In some rooms, a diagonal placement is the best, (or least worst..) option.
Your sketch doesn't provide the detail for me to see what might work.
Get a ruler and draw out the floor plan, it's a lot easier than moving hundreds of pounds of speakers around.
You live in the USA, you are free to choose whatever horns you want.
Two separate speaker systems in one room means one is in the wrong position, unless you want to sit in two different positions.
Two separate listening positions might benefit from different horn polar patterns.
Your "miserably undersized" room length is longer than many control rooms used to mix and master recordings for thousands of hit records.
Abbey Road's Studio 3 control room is under 20 feet front to back:
In any room size or dimension, I'd prefer at least half it's space behind the equilateral listening triangle.
You misinterpret much of what you read that has any technical aspect.
The ALG sectoral throat bi-radial Pavillion ARIA A-290 could be (kinda sorta) considered "constant directivity", but the ALG Iwata 2 is definitely not. It's HF -6dB beamwidth would be about what the red lines would indicate:
If you can't see at least one side of the throat in this type of horn expansion from the listening position, you are not going to hear much direct high end.
The ALG Pavillion Iwata 2 may be slightly less beamy than the IWATA-300 (a lot less than the IWATA-200) but still not much different than your AH425.
Art
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Okay, should now come the time for compromise? If any constant directivity horn (e.g NicoB's , Cirare PR614, B&C M90) would really be detrimental to imaging (in my not very good room), rather than going to beamy exrtremes with the AH425, why not the ES450?
https://josephcrowe.com/products/3d-cad-files-horn-no-1994-es450-biradial-for-jbl-2446-2-throat
Or ES290, like Marco recommends?
https://josephcrowe.com/products/3d...24212&pr_ref_pid=4111598026817&pr_seq=uniform
Would not both be a perfect match for the JBL2450J + Bes? And the ES290 in particular working best with the Altec midwoofers?
A good low diffraction constant directivity horn is not detrimental to imaging, but won't provide any better imaging than your AH425s at a single listening position.
Another pair of beamy horns..
Apparently, some would argue that sound stage does not exist solely in the recording. At the risk of being slapped down for referencing less than expert and/or compensated sources, such as Stereophile or Absolute Sound reviews, when speakers-or amplifiers, DACs and (don't get Amir started) cables (?? Et tu Blue Jeans?? https://www.bluejeanscable.com/arti...gp1i0RhFiTG2l5hjMlu9uDNefWrwxqNHBawcJblDov3yy )-just about all of these reviewers AND brands speak of the sound stage and imaging size and precision of these hardware products.
Me, I'm just the messenger, but it's has been going on for decades in the CE industry.
So what's going on here? Can speakers or other hardware only "enhance" the sound stage and imaging already embedded in a recording, or can they somehow for lack of a better term "synthesize" it?
Second, Pierre has long been a huge source of knowledge, patiences and kind assitance-as well as fortutious reference, especially in this instance, since as I pointed out to Weltersys, Pierre went from long using the Radian 745Bes in the AH425 horns to obviously finding happiness with the Radians in the TH4001s, above TAD 1601 woofers, though with 2" adapters which Docali helped him design.
Granted, the 4001s are not CD horns, but they're definitely not beamy either. https://audiohorn.net/img/bi-radial/TAD-TH4001-polar.jpg So, how likely did Pierre sacrifice imaging realism by moving from AH425s to the TH4001s and/or moving his speakers however much further apart, as shown in post 15266?
https://www.diyaudio.com/community/threads/beyond-the-ariel.100392/post-7481975
Pierre possibly does vary his listening distance at times, and by using the 4001 it looks like he's able to arrive at a near ideal compromise between imaging quality and sweet spot size-AND that he evidently finds it beneficial even just for one listener.
Also, while he does miss what the 425 horns delivered, said Pierre The sweet spot is very large (width and depth) and the speakers can be listened to closer and further off axis than the JMLC, without noticeable tone degradation. By virtue of its low profile, the sectoral horn allows positioning the two drivers closer together. At short to moderate listening distances one can hear this as tightening the image. A benefit in my room is that the narrow vertical dispersion attenuates ceiling reflection.
