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Desirable features on a custom built small-gig keyboard amp?


Dgas

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There is a great deal of info & opinions on what makes a great custom-built guitar amp for various applications. What would be desirable features of a keyboard amp for small club gigs (<100 people)? I'm thinking mostly piano application but possibly organ & piano. Examples of parameters: How much power? Tube or transistor? Solid state or tube rectifiers? How many speakers & sizes; include high freq tweeters? Alnico or ceramic magnets? Stereo/mono; combo style or head w/cabs (gigging amp so portability is a big deal). Special EQ requirements? Anyone have thoughts/suggestions for a custom built small gig keyboard amp?
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Depends. To me the amp isn't that critical as long as I can hear it and the signal I send to the snake is clean. I have adequate EQ and effects on my boards and modules. In September I played through a couple of $250 Behringer powered speakers with a 12" speaker and horn and they sounded fine. Modern keyboards have improved their effects and EQ so much the only real reason for me to have an amp is because I never know how many monitor sends we will have. If I knew we would have 4 monitor sends at every gig then I wouldn't use an amp.

 

You want something clean with a lot of power. You want the power for the clean headroom. Not so you can crank the beegeebees out of it. I would NOT waste money having anything custom built but I'm a cheap *******.

 

You can see one of the Behringers on the floor. I usually use a pair of powered floor wedges. One on each side of me. It is simple and effective for what I need.

http://i3.photobucket.com/albums/y70/CEB2/DSCF0035.jpg

"It doesn't have to be difficult to be cool" - Mitch Towne

 

"A great musician can bring tears to your eyes!!!

So can a auto Mechanic." - Stokes Hunt

 

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:snax:

 

Why the hell can't you just BE NICE????? :evil:

 

 

Ahem.

 

To the O.P., a good keyboard amp is trying to be an average P.A. cabinet. Design a good P.A. cabinet with integrated amplification, and you've got yourself a better keyboard amp.

 

Of course, there have been a million such wheels invented before you brought this up, so I really fail to see any benefit to doing this yourself, other than the satisfaction of a job well done, but hey, whatever floats your boat.

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I agree with Sven - between the QSC, JBL, EV and others, there is no reason to do it yourself.

 

Ideally, I would want something:

 

* lightweight

* enough power to handle the dynamic range and transients without breaking up

* wide & linear frequency response

* adequate dispersion

* wedge-shaped for monitor, as well as upright positioning

* durable

 

The great thing about the name brands is that you can resell them, if needed. Everybody recognizes the JBL branding. Nobody knows the quality of a custom-made system, so if you had to sell it you won't have that manufacturer's reputation or any warranty that they offer.

 

You can compare various speakers side-by-side in the showroom. IMO, this is a mandatory step in the decision-making process. I just can't see buying a pair of speakers without listening to them and comparing them between others first.

 

Good luck.

 

Tom

 

 

 

"Music expresses that which cannot be put into words and that which cannot remain silent." - Victor Hugo
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I agree too: the ideal keyboard amp is a high quality powered PA cabinet. It needs to be flat and clean. The stuff most folks here use have levels around 125 to 130 dB SPL, measured at 1 meter. (Usually that's calculated from the SPL at 1 watt, 1 kHz, measured at 1m, and then adjusted for the actual power level.) That sounds really loud, but 1M is really close, and those damn guitarists ...

 

Something any amp (guitar or keyboard) should have but rarely does is a way to angle it, so it's pointed at your head rather than your knees, if it's on the floor. The stuff we tend to use is wedge shaped so we can use it like a floor monitor, or alternatively on end like a PA cabinet (often on poles). If you're thinking of a cabinet shaped like a guitar amp, it should have hinged support legs to tilt it back on. But I'd recommend against that shape since it would look odd mounted on a pole.

 

Many of us also like the kind that are convenient for stereo use: two inputs on one unit with controls there, line send to the other unit. That way, to turn them both up or down we don't have to fiddle behind both of them, often while playing.

 

In any case, it begs the question "why", since there are so many very good powered PA cabinets. I can't imagine anything custom being cost-competitive.

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With regards to reinventing the wheel...there ARE a good crop of powered speakers that work well. However, many are using a small mixer along with it. I suppose integrating such a mixer would be a nice addition - something with a switch on each channel for +4dbu/-10dbv to accomodate different keyboards, a DI for PRE EQ mix out, probably 4 channels or so, and as they mention, an output for a second speaker to run stereo.

Dan

 

Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth.

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Like most people on this thread, my needs are a flat, clean, powerful unit (i.e. a PA). There is a fun idea I'd like to explore someday though ...

