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  »  New  About the tweeters phase alignment...  Avatar Acoustics time adjustable tweeters....  Horn-Loaded Speakers Forum     3  40631  09-29-2006
  »  New  Time Alignment : Live Performances vs Audio..  Stating the obvious...  Playback Listening  Forum     9  51593  03-07-2007
  »  New  Stop having a fear of horn vignetteing..  Eclipsing the feathery edge...  Horn-Loaded Speakers Forum     1  15495  12-14-2007
05-26-2007 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 1
Post ID: 4463
Reply to: 4463
Driver Alignment, and Where to Draw the Line
Some thinking about Romy's Injection Channel (see the following thread) :

GoodSoundClub - Romy the Cat's Audio Site - The "Macondo Ultimate" MK-XXVII, Revision 432

... brings me to a question that I've had a for quite some time:

When aligning a "normal driver" with a compression-type driver, what point on the "normal driver" should be referenced as that to be aligned with the membrane of the compression driver?

On the "normal driver" viewed from the side :

• Is it the center of the coil at rest in its gap?
• Is it the mounting flange of the basket?
• Or is it somewhere in between?

In the case of a 15" Bass driver, the difference is substantial.

I suppose it is also possible that of the above three possibilities, there is no correct answer, and that such measurements will only get you in the ball park (Macro-Driver-Alignment?)... The final step requiring painstaking trial and error.

Up to now, I have sort of assumed a correct point to be about half way between the coil and the suspension of the "normal driver" (viewed from the side)... And that perhaps it would make sense to reference a point a bit closer to the mounting flange in acknowledgement of the membranes greater area toward the front (due to the conical form).

Anyone have thoughts on what might be correct?

Thanks in advance,

jd*



How to short-circuit evolution: Enshrine mediocrity.
05-27-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,302
Joined on 05-28-2004

Post #: 2
Post ID: 4466
Reply to: 4463
I have writhen about it before somewhere.....
It is very easy to figure out acoustically. Feed the drivers and their crossover with a reference tone of fixed amplitude and fixed frequency, roughly in the middle of crossover point. Disconnect one of the drivers and measure the acoustic pressure exactly at your listening spot with your RTA or scope. Now connect another driver and see what happen with amplitude, you need approximately +3dB, if your tone is in middle, or as much as you can get. With both driver on, take one of the drivers and begin to slide it further and closer from your listening position until you found the maximum gain from both drivers. You will start with sliding it within inches and eventually, the closer you go to the point of aliment, you will slide it within a few millimeters. Since you are at relatively low frequency (the bottom of your compression driver) then there is not danger that you hit the summit of the next cycle. The point of the maximum gain, where the peaks of the cycles wills expand each other will be your time alignment spot. Mark the fixation of the both driver. BTW, be advised that turning the drivers on their axes also very aggressively affects aliment. I am against of any angling of the axes with horn installations horns with exception of the LF channels, where it becomes irrelevant. I know, I know, many people do it. GOTO does it, Cessaro does it. Many other manufactures and private parties do it. I disagree with them and I feel that in horn system the axes MUST be absolutely parallel.


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-27-2007 Post does not mapped to Knowledge Tree
stuck.wilson
Hyattsville, MD, US
Posts 21
Joined on 09-04-2006

Post #: 3
Post ID: 4468
Reply to: 4463
time alignment

hey jessie-

I've wondered the same thing-- and the more i end up twiddling around with it, the more I think it really either comes down to good measurements, or  good listening!  And in fact.. probably both in conjunction!

I have a small 2 way system (crossover's around 1400hz)-- and to ballpark it for starters, I looked on line for a wavelength calculator-- defining the offset of acoustic centers.    Since I'm using an asymmetrical XO (bass box a 2nd order, horn a first)-- using what bad information I have available-- I extrapolated that there is a phase difference between the two of 135 degrees-- the first order being 45 degrees 'ahead', and the 2nd order being 90 degrees 'behind'. 

SO-- that being the case-- I took the distance of a wavelength at 1400hz, multiplied that by 135/360, and got the offset from direct acoustic center of the driver.. 

