Time-alignment

[boputnam]

OK, all you dbx Driverack'ers out there - a question: What are you applying for delay to your mains to time-align with the subs?

I was working into new rackgear this afternoon - the KT DN9848 http://www.klarkteknik.com/dn9848.htm - which took months to get, touring season and all... So I was time-aligning my smaller mains and reflecting on some dialogue on ProSoundWeb where many report routinely applying a 6-8ms delay on the mains to align with the subs (before they delay the system for backline or room position, etc).

Tonight I confirmed it once again - a full 2.66ms (3ft) delay was needed to time-align the mains with the subs. There is no other processing in the signal path - this is needed delay that is imparted by the crossover(s).

Here's my set-up:

EV QRx 118s sub and QRx 115/75 (running bi-amped, with the 2-way Mains in passive mode) positioned in factory placing atop the sub, Earthworks SM30 positioned at 7-ft, on-axis. Using SmaartLIVE's Impulse function, the subs were (repeatedly/continuously) sampled independently from the Mains, and the arrival difference noted.

The subs were acoustically materially behind the Mains. No news there, but I realized I do not employ this technology in the home on the 4345's - there I use an analogue crossover and no DSP.

So, I wonder, what do you Driverack'ers do, at home - do you know?

• Infredible - what delay are you using between the LF and MF/HF on those 4343's?
• Widget - do you know if the DEQX is employing any time-alignment, and phase adjustment?

OK - some pictures...

1) The small stack (one side, only) - no, this is not Pancake House...
2) SmaartLIVE Transform function, full range, after applying the 6-band parametric to the DN9848 "Outputs"
3) Face of my combined "drive" and "FX" rack - from the top: TC M2000; DN9848 DSP; DN370 EQ; DN514+ 4-channel gate; DN500+ 2-channel C/L; Ashly CLX-52 2-channel C/L, etc.... NB: I was only using Channel 1 (Left) for this - note that both Channels of the DN370 EQ are bypassed (Red LED to right of Channel faders); and only Outputs 1 (L-Sub) and 3 (L-Main) are active (lit) on the DN9848. None of the Inserts are active...
4) SmaartLIVE Impulse, Mains (here includes a global, system 10.07µs delay I was playing with, exploring the "Haas Effect" - but that is subject of a future Thread...)

[Mr. Widget]

"Widget - do you know if the DEQX is employing any time-alignment, and phase adjustment?"-Bo

It does if you want it to. It will correct for phase, time-alignment, and group delay too... all independently.

I am not currently using any of those features though I have in the past. I was debating the need for proper time-alignment a while back and forum member Al Klappenberge was saying that it wasn't important... I am now leaning closer to his position.

Bo- how can you use that impulse response plot... there is so much hash...

This one clearly shows that the tweeter is about 0.5ms ahead of the midrange... it also shows that the midrange is out of phase with respect to the tweeter and is 180° out of absolute phase.

Widget

[boputnam]

Bo- how can you use that impulse response plot... there is so much hash...

Only the top window reflects the impulse trace, dood...

btw - are you and Ms. Gadget game for the Box Set and Grapefruit Ed show at the Sweetwater, Friday...?

[boputnam]

This one clearly shows that the tweeter is about 0.5ms ahead of the midrange... it also shows that the midrange is out of phase with respect to the tweeter and is 180° out of absolute phase.

And, what of the LF and now the SUB1500's...?

And, why did you decide to lean closer to Klappenberge's view - can you direct me to that Thread dialogue...?

[Oldmics]

Include a fax # and I will send you an article on

"Electronic Delay Arc Processing" for Subwoofers

from "L" Acoustics.

Once you read this work ,you"ll have to send out for "fresh brains".

Oldmics

[Ian Mackenzie]

Bo,

In theory crossing over below 150-80 hz to subs introduces significant group delay as a result of the crossover filter & frequency (see Drews clues). In this instance it is prefered to position the subs forward of the mains if they cannot be digitally delayed.

In the home scenareo with the 4345 the postions of the mid / woofer are relatively small compared to the wavelength at the crossover point and this is not a critical issue.

One would imagine any additional digital processing would only lead to degradation of the signal .

Ian

Ian

[Mr. Widget]

Only the top window reflects the impulse trace, dood...

btw - are you and Ms. Gadget game for the Box Set and Grapefruit Ed show at the Sweetwater, Friday...?

The Mrs. is still out of town....

And, what of the LF and now the SUB1500's...?

Still working on it...

And, why did you decide to lean closer to Klappenberge's view - can you direct me to that Thread dialogue...?

http://audioheritage.org/vbulletin/s...ead.php?t=5079


Widget

[Lancer]

I was debating the need for proper time-alignment a while back and forum member xxxxxx was saying that it wasn't important... I am now leaning closer to his position.

Ok!
I wanna play!
You lean that way and I'll lean the opposite way to counterbalance you so you won't fall off.

[Mr. Widget]

Ok!
I wanna play!
You lean that way and I'll lean the opposite way to counterbalance you so you won't fall off.

The thing is... with Deqx and Clio, I can adjust and correct for proper time-alignment and while the measurements are readily apparent as to which is better, the sonic impact isn't as clear cut. I will be conducting more experiments over the coming months to see if I can come to rest on this balance beam instead of just leaning one way or the other... in the mean time I appreciate your helping to keep us balanced.

I wonder if Dr. Toole and friends have come to any definitive conclusions?

Widget

[johnaec]

I will say that I once did a listening experiment on a 2-way system that included a phase control on the electronic crossover for the highs, and other than anomolies at crossover frequencies, I was surprised to discover I could not hear any detrimental or even audible effects when LF and HF were obviously very out of phase...

