Off-Axis Response of loudspeakers.

[FrantzM]

Hi

I am currently running a pair of Kef LS50 (very decent speakers) with a trio or quatuor of subs. This is an interim system to which I listen to when I need tactile feelings.. I have been listening to a variety of very good headphones and headphones based system the past 5 years ... headphones do sound different but often are more accurate to my ears than speakers .. Yet headphones don't ever fool me that I am listening to the "Real Thing" .. Speakers OTOH do once in awhile and are IMO and IME a better way to experience music ... In the absence of a good speaker ....

My empirical observations have led me to conclude that the best bass is that obtained with multiple subs. There is an almost magical way in which multiple subs add their output in a most constructive way. Of course you just don't drop them in the room and expect great things... Yet arranging subs , even in a quasi-random fashion and taking some care , tend produce a level of bass quality that needs to be experienced. IMHO a total of $1000 (at least 3 subs with continuously variable phase control or better a min-DSP or equivalent (about $250 per sub) would produce results (and levels) that would surpass one $5000 subwoofers in most case. I am trying not to be too hyperbolic..., else I would have said that no lone subwoofer would match unless one is extraordinary lucky. That's for the bass...
As for the rest of the spectrum ...
Harman, a company who may have the greatest concentration of Audio Engineering luminaries in their ranks has taken the off-axis response as i core philosophy. The more I understand how and what we hear in a room, treated or not, the more I am realizing that we hear on-axis is a small part of the overall sound experience, a small part of the sonic landscape. We hear direct sound and reflected sound in most any room. Making sure that the reflected sound that arrives to our ears is similar to the direct is essential. Thus response off-axis must be reasonably smooth throughout the bandwidth of the speaker within its entire dispersion angle. Most speakers do not provide this smooth axis response, including some very expensive and favored ones. This goes beyond the "head-in-the-vise " small sweetspot.
IOW in-room off-axis response in key to high performance in speakers.
Your replies to this post would be most appreciated.

Peace

Frantz

 

[amirm]

Indeed. I had to do a complete reset in my understanding of sound reproduction once I got exposed to Harman's methodology in general, and Dr. Toole's in the specific. While highly technical in nature, the "story" all hangs together at the end as you mention. The sound from a loudspeaker expands and hits all the surfaces and combines with direct sound. So the fact that they play a strong role at the end of the day, makes perfect sense.

And here is the other important side implication. A speaker with proper off-axis response will sound good in any room. You can buy with confidence that when you buy it and put it in your room it will sound good. Esoteric speakers often have very poor off-axis response requiring considerable amount of tuning/decorations of the room to make them sound good. Not so with a speaker that is properly designed based on this research (and double blind verification).

Best example of this is Michael buying his JBLs. He asked me about them prior if that was a good idea. While I had not heard them, and neither had he, based on the above I knew that the "worst case" situation would be a speaker that still sounded good. It is a remarkable accomplishment to buy a speaker without hearing it, and having it perform.

 

[Purité Audio]

For 'traditional' loudspeakers I completely agree, flat on axis and smooth and even off axis that mirrors the on axis response.
Keith.

 

[NorthSky]

Back in the mid 80s I learned that off-axis frequency response was as much important as on-axis frequency response in loudspeakers.
I never deviated from that scientific approach...for the last 33 years.

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

 

[FrantzM]

Back in the mid 80s I learned that off-axis frequency response was as much important as on-axis frequency response in loudspeakers.
I never deviated from that scientific approach...for the last 33 years.

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

You're old

I do consider myself a rather experienced audiophile ... Been in that thing for the past 45 years or so...yet never paid attention to off axis response .. Actually considered it a detriment. IMO up to recently you needed to limit the off-axis response as much as possible... There is a such a school of thought as a matter of fact... I have come also to see that too much of a good things isn't ... such a good thing too. Having heard the MBL 101 several times I don't understand the fascination with Omnis ...

 

[NorthSky]

I'm not old, I'm odd.
_______

Audiofile forums should restrict membership limitation to age 40.
After that imaging off-axis frequency response becomes obsolete.

For the over age 40 group, there should be dedicated audiofile forums for them...with hi-res MP3 audio and youtube videos.

This world was made for the younger generations. As we age so are our aptitudes...Bob Dylan's voice.
It's the same with the Olympics, Boxing and Tennis players.

