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hifiapart
04-22-2009, 02:56 PM
Hi,
Does anybody know if this works in cases when the coils cannot be aligned? The cabinet I will be making will not allow physical alignment of the coils.
Thanks
Tim

38754

Loren42
04-22-2009, 03:56 PM
Hi,
Does anybody know if this works in cases when the coils cannot be aligned? The cabinet I will be making will not allow physical alignment of the coils.
Thanks
Tim

38754

I guess you can try it both ways and see if you can hear a difference.

The issue is more complex than described and there are a number of factors at work. In a nutshell, what happens is that when near the crossover frequency two competing drivers can interfere with each other.

In reality, there is more going on than simply that and the crossover will introduce a lot of phase mismatch as well as time-alignment issues due to different distances from the driver's voice coils and the listener.

There is also baffle diffraction and center-to-center distances to consider between drivers. Ideally, that distance should be less than one wavelength at the crossover frequency.

So, the answer is not simple and requires a lot of data and number crunching to determine what the end effect will be. The easiest way to determine the right method is to try both and see which performs better.

1audiohack
04-22-2009, 06:52 PM
I always wondered why the physical alignment of the voice coils of non identical drivers would insure you of anything?

Consider three woofers that can be made with the same basket and motor magnet assemblies from the electrical side.

E130, 0.466mH
2225, 1.1 mH
2235, 1.25 mH

Subject all three to an impulse test like MLS and the E130 will win with the 2235 coming in last.

Same physical dimensions, three acoustic centers, sometimes even behind motor assembly due to the inductive delay.

How fast is say a 2450 compression driver with a series L of only 0.120mH?

You would need the 2450's voice coil well behind the voice coil of a 2235 to get the pair phase coherent with out some other way to control delay.

The deeper you dig the worse it gets.

JBL 4645
04-22-2009, 08:30 PM
Wouldnít you use an (oscilloscope) in this situation to test it directly to the electrical leads, leading to the speaker driver elements? Then look for any shift in the wave form on the scope for normal or inverted phase?

1audiohack
04-22-2009, 10:28 PM
A two or more channel scope can show you if two signals are in or out of step one to another and to what degree in the electrical domain that's true.

Looking into the acoustical domain for time information is a bit more complex.

Absolute polarity (some say it's a fools errand) and phase coherency can be maddening even with active crossovers with delay and dedicated measurement equipment. Get it right first and the rest is much easier.

Allanvh5150
04-22-2009, 11:16 PM
Having the voice coils in the same plane ensures that the time domain of the signal is the same. At the crossover point each speaker produces the same frequencies. If one of the drivers is moved forwards or backwards by half a wavelength,the speakers will be 180 degrees out of phase. Reversing the phase of one of the drivers will put them back in phase. But there is another problem to think about. If a passive crossover is used the phasing problem is not quite so simple. Generaly the woofer will have its signal pass through an inductor so the phasing will be 90 degrees lagging. The mid range driver will have the signal running through a capacitor so the signal will be 90 degrees leading. This makes the 2 drivers 180 out of phase. To cure this simlply swap the wires to one of the drivers. There are not a lot of cabinets on the market that are time alligned. Horns are generally long and years back that didnt present a problem because the midrange cabinets were equaly long. The next problem is when you try to time allign a tweeter sitting on the top of the whole pile. Basically impossible.

To be honest you should just listen to the system and then change the phasing and listen again. Decide for yourself which way is more pleasing to the ear. It doesnt have to be correct, it only needs to be to your liking.

Allan.

Hoerninger
04-23-2009, 04:42 AM
To be honest you should just listen to the system and then change the phasing and listen again.

It is easiest done with female voices or pink noise.
____________
Peter

spkrman57
04-23-2009, 08:44 AM
If you must use a different spacing and reverse the polarity of the horns which I have done many times the following is a rough guide.

For 800hz crossover: Distance between the voice coils should be approx 1/2 wavelength, 8 1/4" between each other and then reverse the polarity of the HF horns.

For 1.6khz crossover: 4 1/4" difference.

The formula I use (and there is much discussion of what the exact formula according to the experts is): 13,500 / frequency = 1 wavelength in inches. So you divide the wavelength in half and use that figure.

Hope this helps.

Regards, Ron

JBL 4645
04-23-2009, 10:22 AM
If you must use a different spacing and reverse the polarity of the horns which I have done many times the following is a rough guide.

For 800hz crossover: Distance between the voice coils should be approx 1/2 wavelength, 8 1/4" between each other and then reverse the polarity of the HF horns.

