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Hi All,
I picked up a pair of EV Sentry IV-A's today. The Gefco woofers need new foam surrounds and the boxes are a bit rough. All of the speakers and drivers measure within spec for DCR. So I am hoping that refoaming, cleaning, working over the x-overs and fixing up the bass bins cosmetically will get them back into service.I plan to run them with SET amps, my DIY 300B's and/or BH Paramour 2a3's. Probably run them bi-wired.
There hasn't been much activity on AA since freddyi's foray several years back.
Anyone using, abusing or just futzing with the old Sentry's? Would love to hear your thoughts!
Cheers,
Geary
Edits: 03/27/13Follow Ups:
They are up and running. Still need some work. All of the Gefco 12" woofers now have new foam surrounds. There were three of one production, surround roll up and white glue globs for the leads in the cones. The "odd duck" had all of the same production codes on the back of the magnet strap, but the surround roll was down and the lead glue was clear.The horns didn't sound all that good on initial fire up...screechy! Replaced the old zip cords connecting the horns and the wire for the woofers with solid core silver plated copper/Teflon...more focused imaging and detail. I took the tweeter protection circuit out...better still. Then I replaced the x-over caps with Russian PIO; KBG 2uf,(tweeter), and MBM 30uf, (mid). The old caps were mylar and one of the 30uf was an electrolytic. Everything smoothed out, timbre was much better, imaging much more focused and a the sound lost a coarse, nasal quality.
So, the bass? Nope, doesn't get to the sub woofer realms, but placed in the corners of my room, (approximately 15'X 40'), the bass has much more impact than my Gallo Solo's, (Rogue Audio M150 Magnums or monoblock modded Golden Tube Audio SE40's) w/ SS powered subs, or my open baffle project, (GTA's or bi amped Bottlehead Paramours). (OB => Audio Nirvana cast 8 and Eminence Alpha 15). I am running 1 BH Paramour per side. Will try biamping, when I figure that out from the x-over schematic. (The phono jacks on the bass bin's were replaced with a 2 bladed connector, the x-over switch to biamp is actuated via a 1/4" jack.)
What I hear is marvelous. I really like the horns. I could probably live with the bass, but the bass bins are huge. As one can see in the pic, there is nowhere for additional subs! So,I am gonna indulge on my wife's tolerance and let the new parts in Sentry's burn in for awhile. Still need to work on mounts for the horns. Clean up seems to be never ending as every time I touch the speakers I find new nooks and crannies full of decades of dirt and dust.
Fun project....
Cheers,
Geary
Edits: 04/07/13 04/07/13 04/07/13
I had a pair in similar shape.
I went to Home Depot. The paint department sells a fast drying flat black, that made mine look almost new.
Get a quart of
RUSTOLEUM Paint
"Painter's Touch"
Premium Latex Paint
Flat Black
It maintained the dimpled finish and covers up the bare wood and any scratches that may be visible. Scratches that are black are harder to see when they are the same color as the rest of the cabinet. Wife appeal factor goes up alittle too.
Also, ensure the seal is complete around the cabinet back doors.
For a while I used mine horizontally with a Klipsch K402 horn on top.
Enjoy them.
Thanks Mike!
The paint made the new baffle repair virtually invisible!
Cheers,
Geary
Fyi, the tweeter mounting hardware was typically used to mount the tweeter below the mid horn (within the folded horn), not above it. This provides three advantages: smaller sound source, reduced possibility of physical damage to the tweeter, and the tweeter being closer to ear level in many situations (your's included).
Also, while the decision to remove the tweeter protection circuit is entirely up to you, it was there to reduce the possibility of excursion damage at high SPLs.
:)
Thanks! Yes, you are absolutely right. I moved them. Much better integration of the sound to get the tweeters lower.
When I got them, they were up and I had left them there out of laziness. I have to replace an upper brace in one of the bass bins and repair some composite damage to the mid-horns where the tweeter brackets mount. "They are loose again! S#!T!! Bring me some bigger screws!!" more than one too many times! ;-)
Hopefully I will be OK with the tweeter protection out. I am running them with 2A3 SET's, so about 3 watts. They really do sound better without the protection circuit.
