Cardioid Bass

[Graham Maynard]

I ran out of time editing.
Should be more time available !

Hi Ken,

Yes, and similar crossover induced phase changes with frequency which modify a transduced amplitude response.

I used the words 'transduction phase' myself descriptively here as part of this discussion. They are not a technical term used anywhere else.

I don't like the theoretical term 'minimum phase', and I don't like the term 'linear' as applied to the response of L+C+R components used in networks, because there can be serious phase and music waveform distortions - a considerable difference between an original music waveform and the eventual air displacement using purely 'minimum phase' and 'linear' components !!!

But thats me !

All I have been saying is that it is transducers amplitude/phase response which develops the cardioid sound field, and this cannot hold through frequency, or dynamically if generated using different *pole or tuned mountings due to driver-crossover-wall/room reflection affecting the composite output after the response has been set up using steady sines.

JohnK's single driver, or co-sited dual/more drivers with very close 'transduction phase' characteristics (which includes crossovers and EQ) are essential for cardioid to hold with music waveforms.

So would more complex cardioid be worth the efforts ?

Cheers ....... Graham.

 

[Pan]

Hi Pan,

Drivers sorted ? If only !

Yes I do believe that there are no mystic things going on in dynamic loudspeaker drivers. The physics is sorted out.

None is fullrange

True!

and without need for augmentation via crossovers,

Don't know what you mean with augmentation as I never heard that word in this context before. Do you mean correction of frequency response?

and all generate transduction phase change across their own individual working ranges.

Yes, a driver is a minimum phase device and therfore any deviation from flat frequency response comes hand in hand with a deviation of phase. This is really no problem the way I see it as long as the frequency response and phase response is within target and group delay below the threshold of audibility.

What made me react was your way of proposing that a correction of a non flat frequency response is problematic because of the phase distortion that follows.

Thing is that a driver (min phase) that roll off early in the bass has groupdelay that goes hand in hand with the roll off. If an electronic filter (min phase as well) is used to equalize the driver output for a deeper response and a more gradual roll off.. then the group delay (and phase response) will improve in the passband.


/Peter

 

[Graham Maynard]

Hi Pan,

You wrote;-
>> What made me react was your way of proposing that a correction of a non flat frequency response is problematic because of the phase distortion that follows. <<

THAT IS A PROBLEM FOR MUSIC, if not for sines !!!
You cannot electrically pre-compensate for subsequent mechanical dynamics or sequential RLC circuitry which is not purely resistively loaded.
And whilst line generated EQ can flatten a sine response it simultaneously degrades a dynamic response, as for music.

I must leave this, for I will only end up repeating myself and becoming annoyed.
Any wonder I so dislike the technical terminology mentioned here !

Cheers .......... Graham.

 

[otto88]

(just saw this thraed)

Earl

> In a small room, i.e. not an auditorium, there is very little to be gained from a directional bass source. SO basically all of the configurations that you showed are simply ways to expend more money with no net gain.

If you mean a typical living room, your conclusion differs from Linwitz, and my experience of the Orion.

What about less room interaction ?
Why do you say that?

Regards

 

[dlr]

I used the words 'transduction phase' myself descriptively here as part of this discussion. They are not a technical term used anywhere else.

Using terms only you understand, rather than the developed and well understood standard terms, will guarantee continued frustration on your part.

I don't like the theoretical term 'minimum phase',

That is the only fully descriptive term. It defines particular characteristics of the device. Not liking it is not a valid reason to ignore it. There is no other term to use in its place of which I am aware. If there is, I suspect that you will not like that one, either.

and I don't like the term 'linear' as applied to the response of L+C+R components used in networks, because there can be serious phase and music waveform distortions - a considerable difference between an original music waveform and the eventual air displacement using purely 'minimum phase' and 'linear' components !!!

Those arguments are irrelevant to the usage and definitions of the terms. There seems to be misunderstanding on your part as to what the term "linear" means. That confusion often arises as it is generally used to distinguish between linear phenomena, such as the "linear" portion of driver frequency response, and non-linear phenomena, such as the non-linear part due to motor displacement-induced non-linearities. Linear in terms of FR does not connote flat response.

Crossover componentsare linear devices with the exception of the exceedingly small non-linearities inherent in any real world device. If you're referring to phase shift due to the crossover topology, just say so. Not liking a term is not conducive to good communication.

I believe that the confusion and your frustration will continue if you refuse to use the accepted terms. It would be in your interest in discussions to use the (nearly) universally accepted terms.

Dave

 

[gedlee]

(just saw this thraed)

Earl

> In a small room, i.e. not an auditorium, there is very little to be gained from a directional bass source. SO basically all of the configurations that you showed are simply ways to expend more money with no net gain.

