The 'sleeper' box that killed Conion the barbarion..maybe...

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Cpl-Chronic

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May 14, 2012
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Heyya all. =)

This is kind of a long post so I apologize if you already know about coupling:

I'm all geeked over my first super-blaster. The GF-777Z. I've realized 1 thing about this blaster that no-one seems to touch upon. It's glory is unrealized in its original form. The 4 woofer, 4 amp design has real advantages over the more traditional large 2 woofer approach & takes advantage of the the acoustic law of driver coupling. For every watt of power applied, 2 identical drivers add a 3db boost in SPL over a single driver.

For example, 2 woofers @ 15w each will be 3db louder than 1 woofer @ 30w. Now, remember that doubling the amlifier power of any speaker only yeilds a 3db increase in SPL. Therefore, 2 woofers have the SAME SPL as doubling the amp output on a single woofer. A 10db increase in acoustic output roughly corresponds to a doubling of 'volume' to the listener, on average & requries 8 times the amplifier power. If you use 4 woofers, the acoustical power output is 6db higher, over a single woofer, for every watt of amplifier power.

Now, all 4 woofers in the GF-777Z are simple paper cones with treated & untreated edges & a 4w rating. Add to that, 4 amps that EACH put out 8w RMS into a 4 ohm load @ probably 0.5% THD rating. Peak to peak which is probably what the '8w max.' speaker rating is. If I'm wrong feel free to post here & let me know where my guess is off.

Well, I figured, if I find some good, high efficiency woofers, with a high SPL rating, I might make this thing into a high-octane performer. I know the crap speakers are holding this thing back but the right set of fast accurate woofers would bring this thing into its own. What do you think?

Crazy or Crafty?
 

THAFUZZ

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May 5, 2009
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Cpl-Chronic said:
Heyya all. =)

This is kind of a long post so I apologize if you already know about coupling:

I'm all geeked over my first super-blaster. The GF-777Z. I've realized 1 thing about this blaster that no-one seems to touch upon. It's glory is unrealized in its original form. The 4 woofer, 4 amp design has real advantages over the more traditional large 2 woofer approach & takes advantage of the the acoustic law of driver coupling. For every watt of power applied, 2 identical drivers add a 3db boost in SPL over a single driver.

For example, 2 woofers @ 15w each will be 3db louder than 1 woofer @ 30w. Now, remember that doubling the amlifier power of any speaker only yeilds a 3db increase in SPL. Therefore, 2 woofers have the SAME SPL as doubling the amp output on a single woofer. A 10db increase in acoustic output roughly corresponds to a doubling of 'volume' to the listener, on average & requries 8 times the amplifier power. If you use 4 woofers, the acoustical power output is 6db higher, over a single woofer, for every watt of amplifier power.

Now, all 4 woofers in the GF-777Z are simple paper cones with treated & untreated edges & a 4w rating. Add to that, 4 amps that EACH put out 8w RMS into a 4 ohm load @ probably 0.5% THD rating. Peak to peak which is probably what the '8w max.' speaker rating is. If I'm wrong feel free to post here & let me know where my guess is off.

Well, I figured, if I find some good, high efficiency woofers, with a high SPL rating, I might make this thing into a high-octane performer. I know the crap speakers are holding this thing back but the right set of fast accurate woofers would bring this thing into its own. What do you think?

Crazy or Crafty?
That all sounds Greek to me :dunce: :blush: But it sounded convincing. "I'll buy that for a dollar" :lol:
 

JustCruisin

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Jan 28, 2012
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My hair blew back on that one, it went over my head that fast! :w00t:

Yeah, they say if you replace the speakers with different ones.. you get a whole greater sound! I don't have one yet... :sadno:
 

Jboogie2384

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Sep 30, 2010
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:agree: with Cpl. I swapped mine out and it pounds like all hell broke lose. The original speakers do hold it back from its full potential. Save the old speakers tho. Some old folks like originality so if you plan on selling the 777z down the line then keep them or sell them to somebody in need of the originals.
 