 

I'd love to meet a speaker designer who would be interested in experimenting with speakers which can change the directions of horns/drivers, switch between drivers, and possibly house drivers in variable resonance chambers (i.e. definitely not flat) to emulate vocal and instrumental resonance characteristics. Sort of like a leslie but exploring some different approaches to the "speaker as instrument" concept. The mechanics would likely operate under midi/cv control to enable your typical control methods: lfos, envelopes and performance gestures.

 

 

 

 

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There are two tracks to keyboard amplification:

 

- clean full range hi fi, which you need for acoustic piano and general emulative synth sounds (go powered PA speaker or boutique 3 way bass cabs)

 

- colored maybe tube distorted for electric pianos and non-emulative synth sounds (go tube guitar amp)

 

Choose one or both depending on what sounds are most important.

 

 

Moe

---

"I keep wanting to like it's sound, but every demo seems to demonstrate that it has the earth-shaking punch and peerless sonics of the Roland Gaia. " - Tusker

http://www.hotrodmotm.com

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Thanks for the input so far....I should have specified that there is nearly no cost involved as I have loads & loads of parts; transformers, speakers of all sorts, all necessary hardware; & just plain like to build amps. It is cheaper for me to build one than buy one. So I'm left wondering what makes a good keyboard amp for small gigs (no big sound system to push the keys through so can't be just a monitor amp). I've used Fender Twins (too heavy); Fender Deluxe Reverbs (can't take the low end). Small MESAs (not bad..little crunchy)...boatloads of solid state guitar amps (usually the speakers are crappy). Haven't bought any keyboard amps yet (I'm a guitar player) but now need something that works better than what I have for keys. From what I hear from guitar amps, I think I need something with more frequency range...& flatter response as mentioned in previous posts. Maybe a 15" & a 10" speaker? A high piezo for high end like some bass amps have (or is that too shrill)? I am currently in the process of building a brownface Bassman style amp and maybe can turn that into a keyboard amp (tiltback legs on the cab like the old style fender piggybacks). Maybe put a JBL-15 & a single 10" speaker instead of 2 -12"? Other thoughts?
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Agree with all of the above - I use a JBL EON10 (G2) which is great, except it'd be better if it had a few more inputs.

 

I'd settle for a keyboard-optimised version of the Mackie SRM150 though if anyone made one - maybe a tad more powerful, but small and light and mountable on a mic stand.

 

Or a cheaper version of the Mark Bass stuff.

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OK, I think I have a better idea what you're asking.

 

You'll want 2-way or 3-way, for sure. You need good clean high power, so transistor is usually the way because tubes add too much weight.

 

Tell us what keyboards you plan to play through it. As mentioned above, most keyboards want clean power (for pianos and emulations). However, for a lot of keyboard sounds, a clean (compared to a guitar amp) but colored tube amp can be killer. (Rhodes, for example -- sounds great through a Fender Twin.)

 

Keyboards need the highs and the lows, as you've discovered. Thus 2-way at mininumum and 3-way for the dream.

 

I like 12" a woofer with horn tweeter. Yeah, the horn tweeter isn't musical perfection, but they cover a wider range and are efficient, and crisp. 15" is great for folks who are "kicking bass" (playing bass pedals on organ emulation) or bass synth parts, but IMHO the 15" woofer loses definition in the crucial midrange for many other sounds (especially piano). But, I don't kick bass. I let the bass player handle the bottom (though I often double his part with my left hand on piano, so it can't be weak bass.) 12" or 10" or better yet 2 10's or 2 8's ...

 

You also need to pick the dispersion angle carefully to match what you're doing. I use JBL 12" floor monitors (jrx112m) which have a wide dispersion, making them good for stage monitors. I also often play small clubs where I don't send to FOH, but the wide dispersion means the keys can get lost towards the back of the house. Narrower dispersion allows penetrating better, but makes location more critical and makes them less good as stage monitors. The best bet here is wide dispersion for monitors but send to FOH, and with small enough clubs the back of the venue is close enough to skip the FOH feed.

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If you are dying to build your own, go 3 way. It's the only way you will get good fidelity. Avoid piezo horns, they are all sizzle and no steak.

 

Use a close backed cab, correctly ported to give you all the low end that the enclosure is capable of.

 

I once built a 3 way JBL cabinet that I carried for years, with a 15" woofer, an 8" midrange, and a 1" compression driver w/ titanium diaphragm for highs. It was biamped, with the mids/highs further separated by a passive JBL crossover.

 

It kicked major butt. I currently use a stereo pair of Accugroove Tri 112s, which continues the 3 way speaker theme.

