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Combined amplification system for bass, keyboards, and electronics

A

alobu

Feb 27, 2020
16
7
#1
Hey TB,

Hope this is the correct subforum. Soliciting advice: I gig on bass and keyboards and never have to compete with a loud drummer / band without FOH help, so I don't need anything insanely loud. For awhile I had a Roland keyboard amp, which I sold during quarantine; for bass I play a Little Mark III thru a 1x15 Markbass cab. That amount of power has fit my needs well for bass, but I don't have a lot of space and would prefer a single rig for both instruments (sometimes for use on the same gig), without compromising the sound of either. Additionally, I'd like to run some live audio processing / synthesis in Max MSP alongside the instruments. I'm imagining that the instruments would pass through an interface which would then plug into the amp. As long as the interface can monitor its inputs directly, the latency of the dry signal won't be an issue; with a good soundcard the AD/DA conversion can be done quickly too.

My keyboard sounds pretty bad through the bass rig, especially chords (which sound garbled). This seems not just to be an issue of missing high frequencies. Is this coloration likely the head or the cab? Similarly, the old keyboard amp felt thin and non-responsive compared to far less powerful bass amps. I'd use my interface as a preamp and monitor the signal to the keyboard amp, but it just didn't "snap." Would I have just needed a better preamp?

Anyone have experience or recommendations on a rig like this? I'm aware of the bass -> preamp -> power amp -> passive PA speaker paradigm. Any experience with using that system for several instruments? If so, what should I look for in a power amp / PA cab / bass preamp? Thanks!
 
#2
Depends on the speaker.
And how much EQ is used.

Just like bass guitar. At lower practice levels you can get away with the lows being pushed to much.
Start turning up the volume.
And the boosted lows can't be reproduced very well.

With keyboard your holding chords. Likewise the transients are massive.

A transient being any sudden change in volume or pitch.
Bass could be considered a single voice.
With keyboard it can be up to 10 voices all changing in octaves or holding multiple octaves.

My biggest problem with bass cabs as keyboard amps. Was the tweeter.
Bass hardly makes much highs for the tweeter. My keyboards would murder the pretty simple low cost tweeters in a bass amp.

I moved to typical 2 way 1x12 or 1x15 PA cabinets. With horn and woofer. Even then the tweeters really couldn't keep up.
I finally got a better sound with much much larger PA speakers or towers. It would have 2x15 for the bottom. And the horn was a much larger horn. Meaning it was crossed over lower for better mids and highs.

Most smaller PA speakers cross over the horn around 3000 hz or 5000hz so they can get away with a smaller horn.

You get more clarity in the upper mids if the horn is crossed over to 1800 hz or even lower at 800hz.

Problem is this requires a much larger horn to reproduce frequencies that low. So the physical size of the cabinet has to be bigger.
To have the larger horn

Otherwise for mid-range clarity you need a 3 way PA system. Which will have big 12" or 15" speakers for the low-end. And then use a dedicated 5" or 6" speaker for the mids.

Since the mids offer good lower mid-range and better extension to highs. Then you can get away with a smaller horn for highs.

Most Budget or mid budget PA speakers don't have 6" mids. You had to buy more expensive speakers from JBL to get a good 3 way system.

But a keyboard pumps out alot bass also.
But it's not single notes like a bass. It can be multiple voices at once. Eventually it's just like bass. Too get good clarity at medium to high volume levels. You simply need more speaker area. 2x12 or 2x15 minimum for bass or low-end. Since I was running a stereo tower pair. I'm basically getting good keyboard tone with a 4x15 and 2 large horns.
 
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#3
Yeah, get the upper mids into more speaker than horn. That is a huge piece of the keyboard voice dont muddle them up with the woofer or squish them through a horn. A three-way with decent surface area in the middle IMO for keys if you need it loud. Lower volume two way is ok but like above still need to watch that horn.

I think also seeking cabs like FRFR may be a safer keys route unless you need thunder from the keys. Bass cabs can be boomy or scooped, by design, when used for an instrument they arent designed for. Some bass cabs do better than others for keys. IIRC Fearful/less and AK are good for that.
 
#8
alobu said:
Beside price – and labor required – what differentiates that Fearful cab from a full range passive speaker (e.g. PA)?
Click to expand...

Most "full range" PA speakers are designed with a separate subwoofer as part of the equation, whereas the fEArful cabs use more or less subwoofer class low frequency drivers.
 
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#9
Your keyboard is probably outputting line level, while your bass is clearly instrument level. You may need an impedence converter to clean up the keyboard sound if you're plugging it into an instrument level input.

I'd reccomend a fEARful 12/6/1 or 15/6/1, or fEARless F112 as far as speaker cab goes.
 

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