28 May 2018

Budget Boomers - Electro Voice Sentry

Let's see,
what do we have here...
More big speakers!!

For years now I'd been wanting to build speaker cabinets,
and fill them with good components.
Cause I don't have any other projects to do...
Sadly I've collected good components a few times,
Altec 416/515 woofers and horns,
but with no carpentry tools and the big pdx move,
let them slip away.
A chance craigslist perusal uncovered these gems.
At $100 a piece,
they solved the cabinet building issue,
while supplying decent mid-grade components,
supposedly from Electro Voice Sentry speakers.
Of course there were reasons for the budget price,
found after they were unloaded at home.
Each woofer had a little rip.
The packing tape repairs had fooled me.
The tears didn't cause any rattling or buzzing,
so a hack repair was in order.
Tissue paper and wood glue to the rescue!
Basically paper mache acting like a fiberglass repair,
They dried up stiff as the rest of the cone.
The gaping holes 
allowed me to check out the guts.
Electro Voice t-35 tweeters,
1823m midrange driver, 8hd horn,
and some big magnet 15" 8g? woofers,
all hooked up with custom crossovers.
The tuned port cabinets were well made with plywood.
Not show quality,
but perfect for the garage.
Definitely a score for the dough.
But the sound...
For shop speakers they were just ok.
Some tunes were mixed evenly,
others were grating.
The blaring mid-range was like a shotgun.
I resorted to putting cotton balls in the holes,
which softened the sound.
The builder had started to tune them
Each speaker had 2 knobs,
L-pads that control the two horn outputs,
but they weren't wired.
A quick solder hook up allowed easy experimentation,
uncovering the faults of the system.
Come to find out the EV 8HD horns
have design flaws from the get go,
throwing sound out like a cannon.
Maybe a pair of Altec 811b horns (top) could help.
I couldn't resist copycatting color cues from
old JBL 4345 monitors.
Ugly enough to be cool.
The first one went back together easy,
and the music was finally tamed.
The wild horn diffused the sound waves.
Definitely worth the effort.
The second one needed a new L-pad,
which took a week to arrive.
One was broken,
and both were glued in.
Which meant they disintegrated upon removal.
JB weld is some strong stuff...
Maybe a hammer and channel locks didn't help!
I really didn't want to wait another week.
Since the first speaker worked so well
without needing to move the tweeter knob,
the L-pad ohms were checked at the position used,
about midway,
about 5 ohms.
Luckily I had a stash of 4.7 ohm resistors.
Justifying why hoarders don't throw anything away!
A single measured at 5.8 ohms,
which maxed out the 20% variation
these were spec'd at.
Two in parallel measured at 3.7 ohms.
I'm sure there's a formula for this...
Two were wired up to the tweeter + wire.
One could be cut out if the sound was too bright.
Finally the set was complete!
Time for a late night cranking session..
More soon!