Thanks for pointing this out, as the presence of this acoustical crossover is new to me. Is there a somewhat simple way to explain this driver diaphragm protective /crossover dual action of the horn?
That is, in a two way system with a compression driver in a horn above a woofer, I don’t see the crossover analogy, nor can I picture the action or overlap between the electrical crossover and this horn imposed acoustical crossover.
Obviously, unless you change some physical aspect (s) [which?] of the horn its crossover frequency will remain fixed. Through whatever means you can measure or calculate a particular horn’s crossover frequency, though a crossover frequency spec of 750Hz is stated for this horn. https://audiohorn.net/next-gen-bi-radial-horn/
However, is that spec, in fact, just the horn's acoustical crossover or is it telling you that 750Hz should be the total composite acoustical and electrical crossover frequency?
But how would the horn's acoustical crossover spec then allow you to determine the ideal electrical crossover frequency between a particular compression driver and woofer? That is, one which:
Maximizes uniform frequency response of both the CD and woofer (down to ~ 80Hz at 90db in my case) while preventing audible 3rd harmonic and IM distortion.
Minimizes beaming by both drivers.
Maximizes off-axis response.
Minimizes cumulative spectral decay time.
"Richer" is a subjective term, might mean more distortion, longer time delay, more bottom, less top end. There are no T/S parameters that address any of those terms, other than Sd, and the Sd of any 4" dome diaphragm is pretty much the same.
That's OK by me.
Many studio owners have chosen to use Radian HF drivers over JBL HF drivers in their monitors, and Radian built their reputation from customers choosing to use their diaphragms over JBLs in JBL drivers.
Since you don't feel you have the ability to install your new 3" Radian neo BE drivers on a horn, obviously I wouldn't recommend messing around with used drivers that cost a fortune and may not sound any better.
I've preferred the performance of a 3" diaphragm over a 4" in every aspect other than SPL.
They would sound very similar if equalized the same.
With a proper crossover, a co-ax BMS 4592ND can go a bit louder with less distortion than either.
A horn is not a crossover.
An electrical crossover is a device that “divides” the tonal spectrum at a given frequency and sends a portion of the spectrum to one destination, and another portion to yet another destination.
A horn/driver has a raw frequency response which determines it's useful range, which one bases the electrical crossover design upon.
Changing a physical aspect of the horn will change it's frequency and polar response.
A different horn requires a different crossover to achieve a target acoustical response.
The raw response of the horn (purple, before EQ or crossover) falls off steeply below 600 Hz, so it should be crossed over higher.
Without EQ, it would "honk" at 2.5kHz, and sound "dull" above, as the raw response drops off at ~6dB per octave.
6dB per octave is the response of a single pole crossover.
Unlike your AH425/Radian Be, which has near flat on axis response with no EQ, All contant directivity horns need corrective EQ.
https://audiohorn.net/next-gen-bi-radial-horn/
The acoustical crossover frequency is the composite result of the horn/driver raw response and the electrical filters applied.
The usual approach to crossover design is to make the acoustical crossover similar for each band, which may require different electrical crossover slopes for each band.
A steeper and higher electrical crossover will reduce 3rd harmonic and IM distortion.
At 90dB, audible distortion won't be a problem.
Electrical crossovers have no effect on the polar patterns of the drivers.
One can choose an acoustic crossover frequency where the different bands have similar polar response
Electrical crossovers have no effect on the polar patterns of the drivers,
Electrical crossovers have no effect on the drivers cumulative spectral decay time.
Electrical crossovers have an effect on the phase of each band, and should be designed to keep the phase change smooth through the acoustical crossover region.
Properly executed, on axis one will not be able to determine by ear the acoustical crossover frequency.
Art
Last but not least:
1/) Way up on my performance criteria ratings list will be which of Troy’s and NicoB’s horns sounds the least like a horn system.
2/) While intensely curious about hearing them, I am also very apprehensive about using any beryllium compression driver with dozens of my less than pristine recordings. Pierre most generously spent three hours reviewing 52 of my uncompressed WAV files of CD track rips via my Google drive. While he approved and even raved about the sound quality of some, most he found were hit with excessive dynamic range compression (for the sake of https://en.wikipedia.org/wiki/Loudness_war and to compensate for the obvious limitations of cheap vinyl and even cheaper turntables of the 1960s).
