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Author Topic: THX crossover SG-01 Magnus Eriksson Expert Film Handler Posts: 121 From: Stockholm, Hägersten, Sweden Registered: Jan 2011 posted 02-26-2018 01:38 PM                     How can I connect to this unit? This week me and my colleagues are replacing some sound equipment at a (soon former) THX auditorium. New sound processor, crossover and power amps. All 35mm gear to the scrap yard. The front speakers remain though, 3-way Electro Voice something from 1998 (I haven´t crawled in behind the baffle wall for a closer look yet). But I would like to have a look inside the SG-01, just to get a rough starting point for the new crossovers. But how? I see the RS-232 connector, but then? /M.E.  |  IP: Logged Dave Macaulay Film God Posts: 2321 From: Toronto, Canada Registered: Apr 2001 posted 02-26-2018 02:15 PM                     These were set up by the installer for the speaker used, I don't have a setup program. Probably look at the speaker specs for the recommended crossover frequencies?  |  IP: Logged Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 02-26-2018 05:13 PM                     It's THX, so this box is sealed and not user-configurable. You can try to flash the JBL firmware onto it, maybe it works if you're lucky, but the settings will be gone. I would lookup the make of the speakers and go from there to find their optimum crossovers. You want to see how stuff looks back there anyway I guess? Alternatively, if you have the equipment, you could also simply try to plot them.  |  IP: Logged Magnus Eriksson Expert Film Handler Posts: 121 From: Stockholm, Hägersten, Sweden Registered: Jan 2011 posted 02-27-2018 04:11 AM                     OK, tried to make a shortcut. They are never successful After a dusty visit far back stage we found: Electro-Voice TL606DMT + HPK-Variplex-B. The documentation says 330Hz for top/bottom crossover (HF/MF passive). But: we are not able to find anything regarding HF/MF crossover parameters. And this is an active 3-way system. Does anyone here know? Edit: HF/MF passive of course  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 02-27-2018 09:47 AM                       I would ask Ryan Mendoza at THX. I've lost track of them over the years but they and Ryan are still there I've been told.  |  IP: Logged Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 02-28-2018 01:11 AM                     So, in your case, the passive crossovers in the 3 (or 5?) MF/HF units where bypassed and you do have specific HF outputs connected on your SG-01?  |  IP: Logged Jay Wyatt Film Handler Posts: 33 From: Los Angeles, CA Registered: Mar 2015 posted 02-28-2018 01:24 AM                    If you have a copy of SMAART you could run a transfer function (TF mode) between the input and output of the THX box. The magnitude response would reveal the DSP thats going on under the hood. Capture a trace for each output (Lo,mid,hi) and overlay them on top each other.  |  IP: Logged Magnus Eriksson Expert Film Handler Posts: 121 From: Stockholm, Hägersten, Sweden Registered: Jan 2011 posted 02-28-2018 02:12 AM                     quote: Marcel Birgelen So, in your case, the passive crossovers in the 3 (or 5?) MF/HF units where bypassed and you do have specific HF outputs connected on your SG-01? Yes, exactly. And the Le/Re (former SDDS) speakers will remain but not connected. We will hook up a RTA on the outputs today and have a look. /M.E.  |  IP: Logged Marcel Birgelen Film God Posts: 3357 From: Maastricht, Limburg, Netherlands Registered: Feb 2012 posted 03-01-2018 08:31 AM                     I think I've quick-scanned the same manuals available on-line as you have and they indeed don't mention any specific cross-over frequencies for the MF/HF speakers. I suppose because they were initially not designed to be operated this way but with passive cross-overs only. If you've got access to an RTA and the box is still working, it should give you some answers. I suppose you're going to replace the SG-01 with some more up-to-date crossover solution?  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 03-01-2018 11:34 AM                     If you want to replace that X-over I'd go with something like a QSC x-over as it will likely have your speakers correct files in it's library already. Mark  |  IP: Logged Gunter Oehme Film Handler Posts: 17 From: Frankfurt, Germany Registered: Jun 2000 posted 03-01-2018 12:05 PM                     There was a 3 way active version of the speaker named Variplex (w/o 'B'). The data sheet for the 3 way active Variplex specifies 330 Hz LR 24 dB for LF/MF and 1560 HZ LR 24 dB for MF/HF xover. I've also got the EV recommended eq settings for the EV DSP controller EX34 which are for MF section: 740 Hz, Q=1.3, -3 dB and 1360 Hz, Q=1.6, +5 dB for HF section: 3000 Hz, Q=1.5, -7 dB and 5400 Hz, Q=2.2, -2 dB. These settings may be helpful as a starting point. Please note that there was a different speaker version Variplex II which was introduced around 2003. The Variplex II requires different xover frequencies and eq settings.  |  IP: Logged

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