| Optimizing An Old Gym System [message #323296] |
Thu, 15 May 2008 22:53  |
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 Dan Brandesky
Messages: 685
Registered: February 2006
Location: Lima, OH |
Has No Life |
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Ok, you all are going to laugh at me. I volunteered to do what I could to try to optimize the PA system in the gym at my (relatively small) university campus. The system is comprised of two Altec Lansing Voice Of the Theatre low frequency boxes of some sort, and 8 Atlas paging horns. The LF boxes are in opposite corners, hung from the ceiling pointing toward the stands on the other side of the gym. The horns are in a circular array (roughly) in the center of the gym. I realize time alignment is probably terrible, but my main concern is just making this system as good as it can sound as it is. Right now the only processing they have is a DOD crossover which is kind of oddly set up, and someone has messed with the crossover points so it's definitely not right. I am going to try to see if they can afford a better crossover and/or maybe a 1/3 octave graphic EQ to do a little bit of system tuning (as well as lockout panels for both).
My question is mainly what the appropriate crossover points for this system might be, as well as advisable high pass and low pass points. I'm also going to see if I can adjust the speaker wiring too; the rack that powers the speakers (via a Crown Com Tech 410) is mobile, so there are two wall jacks on the wall for the speakers, but neither is labeled in terms of low and high. I'm thinking of seeing if I can swap their 1/4" panels out for a single NL4 speakon so it's fairly idiot proof.
Anyway, I know I'm crazy for taking this on, but it actually sounds relatively decent, and I'd like to make it even better for them. It is doubtful that they can justify buying a new system at this point, and there is not much money to spare after athletic equipment needs are met, so I'm just working with what I can do on the cheap.
Thanks,
Dan
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| Re: Optimizing An Old Gym System [message #323333 is a reply to message #323296 ] |
Fri, 16 May 2008 07:26  |
Tom Young
Messages: 1750
Registered: April 2004
Location: Oxford CT |
Has No Life |
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How certain are you that the VOT's do not have HF horns within them ? If they do, there will be a crossover mounted on the back of the enclosures with input jacks and a HF level control.
How certain are you that the "paging horns" are not Altec 811 (or similar) HF horns ? These may look to you like paging horns but they may be better than that.
Tom Young
Electroacoustic Design Services
Oxford CT
Tel: 203.888.6217
Email: dbspl@earthlink.net
www.dbspl.com
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| Re: Optimizing An Old Gym System [message #323446 is a reply to message #323296 ] |
Fri, 16 May 2008 12:57 |
Brad Weber
Messages: 1253
Registered: December 2005
Location: Marietta, GA |
Has No Life |
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Just to add to the great information you already received, in general it is impossible to properly address crossovers, high and low pass filters, etc. without knowing a lot more about the actual products and system configuration involved. If those are indeed paging horns then you might even have a number of different drivers that could be mounted to the same horn with very differing responses. It would most definitely be real useful to verify the existing products and wiring.
Brad Weber
muse Audio Video
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| Re: Optimizing An Old Gym System [message #323451 is a reply to message #323431 ] |
Fri, 16 May 2008 13:01 |
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Dan Brandesky
Messages: 685
Registered: February 2006
Location: Lima, OH |
Has No Life |
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Yeah, I figured it would be a rather challenging setup.
I can see from the ground that the horns are Atlas horns, and it would seem most logical that they would install paging horns in a gym. I doubt the system was originally designed for music playback really. I might be able to get a picture of the Altec boxes sometime, but from what I can see, there is a LF driver set back in the cabinet, and at the bottom there is a small band of grille cloth, I'm guessing for a port, but I could be wrong. I might be able to see if I can turn off/disconnect the paging horns and see what the Altec boxes sound like alone. I will probably be able to start messing with this setup maybe next week, so I'll post back with more info as I find out more.
-Dan
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| Re: Optimizing An Old Gym System [message #323479 is a reply to message #323451 ] |
Fri, 16 May 2008 13:54 |
Tom Young
Messages: 1750
Registered: April 2004
Location: Oxford CT |
Has No Life |
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If the Altec VOT's have a HF horn inside, these may be blown. So listening may tell you nothing.
Again: if these are 2-way "fullrange" versions of the VOT, they will have an Altec crossover installed into the back. Finding this is *evidence* that there may be a HF horn on the inside as well as the horn-loaded woofer. You still need to determine that the HF horn was not removed and that it is functioning.
Your chances of achieving something workable are much better if these are functioning 2-way VOT's. Ohterwise, I think you are way too restricted in what can be achieved.
Tom Young
Electroacoustic Design Services
Oxford CT
Tel: 203.888.6217
Email: dbspl@earthlink.net
www.dbspl.com
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| Re: Optimizing An Old Gym System [message #323487 is a reply to message #323482 ] |
Fri, 16 May 2008 14:14 |
Tom Young
Messages: 1750
Registered: April 2004
Location: Oxford CT |
Has No Life |
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The VOT was widely used during its hayday and I think it was avaliable in three forms: with no HF horn/driver, with a HF horn/driver bolted on top and with the HF horn/driver installed into the grill-cloth covered "port". But I am not 100% sure about the last option. I may be confusing this with JBL, who offered a horn loaded system (4560) configured these ways.
You can figure this out by googling on "Altec Heritage" and visiting the website where pretty much all of the spec sheets and catalogs for Altec and JBL are archived.
Of course once you determine if this option was provided by Altec, you still are faced with the possibility that the installer "customized" the two VOT's in this system and they do or do not have a HF horn inside. Believe me; there were many such hot-rodded VOT's around back then.
My gut tells me the original installer was not lame enough to rely solely on Atlas paging horns for HF's / intelligibiity and that you will find HF horns in the VOT's. But I am not sure why I am so optimistic....... there were just as many (or more) "clowns" around back then.
Tom Young
Electroacoustic Design Services
Oxford CT
Tel: 203.888.6217
Email: dbspl@earthlink.net
www.dbspl.com
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| Re: Optimizing An Old Gym System [message #323496 is a reply to message #323482 ] |
Fri, 16 May 2008 14:42 |
Brad Weber
Messages: 1253
Registered: December 2005
Location: Marietta, GA |
Has No Life |
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| Dan Brandesky wrote on Fri, 16 May 2008 14:58 |
Thanks Tom. So does anyone know, just to narrow down the possibilities, if there ever was a VOT model that only had a LF driver with no HF?
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Sure, there were several, in fact many of VOTT speakers were a low frequency enclosure with a horn mounted on top. The traditional 828 cabinets did have grille cloth across the bottom but it was about half the enclosure height and not just a narrow band. The 816 and 817 models had smaller ports across the bottom but no grille cloth.
Brad Weber
muse Audio Video
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