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Author Topic: Power Amp Speaker Wiring Question  (Read 1431 times)

Dave Garoutte

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Re: Power Amp Speaker Wiring Question
« Reply #10 on: May 14, 2019, 03:08:42 pm »

Think I'd still want that lot replaced with an SpeakOn connector. Banana plugs like these are not for PA applications.

Also, the speaker wiring on the next amp down needs tidying up.

Chris

I agree that speakons are better, but it seems to me, that if the banana plugs weren't adequate, the amp builder would not have put them on their amp.
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Chris Grimshaw

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Re: Power Amp Speaker Wiring Question
« Reply #11 on: May 14, 2019, 04:51:39 pm »

I see your point, but I more meant the fact that they're gold-plated all the way along. If you put a little weight on the top one, I bet you could get it to short the amp's output.

Chris
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Luke Geis

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Re: Power Amp Speaker Wiring Question
« Reply #12 on: May 14, 2019, 05:20:36 pm »

Aside from some gain staging aspects of how your system operates, it seems to me that all is fine. Being at -20 on the faders isn't a huge deal, but that is relative to what other things are going on. If the master fader is down to -20 as well and you have that kind of volume, it could be because of the way the channels are grouped. If you group the channels into multiple groups and buss all those groups to the main you gain +3db for every buss doubling. With a 4 group console that means you have a potential 9-12db boost just from double bussing.

My answer would be to have the system run either in stereo or simply mono, but not bridged mono. The bridging of the amplifier may very well add more wattage than is needed to meet your NAG (Needed Acoustic Gain ). By making the amp run in the more common mono mode, you would have half the potential wattage being produced. This may allow you to run the level of the amp up more and still have a reasonable adjustment at the mixer.

If you don't need any kind of grouping, it would behoove you to simply eliminate that part of the signal flow. What many operators do is run the channel to both the group and the main L/R in order to get a little more volume. If you don't want added volume, then getting rid of the groups will help. You can turn the master volume down as far as you need to in order to get the channels up to where you want them. In some cases, this helps greatly with record feeds and other feeds that come off the mixer that do need to have a hotter signal.

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Scott Holtzman

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Re: Power Amp Speaker Wiring Question
« Reply #13 on: May 15, 2019, 03:06:43 am »

Aside from some gain staging aspects of how your system operates, it seems to me that all is fine. Being at -20 on the faders isn't a huge deal, but that is relative to what other things are going on. If the master fader is down to -20 as well and you have that kind of volume, it could be because of the way the channels are grouped. If you group the channels into multiple groups and buss all those groups to the main you gain +3db for every buss doubling. With a 4 group console that means you have a potential 9-12db boost just from double bussing.

My answer would be to have the system run either in stereo or simply mono, but not bridged mono. The bridging of the amplifier may very well add more wattage than is needed to meet your NAG (Needed Acoustic Gain ). By making the amp run in the more common mono mode, you would have half the potential wattage being produced. This may allow you to run the level of the amp up more and still have a reasonable adjustment at the mixer.

If you don't need any kind of grouping, it would behoove you to simply eliminate that part of the signal flow. What many operators do is run the channel to both the group and the main L/R in order to get a little more volume. If you don't want added volume, then getting rid of the groups will help. You can turn the master volume down as far as you need to in order to get the channels up to where you want them. In some cases, this helps greatly with record feeds and other feeds that come off the mixer that do need to have a hotter signal.
The Samson SX series amps say 8 ohm only in bridge mode any lower and you risk damaging the amps.  The fact they are stacked, unless they are 16 ohms you are in a bad spot.

The concept that the amps are "not working hard" because they are set at 9 o'clock is a false premise.  It simply means a larger signal must be applied to drive the amp to full power.

That speaker cable is woefully inadequate.  No way this was a pro install.

Sent from my VS996 using Tapatalk

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Tim McCulloch

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Re: Power Amp Speaker Wiring Question
« Reply #14 on: May 15, 2019, 10:48:12 am »

I'm not fully saying I want to change it but something in this system isn't right. My wife and I are taking over as worship directors and I'm trying to get an idea of how things are set up so I have the knowledge. I work in IT and I'm used to knowing what systems I work with in case something goes wrong. Plus, it serves as an excuse for me to finally learn how power amps and speakers work.