And some Pierre said sounded “congested” (e.g analog tape saturation? Poor miking techniques?)
No doubt, all Be drivers are merciless with source material; it’s always garbage/beauty in/out, and probably more so than any other diaphragm material.
At least in this regard, it might partially qualify the statement from those Yamamoto designers whom Ro808 had quoted: “Be diaphragms don’t make music”
No doubt a diaphragm like https://usspeaker.com/B&C-DCM50-1.htm
or https://www.usspeaker.com/bms 4592nd-Mid-1.htm would be more forgiving; another reason why I thought to go with a three-way.
And unlike clipping or hum which can be excised https://downloads.izotope.com/docs/rx6/22-de-clip/index.html , there is no fix to restore the lost dynamics of over compressed recordings.
Of course, pursuing this game is hardly to build systems to play poor recordings. Unfortunately, lots of my favorite music were produced that way, deliberately or otherwise. But how many ear fatigue attacks will I suffer during every listening session from hearing my troubled recordings of musical favorites with Radian Be drivers, particularly the 745Be?
How smart would it be to take that risk?
If possible, please recommend two or three of the best constant directivity horns for the Radian 745 and 950/951 which would work best with my midwoofers.
https://josephcrowe.com/blogs/news/altec-416-8b-in-100l-sealed
https://user.faktiskt.io/RogerGustavsson/416-8B LF Speaker.pdf
Thanks for those explanations about driver/horn raw response and how designing the electrical crossover to correct it will then become the composite acoustical crossover. Also, about at least one of the causes of honking!
Okay, BMS 4592ND vs. both Radian Bes for a two-way. But now see post 15663.
At 11 ft away in a ~ 3200 cu ft room (triangular ceiling; side opposite long wall open to ~ 4 ft x 15 hallway), how safely loud would I want within the driver's bandwidth? https://en.wikipedia.org/wiki/Equal-loudness_contour
Okay, BMS 4592ND vs. both Radian Bes for a two-way. But now see post 15663.
Don't see why you wouldn't be more impressed by the 4" Radian 950's or BMS 4592ND's midrange, at moderate or other listening levels.
And never without penalty?
Except that I have no chance to hear the AH425 horn in time, much less with the RadianBe. And NicoB's CD horns, which I can hear soon may have the directivity polars I'm looking for, at least if they don't require a huge amount of room treatment. But I'm very worried that Troy might not agree to use those horns.
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If i may be honest, i do not know the particular insides of the 745/950/951 well enough.
FX. The 950 has a exit angle of 2x10,3° =20,6 degrees.
Jbl 2450 and TAD 4001/4002 are 10 degrees.
The 950/951 use a different 5 slit phase plug.
Check 5. In the drivers manual i attached.
For the 951, behringer electric makes a customized 1,4" copy of the JBL H9800/H4348, that fits it.
It's a "JBL" biradial, with diffraction slot. Can find plenty of info on it in tech. Manuals etc. But might not be what you are looking for.
Augspruger makes/order theyre own horns for the 950pb. Not many hours away from NY.
VUE audiotechnik makes theyre own for the 950/951 drivers they use with own label that fits. Maybe can be bought as replacement, if you find a fitting one.
I would advice you to look at this thread, where the Radian 950 is compared to the JBLs on same horn, and you see the resulting throat mismatch fairly easily. So you understand why we advice against it.
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If you listen louder than you presently do, you probably will suffer more.
I won't attempt to assess your risk/reward ratio preferences in terms of "smartness".
The electrical crossover is used to limit the lower frequency range of a HF driver.
Equalization adjusts level to fit a desired profile, a horn/driver with flat on axis may not require any EQ.
Since you aren't planning to listen to your AH425/Radian Be, which has near flat on axis response with no EQ, you won't have the opportunity to compare it to horns that require EQ to sound similar.
"Safe" as designated by the Occupational Safety & Health Administration (OSHA) could easily be exceeded within a compression horn driver's bandwidth at 11 feet (or anywhere in a domestic size room)in a matter of a few minutes.
NIOSH is much more conservative.