For 1.6khz crossover: 4 1/4" difference.

The formula I use (and there is much discussion of what the exact formula according to the experts is): 13,500 / frequency = 1 wavelength in inches. So you divide the wavelength in half and use that figure.

Hope this helps.

Regards, Ron

Distance between the voice coils, hmm. what about JBL control 5? Do you use the short distance within the size of the speakers voice coil distance the long delay from speaker to listener. I mean the flipping manual doesn’t tell you much apart from riddles!?

I don’t get it, I’m no hot on mathematics but I do catch on sometimes. What is the equation figure to determine distance?


A two or more channel scope can show you if two signals are in or out of step one to another and to what degree in the electrical domain that's true.

Looking into the acoustical domain for time information is a bit more complex.

Absolute polarity (some say it's a fools errand) and phase coherency can be maddening even with active crossovers with delay and dedicated measurement equipment. Get it right first and the rest is much easier.

Yes, yes but has it ever been achieved in say cinemas where stage speakers are not likely to be moved around like live PA I prefer the speakers staying PUT!

Hmm, how would I go about tackling this? What’s the easiest method of approach pink noise or sine wave tone that’s going to stay still pending on background noise exciting the microphone? The tone would be far stable to watch as you switch from normal to invert while looking at the RTA for phase shift up or down. down is out-of- phase, up is in-phase. Or steady straight line?

I was mucking around a few years ago with my first active crossover and patched the LF and HF into the Technics SH-8055 with lower the HF I can see it falling away from the LF signal on the RTA.

Now if I was to make a two leads for the DCX2496 as the ends have XLR on the end for the Alesis RA300, wait a second!!!

Are I have the HF XLR to RCA phone for HF for the Marzntz 1050 amps I can switch the leads around and plug them into the SA-8055 and adjust the phase though 0 to 180 or the polarity while using pink nose or sine wave.

Ok, going to try this out back in jiffy.

JBL 4645
04-23-2009, 10:42 AM
That didnít take long. Yes there is noticeable difference when switching phase up and down or switching polarity. Even the time delay shows an up and down change even thou the delays are set for distance in the room for centre LF/HF there is difference in change.

Itís going to be dicey with the in-room RTA what with the noisy background from traffic outside, the low end will be rising each time in the 25Hz to 40Hz range. :banghead: Might try this later around midnight when it quietens down a bit.

I wouldnít have thought about doing this if I hadnít noticed this thread.

I was tinkering around a few nights ago with steeper Butterworth -48db at 1Khz LF high end cut and Butterworth -18db for HF result less harshness for now, also tinkered with delay on right front HF as the stereo was giving me good left sound panned effect Star Trek the motion picture original 1979mix, when Scotty, presses a button on screen left.

When in Dolby stereo the effect was kinder lost on the HF, then it clicked why not delay the right HF and after setting the distance it worked like magic. That effect has always bugged me for years and without the DCX2496 Iíd still be trying to figure it out?:bouncy:

hifiapart
04-23-2009, 10:45 AM
JBL465,
Glad this got into that direction, like to know how it comes out.

As for me I am picking up my 416-8-A's, 288-16-h's, Mantaray 64's and xovers tomorow....cannot wait!

I have some questions on the 288-16-H, any info on that (posted thread here asking also)

Tim

JBL 4645
04-23-2009, 11:25 AM
JBL465,
Glad this got into that direction, like to know how it comes out.

As for me I am picking up my 416-8-A's, 288-16-h's, Mantaray 64's and xovers tomorow....cannot wait!

I have some questions on the 288-16-H, any info on that (posted thread here asking also)

Tim

You bet. Will do for better or worse LOL

Well as soon as the noise background level drops down at midnight as this noisy road with speeding cars breaking the law, the limit is 30MPH! Not 60MPH! Plus the Bournemouth yellow buses that stop across the road is visible on the RTA at 25Hz on the Technics RTA and worse on spectrumlab that shows 20Hz or lower sigh.

What is the best place to put the microphone in this case. Pointed horizontally at the speaker mid way point between bass mid and HF tweeter?

Or placed vertically upright about the same position?

CONVERGENCE
04-23-2009, 01:18 PM
JBL465,
Glad this got into that direction, like to know how it comes out.

As for me I am picking up my 416-8-A's, 288-16-h's, Mantaray 64's and xovers tomorow....cannot wait!

I have some questions on the 288-16-H, any info on that (posted thread here asking also)

Tim

Hi .How to figure out if diaphragm is in phase?

Don't laugh!

