Objections to speaker qualifications

[Salt]

Point source may be the wrong terminus (what is the size of a point?), so I would prefer coherent or simultanous sound source for all (most) audible frequencies.

 

[Theta]

You didn't notice my sarcasm...
Your main point was - lobing is not important at all:

So, how is it possible this speaker to sound crappy to you, when it is the epitome of maximum possible lobing?

We are talking about 2 diferent things. A bunch of drivers stuck on a socker ball has more problems then lobing and is not even worth discussing.
Lobing is a term most associated with line source speakers.
Of course lobing can be identified and measured.
My point was: You can't eliminate or disqualify all exellent speakers by yelling lobing when you see lots of drivers on a baffle. That is the pre-conceived opinions I see on this type of design. Some lobing is a trade off that can be acceptable.
Sitting on a chair with the tweeter at ear level without moving your head is a trade off that is not acceptable to me, even if Klipel says it is correct.

 

[Salt]

Don't confuse constant directivity with omnidirectionality.

 

[Platypus20]

I disagree.

View attachment 379868

Jim

Egads!!! I grew up with a pair of them in the living room, my brother’s, his wife would not allow them in their house, my mother, allowed them to set there for about 6-7 yrs, I went to college, after my junior yr, I came home and they were gone. At 14-17 yrs old, I thought they sounded great, but that was 45+ yrs ago. I never found out what happened to them.

 

[Avp1]

Egads!!! I grew up with a pair of them in the living room, my brother’s, his wife would not allow them in their house, my mother, allowed them to set there for about 6-7 yrs, I went to college, after my junior yr, I came home and they were gone. At 14-17 yrs old, I thought they sounded great, but that was 45+ yrs ago. I never found out what happened to them.

B&O did great work in similar design with DSP to control each driver. They were (or is) their real high-end speakers.

MBL sound interesting, as do Ohm Walsh and now new generation of those from German Physiks. Actually they do very good job in small rooms.

 

[Vladimir Filevski]

We are talking about 2 diferent things.

? Which are...?
Lobing is the first thing. What is the second thing?

A bunch of drivers stuck on a socker ball has more problems then lobing

If the drivers are working in the same frequency band (I don't know if it is true for this loudspeaker), than the comb-filtering is the only problem. Obviously, you are confusing lobing with comb-filtering.

Lobing is a term most associated with line source speakers.

No. LIne source speakers made from several drivers working in the same frequency band has no lobing. It has comb-filtering only (in the same frequency band).
Only if this line source is combined with other driver(s) working in the other frequency band (divided by crossover), than the lobing is created.
Obviously, you are confusing lobing with comb-filtering.

My point was: You can't eliminate or disqualify all exellent speakers by yelling lobing when you see lots of drivers on a baffle.

"Eliminate" and "Disqualify" are too strong word - I would say "that loudspeaker potentially has BIG problems". For example, look at the McIntosh XRT2.1K loudspeaker:

It has lobing between the two 6.5" drivers and the line array in front of them. And between the two 6.5" drivers and the other six 8" woofers. Period.
Whether the lobing is small or anaceptable big, depends on the exact crossover frequency and the exact distance between them.
About the comb-filtering here - I don't know if the 2' drivers and 3/4 tweeters are shaded or not.

Some lobing is a trade off that can be acceptable.

Every conventional 2-way, 3-way, 4-way, ... has lobing. So, yeah, pretty common problem... and acceptable, if not too big.

Sitting on a chair with the tweeter at ear level without moving your head is a trade off that is not acceptable to me, even if Klipel says it is correct.

Wrong! Klippel never said that!
Sitting on a chair with tweeter at ear level is how 99.9999999 % of all humans on earth are listening to music in their homes - it is convenient and relaxing. And all of those humans are moving with their heads when listening - what is the problem with that?
I am really curious - how are you listening to your loudspeakers (and which are they)?

 

[kemmler3D]

? Which are...?
Lobing is the first thing. What is the second thing?