No one truly seems to know how things are set up and the mixer doesn't work the way I'd expect it to. For instance, during a normal service that's run a little loud; the channel and group faders (incl mains) are set around -20, the gain for the channels are not set high, the mixer shows main output at around -16, and the power amp level is set at 9 o'clock where the lowest possible is 8 o'clock. Needless to say it doesn't give the sound tech a whole lot of "room" to work with on the mixer when mixing near -20 and most gain knobs set to 0. Just seems like the whole system was set up for a rock concert as opposed to a house of worship.

So this started with me just being curious/wanting to learn and the deeper I dig the weirder things seem.  :o

This sounds like a console gain-staging issue, mostly, but there could be other things going on and we'll need a LOT more info to suss it all out.

First, what console?  If it's a digital mixer with metering in DBFS (dB full scale), -18 is the close equivalent of an analog mixer mechanical meter reading at 0 dB Vu. 

{quick story} When our shop got our first Yamaha M7, my Olde Analogue Guy boss wanted to play with it in the shop.  He got a CD to play through it and and microphone to work.  He called me, happy that he'd gotten the new technology to work, but told me "these things have LOTS of gain and the faders need to be down really far."  He's an old analog guy with a practice of "PFL the input, set the channel gain so the meter reads 0 dBVu".  The M7 has metering in DBFS, which is almost 20dB hotter at -0- (at that point the console has no more "1s" in the digital inventory).  Once he understood that -18 DBFS is the new "zero VU" the console operation was normal for him. {/quick story}   Could this be what you're seeing?

Seeing input gains all set at the "zero" or "unity" (I could eviscerate Greg Mackie's marking people for that BS concept of setting input gain) means someone bought into the Mackie marketing hype from 25 years ago and the BS still has impact.

If the input gains are set more or less as I described in the story (but so the inputs peak at -18ish on the meters, if DBFS metering), the problem is down stream of the console, and that will require answers to more questions, some pictures and maybe a signal flow diagram.

The Samson amps would not be my choice for anything except a frat house basement PA, broke musicians playing bars, etc. but my standards are fairly high.  If it's working, there is no need to replace it.

Is your issue with the system 1) held by others and 2) based solely on the observed fader positions?
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Andrew Cole

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Re: Power Amp Speaker Wiring Question
« Reply #15 on: May 15, 2019, 11:57:44 am »

The Samson SX series amps say 8 ohm only in bridge mode any lower and you risk damaging the amps.  The fact they are stacked, unless they are 16 ohms you are in a bad spot.

The concept that the amps are "not working hard" because they are set at 9 o'clock is a false premise.  It simply means a larger signal must be applied to drive the amp to full power.

That speaker cable is woefully inadequate.  No way this was a pro install.

Sent from my VS996 using Tapatalk

The whole system is probably...20 years old with various smaller "upgrades" done along the way. I'm guessing it may have been a pro install and then modified over the years. Thanks for the info on the amp signal! Also, how far east does your company go? I'm over in Geauga county and if we try to upgrade in the future I can keep you guys in mind.

This sounds like a console gain-staging issue, mostly, but there could be other things going on and we'll need a LOT more info to suss it all out.

First, what console?  If it's a digital mixer with metering in DBFS (dB full scale), -18 is the close equivalent of an analog mixer mechanical meter reading at 0 dB Vu. 

Seeing input gains all set at the "zero" or "unity" (I could eviscerate Greg Mackie's marking people for that BS concept of setting input gain) means someone bought into the Mackie marketing hype from 25 years ago and the BS still has impact.

The Samson amps would not be my choice for anything except a frat house basement PA, broke musicians playing bars, etc. but my standards are fairly high.  If it's working, there is no need to replace it.

Is your issue with the system 1) held by others and 2) based solely on the observed fader positions?

Tim,

The console is an old Allen & Heath GL2200 so it's not using DBFS. I've heard Samson amps don't have a glowing reputation but maybe they'd be OK in the future serving for monitors?