So my question is would I not be better off with a less beamy horn than the AH425; one which can project an expansive sweetspot but not so big that it compromises the recording's clarity and accuracy of vocal and instrument imaging?
If I go with a restored pair of JBL2450J (and added Be diaphgrams), Docali and Marco said no adapter is needed for the TH4001 or Troy's or ES450 or ES290 horns.
Questions? Comments? Advise?
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Very interesting point, lets talk about it lol. The distance to the back and then to your ear, has to be thought about, attenuation over distance helps to lessen the effects of indirect sound. We also have HRTF for help damped the rear sound.
According to Grok;
How the Ear Processes Sound from Behind
- Head-Related Transfer Function (HRTF):
The HRTF accounts for how sound waves are filtered by the head, pinnae, and torso. For sound from behind (e.g., 180° azimuth, directly behind you), the head creates a head shadow, attenuating high frequencies (>1 kHz) because the sound must diffract around the head to reach the ears. The pinnae also reflect and diffract sound, adding spectral cues (e.g., notches at 6-10 kHz) that help distinguish “behind” from “in front.” - Interaural Time Difference (ITD) and Level Difference (ILD):
- ITD: For sound directly behind, the time difference between ears is near zero (similar to sound from directly in front), making front-back localization tricky. ITD is more useful for side sources.
- ILD: High frequencies are quieter when coming from behind due to head shadowing—e.g., a 6 kHz tone might be 5-10 dB lower than from the front, per Moore’s An Introduction to the Psychology of Hearing.
- Pinna Cues:
The outer ear (pinna) adds direction-specific notches and peaks. For sound from behind, the pinna’s rear-facing ridges create a notch around 6-8 kHz, while front-facing sound has a peak at 4-5 kHz. Your brain uses these spectral differences to resolve front-back ambiguity, as noted in Blauert’s Spatial Hearing. - Torso and Head Movement:
The torso reflects sound from behind, adding a slight delay (e.g., 0.1-0.2 ms), and head movements help disambiguate—turning your head slightly shifts the HRTF, confirming the source’s position.
I think this is wrong, but I am not 100%... The higher the DI the lower the acoustic power put into the room, and less power needed for the driver to produce it. With an extreme example, of DI, we end up with a loudspeaker that can only be heard on its 0 axis.
Just nitpicking details btw, I believe you are right that Diffusion on the backwall is a good thing, If... the situation calls for it. I am lucky to have a long rectangle basement, so the rear wall is almost 40ft away.
FWIW, I don’t see anything “technical” here; do you?
https://alg-audiodesign.com/pavillon-iwata-2/
But with regard to this issue, Arnaud’s did say I'm not sure I understood the expressions "You Are There" and "They Are Here" [okay, LOL] but ………to answer your question, most of the horns on the site are constant directivity except for certain models and of course circular horns.
Another pair of beamy horns..
Well, I think Marco would have a valid reason for recommending it, and it's certainly less beamy then the ES450-and no doubt WAY less beamy than the A425. Speaking of which, as Lynn's thread is like the genesis of the 425 has anyone ever seen a Geddes plots of that horn there? In fact, I can't recall seeing any such plots on any thread on this forum.
AND what about the Geddes plots of all those other JMLC-like horns you said you've heard?
Let's see some.
And the choice of driver can also impact directivity, such as https://croweaudio.blogspot.com/2020/03/es-290-biradial-with-jbl-2446h.html
Hoping a pair of restored JBL2450J + Bes will look at least a bit better than those Geddes plots.
Except that my room has gross asymmetries, which apparently are serious enough for you to point to. But what cost effective solutions are there for them?
Did I miss something? You already have a system in the room. Who would know better than you?
Rob 🙂
Whats going on here is that you finally got yourself amongst some well meaning people who believe in a science based approach to loudspeaker design which includes the proper use of terminology as it applies to the study of Acoustics.
Just because you are confused, doesn't mean I am lol.