If the drivers are working in the same frequency band (I don't know if it is true for this loudspeaker), than the comb-filtering is the only problem. Obviously, you are confusing lobing with comb-filtering.


No. LIne source speakers made from several drivers working in the same frequency band has no lobing. It has comb-filtering only (in the same frequency band).
Only if this line source is combined with other driver(s) working in the other frequency band (divided by crossover), than the lobing is created.
Obviously, you are confusing lobing with comb-filtering.


"Eliminate" and "Disqualify" are too strong word - I would say "that loudspeaker potentially has BIG problems". For example, look at the McIntosh XRT2.1K loudspeaker:

View attachment 379891

It has lobing between the two 6.5" drivers and the line array in front of them. And between the two 6.5" drivers and the other six 8" woofers. Period.
Whether the lobing is small or anaceptable big, depends on the exact crossover frequency and the exact distance between them.
About the comb-filtering here - I don't know if the 2' drivers and 3/4 tweeters are shaded or not.


Every conventional 2-way, 3-way, 4-way, ... has lobing. So, yeah, pretty common problem... and acceptable, if not too big.



Wrong! Klippel never said that!
Sitting on a chair with tweeter at ear level is how 99.9999999 % of all humans on earth are listening to music in their homes - it is convenient and relaxing. And all of those humans are moving with their heads when listening - what is the problem with that?
I am really curious - how are you listening to your loudspeakers (and which are they)?

Unless I've missed something, at least when it comes to talking about interference between drivers, aren't lobing and comb filtering just two ways of talking about the effects of said interference?

Lobing can be at a single frequency, referring to the shape of the sound field. Comb filtering describes the total effect of interference across multiple frequencies, but not the shape of the sound field.

 

[Jim Taylor]

Sitting on a chair with the tweeter at ear level without moving your head is a trade off that is not acceptable to me, even if Klipel says it is correct.

Klippel says no such thing. In the first place, Klippel ( https://www.klippel.de/index.html) is a company that makes instrumentation for testing. One of them is the unit that Amir uses. True to the scientific paradigm, it shows results without judgement.

By reading the results of the Klippel tests, a person can deduce whether the loudspeaker under test has a very narrow sweet spot or a much wider sweet spot. But that is for the person to judge, not the machine.

Jim

 

[MAB]

Sitting on a chair with the tweeter at ear level without moving your head is a trade off that is not acceptable to me, even if Klipel says it is correct.

Aside from dramatically misrepresenting Klippel, I recommend learning to spell the name.
You seem to be the one who has an immovable head.

 

[Jim Taylor]

Perhaps visuals might help.

This is a diagram of lobing. As you can see, the response envelope sags at 2.4 kHz (the red line) due to interference between the tweeter and the midwoofers at that frequency.

This, OTOH, is a site that explains comb filtering in easily understood terms. Notice that the interference follows a mathematical pattern rather than the spatial pattern I showed above.

Acoustical interference and comb filtering - TestHiFi

interference

testhifi.com

Jim

 

[RayDunzl]

The "sweet spot" is referred to as a "spot" for a reason.

If there is more than one reason, the first reason would be "equidistant from the speakers".

spot
/spät/
noun

2. a particular place or point.

 

[Vladimir Filevski]

"Spot" - as a infinitesimally small point in space? No.

 

[Vladimir Filevski]

when it comes to talking about interference between drivers, aren't lobing and comb filtering just two ways of talking about the effects of said interference?

No.
Lobing is createad only when there are 2 (3, 4, ..) physically separated drivers divided in frequency by crossover, as in any 2-way, 3-way, ... loudspeaker. Comb-filtering is created only when 2 (3, 4, ...) drivers are working in the same frequency band (so no crossover).

 

[Blumlein 88]

"Spot" - as a infinitesimally small point in space? No.

Well yes, but with an ear about 3.75 inches (9.5 cm) either side of it.