 

[Fitzcaraldo215]

You're old

I do consider myself a rather experienced audiophile ... Been in that thing for the past 45 years or so...yet never paid attention to off axis response .. Actually considered it a detriment. IMO up to recently you needed to limit the off-axis response as much as possible... There is a such a school of thought as a matter of fact... I have come also to see that too much of a good things isn't ... such a good thing too. Having heard the MBL 101 several times I don't understand the fascination with Omnis ...

I agree about the MBL's. But, it could be worse. There are always Bose 901s, apparently still available. Either way, I think it is the concept of either implanted in audiophile minds by marketing a slick, but superficial and erroneous ideas, not the sound itself, which is different from other direct monopole radiators. I just do not think it is more accurate.

And, frankly, I do not totally get the revolutionary new Beolabs. Much expense seemingly goes into delivering wide, essentially omni response. Yet, everyone seems to prefer the narrowest settings for best sonics. Maybe I do not get the concept in full technical detail. Are the omni drivers applying some sort of out of phase cancellation when in narrow mode? Or, are they just increasingly silent as the dispersion is dialed down? If it is the latter, why not just offer a narrow dispersion version at much, much lower cost, but still having DSP correction, which I am convinced is a truly great thing.

I am not interested in claims here about their wondrous sound. It is more a technical question about how they work.

 

[TBone]

There are always Bose 901s, apparently still available.

still remember this 1 Bose demo, 4 901s cornered in a room seating around 30 or so people. Can't recall if they even played music, certainly remember brief recordings of jet planes flying close overhead, even buzzing chainsaws ... people ducking for cover everywhere.

 

[Thomas savage]

there is a thread dedicated to the beolab 90, I can't vouch for its technical content mind you.

 

[Kal Rubinson]

And, frankly, I do not totally get the revolutionary new Beolabs. Much expense seemingly goes into delivering wide, essentially omni response. Yet, everyone seems to prefer the narrowest settings for best sonics. Maybe I do not get the concept in full technical detail. Are the omni drivers applying some sort of out of phase cancellation when in narrow mode? Or, are they just increasingly silent as the dispersion is dialed down? If it is the latter, why not just offer a narrow dispersion version at much, much lower cost, but still having DSP correction, which I am convinced is a truly great thing.

No expense was incurred to have an omnipolar (Party) response. That came as a freebie because all those drivers, other than the LF, MF and HF drivers on the front, are there for the purpose of modifying the polar response of the front three. RoomEQ is a feature separate from the beam control.

See the B&O white paper: bang-olufsen-beolab90-whitepaper.pdf

 

[RayDunzl]

I have a pair of P-363 with the wide flat dispersion...

And a pair of MartinLogans which should measure about like this...

Here's the first 40 milliseconds of the impulse response of both overlaid in my room at the listening position:

 

[hvbias]

Posting this from the imaging thread so that thread can remain "on topic"
( moderator says.., thank you)

The off axis is entirely created by DSP!
Exactly the same as the Beolabs.
Keith.

That's not the whole story. The off axis performance is a result of

1) DSP
2) driver type
3) number of drivers
4) how the drivers are arranged (which would dictate enclosure shape)

The Kii response is far from bad and I was being facetious in my earlier post. For the amount they cost there are several speakers that out perform them in that area, most from the Harman family.

You still insist the polar plot is perfect. Do you have measurements to back that up? The German mag plot is far from perfect. You could derive a directivity index from their graph and it would be neither controlled or constant.

 

[Purité Audio]

I am afraid you still haven't understood exactly what the Kii and Beolabs are capable of.
Keith

 

[hvbias]

I am afraid you still haven't understood exactly what the Kii and Beolabs are capable of.
Keith

Sorry your attacks on members doesn't strengthen your position

I understand how both work. The numerous bass/midrange drivers on the sides and rear of the Kii can not do anything for the directivity at higher frequencies, something the Beolab do not have an issue with since they have far more midrange and treble drivers arranged in various positions to work with the DSP.

Since this is a science based forum I'll once again post the Kii measurements.

 

[Blumlein 88]

Sorry your attacks on members doesn't strengthen your position

I understand how both work. The numerous bass/midrange drivers on the sides and rear of the Kii can not do anything for the directivity at higher frequencies, something the Beolab do not have an issue with since they have far more midrange and treble drivers arranged in various positions to work with the DSP.

