 2485 for this application.
https://www.jblpro.com/pages/pub/components/2485.pdf
The horn needs to be big! See for example.
KPT - Jubilee® | Klipsch
Regards,
WHG

Thanks for the links!
I had actually seen the first one (JBL PT guides), and also the one on CMCD drivers. The 2485 looks interesting, although my search suggests it's a vintage product apparently not being sold anymore. So as challenging, if not more, as finding a CMCD-61. Plus the 2485 spec shows it coupled to a 2366 horn, which is huge:eek: Not living-room friendly! The sensitivity is outstanding, though. Would love that with a 45-SET.

Is there a place where I can buy 2485 that you know of? And how well would they work well with a different type horn, hopefully smaller? Don't need 118dB...105 would suffice:D
 
I also have been searching for a high efficiency midrange to pair with TPL-150, and will try this before diving into midrange horn territory (or not when it turns out to work well enough):

View attachment 532328

This combination will have some 97 dB efficiency from 300 Hz upwards, and crossover to the TPL-150 will be around 1900 Hz to prevent the midrange from beaming.
Very short waveguide for the TPL-150 for vertical alignment with the midrange.
Sorry for the 90 degrees rotation.

Hello Pieter.

Yes, I'm considering direct radiators as well. So far my leading candidates are 8-inchers: PHL 2540, B&C 8PE21, AE TD8M, and HM210Z10. Their sensitivities go from 95 (AE) to 99dB (PHL). These pose challenges in the center-to-center department (to a TPL) and might start beaming at 2kHz (which is why I'm refraining from 10" midranges).

I'm also considering 6.5" midranges, which are a good match as far as beaming goes and reduce some the c-to-c issue, but I'm afraid to have an unbalanced system in terms of dynamics (which the TPL are known for). My B&W speakers have FST midranges, and these are outstanding drivers, so I'm likely to try this before dumping the idea of 6.5" direct radiators.

But if I were to drop 6.5" and then live with the c-to-c compromise...I might as well go to a midrange CD horn and be done with beaming concerns and sensitivity limitations. Hence this thread :)