You take a cleanex put it in front of the driver . Now take a 1.5 volt battery and apply a current . If the cleanex blows away from the driver
you have found which terminal is + and which is minus and your in phase.
If the cleanex tissue goes in your out of phase.

There is no other way.
.................................

JBL 4645
04-23-2009, 01:38 PM
Hi .How to figure out if diaphragm is in phase?

Don't laugh!

You take a cleanex put it in front of the driver . Now take a 1.5 volt battery and apply a current . If the cleanex blows away from the driver
you have found which terminal is + and which is minus and your in phase.
If the cleanex tissue goes in your out of phase.

There is no other way.
.................................

:wtf: Is anyone buying that story?

Iíd lay off the crack cocaine for at least month until youíre clean.:D

JBL 4645
04-23-2009, 05:39 PM
Hmm, now that its quite free from traffic noise!

I’ve set the crossover for LF bass mid on the higher end to full, instead of 1Khz I’ve set to 20Khz or full.

While listening to pink noise between the LF and HF that is set at 1.38Khz level is set close enough to 0db on the SPL db meter 0db or 70dbc and with both LF/HF summed with an increase +3db.

Inverted it dropped by -2db.

It was disorienting doing “the couching tiger itching dragon” in front of the speaker while pink noise played. It kinder shifted the tone or pressure on one of my ears left side. I guess this was due to the tweeter being off-set to right on the control 5, not that I have problem with that.

I sat down and shifted the phase up and down with slight appearance the high end tweeter it was as if it shifting towards the middle of the baffle enclosure. It’s an illusion!

I haven’t gone thou the delay process as of yet, I’ll tinkering around with it later in the early morning hours. Oh the peace and quiet of stillness is bliss, oh a nice countryside village would be nice.:)

I’m using Star Trek original series “The Man Trap” for differences in the slight changes as it has some fascinating sound effects and voice dialogue.

The display on the SH-8055 so far looks flat enough apart from a few minor peaks at 1KHz and 2KHz.

I’ll EQ these down later providing I have enough EQ filters left on the DCX2496. The polarity switching from (normal to inverted) shows positive difference in drop when switching to inverted.

CONVERGENCE
04-23-2009, 07:02 PM
:wtf: Is anyone buying that story?

Iíd lay off the crack cocaine for at least month until youíre clean.:D


Both speakers should be either pushing or pulling especially with surround speakers in a theater so that the whole system is in phase.

If one cabinet's polarity is reversed in the system then you will have a problem.

Time alignement if active crossover the better.

Any way you need time alignment with your surround speakers.

This is not rocket science.
.....................

Allanvh5150
04-24-2009, 01:35 AM
Both speakers should be either pushing or pulling especially with surround speakers in a theater so that the whole system is in phase.

If one cabinet's polarity is reversed in the system then you will have a problem.

Time alignement if active crossover the better.

Any way you need time alignment with your surround speakers.

This is not rocket science.
.....................

Are you talking of "time allignment" or delaying the surrounds so the sound reaches the listening position at the same time as the fronts?

Allan.

Allanvh5150
04-24-2009, 01:38 AM
Hi .How to figure out if diaphragm is in phase?

Don't laugh!

You take a cleanex put it in front of the driver . Now take a 1.5 volt battery and apply a current . If the cleanex blows away from the driver
you have found which terminal is + and which is minus and your in phase.
If the cleanex tissue goes in your out of phase.

There is no other way.
.................................

Out of phase with what?:blink:

CONVERGENCE
04-24-2009, 07:15 AM
Out of phase with what?:blink:

I should have read the entire thread .

out of phase with the woofer for example.

It,s just a technique when you have your drivers fixed or repaired to make sure that he rewired the thing the right way.

Reconers are very busy and they wil tell you to do the test at home to make sure.

That's all.

Especially here with the head quartes of Le cirque du soleil etc in Canada.

All equipment is purchased in Canada.

..........

JBL 4645
04-24-2009, 09:03 AM
Both speakers should be either pushing or pulling especially with surround speakers in a theater so that the whole system is in phase.

If one cabinet's polarity is reversed in the system then you will have a problem.

Time alignement if active crossover the better.

Any way you need time alignment with your surround speakers.

This is not rocket science.
.....................

Yes, yes, yes I know about the bat 1.5v placed on the terminals and cone moving forwards.

