My GF-777Z ** Project PHAT-AZZZ BASS!!

[Cpl-Chronic]

BAM!!!! Check this out!!!

http://lenardaudio.com/education/12_amps_4.html

So, super, if I get it right, you're saying that if the volume is even 25% or higher, my transistors are cooking with a sealed back & possibly a 2-ohm load on the BASS notes? I understand your view here & this information does back your assertion over my un-educated guess for sure but looking at the wattages & comapring them to the masive heatsinks, I think they really did over-engineer the thing against abuse because they had to & I bet they are engineered to dip down to the 1.5-2-OHM mark on the low notes, before straining. We'll have to see. I swear, I will pronounce the death of my GF & warn others against my fate if things go horribly wrong. I am all about the knowledge & F7%K the haters along the way. :judge: *fingers crossed*

As I said, I don't see any signs of transistor fatigue. If they were heating up too much, I'd be able to tell when it clips alot earlier or the highs would get a little bit muted & hazy. As heat builds, output fades while noise multiplies. It's as simple as that, really. You just need to listen closely to tell sometimes. I really don't hear that at all, even outside in 90+F days of summer, in the great lakes region. I really think it'll be OK in the end.

Can't you remember as a kid when you cranked it to 8 & damn the distortion? They don't burn out unless they suck....plain & simple...

 

[tshorba]

It is quite clear by this the THD spec is 10% and the output is 6.8W @15V and 4.3W @ 12V. Your assumed 1% THD is available at 0.5W. Reading the spec sheet the amp can dip to a minimum impedance handling of 2ohm (9W output) I would not be surprised if your "subs" dip below 2ohm when reproducing 20Hz

Source is Hitachi's own datasheet, was very easy to find this datasheet.

By the way, we are not haters and if you were really "all about the knowledge" you might listen to others. We are actually trying to help you by righting assumptions you have made by reading various web pages. Again nobody has criticized the sound of your box, we have only given ideas on what we believe are incorrect assumptions and other possible design flaws that might present problems in the future. I have never said the "horns" don't work but I have said it is a very flawed design and implementation by Sharp

 

[floyd]

it's plastic there's only so much you can do with it , even mr spock can't change that

just be happy with what you got and if you don't like constructive criticism then you might be in the wrong place , it's like being a stand up comedian and insulting the audience you might end up smelling like rotten tomatoes .


your box and mods are cool but this ain't a science fair and we will prolly never see it in real life so basically the **** only exist for you.

only reason i'm saying this is because i don't like seeing my pals get smart ass responses by a newbie .

if you don't like opinions don't don't ask for them or put yourself in a position to be called out on details of the project .
i have modded plenty of 777's and never felt the need for techno babble if you gonna do all that stuff to it might as well build a new box to house the electronics instead of re inventing the 777.
if don't like me i don't care ,i love to argue but i have nothing against you just saying what needs to be said .\

bring it on man i ain't scared

 

[Reli]

I still have yet to see ANY audio equipment user manual, including ghettoblasters, rated @ 10% THD

I don't have a TON of boombox manuals, maybe 20-30, but of those, half of them don't even list a THD figure.............. and the other half say 10% THD. I really doubt you'll ever find one saying 1% THD. If they did, it would reduce the wattage and make it look weaker in the minds of consumers.

 

[Reli]

You're missing my primary point about the horn's lens. The wasted frequencies, used up in refraction, are in fact the general region that is strong in a cone tweeter & drowns out the highs emanating from the dome of the tweeter, anyway. Why not trap only the energy from the dome of the tweeter & boost its acoustic output, using a horn with a decent, if not perfect, dispersal pattern. Frequencies of about 1Khz-2Khz are the most efficient for a cone tweeter & that's why they SUCK!!! I think the GF uses a crude but efffective solution to dampen the mids & even out the overall output of the horn, by only using the FLAT response of the dome region of the tweeter & boosting its output accoustically, using a smaller but somewaht accurate horn aperture. Yes, you get noise from the lens. Yes, it isn't perfect, by any means, but the RESULT really is a much cleaner, more accurate & louder sound than the naked tweeters. So, no I disagree & you simply have to hear this for yourself, I guess to ever settle the debate. Again, I ahve no ego involved & insults liek that jsut cloud the subject instaed of inviting collaboration between opposing views. What SHARP did was make a case that maxximized that shitty paper cone tweeter woofer noise thgt was 'IT' back then & then USED the crappiest speakers ever made to totally sabotage their dominance & give it up to the JVC's & the CONION's. That's the real problem with the GF & maybe 12w/ch woulda, coulda, shoulda, yada-yada....

Since there is no way to mount the 777's tweeters directly on the case, how could you possibly compare the sound quality, with and without horns? Sounds like just more speculation.

