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[Ben Heavenrich]

I would not use the 52dB highpass.

While it "kinda sounds" like a good idea-there are problems associated with very steep slopes.

For the most part I stay with 24dB or less.  Yes one of our products has a midrange slope of 30dB, in order to get the phase to line up.

I would also lower the freq.  35Hz is pretty high for the TH118.  If you are really going to slam it-then maybe 30hz.

With the sub in the middle-the best you can get is a "general" setting for the delay. 

If you are in the middle-then you need a longer delay time.  But as you move towards the sides-the delay time gets less and less.

So you have to choose a "middle road" setting and live with it.

Are you highpassing your tops with the DSP?

With the relatively high..high pass frequency I was trying to take some stress off the amp. That was my thinking. I will lower it for the future.

Yes the tops are crossed over at the same frequency and slope as the subs low pass.

Is RTA software the only way to properly phase align a system?

[Ivan Beaver]

With the relatively high..high pass frequency I was trying to take some stress off the amp. That was my thinking. I will lower it for the future.

Yes the tops are crossed over at the same frequency and slope as the subs low pass.

Is RTA software the only way to properly phase align a system?

Yes raising the high pass can take some strain off of the amp-but at the sacrifice of low freq extension.

An RTA does not give any phase information-so it is pretty much useless for getting a good alignment.  But if it has enough resolution (in freq and level) it could be better than nothing-but you have to be careful.

And like I said-there is NO WAY to get a good phase alignment with the sub in the middle-at least at more than one location

[Mark McFarlane]

...
And like I said-there is NO WAY to get a good phase alignment with the sub in the middle-at least at more than one location

Well, maybe 2 locations.

[Ivan Beaver]

Well, maybe 2 locations.

Yes you are correct------

There you go getting all "technical on me".

[Scott Carneval]

With the relatively high..high pass frequency I was trying to take some stress off the amp. That was my thinking. I will lower it for the future.

Yes the tops are crossed over at the same frequency and slope as the subs low pass.

Is RTA software the only way to properly phase align a system?

If you cross the top and sub at the same frequency you probably have quite a bit more overlap than you think.  Most people run their subs quite a bit louder than their tops, sometimes by 10-15db or even more.  For instance, if your subs were run 24db hotter than the tops, and you're using a 24db per octave crossover, then the ACOUSTIC crossover (the frequency where the two sources are at the same level) is going to be a full octave higher than the ELECTRICAL crossover (the number you're entering into your DSP).  If the two sources aren't phase aligned at the acoustic crossover point then you're likely to experience cancellation.

What sub were you using before this?  Can you connect it and compare A/B? 

[Mark McFarlane]

Yes you are correct------

There you go getting all "technical on me".

Well, it depends...

[Ivan Beaver]

If you cross the top and sub at the same frequency you probably have quite a bit more overlap than you think.  Most people run their subs quite a bit louder than their tops, sometimes by 10-15db or even more.  For instance, if your subs were run 24db hotter than the tops, and you're using a 24db per octave crossover, then the ACOUSTIC crossover (the frequency where the two sources are at the same level) is going to be a full octave higher than the ELECTRICAL crossover (the number you're entering into your DSP).  If the two sources aren't phase aligned at the acoustic crossover point then you're likely to experience cancellation.

What sub were you using before this?  Can you connect it and compare A/B?

And that would be assuming that the speakers in question are both flat for an octave or so above and below crossover-which is almost never the case.

Most subs get louder as you approach crossover (as compared to an octave below crossover).

So the actual response is often QUITE different than most people "think" it is.

[Mark McFarlane]

Yes you are correct------

There you go getting all "technical on me".

Actually, to be technically correct, given point source tops and subs, there should be two planes where the alignment is correct, resulting in two lines intersecting the audience seating area, not necessarily where you would expect them if the tops are flown.

OK, I should have gone to bed hours ago,...

[Ben Heavenrich]

And like I said-there is NO WAY to get a good phase alignment with the sub in the middle-at least at more than one location

So with respect to delay, the th118 should be treated as a front loaded sub and the horn length doesn't matter?

..or, do you need to compensate for the length of the horn? Does it not matter with a tapped horn because the driver is close to the mouth?

With regards to the crossover, the literature with my BSS processor says that the dsp compensates for phase differences at the xover point..provided the amp levels are set correctly. Are they set correctly? Other then using my ears, I really don't know. I am relatively new to the complicated processing aspect of sound reinforcement because I'm used to using powered stuff with built in dsp and what not.

Thanks guys for your help! 

[Ivan Beaver]

So with respect to delay, the th118 should be treated as a front loaded sub and the horn length doesn't matter?

..or, do you need to compensate for the length of the horn? Does it not matter with a tapped horn because the driver is close to the mouth?

With regards to the crossover, the literature with my BSS processor says that the dsp compensates for phase differences at the xover point..provided the amp levels are set correctly. Are they set correctly? Other then using my ears, I really don't know. I am relatively new to the complicated processing aspect of sound reinforcement because I'm used to using powered stuff with built in dsp and what not.

Thanks guys for your help! 

I did not say that at all.  It does not matter whether you use a horn or a front loaded subs-as you move around the delay times will be different.

Yes a horn loaded sub will require a longer delay time than a front loaded sub.

Your processor may account for phase differences at different freq (I have never used it so assuming you are correct), but how does it know what the phase response or amplitude of the actual speaker is?

Are you talking about the ELECTRICAL or ACOUSTICAL crossover points?

Remember that if you change the levels of either the sub or the top the acoustical crossover points will change-which means possibly the electrical crossover points will also change.

It is VERY RARE that you would use the same high and low pass filters for a particular freq.

Yes that is the way analog crossovers were designed (except for a few exceptions-like the Crown stereo crossover)-because it was easier and cheaper and offered less chance for a user to "screw up".

If the amplitude is different at different freq (as most are), then different crossover freq would be needed for different subs.

Just because a unit has a built in DSP does not mean that it is proper.  Only for a particular sub and top setup.  Change either one-or the quantity and the crossover points need to change.

At least to make it right.  But some people don't care about it being "right".

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