I said I preferred the performance of a 3" diaphragm over a 4" in every aspect other than SPL.
You might find the louder levels available from a 4" (or equivalent annular diaphragm) more "impressive", but having suffered considerable noise induced hearing damage, I don't want to subject my ears to that level any more.
I'm going to vacuum the house now, it produces about 80dBA at my ears, I'll be wearing hearing protection.
Art
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This has been stirring in my head ever since I read it around early last year.
https://josephcrowe.com/blogs/news/...river-test-review?_pos=2&_sid=cfaba5768&_ss=r
And yes, I also have that preamp; bought it last year from a thread member who bought it from Don Sachs. The seller had Don do most of his mod offerings. The preamp is based on this one https://www.tubes4hifi.com/pre11.htm#SP14
which Don modded. http://www.dsachsconsulting.com/custom line stage.html
And that is nearly the same as this one which Pierre built but added balanced I/O.
https://glass-ware.store.turbify.net/ainost.html
https://josephcrowe.com/blogs/news/...river-test-review?_pos=2&_sid=cfaba5768&_ss=r
And yes, I also have that preamp; bought it last year from a thread member who bought it from Don Sachs. The seller had Don do most of his mod offerings. The preamp is based on this one https://www.tubes4hifi.com/pre11.htm#SP14
which Don modded. http://www.dsachsconsulting.com/custom line stage.html
And that is nearly the same as this one which Pierre built but added balanced I/O.
https://glass-ware.store.turbify.net/ainost.html
So according to the above sheet, with a 80dBA vacuum cleaner, you are safe unless you vacuum clean for more than 8 hours continuous. You're wearing ear protection...big house?
Not a big house, takes 30-60 minutes depending on how far I want to take it.
If I don't use hearing protection with continuous levels of 80dBA(slow) the high frequency ringing (tinnitus) in my hearing increases and takes a good portion of the exposure time to drop down to its "normal" levels.
At 80 dBA, one could supposedly be safe for over 24 hours of exposure even under the more conservative NIOSH (National Institute for Occupational Safety and Health) standards:
At 110 dB, the NIOSH daily exposure limit drops to one minute.
It's easy to exceed the NIOSH limits in under 60 seconds of exposure with small compression drivers on large horns crossed at 500 Hz driven with more than a few watts.
If used to small speakers that sound bad at 10 dB under that level, the lack of audible distortion can make potentially hearing damaging levels seem "normal".
Art
Thanks for sharing the NIOSH graph, good that you remind people of the adverse consequences of listening too loud for too long at clean CD output in domestic environments. I use the 4592ND, but with a 0,5 Watt tube amp, 100-110dB max. output. Saves my hearing, although my hearing was damaged after a jam session of 15 minutes standing besides a drummer that played extremely loud in a small space., and also by attending house club and disco evenings for many years, and playing in bands in rehearsal rooms for years. It is not too bad for my age but noticable. Light tinnitus as well.
How did I know that was coming before I finished reading the prior sentence? But can you guess that again my reply is yes, I know that, but the AH425 won't give me directivity like this. https://www.bcspeakers.com/en/products/horn/1-4/0/me90
However, speaking of that horn which you had also recommended, will it give me the sound stage width and depth that Pierre said he enjoys with the 4001 horn?
It's also important to note that the difference in exposure time is logarithmic (as is dB scale)- a 10dB increase in SPL is only safe for one tenth the time period.
100dBAslow-900seconds, 110dBAslow-90seconds.
Fortunately, music generally has almost the inverse spectra of an industrial noise source like my Hoover vacuum (79dBAslow in a carpeted room, 84dB in a narrow tile floor hallway).
The Hoover rises at ~6dB per octave up to 5kHz:
That 5kHz level is similar to a typical live music show that averages ~102dB at 63Hz:
As the World Health Organization states in their "Global Standard For Safe Listening Venues and Events"
"For parity across standards, the sound level limit for entertainment venues and events further applies the equal energy principle to the
80 dB(A) for 40 hours a week recommendation. This translates into a sound level limit of 100 dB(A) for approximately one hour 45 minutes per month."
I didn't recommend the constant directivity B&C ME90 horn, I wrote it would work well above your Altec midwoofers crossed ~800-900Hz to your Radian 745NEOBe, assuming proper horn equalization as would be required for any constant directivity horn/driver combination.
