time delay problem JBL 4343 (3143 network)

[Tom Loizeaux]

Why not pull the 2405 out of the cabinet (temporarily blocking the hole), and put the 2405 on top of the cabinet. Then move it back in small increments to see if a better phase alignmemt is found? That, with bi-amping the woofers and setting any required delay on the active crossover to bring the lows in line with the rest, might help with your phase concerns.

Let us know.

Tom

[B&KMan]

Originally posted by Ian Mackenzie

I suppose it would be nice to have a perfect point source but as was explained by guru's in another thread, this can only exist for one sweet spot in time and space.

Ian

Bonjour,

well, yes and no this test is performed in couple of placement on axis and 30 axis with different lenght.

all result expose the same problem....

the point source of off time...

Originally posted by Ian Mackenzie

I think the focus was on flat amplitude response on axis rather than absolute phase at the time, flatness of response certainly more audible than phase shift.
Ian

the problem is not the spectrum response because in this question the response is not problem. The problem is the transient response and harmonic response. Floue, blur, fuuzy response. And the spacious response afected.

the first attack is drop over 20 DB before the second is start. the integration of HF & UHF is false but each peak analysing separately expose good phase response...

My litterature is explain the human ear is particulary sensible to phase shift... but many university recheard trace the line exact the variation of one is more perceive by variation of other...

I understand this monitor is a great. (I buy fo this reason)
But over 25 years of research if run foward many improvement. theS9800 is a astronoshing exemple of that...

Anybody have a complete spec of the cross-over 3143: slope, response driver, real cut frequency ???
Maybe I have a batch modified or wrong build...

[B&KMan]

Originally posted by Tom Loizeaux
Why not pull the 2405 out of the cabinet (temporarily blocking the hole), and put the 2405 on top of the cabinet. Then move it back in small increments to see if a better phase alignmemt is found? That, with bi-amping the woofers and setting any required delay on the active crossover to bring the lows in line with the rest, might help with your phase concerns.

Let us know.

Tom

Yeah this is the simple solution : put out driver and go back with in time integration is perfect but I start other big problem, blend with HF, stable fixing, space for good dispertion., cable, and E.T. look...

If you are any more tips in this way let me know...

[Ian Mackenzie]

B&K,

Can you post the time impulse to include scales and mark the UHF peak? so easier to read.

I have previously done near field time and response of individual drivers in 4345 4 way. I recall when only one driver being tested the time response was much cleaner.

It comes down to interpreting what the test results are telling us.
What are the peaks, what is causing them? What time gating are you using?

I might be able to repost my results if you are interested?
But I must have glass of Red first.

Ian

[B&KMan]

Originally posted by Ian Mackenzie
B&K,

Can you post the time impulse to include scales and mark the UHF peak? so easier to read.

I have previously done near field time and response of individual drivers in 4345 4 way. I recall when only one driver being tested the time response was much cleaner.

It comes down to interpreting what the test results are telling us.
What are the peaks, what is causing them? What time gating are you using?

I might be able to repost my results if you are interested?
But I must have glass of Red first.

Ian

Well, eastern time is 23:10 and I tried to give info soon.

For little explain the dual channel analyser is syncronised with internal generator... the gate is simple max peak detector - 10% is applied on channel A
The generator is connected with T bnc of channel A and channel where test interest. the channel B is receive the response via preamp an mic.

The rectangle weighting is applied on this impulse signal at channel A and B

Because time delay is automatiuely non syncro the analyser permit to delay response on each channel for perfect syncronisation.

Finally the original response is compared by the second with completely automated taste and response H1 is produce. well in this case this syncronisation is not critical for expose the 2 peaks. But for complete analyse it is important...

But for determine what is what the analyser accept to weighting transient window. In this any time and size of time is manual calibrated by user and reveal by analysing function.

The first step is the response of UHF.

My second pict expose the delta x is intervale and delta y is the difference in Db of the peak comparison.


euh it is too hermeneutic explanation??

I have no problem to send more pict but long process in this forum restriction... let me know.

and I open to send pict for your test.

the exchange build concrete of this forum

[B&KMan]

I hope this more picture is help more your mind to realize the phenomenon.

this pict is ruff analyse of the fisrt peak.

[B&KMan]

this pict is ruff analyse of the second peak.

[B&KMan]

Finally this pict explain mesure set -up
each Line of time analyse is value of 15.3 US time.

Sorry for poor pict.

It is better comprehensive ???

oups it is time for me to replenish the second solution (red wine)




p.s. 1 --- the signal generator is one pure positive square pulse.
the spectrum response is a line !! If you have more curious I send pict of this...

