Yamaha DTXpress/DTXplorer/DTXtreme

Any of you have experience with either of the following keyboard amps:

Peavey KB4 (Single 15" w/horn.)
Peavey KB5 (2@ 10"/with horn)
Behringer KX1200 (3-way: 15"/5"/tweeter)

The Behringer is far & away the least expensive, and it is a three-
way system, which I like. Trouble is, I've heard that quality is 
iffy with this amp despite the fact it's German-built.

The Peavey KB5 is the most expensive, and the twin 10" speakers would 
give me 20" of total speaker area dedicated to low/mid frequencies. 
Five more than the 15" in the Peavey KB4.

All three amps have PA capability & multi-channels, so other signal 
sources can be managed through them, and they're all capable of 
acting as stage monitors when using e-drums live. Like I said 
though, the Behringer reputedly has quality problems. AND...I can't 
get ahold of one to demo whereas I CAN demo the Peaveys at a local 
shop.

If you guys have got some hours logged in with any of these amps I'd 
appreciate your input, or recommendations for other amps, for that 
matter.

Zilla

Zilla:
I believe the KB 4 is an updated version of the KB300, which is a 150 
watt, four channel amp with a 15" woofer, 5" mid range and tweeter. 
My keyboard player has on of these and I have used it on occassion. 
It's great for reproducing the full range of e-drums. 150 watts is 
fine for small venues, or to use as a monitor for larger venues. I 
bought the very similar Samson KB140 only because I couldn't find a 
deal on a used KB300.

Personally, I don't think the 2 10"s on the KB5 will be enough to 
give you the 'oomph' required for the low frequencies. My previous 
systems had 2 10"s (but only 80 watts) and the bass would overdrive 
even at very lo volumes.

Steph seems to have a lot of recent research, as well as in-depth 
knowledge, on the subject of sound reinforcement. Maybe she can give 
you a more technical explanation.

Stephen

> Steph seems to have a lot of recent research, as well as in-depth
> knowledge, on the subject of sound reinforcement. Maybe she can give
> you a more technical explanation.

Thanks, Stephen:

I used to install car stereos for fun, and because of my deafness, I had to 
resort to better-quality equipment in order for me to enjoy listening to 
music easily.  That meant making sure that I had amps with big enough power 
supplies to handle the load and electronics to control the speaker's 
movements accurately, placement of speakers in the car (wavelength matching 
as much as possible), "stiffening" caps for power level management, and a 
certain number of amp outputs to get a good, even sound across the frequency 
band in the car when it's loud.  This is how I come to know about this.

It's true that a number of small speakers can be used to reproduce lower 
frequencies they were not designed for, but it comes at a cost of being able 
to move that whole wavelength (20 Hz is about 18m long, 40 Hz about 9m long, 
and so on) very far.  Really, it takes a much larger cone to move larger and 
larger wavelengths.  However, the bigger the speaker, the more robust the 
electronics must be to control it accurately.  I've been wondering lately if 
it's possible to demolish a wooden building with a couple of 10-feet diameter 
speakers emitting a 7 Hz signal aimed at it.  It would probably have to be 
powered directly by the city's power grid...

Stephanie with nothing to do (not!  I'm about to practice)

>  Stephanie wrote: "I've been wondering lately if 
> it's possible to demolish a wooden building with a couple of 10-feet
> diameter 
> speakers emitting a 7 Hz signal aimed at it. "
> 
> Wow, a 10' diameter speaker, what an idea for all the home renovation
> shows....5 seconds of Back in Black from AC/DC...and the demolition
> portion of the show is done...then on to the new construction! ;)
> 
> OGD
 
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On Tue, 5 Aug 2003 12:30:38 -0500, Stephanie Ellison wrote:
>\ufffdI've been wondering lately if it's possible to demolish a wooden 
>\ufffdbuilding with a couple of 10-feet diameter speakers emitting a 7 Hz 
>\ufffdsignal aimed at it. \ufffdIt would probably have to be powered directly by 
>\ufffdthe city's power grid...

Do you remember the "amplifier instability" scene from the movie 'Back
to the Future'? ;-)

Matt

> Do you remember the "amplifier instability" scene from the movie 'Back
> to the Future'? ;-)

Nope - it's been so long since I've seen the movie.

Stephanie

On Tue, 5 Aug 2003 19:41:49 -0500, Stephanie Ellison wrote:
>\ufffd>\ufffdDo you remember the "amplifier instability" scene from the movie
>\ufffd'Back
>\ufffd>\ufffdto the Future'? ;-)
>\ufffd
>\ufffdNope - it's been so long since I've seen the movie.

Short synopsis: Michael J. Fox comes into Doc Brown's lab (which has a
massive power amp and aprox. 6' diameter speaker!) and plugs in his
guitar. A quick twist of the volume knob to maximum, a short pause and
he hits a power chord -- at which time the speaker blows out the front
of the cabinet, knocking MJF across the room and generally knocking
everything in the room over... funny scene.

BTW, I design high performance speakers as a hobby. I'm an electronics
consultant/EE doing mostly embedded controller design, but audio is my
first love. I wish I had more time to work on some new designs.

Matt

--- In DTXpress@yahoogroups.com, Matt Pobursky <ccsuser@m...> wrote:
> BTW, I design high performance speakers as a hobby. I'm an 
electronics
> consultant/EE doing mostly embedded controller design, but audio is 
my
> first love. I wish I had more time to work on some new designs.

Matt,

I'd love to talk audio sometime. As someone who's spent an inordinate 
amount of money on high-end audio equipment with nothing but 
unremitting glee, I salute you.

Ed

Stephanie
I took an excellent acoustics class in college (many moons ago) and the
professor told us about a student who did an experiment in a long tunnel
that joined a high-rise dorm to campus. He set up a guitar amp with a
frequency generator in the tunnel in an effort to find the tunnel's resonant
frequency. Well, he found it. Supposedly there were swaying vibrations all
the way to the top of the dorms and a squad of campus police arrived to end
the experiment. I have no idea what the frequency was that was arrived at-
but it takes very little energy to excite a column of air if the frequency
is correct.

-----Original Message-----
From: Stephanie Ellison [mailto:deafdrummer@...]
Sent: Tuesday, August 05, 2003 8:42 PM
To: DTXpress@yahoogroups.com
Subject: Re: [DTXpress] Re: Keyboard amps for electronic drums


> Do you remember the "amplifier instability" scene from the movie 'Back
> to the Future'? ;-)

Nope - it's been so long since I've seen the movie.

Stephanie


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On Wed, 6 Aug 2003 09:25:34 -0400, Creighton Higgins wrote:
>\ufffdHe set up a guitar amp with a frequency generator in the tunnel in an
>\ufffdeffort to find the tunnel's resonant frequency. Well, he found it.
>\ufffdSupposedly there were swaying vibrations all the way to the top of 
>\ufffdthe dorms and a squad of campus police arrived to end the experiment.
>\ufffdI have no idea what the frequency was that was arrived at-
>\ufffdbut it takes very little energy to excite a column of air if the 
>\ufffdfrequency is correct.

This is the theory behind vented enclosure loudspeakers. It's used to 
both control the excursion of the woofer cone and also augment the bass 
output by moving more air through the cabinet vent. You tune the box
volume and vent port to the speaker's low frequency cutoff you desire,
which limits the speaker's excursion.

It's also used in transmission line speaker design and the principle
behind how the Bose system you see all the infomercials about achieves
it's "amazing lifelike sound" from such a small enclosure and speaker
drivers.
hehehe...

Matt Pobursky