I have time alignment on the AVR its not perfect like DCX2496 would be but it will be sorted soon as soon as I get the money. Iím not rich bugger just a poor bugger that likes to listen.:bouncy:

JBL 4645
04-24-2009, 09:24 AM
Out of phase with what?:blink:

I think he means the thread is out of phase. We’re all out of phase. Must be the climate?:D


Are you talking of "time allignment" or delaying the surrounds so the sound reaches the listening position at the same time as the fronts?

Allan.

If you played the AVR into an audio mixer use a single channel to monitor say the centre channel for argument sakes.

Set the SPL db meter up play the pink noise cycle balance each channel as it cycles around for the same weighting db level say 70dbc argument sakes.

Buy the time you’ve balanced all the levels you wouldn’t be able to tell which is LCRS unless you looked at the AVR indicator display that shows which pink noise is playing on which channel.

If you changed the level of one channel it will stick out!
If you changed the phase of one channel it won’t really show up!
If you applied a little EQ say some high or low range it will stick out!

If you played an all channels pink noise signal from a set-up 5.1 DVD or CD dts calibration disc.

Note all the pink noise that is sent from LCRS into the mixer has been balanced by switching off each channel and insuring that each channel is at 70dbc when adding them all up it doubles. Okay now easy the level down so it reads 70dbc.

Now apply some phase shift change, you should be able to notice the pink noise going up and down.
Switch polarity of one of the channels you will hear and notice the SPL db meter dropping by a few db.

Plug the AVR outputs into the line inputs on the audio mixer and use the monaural output plugged up to an amp to centre channel front.

Now go and try this. Have fun!:):bouncy:

Allanvh5150
04-24-2009, 01:07 PM
I don't have to worry about such things. My amp takes care of time allignment and levels all on its own. All I need do is setup a mic and run a one minute test. It will even tell me if a cabinet is out of phase. Simple!

Allan.

robertbartsch
04-24-2009, 01:59 PM
Physical alignment of the VCs in a verticle array was probably first discussed in a Stereo Review article in the early 1970s. Soon afterward, you saw consumer products comming to market with this space-age feature.

I was so impresed with this concept that I took my VOTT components out of the factory boxes and built phase aligned boxes.

In reality, I never saw any advatage and, to me, it was a bunch of marketing hype. A few months after the experiment was completed the components returned to the original furniture grade boxes where they stayed for the next 30 years.

JBL 4645
04-24-2009, 04:11 PM
I don't have to worry about such things. My amp takes care of time allignment and levels all on its own. All I need do is setup a mic and run a one minute test. It will even tell me if a cabinet is out of phase. Simple!

Allan.

Same with DCX2496 auto alignment it sends short bursts of pink noise to left LF left HF centre LF centre HF and right LF right HF. It also adjusts distance and polarity if a speaker happens to be wired out incorrectly.

JBL 4645
06-20-2009, 01:21 PM
Recapping the phasing thingy I was retesting two-days ago with steady sine wave lowered the levels of each LF and HF tested the sine wave one at time noted the level on the SPL db and to my surprise when un-muting one the other the level dropped down. Out-of-phase.

So a quick press of the button on the DCX2496 HF to correct the polarity. I could also hear the level difference with 1KHz 2KHz and even 8KHz by winding the LF up to allow the highs seep out or register on the SPL or before audible.

Anyhow I’ve sorted that and I was certain it was checked-out months ago unless I being switching cables around???

Also I’m thinking about doing a video to show how it would sound maybe tonight then again maybe tomorrow.



I think he means the thread is out of phase. We’re all out of phase. Must be the climate?:D



If you played the AVR into an audio mixer use a single channel to monitor say the centre channel for argument sakes.

Set the SPL db meter up play the pink noise cycle balance each channel as it cycles around for the same weighting db level say 70dbc argument sakes.

Buy the time you’ve balanced all the levels you wouldn’t be able to tell which is LCRS unless you looked at the AVR indicator display that shows which pink noise is playing on which channel.

If you changed the level of one channel it will stick out!
If you changed the phase of one channel it won’t really show up!
If you applied a little EQ say some high or low range it will stick out!

If you played an all channels pink noise signal from a set-up 5.1 DVD or CD dts calibration disc.

Note all the pink noise that is sent from LCRS into the mixer has been balanced by switching off each channel and insuring that each channel is at 70dbc when adding them all up it doubles. Okay now easy the level down so it reads 70dbc.

Now apply some phase shift change, you should be able to notice the pink noise going up and down.
Switch polarity of one of the channels you will hear and notice the SPL db meter dropping by a few db.

Plug the AVR outputs into the line inputs on the audio mixer and use the monaural output plugged up to an amp to centre channel front.

Now go and try this. Have fun!:):bouncy: