Angle?

[beanbag]

What does point source vs. line source have to do with speaker delay

The gist is that point source speakers are affected by rake and line source speakers not nearly as much.
So if you have a regular speaker with cone drivers and lean it back, the drivers become out of phase with each other.
If you have a hybrid ML speaker with woofer and lean it back:
The panel does not become "out of phase with itself" due to the analysis in post 36. Your midrange to high freq integration remains intact.
The woofer does become out of phase with the panel.
Maybe I should have said that if the woofer was located at the same height as the middle of the panel then it would not be out of phase either.

This is only for the direct sound, and there could be other effects due to reflections and etc.

 

[Gordon Gray]

I don't have the slightest idea what your post means from a real world listening perspective.

I assume you know that the back wave of the panel is out of phase with the front.

Analysis in Post 36?

That also makes no sense to me from a real world listening perspective.

 

[Rich]

If you have a hybrid ML speaker with woofer and lean it back:
The panel does not become "out of phase with itself" due to the analysis in post 36. Your midrange to high freq integration remains intact.
The woofer does become out of phase with the panel.

I understand what you are saying now and it does make sense to me. And it just reinforces my point that the raked back panel is a flawed design.

 

[User211]

Hm... once she's got those Soundlabs straight, she's coming round to make sure your MLs are the same Rich.

She's harsh, though. 40 lashes if they're not But if they are, well... who knows?

 

[Rich]

Hm... once she's got those Soundlabs straight, she's coming round to make sure your MLs are the same Rich.

She's harsh, though. 40 lashes if they're not But if they are, well... who knows?

She can dial my system in any time she wants, Justin! But she may have to bend over to adjust the sub.

 

[Bernard]

What Soundlab, Justin?

 

[Gordon Gray]

I don't have the slightest idea what Post 41 means from a real world listening perspective.

I assume you know that the back wave of the panel is out of phase with the front.

Analysis in Post 36?

That also makes no sense to me from a real world listening perspective.

Beanbag, second request for a response.

PS: And please explain the phrase "This is not exact, but mostly correct". See Post 36.

 

[beanbag]

I don't have the slightest idea what your post means from a real world listening perspective.

I assume you know that the back wave of the panel is out of phase with the front.

Analysis in Post 36?

That also makes no sense to me from a real world listening perspective.

I showed that leaning just the panel by itself backwards doesn't change the sound qualities by very much. so if you notice differences from leaning a hybrid speaker back, it is likely due to the woofer vs panel relative distance.

Yes, the back wave is out of phase from the front, but it is also exactly 180 degrees out of phase and goes the opposite direction, so Time-Parity symmetry is preserved. (Whew!)

I said my analysis is approximate because to truly describe the effects of leaning back a panel would involve computer simulations of how the wave shoots out. If you remember from integral calculus, to analyze an object, you break it up into little sections, and the more sections you have, the more accurate is the answer. You only considered a panel with a top and bottom section and thus you said that there are delay effects from the top vs bottom. I said that there are three sections, and showed there aren't any additional delay effects from leaning the panel.

 

[Gordon Gray]

Time parity symmetry? Integral calculus?

Don't think my ears understand what that means.

I did take calculus in college but that was a long time ago.

In any event, thanks for the attempt to clarify.

 

[MPS]

I showed that leaning just the panel by itself backwards doesn't change the sound qualities by very much. so if you notice differences from leaning a hybrid speaker back, it is likely due to the woofer vs panel relative distance.

Yes, the back wave is out of phase from the front, but it is also exactly 180 degrees out of phase and goes the opposite direction, so Time-Parity symmetry is preserved. (Whew!)

I said my analysis is approximate because to truly describe the effects of leaning back a panel would involve computer simulations of how the wave shoots out. If you remember from integral calculus, to analyze an object, you break it up into little sections, and the more sections you have, the more accurate is the answer. You only considered a panel with a top and bottom section and thus you said that there are delay effects from the top vs bottom. I said that there are three sections, and showed there aren't any additional delay effects from leaning the panel.

Interesting, I always thought angle of the line source is affecting radiation pattern relative to acoustic environment of the listening room. I would like to hear more about time-parity symmetry and panel/woofer relative distance effects vs angle, never heard before of such mechanisms?

 

[beanbag]

I think it would be easier if I just told you to draw a diagram and you can see for yourself.

You know how in the ML owners manual, they have a picture of the panel with straight lines beaming out from in front of it? That is a reasonable representation of the wave that shoots out of it. As long as you are on one of the lines, then all the "musical information" remains intact. You can verify this for yourself. Turn off the woofer, and put your ear right next to the panel. The panel sounds the same over the entire length, right? That's what it means to be "on one of the lines".

If you step back, and then rake the panel, the lines are still hitting your ears, so the sound shouldn't change by much. This is assuming that you don't lean the panel over sooo much that the lines completely miss your head. Then all bets are off.

This is for the direct sound wave. Room acoustics also takes into account the reflections of this wave. So draw another set of lines that goes out the back of the speaker and bounces off the rear wall and then heads towards you. If you change the rake so much that in one case the reflected wave still hits your ears, and in another case it doesn't, then the sound will change a bit. Not all that much since the reflected wave is weak.

Now for the woofer. In this case, the sound propagates out in circular arcs. For a given speaker rake, one of the panel vertical lines is going to intersect one of the circular woofer arcs at your ears. If you lean the speaker back by more, now you will have a different set of lines and arcs intersecting at the ear location. This is what it means to have the woofer and panel go out of phase due to leaning the entire speaker. It's going to affect the frequency response and impulse response. There's probably a particular rake angle that gives the best impulse and frequency response, but I don't know what that is. You'd have to measure it, or use an active bi-amp setup with digital delay.