Cheers,
Geary
I too have sentry IV and have been playing with them for many years trying to get them to sound the best they were capable of. I recently went to a high end audio expo and saw a Staccato horn system by Sadurni Acoustics ($40K) and had the wonderful opportunity to talk briefly with the designer himself. He said that one of the key aspects of getting good sound from horns is having the three horns time aligned. In general that would be approximately with the speaker diaphragms in line although he said that exact point may actually appear to be at a point further into the throat of the horn. He said moving the horns slightly might be necessary to find that perfect alignment point. When properly time aligned you will know. So I thought that would be something to try with the Sentrys. You have to then consider that the bottom is a folded horn. The actual horn length is longer than the physical depth of the box enclosure. So this would mean mounting the midrange horn at a position sort of behind the bass enclosure. I didn't see that as practical so I decided to resurrect an old Yamaha DSP that I had to act as a stereo delay for biamping the speakers. My home theater stereo drives the folded bottom and the delay and a small stereo amp drive the mid and tweeter using a stereo preamp feed and 1/4 inch plug into the Sentry crossover Biamp jack. I set the delay for approximately 3 msec then I physically took the tweeter on its bracket and mounted it above the mid horn back a bit so that it's diaphragm is in line with the mid horn diaphragm. Both the mid and tweeter are tilted down a bit toward the listeners level. To me, the result was significant. Imaging greatly improved and the greatest improvement is in transients like drums. Now the tweeter and midrange seem to blend into a single smooth sound source instead of a mid and tweeter. Took a bit to get the levels matched between amps but I really like the results.
COOL! - when seeing your mid-capacitor value that reminded me of an odd result I got with an 1823M on a SM120 horn with 29uF vs the same driver and cap on a 511 and Cobraflex - are you running 1st order on the midhorn? 2nd order may look fine. Best, Freddy
Karlson Evangelist
Based on the schematic, if I am reading correctly, and the actual crossover, the mid high pass is 2nd order => 30uf + 3mh, approximately 460Hz. The woofers are 1st order at about 250Hz.
I tried to trace the J1 bi-amp switch. Looks,to me, to be switched in by inserting a dummy 1/4"phono jack. This takes the woofers, out of the x-over circuit. To bi-amp one would need to provide an external crossover and amp for the woofers? The mid/high's would be driven from the stock crossover input?
Cheers,
Geary
I have attempted to reduce the x-over to eliminate the tweeter level switch,bi-amp jumper and the STR. Without the level switch the frequency versus power handling for the tweeter is 10w@15K. (See Curve 1 on chart)This layout can be strapped for single amp or bi-amped. I dropped the .6mH,(Not sure why it was there!) coil in the switch circuit and added a 3uF cap in the mids to maintain 2nd order roll off. These values are basically the stock values. When I model, the crossover points are more like 500Hz & 5K Hz, 2nd order Bessel. The spec's call out 400/3500 Hz.
I am definitely not real experienced playing around with x-overs. The plan is to replace the current x-over box in it's entirety and replace with the new crossovers,rather than hack up the stock units. Does it look reasonable? I would appreciate thoughts, suggestions and comments.
Cheers,
Geary
Edits: 04/14/13 04/14/13 04/14/13 04/15/13
Keele's paper illustrates "things"I believe the Gefco are a few dB less hot in the mids than the EV12L used in the paper's comparison so may be a bit more balanced.
you can probably have some fun - if your listening levels aren't real high then a modest powered sub would probably add enjoyment.
Karlson Evangelist
Edits: 03/30/13
Thanks freddyi! Interesting read at first pass. I will have to digest the comparisons. There is no argument about the inefficient use of space in the folded horn section versus vented.
I will probably run the S-IVA's as configured for awhile, after I refoam and work on the x-overs. There is a mention of vertical versus horizontal in the paper. That will be my first section of study. I was in the end process of finishing my 4Pi's when I happened upon the S-IVA's. It will be an interesting comparison given the paper's thesis.
Cheers,
Geary
The Sentry IV was more-or-less Electro-Voice's answer to the Altec A7. High efficiency, high output. Lacking in low bass, but really nice mid and upper range. We put a couple into a new high school auditorium back when they first came out (1974?). If I remember correctly, it uses the same midrange horn as the Sentry III, and it uses the same tweeter. The tweeter, btw, is basically the same as the T350 but with a different horn and a less pretty motor housing. Very nice tweeter, and very nice mid horn/driver.
You might want to consider keeping the mid, tweeter, and crossover, and building a better low end for it, kind of like what E-V did - known as the Sentry III - a very nice speaker.
hth
New bass bins are a strong likelihood. The Sentry III traded off efficiency for deeper bass and and a more furniture like form. I want to maintain the efficiency.