 

Here's a pic of it:

 

http://www.hotrodmotm.com/images/misc/mixx_rig.jpg

Moe

---

"I keep wanting to like it's sound, but every demo seems to demonstrate that it has the earth-shaking punch and peerless sonics of the Roland Gaia. " - Tusker

http://www.hotrodmotm.com

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I once built a 3 way JBL cabinet that I carried for years, with a 15" woofer, an 8" midrange, and a 1" compression driver w/ titanium diaphragm for highs.
That sounds like a great choice of drivers. Even a 6" or two 4" squawkers might be good, with that 15 to cover the bottom.

 

I bet that cab wasn't light, and adding an amp wouldn't make it any lighter.

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I bet that cab wasn't light, and adding an amp wouldn't make it any lighter.

 

Oh heavens no. The 15" was a JBL 2415, which was almost a 16" speaker. It had a massive cast basket - this was way before the days of neo magnets.

 

The horn driver was a 2475, which weight at least 10 lbs itself. It was massive overkill for just doing highs above 2 kHz, but then I was never able to blow it up either.

Moe

---

"I keep wanting to like it's sound, but every demo seems to demonstrate that it has the earth-shaking punch and peerless sonics of the Roland Gaia. " - Tusker

http://www.hotrodmotm.com

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With regards to reinventing the wheel...there ARE a good crop of powered speakers that work well. However, many are using a small mixer along with it. I suppose integrating such a mixer would be a nice addition - something with a switch on each channel for +4dbu/-10dbv to accomodate different keyboards, a DI for PRE EQ mix out, probably 4 channels or so, and as they mention, an output for a second speaker to run stereo.

 

http://www.proavmax.com/v/vspfiles/photos/YAM-STAGEPAS500-2T.jpghttp://www.dolphinmusic.co.uk/shop_image/uploads/Image/guitars/NEWS/stage1.jpg

 

Anything else? ;)

 

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With regards to reinventing the wheel...there ARE a good crop of powered speakers that work well. However, many are using a small mixer along with it. I suppose integrating such a mixer would be a nice addition - something with a switch on each channel for +4dbu/-10dbv to accomodate different keyboards, a DI for PRE EQ mix out, probably 4 channels or so, and as they mention, an output for a second speaker to run stereo.

 

http://www.proavmax.com/v/vspfiles/photos/YAM-STAGEPAS500-2T.jpghttp://www.dolphinmusic.co.uk/shop_image/uploads/Image/guitars/NEWS/stage1.jpg

 

Anything else? ;)

 

Agreed, but most of the reviews on this forum prefer the sound of QSC, JBL, and EV offerings. So seems to me, "ideal" would be be one of those offerings, but with the mixer section you show on the stage pas.

 

 

On a side note, I haven't tried it, but I've wondered if a waveguide would be better than a horn in a keyboard amp situation. Usually the sound is superior, but with a shorter throw and perhaps less efficiency. But I would think this would be good for monitoring.

Dan

 

Acoustic/Electric stringed instruments ranging from 4 to 230 strings, hammered, picked, fingered, slapped, and plucked. Analog and Digital Electronic instruments, reeds, and throat/mouth.

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"Flat, clean and powerfull" sound good to me.

 

Slightly traditional PA System setups probably would resonate right with me too, lots of good and harmonically varied sounds can be made with those. Of course making a small, light, transparent enough sounding PA speaker with *also* a lot of power isn't easy by any means, and certainly does not grow on the tree of IPL units and some random speaker parts, even though that's fun.

 

The hard to describe part apart from clean full range power is often the interesting part, because of modern synths having quite a range more of sound-shapes in them then guitarists are used to. The resonances and wave dispersions and how the speakers "push" (and pull) the air waves into existence make a lot of differences of which some are nice (and often loudness oriented) and more than a few will make the difference between the DIY speaker losing from lets say a wooden K12...

 

I know from practice that another side of the flat and un-colored "live sound" coin is that it isn't easy, even with advanced romplers and effects, to make that "golden live sound" which I too would almost take for granted on a decent PA system. Of course in some sense it is also more rewarding to go flat and neutral and being able to adjust the sound to spaces and synth sound needs.

 

The number of times (not that many, but varied) I've used my 5 way (dome tweeter above 8kHz, .., 15 inch 100 liter all damped (no bass reflex) under 40Hz) prototype speakers for live (inside and outside) sound I was still satisfied with the neutralness of the sound, but the 650 RMS or so driving the system probably would need to be used quite right to do in certain band constellations. The advantage of the neutralness are manyfold though. And very satisfactory. And probably not easy to achieve in a light small system. :)

 

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I'm different than most, I regularly gig without going through a PA, and do like a little color because I play mostly organ and feel powered speakers are a little cold for this, also I hate the idea of setting up a separate mixer on top of all the other things I have to deal with as a keyboard player with 2 boards, so what I want is a light, loud amp with numerous ins and separate EQ for each and tubes, like the K4, which I still use and am generally happy with, just make it about 20 lbs. lighter and I'd be very happy.
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