Ideal off-axis response

[daftcombo]

Hi,

The consensus for on-axis response in an anechoic room seems to be flatness from 20Hz to 20kHz.

Is there also a kind of consensus for off-axis, let's say 30° horizontal response of a speaker?

Cheers.

 

[Thomas_A]

No there is no consensus other than there should not be gross variation in amplitude for 1st reflections. Having a large room where 1st reflections (sidewalls) come later than a certain value (10-20 ms) you can allow more dispersion. A small room the reflexes *may* come too early that disturbs the precedence and you would benefit with a more narrow dispersion. It is probably not entirely true since reflections do fill in the errors of the stereo system and should be just right, and also is subjective, depend on the music style (studio recording, live classical?). (Talking about stereo only here).

 

[Juhazi]

Dr. Floyd Toole et al. created some proposals for Harman Group. Smooth is consensus, but there is discussion about how steep the the DI slope sould be and from what frequency up. And about how far off-axis we should look/measure. And how about vertical directivity importance.

It also depends on listening distance and room size, reflectivity, speaker/listener placement, and personal preference/judgement of sound.

A good synopsis here
http://www.acousticfrontiers.com/20...kers-open-up-your-acoustic-treatment-options/
http://www.acousticfrontiers.com/20...nse-psychoacoustic-and-subjective-importance/

 

[Soniclife]

Is perfectly flat not the ideal result? The only remaining question being should it be attenuated compared to the on axis, and if so how much at each angle.

 

[MZKM]

It should be as close to the on-axis as possible in terms of FR. In terms of loudness, that is room/setup dependent.

 

[Juhazi]

Is perfectly flat not the ideal result? The only remaining question being should it be attenuated compared to the on axis, and if so how much at each angle.

Good question. "Flat" off-axis with gradual attenuation is physically almost mission impossible (multi-way dipole and cardiod speakers can do this best). Music spectrum is 20-20.000Hz which means wavelenths 17,2 meters - 0,0172meters. Transducers trying to reproduce this variance are in trouble, and the higher the requency, the harder it gets to maintain wide and smooth dispersion.

In listening tests it has been shown many times that people around the world prefer a slightly tilted power response at listening spot. A typical 3-way speaker with dynamic drivers and flat on-axis response at 2m distance can achieve this goal rather easily. If the loudspeaker has different or uneven directivity profile, the task gets more difficult or even impossible.

The listening room always modifies reflections and reverberant energy and our perception has it's own rules for direct vs. reflected sound.

 

[Thomas_A]

Although flat on axis is the dominating view, some prefer a somewhat deviating frequency response due to the stereo system errors. You can argue both ways, but for a pure and more or less untouched live recording with good microphone technique can be more neutral if the frequency response is adapted to that of Shirley et al. That is my view.

https://www.audioholics.com/room-ac...ons-human-adaptation/what-do-listeners-prefer

 

[jonfitch]

I prefer a tilted down soundpower, which generally means off axis response is flat but starting from around 45 degrees it starts to roll off, ala Kef Reference or Genelec The Ones.

I find Revel's flatter sound power with flat off-axis out to 60 degrees gives slightly better intelligibility but the trade-off is a somewhat brighter treble presentation that I don't like for music.

I personally run a Revel Ultima2 system for home theater but KEF Ref 1/Genelec 8331 for nearfield music playback. To me the Revels are brighter than I like for music playback.

Is perfectly flat not the ideal result? The only remaining question being should it be attenuated compared to the on axis, and if so how much at each angle.

Depends on who you ask. I believe Earl Geddes prefers more narrow dispersion and Toole prefers wider and extending the flat off-axis response further out.

I think the more rolled off design is more common these days--TAD, KEF, Genelec, etc which all draw from the same research all seem to focus on rolling off past around the 45 degree mark whereas Toole/Voecks seem to prefer going more wide.

 

[aarons915]

This has been on my mind lately as well and I posed a similar question in the What Science shows thread on AVS hoping Dr. Toole would bite but he didn't. He mentions that the early reflections should be smoothly declining or constant directivity but it seems like one has to be preferred. Based on the Salon vs M2 shootout I have to think the smoothly declining early reflections is best. I definitely don't think flat, which would basically be omni-directional, is ideal, based on hearing a very wide dispersion 3-way, that sounds too bright in my room.

