Are single drivers really phase coherent?

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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
 
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
 
Re: Re: Are single drivers really phase coherent?

tnargs said:


In any normal room with reflective surfaces, no. It's a discussion that has no importance in real room environments.

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?

graaf said:


good single drivers are not perfect

BUT they are time and phase coherent ENOUGH to fool our hearing

multiways are not

best!
graaf


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?

GM said:

True, true, as presented, false. They can be

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
 
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
 
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