Cpl-Chronic

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May 14, 2012
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I guess what I'm trying to say in more simplified terms is:

The GF-777Z isn't the most collectible box since chinamen are selling off warehouse warranty returns, all over the place & 24/7. Still, I've yet to see a 4-amp 4 woofer design rated @ 8 watts RMS @ 4-ohms into each channel, probably @ 0.5-1% THD rating. I bet the amps will take 2 ohm dips all day long just to be safe. No other blaster has that & only a good set of skins will do it justice. Once you mate some good quality, high SPL woofers that are speedy, maybe 55Hz Fs you can get the most out of it. Good quality foam surround audiophile drivers might work if the sealed enclosure requirements is small enough. I bet that once I get a speaker set to work out in the triple-7-ZEEE, I'll blast every conion I see....He-HEEEE! Cough!

I ordered 4 foam surround woofers that have an Fs(-3db) of 58-Hz & I'm excited because I got these little speakers with Infinity cone tweeeters, about 3 years ago & the tweeters are a more modern sealed cone tweeter that is a little bit bigger & I bet it's more efficient too because its some sort of butyl or polypropylene type substance, instaed of tired old paper. I've got High hopes it matches my needs. It's got a slightly larger dome dust-cap & tightly fits the plastic housing so that the dome is centered perfectly in the plastic aperture or 'opening'. I bet I'll either love it or hate it.

I bought 2 soudnstream basic 2-way 12-db crossovers for a car rated at 3000Hz with both 4 ohm woofer/tweeter combinations. The old tweeteres already sound unbalanced & muted with the crossover because the woofers & tweeters no longer overlap. This means the tweeters were always weak but sounded good with the crappy woofers & added that little bit of sizzle but no real clear upper mids. Hopefully the infinity car 'cone type' tweeters will fill in the gap more smoothly. *fingers crossed*.

I'll post some pics & move it over to the 'MODS' section if appropriate...
 

jimmyjimmy19702010

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I think a lot of older boomboxes would benefit with a new speaker upgrade. It would only be of benefit though if the replacements were more efficient than the originals and of similar or superior quality. Finding and correctly matching the output characteristics of the new subs, woofers and tweeters would be the trick.

James.... :-)
 

Cpl-Chronic

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May 14, 2012
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You are correct sir-JimmyJimmy. It will take a couple of educated guesses & tweaking the drivers to the x-over. I plan to go through maybe 6-8 woofers, tops, if my guess is off. I've deadened the box with dead-mat sheets & plan some modest insulating too. I even wrapped deadmat around the horns to dampen them with weight so that they don't rattle as much from the woofers. Now, I have to match the lows & highs with the slope of the x-over & maintain a 4-ohm load. Once that is acomplished, I'll play with the inner woofers until it reinforces the bass in a more natural way, so to speak.

It'll be either 4 woofers all across @ 4-ohm & 58Hz Fs, using foam surrounds & high SPL or only 2 in the outer positions while the inner woofers are a more traditional small sealed sub-woofer driver. I bet the 4 mid-bass high efficiency dirvers will sound better & louder too.
 

Fatdog

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May 3, 2009
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As much as I love my GF-777, I've always been disappointed with the sound in the Treble department. I never really expected big bass - even from the Super Woofers - simply because of the thin case and limited throw of the woofers. However, I do believe the speakers are holding back this beast. I upgraded my JVC PC-55 with Diamond Audio component speakers and doing so made a world of difference in sound - for the better. I guess I'm just too chicken to mess with my sentimental friend.

Definitely keep us updated, Chronic. :yes:
 

Cpl-Chronic

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It's funny you should mention that Fatdog, & I feel the same. The horns have so much potential & mids are nice & clear. The problem is anemic woofers & tinny paper cone tech. The original BASS woofers are nice & punchy in a guitar amp kind of way but low end is gone. I picked some average 6.5" home speaker sub-woofers that had a nice trade-off between sensitivity & low frequency handling. Next, I needed to rig a tweeter that would fit the horn adequately & boost the treble response. I looked around in my basement & low down in a box underneath my bench was 2 little speaker cabinets that sounded like puke but the tweeters sounded good & natural. As it turns out the tweeters are a perfect fit & are more natural sounding, efficient & can handle more power too. Oh, & they are 4-OHM Infinity car audio tweeters from the late 80's when they were still using cone tweeters & a 6-db single cap x-over. PERFECT!!!