If you mean a typical living room, your conclusion differs from Linwitz, and my experience of the Orion.

What about less room interaction ?
Why do you say that?

Regards

This is the same question as has come up before in this thread and I suggest that you read the thread.

Is your experince backed by measurements or is it based on your subjective opinion? If you have data to show that your experiences are supported by actual measurements then I would be very interested in seeing it. But I have done lots of simulations and built and measured a lot of rooms and all my data says the same thing. The way to make the bass in a room room as smooth as possible is to use multiple monopoles. Now I find that I subjectively prefer this approach and many others have thought so too, but you may not like it. I have no way of knowing that.

Directionality of sound at LFs is simply not a concept that has any foundation in physics. Thats my point from above.

Room interaction, as far as directivity is concerned, is an extremely important criteria in the dense modal region. But in the discreet modal region it has no validity. And I'll say it again, that there is no mathematical way to prove that dipole or cardiods excite fewer modes than a monopole. They simply excite them differently. What people always do is to place a dipole at a point and show that it only excites along a certain direction and the monopole excites in all directions - true enough, at THAT point. But I can also find a point in that same room which the monopole will NOT excite and the dipole will when aligned in a certain direction. For each dipole example there is an alternate monopole example.

The ONLY way to settle this argument about "more modes" versus "less modes" is to model a room with monoples and dipoles placed at a number of locations and to look at the statistics of these placements. I did this back in the early 00's and it was published in JAES. My data showed that there was not a strong difference between the smoothness of the different types of sources, the room dominated this characteristic, but the monoples did have a far greater output at the lower frequencies. The conclusion was clear. Linkwitz did not like my conclusions, and he told me so, but he did not refute them either. His impressions are all based on subjective data and not on objective data.

If you keep up on JAES you will realize that everyone is coming to the same conclusion on this, JBL, myself, several other acoustic consultants. Multiple monpoles is the way to get the smoothest and most efficient bass response in a small room. We all prefer this smoothness, but not everyone will.

I actually do say, however, that I am not as concerned with the type of sub, monopole, dipole, cardiod, etc. as I am with the number and the placement. The number and placement makes a far bigger difference that the type (BECAUSE the room dominates the problem so the solution is independent of the source type). So if you like dipoles, use them, but below 100 - 150 Hz you need to have multiple ones and they should be placed around the room.

 

[Graham Maynard]

Hi Dave,

Here we go again - your response to me is no surprise.
I had no frustration relating to my use of the term 'transduced phase' and was quite happy to explain, so where did YOUR comment come from ?

As from *before*, you imply I lack inderstanding and you do little other than argue, dissect posts and nit-pick by shifting discussion to points I do not mention, rather than discuss the points I do actually raise !
(Woe be the day I am obliged to think and write the same as you just to satisfy you. You should be celebrating the differences between folk and their thinkings in this world, not setting yourself up as a critic of those who are different.)
Would you rather I left diyAudio ?
If no, then don't attempt to mould me according to your requirements !

I had been addressing the far from obvious fundamentals relating to loudspeaker driven air motion and the generation of a cardioid response wrt an original electrical waveform. I can appreciate specific terminology might be relevent to you, but that does not alter the fundamentals I discussed before Pan brought up this 'minimum phase' diversion.

Now it would be nice for you to actually contribute about the subject of this thread, so Dave, I look forwards to reading your input about cardioid instead of criticism about non-essential terms I did not use and have clarified my wish to NOT use !


Cheers ............ Graham.

PS. No I was not refering to phase shift.

 

[Pan]

Graham,

I would be interested in what the imperfection are (IYO) to equalizing a LS driver into a desired response. Also what the difference would be with a speaker that has an intrinsic response compared to one that has another intrincis response but altered by the means of EQ to match the former.

Should add that I'm talking about small signal behaviour.


/Peter

 

[dlr]

Hi Dave,

Here we go again - your response to me is no surprise.
I had no frustration relating to my use of the term 'transduced phase' and was quite happy to explain, so where did YOUR comment come from ?

I pointed out your use of terms that only you may understand since they, as you specifically stated, "are not a technical term used anywhere else". You prefer to use your terms when appropriate terms exist that you do no like. It does appear to me that there may be some misunderstanding of the typical usage of the term linear, maybe I'm wrong on that one. Your descriptions seem to be contradictory in that area at times.

Your words are your words, I did not write them. You said "I don't like the theoretical term 'minimum phase' " to which I replied. You said "I don't like the term 'linear' " to which I replied. It was not a post of mine that caused you to introduce this.