After that-- I based the measurement to the approximate 'end of piston'-  by eyeball.. I can't measure through the woofer, obviously.. but I've got vented dustcaps, which helps.  Add that to the offset.. and then it's all by ear.  but to get a good reference point-- i took a straightedge across my bass driver, and extrapolated the distance inset from the CABINET ( the straightedge lines up with the top lip of the cabinet, as it's front mounted) to the piston by eye.  I'm a carpenter.. so I guess that crap a lot--  but you'd still be ballparking-- so a good guess is better than nothing.  For the compression driver-- there's a silver band in the center of mine, which i believe holds the gap-- so i use the back of it as my 'guesstimation point'.

What I usually do after that is to keep a machinists rule nearby, and listen to things with a lot of ambient information, as well as things with big transients in the XO range... especially bombastic piano jazz..  which exposes bad phase problems like spotlighting deer in an empty field...  big 'frrmmPPHHTTtt..'' every time theres a BIG transient.. you'd have a hard time missing it!  the ambient information is more subtle.. but when you get it right... ('right'.. I'm no expert, I assure you...)-   decay is MUCH better.  Oh yeah.. the machinists rule is to keep track of the movement of the horn forward and back-  best to keep track.. because sonic memory is usually pretty bad..

BUT.. I think you already said as much.. it's all trial and error, unless you've got a great RTA and mic setup, or bionic ears.. and even still....  Just keep track of your experiments and go with what you hear!  I can't speak to the 'absolute correctness' of ANY of this data.. it's just my experimenting logic, if y' will.. but it's yielded decent results so far, best I can tell!

Good luck!

yrs

dan
05-27-2007 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 4
Post ID: 4474
Reply to: 4468
Measured Progress
Thanks very much Romy and Dan for the input.

With the exception of a structure to locate the horns, I have all the tools necessary to make the measurements.

Though this is all happening in France where DSPs and TADS rule* (see note at end), all filters are first order passive, non-digital.

BTW, I am using a 180Hz lower Mid-Range horn with the S2 driver filtered to receive between 800-3200Hz (first order). Working within this frequency band, I hear no reason to use a steeper filter. It is really clear why Romy calls this the fundamentals channel.

I don't yet have frames to hold the horns in place, but I've been working on a design.

This frame would allow some fore and aft adjustment of each horn. With a bit of careful planning, the driver will end up in the center of the range of adjustment (this is what was behind my question in the above post).

Romy's comments on "axial rotation" of the horns (meaning in this case, angling the horns) has me thinking. I had planned to build in a vertical tilt adjustment for horns located near the floor and ceiling...

I would be interested in hearing more if anyone has thoughts on this subject.

In any case, in this house the 45Hz Mid-Bass horns will have to be angled down from above ; their drivers will not be aligned with the rest of the system... this may eventually be a reason to move to a new house.

Thanks again,

jd*

Oh yeah : Why have the French so embraced DSP technology? Simple ; if you had a French mother, you too would likely embrace DSP technology (I am completely serious here).

I am leaving out a lot, but the rusult is as follows :

These people are superbly able to grasp complex concepts in isolated blocks... And superbly unable to put into practice the concept of flux.

They see and act only in blocks!


How to short-circuit evolution: Enshrine mediocrity.
05-27-2007 Post mapped to one branch of Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,302
Joined on 05-28-2004

Post #: 5
Post ID: 4475
Reply to: 4474
Vertical tilt adjustment for horns

 jessie.dazzle wrote:
Romy's comments on "axial rotation" of the horns (meaning in this case, angling the horns) has me thinking. I had planned to build in a vertical tilt adjustment for horns located near the floor and ceiling...  I would be interested in hearing more if anyone has thoughts on this subject.

Do not listen Romy, make you own very simple experiment and then make your own mind. Take two horn channels, low-pass and high-pas them at 6K for instance and drive them with 6K sinewave. When you time alight the driver you have well measurable gain. Any minute angling of axes of any of two drivers you will have change of the summarizing gain. Then set the driver with one having 1-2cm delay and begin to angel them. You will see that aliment will be changing and you will be able to changing the delay and angel to find the look-like perfect time alignment. However, here what the GOTO, Cessaro and the rest of the guys failed to admit: the angled aliment will work probably ONLY for a VERY specific listening distance. The parallel horns however do not care about listening distance. BTW, the effect is audible at HF and for bass horn that do not go very high the “parallel axis paranoia” might be neglected.

