Late last year, B.I.C. introduced the Beam Box, a directable indoor FM antenna. Now we have the Boom Box courtesy of dbx, a company that is probably best known for its range expander and noise reduction units. The Boom Box is an entirely new area for them.

What does it do? Well, it pounds your chest a lot. You remember that feeling you get in your rib cage when you enter a live rock concert? Well, it's not the excitement of an imminent heart attack, but high intensity low frequency sound that's making you feel like your ribs have just shrunk a size and a half; but the items contained in your chest cavity have not quite caught up.

We have long assumed that part of that feeling was the general sound level at near-deafening force. That's probably only partly correct, according to dbx. The feeling of excitement is the result of extremely low frequencies at significant force. Those frequencies fall in the area between 25 and 50 Hz and are generally removed from arecording in the mastering process. They are also reasonably inaudible as sound or discreet tones.

Nonetheless, dbx and others believe that this inaudible sound produces a significant feeling, and it is that feeling the Boom Box attempts to recreate by synthesizing the missing area.

How come the editorial job on our records? There are several reasons. The first is simple cost cutting. Reproducing those frequencies at decent volume requires large grooves.' The wider the grooves, the less you can get on a disc. You would probably not want to buy a record that had less on it than you have come to expect.

The Boom Box is a seemingly simple device. Two knobs and an LED adorn its front panel with a push to bypass activate button. The large knob handles the synthesizing end of the process, while the smaller knob is a low frequency boost control which acts to fill in the area between the synthesized sound and the actual low end on your record.

Connections are made in the rear with cable going to the tape jacks. The Boom Box takes an incoming signal, senses a frequency of around 50 Hz and says to itself, "Hmm, this sound didn't just cut itself off at 50 Hz. It must exist, at least in overtones, at lower frequencies." And it creates them.

The large knob regulates the amount of synthesizing you get. Entertainingly, as soon as the circuit activates, you get a nice wink„from the LED. Once you get the synthesized low frequency, you have to start playing with the other knob to "fill in" the gap. Low frequencies from 50 to 100 Hz are pumped up and emphasized to give you a "smooth" curve.

What's the result of all this creation and restoration? A rather interesting effect. You really can give your listening area (and your respifatory system) the illusion of being in a large concert hall surrounded by thousands of watts of power and massive speakers with huge woofers. The damned thing works.

It requires a little while to make the adjustments properly and get the desired levels for optimum comfort and your taste, but it certainly does work. Your first temptation, at least mine, is to take the knobs and give them the maximum boost for maximum whomp. The result, to me, was disappointing. It was only after I backed both knobs off to around 10 to 12 o'clock positions that the effect became both apparent and pleasing.

The Boom Box, obviously, is intended for rock music and it does work incredibly well on the several records that form my standard test package. I, really felt a pulsating drum banging my chest (to say nothing of my tympanic membrane). But for the sake of argument and truculence, I thought I'd try the Boom Box out on a few classical discs, and then through a pair of not-so-great speakers.

I was surprised on both counts. The Boom Box came through again. I had to make some control readjustments, but suddenly, a cello sounded the way a cello does in a good concert hall (from good seats). There was a resonance and richness that gave me a sense of presence. ,

The other surprise came from the fact that I found I did not need great speakers to enjoy the Boom Box's benefits. Small speakers sounded full and even a set of car speakers sounded not too bad in my living room.

Dbx makes few scientific claims for the Boom Box. They do not say that it restores the original harmonics or even that it's accurate. They do say that they have made a series of assumptions and that the Boom Box is the result of those assumptions—that sound does not arbitrarily cut off, and that it's the missing low and subharmonic frequencies that give you the feeling of reality. The Boom Box makes good on dbx's claims.

Priced at $200, it is clearly an optional item rather than an audio necessity. But, just as obviously, the Boom Box is an addition many music fans will want to make to their stereo system.