ZDL

[Joachim Gerhard]

OK, Markus i understand. So there is even one more definition of nearfied. Measuring very close to the membrane at less then 11% of the effective membrane radius.
What i mess, now we have 3 definitions.

 

[markus76]

I though we were discussing diffraction and its affect on temporally accuracy.

No, we were discussing room reflections.

 

[Pano]

I think many people would be surprised to see the extent of the listening window over which such EQ results in an improvement of both frequency and transient response. "Perfect" at only one point does not necessarily mean degradation everywhere else

Having heard this in action (Lyngdorf and others) I agree. The one point may be best, the the others are not bad at all.

 

[markus76]

Pano, John didn't talk about room reflections.

By the way, how does the Lyngdorf optimization work? I guess they don't disclose the underlying principles.

 

[john k...]

No, we were discussing room reflections.

OK, my mistake in reading. My comments addressed diffraction artifacts. Agreed that early reflections can smear temporal detail. Agreed that correction by EQ is limited to a very small window in that case. Should be addressed by room treatment or speaker placement to avoid early reflections. Isn't that a given?

 

[markus76]

Isn't that a given?

Probably not in a discussion about speakers that light up as many early reflections as possible.

 

[soongsc]

That is not necessarily correct. If the EQ is developed to correct the response at the listening position then at the listening position the response will be correct. If the direct sound is an impulse of magnitude 1 and a reflection of magnitude 0.5 arrives 0.5 msec after the direct sound than by adding inverse of the reflected impulse to the system after 0.5 msec then at the listening position the direct sound inverted impulse will cancel the reflection. There will be a reflection of the correcting impulse which is then canceled by another correction and so on. If the sum of the original direct plus reflected sound is minimum phase, then MP EQ will provide the necessary correction. You can check this out with the UE.

The problems are:
1. The mic measures one point, but you have two ears.
2. Even if you were able to equalize to two points, do you really want to spend time to make sure your ears are always at the measured location? The distance between the ears are different for each person....

Edit:
Did not see you later posts. Yes, the diffraction artifacts are effectively EQed as long as the distance to the ear are very close to being the same as the source. Still, my preferred EQ measurement point is near field based on listening evaluation. This is possibly because both of our ears are never at the same distance from any single speaker. While we have EQed the speaker at one point, and we listen at another, plus two ears have different distances, there is still some uncertainty. If we EQ near field, then it applies to the wider range of listening window.

 

[soongsc]

How fast is the spectral decay in a design like the one Earl promotes?

I have never measured them, so I don't know. But in the process of trying to develop a good waveguide/horn, I have not come up with one that decays faster than a direct radiating driver. I am hoping that UE will improve the situation.

 

[markus76]

I have never measured them, so I don't know. But in the process of trying to develop a good waveguide/horn, I have not come up with one that decays faster than a direct radiating driver. I am hoping that UE will improve the situation.

So, what levels and time frames are we talking about for a direct radiating driver? Is this even relevant in the context of room reflections? If not then I don't understand the relevance of this post.

 

[soongsc]

I cannot give you a pass/fail criteria, but the faster it decays, the better. For example:
http://www.diyaudio.com/forums/multi-way/178350-zdl-36.html#post2444347
For wave guides, please look in the geddes thread, because I have to search just like anyone else.
Anything radiating from the driver will end up in room reflections. They all get mixed together. Since we have no control of the room, we should focus on a design that is a reasonable compromise between listening location variation and trying to excite less room reflection.

 

[markus76]

I cannot give you a pass/fail criteria, but the faster it decays, the better. For example:
http://www.diyaudio.com/forums/multi-way/178350-zdl-36.html#post2444347
For wave guides, please look in the geddes thread, because I have to search just like anyone else.

Faster decay might be better but isn't a speaker's room interaction of greater importance?

 

[markus76]

Anything radiating from the driver will end up in room reflections. They all get mixed together. Since we have no control of the room, we should focus on a design that is a reasonable compromise between listening location variation and trying to excite less room reflection.

So why discuss speakers with broad dispersion when the goal is to reduce reflections?

 

[soongsc]

Faster decay might be better but isn't a speaker's room interaction of greater importance?

Both are of importance in different ways. Of course if you put a good speaker in a glass room, it's going to sound terrible. I have tried it. But we are not talking about room design here.

 

[soongsc]

So why discuss speakers with broad dispersion when the goal is to reduce reflections?

Different people like different sound perception. But also let's not forget that broad dispersion speakers are always placed as far from reflecting walls as you can. If you have some directivity control, the you have a bit more flexibility. I was at a friends home once, and it was fun walking around the room and even behind the electro-static speakers and listen.
Bose has some designs that also rely one lots of room relfection and delayed release of stored energy as well. Lot's of people like that too. The issue is what kind of listening experience is the design goal.

 

[markus76]

Both are of importance in different ways. Of course if you put a good speaker in a glass room, it's going to sound terrible. I have tried it. But we are not talking about room design here.

I don't see any value in designing a car that ignores the roads it will drive on.

 

[soongsc]

I don't see any value in designing a car that ignores the roads it will drive on.

The same thought, you can buy a car for all terrain, but's it's going to be much different from cars that handle well of normal roads, nor is it going to be comfortable as some others on normal roads. The designer has to decide what he's designing for. So it is the same with audio.

 

[markus76]

Different people like different sound perception.

If sound perception varies from person to person then we're lost. If your perception of green can no longer considered to be perceived as green by others then humans would never have developed any language.
Or are you talking about preference? Of course everybody has a preference for something but if you want to have control over a recording to satisfy your personal preference then looking at speakers is looking at the wrong end of the reproduction chain.

But also let's not forget that broad dispersion speakers are always placed as far from reflecting walls as you can.

They are? The setups I've seen suggest that the opposite is true.

If you have some directivity control, the you have a bit more flexibility.

A lot more. Just look at the actual in-room behavior of certain designs.

 

[markus76]

The same thought, you can buy a car for all terrain, but's it's going to be much different from cars that handle well of normal roads, nor is it going to be comfortable as some others on normal roads. The designer has to decide what he's designing for. So it is the same with audio.

That's not the point. You said "But we are not talking about room design here." which equals to "We're not talking about roads" in my analogy.

 

[soongsc]

At least I don't think Joachim is going to recommend putting the ZDL design close to a wall.

 

[markus76]

At least I don't think Joachim is going to recommend putting the ZDL design close to a wall.

The questions is if common room sizes allow a wide dispersion design to be placed as far from the walls as needed? "Floor" and "ceiling" are just another term for "wall"...