I’m eager to the the SP-1 and SP-II manuals as well. There is a nice image of an SP-II on eba with the top off. I found this article – Broadcast-Equipment-Exchange-1980-07 DOT pdf
I especially like this section: (Quote from that article, July 1980 Radio World, Psychoacoustic Enhancement
by M.D. Heleniak
Direct text quote:
Since our firm caters to the broadcast and recording industries, we looked
into the psychoacoustic processors to
see what they had to offer. The unit we
found most favorable is made by a new
company from Michigan called EXR.
EXR’s products are the SP1 and EX2
exciters which are both dual channel
audio signal processors.
The EXR Company was born out of a recording studio in the 1970’s. Jim Cassily, president of EXR, was looking for a way to make standard analogue tape
recordings match the sonic qualities of
the esoteric direct -to -disk recordings. In
their R &D , Jim Cassily and partner, Jim
Lagerkvist, designed a circuit which
they felt vastly improved the clarity and
intelligibility of an analogue audio signal.
They dubbed their new invention the
sub -phase psychoacoustic enhancer,
which was later shortened to SP -1. The
original SP -1, home -brewed in a Bud
box, caught the attention of rock star
Pete Seeger during a recording session
at Cassily’s studio. Seeger and his sax Get the most from your AM signal…
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Circle 108 on Action -gram.
player, Alto Reed, talked Cassily and
Lagerkvist into making an SP -1 for
them and with that, production of the
EXR Exciter began.
The EXR Exciter is now used in
almost any audio application imaginable. Although no one (except its
makers) knows for certain how it works,
its sonic presence is sought after. For
instance, in PA applications, the giant
McCormick Place in Chicago purchased
an EXR for President Jimmy Carter’s
speech and now ùses it regularly. Disk
mastering labs and recording studios
use the EXR and recording groups
ranging from the Berlin Philharmonic
to Linda Ronstadt to Earth, Wind and
Fire won’t record without it. Broadcaster’s enthusiasm for the EXR is no
exception. The latest Burger King and
GM jingles were mixed through an EXR…

I can testify to the EXR SP1 actually being very much a net positive when used on SM58, EV676, e935, e945, etc. vocal mics. It’s single knob dials in the crisp intelligibility factor when singing softly either live or on recordings.

I used one, not as often as you and missed the kick drum idea, but I have one for sale now. Last time I used it, it worked although now many years ago. I may be able to test it to verify it still works but I am no longer in studio work. I believed when I used it, it did what I wanted it to, basically added some presence if used well.

Bud, I have 2 or 3 of these if you really need one. They also pop up on ebay periodically.

Musician for 50 years, Studio engineer since 1994, Degree in electronics. Bud’s comments are the more real world experience. I never disliked a piece of equipment because of its design per say, I always look at equipment for what it is, a TOOL, and how it sounds to ME. Been a president of a multi-million dollar gaming operation as well and my job was to manage directors and managers(people), not know every nuance of their expertise. Not that it doesn’t help! Bottom line, now I have to go check it(EXR) on a kick track to see what it does before I let it go. you never know. I once had a very well known music recording industry figure (published)tell me vintage Quad Eight channels sounded like a wet blanket draped over your speakers. He sold me 4 MM61 channels for $175.00 dollars apiece. After a proper recap and cleaning, they are arguably the best sounding preamps(and deal) I have ever heard including Neve, Electrodyne, Amek, or anything else. Everyone I know in the industry agrees with me. Point being, usefulness is in the ear of the listener. I never dreamt of trying the EXR II on Kick…my Bad! I’ll let you know…

“It was a multi pole high pass filter. When that output was added back to the full signal it created a comb filter effect. Initial impression was increased presence but very quickly people realized that there were parts of the spectrum missing.”

And he DOES know technical things, in the greatest detail. And he had the best engineers. So many, many classic hit records were recorded using or mastered using the Aphex Aural Exciter for decades & so few people know. Which is still selling after nearly 40 years.

The EXR is absolutely audio quackery, pure snake oil. Hardly surprising their admitted “not a tech person” ex-president (now interior designer) doesn’t even know how it works.

If you want to lose huge chunks of your music, use an EXR. Its not a serious piece of gear.