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Author Topic: USL XTA-1 Crossover Richard B. Perrine Film Handler Posts: 89 From: Cuyahoga Falls, Ohio Registered: Apr 2000 posted 03-20-2010 10:05 AM                     Since you've got this topic going......We have a CP-500 that is fed into the USL 3 channel bi-amp frame (forget the model #)....with 125HZ cross-over modules. Problem is when we play an academy mono print....all sound goes to the horn. I wanted to change to the the 500HZ XTA-1 modules to correct this. Would the module built for the QSC 1400 work in the 3 channel frame.....or are they wired differently ? RBPerrine@att.net  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 03-20-2010 01:44 PM                     Yes Richard, the modules are exactly the same and will work just fine in that frame. But..changing from 125hz crossovers (and what oddball speaker requires bi-amp at 125hz?) to 500 hz crossovers means you WILL have to do a B-Chain Eq and level reset as it will radically alter the system's output. You may find some serious issues with response as well, as it seems that the horn is supposed to take all of the "mid-lows" away from the LF driver, which may not have enough output above the 125hz crossover point...if that is even the correct crossover point for those speakers. It would be helpful if you could post the make and model of your speakers.. It would not be a "plug and play" type of thing. If all the sound is coming from only the horn in mono it sounds like there is some other problem happening, as IIRC even Academy mono has some content below 125 hz...  |  IP: Logged Clint Koch Phenomenal Film Handler Posts: 1435 From: San Luis Obispo, CA, USA Registered: Feb 2002 posted 03-21-2010 12:02 AM                     USL has two standard frequencies, 500Hz and 800Hz. We will modify them for any frequency the customer ssks for. Like Tony said, 125Hz? Odd number. Do you know who modified them? USL? When were they modified?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 03-21-2010 12:18 PM                     What stage speakers are you sure it isn't 1.25KHz  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 03-21-2010 02:33 PM                     Good pint Gordon..and if the current xover is 1.25k and you change it to 500hz you run the risk of blowing out the HF drivers. Hi Clint!! Those encoders I mentioned a while ago are still going strong...  |  IP: Logged Richard B. Perrine Film Handler Posts: 89 From: Cuyahoga Falls, Ohio Registered: Apr 2000 posted 03-22-2010 01:20 AM                     Ok Been away for a few days here.... I don't remember the name of the speakers....if this helps.. the system was installed in 2000....The Speaker line was sold to Big sky a few years later....we got no documentation on it at all. I started to look into this problem when we ran a mono print of Woodstock and it sounded like a ballpark stadium. The amp rack is duel bi-amped... CP-500 to the ULS bi-amp EQ frame.....then LCR have 2ea QSC Mx 1500A amps in stereo mode...one complete amp for the highs....one for the lows. Behind the screen are low, mid and high cabinets with another cross-over unit. So...for the left channel there are 4 pairs of #12 running to the speaker from the amps. The speaker "name" was something like SRT model 3500...it's buried in my file at the theater and actually when you look at the units behind the screen they are componets from severl different Mfg's. Here's the simple thing.....when running a mono print...the signal present light never flashes on the bass amps. That's out of this ULS Cross-over. The modules do have a 125 hz sticker on them and are XTA-1. If it was a 1.25Khz....there would probably be some drive on the bass amp. Doly digital and SR sound fine. I've also taken a couple of reels of mono prints that I have and run them in mono, SR, and bypass with no perceptable change. I beleive it's the 100hz rolloff and the 125HZ cross-over frequency on the modules that's giving me the problem. To answer a couple of questions you asked me.....the systems was installed new in 2000 and spec'd by then NCS cincinnati by Mitch with him and John Harvey installing it. We did discuss this with Mitch after running several mono prints and he did think that changing the X-over would blow the speakers. I did call Big Sky once and talk to them..They said the X-over frequency was almost a matter of personal taste. I do have 2 XTA-1 modules 500Hz marked QSC 1400 only....so I'm wondering if they will work for a test. i'd like to hear more on the possiblity of blowing the speakers before I try just running a test. RBPerrine@att.net  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 03-22-2010 05:05 AM                        Change crossover to a more suitable frequency and replace stage speakers with "normal" speakers (like JBL), retune and get normal results. Louis  |  IP: Logged Kenneth Wuepper Phenomenal Film Handler Posts: 1026 From: Saginaw, MI, USA Registered: Feb 2002 posted 03-22-2010 07:34 AM                     TOM, Let's take a more scientific approach to this problem. Did the system EVER sound right? If it did, then what has changed? Without proper equipment and knowledge of the basic engineering involved, you would be well advised to seek competent help with this problem. This sounds like a classic case of out phased speaker systems. The more discrete the signals to the speakers are, the less the effect of the out-phasing will appear. Thus the DD and SR formats will show the least effect from the problem. To begin you must have a known good and stable signal source, like the Dolby Pink Noise source. Then you will need a Real Time Analizer to see the results. Since there are many places in this system for phasing errors to occur, one should start with the alignment of the drivers in each of the speaker arrays. There is a good description of how to do this in the Altec notes on the old Altec site. Then you can proceed to the phasing between the units with the amplifiers and speaker cabling. You mention tri-amplified and then say there are 4 pairs of wires to each stage speaker stack. Please elaborate on where these wires are connected. Tri-amplification requires 3 pair, one for each bandpass speaker. Also you state there are crossovers in the speaker arrays as well. Where in the system are these placed? Are these merely high or low pass filters to protect the drivers of that particular range? Well, without seeing the equipment or hearing the results of these tests, I will await your response. Sincerely KEN  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 03-22-2010 09:36 AM                     it sound that in fact you have a 3way system on your screen channels and 125hz would be probable for the bottom end speaker If memory serves bigsky used the ribbon drivers for the high end  |  IP: Logged Ron Lacheur Jedi Master Film Handler Posts: 650 From: British Columbia, Canada Registered: Feb 2002 posted 03-24-2010 03:42 PM                     Just a thought, What is your mono trim and EQ set at on the CP500?  |  IP: Logged Robert Throop Master Film Handler Posts: 412 From: Vernon, NY USA Registered: Jun 99 posted 03-27-2010 07:27 AM                     quote: Tony Bandiera Jr Good pint Gordon Gordon loves a good pint! javascript:void(0)  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-27-2010 08:02 AM                     Dang RObert... you beat me to it! Louis is 100% correct! You may as well have the "Horizon" brand name on those speakers!  |  IP: Logged

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