 

[Cpl-Chronic]

As lomg as you guys keep the debatge about hte knowledge, I'm fine & can take criticism, if it's constructive & informative. If you start calling into question my pride & call me defensive because I debate a subject & question the validity of statements, remember this:

Even if you KNOW you are right, I don't & won't agree with everything everyone says until I see some proof. Until then, it's jsut another statement to the contrayry. You have to back it up with some sort of reference. To tell me it's a waste of time proving your point to me is a waste of my time & don't bother me with pointless accusations about my character or whether I can take criticizm or not.

Again, you may be more knowledgable about amps & circuit design but I do know a thing or 2 about loudspeakers & have built cabinets for a living for stage equipment. Amplifier IC's may be rated at 10% THD but audio equipment HAS NEVER been rated at these noise levels. The signal would be simply unusable at those noise levels. ALL of you have to admit, it's a goody way to rate amp circuits compared to audio equipment & I ahve yet to see a 10% THD rating in any opwners manual, PERIOD!! As for the plastic case. Of course, it's plastic but the staggered woofer placement gives the plastic more rigidity & reduces large panel vibrations & may POSSIBLY address an alignment issue too since the 'Super-Woofer' amps are cascade fed by the outer amps. I don't know for sure but it seems plausible.

 

[Reli]

Ask yourself: Why would the average boombox buyer care about low distortion? I bet 99% of them didn't even know what that means!

Here are some examples of 10% THD, straight from the owners manual:

JVC RC-550:

Aiwa CS-880:

Crown CSC-980:

Sony CFS-77:

 

[Cpl-Chronic]

Ask yourself: Why would the average boombox buyer care about low distortion? I bet 99% of them didn't even know what that means!

Here are some examples of 10% THD, straight from the owners manual:

JVC RC-550:

[ Image ]


Aiwa CS-880:

[ Image ]


Crown CSC-980:


[ Image ]


Sony CFS-77:


[ Image ]

OK...point scored for Reli & SuoerDuper & as I said, these specs are new to me & I wanted to see some specs to back it up since all I've ever dealt with is manuals for stage & home audio equipment so 10% THD is un-usable in my world & unacceptable in those settings. As far as the difference in sound between the naked tweeters & the horns, I can tell a BIG difference in sonic properties & I've read tons of material about loudspeaker design & without question, even poorly designed horns will perforn better than naked or flush mounted tweeters & are WAY more efficient. What you guys are failing to grasp is the energy from the dustcap of the cone tweeter is more flat through the higher octaves, say above 3Khz & the horn is purposefully using that flat response & acoustically amplifying it with a horn waveguide. This shapes the output, has better transient response & my ears can tell that the overall output is cleaner & not jsut slightly. Also, the sound carries farthur too without distortion. Even the JVC M70 uses a shallow horn opening of sorts to boost highs slightly. You may know electronics more but I KNOW horns & theory applies here too, even if it is a hybrid lens that has mroe refraction than a properly designed compression hon.

A proper compression driver is really jsut a dome or dustcap on a coil without the cone part of the tweeter. That's really the only general difference between these horns & a professional horn. I know I'm generalizing but really, overall, that's the only difference.

 

[Line Out]

A D8444 is also spec'd at 2 x 2,0 W + 3,2 W (+-1dB) (d=10%) in service manual.

 

[Cpl-Chronic]

A D8444 is also spec'd at 2 x 2,0 W + 3,2 W (+-1dB) (d=10%) in service manual.

Yeah, that still blows my mind & I feel a little ripped off when the 'Owners Manual' states 28w RMS with no THD numbers at all. I think poeple can understand my mistake in assuming they were wrong when I'm staring at very different numbers here & you can see my speakers really move ALOT. My ears tell me a different story & I'm still trying to sort it out between what I see posted in various manuals, datasheets, websites, etc. & what my ears tell from past experiences, etc.

Again, the sound isn't perfect or like a BOSE but for a ghetto-blaster, it sounds pretty BOSS. It isn't a CONION killer yet but those little amps are working for the money, believe me & the working horns help too.

 

[Kinietis11]

That's a super sweet upgrade . I always wanted to do something like this on my own. I hope i will in the future.

 

[Channon]

:unknown: Awesome

 

[Cpl-Chronic]

50Hz Hi-PASS F-MODS came in today!!! YAY!!!

