Here is a question I've always wondered about.
Looking at the Jordan JX-92
JX-92
it shows the phase changing with frequency response. This is typical of all single driver speakers.
Does this mean the speaker would not be time and phase coherent?
If so, is ANY speaker truly time and phase coherent?
http://www.ejjordan.co.uk/drivers/jx92.html
Looking at the Jordan JX-92
JX-92
it shows the phase changing with frequency response. This is typical of all single driver speakers.
Does this mean the speaker would not be time and phase coherent?
If so, is ANY speaker truly time and phase coherent?
http://www.ejjordan.co.uk/drivers/jx92.html
At their lower end and in the middle of their range fullrangers are usually excellent. Only a few are good at their upper end however.
But the Jordan driver in question is a particularly good one in this respect !
Regards
Charles
But the Jordan driver in question is a particularly good one in this respect !
Regards
Charles
I think a time aligned 2 or 3 way has a good chance at phase from low to highs.
I think gma claimed +/- 10 degrees from 100-20khz but I could be wrong.
Norman
I think gma claimed +/- 10 degrees from 100-20khz but I could be wrong.
Norman
But then he might also have used a tweeter that is reaching > 100 kHz or used some electronic phase-compensation or he simply made a measurement error !
Regards
Charles
Regards
Charles
true, I had not though of that.
It is tough on a 6db because rule of thumb is the driver need flat freq response 2 octaves beyond crossover point. Although some probably are flat only 1 octave.
And the driver will roll off when it hits its own rolloff point.
Thiel crossovers are quite large, I think they compensate for that but I'm unsure.
Norman
It is tough on a 6db because rule of thumb is the driver need flat freq response 2 octaves beyond crossover point. Although some probably are flat only 1 octave.
And the driver will roll off when it hits its own rolloff point.
Thiel crossovers are quite large, I think they compensate for that but I'm unsure.
Norman
Phase starts to deviate from zero long before the cutoff frequencies are reached. This can be seen very well in the diagrams of the aforementioned Jordan driver. So a speaker with an upper cutoff-frequency between 40 and 50 kHz will most probably show more than 10 degress of phase-lag at 20 kHz due to the rolloff alone. This could be corrected electronically however.
10 degrees of phase-shift at 20 kHz is the same as around 0.5mm of sound travel through the air. I wonder how someone determines the point in space - where a wave originates from - at this accuracy.
OTOH I don't doubt that the mentioned design as such is a competent one.
Regards
Charles
10 degrees of phase-shift at 20 kHz is the same as around 0.5mm of sound travel through the air. I wonder how someone determines the point in space - where a wave originates from - at this accuracy.
OTOH I don't doubt that the mentioned design as such is a competent one.
Regards
Charles
chuck55 said:
good single drivers are not perfect
BUT they are time and phase coherent ENOUGH to fool our hearing
multiways are not
best!
graaf
all interested in those matters might find this interesting:
http://www.timedomain.co.jp/tech/tech_e.html
best!
graaf
http://www.timedomain.co.jp/tech/tech_e.html
best!
graaf
Re: Re: Re: Are single drivers really phase coherent?
what why?
why "not perfect"? or "why enough"? or why "are not"?
Lord_Humongous said:
what why?
why "not perfect"? or "why enough"? or why "are not"?
chuck55 said:
In any normal room with reflective surfaces, no. It's a discussion that has no importance in real room environments.
Re: Re: Are single drivers really phase coherent?
time coherence has importance in real room environments
I mean transient and waveform shape
therefore precedence (Haas) effect can work and we can talk to each other in reverberant environments
best!
graaf
tnargs said:
time coherence has importance in real room environments
I mean transient and waveform shape
therefore precedence (Haas) effect can work and we can talk to each other in reverberant environments
best!
graaf
Re: Re: Are single drivers really phase coherent?
True, true, as presented, false. They can be, but its design is no trivial pursuit for the casual DIYer and many well regarded pros argue it's not worth the effort, though judging by the fact that the grossly overpriced (IMO) world consumer market dominating speaker systems all use 'full-range' drivers to cover our acute hearing BW would seem to conclusively indicate otherwise, so as always YMMV.
GM
graaf said:
True, true, as presented, false. They can be, but its design is no trivial pursuit for the casual DIYer and many well regarded pros argue it's not worth the effort, though judging by the fact that the grossly overpriced (IMO) world consumer market dominating speaker systems all use 'full-range' drivers to cover our acute hearing BW would seem to conclusively indicate otherwise, so as always YMMV.
GM
Re: Re: Re: Are single drivers really phase coherent?
I think that they can be but only with regard to one specific axis
the problem is that only under unechoic conditions what we listen to is what goes on axis
under normal reverberant conditions we listen to total sound coming from every direction
and this total sound is not time coherent in case of multiways, even those multiways that are time coherent on a specific axis,
because those multiways are not time aligned off axis
in the result reflected transients and waveforms differ from the first transient and waveform and from each other - the resulting total sound is time incoherent, smeared
of course I am not certain but the above is what I think
best!
graaf
GM said:
I think that they can be but only with regard to one specific axis
the problem is that only under unechoic conditions what we listen to is what goes on axis
under normal reverberant conditions we listen to total sound coming from every direction
and this total sound is not time coherent in case of multiways, even those multiways that are time coherent on a specific axis,
because those multiways are not time aligned off axis
in the result reflected transients and waveforms differ from the first transient and waveform and from each other - the resulting total sound is time incoherent, smeared
of course I am not certain but the above is what I think
best!
graaf
Study the Unity concept horn and you will find it meets the criteria through our acute hearing BW which is about all the best 'FR' drivers can do.
GM
GM
graaf,
"because those multiways are not time aligned off axis"
That is an excellent point.
The direct sound is time aligned, but the off axis wall bouncing stuff is not. And I say roughly 70-80% of the sound you hear is the room swamping everything. My cat walked ear level behind me, and the change was dramatic. I think that is where a coax is off to a good start. Then time align it (think urei or use an active crossover with delay). That should be the cat's meow.
Norman
"because those multiways are not time aligned off axis"
That is an excellent point.
The direct sound is time aligned, but the off axis wall bouncing stuff is not. And I say roughly 70-80% of the sound you hear is the room swamping everything. My cat walked ear level behind me, and the change was dramatic. I think that is where a coax is off to a good start. Then time align it (think urei or use an active crossover with delay). That should be the cat's meow.
Norman
Time accuracy of the diffuse sound is not important IMO (and fullrange drivers wouldn't be good in this respect either). But the frequency response of the reverberant sound is important.
Regards
Charles
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