Matching horns to compression drivers, a discussion

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#221
kevinkr said:
I think Earl has nailed it. When I have some time I will pull one of them out of my storage cabinet and take a good picture, but I believe mine have the step as shown.
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Unfortunately I gave them away fairly recently and failed to photograph them, but yes the step shown is present in mine. I've already forgotten who got them and am strangely undisturbed by the fact. 😀
 
#222
oltos said:
Question: Is the 16 ohm DCM50 really not a 4” diaphragm?
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It's a 5" paper diaphragm.2" exit.
WIth a 2" Voice coil.


Unlike traditional compression drivers/ domes.
It is "driven' from the center, Voice coil is in the middle like a normal cone driver. With a half roll surround termination on the circumference like a normal cone driver/woofer.

So it's construction is quite a bit different then a standard 4" /2" compression driver.
 

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#224
Arez said:
It's a 5" paper diaphragm with 2" exit. WIth a 2" Voice coil.

Unlike traditional compression drivers/ domes. It is "driven' from the center, Voice coil is in the middle like a normal cone driver. With a half roll surround termination on the circumference like a normal cone driver/woofer.

So it's construction is quite a bit different then a standard 4" /2" compression driver.
Click to expand...
Strange that the DCM50’s 5” diaphragm is even an inch larger than the Radian 950 and JBL 2450J, and still I wasn't especially as impressed as I thought I would be by the size of its sound I heard it in this system last month. https://josephcrowe.com/products/speaker-system-no-2095

However, Troy recently emailed me about changes he's made to the DCM50 ; see 3:25 to 4:11.


That speaker uses the same ES450 horn. Speaker System No.2800

But how likely would those “relaxed sound” upgrades do what the larger ES290/ # 1670 horn might? Would the only difference be in the size of the sweet spot or would it take the larger ES290 horn to create a more spacious sound due to a somewhat (?) lower directivity pattern, where more indirect sound (secondary reflections?) would be generated?

https://cdn.shopify.com/s/files/1/0..._Filled_Contour_Plot_480x480.png?v=1697218866

https://cdn.shopify.com/s/files/1/0...BMS_4591-8_off-axis3_480x480.png?v=1649504045

In any case, would that new rear enclosure Troy built for the DCM50 improve the expansiveness of it’s sound?

This relates to what I don’t understand when Troy and others claim about the advantages of large diaphragm drivers: “This large diaphragm driver provided excellent clarity across the frequency bandwidth along with world class dynamics, especially on male and female vocals, being able to project into a large listening space with shocking realism and affect.” Added italics.

https://www.rcf.it/en/products/product-detail/nd950-2.0

https://josephcrowe.com/blogs/news/bms-4591-with-horn-no-1670

https://www.bmsspeakers.com/fileadm..._4591_2011-04_midrange_compression_driver.pdf

Embarrassing ignorance again, but how can those larger diaphragm drivers perform in those respects any better than could this driver, also with a 2” throat but with a 3” diaphragm? https://www.usspeaker.com/radian 760neoBepb-1.htm . Am I wrong or is not hole in the horn in the center-on the side of the horn where the flare begins-way smaller than 5 or even 4”?

In any case, even in my less than large room (~ 2800 cu ft), at least as Earl Geddes would likely judge it, what subjective benefits might the 4 or 5” DCM50, RCF ND950 or BMS 4591 deliver that the Radian 745 or 760 berylliums won’t in the same Crowe ES450 or ES290 horn?
 
#225
oltos said:
Strange that the DCM50’s 5” diaphragm is even an inch larger than the Radian 950 and JBL 2450J, and still I wasn't especially as impressed as I thought I would be by the size of its sound I heard it in this system last month
Click to expand...
It's a midrange driver with a composite 5" diameter annular diaphragm with a 2"diameter voice coil, quite different from a 4" dome diaphragm designed to cover up to 20kHz.
oltos said:
In any case, would that new rear enclosure Troy built for the DCM50 improve the expansiveness of it’s sound?
Click to expand...
It would change the driver's resonant frequency and frequency response.
How one interprets those changes subjectively is an individual response.
 
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#226
oltos said:
Embarrassing ignorance again, but how can those larger diaphragm drivers perform in those respects any better than could this driver, also with a 2” throat but with a 3” diaphragm? https://www.usspeaker.com/radian 760neoBepb-1.htm . Am I wrong or is not hole in the horn in the center-on the side of the horn where the flare begins-way smaller than 5 or even 4”?
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The "phase plug" funnels the entire surface area into the 2" throat.

