The Motion Sound KRB-3D

I think you all know by now how I feel about rotating speakers-they totally make my boat float! I am as equally impressed by the Motion Sound PRO 3-T which travels to ever gig that I play organ stuff on. Unfortunately, the high end of the PRO 3-T must be miked to hear it. Of course, then I need a Barbetta amp/speaker for the low rotor, accordions and piano sounds. Many times I wished for a package with a great rotaing speaker sound and a great keyboard sound for my other instruments. Motion Sound has read my mind.

The motion sound KRB-3D is a stand alone stereo keyboard amplifier with 2 high quality 10" co-axial full range bi-ampable speakers (100 watts each) and a PRO 3-T rotating horn (see the review-xxxx) with fixed mikes fed back into the amp. All this, plus two stereo inputs (one channel with an expander), 3 band EQ, and two rotating speaker inputs. Whew! Motion Sound manages to squeeze this into a 24" X 21"X 16" cabinet with a 120 degree angled front (looking rather like a Bose speaker on sterioids), but with the high quality speakers being 25 pounds a piece, the KRB-3D weighs in at 70 lbs. Luckily, they supplied two heavy duty resessed handles which help alot. Casters would have been nice, too! Considering that you would need a PRO 3-T , a stereo amplifier, two speakers and a mixer to match the features, the unit is quite reasonable at $1549. And, its all in one handy unit!


Those of you familiar with the PRO 3-T, will reconize some of the controls on the rotary chanel. The input goes into a 12AX7 tube preamp to a pre gain which can be raised for a gnarly sound before going to the post gain for overall input volume. This is fed into a actual rotating horn, miked and put back into the amplifier. The tone of the rotating sound is controlled by the Contour, adjustable from a mellow tone, modeled after a Leslie 147, to more of a high tech sound. The low rotor (a simulation) is also fed back into the amp and controllable by a volume and bass knob. A unit with two foot swithes is provided-one for fast/slow, the other for stop leslie. Thankfully, the company changed the wires of the foot pedal to a softer kind, not as easy to fray, like the one for my PRO 3-T did. Once again, I wish the foot pedal had a LED for the fast speed, like on the amplifer. Controls for the slow, fast, and acceleration for both the horn and low rotor are variable inside the unit on the pc board.

There are two channels for keyboards (right and left for each) that share a very usable 3 band eq. Input one has the addition of a stereo expander controllable by a knob and switch. This effect seemed to act diferently with various patches on the keyboard, some not having any effect at all (especially bass sounds), though with the right patch, it sounded as if my axe was coming from the corners of the room.

The rear controls are a nice surprise. Two additional line level inputs for a mixer are included. You could feasibly run the whole band through the KRB-3D! Another very nice feature is right and left balanced XLR outputs. No more searching for a working direct box at a small club! Also included is a dry rotary output for running the non-effected organ sound to a reverb then back into a channel (or the mixer inputs if they are availiable). Some trim pots for controlling the mikes on the horns reside in the rear as well.


I used the amp at a pub gig with The Mojo Monkeys, an original blues band, featuring members of the Dwight Yoakum group. I broke out my trusty Yamaha SK-20 for organ and synthy sounds and my accordion for the gumbo. In the past, one of my problems of this set up was when I brought my PRO 3-T and a Barbetta speaker/amp, I had only one input, that being the rotating speaker sound. I ended up running the accordion through the PRO 3-T with the speaker stopped, but the sound was definitely had less high end than I needed. If I wanted the full sound of the accordion, I had to bring a mixer. More stuff. With the KBR-3D, I plugged the SK-20 into one of the rotating inputs and the accordion into input 2 mono, took out a little mid (worked great), send one XLR line to the house guy (who was pleased at the subtraction of an extra mike for the horn) and played the show. Very little setup. I had the whole unit up about 2 feet at semi-ear level. It sounded even better than my PRO 3-T. The organ sounds were superb, the amp being a perfect match for the rotating horn, stereo tones filling my ears. I had tweaked the pre-gain a little more than half to give a slight distortion, turned the low rotor bass down a bit, but cranked the low rotor volume and post-gain volume. This is where I felt the amplifier was a little quiet. Maybe I am old-fashioned, but I might be more turned on by a 15 inch version of this unit. Of course, I realize this would make the amp even more heavy, and it is right on the weight limit as it is. Being a multi-instrumentalist, I found myself wishing for more inputs with separate EQ but I guess thats what a mixer is for. When I played the squeeze box, the sound was fantastic, but greatly diminished in volume if I stood up. Very directional amp. If I did another show with it, I would raise it even higher, directly at ear level and tweak until the volume was right.I think the logic is that if you are playing that loud, you will have a line out to the house for reinforcement. People in the house, including the sound guy, said the organ sounded better than ever, and I have to admit, it made me play up a few notches.

When I got home, I checked the unit out with a Kurzweil piano module in input one and two, and a organ sound in the rotary simultaneously. At higher volumes the sound began to distort, especially the high end, but an attenuation of the mid and high helped considerably. Low bass sounds seemed a little too much for it, but some EQ adjustment helped this. I also plugged an acoustic guitar into input two and cranked it. It sounded great, though the 3D effect did not make much of one. I also ran a Roland VK-1 through it and it was awesome, even with the keyboard rotating effect on (like a double leslie-the voice of God).

The KBR-3D seems to be made with people like me in mind. The rotating speaker sound is steller and the keyboard channels are very full range and pleasing sounding. The convience factor of an all-in one-unit, combined with the excellent sound quality make the unit a good bargain for the money. Sporting a road case supplied with castors, this amp could have a place at ever gig that I play.

1999 Gig Magazine
Reprinted with permission