 

[Kal Rubinson]

To me the Revels are brighter than I like for music playback.

Revel/Harman has a "anechoic correction" curve for this. It is mild but, to me, makes all the difference.

 

[echopraxia]

Good question. "Flat" off-axis with gradual attenuation is physically almost mission impossible (multi-way dipole and cardiod speakers can do this best). Music spectrum is 20-20.000Hz which means wavelenths 17,2 meters - 0,0172meters. Transducers trying to reproduce this variance are in trouble, and the higher the requency, the harder it gets to maintain wide and smooth dispersion.

In listening tests it has been shown many times that people around the world prefer a slightly tilted power response at listening spot. A typical 3-way speaker with dynamic drivers and flat on-axis response at 2m distance can achieve this goal rather easily. If the loudspeaker has different or uneven directivity profile, the task gets more difficult or even impossible.

The listening room always modifies reflections and reverberant energy and our perception has it's own rules for direct vs. reflected sound.

I recently did a blind test comparison between the KEF R3 and Ascend Sierra 2EX. I’ll probably cross-post that thread to these forums (if that’s allowed), but in summary: the Sierra 2EX won easily, by a large margin.

The Sierra 2EX actually has remarkably wide and smooth dispersion all the way up to 20khz, which as you say is quite an impressive accomplishment. The question many people ask is, is this desirable? Some people think it is, some think it’s not. Fewer seem to have tested these hypotheses in blind tests. That’s what I hope to help out with, even if by a little bit.

I think the results of my blind test surprised many, because though there is not a full consensus here, many people seem to just go with how Harman designs their speakers as the model of the ideal speaker. And by that standard, obviously the Sierra 2EX deviates quite a lot by having a drastically broader treble dispersion (more linear, too). Some say this makes it superior, others question that. Well, I figure only a blind test can truly answer this.

The results of my recent blind test is at least a hint that dispersion should be both smooth AND wide to achieve the best sounding speaker. Not proof by any means, but one intriguing bit of evidence pointing in that direction.

Next I am going to be comparing the Neumann KH120 to my Ascend Sierra 2EX. The Neumann’s spin measurements appear to extraordinarily good. One therefore would expect them to beat the Sierra 2EX. If not, this would be another strong data point in favor of the broad dispersion preference theory.

P.S. This time I will (probably tomorrow) post a pre-test thread asking for suggestions and advise for test methodology etc., to try to make my next blind test as scientifically valuable as possible.

 

[Blumlein 88]

These links might help with understanding what good spin data is for a speaker.

https://www.audioholics.com/loudspeaker-design/understanding-loudspeaker-measurements

https://www.sausalitoaudio.com/wp-content/uploads/2018/07/Interpreting-Spinorama-Charts.pdf


https://speakerdata2034.blogspot.com/2019/02/spinorama-cea-2034-2015-ansi-data-format.html
Explanation of what to look for in spin data results.

https://speakerdata2034.blogspot.com/2019/03/all-spinorama-data-index.html
Some speakers and their spin data with links to the results.

 

[jonfitch]

I recently did a blind test comparison between the KEF R3 and Ascend Sierra 2EX. I’ll probably cross-post that thread to these forums (if that’s allowed), but in summary: the Sierra 2EX won easily, by a large margin.

The Sierra 2EX actually has remarkably wide and smooth dispersion all the way up to 20khz, which as you say is quite an impressive accomplishment. The question many people ask is, is this desirable? Some people think it is, some think it’s not. Fewer seem to have tested these hypotheses in blind tests. That’s what I hope to help out with, even if by a little bit.

I think the results of my blind test surprised many, because though there is not a full consensus here, many people seem to just go with how Harman designs their speakers as the model of the ideal speaker. And by that standard, obviously the Sierra 2EX deviates quite a lot by having a drastically broader treble dispersion (more linear, too). Some say this makes it superior, others question that. Well, I figure only a blind test can truly answer this.

The results of my recent blind test is at least a hint that dispersion should be both smooth AND wide to achieve the best sounding speaker. Not proof by any means, but one intriguing bit of evidence pointing in that direction.

Next I am going to be comparing the Neumann KH120 to my Ascend Sierra 2EX. The Neumann’s spin measurements appear to extraordinarily good. One therefore would expect them to beat the Sierra 2EX. If not, this would be another strong data point in favor of the broad dispersion preference theory.