If you don't want this discussed in a thread, don't bring them up. This all occurred after a post in which you said "I don't regard either crossovers or drivers as being minimum phase devices." You may consider it a diversion, but don't be surprised if there is a response when you include a statement that is contrary to accepted theory about a fundamental property.

In another post you said "I must leave this, for I will only end up repeating myself and becoming annoyed. ". This ultimately is what prompted my post. You were frustrated for a reason. All I did was point out and explain why I think that without doubt, you will continue to be frustrated if you use your terminology that is at times not clear and refuse to use terms that you "don't like" when they are the generally accepted terms or when you discount accepted theory. This situation has arisen on a number of occasions for the same reason.

Dave

 

[gedlee]

Now it would be nice for you to actually contribute about the subject of this thread, so Dave, I look forwards to reading your input about cardioid instead of criticism about non-essential terms I did not use and have clarified my wish to NOT use !

Cheers ............ Graham.

Graham

I certainly wouldn't get upset with Dave as he is the one making the most sense. He is trying to help you and you are just rejecting his comments off hand. Be thankful that he takes the time to read your posts and try to understand them and comment. Not everyone will do that.

You have to use terms that everyone understands in the same way that they understand them There is no other way to have a dicussion. If you use trems that only you understand or, even worse, you use terms where your understanding differs from the common usage, then there is going to be a great deal of confusion and communication is impossible.

Its like speaking another language where you are using the same words as the other person, but you have defined them differently. You have no idea what each other is saying and you both think that the other one is crazy. The one who is NOT crazy is the one using the common deffinitions.

 

[Graham Maynard]

Hi Dave,

As I said - here we go again - arguing about dissected posts - you this - I that.

So unproductive, and so *NOT* original thinking.

Yes I did write
"because I was not going to repeat myself any more"

If the explanations I had *previously* given, and which were based upon fundamental principles without any need for other terms were not adequate, then I was going to give up, because there is no sense in me repeating myself if not understood.

I don't blame anyone, not even myself, and not a problem.
So why comment ?

And you highlight;-
>> I don't regard either crossovers or drivers as being minimum phase devices <<

Yes, I was writing about phase variation with frequency. Reactive arrangements acting sequentially (also written somewhere) where behaviour becomes independent in time of the source which energises them and cone loading, and which simultaneously but differently modify the amplifier's on-going drive non-linearly in time !

Far too many balls to drop if watching only one from a 'minimum phase' viewpoint !


Hi Earl,

You know what - I want the different approach - and the more I am told I should 'conform' the more I see a need to not do so in order that I can look at problems from different perspectives.

I did not bring up the terms I am being told I must use.

I merely stated I do not like them, and that I do not wish to use them, especially because they represent exact opposites to the *fundamentals* of what is happening to reproduced waveforms in *time*. This being essential to keep in mind within rooms as you state, and with regard to cardioid generation too.

Far too many test examinations relate to sine wave response only, or simple impulse response testing, and not to recording waveform distortion in time due to phase changes, which become reproduced as audio image smear in time, or additional 'noise'.
Good to see Gerrit establishing some aspects here at last !

Theory can distract a mind's eye and fixate thought processess, such that established concepts and a need to follow rules can blinker what might otherwise be free thinking towards overview and other possible real world acceptable solutions.


Now I AM bouncing this ball back, for although I have made efforts to contribute it is clear my method of playing has become unacceptable, and there is so much else to do besides fending criticism.

Cheers ......... Graham.

Pan. Just spotted your last.
The EQ and the LS act independently in different *time* frames.
Simulate a voltage EQ circuit followed by amplifier driving a virtual LS and watch what happens to the voice-coil current when waveforms change.
Steady sine will reveal nothing. An impulse will though !

 

[Pan]

Pan. Just spotted your last.
The EQ and the LS act independently in different *time* frames.
Simulate a voltage EQ circuit followed by amplifier driving a virtual LS and watch what happens to the voice-coil current when waveforms change.
Steady sine will reveal nothing. An impulse will though !

Yes, aply a voltage to a reactive device and there will be something going on that you do not see with a resistive load. But when it comes to audio we must begin with the ears.. not what the eyes think looks nice on the scope.

It's perfectly possible to add phase distortion that makes the signal looks like crasy on the scope.. and still don't hear the presence of it.


/Peter

 

[Pano]

Well I must be quite mad, because what Graham says makes sense to me.

I certainly don't know if what he says is true, but find it interesting, fairly easy to understand and would like to know more about it.

If group delay is messing up the perception of musical signals - and it's doing weird things to the cardioid response - I'd like to learn more about it. (no matter what terms he used to express it).

