Psycho-acousticians use a measure called the coherence to determine when a signal will sound spacious. In this case, coherence is simply the normalized cross-correlation between the left and right ears. It varies between 0 and 1 with 1 indicating completely correlated signals and 0 being completely uncorrelated. The lower the coherence the more spacious the sound is.
When signals arrive from any direction that is in the plane of symmetry of the head, then the coherence of those signals must be 1 since they have to be identical or nearly so. This means that any reflections that arrive in that plane cannot add to spaciousness - they only tend to confuse imaging. So your example only works if the front wall has diffusors. It might enhance spaciousness, but again will degrade imaging. I use absorption to eliminate any frontal reflections thus enhancing imaging. This then also increases the ratio of lateral later reflections from the rear of the room adding spaciousness without sacrificing imaging. Signals arriving from the front (except the first arrival) can only degrade the image.
Yes I had a lot of full with Heil drivers trying to find a balance that worked in my room by attenuating/absorbing the rear radiation. No attenuation spacious but poor imaging. Imaging improved the more I absorbed the back wave. Ended up with it mostly absorbed.
Rob 🙂
Whether it will confuse imaging depends on the arrival of time. And I mentioned specifically having sufficient distance.
For practical reasons and especially to work within my builder’s rapidly approaching deadline, I quickly need help selecting among constant directivity horns which are proven to produce what are generally regarded as near ideal characteristics for home use (~ 3200 cu ft room; slanted ceiling) and which are currently produced commercially.
I only know of these sources:
1/) https://audiohorn.net/x-shape-horn/ and https://audiohorn.net/next-gen-bi-radial-horn/
These were designed by https://www.diyaudio.com/community/members/nicob.210335/
What’s discussed at his website looks impressive to me but experts like Docali and mabat seem to have had numerous problems with NicoB’s lack of available or complete performance data and perhaps his approach to design. Nor had NicoB been active here since October. https://www.diyaudio.com/community/...001-clones-makers.375215/page-17#post-7813229
However, I look forward to what’s no doubt a rare opportunity to hear both of those horns next month, and my thanks to the system owner and NicoB for this.
2/) But I only know of one currently marketed CD horn https://www.usspeaker.com/ciare pr614-1.htm being used by a member now at work with it. https://www.diyaudio.com/community/...e-pr614-horns-to-use-in-a-2-way-build.368904/
But he surely won’t have the speakers finished and evaluated in time for me to consider that horn, as my builder is pressing me to decide on a horn and driver by end of April.
3/) Docali had once suggested that I choose one of these horns but didn’t specify which.
https://alg-audiodesign.com/pavillons/ I shared emails with Arnaud Le Gac, who said none of his horns will fit my 1.4” Radian 745Be, except his round horns, which have “enormous directivity”.
Alternately, I may have the opportunity to get a good price on one of these 2” versions.
https://www.usspeaker.com/radian 950Bepb-1.htm
https://www.usspeaker.com/radian 951Bepb-1.htm
https://www.usspeaker.com/radian 760neoBepb-1.htm
But which of Arnaud’s CD horns to work below my Altec midwoofers?
https://josephcrowe.com/blogs/news/altec-416-8b-in-100l-sealed
Another issue is that NicoB and Arnaud dislike Radian Be drivers. NicoB said “I'm not a big fan of Radian—the phase plugs are outdated, and the Be diaphragms are embossed. I find less and less reason to use Be nowadays.” And Arnaud said “I was very disappointed by the result. The sound is very "hard" to listen to if we compare it to the TAD 4001 beryllium too and it is a driver that ultimately does not go up in the treble, we observe a big attenuation from 10 kHz and suddenly without recovery with another element it will lack detail and precision in the high end of the spectrum.”
However, I didn’t reply that Pierre had addressed limited HF response and perhaps serendipitously that “hardness” problem-which former 745Be user g3dahl also strongly complained about-by apparently perfecting a contouring filter which flattened and extended the response; see posts 15266, 15276. https://www.diyaudio.com/community/threads/beyond-the-ariel.100392/page-764
If possible, please recommend a CD horn which should work well with my Altec midwoofers and either the 1.4” Radian 745Be or the 2” Radian 950 or 951Be.
https://audioxpress.com/article/the-745neobe-compression-driver-from-radian-audio
The B&C ME90 80° × 60° constant directivity cast aluminum horn 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.
Your Radian 745NEOBe 3" diaphragms are not.
They don't need embossing, their response extends past 40kHz.
The B&C ME90's (or any CD horn designed for flush mounting) performance would improve mounted on a baffle of similar width to your Altec.
Art
Last edited:
Thanks for this. From what I can tell the constant directivity of this plot looks impressive.
https://www.bcspeakers.com/en/products/horn/1-4/0/me90, apparently more so than this.
https://www.usspeaker.com/ciare pr614-1.htm
But assuming my room would support it acoustically (~ 2900 cu ft 11 ft triangular ceiling), I would want a CD horn that can give me the sound stage width and depth that Pierre said he enjoys with the 4001 horn.
Btw, invaluable feedback from Docali about need to cover up that safety hole in the Radian 745Be when playing at Pro audio levels. For home levels (!), he recommends closing it. Posts, 91, 94, 98.
https://www.diyaudio.com/community/...ompression-drivers-a-discussion.397699/page-5
Also, see Pierre’s post 101. https://www.diyaudio.com/community/...ompression-drivers-a-discussion.397699/page-6
However, I doubt if my hearing acuity extends beyond ~ 13kHz, might I be better off with a 2” driver-even if not Be-which might therefore deliver a more robust-not simply louder-midrange?
OK, so you are more "impressed" by an 80x60 than a 60x40.
What is your preferred polar pattern?