Once I get the 12" woofers rebuilt and the cabinets cleaned up, I plan to try placing them in the rooms corners, diagonally and horizontal. This should load the bass better and put the mid and tweeter closer to ear level from a sitting position.
I do have a old pair of passive subs that I can use to supplement the bottom end.
I am looking possible configurations for the bass bins. Any suggestions on a DIY'able plan that maintains the efficiency?
Cheers,
Geary
I have installed and have been tweaking new crossovers. So far I am liking the sound. I made the woofers' high pass second order. Cleaned up the mid transition with the steeper curve.
I tried the factory spec'd 2uf for the tweeter high pass. Lost much of the treble presence of my first crossover using 4750Hz/3uF cap. I went back to the 3uF. I think this is where I will leave the crossover for awhile.
I am going to play around with the 1uf cap paralleled with the 2uF caps for the mid and treble. I will then bypass the mid 30uf cap with small value film or PIO cap. (Thinking .22 or .33 uf).
Cheers,
Geary
I am loving my 45 tubes BottleHead Paramours!! Much of that love is due to the Sentry's! I am really pleased with the music that the Sentry's effortlessly put forth with the SET's flea power!
I am till tweaking mid range bypass caps on the 30uf caps. But other than fine tuning the tweeter crossover point, I am close!!
Now to cosmetics...
The bass bins are 5/8" ply, not 3/4", so I am probably losing some mid/upper bass impact and resolution. I will need to do some sanding and heavy fill, so may still lose more material in the bass bin walls. I think the walls need to be thicker and far less resonant.
To make them more "furniturish" I plan to sheath them in 1/2" BB on the upper and lower sides and back. The BB will be stained a dark black cherry.
The "front" of the folded horn, (the flat 12.5" high front middle), and the same area on the sides will be solid 3/4" cherry forming a "beltline" of hardwood. Not only will this, hopefully, look nice, but in combination with the BB ply substantially decrease the cabinet resonance.
I have sanded down the mid horns and repainted them a 2 stage automotive cherry metallic. Just seems proper that 60/70'ish horns would be Cherry Red Metallic! There IS a REASON that EV splatter textured these horns. OMG there was no end to bumps, dropouts, pin holes and other blemishes from the molding process. Satin Black over heavy texture makes them disappear. Sanding the texture off, well....Every blemish I sanded and or filled made three more stand out proud!!
Here are some pics of the horns...
those SM120's look hot in red - hey, would you know where I could get decent but cheap diaphragms for the Sentry IV tweeters? - the flanges are bent and busted in places on my tweeters too.
that little notch in the upper brace where the tweeter nestles is a flexy spot.
Karlson Evangelist
Simply Speakers, $19.95
http://www.simplyspeakers.com/ev-replacement-speaker-diaphragm-89486a.htmlShould be the same diaphragm as the T35 and Klipsch K77 tweeters.
Bob Crites has some comments:
http://www.critesspeakers.com/klipsch_tweeters.htmlYes, I like the red. Seems a better color for WAF, as well!!
Cheers,
Geary
Edits: 05/19/13
I have finished stripping the bass bins. Messy, time consuming and just plain NO FUN! Started with my belt sander. Not a chance. The EV textured finish gummed the belt almost instantly. Tried coarser belt, still not good. Had to drag out the 7" grinder and get sanding disks to fit. 80 grit and lots of changing disks, but worked. The factory coating was tough stuff!
I had to fill quite a few 1/4" and 3/8" holes in the sides. Must have been used to mount something(s)!? Dowels and glue, good to go!
The entire bass bin was stapled to assemble at the factory, mostly held up well except for the seams at the corners, (well all of the abuse occurs here!). I glued and screwed the entire perimeter. I still need to fill the the countersinks holes and a few gouges and then sand again. Nice improvement in the "knuckle knock" test. Everything is and sounds solid. I will pick up the BB ply and cherry stock and start prepping to convert from beasts to beauties!
I air blasted the sanding dust and blew out the folded horns. I cannot believe the amount of crap that came flying out of the bins. Hell, that's got to improve the bass just having clean soundways!!!
Cheers,
Geary
Edits: 07/07/13 07/07/13
Good box if you have a subwoofer, no bass otherwise.
Those are your EV boxes on the bottom, JBL 4560s on the top.
There has to be a story to that picture! What is it?
Dave
It's simple.......Those cabinets are too big and too heavy for what they do, and the landfill charges too much.
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