Having 4" diameter coils does seem a bit odd, and there are probably some technical challenges in preventing transverse waves from rippling across the dome and accumulating to a high amplitude in the middle.
 
#227
weltersys said:
quite different from a 4" dome diaphragm designed to cover up to 20kHz.
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When comparing the Radian 745Be/760Be (1.4"/2" throat, 3" diaphragm) to the 951Be/950Be (1.4"/2" throat, 4" diaphragm), I thought you said that while the 4" Radian Be has better lower midrange response and/or can be crossed lower the the 3" diaphragm Radian Bes, it couldn't get as close as the 3" can to 20kHz without distortion, regardless of filtering.
 
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#229
oltos said:
When comparing the Radian 745Be/760Be (1.4"/2" throat, 3" diaphragm) to the 951Be/950Be (1.4"/2" throat, 4" diaphragm), I thought you said that while the 4" Radian Be has better lower midrange response and/or can be crossed lower the the 3" diaphragm Radian Bes, it couldn't get as close as the 3" can to 20kHz without distortion, regardless of filtering.
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That is correct.

oltos said:
Finally, I know what that thing does? Does it serve any other functions?
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Maybe this will explain and visualize a bit better. Both what it does and some of the issues with them.

https://fohonline.com/articles/speaking-of-speakers/understanding-compression-drivers-phase-plugs/
 

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#230
oltos said:
I will be shipping a pair of these https://www.usspeaker.com/radian 745neoBepb-1.htm and possibly also these
https://www.usspeaker.com/radian 760neoBepb-1.htm to Troy Crowe to test in one of these horns.
https://josephcrowe.com/products/3d-cad-files-horn-no-1994-es450-biradial-for-jbl-2446-2-throat
https://josephcrowe.com/products/3d-cad-plans-for-es-290-biradial-horn-horn-no-1670

While browsing Troy’s speaker design blog looking for what he said that he suspected might be true of a driver with a 2” throat and 3” diaphragm (see the BMS 4591 review below), I found this otherwise review https://josephcrowe.com/blogs/news/b-c-dcx-464-16-with-es-600-biradial-horn which says “1.4" throat provides wider off-axis coverage in the upper treble than a 2" throat”.

This was precisely the concern I wanted to discuss with Arez, Weltersys, John Sheerin those here and finally Troy about: Both wide upper HF off-axis and lower MF off-axis coverage is likely harder to achieve in a two-way system. But would Troy’s statement only apply to the DCX464 because it's a coaxial driver?

Or would that statement also apply to most compression drivers, such as these, both with 3" diaphragms?
https://www.usspeaker.com/radian 745neoBepb-1.htm
https://www.usspeaker.com/radian 760neoBepb-1.htm

And if so, is the converse also true of 2” throat (3” diaphragm) drivers-that most such drivers provide wider off-axis coverage in the midrange than their 1.4” throat versions?

But when Troy reviewed this NON-coaxial midrange driver
https://www.bmsspeakers.com/fileadm..._4591_2011-04_midrange_compression_driver.pdf , he voiced the same suspicions about audibly different if unmeasurable (subjective) differences between 1.4” and 2” throat drivers. https://josephcrowe.com/blogs/news/bms-4591-with-horn-no-1670 , saying “This driver has the same sound characteristics as the B&C DCX-464 midrange section, which is exemplary, providing immense authority to vocals. There is zero hint of harshness as well. This driver could easily become the underpinning of a great system……….The BMS 4591 is also a true 2" driver where other drivers use an adapter from 1.4" to 2". Does this equate to better sound? I’m not sure. But if a system is going to have a dedicated mid-horn, why not stay with 2 inch?

In any case, can maximal horizontal and vertical off-axis coverage be realized across the usable bandwidth of the 3” diaphragm of these drivers? https://www.usspeaker.com/radian 745neoBepb-1.htm
https://www.usspeaker.com/radian 760neoBepb-1.htm

by selecting a larger version of the ES-600 horn, which was used for that review? https://josephcrowe.com/products/es-600-bi-radial-wood-horn-no-1978

And if that’s true then:

1/) How to decide between those two Radian drivers to select and implement the appropriate passive frequency contour filtering to flatten and extend the HF response consistent with inaudible distortion and maximal clarity for an ideal two-way system-as Pierre did with his Radian 745Bes. https://www.diyaudio.com/community/threads/beyond-the-ariel.100392/page-764

BUT Troy would have to agree to likewise, though according to Robh 3606 this is not hard to do using LEAP ( https://www.physical-lab.com/products/linearx/cae-software/leap ) or the like.