Are you now planning to build your horns into a room corner?
What acoustic support do you think a room provides?
Docali mentioned he "had a 745Neo and it had a suspicious hole in the back cover."
For all we know, it may have been an inspection hole missing the insert.
None of the photos of Radian 745 I've seen have a suspicious hole in the back cover, does yours?
A larger exit diameter will not help improve hearing acuity.
"Robust" means strong and healthy; vigorous, strong and rich in flavor.
Any size driver can be strong and healthy.
More "flavor" might mean more distortion, as can be used to "enhance" a signal.
Many find harmonic distortion, as added by tube amplifiers, tape saturation, overdriven loudspeakers etc. to sound more euphonic.
I do too, but there is generally more than enough distortion present in recordings that I'd never want to add more, especially on a global basis.
Many 4" diaphragms rely on break up modes to bring up HF response that is lost due to their increased mass rolloff compared to smaller, lighter diaphragms.
My personal experience with hearing loss is that drivers that provides more accurate upper response (smaller diaphragms) make it easier to perceive details.
Without accurate, detailed reproduction, sound stage width and depth cues present in a recording are obscured, more difficult to pick up.
Cheers,
Art
Does not matter 🙂
My experiaence is that the biggest factor is type of attenuation for compression HF units...
The attenuation is huge actually probably more than 10-12 db needed to match the level of LFs...
To ilustrate -6db is half of voltage aplied. another -6db (-12db) is 1/2 of this 1/2...
Tried almost everything. The Lpad is the worse one - 90% people are using... Much better way is Brige "T" net.
Better than this is ballanced Bridged "T"
But the best one is for me Inductive attenuation, with big, tin wire say 22-30mHy inductor with taps.
with C before and after You can form an passive filter.
This will compleatley chaged the sound outcome from speakers. And I will never go back to resistors again.
The issue with big body transformer L att. is that You have to DIY or find custom order. These little ones like Tannoy using are totally inappropriate...
Last edited:
I'm at a loss to know which to prefer. Is the choice for vertical coverage based on on axis listening distance. Please advise.
By support I mostly meant room size. No way to plan for placement at this stage, though my room is largely empty save for the 4 subs, a glass coffee table and two chairs I should have a few options.
Well, did those you've seen have any hole, suspicious or otherwise?? I haven't opened the boxes yet to check.
But how to explain this? Do you think Docali's tricking us or seeing this? I don't. But if mine do have that hole and based on his before/after impedance plot https://www.diyaudio.com/community/...sion-drivers-a-discussion.397699/post-7314315 shouldn't I be concerned if mine does any hole? If so, do what? Cover it with gaffers tape?
So, you haven't analysed your room to work out the needed angles. Now you know that we don't know them either.
That's possibly what contributes to Pierre's perception of sound stage size, and that he gets it from the 3" 745Bes-especially how he describes the sound in much detail while reviewing my recordings. Very grateful to him for the reviews. Again, however, he did obviously derive more such benefits when he switched from the AH425 to the 4001 horns.
The choice of vertical coverage is based on the amount of vertical coverage required or preferred.
A longer distance can use more narrow vertical coverage to achieve the same vertical coverage height.
As I wrote, they did not.
I doubt yours has a hole, and if it has one, it's likely covered by the nameplate escutcheon.
If it isn't covered, it's defective.
The AH425 has wider vertical coverage, so more vertical reflections to reduce detail.
The 4001 has wider horizontal coverage, so requires more toe-in to reduce sidewall reflections.
Either horn would work well in your place, but I'd still suggest using the ones you own before taking a chance on ones you don't own that you may not prefer.
The directivity of the ME90 is the result of a tiny slot, which, combined with the less than perfectly matched throat angle, may affect the listening experience. The 6 cm extra length of the Ciare also facilitates a low XO point.
Feel free to contact me about the horn we have, and I can also assist with acosutics as I've worked with that since 2016. Obviously I can't share much here as a manufacturer.
A word of advice; I would take a lot subjective feedback with a big grain of salt. Lack of proper AB comparisons, different EQ and different room/acoustics give different results. Plus a horn may not be sutiable for a driver if exit angle doesn't match well or an adapter was being used for changing from 2" to 1.5/1.4" or the opposite way.
Keep also in mind that there's a difference between simulations and actual measurements.
I find our horn with Radian 951BePB to sound smooth, but it's certainly also revealing of poor recordrings as very open and transparent speakers are combined with low distortion electronics. We have one pair of the 951 beryllium version left and which is sold with the horns for the old Radian price (Radian is selling the driver now at a much higher cost).
The latest midbass also now has ribs on the rear, which the proto below doesn't have FIY. The protos below can be sold for a much lower price, but with some smaller difference in size and finish between the units.
The measurements below are only of the top horn alone. Measurement distance is too close to give the correct directivity in degrees (required to measure at a fairly long distance from horn and thss a bigger space to measure in). In reality it's narrower and close to 80/90°x50/60°, but the overall smoothness in directivity should be quite accurate.
Horizontal polar:
Vertical polar:
Last edited:
Thank you. If only I had this 2" instead of my 1.4" Radian 745Be, since using adapters is apparently an undesirable compromise. https://www.usspeaker.com/radian 760neoBepb-1.htm
I guess Art had overlooked that as otherwise he said the B&C ME90 horn is a good match to cross the 745Bes with the Altecs at 800 to 900Hz. I can't tell from the vert and hor directivity plots of both horns which one might perform better. Looking at them would you say the ME90? But I'd still would chance using a horn/driver combo that wasn't a perfect adapterless match. Schiit! If only I had this damned driver instead!!!!!! https://www.usspeaker.com/radian 760neoBepb-1.htm