My GF-777Z ** Project 2 OHM STABLE

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tshorba

tshorba

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Cpl-Chronic said:
Well, I did think of using a car amp with speaker level inputs. That way, I could run the original super-woofer wires to the amp's speaker level inputs & run the woofers from the amp giving me a good 20w per side or more, depending on how I set the input gain. Using speaker level inputs would avoid messy splicing into the pre-stage, present a higher impedance load to the original woofer amps & lower the load to the HA's.
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The issue with this design would be

Pre-amp > Amp (HA1392) > level conversion > woofer Amp(HA1392) > level conversion (high level input) > car amp,

This just amplifies any noise picked up through the stages of amplification and subsequent level conversion to the next amp


Cpl-Chronic said:
The down side to that plan is space. It's really tight in there already & any added amps would have to be attached externally to the back-panel.
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That is why I suggested a T-amp, very small size and thermally & energy efficient. T-amps are essentially a Class D with quicker switching. They are big in the DIY/mod community.
 
Cpl-Chronic

Cpl-Chronic

Member (SA)
tshorba said:
The issue with this design would be

Pre-amp > Amp (HA1392) > level conversion > woofer Amp(HA1392) > level conversion (high level input) > car amp,

This just amplifies any noise picked up through the stages of amplification and subsequent level conversion to the next amp
Click to expand...

Uh,,, I have to disagree. If the super-woofer amps are used as inputs to the new amp, the load presented is much higher & in return, the current demand is much lower, hence the signal from the HA 1392 is much cleaner, going into the added amp. The only real noise would be from the goofy attenuated signal to the second HA chip for the super woofers. The amount of noise added by a speaker level input to another amp would be minimal & offset by the gain in clean amp power & increased dynamic range. In the end it would sound cleaner, actually, having a better dynamic range for deep bass tracks. Also, if you use speaker level inouts, then you can still use the controls on the front to control the NEW Super-Woofer AMPS. Seamlessly. Finally, an added benefit is that the setup can be returned to original condition easily if the resulkt is less than satisfactory.

That's why I vote for speaker level inputs vs. hard soldered taps from the pre-stage.

Maybe I'm wrong for thinking that but I bet I could get a really good result by dialing in the right amount of gain off of the super-woofer wires.
 
Cpl-Chronic

Cpl-Chronic

Member (SA)
Superduper said:
Pretty sure I can blow them for you if you'll give me a day or two with it.
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1. Why would I do that? 2. How would you go about this astonishing feat? I'm guessing a square wave, maybe at half output, with lots of cooling & heating up in between to stress those internal junctions? Say going from near freezing to 90+ degree temps?

I bet you are just itching to try it too.. too bad you'll NEVER, EVER get the chance.... :thumbsdown:

Just curious, that's all & stay tuned..... :-D
 
Cpl-Chronic

Cpl-Chronic

Member (SA)
Well, 2 months later & still crankin' the BASS, LOUD & CLEAN & MEAN!!!!! 2.5 OHM BOSE woofers sound really balanced & thumpin' hard @ '0'(flat) & kickin' like a jack-hammer on everything from the stones, 'Slave' to Hashim, to Lunatics 'Midwest Swing'. Will post again in a few weeks to let you peeps know if its all good.

BAM!!!

Cheers, :-D
Cpl
 
Cpl-Chronic

Cpl-Chronic

Member (SA)
Here's my 2ND Gf-777Z Modded with the same 3.2 OHM outer woofers, a 2ND pair of BOSE/CADILLAC 2.5 OHM Super Woofers, identical to the last pair tested & FINISHED OFF WITH 2 JVC M70 TWEETERS for incredibly powerful & clean BASS & TREBLE....

Check it out:

https://www.youtube.com/watch?v=GSv_XP3Vy3Q

https://www.youtube.com/watch?v=qn0l1CiCvIM

I still have to sort out a couple of cabinet nosies & insulate it with Acousta-Fill to finish off the sound...

Cheers,
Cpl
 
bklyn sound

bklyn sound

Requiem Æternam
I have to say ....I give you a lot of credit for taking this baby to the edge...the time you put into one of these projects is fantastic...wish I could really hear this one in person but I do get the idea :thumbsup: :thumbsup:
 
Cpl-Chronic

Cpl-Chronic

Member (SA)
Heyya All, :-D
What's new?!?!?!

It's been ten months since starting this thread & I'm reporting back on the 2nd Triple7 modded with my BOSE 2.5 OHM super woofers & 3.2 OHM full range woofers.

The speakers installed are as follows
***************************************************************************
2 - 2 OHM BOSE SUBWOOFERS(Super Woofers)
2 - 3.2 OHM HIGH EFFICIENCY WOOFERS with cloth inverted surrounds & high efficiency cones(full range woofers)
2 - JVC M70 HORN TWEETER drivers(horn drivers)
STOCK AMP & FLAT RECORDING(no boost or cut)
****************************************************************************
It's important to note, I've done this to 2 separate 777's now & both handled the lower impedances with ease, proving that the 2 OHM stability the graph implied, could be relied upon as accurate.

I am happy to say all is well & bangin' out the BASSSS!!! So, after all this time, listening to some heavy hitting DUB & reggae, this is what those BOSE woofers sound like, up close:

LISTEN TO THIS IN YOUR CAR OR ON A KILLER STEREO!!!

!!WARNING!!! HEAVY BASS!!!*******************************************

https://www.youtube.com/watch?v=LIbmxurd-vs

https://www.youtube.com/watch?v=lZFOAPNQh8Y

*******************************************************************************
 
J

JLF

Member (SA)
Fantastic!

I love this thread, just read every word.

What I didnt like about my Triple 7, actually a GF-919; was the lack of bass. Id have shipped this to you for modification TODAY if I hadnt sold it off. I mean, my JVC M-70 pounded harder!
 
Cpl-Chronic

Cpl-Chronic

Member (SA)
JLF said:
Fantastic!

I love this thread, just read every word.

What I didnt like about my Triple 7, actually a GF-919; was the lack of bass. Id have shipped this to you for modification TODAY if I hadnt sold it off. I mean, my JVC M-70 pounded harder!
Click to expand...
Well, when I got my first GF-777Z, I wanted to cry. It sounded like a sick clock radio with the original speakers so I was on a quest to make this beast great & read a couple of restoration threads where enthusiasts were using car speakers for their 777's with good results. The BOSE woofers have a great blend of deep bass with a warm sound but not too boomy....

Cheers,
Cpl
 
Cpl-Chronic

Cpl-Chronic

Member (SA)
In a previous post I listed the speakers I used for the 2ND mod:

--
The speakers installed are as follows
***************************************************************************
2 - 2 OHM BOSE SUBWOOFERS(Super Woofers)
2 - 3.2 OHM HIGH EFFICIENCY WOOFERS with cloth inverted surrounds & high efficiency cones(full range woofers)
2 - JVC M70 horn tweeter drivers
STOCK AMP & FLAT RECORDING(no boost or cut)
****************************************************************************
--

What I forgot to mention is the JVC M70 Tweeters are in fact 8 OHMS impedance...

So, I am running 3.2 OHM woofers & 8 Ohm tweeters off of 2 AMP channels, essentially, & 2 more AMP channels are running the BOSE 2 ohm drivers as Super Woofers.


Cheers,
Cpl
 
k2j

k2j

Member (SA)
What do you do for speaker stabilization? I threw a replacement speaker in a junked out jvc 550 and the thing is rattling bad. Think I need to put something in between the speaker and the box maybe?
 
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