The AH425 and 4001 horns are not constant directivity horns, and they each have different polar patterns than ME90 horn, so would require different (and less) EQ for flat on axis response.
I still have no idea how your perception of sound stage width and depth compares to Pierre.
Art
Obviously, that's the thing that terrifies me about horns; some kind of accident that could only happen to me-the King of Bad Luck. I think I once read that OSHA warned that even open windows exposing ears to constant levels ~ 73db can possibly endanger the hearing mechanism. In fact, what also worries me about my Sachs preamp is that unless I follow the preamp/power amp turn on AND turn off sequence there could be loud transients, especially with these drivers. For that problem, I'm wondering if power strips which sequence the device power up/down order according to where you plug in that thing's power plug. See chat with d1966 and jaddie. https://gearspace.com/board/so-much...13411-power-conditioners-who-uses-them-2.html"Safe" as designated by the Occupational Safety & Health Administration (OSHA) could easily be exceeded within a compression horn driver's bandwidth at 11 feet (or anywhere in a domestic size room)in a matter of a few minutes.
NIOSH is much more conservative.
The other potential danger are power line transients in systems with high efficiency horn speakers. Which device here https://neurochrome.com/collections/power-supplies or elsewhere can allow me to limit adjust average system SPL of my mains (not the subs) to ~ 77db at 11 ft?
I can't argue with this. I wear ear plugs when I vacuum and whenever I'm outdoors-even while driving with the windows up, which is practically always. Okay, then no 4" diaphragms. But please reply to other concerns.
This certainly isn't Pierre's particular horn but this is from NicoB. https://audiohorn.net/img/bi-radial/TAD-TH4001-polar.jpg
Overall, it seems to resemble perhaps not this https://bcspeakers.com/uploads/products/graphs/2020_10_22_12_34_06_407_ME90_map_Hor.png but certainly this, save for what's causing those peaks/dips with the 4001 horn above 10kHz. https://www.usspeaker.com/images/ciare-pr614-hor-size475.gif
Unfortunately, I've yet to hear any speaker system which impressed me as having great sound stage width and depth. IIRC, Pete Grzybowski's Volti speakers may not have been properly placed when I heard them, circa 2016. Very long before that I was likely very impressed when I saw a Bond film here. https://cinematreasures.org/theaters/4091
https://in70mm.com/news/2003/syosset/index.htm
Come to think of it, Pierre should know better than practically anyone how differently are the soundscapes of AH425 and the 4001. Before he ended up staying with the 745Bes in the 4001s, he long had them in the 425s, and said as much in detail here. https://www.diyaudio.com/community/threads/beyond-the-ariel.100392/page-764
And since the directivity of horns like that B&C ME90 and Ciare PR614 are far closer to that of Pierre's 4001s, it seems logical to conclude that those and/or other 1.4" constant directivity horns would most likely deliver the inviting sound that Pierre described.
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The directivity of the "constant directivity" B&C ME90 and Ciare PR614 is not close, or even very similar to that of a sectoral throat "90x40" degree exponential radial like Pierre's TH4001s.
Horns like the TH4001 trade narrowing vertical response to offset the upper mass rolloff of large format (3" or 4" diaphragm) compression drivers.
That's just a silly take-away.
4" diaphragms pose no intrinsic greater danger than 3", and neither prevents irresponsible misuse.
Presumably, as both the TH4001 and Troy's ES290's are exponential horns their directivity isn't much different than this.
https://cdn.shopify.com/s/files/1/0...BMS_4591-8_off-axis3_480x480.png?v=1649504045
Arnaud Le Gac said he only makes constant directivity horns, and Docali recommended this one for a 2" driver.
https://alg-audiodesign.com/pavillon-iwata-2/
You are spending a lot of time discussing this on the internet in more than one forum. It's a great idea you are trying to educate yourself to make a wise decision. You would be much better off tracking down and listening to a couple of these horns. Just because so and so thinks it's the bee's knee's doesn't carry any real weight. You need to hear them for yourself.
You can talk about this all day what matters is if like what you hear not what someone else thinks.
Rob 🙂