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PA or ? for small room with low ceilings
Old 2nd April 2018
  #1
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PA or ? for small room with low ceilings

I hope someone can help me with my quandary.

I play solo and also in a duo in some very small pubs, and some have quite low ceilings. I use a Fishman SA220 when playing solo and add a mixer and a Yamaha DBR10 speaker for the duo. Some of these places are too small to have either speaker behind me, the only space is off to one side. There is often no room for monitors either. I have had feedback issues in the past with the SA220 and solved them by moving further away from the speaker. There are probably better ways to solve the issue, I am not technically minded but happy to learn.

I have a solo gig coming up where the room is approx 15' x 20', and the ceiling is approx 7' high. These are just general guesses from when I was in making the booking. I can't remember if there is carpet or not. I am slightly worried about feedback and wondering which option is going to be the best for this size room. I should add that the place will be packed, there is no way I could be heard without using amplification.

I use a Gibson J45 with a K&K mini pickup and a AKG D5 mic.

Thank you in advance for any advice!
Old 2nd April 2018
  #2
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The cardinal rule governing feedback is:

LOUDEST SOUND AT THE MIC WINS

So...

The stronger you sing, the easier it is to reduce the onset of the self-reinforcing feedback loop. If you've been letting the system do the work instead of having developed strong vocal muscles you're going to be limited in what you can achieve. In the mean time:

Use the mixer/speaker rig with the speaker as high as practicable. You might find that pointing it at the wall behind you will reflect the sound into the room enough to help project yet be diffuse enough to slightly reduce the onset of feedback. Having the ability to EQ the speaker with a PEQ will help, but it's a little late for a frash course in PA management.

Frankly, I'd just stand up (sit down and nobody's going to hear you anyway) in a corner and do your thing. Room noise : music have a self-leveling relationship. Use a PA and people will just chat louder to compensate. Keep your sound at a reasonable level and the chatter will stay at a more reasonable level. Plus there's an art to presentation that transcends mere volume. I play a regular date in a restaurant about 4x the size of the room you'll use. I don't use the PA, just sit high enough to get the guitar above peoples heads. Others use the PA. I do as well as anyone else and the staff appreciate the lower overall sound level.

Anyhoo...good luck. Accept it for what it is, don't fret (except the guitar) and find a way to enjoy yourself. If you're having a good time, so will those who want to listen. If they don't care to listen, PA won't help. Myself, if the musician is more involved with equipment and getting it to work rather than just playing, I'm out of there.
Old 2nd April 2018
  #3
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Thank you so much!

I have a relatively soft female voice so just singing in a noisy pub without amplification won't work, also the landlady has asked for it. Apparently the crowd at this pub love to sing along.

Projecting it towards the wall is something I will try. Which would be the best choice between the SA220 or DBR10?

Thank you again for your help.
Old 2nd April 2018
  #4
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The idea with turning the speaker around is to reflect the sound into the room in such a way as to minimize the direct return to the mic position...and to create a bit of delay as well. Put the speaker on a stand and raise it to within about a foot of the ceiling, more or less. Aim it toward the wall behind you and angle it toward the corner, sort of a "2 cushion billiards shot". EQ as needed and don't worry about monitoring. If you need to, amp the guitar with the other unit so you get a feel for it.

Good luck and SING OUT.
Old 2nd April 2018
  #5
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That's an interesting suggestion, Wyllys and not something I would have considered. Do you think it would be worth trying the back wall/ceiling angle instead, possibly doing away with the need for a stand and just putting the Yamaha speaker on a chair or table behind the performer (O/P) in the "wedge monitor" position?
Old 2nd April 2018
  #6
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Quote:
Originally Posted by shufflebeat View Post
That's an interesting suggestion, Wyllys and not something I would have considered. Do you think it would be worth trying the back wall/ceiling angle instead, possibly doing away with the need for a stand and just putting the Yamaha speaker on a chair or table behind the performer (O/P) in the "wedge monitor" position?
That wouldn't be my first choice, but you could try it and see. I think having the entire body of the speaker elevated is preferable and with the vertical orientation you have a lot more angles available simply by rotating the speaker on the stand instead of being limited to one basic monitor angle. Clearance to the ceiling is also adjustable with stand mounting, so even more positioning options.

