their new systems, some have called and said they are having problems and going to return their Bose and purchase a conventional sound system.

When I asked about the nature of their problem, I quickly discovered that many of them never cracked the instruction (user) manual. They just plugged in the amp, plugged their keyboards into the inputs, turned everything on and expected perfection. BIG MISTAKE!

In some instances I drove to where they were playing and checked out the systems. Others were just too far away to drive to, therefore, I was able to solve the problem(s) over the telephone. In all cases, with the exception of one, they were elated at the overall sound they're now hearing and would never consider returning the systems.

Most of the problems were associated with Gain Staging, which is essentially a balance between the keyboard and the amp's input. If you are using the Standard Bose L1, you'll find detailed instructions for gain staging in both the user manual, and on the Bose website.

For those that recently purchased the L1 Compact, the process of gain staging is quite similar, but not as complex. Basically, the master volume of the keyboard should be set somewhere between 12:00 and 1:00 O'clock position--no higher. The same is true with the Bose L1 Compact's master volume. It should be set somewhere between 11 and 12 O'clock, but can be cranked up a bit higher when necessary.

This balance between the output and input devices is in compliance with most manufacturers recommendations and specifications. The vast majority of the sound systems I've worked with over the past 50 years operate at peak efficiency when the master volume and input mixer volumes are set at or near the 50 percent level. This usually results in the cleanest signal from both both the output device (keyboard, guitar, electric piano, etc..), and the amplifier output. If either device is cranked up too high, this will usually result in distortion of low and mid frequency sounds.

Almost forgot. One of the best aspects of using a balanced system, either conventional or Bose' vertical arrays, is that once the system is balanced, and if later during the event you decide you need either more, or less, volume, the only volume control you need to adjust is the amp's main volume. Granted, if you crank the amp's master volume too high you can produce distortion, but you would really have to go well beyond the normal limits of the amp to have this sort of problem. Additionally, the keyboard, guitar, etc.. output volume, and the amp's input volumes should NOT be adjusted once the system is balanced, or with the Bose systems, gain staged.

Hopefully, this will be helpful to those that are thinking about purchasing a new sound system.

Good Luck,

Gary

So many "problems" can be solved if only people would RTFM.

We live in an age where folks can't seem to take the time to crack the manual -- yet they can find plenty of time to fill up internet forums with long diatribes about how bad they perceive a device to be -- only because the PEBKAC.

My day job is as a design EE.

They flog us towards the end of every new project to get that user manual written, edited and ready to go.

And then the product goes to market.

And then the same old, same old starts.

On top of all that, we are then castigated if we answer the Customer Support line and have the unmitigated gall to tell the consumer that the answer to their perceived problem is on page two of the manual in bold...

As user equipments get laden with more and more features, the complexity involved requires the user to educate themselves concerning not only the operation of their new equipment, but in certain practices and terminologies that are common to all pieces of gear like the one they just purchased.

Gain Staging is certainly one of those common terminologies and practices.

The price paid for a piece of gear does not include one-on-one tutoring costs.

Not yet, anyway...


--Mac

[This message has been edited by --Mac (edited 01-08-2010).]

OTOH, Bose, for whatever pigheaded reason they chose to do so, fly in the face of donkey's years of a perfectly good system on how gain stages OUGHT to be set up...

In other words, why do they have to reinvent the wheel, and make their owners learn an entirely different way of doing something that works perfectly well the way it is on other gear? It's just a simple gain stage, it's not rocket science. Except, of course, Bose would like to pretend that it IS...

BTW, most mixers operate at their quietest when the channel fader is at unity, and the mixer main output is set to unity, and you only crank the input gain as little as is necessary. Channel fader and main fader are ATTENUATORS (at least, up to the unity point), it's the channel INPUT that is an op amp, and can introduce noise and distortion if sett too high (mind you, most modern op amps are pretty darn good through most of their range, these days). But set it too high, and what you are doing is ADDING amplification (and noise and distortion) to your signal, then turning it back DOWN again with the channel and main faders. Which doesn't get rid of the noise the input amp added.

That's not a good idea!

