Rational Acoustics

September 9th, 2014, 03:28 PM
Hopefully this is a simple question. Sorry at the moment I can't post any screen shots. The computer is packed away in my trailer.

I have had no problem working with my previous subs ( aligning them with tops). They were just double 18 br subs. Maybe I just got lucky. I built 4 th subs to use with my live rig. Went to align them with tops and I'm getting a large dip at the crossover. I'm guessing it's because the graph for the phase shows that the tops and subs don't have the same angle ( I'm new at this so I could be wrong). I was systematically changing things till I figured out what would change that angle. This got got cut short due to angry people in surrounding houses.

I can get them to overlap at crossover with delay but what changes the angle to overlap. Sorry I'm guessing this is very basic but I have to make my next test day a little shorter than this one that's why I'm asking here.

I know more info is always better so tell me what if any you need and I'll be happy to share. What I can tell you is the angles both fall the same direction but the sub angle was far steeper then the tops.

Again sorry if this is basic knowledge. But any help would be very appreciated. Thanks

Timo Beckman
September 10th, 2014, 04:44 AM
You have to synchronize Smaart ("find" button in transfer mode) on the system (subs+tops).
After that take a solo trace on the tops and a solo trace of the subs without changing the Synchronization delay (you want to align the subs to the tops so do not try to synchronize on the subs via live IR).
If the phase angle of the traces in the x-over area do not match the trace that has a less steep angle then the other is the one that has to be delayed.

September 10th, 2014, 01:08 PM
I did that. I found the correct delay for smaart. I am using transfer function not ir. I guess where I'm lost is I can get them to overlap by delaying my subs. The problem is the traces don't lineup angle wise does this matter. I'll have this computer out again Saturday I can take a screen shot than. The sub has a steep drop left to right top has a gentle slope left to right. I thought I remember reading that the angles should line up near the crossover. I was just trying to verify if that's correct. If it is how do you manipulate the angle. Thanks again for the response I should have given more info sorry.

Chris Tsanjoures
September 10th, 2014, 01:40 PM
The problem is the traces don't lineup angle wise does this matter. I'll have this computer out again Saturday I can take a screen shot than. The sub has a steep drop left to right top has a gentle slope left to right.

Are they the same slope at crossover? that is the area you are concerned with most - the 'hand off' of broadband to sub. The different angles may be a result of different order HPF/LPF settings on the processor.

September 10th, 2014, 02:10 PM
No they are not the same slope. So changing the filter types should alter the angle. I did have them both at bw18 centered on 100 hz. Also tried the tops a little higher up to 116.

I was trying to figure this out on my own but neighbor didn't like there houses shaking.

Timo Beckman
September 17th, 2014, 04:29 AM
Could you post a screenshot? with solo traces of the sub and top?

September 29th, 2014, 02:56 PM
I'm going to try again later this week. I will post shots if I don't get it. Found a vacant field in the country with power. I will have the whole day to try things. Thanks for the suggestions guys.

October 6th, 2014, 10:57 PM
Well I did get some time to try again. I didn't recapture some of my traces as I was making changes on the fly. This is the best I can give you. Which I know limits the responses. Subs were set at bw18 90hz. I'm guessing that the crossover point looks far higher do to natural bump in response at 100hz. That may be what is causing my problems. Tops were set at bw18 115. Subs were delayed at 7.5 ms (horn design). Blue trace is finished post eq changes. I also lowered the gain on sub amps. That is the reason for the difference between individual and combo. Any critiques and advice is very welcome. Hopefully the screen shot works. Thanks


Timo Beckman
October 19th, 2014, 01:11 PM
So if i take a look at the screen shot (it's a bit unclear due to the black back ground) you might try to delay the tops with about 2.5 to 3 ms with the subs at the time you mentioned at 7.5 ms. It's a bit of a guess on my part.

There's another thing you might try and that's polarity reversal on the high's if the tops are actively driven (?). If they are passive do not mess with it :-)