You can distort the sound stage in any way that you prefer, and then call it an enhancement. When everything is set up technically correct, you will render something as close as possible to what the sound engineer responsible for the recording intended. You can of course, deviate from accuracy towards preference. In the land of preference anything goes.
Think about the concept transfer function. Most aspects a transfer function not far from 0 is desired amongst those who looking for high accuracy... that means every aspect can seen as a transfer function where 0 is perfect accuracy. Accuracy to what? To the source. The equilateral triangle of listening, is a 0 transfer function... a neutral FR is a 0 transfer function... I need to brush up on this aspect for decay, but, <300ms sounds right for clarity.
"(<250Hz) need longer decay (0.4-0.5s) for warmth; high frequencies (>7kHz) shorter (0.1-0.2s) for clarity" - Grok
Someone here maybe can sharpen this perspective. Notice that the timings are within a couple hundred milliseconds.
You can separate direct and indirect sound and give them a neutral FR, that would be 0 transfer function.
FR and Decay issues can come from loudspeaker or room but the room tends to be grossly more problematic, hence the need for room treatment and Directivity. When we talk about the 0 transfer function of the room, which is directly tied to indirect sound, and decay.... the true 0 position is in the mastering room. Here you will find the place where people will do the next best thing and create the room they desire. Those who desire accuracy generally have rooms that trend towards certain characteristics, remember the picture of the studio measurements, a trend is there.
With decay times a uniform character with a slight tilt causing slightly lower times towards Hf might be ideal. I continue to learn but I have not mastered all things
Interesting is that some people seem to think a very neutral FR is too bright. I deduce that they have Low Di and no room treatment, thus high rt60... the long decay times in contrast to the short cycle times of Hf is the likely cause. The High Di of some beaming horns (which are also called a horn with rising DI btw, way less menacing adjectives lol) doesn't have this issue since the high DI can create studio like decay times without room treatment as displayed in my rt60 pictured for you previously. The large width of my horn also allows directivity lower into the spectrum which helps to lower decay times. Large baffles have the same affect just less potent than the same size with increased wall angles like inside a horn/waveguide.
With that said, any of the horns you've chosen can have studio level rt60's with room treatment, but the biggest horns and the ones with the highest Di will help you get there with less or no room treatment. You aren't going to get a horn as big as mine, you already have dimensions set for your woofer baffle but try not to get a horn thats skinnier than your woofer baffle.
Maybe this info can help you make your own critical judgments.... maybe lol
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No, all I have at the moment are four Rythmik F12 subs. My midwoofers-essentially leftover clones of a DIYer whose system I thought of having Jim Salk build for me years ago-are now with Troy Crowe, who will use them to build a pair of speakers by end of summer. Expecting it to be a two-way. Have to decide on a horn an driver by end of April.
It may be counterintuitive, have you considered that both of these things have been shown to create problems?
For a given 1 watt of input in a horn(driver) you get a corresponding output in acoustical watts. This same acoustical power is spread by a low DI speaker and beamed by a high DI speaker. The high DI speaker will sound louder in the direction of the listening position for the given input. For a given spl on the listening position however, I guess it is true that the high DI speaker needs less input power than a low DI speaker, as less power from the low DI speaker reaches the listening position. Hence the confusion.
TO demonstrate the connection of visuals of the throat and what you hear.
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Wow that's getting a bit tight. How's the Iwata in the vertical? To head in vise for me, don't like speakers that beamy.
To each their own
Rob 🙂
@AllenB Why didnt you tell me I use the word bandwidth incorrectly... I don't feel bad other then for causing confusion, beam+width=Angle????.... Hey how wide is that beam? 24 degrees? ok thanks....Senseless but not my invention... Arch length is the correct term, Ty @docali other wise I would be confused still...
@Robh3606 at 1m, ±12° is 0.42m (16.5"); at 2m, 0.84m (33") who has a head that would fit in a vice that is 16" wide 😂
@Robh3606 at 1m, ±12° is 0.42m (16.5"); at 2m, 0.84m (33") who has a head that would fit in a vice that is 16" wide 😂