My ears must be rubbish I cant hear Crossovers

[oublie]

Hi folks,

I've been running a few tests with my computer on the way to building my open baffle line arrays.

The prototype is currently using 12 4 inch full range drives as mid woofers and at the moment im crossing to a single 1 inch silk dome tweeter. The final product will use 20 4 inch drives per side along with a narrow electrostatic panel. Sub duties will depend on how the final measurement pan out regarding low frequency extention.

I'm crossing over electronically at 2.5khz - this will change to 1.5 khz once i sort out the electrostatic tweeters.

My tests use a 4th order crossover and i've tried my best to hear what issues i would have with crossing over in the main audio region and as yet can't hear the crossover.

I know some of you golden eared type can tell the difference but i just don't seem to be able to.

I've tried running the 4 inch speakers full range but they lose a lot of sparkle above about 3 - 4 khz (probably comb filter related) so i definately need some form of treble augmentation.

So the questions are what am i actually listen for and what is it that i can't or can hear but am not noticing, also is there really that big of an issue crossing over in the 100hz to 3khz audio band line array comb filtering issues aside.

[Pano]

Sorry, what do you mean you "can't hear the crossover"? Are you talking about the low pass filter on the 4" mids, or the high pass filter on the dome tweeter, or both?

You say the 4" speakers loose sparkle above 2-4Khz. Don't you hear even less sparkle out of them with the crossover? A 2.5KHz LP should be very easy to hear - at least on a 4" driver.

Or do you mean that you can't hear a difference if you shift the crossover point and/or slope?

[oublie]

I'm doing this all through computer based active crossovers with independant amplification so i'm able to adjust crossover points for low pass and high pass on the mid and the tweeter i can hear the difference to the sound when i change the frequency of the crossover particularly when i listen to the 4 inch full range but a lot of people have indicated that it should deteriorate the sound if i'm crossing over within the main vocal band i.e. 100hz to 3khz but i'm just not finding this.

is it me or is this perfectly normal?

[event horizon]

What type of 4th order filters are you using? If they are Linkwitz Riley then you shouldn't have any real phase problems as the two sum. With 4" drivers the voicecoils of the 4" units won't be much further from your listening position than a tweeters voicecoil so you might not need to give much in the way of delay (if at all unless you want absolute accuracy) to the tweeter so all radiate in phase.

In fact with the amount of drivers you are suggesting then unless you have each 4" drivers voicecoil exactly the same distance from you at the listening postion there really isn't much point in going overboard time aligning things

Our ears are most sensitive to stuff between about 1 - 4Khz. I had an MTM speaker with 1.5KHz xover time aligned (active xover Linkwitz Riley) & the things were quite scary in their realism even with 5 1/4 bass/mids & 30mm inverted kevlar Focal tweeters. I'll never forget them

[Pano]

Ah, OK....

If your crossover is good, then it won't hurt the midrange enough to notice. In fact, it will probably help it. You need to cross the drivers where they work best - not where you "think" they will sound best or where some vague rule says you should cross them. It took me years to get past that hurtle.

It is true that it can be very easy to hear crossover changes in the mid-band. I find 1KHz to be very tricky. Any small change is easy to hear. Buy get it right, and it's right.
A crossover outside the 100Hz-3KHz range could be just as bad, but you won't be as sensitive to it.

FWIW, I presently cross at 500Hz and 6KHz and it works just fine. I'm surprised that your 4" drivers don't play well higher than 3K, but as you say it may be the comb filtering. You may be able to simulate comb effect that in The Edge software.
Home of the Edge

[oublie]

Thanks Folks,

Looks like I must have good crossovers

I'm going to be crossing over around the 1.5 to 3k mark dependant on tweeter results once the electrostatic panels for the tweeters are built. I'm currently using a single 1" silk dome for testing purposes so the crossover point may change dramatically.

I'm currently listening with a 3k crossover point that so far seems to be optimal. This contradicts the midrange comb filtering calculations which indicate a crossover below around 1.7k but hey they are my speakers and my ears so calculation isn't everything .

I've used edge before and it's very good although as it's not driver specific it doesn't show the whole picture I may have to invest in basta.

[Pano]

True... But by putting in the cone size and spacing into Edge (or Basta) you should get an idea of the comb filtering at a given point in space. Nice because you can move the mic to see what distance and off axis does.

I think you'll see that real drivers, with real cone area, comb filter less than point sources at the same center to center spacing. That may push your possible crossover point up higher.

[jerryo]

Hi oublie,
are you using the 4" Wharfedale full range drivers that were on sale on ebay some time back? If so, I will be interested to see how you rate them when you finish your line array. I have the same drivers but only allowing 12 for each channel, and I will probably use a high efficiency pro tweeter to augment the frequencies above 3-4000 Hz and using a simple passive crossover for this and bass duties below 150 Hz.
Good luck with your project.

[chris661]

Most people think they can't hear the difference between crossovers. Get it (seriously) wrong, and you'll know about it. The closer it gets to "right", the less offensive the original problem will be. The problem will still be there until you've got it right, it will just get harder to notice as you get closer.

I find that sometimes you need to know exactly what the problem sounds like before you know it's there.

[oublie]

Originally Posted by jerryo

Hi oublie,
are you using the 4" Wharfedale full range drivers that were on sale on ebay some time back? If so, I will be interested to see how you rate them when you finish your line array. I have the same drivers but only allowing 12 for each channel, and I will probably use a high efficiency pro tweeter to augment the frequencies above 3-4000 Hz and using a simple passive crossover for this and bass duties below 150 Hz.
Good luck with your project.

Yes, i have 64 of them

I'm building an open baffle cone and electrostatic surround sound system.

20 per side for the mains, and eight for the centre and 2 rears.

4 inch wide electrostatic panel for highs

and twin 20 ish inverted tapped horns.

this all may change as i tweak more and more.

bass isn't bad down to about 60 or 70 hz but needs augmentation.

I find there not much in the way of highs above 5k in a line array.

I have the original thiele small parameters for them if you need em.

btw i've tried them with and without the rear shielding the seem to have a higher qts without the shield so perform a little better in an open baffle.

btw you won't need more than 20w into the array even with 12 of these