I do agree linear phase is a worthy goal - even if I can't hear the difference, the idea of knowing the drivers are in phase is at least somewhat comforting.

John

[Steve Schell]

Hi guys,

In the three way front loaded horn system my partner Rich and I have been developing, we have some pretty severe arrival time issues. The subwoofer has an 18' path; the midbass horns have a 7' path, and the mid/high frequency horns have a 30" path. Recently we have been running passive crossovers between the upper two horns, and electronic crossover and separate amp for the sub. Horns tend to sound so fast and clean that one can actually get away with such misalignment and have the results sound pretty good. About all I can hear specifically is a slight subwoofer lag on highly percussive recordings.

At times we have run the system with the DEQX, and used it to correct for the arrival time errors. This is definitely better, as everything lines up and has more wallop and clarity, and a more focused soundstage. We will set up the DEQX again soon, when we receive the new version of the software.

Ian, I'm as wary of digititis as the next guy, but so far the DEQX has been sonically invisible as far as we can tell apart from its intended functions.

[boputnam]

...everything lines up and has more wallop and clarity, and a more focused soundstage.

Ian, I'm as wary of digititis as the next guy, but so far the DEQX has been sonically invisible as far as we can tell apart from its intended functions.

Hi, Steve...

I concur. Once I got out of Pink Noise... I restricted my listening to acoustic stuff with wide-open transients. I gotta say, there was an improvement - things were clearly in-synch. It was as if the acoustic guitar was right there. W/o the delay, it was all still very good, but not as clearly articulated (for lack of better word). W/ delay was better.

On the "digititis", I am outspoken critic of lesser quality A/D and D/A converters - and I find digital EQ's annoying. This particular DSP unit is a pleasant surprise. I A/B'd with an analogue crossover, and while the analogue has some slightly perceptible warmth (arguable), with it I relinquish the (additional) parametric EQ that I can store/recall, as assigned to various cabinet combinations I use. Starting with the speakers "flattened", makes it much easier and more efficient when getting into an unknown room/venue to optimally EQ the room (same-same on monitors - it greatly improves GBF without a great deal of venue-specific tweaking).

[Ian Mackenzie]

Thanks Steve,

Perhaps my desires for full horn loading without time alignment anxiety will come of age. This make a conical horn all the more interesting!

Ian

[Mr. Widget]

...we have some pretty severe arrival time issues. The subwoofer has an 18' path; the midbass horns have a 7' path, and the mid/high frequency horns have a 30" path.

Well now, that's a different story... I was talking about maybe a maximum delay of 2-3ms.... not 10+ ms!

Ian, I'm as wary of digititis as the next guy, but so far the DEQX has been sonically invisible as far as we can tell apart from its intended functions.

I'll second that. The analog section in the preamp version might be improved, but it is better than the analog section in most CD players and is reasonably invisible.

Widget

[Ian Mackenzie]

You have seen this before so lets re visit it.

Having had some hands on experience with the DEQX now you probably appreciate there is more to this subject than there appears.

Have a think about it and a play.

Cheers

Ian

The links are gone and files are too big to upload so I will zip then and send them to the Widget over the weekend if he has not already got them


A new Crossover Theory
Below is an extract of a post from diyaudio.com that may prove interesting for those involved in the crossover design, particularly if you have access to a sophisticated digital crossover network.

Improoved Sound Stage and 3D-Imaging Post #265 Dear folks out there,
I would like you to participate at one of the most interesting filter designs I ever tested on my Behringer.

Some time ago a French gui called Thierry Martin mailed me some information about a new kind of filter design for speaker crossovers engineered my Mr. Le Cleach. The material was ONLY in French so it was quite hard for me to follow his approach. Finally I found a French person which translates the article to German (uuh, what an ugly German!). After that I started translating the article to real German and also to English for you. The whole material you’ll find here (8am to 10pm german time):


Well, in-between I tested the approach of Le Cleach with my DCX-2496 and got so astonishing results that I thought I had to let you know about his theory. Believe me or not: With his filter design you get a soundstaging and imaging you never heard before on your system!!

So what has to be done?

First adjust your DCX-2496 the way you have a flat frequency response and time aligned speakers which can be achieved by the auto align function of the DCX 2496 (yes, you need a microphone this is VERY important!). I guess you did it before ;-)

Now read the paper (.doc-file) I submitted in the ZIP, open the spreadsheet and enter the values according to your current DCX-2496 configuration. Do not enter the current time delay of your DCX in the spreadsheet! Now in the spreadsheet modify the values as described in the paper. If you got a good result in the spreadsheet adjust your values in the DCX-2496 so they match the spreadsheet.
A bit care has to be taken at the delay. The auto align function of the DCX calculates values for the delay. To these values the values from the spreadsheet have to be added. This means the distance between the chassis will become bigger. Le Cleach says the speakers (bass, mid) have to be moved towards the listener. With the DCX-2496 you have to move the mid and tweeter away from the listener which is the same!! The distance gets bigger.

Now save this adjustment under a new preset of your DCX, sit down and listen while switching between your old preset and the new one. What you will hear is really astonishing. The whole characteristic of the sound will stay the same (same frequency response) but with the new settings the soundstage expands and you will get a never heard 3D-imaging.

A nice test for the new setup is the SACD “Scared Love” from Sting. In my opinion it is a bit over instrumented and it is sometimes difficult to differentiate between the voices and the instruments. With the new filter parameters the whole soundstage unfolds and ….. you know, I now really love this SACD.

And best of all: The filter modification is for free just try :-)))