In response to input gains @ 0 and my issue: FWIW I was taught to set gain by putting the fader at 0/unity and bring the gain up to where the level meter shows near 0. At that point use the faders/groups to adjust the mix. So seeing how this board ran with most gain @ 0 and faders super low just through me for a loop especially since if I tried to set the gain my way I'd have to turn all the input gains way way down. Maybe the way I've always done it/ been taught is wrong? Also, I've spent most of my mixing time on a X32 and not an analog. So I suppose my issue was that the setup (which seems to work ok) is completely different from what I'm used to.
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Taylor Hall

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Re: Power Amp Speaker Wiring Question
« Reply #16 on: May 15, 2019, 12:04:29 pm »

The Samson SX series amps say 8 ohm only in bridge mode any lower and you risk damaging the amps.  The fact they are stacked, unless they are 16 ohms you are in a bad spot.


That's interesting since his first photo shows a little "4ohm min" annotation nested in the bridging diagram by the screw terminals.
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Tim McCulloch

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Re: Power Amp Speaker Wiring Question
« Reply #17 on: May 15, 2019, 04:15:15 pm »

The whole system is probably...20 years old with various smaller "upgrades" done along the way. I'm guessing it may have been a pro install and then modified over the years. Thanks for the info on the amp signal! Also, how far east does your company go? I'm over in Geauga county and if we try to upgrade in the future I can keep you guys in mind.

Tim,

The console is an old Allen & Heath GL2200 so it's not using DBFS. I've heard Samson amps don't have a glowing reputation but maybe they'd be OK in the future serving for monitors?

In response to input gains @ 0 and my issue: FWIW I was taught to set gain by putting the fader at 0/unity and bring the gain up to where the level meter shows near 0. At that point use the faders/groups to adjust the mix. So seeing how this board ran with most gain @ 0 and faders super low just through me for a loop especially since if I tried to set the gain my way I'd have to turn all the input gains way way down. Maybe the way I've always done it/ been taught is wrong? Also, I've spent most of my mixing time on a X32 and not an analog. So I suppose my issue was that the setup (which seems to work ok) is completely different from what I'm used to.

Hi Andrew-

Your method is close to the "PFL to 0 vu" that the resulting input gain should be close to the same.  Give it a try both ways and see if there is a difference.  Good to know you're familiar with the differences in metering scales; you a couple steps ahead.

Yeah, it probably would be a good idea to call a team rehearsal and take a look at levels.  Does the console feed other down stream items like lobby or nursery?  A recording or streaming feed?  Hearing assistance system?  Particularly if the sends are derived pre-fader, reducing input gain will require that lost level be made up elsewhere.

At 20 years old I think your review of the system is understandable.  Other than console operation being inconvenient what aspects of the system are you questioning?
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Mac Kerr

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Re: Power Amp Speaker Wiring Question
« Reply #18 on: May 15, 2019, 04:56:31 pm »

Hi Andrew-

Your method is close to the "PFL to 0 vu" that the resulting input gain should be close to the same.  Give it a try both ways and see if there is a difference.  Good to know you're familiar with the differences in metering scales; you a couple steps ahead.

Yeah, it probably would be a good idea to call a team rehearsal and take a look at levels.  Does the console feed other down stream items like lobby or nursery?  A recording or streaming feed?  Hearing assistance system?  Particularly if the sends are derived pre-fader, reducing input gain will require that lost level be made up elsewhere.

At 20 years old I think your review of the system is understandable.  Other than console operation being inconvenient what aspects of the system are you questioning?

It also seems the system just plain has too much gain. The first thing I would do is get rid of the bridged mode on the amp. Switch it to parallel instead of bridged and put one banana plug in ch1 and the other in ch2. You will lose 6dB of unwanted gain just by that.

If excessive noise is not an issue can certainly run the mic input gains a little lower as well.

Mac
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Tim McCulloch

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Re: Power Amp Speaker Wiring Question
« Reply #19 on: May 15, 2019, 10:48:32 pm »

It also seems the system just plain has too much gain. The first thing I would do is get rid of the bridged mode on the amp. Switch it to parallel instead of bridged and put one banana plug in ch1 and the other in ch2. You will lose 6dB of unwanted gain just by that.

If excessive noise is not an issue can certainly run the mic input gains a little lower as well.

Mac

Mac, that was where I was going next, depending on the OP's input gain findings.

The use of that amp isn't fully clear, either, but we're presuming it powers 2 full range loudspeakers and I'm in full agreement about not bridging.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

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Re: Power Amp Speaker Wiring Question
« Reply #19 on: May 15, 2019, 10:48:32 pm »


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