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» Film-Tech Forum   » Operations   » Large Format Forum   » IMAX SR speaker crossover point (Page 1)

 
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Author Topic: IMAX SR speaker crossover point
Paul Trimboli
Master Film Handler

Posts: 274
From: Perth Western Australia
Registered: Dec 2002


 - posted 03-17-2005 04:40 AM      Profile for Paul Trimboli   Email Paul Trimboli   Send New Private Message       Edit/Delete Post 
I need to find out at what point a 2 way Sonics speaker as used in an IMAX SR setup is crossed over. Is there anyone that makes high power (600watt ish) PASSIVE crossovers?

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Gordon McLeod
Film God

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From: Toronto Ontario Canada
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 - posted 03-17-2005 09:35 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
Why would you want to passively crossover it since they will introduce far more distortion
Also the crossover slope of a passive is probably to shallow to protect the drivers

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Dan Suomi
Film Handler

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From: Aurora/Oswego, IL
Registered: Jul 2004


 - posted 03-17-2005 11:08 AM      Profile for Dan Suomi   Author's Homepage   Email Dan Suomi   Send New Private Message       Edit/Delete Post 
I would also like to add that that type of info would probably considered confidential to prevent anyone from copying speaker design.

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Paul Trimboli
Master Film Handler

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From: Perth Western Australia
Registered: Dec 2002


 - posted 03-19-2005 03:35 AM      Profile for Paul Trimboli   Email Paul Trimboli   Send New Private Message       Edit/Delete Post 
Well what might be happening is I will be doing the setup at a now closed IMAX cinema. The speakers are still in place, but no amps or crossovers. OK so passive does not seem the way to go. My question is still at what point should I cross the speakers over at and what should my crossover slop be? Is there anyway to work this out with out the driver specs?

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Mark Gulbrandsen
Film God

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From: Bountiful, Utah
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 - posted 03-19-2005 07:39 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
Paul, I have to chuckle, another closed Imax....... I guess you have "bean counters" down there too!

Anyway if you have a good spectrum analyzer, preferably one with at least 4 mics, and access to a programmable x-over with adjustable time delay this is a workable thing to do. While I can't reccomend any exact x-over points and time delay settings if one looks at what each driver is doing by itself its pretty easy to determine reaosnable x-over points and delay settings. The use of a TEFF analyzer probably would be needed to determine exact delay settings. Once you determine as close as you can what each driver is up to then building a system around them is fairly easy. I would definately reccomnend the use of a digital x-over for this. You will need LOTS of power... Dont skimp here! Hope this gives you some clues.

BTW: Those Imax SR sound systems just use Crown power amps in disguise....... inside the Sonics case you will find a Crown... not very original!

Mark

[ 03-19-2005, 11:45 PM: Message edited by: Mark Gulbrandsen ]

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Adam Martin
I'm not even gonna point out the irony.

Posts: 3629
From: Dallas, TX
Registered: Nov 2000


 - posted 03-19-2005 08:11 PM      Profile for Adam Martin   Author's Homepage   Email Adam Martin       Edit/Delete Post 
Only the SR (and maybe the MPX) systems use Crown amps. The higher-end systems use much better amps and run three-way.

Paul doesn't have the amps, he just has the speakers.

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Paul Trimboli
Master Film Handler

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From: Perth Western Australia
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 - posted 03-19-2005 08:43 PM      Profile for Paul Trimboli   Email Paul Trimboli   Send New Private Message       Edit/Delete Post 
Thanks for the help Mark. I can get my hand on such equipment so hopefully will be able to work it out. Was hopeing someone could say-oh sonics crossover at such and such and the slope is this number. But as Dan said, this might be confidential info. I was looking at around 600watt for HF and 600watt LF drivers. A couple of thousand for subs. Those numbers seem OK?