 

[Vladimir Filevski]

Well, no. If you are listening a few inches left or right from that "spot", you will listen to the exactly same music. Magnepan is excluded, of course.

 

[kemmler3D]

Perhaps visuals might help.

This is a diagram of lobing. As you can see, the response envelope sags at 2.4 kHz due to interference between the tweeter and the midwoofers at that frequency.

View attachment 379897

This, OTOH, is a site that explains comb filtering in easily understood terms. Notice that the interference follows a mathematical pattern rather than the spatial pattern I showed above.

Jim

Sure, but isn't the lobing diagram just a 2D / 3D representation of interference in space, while a comb filtered FR is a representation of interference at a single point in space across multiple frequencies?

No.
Lobing is createad only when there are 2 (3, 4, ..) physically separated drivers divided in frequency by crossover, as in any 2-way, 3-way, ... loudspeaker. Comb-filtering is created only when 2 (3, 4, ...) drivers are working in the same frequency band (so no crossover).

Comb filtering is always created to an extent when there is overlap in frequency ranges from multiple drivers, which almost all crossovers do have. It tends to be minimized in good speakers, but I guess you could call comb filtering a special case in which the full frequency range is damaged. I think of it as a more general thing where you have periodic notches in the FR regardless of bandwidth.

 

[tmtomh]

Sure, I heard one of the first units shipped to the US. (Yeh, I'm that old) Still, it did not create a point source nor did it exhibit the radiation of a point source. As you state in your post, it's a dipole and I'd say a helluva clever design. Still, one can't make a point source with multiple drivers. (Do I hear a head on collision between Maxwell and Euclid?) An audio point source (again, a chimera) cannot be limited as to directivity nor bandwidth. Now, If someone would create a simple spec. specifying transducer "point-sourci-ness" over some frequency within a given directional spread (radiation pattern), we might have something, but still no true point source radiator.

I take your point (no pun intended!) about defining what counts as a point source (or quasi-point source, or coincident source) as a practical matter.

That said, it seems to me that the forum already has a working definition, which is a system with coincident drivers and/or a system whose vertical dispersion measures as others have explained above.

If you’d like to propose a more comprehensive and/or more precise definition, please do so.

But I think there’s limited utility to commenting over and over (and over) again that there’s no such thing as a true/absolute point source.

 

[Platypus20]

Wouldn’t the array effect the dispersion pattern on the drivers behind it ??

 

[Vladimir Filevski]

Comb filtering is always created to an extent when there is overlap in frequency ranges from multiple drivers, which almost all crossovers do have. It tends to be minimized in good speakers, but I guess you could call comb filtering a special case in which the full frequency range is damaged. I think of it as a more general thing where you have periodic notches in the FR regardless of bandwidth.

In lobing there is only one null in the whole frequency response at one particular axis (and maybe second weak one at different frequency, if the crossover is first order), so - there is no comb-filtering in lobing. There must be several nulls in the frequency response, to warrant the comb-filtering name.

 

[stoo23]

Ohm F's were True Omni's

Similarly to the MBL's they aren't true omni but at best axially symmetric in the horizontal plane, but are definitely not vertically.

Hmmm, Really ??
Are there any Measurements / Field 'Plots' that Prove or Disprove this ??

Personally, I think considering the 'Vertical 'Cone' of the Ohm F is, .. a Cone, perhaps the Term 'Axially Symmetric' is a misnomer, as it's 'Dispersion', is in 360 degrees, (Horizontally) and I'd venture to quite some degree vertically as well, plus with the Woofer also firing vertically at quite Low frequency, may I suggest it's dispersion would also be pretty close to Omni-Directional.

I'm actually rather unsure as to What type of Loudspeaker you may or might be trying to describe as 'Truly' Omni-Directional,.. OR,.. for that Matter What and Where it's actual application, would or could be appropriate ??

For ANY True Onmi loudspeaker to work effectively in Omni 'Mode', it would (in effect), have to be 'flying' In the Operational Space