Getting just enough
In the late 1970′s I began experimenting with planar loudspeakers: first with Magnepans and later with electrostatic loudspeakers – specifically the Acoustat 2+2 which happened to be tall enough to qualify as a line source. If you’ve never heard an electrostatic loudspeaker then you’ve missed out on an amazing experience – albeit one that is very limited – that of a window-like quality of “you are there” midrange.
We used to joke that with an electrostat you had to have your head held in a vise to enjoy the benefits – so narrow the sweet spot of these products. But when you were in the zone they could be rather amazing – so light is their diaphragm that their transient response is nearly instantaneous. They had other faults and benefits as well, chief amongst them was a lack of dynamic range and bass. It was to this latter quality I address this post.
After acquiring the 2+2 pair I quickly became unhappy with their limited dynamics and low end and was ready to sell them and move on when by chance I happened to be standing next to the panels when they were playing. I noticed that standing next to the speaker there seemed to be an enormous amount of bass present that apparently wasn’t being projected into the room. Instead, the flimsy wooden panels were themselves wobbling to the bass and hence little of that energy was being transferred into the room.
The solution seemed obvious: brace the panels so they didn’t move and the air in the room did instead. To do this I built a bracing system out of 2×4′s and screwed it into the panels – a good solution but ugly and much to the horror of my ever loving and forgiving wife Terri – as these were in the family living room. I lived with the improved results for some time but eventually hated the look of this contraption as well and dismantled it.
I decided it might be worth while to augment the bass instead – with a subwoofer – of which at the time there weren’t too many of any quality. I happened to have a low cost M&K sub hanging around and added this to the right side of the system – the right side being the correct side always when a single sub is chosen because of where the bass instruments reside in an orchestra.
I spent the day moving the sub around turning the volume up and down and could never quite get the thing to integrate with the panels – until at one point in my adjustments I nailed it. It integrated perfectly! True, in this setting there wasn’t much bass but dang if it didn’t integrate seamlessly with the panels.
It was when I went to the rear of the sub to write down the volume setting that I noticed I had actually set it to zero. No wonder it integrated so seamlessly.
I put the 2+2′s up for sale the next day.
Paul McGowan – PS Audio, Intl
In yesterday’s post we covered part 2 of the MultiWave story and how my experiments with higher frequencies feeding power to the connected equipment gave me breathtaking results in the top end and midrange, but lost midbass and bottom end at the same time. Truly, this was the quintessential double edged sword – but I wasn’t about to let it go.
Since I did not have an answer to the problem and wanted badly to get this new concept of regenerated power out into the world so high-end lovers could experience what I was hearing, we released the P300 Power Plant with the ability to raise the frequency as high as 120 Hz. We let folks know it would come at a penalty of lost bottom end, but on many systems this was actually a benefit as you could dial in what worked best 1Hz at a time – until you had perfection.
It took several years before the answer I was seeking could be figured out and it came from an unlikely source: a secret vault located somewhere near Chicago. In that vault worked one of our nation’s best minds, that of Douglas Goldberg. Doug, a scientist at Northrup Grumman doing God knows what to save our country, spends his day locked in a vault in a secret location. I don’t know what Doug does but if I found out you’d probably never hear from me again.
Doug’s a serious Audiophile and designed much of the original Audio Alchemy products back in the day. Over a beer at a CES I told Doug about my problem – how could I have the best of both worlds? I want the glory of the top end I got with powering the equipment at a higher frequency without sacrificing the bottom end. Could it be done? Doug pondered this for a moment and said “Yes, but I would have to run some computer simulations to figure it out.” We finished our beer and I figured that’d be the last of it.
A couple of months later Doug called me and said he’d done it. It was “simple” (everything’s simple when you’re smart).
“The simplest and most effective means would be to add in a little of the higher frequency while maintaining the lower frequency, and this could be done in several ways”. Doug explained. ”Combine two or more frequencies together with the lower fundamental and do it at the same time which will change the basic sine wave shape and extend the peak charging time. That’s one idea. You could also start with the basic wave then add a quicker one right in the middle of the first wave.”
The idea was, after being explained, simple. Instead of one wave it would use multiple waves – hence the name. The bass problem was solved by sticking with the fundamental 50Hz or 60Hz and then adding a little higher frequency to open up the top end and midrange. It was a brilliant solution and fortunately our engineering group had used a type of DSP to produce our sine wave and a simple programming change allowed us to try it and produce it.
Today’s MultiWave is actually the first suggestion Doug gave us. We add a little bit of 180Hz to the lower frequency which extends the peak charging time of the sine wave – and the rest is history.
Paul McGowan – PS Audio, Intl.