We used to do small rooms like this to soften the sound and avoid slap-back off the facing wall.
Old 2nd April 2018
  #7
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Your valuable speaker is less likely to fall off a decent stand than a chair or table.
Old 2nd April 2018
  #8
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That's brilliant, thank you. I will definitely try that. Would the Yamaha be a better choice than the SA220?
Old 2nd April 2018
  #9
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Quote:
Originally Posted by OldBlue View Post
That's brilliant, thank you. I will definitely try that. Would the Yamaha be a better choice than the SA220?
I have a definite bias against every single one of the "affordable" (read cheap) column array units. Any half-decent single speaker will likely be able to put out more usable sound if you know what you're doing.
Old 2nd April 2018
  #10
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Thank you Wyllys, you are a star!
Old 3rd April 2018
  #11
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Try what Wyllys suggests as he has more experience than I but I do want to get one thing straight. Performing in front of your speakers is ALWAYS a bad idea. In principle you should always try to be behind the speakers if you can to minimise feedback.
Getting your gain staging right to can help a lot. I find that having the preamp gain higher than it should be is inducive to creating feedback.
Old 3rd April 2018
  #12
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Quote:
Originally Posted by AnthonyG View Post
Getting your gain staging right to can help a lot. I find that having the preamp gain higher than it should be is inducive to creating feedback.
Don't pick on the poor little preamp. Feedback is a SYSTEM phenomenon. Run ANY stage too hot and you'll likely run into problems with the noise floor, but in the end it's the TOTAL system gain exceeding the feedback threshhold which is the problem.

As I posted earlier, LOUDEST SOUND AT THE MIC WINS. If you want to (or must) sing softly and let the system do the work for you, the likelihood of feedback happening is higher than if you give the mic a strong signal...allowing you to use less overall system gain for performance.

If you're interested in understanding all the gain stages of a system, start with the microphone itself and consider its sensitivity. The output voltage sent to the next stage (preamp) varies according to the level of the input signal: stronger input, less preamp gain required. Whether the input level is varied by proximity or just by singing/speaking louder or softer, proper preamp setting is desired...that being enough to pass signal to the next stage at a usable level but not so hot that the loudest passages result in clipping. Here's a link:

Understanding Microphone Sensitivity | Analog Devices

Last edited by Wyllys; 3rd April 2018 at 01:45 AM..
Old 3rd April 2018
  #13
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Quote:
Originally Posted by Wyllys View Post
Don't pick on the poor little preamp. Feedback is a SYSTEM phenomenon. Run ANY stage too hot and you'll likely run into problems with the noise floor, but in the end it's the TOTAL system gain exceeding the feedback threshhold which is the problem.

As I posted earlier, LOUDEST SOUND AT THE MIC WINS. If you want to (or must) sing softly and let the system do the work for you, the likelihood of feedback happening is higher than if you give the mic a strong signal...allowing you to use less overall system gain for performance.
Sure its everything. Maybe on high end systems with clean preamps the preamp isn't a problem yet on some lower end systems that I have used I find I can get more volume before feedback from not going to high with the preamp and turning up the power amp instead.

If you really crank up some cheap preamps they will start squealing on their own without much power amp volume.
Old 3rd April 2018
  #14
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Quote:
Originally Posted by AnthonyG View Post
Sure its everything. Maybe on high end systems with clean preamps the preamp isn't a problem yet on some lower end systems that I have used I find I can get more volume before feedback from not going to high with the preamp and turning up the power amp instead.

If you really crank up some cheap preamps they will start squealing on their own without much power amp volume.
Your perceptions are what they are, but the math and physics eliminate the magic and voodoo. Feedback occurs when system gain passes the point where a self-reinforcing loop occurs. Whether "excessive" gain is added at the preamp, the channel fader, compressor make-up gain, master gain etc, it's the end-sum that matters. And BTW...

You don't "turn up" (or down) a power amp. They're fixed gain devices. The knob you're turning adjusts the the sensitivity to the input voltage. Turning it "up" means it takes less voltage output from your board for the desired level and turning it "down" means you need more from the board. You probably know this, but for the less experienced reader of the thread it's good to clarify so as not to reinforce a common myth.