But Bose have decided to eschew decades of experience, have decided to eschew just about any metering on the unit (ONE overload LED that doesn't even tell you WHERE the overload is? ) and makes you toss away everything you have learned over the years, just so they can LOOK different (but internally, the same stuff is going on)...

That's just plain arrogant... Were I a Bose user, first thing I'd be griping about (after the lack of even a barebones reverb) is this confusing system and lack of any metering. When I see an overload LED flash, I want to know is it the preamp or the power amp that is clipping... You know...

Troubleshooting, 101.

Most people don't NEED to read a manual about this. It's been done like this for decades. Only Bose think that it needs changing. Crazy...

Diki,

I agree with some of what you stated, however, when you said "Most people don't need a manual..." this has never been the case, at least with most of the musicians and entertainers I know. They are very talented when it comes to hitting the correct chords and singing the right notes, but that's about as far as it goes.

And, I really don't believe Bose is doing anything differently than anyone else when it comes to gain staging--they've just put the information out in a readily understandable, step by step format that is easy to follow.

I assume when you refer to "Unity" you are referring to the most efficient or effective range of the system, which from what I learned many years ago in the U.S. Navy's electronic school, is usually slightly above mid level. And, from my experience, this has always been the level that produces the best signal to noise ratio (SNR). Unfortunately, a lot of folks just do not know this, or as Mac and others will tell you, they don't want to take the time to learn.

I think we are both saying the same things, just in different ways.

Cheers,

Gary

That is erroneous information.

First, the lowest thermal noise setting would happen when the Mic fader is turned up high and the Master fader is down low. Matter of fact, this is the way to properly set up a Mixer, whether for live performance or recording. Mic input at about the 70% point and Master Output fader down around the 20% point as starting places.

The faders typically control the negative feedback of an amplifier circuit. This is a pretty clean situation and should be described as something other than "attenuation" when the sig is low.

To call a Mic Sig "unity" doesn't make sense. Will let that pass, though.

Before it starts, all I do is design 'em, after years of experience at the repair bench...


--Mac

Sorry, guys, but I was always told that the 'unity' point of a fader is where it neither adds gain nor subtracts with attenuation. And that point varies from fader to fader based on design, taper, etc.. But it IS marked on most mixers.

I was also told that overloading the input gain, and then reducing it at a fader is the quickest way to mess up your signal. So, in general, I have always run my mixers with faders up to unity (but not exceeding it) and with as little input gain as is necessary. Make sure the meters never exceed 0db unless for very short peaks (if you have a compressor/limiter downline from it) and you generally end up with a mix that is super clean, super quiet, and easy to produce.

I believe that, in times of old, op amps had a specific range where they worked their best, and may have accounted for running them hotter than the bare minimum (but never at peak), but modern designs seem exceptionally quiet at all but their highest settings nowadays, so why run hotter than you need?

If anyone can explain where this is incorrect, I'd love to hear it...

The thing with Bose's is, most mixer systems provide independent information whether you are overloading the channel input OR overloading the main output (or power amp clipping, in powered systems), but Bose just gives you the one, non-informative clip light. Some way of distinguishing whether you are clipping the power amp or just the input would be VERY handy, IMO.

I have the Tone Engine mixer and it does provide you the channel specific info on volume levels/clipping. With proper gain staging, it's almost impossible for me to overdrive the main amp, but I have seen either the keyboard or vocals channels clip.

I've noticed various 3rd party styles are ultra hot and clip routinely unless I back them off.

Vocals not so much. Typically if I'm sharing a mic with someone...I need to increase the volume substantially for them to be heard. There voices aren't as big as mine and their mic technique is usually poor.

If I adjust volume levels for them, and then forget to return them back down to where I need them, then holy hell, its loud, lol...



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Bill in Dayton

May I add an extra gotcha?

Running lots of EQ on a channel stage can also boost a signal so that it overloads the mixer bus even if the input itself is fine. At this point your ability to spot this depends on (a) whether there is an input overload LED and (b) whereabouts in the channel the overload circuit is monitoring.

Generally I'm reminded of a live PA engineer I once worked with whose basic premise was "run all the amps at max so you can leave everything else low"

100% agreed...

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Bill in Dayton