MySHARP GF-77Z DISCO DISTROYAH! New Compression Horn drivers & minor updates

Hey MOD freaks. As you know, I have the annoying habit of improving upon old Grail status blasters like this poor 777Z that was 90% clean but the tuner is bagged & there's a repaired crack in the side but it's only a small one & you won't notice it unless you look specifically for it....YaY Time to mod...

I've been running 4x BOSE 2 OHM 6.5" woofers on each of the 4 channels present on the 777. 2 Super-Woofer channels & 2 Full range channels pump out a total of 45w, exactly the same as the Original C-100F class blasters. The difference is both hitcahi chips each run stereo across 4 channels in the 777 while the coion bridges the 2 chips for a BTL(bridged) 22.5W per channel, across 2 channels....

For highs, the 777 has 2 JVC M70 Tweeters mated to the horns & did their job well for 3 years but I got my hands on some compression drivers from mitsubishi, 2 years ago & forgot I had them...DOH!!....looks like good quality 70's horn drivers to me @ 6-OHMS...Perfect....let's try them....I'll change the 6.8uF caps to a buttery 3.3uF set from an old M90 I converted with better woofers which needed more coverage in the midrange by the open faced 2.75" drivers...

As you can see, the drivers I plan to replace the M70 Tweeters with are the 2 pieces above. They are much smaller & purpose built for driving a compression horn through a traditional horn aperture or lens. They will be much cleaner sounding & much more efficient compared to the paper cone tweeters below, which came from a JVC RC-M70...

Here they are mated to the horn structure. Now that JB weld was used to seal the mated surfaces of the driver opening to the horn's throat, it acts like a true compression horn tweeter. A first for the GF-777, 909, 1000 series...no Piezo POS half-measures here...



This pic gives you an idea of the driver's total size next to a Bic lighter...


More to come....

Can't wait to see the end result!

After listening to the blaster with the new Compression drivers & 3.3uF filter, I still noticed a hole in the upper midrange but now it shifted lower so that the upper range of voice & guitar tracks seemed a bit muffled & muddy. I think it's because I choked it for 8000Hz(8KHz) @ 6-OHMS, when it should dip lower into the upper middle range, say down to 4Khz. There's plenty of treble present & I think if I open it up more with a 4.7uF filter, it'll sound good & strong. The Bass & Treble on the 777 can do the rest easily to give me a more balanced, fuller sound. We'll see...

Stay tuned for a 3.3uF & 4.7uF filter comparison on the new horn drivers. This sampling of filters is not a difinitive experiment, just a rough, side by side, sound off....


Cpl

Here's a good track for mid high testing & has a decent bass track for comparing tweeter performance using 3.3uF filters on new compression tweeter drivers fitted to the 777 horns...

Note in the video below, halfway through the track, the Saxophone solo sounds a bit muffled while the Treble is strong & balanced with the lower mid & bass tones....
https://www.youtube.com/watch?v=Fh-bEpmrC5M

Here's a pic of the horn driver fitted to the throat of the 777 horn with the factory lens(black plastic ring/collar assy).


Below, the opening of the new tweeter dome fits exactly inside the narrow opening of the throat, as if it were made for it...




They have a lot more high(10KHz+) presence but the 3.3uf(8Khz) filter chokes it too much in the upper mid-range(4-8Khz). I think 4.7uF filters will do better with a 5.6Khz roll-off point which will blend well, down to about 4Khz, where the woofers start to trail off...


Stay tuned...

Cpl

Ok, swapped out the new filters to 4.7uF & a roll-off point of about 5600Hz(5.6KHz) & the difference in sound is striking...listen for yourself. The saxaphone solo, guitars & voices now have presence in the center of the soundstage. With the 3.3uF caps, the same track sounded muffled & the sax & guitar seemed to be playing from a distance, behind the other tracks.

New 4.7uF filters
https://www.youtube.com/watch?v=OEvKBmwSnRY

Normal bias & EQ tapes sound very good...Cybotron brings back the cassette days of my high school parties...

https://www.youtube.com/watch?v=KvdGs6Tm19U

I also added bumper feet on the outer front corners so it sits very steady & protects the corners from dings.

Another HEAVY BASS track to really give you an idea of the power this beast cranks out(45w ** 11.25w RMS x 4 @ 10% THD)
https://www.youtube.com/watch?v=55dFYQ7QyZE&feature=youtu.be

Thats an intense build. As always, but still impressive. How much time did this take to do would you guess? I get overwhelmed just trying to imagine doing something like this.

trippy1313 said:

Thats an intense build. As always, but still impressive. How much time did this take to do would you guess? I get overwhelmed just trying to imagine doing something like this.

Click to expand...

It takes a heap of patience, determination & planning, planning, planning....I'd say I spend 2-3 hours of planning, prepping & designing these grails for every hour of actual execution & fabrication. These are all prototypes in my mind of what a blaster can be if it was cool again.

I wanted a 777Z - CONION - DISCO-LITE with lots of power, a super bright strobe light music system & lots of well placed bumper & crash bars to protect this working piece of art,....so I made one out of an almost dead 777 & lots of parts & things I wanted including 4 BOSE 2 OHM woofers to get the full 11+w per channel X 4 channels, which is the same output as the C-100F, not the 28w FF or Helix.....BOOOO_YEAHH!!

I think, over the years remaking this colossus, I spent probably 4-6 40 hour weeks on it as a project, including design, planning, scrounging, foraging & bartering etc.

It does resemble a NASA engineering project inside with the extra wiring but it's all fused at the original power source & you can remove the original chassis in 10 minutes with 2 extra 3-pin plugs to disconnect, vs a total stock unit...virtually the same serviceability as original. The big red LED meters at the center bottom are from a C-100 & fitted to the Super-Woofer outputs to give a visual representation of the power being sent to each 'Super-Woofer'(middle 2 woofers).

ooops..