As for time-parity symmetry, I mean to say pOLarity. oops. For the back wave, you reverse "time", and now the wave moves in a forwards direction. You ALSO have to invert polarity, and hey, now the back wave is the same as the front wave! This has deep and profound implications for the wave propagation mechanics of the speaker.

 

[Gordon Gray]

There's probably a particular rake angle that gives the best impulse and frequency response, but I don't know what that is. You'd have to measure it, or use an active bi-amp setup with digital delay.

You can always use your ears.

 

[User211]

You can always use your ears.

Then again you can always "think", Gordon. Thinking created the engineering products for your ears to enjoy in the first place.

Whether beanbag is entirely right or wrong isn't so much the point. He is trying to understand what is going on. There is no harm in that. He is also going to some effort to share what he thinks he has gained through his investigations and insight.

In some ways, ears are only a part of it, I am afraid.

 

[Gordon Gray]

Justin,

With all due respect, I believe you are being aggressive.

I didn't say he was right or wrong in his most recent explanation and was not being sarcastic. I agree that beanbag is trying to provide us with information that may correlate measurements to what we hear.

That's why I asked the questions I did regarding real world listening impacts.

Gordon

PS: And I do think about many things but generally trust my ears when it comes to audio. Actually, I just had a labatomy so maybe my brain isn't functioning properly.

 

[MPS]

I think it would be easier if I just told you to draw a diagram and you can see for yourself.

You know how in the ML owners manual, they have a picture of the panel with straight lines beaming out from in front of it? That is a reasonable representation of the wave that shoots out of it. As long as [1] you are on one of the lines, then all the "musical information" remains intact. You can verify this for yourself. Turn off the woofer, and put your ear right next to the panel. The panel sounds the same over the entire length, right? That's what it means to be "on one of the lines".

If you step back, and then rake the panel, the lines are still hitting your ears, so the sound shouldn't change by much. This is assuming that you don't lean the panel over sooo much that the lines completely miss your head. Then all bets are off.

This is for the direct sound wave. Room acoustics also takes into account the reflections of this wave. So draw another set of lines that goes out the back of the speaker and bounces off the rear wall and then heads towards you. If you change the rake so much that in one case the reflected wave still hits your ears, and in another case it doesn't, then the sound will change a bit. Not all that much since the reflected wave is weak.

Now for the woofer. In this case, the sound propagates out in circular arcs. For a given speaker rake, one of the panel vertical lines is going to intersect one of the circular woofer arcs at your ears. If you lean the speaker back by more, [2] now you will have a different set of lines and arcs intersecting at the ear location. This is what it means to have [3] the woofer and panel go out of phase due to leaning the entire speaker. It's going to affect the frequency response and impulse response. There's probably a particular rake angle that gives the best impulse and frequency response, but I don't know what that is. You'd have to measure it, or use an active bi-amp setup with digital delay.

As for time-parity symmetry, I mean to say pOLarity. oops. [4] For the back wave, you reverse "time", and now the wave moves in a forwards direction. You ALSO have to invert polarity, and hey, now the back wave is the same as the front wave! This has deep and profound implications for the wave propagation mechanics of the speaker.

You are using terms which are not familiar for me..

1. You are referring to listening in near field, right?

2. How much difference at crossover frequency do you expect to get from few degrees angle? Higher frequencies do not arrive simultaneously at any one point from single uniform line source that's why we get comb filtering from panel and no degree of panel angle is going to change that.

3. I don't see how slight angle (or no) of panel has anything to do phase or out of phase of speaker, can you clarify?

4. Why and how does "time reverse" come to play? I understand basic principals of dipole, bi-pole and mono pole speakers and their acoustical radiation pattern but I have hard time understanding your explanations, please give some reference.

 

[beanbag]

You can always use your ears.

In this case, I'd agree. When you throw room acoustics into the mix, with reflections spraying everywhere, then maybe a particular rake doesn't have the best impulse response, but inadvertently optimizes some other quality.

 

[beanbag]

You are using terms which are not familiar for me..

1. You are referring to listening in near field, right?

Both near field and medium field.

2. How much difference at crossover frequency do you expect to get from few degrees angle?

I guess I have to post a diagram after all.



At the default 5 degrees rake, there is a 2.8" path length difference between the panel and woofer. This doesn't mean that the panel and woofer are out of phase right away. That would depend on the crossover circuits.
If I lean the speaker so it is exactly vertical, the path length difference is 5.6". So there is a NEW 2.8" change in path length. At 450Hz, this corresponds to 35 degrees of NEW phase shift.

Higher frequencies do not arrive simultaneously at any one point from single uniform line source that's why we get comb filtering from panel and no degree of panel angle is going to change that.

Yes, that's what I said back in post 36.

4. Why and how does "time reverse" come to play? I understand basic principals of dipole, bi-pole and mono pole speakers and their acoustical radiation pattern but I have hard time understanding your explanations, please give some reference.

Ehhh, I was just joking around. Time-polarity symmetry is a property of open baffle planar dipolar speakers. Note that this same property doesn't apply to a speaker with a vented rear port, or a passive radiator.

 

[Gordon Gray]

Ehhh, I was just joking around.

Beanbag,

What does that mean?

And how does your excellent graphic, and analysis thereof, correspond to the typical listening height (floor to ears) of 36" to 42"? The drawing shows 48".

GG

PS: Regarding Post 56. I'm glad you acknowledge the importance of hearing in making auditory judgments.

 

[guido]

My SL3s just sound more focused when set almost vertical.

I do not use spikes. Rather, i decouple the speakers from the floor with neoprene and cork pads, double thick in the back.

Works beautifully and musically.

Regards,

Guido F.