The donor speakers.




They were 30 bucks online & the tweeters were the only good part anyway. It's a cone tweeter with roughly the same characteristics as the old paper cone but it has a larger magnet & the suspension is some sort of polymer, almost like rubber. They are more natural sounding & the denter cap of the tweeters fits the horns like a glove. I'll have more pics soon:


Infinity Tweeter from donors compared to original SHARP Tweeter





19-BASS-Wooofer replacements 4-OHM



Specifications:

*Power handling: 80 watts RMS/160 watts max

*VCdia: 1-1/2"
*Le: 1.61 mH
*Impedance: 4 ohms
*Re: 3.25 ohms
*Frequency response: 35-2,000 Hz
*Fs: 38 Hz
*SPL: 83.5 dB 1W/1m
*Vas: 0.55 cu. ft.
*Qms: 6.74
*Qes: 0.64
*Qts: 0.59
*Xmax: 4.5 mm
Dimensions:
Outside diameter: 6-1/2",
Cutout diameter: 5-3/4"
Depth: 3


The front of the woofers. loaded into the GF-triple7-ZEEEE...*tear*...*sniffle*

 

Cpl-Chronic

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:breakdance: Well, so far am pleased with the sound. It's close to balanced. I'm using the original inner super woofers as the outer speakers & they work quite well witht he new horn tweeters. Upper mids are still a bit muted but that should smooth out with the ESS 6.5's I ordered. I'm hoping the new outer woofers will make the mids a little clearer & warmer while boosting the 40-80Hz band...which is perfect for kick-drums & bass guitars. Plus, a light woofer with a foam surround is what I need for the rich mids to mate with the horn. Reggae sounds awesome so far & even rock & roll isn't tinny anymore.

MOre pics soon:
 

Cpl-Chronic

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Thanx goodman! :-D Keeping the horns was an improtant goal as horn laoded tweeters are 5 times more efficient than a naked dome or cone tweeter & the sharp GF horns are a decent design. The new sub-woofers were not very expensive but are decent quality & roll off at 40hz in a small sealed box(0.16 cu feet). They really 'pound' & the box rattles my bookshelf now. :afro:
 

Gluecifer

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May 6, 2009
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Great work, Cpl Chronic!

Do you have a link of where we can buy those speakers from that you replaced the Super Woofers with??
I'm VERY tempted to do it to mine too, as my side speakers have already been replaced.



Rock On.
 

Gluecifer

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Marvellous! Thanks a lot.

Be sure to get some Dyna-Mat or something similar to deaden the box rattles, thats one thing I discovered as soon as I replaced my side speakers; everything started to vibrate like a melonfarmer.



Rock On.
 

Cpl-Chronic

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May 14, 2012
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Gluecifer said:
Be sure to get some Dyna-Mat or something similar to deaden the box rattles, thats one thing I discovered as soon as I replaced my side speakers; everything started to vibrate like a melonfarmer.
Heyya, yeah already applied some dead-mat I had to the sides & woofer area. Still getting some rattles in the top of the box but I'm working on it & my outer woofers should get here next week but I'll be on vacation so It'll have to wait until I get back. :thumbsup:
 

Cpl-Chronic

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In the meantime, here's some more shots of the present modifications:

Here's a comparison of the original tweeter vs the new infinity tweeter. Both pics show the 2 drivers loaded into the plastic lens of the horn.

Original-Tweeter-Loaded




New Tweeter in PLASTIC Horn aperture




Notice the flat spot in the plastic opening to shape the coverage area of the horn. As you can see, the new tweeter dome actually makes better use of the aperture's size. The original dome is s=maller & leaves a larger gap for reflections.

As you can see from the pic below, the middle speaker is the original tweeter & has a much smaller magnet & voice-coil than the replacement infinity:

tiny-tweet-in-the-middle




The next photo shows the new tweeter insatlled:

 
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