Again, any system will have a point at which a feedback loop will start. This depends solely on the level of sound returning to the mic(s) from the speakers (either directly or from reflection) exceeding the critical point. It does not matter which of the various stages of gain are high or low, simply that the TOTAL SYSTEM GAIN has exceeded the critical point. For example:

Let us say that the quantity of sound required for the onset of feedback is X. Further, if for our purposes we give X a value of 10 and add up the values of each stage in the chain, it matters not what the value of each component may be so long as the sum is not greater than 10.

Sorry for the length of the explanation...
Old 3rd April 2018
  #15
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Quote:
Originally Posted by AnthonyG View Post
Try what Wyllys suggests as he has more experience than I but I do want to get one thing straight. Performing in front of your speakers is ALWAYS a bad idea. In principle you should always try to be behind the speakers if you can to minimise feedback.
Getting your gain staging right to can help a lot. I find that having the preamp gain higher than it should be is inducive to creating feedback.
Gain staging has nothing to do with feedback and does not influence it one way or another...
Old 3rd April 2018
  #16
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Quote:
Originally Posted by Samc View Post
Gain staging has nothing to do with feedback and does not influence it one way or another...
On high end systems it probably doesn't but then again anyone running a high end system will gain stage properly anyway.

If you take a cheap mixer and max out the preamp gain and only turn up the main sliders slightly then you should expect more feedback than if you gain staged the mixer properly.

That's my experience anyway.

EDIT. Well maybe your right and its a different issue. Maybe I'm talking about microphonics.
Old 3rd April 2018
  #17
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Thank you again for the replies. I will admit that before joining the forum, I didn't really understand what caused feedback aside from standing in front of speakers or pointing your mic towards the speaker. I'm still a beginner with a PA, I've been gigging with the Solo amp for years and only occasionally ran into feeback problems that I could usually solve by pointing the speaker away from me or moving further away from the speaker.

Now that I am playing more and more noisy pubs, I'm ditching the SA220 altogether and replacing it with another Yamaha DRB10 or similar, unless you can recommend a better quality lightweight speaker for a similar price. (£325) I'm not sure if the DBR10s are considered low quality speakers but for the moment they are what I can afford and are light enough that I can lift them on to the stand without too much trouble. I don't think I could comfortably lift more than 25lbs on to a speaker stand.
Old 3rd April 2018
  #18
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Quote:
Originally Posted by AnthonyG View Post
On high end systems it probably doesn't but then again anyone running a high end system will gain stage properly anyway.

If you take a cheap mixer and max out the preamp gain and only turn up the main sliders slightly then you should expect more feedback than if you gain staged the mixer properly.

That's my experience anyway.
Despite your impression, this is not true in practice, and is not supported by the science and can easily be debunked in a simple, practical test.

Quote:
EDIT. Well maybe your right and its a different issue. Maybe I'm talking about microphonics.
Wyllys already gave an explanation above, but you can read about the cause of feedback easily, there are several articles on the subject.
Old 3rd April 2018
  #19
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Quote:
Originally Posted by Samc View Post
Wyllys already gave an explanation above, but you can read about the cause of feedback easily, there are several articles on the subject.
In real life scenarios bad gain staging at various points in the chain caused be users not understanding what their system requires or is capable of can result in distortion and feedback due to the processes outlined by Wyllys.

I don't see why these things ahave to be mutually exclusive.

[Edit] I think I know what you're getting at, simple (?) physics is ultimately the process at play but I think what AntG is suggesting is that inappropriate upstream g/s causes feedback when folks to turn up (channel) inputs beyond the (system) feedback point because they get little volume gain due to clipping at that point..
Old 3rd April 2018
  #20
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Quote:
Originally Posted by OldBlue View Post
Thank you again for the replies. I will admit that before joining the forum, I didn't really understand what caused feedback aside from standing in front of speakers or pointing your mic towards the speaker. I'm still a beginner with a PA, I've been gigging with the Solo amp for years and only occasionally ran into feeback problems that I could usually solve by pointing the speaker away from me or moving further away from the speaker.

Now that I am playing more and more noisy pubs, I'm ditching the SA220 altogether and replacing it with another Yamaha DRB10 or similar, unless you can recommend a better quality lightweight speaker for a similar price. (£325) I'm not sure if the DBR10s are considered low quality speakers but for the moment they are what I can afford and are light enough that I can lift them on to the stand without too much trouble. I don't think I could comfortably lift more than 25lbs on to a speaker stand.
The DBR10 is certainly a useable speaker and lightweight. You may not need a second one unless playing a much larger space. One thing to watch for is the control knobs stick out on the back and can get damaged during transport.