BTW, a few years ago the Moron Steve Rochlin wrote a review in Ultimate Audio, suggesting tilting the AG horns. I had replyed to it and it was surprisingly not vandalized within the AA's drain…

http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=6349

 jessie.dazzle wrote:
In any case, in this house the 45Hz Mid-Bass horns will have to be angled down from above ; their drivers will not be aligned with the rest of the system... this may eventually be a reason to move to a new house.

if the 45Hz Mid-Bass horn do not go over 300Hz then, I think, could be annealed quite dramatically.

 jessie.dazzle wrote:
Why have the French so embraced DSP technology? Simple ; if you had a French mother, you too would likely embrace DSP technology.

I do not think that you are right. French audio people like anyone else walk in packs and eat whatever is given to them. In the end of the 90s French folks become to be stressed by DSP filtration propaganda when your French Jean-Michel Le Cleac'h fell in love with DSP and begun to staff this idea into the minds of the French “horny” public. Jean-Michel is experienced guy but he became the Behringer or BSS distributor (or dealer) and then whatever he begun to talk about the DSP subject stopped to be appealing. I think THAT made many French to look at DSP. Ironically I see no problems when people try to resolve the delay problems with DSP but they also do filters by DSP and THAT it horrible…. BTW, I have a local guy who had horrible sounds for years running his 3 channels with DSP filters and multi-amping.  Recently he got Pioneer D-23 crossover, a cheap and VERY consumer-level but very flexible and friendly – a perfect piece for prototypes. His sound still is not good but MUCH better then used to be. When he first time turned his system and I did not know that he use a new crossover, I immediately asked him what happen with his playback that it is suddenly become to sound friendlier.

Rgs,
Romy the Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
05-04-2010 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,302
Joined on 05-28-2004

Post #: 6
Post ID: 13419
Reply to: 4463
The deaf skeptics, take note.
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I have been pitching about the superior importance of time alignment for years. It is not that I violently insist that people have their channels time-alignment. We kind of free people and everyone do whatever they want. Still, I exercise for years my liberty and do not take serious audio comment and audio opinions from the people who have channels misalignment and who do not see it as problem. I understand that most audio people can’t understand the heard and they instead of recognizing and interpreting difference use “somebody else opinions”. There are some opinions out there that time-alignment is kind of important. If a car mechanic claims the in your small 6 cylinder engine the ignition alignment is important then no one argue with him. However, when we bring to the same mechanic a large 12 cylinder bus of cargo track then we do not feel that larger engine do not need comply with ignition-alignment. Why in such case the Morons feel that if they go for large horns then the rules of time-alignment are not applicable anymore? Because it is difficult to do or because some audio-idiots so hate Romy that Cat that they scare to admit to themselves that Macondo configuration is the ONLY one available sane configuration to build multichannel horns? Well, I let the audio- idiots to treat their psychological problems with whoever is interested in them and will bring the recent case for illustration.

I do not have time misaligned system for a while and I even forgot how it might be. Moving to the new room I tossed the channels as they were, aligning the drivers very rudimentary, by eyes. The last might I took my RTA and aligned the drivers properly. The Macondo right the way went from the former anarchy sound to the sound that I am cultivate. It is very hard to explain what difference the perfect alignment made. I mean, it is not hard because it is difficult but hard because there are TOO MANY CHARACTERISTICS OF SOUND that “magically” improved with time alignment and make the sound to be as it shall be.  Those characteristics of sound did not even get improved – they just do not exist in time-misaligned configuration.

Anyhow, I will not continue it as but I would extend to the Morons who listen the time-misaligned horns one more opportunity to pay attention to the subject of driver’s time-alignment. If your channels, particularly above 200Hz, are time-misaligned then your playback sounds like shit. That is juts very simple as is. The sad part is that you would never knew how much more complexity and more interest in Sound you would realize if you had your drivers time-aligned.

Romy The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
Page 1 of 1 (6 items) Select Pages: 
   Target    Threads for related reading   Most recent post in related threads   Forum  Replies   Views   Started 
  »  New  About the tweeters phase alignment...  Avatar Acoustics time adjustable tweeters....  Horn-Loaded Speakers Forum     3  40631  09-29-2006
  »  New  Time Alignment : Live Performances vs Audio..  Stating the obvious...  Playback Listening  Forum     9  51593  03-07-2007
  »  New  Stop having a fear of horn vignetteing..  Eclipsing the feathery edge...  Horn-Loaded Speakers Forum     1  15495  12-14-2007
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