2/) Select between these two Crowe or other suggested horns, who says: My subjective assessment is in the context of medium size format horns such as the ES-600 Biradial. If we are having a general discussion about ultimate sound quality, then it needs to be pointed that a larger horn will provide a larger sense of scale and clarity, and in turn a more engaging listening experience. If we are talking cost-no-object ultimate sound quality then the ES-450 or ES-290 Biradial [with the TAD TD-4003] will provide those attributes mentioned.
https://josephcrowe.com/products/3d-cad-files-horn-no-1994-es450-biradial-for-jbl-2446-2-throat

https://josephcrowe.com/products/3d-cad-plans-for-es-290-biradial-horn-horn-no-1670

3/) BUT no use of throat adapters as I want zero chance of creating resonances or other artifacts.

As both the Crowe horns and Radian beryllium drivers are very costly this is why throat sizes I obviously need to avoid any simple sizing mistakes. So, the selected horn must either natively mate with the driver’s throat, or the horn must be custom made to do so

As I cannot make the trip to Ontario, my strategy is that if Troy isn’t seriously won over by what he hears from the EQed 1.4” or 2” Radian 3” diaphragm drivers, then the 16 ohm BMS 4591 2” throat 3.5” diaphragm midrange and what would likely be Troy’s recommended tweeter. https://josephcrowe.com/products/lens-no-1896-for-fostex-t96a?_pos=1&_psq=t96&_ss=e&_v=1.0
would be the other option.

Of course, for the sake of achieving a highly listenable two-way beryllium system I hope that doesn’t happen.

Question: Is the 16 ohm DCM50 really not a 4” diaphragm? https://usspeaker.com/B&C-DCM50-1.htm
Click to expand...

I feel for Troy...
 
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#232
oltos said:
When comparing the Radian 745Be/760Be (1.4"/2" throat, 3" diaphragm) to the 951Be/950Be (1.4"/2" throat, 4" diaphragm), I thought you said that while the 4" Radian Be has better lower midrange response and/or can be crossed lower the the 3" diaphragm Radian Bes, it couldn't get as close as the 3" can to 20kHz without distortion, regardless of filtering.
Click to expand...
No, I said a 4" (dome) diaphragm is capable of around +5dB more SPL due to it's greater displacement than a 3" (dome) diaphragm.
Louder does not mean better.
Filtering has no effect on distortion, unless the filters are used to push the driver beyond the SPL it can achieve with acceptable levels of distortion.
 
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#233
Arez said:
Maybe this will explain and visualize a bit better. Both what it does and some of the issues with them.

https://fohonline.com/articles/speaking-of-speakers/understanding-compression-drivers-phase-plugs/
Click to expand...
Thanks so much for citing that highly informative discussion. It clearly answered all question I imagined about phase plug design and performance, at least at my present knowledge level. Very enjoyable read. The rest of my education into speaker design, performance and room acoustics should go so smoothly and virtually effortless.

I was curious about the Radian phase (“phasing”) plugs, which for the 760NeoBe and 950 are said to utilize a "3-slit phase plug" here https://radianaudio.com/blogs/articles/southI -coast-casino

https://audioxpress.com/article/tes...eering-950pb-and-760neopb-compression-drivers

But it doesn't exactly say as much here.
https://radianaudio.com/collections...ts/760neo-3-dia-2-exit-neo-compression-driver

However, I can’t find any details about the phase plug design for the 745NeoBe in this review
https://audioxpress.com/article/the-745neobe-compression-driver-from-radian-audio
nor at Radian’s website. https://radianaudio.com/collections/hf-neo/products/745neo-3-dia-1-4-exit-neo-compression-driver Nor so with the Ferrite version.
https://radianaudio.com/collections/hf-ferrite/products/745pb-3-dia-1-4-exit-compression-driver

Even stranger is that the same three-slit plug design is employed in this driver.
https://audioxpress.com/article/voi...udio-475bepb-8-1-beryllium-compression-driver

It couldn’t hurt and I was too curious not to email Radian this morning about any significant differences between the phase plugs of the 1.4” exit 3” diaphragm 745Be and the other drivers above.
 
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