Interestingly, I found that my DBR10 will fit inside two of these milk crates--one on the bottom, another on the top like a sandwich. https://www.homedepot.com/p/GSC-Tech...-002/204793156 This helps protect those knobs. the crates are fairly cheap. Some of the crates from other places are just a bit smaller than the ones I linked and won't work.

You can strap two DBX10s to a rocknroll cart in milk crates using ratchet straps. Strap your speaker stands...off you go.

The DBX10 is a higher end model, but more $.
Old 3rd April 2018
  #21
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Quote:
Originally Posted by AnthonyG View Post

If you take a cheap mixer and max out the preamp gain and only turn up the main sliders slightly then you should expect more feedback than if you gain staged the mixer properly.
Good gain staging is desirable. Agreed. But...

You're drawing unsupportable albeit common conclusions regarding system feedback. If you actually measure what's happening rather than just assuming, you'll find the math is based strictly on voltage, not the quality (or lack thereof) of the system components. If preamps of lesser quality perform poorly, the reality regarding feedback would almost cerainly be related to inconsistent voltage levels rather than "poor sound" and distortion...NOT from any bad juju. Additionally, any judgements made should come from IDENTICAL system setups in IDENTICAL conditions. Casual assessments based on various room/system interactions have more variables than preamp quality and gain staging...

BTW...tchnically, you cannot have "more feedback". Once the threshhold of feedback is crossed, the system enters feedback mode. It's black and white, not more or less.

Edit:

Sam could probably say all this in a single sentence.

Last edited by Wyllys; 3rd April 2018 at 01:04 PM..
Old 3rd April 2018
  #22
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Quote:
Originally Posted by OldBlue View Post
Now that I am playing more and more noisy pubs, I'm ditching the SA220 altogether and replacing it with another Yamaha DRB10 or similar, unless you can recommend a better quality lightweight speaker for a similar price. (£325) I'm not sure if the DBR10s are considered low quality speakers but for the moment they are what I can afford and are light enough that I can lift them on to the stand without too much trouble. I don't think I could comfortably lift more than 25lbs on to a speaker stand.
Sounds like you're taking a reasonable course. Just remember that adding speakers will allow you to cover a WIDER area more evenly. It will not necessarily give you a USABLE increase in overall output...volume-wise.

For the info on speaker alternatives, see if you can contact forum member dickiefunk. He's down in Devon, I think, and has probably gone through most of the available candidates in your category in the past 3 or 4 years. Ask about Alto.
Old 3rd April 2018
  #23
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Thank you Wyllys, I have sent dickiefunk a message.

Thanks as well 2manyrocks for the milk crate advice. I'm sure there is a similar alternative available here in the UK so will have a look.
Old 3rd April 2018
  #24
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Quote:
Originally Posted by shufflebeat View Post
In real life scenarios bad gain staging at various points in the chain caused be users not understanding what their system requires or is capable of can result in distortion and feedback due to the processes outlined by Wyllys.

I don't see why these things ahave to be mutually exclusive.

[Edit] I think I know what you're getting at, simple (?) physics is ultimately the process at play but I think what AntG is suggesting is that inappropriate upstream g/s causes feedback when folks to turn up (channel) inputs beyond the (system) feedback point because they get little volume gain due to clipping at that point..
I stand by my statement:

Gain-staging has NOTHING to do with feedback, and while no one denies the importance of good gain-staging, the claim that the lack of good gain-staging causes feedback is incorrect. The other argument that low-end preamps will cause feedback if you push them hard is grossly false and misleading in every sense...!

I'm not trying to get at anything here, the physics that governs this is very clear and leaves nothing to the imagination...what you describe above is the incompetence of users which is a different thing.

Quote:
Originally Posted by Wyllys View Post
Edit:

Sam could probably say all this in a single sentence.
From Wiki, in a nutshell:
"Audio feedback (also known as acoustic feedback, simply as feedback, or the Larsen effect) is a special kind of positive loop gain which occurs when a sound loop exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for example, a power amplified loudspeaker)."
Old 3rd April 2018
  #25
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Quote:
Originally Posted by Samc View Post
.what you describe above is the incompetence of users which is a different thing.
OK, what are you calling incompetence that isn't incorrect gain staging that leads to feedback?