The line level filters arrived for my line-in inputs & they work by rolling off the LINE IN signal below 50Hz @ 12db/oct. This cuts out the sub-sonic range & prevents the AMPS from wasting TONS of power in that 20-50Hz range. It's the same idea as rumble filters on your PHONO input to weed out turntable rumble, disc wow, etc. It should give me more headroom & add to my SPL output down to the 50Hz mark. This is perfect for the 'LOUDNESS' effect that made the boomers so great, back then & now. The video is crap but you can hear the bass line & the shaking of the cabinet & book shelf.... Bass, Treble & volume are ALL @ about the 3:00 position, the 'Super-Woofer' controls @ 0db(FLAT) & you may be surprised by the fact that the 'Loudness' switch is in the 'OFF' postion. You have to watch the entire video in full screen to get a good look at the controls & woofer travel, etc. Shelf rattling DUB

Below is a list of MODS that were done to the Triple-7 ZEEE. Note that the guts & amplifiers are completely stock, including the line-in, pre-amp & AMP stages. Only the speaker components & 2-way crossovers have been replaced while the cabinet was dampened with deadmat & insualated to eliminate reflections & vibrations, as much as possible. I still have to deadmat the back panel & possibly brace it with long bolts to get rid of vibrations in the upper bass region.

List of MOD details:

Speakers upgraded. After trying different combinations of woofers the best sounding combination is as follows:

The outer woofers are part of a center channel kit which have 2 @ 6.5" woofers,
The frequency response is qutie good & flat up to 4Khz & the free-air resonant freq. or FS point is 63Hz. Perfect for upper bass punchy-ness & can be found here:
http://www.ebay.ca/itm/360429029111?ssP ... 1423.l2649
The black sub-woofers I used for the 'Super-woofer'(s) have a optimal sealed enclosure of just 0.16 cu. feet & a resonant freq. or FS point @ 38Hz Perfect for the bottom octaves so many boom-boxes lack. They can be purchased here:
http://www.ebay.ca/itm/290734609719?ssP ... 1423.l2649

box dampened & insulated
2Khz/2-way/4-ohm crossovers added for outer 2-way system
the transformer moved to accomodate larger driver magnets/assemblies
F-MOD filters applied to the line-in for a 50Hz high-pass signal




Both sets of woofers are 4-ohm each so you can match impedances between old & new drivers & the unit still functions well. If you update your GF, I STRONGLY suggest using this combination of woofers to get a more flat BASS response down to 35Hz. The outside woofers are from a center channel kit & have a stiffer cone allowing it to give lots of punchy tight bass & remain flat up to about 4KHz. They do a great job of blending in between the sub drivers & the horn tweeters.

 

[ismaels2000pr]

In my Gf-777 tweeters mounting plates, i remove the ring that makes contact with the cone , exposing the total mass of the cone to be in contact with the air, and now my unit got noticeable boost in Highs with the original tweeters.

 

[Cpl-Chronic]

In my Gf-777 tweeters mounting plates, i remove the ring that makes contact with the cone , exposing the total mass of the cone to be in contact with the air, and now my unit got noticeable boost in Highs with the original tweeters.

Does the center dome of the tweeter still project sound throught he neck of the horn like the original design?

It's an interesting point you make about the ring surrounding the center-dome of the tweeter. Mine sounds balanced as it is & I find nothing really lacking in the highs. My feeling is, if I remove the ring, more refracted waves will emanate from the entire tweeter & the mids will become strionger over the treble & sound slightly noisy or strident. The problem is I don't have spare lenses to try out the experiment.

 

[ismaels2000pr]

I don"t remove the whole tweeters mounting plates, just only remove (ware out) the ring that make contact with the cone itself in the inside of the plate, now the cone have more airflow in contact ,even from the outside it look the same, and the tweeter still have the protection of the back waves.. only high's sound..

 

[Cpl-Chronic]

I don"t remove the whole tweeters mounting plates, just only remove (ware out) the ring that make contact with the cone itself in the inside of the plate, now the cone have more airflow in contact ,even from the outside it look the same, and the tweeter still have the protection of the back waves.. only high's sound..

hmmm....very interesting idea. I may try it out.

 

[Cpl-Chronic]

I got some new 'Super-Woofer'(s)!!! They are 3.2 ohm 50w drivers with a decent size magnet, a large voicecoil & a super light rigid cone coupled to an inverted polymer surround. They are in perfect shape & go perfect witth the inset placement of trhe superwoofers. Here's a pic:

They're nice & black & go great with the retro look. They really kick hard in the 60Hz Kick-drum & can go as low as 40Hz. The 3.2 Ohm load & the exremely high efficiency for a woofer are hard to beat & the old 'subs' pale in comparison. I need to improve trhe mid to high blending between the tweeters & woofers. The outers are due for an upgrade too.

Here's a crude video of the Gf in action & the new woofers are working good...

Stones: SLAVE

The sound & lighting is so much more vivid & lively in person over my crappy kodak 10M point & click....

 

[Line Out]

Now just get some chrome dust caps for those and voila!

 

[Cpl-Chronic]

Now just get some chrome dust caps for those and voila!

Yeah, chrome caps bouncing the RGB's would look pimp-tite but I like the black center caps too & those speakers are really good as they are & rare. I don't want to mess with them at all really,. They were really hard to find & 3.2 Ohms doesn't come easy or often, especially in a nice efficient speaker like these.