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Author
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Topic: Seeking extension speaker advice
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Adrian Winchester
Film God
Posts: 2941
From: Croydon, London, UK
Registered: Aug 2004
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posted December 22, 2014 09:40 PM
Some time ago, I urgently needed a more powerful extension speaker for a shop I presented on 16mm and Super 8 in a hall. I don't use additional amplification but I needed a speaker that could cope with a 25 watt Eiki amp turned up fairly high. I opted to but this 100 watt PA speaker, which was amazing value at £29 including delivery:
http://www.astounded.com/pulse-pvs8-8-100w-passive-pa-speaker.html?cPath=262_7_49
Despite the price, I was generally impressed by the full-bodied sound this provided, which certainly beat the previous speaker I'd used. However, certain higher frequency sounds cause some distortion even though the speaker shouldn't be under strain. I'm not sure, therefore, if this means the speaker has a fault, or if it could possibly be something to do with using film projectors? It's said that projectors are not great in terms of higher frequency sounds, so I'm not sure if they could mean a problem in using a speaker?
Any thoughts - or perhaps speaker recommendations, if anyone has bought one for film use in medium-sized halls and been happy with it - would be appreciated.
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Adrian Winchester
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Steve Klare
Film Guy
Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003
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posted December 22, 2014 10:59 PM
The problem you run into is often external amps and/or speakers are actually too good for cinema sound purposes.
A long time ago when theatrical sound was first being refined, they found that a lot of nastiness went on in the higher end of the audio spectrum, and they rolled off the gain well below the 20 kHz that a really decent (young, usually) set of human ears can pick up, but it sounded better that way and remained the standard.
The GS-1200 as an example doesn't venture north of 12.5 kHz, and that's about as good as we have.
Now we go hanging really good external modern hi-fidelity equipment on that signal. Why should we worry? There's nothing up there in the teens , right? Well, no, there actually is. There is tape hiss and distortion and all sorts of stuff that doesn't sound very nice without benefit of "signal" to cover it up.
I run a pretty recent (and decent) external stereo amp and nice speakers with the audio outputs of my projectors and it sounds good, but one of the first things I had to do to civilize this setup is dial back the high frequency signal going into the amp.
I had to fool those speakers into thinking they weren't as good as they really are.
After the film, when I'm playing music through them they can go all out!
Probably the best thing you can do with what you are using is dial back your tone control if you have one.
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All I ask is a wide screen and a projector to light her by...
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Adrian Winchester
Film God
Posts: 2941
From: Croydon, London, UK
Registered: Aug 2004
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posted December 23, 2014 09:04 AM
Thanks for the further replies - I'll try some more tests, including trying to put another sound source through the speaker. This is 8 ohms so I'm sure I'm not overloading it. Ironically, despite the problem I've mentioned, part of the reason why I haven't been inclined to go to the expense and added work of incorporating a separate amp into my shows is that the combination of the projector (which always sounded fine via my previous speaker, which has no tweeter) and the new speaker has meant the best 16mm sound I've ever had! However that's no consolation when certain frequencies, particularly in relation to music, cause the distortion which might be the rubbing that Paul refers to. It may well be the speaker that's at fault, but I was hesitant to think that having bought it new.
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Adrian Winchester
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Paul Browning
Phenomenal Film Handler
Posts: 1006
From: West Midlands United Kingdom
Registered: Aug 2011
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posted December 23, 2014 09:30 AM
The voice coil rubbing in the magnet would cause the bass end to distort rather than the "top end" Adrian, the action of the peizo horn tweeter, acts without any moving parts like a speaker cone does. You could check this however, but you would need to take off the front grill to do this, and with out any power to the speaker hold your hands horizontal about centre of the speakers outer edge, flat hands to the cone, push up and down gently, you should not feel the voice coil rubbing on the fixed magnet, if you do, then this is not good news, and a fault of manufacturing if this is a new speaker. It should go back immediately for replacement, it can happen and does. If you have used this and has improved your sound from your 16mm projector, then it sounds fine, but the tweeter for me is where you should focus your attention, they always sound "screechy and harsh" no matter what you do with them.
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