 

[gedlee]

If group delay is messing up the perception of musical signals - and it's doing weird things to the cardioid response - I'd like to learn more about it. (no matter what terms he used to express it).

The audibility of group delay has been studied quite extensively. The best research was done By Brain Moore at Cambridge. He found that group delay was not audible, but his circumstances were rather restrictive in my opinion. Lidia and I showed how group delay could be audible, but only at higher SPL levels, Moore did his work at lower listening levels, and we did ours over headphones and Moore did his in a listening room over loudspeakers.

What we all agree on is that group delay is not audible at low frequencies. It becomes audible at about 1 kHz and peaks at about 3 kHz. Its audiblity increases with SPL. Thus it is not masked with level as harmonic distortion is - it does the exact opposite.

There is absolutely no reason to believe that coherence in a waveforms appearance has anything to do with audibility. The reason for this is easy to see if you look at how the ear detects sounds (see http://gedlee.com/Home_theatre.htm , read Chapter 2.)

I can completely scramble the appearance of a waveform and yet it will sound exactly the same. What we see and what we hear are completely different things.

 

[HiFiNutNut]

What we all agree on is that group delay is not audible at low frequencies. It becomes audible at about 1 kHz and peaks at about 3 kHz.

Higher order crossover has higher group delay. Most designs use 2kHz - 4kHz crossover point between the tweeter and the woofer.

Does it mean something like LR4 shouldn't be used? It is the most popular XO for crossing tweeters to woofers.

What sort of group delay around 2kHz would be considered not audible? BW1, LR2, BW3, LR4?

Regards,
Bill

 

[gedlee]

Higher order crossover has higher group delay. Most designs use 2kHz - 4kHz crossover point between the tweeter and the woofer.

Does it mean something like LR4 shouldn't be used? It is the most popular XO for crossing tweeters to woofers.

What sort of group delay around 2kHz would be considered not audible? BW1, LR2, BW3, LR4?

Regards,
Bill

Personally I avoid the issue altogether by not having a crossover above 1 kHz.

 

[Etienne88]

back to cardioid

I found a very appropriate paper on the web that I would like to share with you. You can find it here.
One of the conclusion they draw: A cardioid excites room modes in pressure-nodes as well as velocity-nodes. Therefore its coupling to room modes is far less position dependent than that of a monopole or a dipole. Experiments prove that the cardioid maintains nearly the same mode excitation pattern even when placed in contrary positions (corner vs. centre). Turning the cardioid can help to adjust for an even mode excitation pattern.
The whole paper is based on the assumption that the room modes are evenly distributed. My question is then: how do you know if the modes are evenly enough distributed in a given room? Is the Bonello criterion a good start?

Feel free to browse the whole web site, the publication part is of interest. There is for example a paper about improved control of room mode excitation using multiple low frequency cardioids in multi-channel systems. Unfortunately it is in German... But the pictures speak for themselves. I also found a PowerPoint about room treatment that shows that the room modes determine the reproduction of the lower frequencies (which is in total accordance with what Earl said earlier in the thread).

Regards,
Etienne

 

[Pan]

Of course groupdelay is audible.. if high/long enough. The question that remains is at what levels does it beomce audible.

If I remember correct, a swedish engineer that has done work for SR (swedish radio) found that if the GD is held at 0.8/F* or below it is not audible. One exception being the 100-250Hz range where the sensitivity seems to be higher with percussive material like some drums.

*0.8/100Hz=0.008seconds.



/Peter

 

[Pano]

Re: back to cardioid

I found a very appropriate paper on the web that I would like to share with you. You can find it

Great find on that paper, Etienne. Thanks for posting the link.
Funny thing is tho, after reading the paper and being convinced of how much better the cardioid is, we see the last graph - figure 15. What's that all about? The dipole looks about as good as the cardioid.

Of course groupdelay is audible.. if high/long enough.

Sure is. That's what the early cinema sound guys found out. All that 1930's Hollywood tap dancing was a dead give-away that somethng was wrong. Ta-tap, ta-tap

I always wonder about kick-drum. Rock kick-drum is a lot of LF with a high click on top. Most kick mics are even EQ'd that way. What happens when GD pulls the high and low of the Kick out of time? I think that's what Graham was getting at.

The 0.8/F figure is interesting. Do you think you could find the reference?

 

[Pan]

Re: Re: back to cardioid

The 0.8/F figure is interesting. Do you think you could find the reference?

It's information that I have read on Swedish forums and from conversation with people. The work has been for the researcher self and for SR and for some companies. As far as I know little of the material has been published (which is a shame).

The person is the one behind Guru speakers and Ino Audio.


/Peter