To be honest I doubt you guys ever run a PA that isn't properly gain staged.

I suspect that the problem that I'm talking about is actually microphonic squeal from cheap preamps.
Old 3rd April 2018
  #26
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Quote:
Originally Posted by Samc View Post
I stand by my statement:

Gain-staging has NOTHING to do with feedback, and while no one denies the importance of good gain-staging, the claim that the lack of good gain-staging causes feedback is incorrect. The other argument that low-end preamps will cause feedback if you push them hard is grossly false and misleading in every sense...!

I'm not trying to get at anything here, the physics that governs this is very clear and leaves nothing to the imagination...what you describe above is the incompetence of users which is a different thing.


From Wiki, in a nutshell:
"Audio feedback (also known as acoustic feedback, simply as feedback, or the Larsen effect) is a special kind of positive loop gain which occurs when a sound loop exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for example, a power amplified loudspeaker)."
Ok, apologies. I'm not making myself clear.

Imagine the scenario (I've seen this in real life):

Numpty #1 (talent) plugs an sm58 into his little mixer and from there into the house system via 2x RCA phonos on the wall.

Numpty #2 (behind the bar) decides #1 is too loud. It's not really that loud, it just sounds crap because control is limited and #1 doesn't know what he's doing. #2 turns the system down at the power amp behind the bar.

Hearing that he's got even quieter #1 turns his system up gradually on all faders, eventually including the channel gain, which he normally doesn't touch because he was told not to by a friend, numpty #3 (me).

The channel gain is well above ideal and #1 is torn between singing/playing quietly in order to minimise clipping/distortion and shouting to be heard.

The gradual increases are reciprocally followed by #2 attenuating the signal at the power amp.

Eventually #1 asks #2 to turn it up so someone can hear something, at which point nothing musical is happening and system is well into feedback.

#1 calls me, I explain the situation to both and everyone lives happy ever after.

Now, anyone with a tiny bit of knowhow would have avoided this, they didn't. Everything yourself and W have said is what's going on but (I think) this is the situation AntG was suggesting.

Are we approaching consensus at all?
Old 3rd April 2018
  #27
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Quote:
Originally Posted by AnthonyG View Post
I suspect that the problem that I'm talking about is actually microphonic squeal from cheap preamps.
My understanding is that microphonic squeal happens when guitar pickups do not have a gain knob and are in effect wide open and squeal/feedback when the amp is loud and the guitar is close enough, classic feedback scenario and has nothing to do with the quality of the feedback per say.

Please read the Wiki article or any number of articles on the net about acoustic feedback.
Old 3rd April 2018
  #28
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Quote:
Originally Posted by Samc View Post
My understanding is that microphonic squeal happens when guitar pickups do not have a gain knob and are in effect wide open and squeal/feedback when the amp is loud and the guitar is close enough, classic feedback scenario and has nothing to do with the quality of the feedback per say.

Please read the Wiki article or any number of articles on the net about acoustic feedback.
As an ex-punk guitarist many moons ago I can attest that there are different kinds of guitar feedback, some based on interaction with the strings, others interaction with the pickup, all subject to the usual laws but qualitatively different and good pickups make for much more musical feedback.
Old 3rd April 2018
  #29
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Quote:
Originally Posted by AnthonyG View Post
I suspect that the problem that I'm talking about is actually microphonic squeal from cheap preamps.
AG...

I don't want to beat you up on this, but the above phenomenon exists only in your mind as a personal supposition regarding what causes audio feedback and has no basis in actual fact. You also stated:

"If you really crank up some cheap preamps they will start squealing on their own without much power amp volume."

The test you need to do would be to have NO INPUT into the preamp. If turning it up full produces a loud shrieking noise, then, yes, there's something faulty with the preamp...but it's not feedback. Are you really serious in making this statement?

Do yourself a favor and read the Wiki Sam linked above. If you want a good reference book, I suggest the Yamaha Sound Reinforcement Handbook...aka "The Bible".

Good luck.

Last edited by Wyllys; 3rd April 2018 at 05:33 PM..
Old 3rd April 2018
  #30
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I've described above two distinct (experientially) types of feedback. The amp/strings feedback responds to manipulation of the strings, direct amp/pickup feedback doesn't.

The mechanics are the same but in the first the energy is mediated via the strings. It's the same for acoustic guitars except for the musicality part.
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