P.S. 2--- it is easy to buid spectrum in the same way with near field mic.
I have no problem to buid this analyse too if you interest. And Yes the UF is go up to over the cut off frequency cross-over.

[Ian Mackenzie]

Very interesting and clever.

Here is my PC analyser reference pulse.

Ian

[Ian Mackenzie]

This one the UHF only.

Near field .

There is some blurr on the tail edge, this could be the system, noise from the amps ect or possible ringing from the crossover.

Ian

[Ian Mackenzie]

The UHF and Horn .

The combined effect of the delays and other crap shown here.

I have no doubt with better equipment I could evaluate this better. Third order filters do suffer poorer transient performance than say first order so it is likely there is some transient distortion. But whether that's audible over other compromises with these designs is another issue.

In some respects the 4430/35 has a better crossover characteristic as it has miminal group delay according to the white paper. But that ain't the whole story.

B&K, elsewhere our member 4343mod has used a modifed 1st order passive network for the 4343 and claims startling results although this would not solve the time domain issues of the UHF driver. No doubting it would sound different but such a dramatic change to the network may create other compromises such as dispersion lobes and limited power handling in some circumstances.

Ian

[B&KMan]

Thanks very mch for info too.

cool stuff.

What exactly rate intervale ??
the little inconsistence is origine of the type of weighting filter for this type of input signal. Normally the hanning is overal best filter but for pulse it is preferable to run in rectangular filter for rectangular signal ... (according to many tech note on Bruel & kjaer. but maby is different for this software...)

Do you have possibillity to expose the imaginary part of signal ??

This is my pict of my UHF

[Ian Mackenzie]

What exactly rate intervale ?? The sample length is defined by the control panel as is the sample length.

I will check the authors web page for more details, this is a very simple package that used a soundcard to generate the pulse and do the FFT functions. Tim G has a better package , perhaps he is following this thread he can run a similar test.

Ian

[Bill Shenefelt]

Might another approach be to run the horn and slot radiator on a single amp and the midbass on a second one and the bass on a third? The way the physical configuration is right now is with the 15 inch in a 6 cu ft enclosure like an L300 laying on its side (It was the same box I had used in the home built L300) A second box about 15 inches square on the front face contains the 10 inch midrange. It just lays on the bass box. The face of the box for the 10 inch is extended vertically upward and free air mounted to that face are the horn and slot radiator. These could be moved rather than using an electronic delay.
My main problem right now is that after I changed from the 3 way design of the L300 to the 4 way design incorporating the 10 inch midbass the system sounded "warmer" but lost the great punch it once had. I thought a mismatch of the crossover from 15 inch to 10 inch was the culpret. The 15 could no longer go up to 800 cps and possibly provide the leading edge of the waveform. This is just what I imagine to be happening.
I do have coming to me a 3 way crossover from Marchand currently configured for either a 300 or 400 cps 24/ocatve for the cone speakers and provisions for adding a 1200 cps crossover for the cone to horn interface. Looking for the best way to set it up right now. I want to recover the nice punch I had with the L300 setup, yet keep the warmth I get with the 10 inch. All drivers and passive crossover design and parts are from the 4343 but I have no 4343 15 to 10 inch cone passive and wanted to use active there if beneficial. With my age and ears I cant hear much from the slot readiator anyway.

I'm just wanting to be clear here- so, the bigger of those two spikes on the time response curve, is ALL THREE of the other drivers in the 4343 stacked up on top of each other, ie, the midrange horn, the midbass and the woofer? If so, that's pretty remarkable... that would very consistent response from drivers of different mechanical acoustic centers.

My suggestion, might be to seperate JUST the 2405 from the other three drivers- run a tri-amp setup- with the 2231/2235 woofer on one amp, the 10" midbass and mid horn on one amp, and the 2405 on a third amp. Then, use a digital time delay, to delay the 2405 .67ms. That shouldn't be too terribly hard- all you'd have to do, is seperate the 2405's crossover section from the rest, and just run another amp from a time delay unit for just that tweeter and crossover...

[Chas]

Bill, this should not be a problem. Per my PM earlier today, I moved from three ways to four way 4345's and certainly found nothing missing in this department.

If I recall correctly, the 2122H's in my 4345's need to be installed in 0.5 cu.ft. enclosures for optimal transient response. Mine have a light fibreglass fill, covering the rear and all sides. I think it's about 0.5 to 1" thick. What box volume and fill are you using?