Since this is a science based forum I'll once again post the Kii measurements.

While not a SOTA result it looks not too bad except for the 10 degree vertical. Ouch on that one.

 

[RayDunzl]

While not a SOTA result it looks not too bad except for the 10 degree vertical. Ouch on that one.

Uh, look again.

There's a little green line just under the red axial line.

Also, this has some more explanation - the lower green is taken behind the speaker.

The level of attenuation of the low frequencies at the backside isn't what I might have expected to see based on concept and the ad copy. Reading it again, the "free field" option setting is in use, so, that criticism may be moot.

When is Mr Purite going to take some measurements of all these wonderful speakers he has in his listening rooms for us to critique?

 

[Cosmik]

So today, is the forum in the mode that says measurements are all that matters? The question is then: which measurements? The on and off-axis frequency response is one set of measurements. Phase is another. Distortion is another. Transient performance is another. As are: interaction with the room, matching between channels, consistency of behaviour at all power levels. How do you interpret those measurements? How do you rank them in terms of importance? I don't think it is fixed. Any two speakers may out-perform each other in different measurements, and may even cross over compared to each other as power levels and signal content vary.

By definition, room correction would change those measurements, making them 'look' incomprehensible, yet many here would be saying that they 'must' sound better because they measure 'better' at the listener's position.

I honestly think that 'design philosophy' tells us more than the measurements. One such philosophy is that the speaker should be as neutral as possible, with minimal room correction - which is what the Kiis do.

In this day and age, a system is going to be a combination of software and hardware. Do the designers give off a reassuring impression of understanding those areas, and an openness to new ideas - a willingness to ditch the traditional rule book while remaining fully competent? (Some products just give off an air of dodginess. I read interviews with 'star' designers and some of them are just overgrown teenagers - I would't want their products in the house, and certainly wouldn't leave them switched on unattended).

And for me, anecdotal listening impressions are important. I don't think they are science (I know the variability of my own hearing perception too well), but in conjunction with the designer's philosophy, I still think they tell us a lot.

 

[Purité Audio]

The Beolabs measurements are exemplary see page 14 here, http://www.bang-olufsen.com/~/media...eoLab-90/bang-olufsen-beolab90-whitepaper.pdf

(Edited by moderator ) this is not a market stall Keith. The thread is about off axis not how much your wares cost..

 

[Cosmik]

I would strongly advise trying to hear either or both Kii and Beolab if you have the opportunity.

I am hoping to arrange it, very soon. I look forward to meeting you!

 

[Thomas savage]

So today, is the forum in the mode that says measurements are all that matters? The question is then: which measurements? The on and off-axis frequency response is one set of measurements. Phase is another. Distortion is another. Transient performance is another. As are: interaction with the room, matching between channels, consistency of behaviour at all power levels. How do you interpret those measurements? How do you rank them in terms of importance? I don't think it is fixed. Any two speakers may out-perform each other in different measurements, and may even cross over compared to each other as power levels and signal content vary.

By definition, room correction would change those measurements, making them 'look' incomprehensible, yet many here would be saying that they 'must' sound better because they measure 'better' at the listener's position.

I honestly think that 'design philosophy' tells us more than the measurements. One such philosophy is that the speaker should be as neutral as possible, with minimal room correction - which is what the Kiis do.

In this day and age, a system is going to be a combination of software and hardware. Do the designers give off a reassuring impression of understanding those areas, and an openness to new ideas - a willingness to ditch the traditional rule book while remaining fully competent? (Some products just give off an air of dodginess. I read interviews with 'star' designers and some of them are just overgrown teenagers - I would't want their products in the house, and certainly wouldn't leave them switched on unattended).

And for me, anecdotal listening impressions are important. I don't think they are science (I know the variability of my own hearing perception too well), but in conjunction with the designer's philosophy, I still think they tell us a lot.

fortunately this is a audio forum and not a logic puzzle nor are we dealing with jeopardy of the kind you might encounter defusing bombs.. So we want as much info as possible so members can make informed decisions and God forbid debate the significance of each data point..

From that folks can take whatever conclusions they deem suitable, to negate that because some of the parameters or significance of the data points is open to question is to allow logic to defeat function.