Your right Mark, we have been counters in Australia too. We only have IMAX Sydney and Melbourne left in Australia. When I was over in Sydney for work a couple of weeks ago I visted IMAX, building is a little run down but I think they are running at a point where they are turning over a profit.

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Gordon McLeod
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From: Toronto Ontario Canada
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 - posted 03-19-2005 09:24 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
I doubt you would need much more than 200 watts for the HF

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Paul Trimboli
Master Film Handler

Posts: 274
From: Perth Western Australia
Registered: Dec 2002


 - posted 03-19-2005 09:34 PM      Profile for Paul Trimboli   Email Paul Trimboli   Send New Private Message       Edit/Delete Post 
Anyone has much experience with Biema amps? Any good?

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Gordon McLeod
Film God

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From: Toronto Ontario Canada
Registered: Jun 99


 - posted 03-19-2005 09:47 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
I know David Johnson at Hoyts has been using them so maybe you should ask him

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Mark Gulbrandsen
Film God

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From: Bountiful, Utah
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 - posted 03-19-2005 11:43 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
quote: Adam Martin
Only the SR (and maybe the MPX) systems use Crown amps. The higher-end systems use much better amps and run three-way.

Yes, am aware.... Thanks, I stand corrected and so does the post. You mean theres someting better than Crown amps????? [Big Grin] .

quote: Paul Trimboli
When I was over in Sydney for work a couple of weeks ago I visted IMAX, building is a little run down but I think they are running at a point where they are turning over a profit.

Seems like an example of having to let the building go to heck because the profits have to go elsewhere.....by contract.

Good luck getting the system back up... shouldn't be too hard! Just don't blow any of those mysterious drivers or you may have to install something that can be easily delt with [thumbsup] .

Mark

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Paul Trimboli
Master Film Handler

Posts: 274
From: Perth Western Australia
Registered: Dec 2002


 - posted 03-20-2005 12:07 AM      Profile for Paul Trimboli   Email Paul Trimboli   Send New Private Message       Edit/Delete Post 
That was another question I had Mark,what if I need driver replacments? Got the spare parts speaker at the top of the screen I guess! [Big Grin]

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Gordon McLeod
Film God

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From: Toronto Ontario Canada
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 - posted 03-20-2005 09:50 AM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
Another issue to be addressed is bass summing to a sub since the screen channel speakers were designed for that form of bass management

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Mark Gulbrandsen
Film God

Posts: 15869
From: Bountiful, Utah
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 - posted 03-20-2005 01:39 PM      Profile for Mark Gulbrandsen   Email Mark Gulbrandsen   Send New Private Message       Edit/Delete Post 
quote: Gordon McLeod
Another issue to be addressed is bass summing to a sub since the screen channel speakers were designed for that form of bass management

Actually Gord if they install a DTS XD-10 which is most likely to end up in a replacement for that system they an go eiither with a dedicated sub or with bass summing. DTS will format it which ever way you want it onto your playback disk or per the director/producer. I recomend a Panastereo CSP-1200(even in its basic form!) as all the sub card slot is able to run full range if needed. Most LF DTS stuff is 6 track discrete with channel 6 as the sub channel. In leiu of that sub channel it can be used asa full range channel for high center in which bass summing is then necessary. For that slot you will need to add 1/3 octave eq which is bybassable in sub mode. BTW: The CSP-1200 also sounds WONDERFUL in a large format system!

Mark

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Gordon McLeod
Film God

Posts: 9390
From: Toronto Ontario Canada
Registered: Jun 99


 - posted 03-20-2005 02:03 PM      Profile for Gordon McLeod   Email Gordon McLeod   Send New Private Message       Edit/Delete Post 
From what I gather he doesn't plan to run large format and even if he did and put in a xd10 the speaker system design in the first place is designed for the use of bass management and the screen speakers are not full range down to the very bottom of the system
Even the larger 4 sonic systems still use bass management in there design also the "classic systems" used either re branded AB international amps or Bryston amps

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