P.S. This time I will (probably tomorrow) post a pre-test thread asking for suggestions and advise for test methodology etc., to try to make my next blind test as scientifically valuable as possible.

I think it's mostly a preference thing when it comes to ideal dispersion.

Some people are also more sensitive to directivity issues. When I compared the Sierra 2 EX to the Salk Silk and Scansonic MB-1B, I felt the Sierra 2 EX had the worst driver matching between the RAAL tweeter and the 6" woofer, where the dispersion was excessively wide at the tweeter axis but the woofer's dispersion near the crossover frequency noticeably narrower. The matching was a somewhat better with the Salk Silk's 5" driver (smaller woofer with wider dispersion and larger ribbon tweeter with narrower dispersion), but ultimately the Scansonic sounded like it had the best directivity matching with the use of a waveguide around the ribbon tweeter and a small 4.5" woofer. If I didn't know I would think I was listening to a typical waveguided dome tweeter, that's how good the directivity match was with the Scansonic/Raidho tweeter + woofer.

 

[echopraxia]

I think it's mostly a preference thing when it comes to ideal dispersion.

Some people are also more sensitive to directivity issues. When I compared the Sierra 2 EX to the Salk Silk and Scansonic MB-1B, I felt the Sierra 2 EX had the worst driver matching between the RAAL tweeter and the 6" woofer, where the dispersion was excessively wide at the tweeter axis but the woofer's dispersion near the crossover frequency noticeably narrower. The matching was a somewhat better with the Salk Silk's 5" driver (smaller woofer with wider dispersion and larger ribbon tweeter with narrower dispersion), but ultimately the Scansonic sounded like it had the best directivity matching with the use of a waveguide around the ribbon tweeter and a small 4.5" woofer. If I didn't know I would think I was listening to a typical waveguided dome tweeter, that's how good the directivity match was with the Scansonic/Raidho tweeter + woofer.

Out of curiosity, what does this directivity matching (or lack thereof) sound like, subjectively? I’ve never sat in front of a speaker and said to myself and said “wow the crossover dispersion is matched really well” or vice versa. When you’re listening on-axis and at an appropriately large distance from the speakers, what does this difference sound like to you, in non-speaker-designer terms?

When I compared the Sierra 2EX to the KEF R3, the KEF did not sound any more like a point source whatsoever, at least in this room. Both sound like point sources to me, until you get really close (much more so than you should for these kind of speakers).

I would grant you the Sierra 2EX is not appropriate for a near field monitor like a coaxial or my purpose built monitors are, but I don’t see that as a problem since they’re not meant to be used as near field monitors.

You may also be right that different people have different sensitivities and preferences for speaker directivity behavior.

 

[aarons915]

When I compared the Sierra 2EX to the KEF R3, the KEF did not sound any more like a point source whatsoever, at least in this room. Both sound like point sources to me, until you get really close (much more so than you should for these kind of speakers).

I don't think the KEF R3 is a great example of this since the woofer to midrange crossover is at 400Hz, right in the middle of the vocals. Did you not notice the point source nature of the LS50 wireless? I feel the 2-way coaxials do a much better job of this at the expense of being more limited by bass and distortion compared to a 3 way. Revels are very well integrated as well, the closest I've heard to a coaxial speaker.

 

[jhaider]

Is there also a kind of consensus for off-axis, let's say 30° horizontal response of a speaker?

"Smooth" is the only consensus.

 

[phoenixdogfan]

The way I understand Toole is that the frequency response should be dead flat from 20 to 20kz IN AN ANECHOIC CHAMBER which will result in what we identify as the Harman Curve in a normal listening room.

 

[Duke]

Out of curiosity, what does this directivity matching (or lack thereof) sound like, subjectively?

It often sounds like coherence; you are not aware of hearing the crossover.

It also tends to sound non-fatiguing (assuming there are no other problems), as there is no significant spectral discrepancy between the first-arrival sound and the reflections. When there is a significant discrepancy between the two, it can show up over time as listening fatigue.

In my opinion.

 

[Ilkless]

It often sounds like coherence; you are not aware of hearing the crossover.

It also tends to sound non-fatiguing (assuming there are no other problems), as there is no significant spectral discrepancy between the first-arrival sound and the reflections. When there is a significant discrepancy between the two, it can show up over time as listening fatigue.

In my opinion.

This has been my experience. It manifests as a subtle congestion.