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[Adam Schaible]

Hi guys,

I posted in the SMAART forum and didn't get much help.

My goal is to phase align my tops and subs, but before that I need to time align them.  I'm fairly green with SMAART - I've read the quick start guide and know my way around the software, but I'm not able to configure my measurements correctly, and/or I'm having trouble configuring my hardware.

I am aligning KF650z's to SRX 728's.  I'm going to make a preset stacked, but I'd like to be able to repeat this process on site for my larger gigs when I change my sub placement.

My signal chain is as follows (ignoring SMAART):

iPod L&R into A&H iLive, L&R outs into a UX8800 (80hz crossover), right now I'm doing mono - UX8800 is taking both A&B for the outputs, into an I-Tech 5000HD, then out to the speaker.  The iLive is setup as L-R-Sub and the sub output is going straight into another i-tech HD and I'm using the built in processing to cross the subs.

I have an M-Audio profire 2626 interface, with a DBX reference mic.  I'm sending both channels of the iPod input into aux 1 and sending aux 1 out into the reference channel of the interface.  Smaart see's both of them.

I'm not sure, but I don't believe there is any more or less delay in the aux bus than there is in the master, so I think this should work - however should as I understand reference should PROBABLY come out of the L out, and I should just use the L channel for this?

Advice would be greatly appreciated!

[Rob Spence]

Well, for one thing, you need to only do one side (ie; one stack) at a time. So, if you are sending mono to the LR outs, you can disconnect the side you are NOT doing and use that for the reference.

Actually, once you have done one side, you are really done if the 2 stacks are the same.

[Mac Kerr]

Adam Schaible wrote on Tue, 27 April 2010 13:28

My signal chain is as follows (ignoring SMAART): iPod L&R into A&H iLive, L&R outs into a UX8800 (80hz crossover), right now I'm doing mono - UX8800 is taking both A&B for the outputs, into an I-Tech 5000HD, then out to the speaker.  The iLive is setup as L-R-Sub and the sub output is going straight into another i-tech HD and I'm using the built in processing to cross the subs. I have an M-Audio profire 2626 interface, with a DBX reference mic.  I'm sending both channels of the iPod input into aux 1 and sending aux 1 out into the reference channel of the interface.  Smaart see's both of them.

Use the iPod only for listening to music to pass judgement on the changes you make. Use pink noise from the console for measuring. If Aux 1 is your reference send, send pink noise to that, and to the subs. When you have a stable phase trace take a snapshot by hitting the space bar. Now send noise to the 650s and ref, but not the subs. Look at the phase trace at the crossover frequency between the 650s and the subs. You want the phase trace from the mains and the subs to lay on top of one another at the crossover frequency. Without changing anything else, still with a live view of the mains, add delay to the mains. As you add delay the phase trace should move toward the saved trace from the subs. If it moves away, start over with the mains as the saved trace and delay the subs.

Mac

[Adam Schaible]

Ok thanks Mac,

I was using the iPod as the pink source but that makes sense to just use the console.  I'm using SMAART 7 - is there a particular combination of settings I should be using to collect this data?  It seems to wrap a LOT - like 7+ times, and although the slope is constant, it seems like my measurement configuration is suspect.

[Mac Kerr]

Adam Schaible wrote on Tue, 27 April 2010 15:07

Ok thanks Mac, I was using the iPod as the pink source but that makes sense to just use the console.  I'm using SMAART 7 - is there a particular combination of settings I should be using to collect this data?  It seems to wrap a LOT - like 7+ times, and although the slope is constant, it seems like my measurement configuration is suspect.

Since you are only interested in the area around the crossover frequency between the sub and the mains, zoom in so you only see the range from say, 50Hz to 250Hz. This will get rid of a lot of the distracting wraps.

Mac

[Adam Schaible]

My assumption was that the phase trace on my subs should be flat after the HPF and before the LPF - is that assumption incorrect?

[Art Welter]

Adam Schaible wrote on Tue, 27 April 2010 13:07

Ok thanks Mac, I was using the iPod as the pink source but that makes sense to just use the console.  I'm using SMAART 7 - is there a particular combination of settings I should be using to collect this data?  It seems to wrap a LOT - like 7+ times, and although the slope is constant, it seems like my measurement configuration is suspect.

You must use Auto sm to measure the delay, then insert the delay time, otherwise the phase trace will not be correct, which can easily cause multiple wraps in the HF.

A large phase discontinuity around the crossover point may indicate a polarity reversal. Polarity should be checked prior to adding delay to the LF or MF.

[Adam Schaible]

Is this equivelent to the "delay finder" in smaart 7?

When running pink noise through the subs, the results of the find delay feature vary extremely (like 300ms).  When I do it with the tops it is pretty accurate, but comes up with over 16ms which seems way higher than I expect.  I anticipate 1-2 for the desk, and maybe up to 5ms for the ux8800.

[Adam Schaible]

I just checked this PDF:

http://www.rationalacoustics.com/files/v7GS_Ch4_Transfer_Fun ction.pdf and read the v6 manual.. That's what i was doing, but perhaps the issue was that the pink noise was coming from my iPod and not the console.  I don't really think that's the problem but it's something I will try?

[Mac Kerr]

Adam Schaible wrote on Tue, 27 April 2010 15:27

My assumption was that the phase trace on my subs should be flat after the HPF and before the LPF - is that assumption incorrect?

Yes, that is incorrect.

Mac