Altec 604-8G sanity check

Audionut

Next Round Is On Me
GPA diaphragms are up to $148 each. I'll certainly look into repairing the voicecoil lead.

If it comes to the worst, the $148 diaphragm cost makes the complete overhaul look downright affordable.
I agree with @billfort , do both diaphragms at once for a more even sound base. They will send you your old ones back with your speakers if you ask them to. You can keep or sell the single good diaphragm or keep it as a backup. I still have mine.
 

billfort

Administrator
Staff member
I still have my good one around here as a spare somewhere too. I've heard the fine leads get brittle with age and the strain of years in use, and end up being the weakest-link when over-powered, but there isn't much risk of that with the blazing 1.5 to 5wpc mine see. :)
 

John Frum

Secret Society Member
Hoping to be rocking these 604-8G by fall, and I've got a few preliminary notes on boostrappy implementation.

Leaning towards working with what I've got and bi-amping the 604 with a DSP and painfully boring solid state amps, with the intent of trying passive crossovers and different amplification farther on down the line.

I'd like to hear your thoughts on different cabinet schemes. Obviously something like a 620 clone or MLTL would be great to try in the future, but again, working with what I've got, I have two choices:

The first cabinet option includes using the Duplexes in narrow-baffle 3.7 cu. ft. cabinets (sealed?), sitting above 6 cu. ft. lowboy cabinets loaded with Fostex FW405 15" woofers, also crossed over with DSP.

The second option aims for simplicity in forgoing the helper woofers, and rather puts the 604-8G in the 6 cu. ft. cabinets, and raises these horizontal-orientation cabs to ear height with about $180 worth of hairpin legs.

Going to need a bunch of speaker wire. Looking at Belden 9497. For damping material, looking at UltraTouch denim insulation.

The bad diaphragm is still an unknown quantity, but I am excited by the possibility of repairing the voicecoil lead rather than immediately shucking out three bills for GPA 'phragms.
 
I
I heard recently (maybe on this forum?) that GPA has raised their prices rather dramatically (like 100%) in the past few months. Apparently they weren't making any money. I don't have any firsthand knowledge of this but I did see a couple Ebay ads from GPA that seemed to support this.

I just got round to ordering the 8ohm diaphrams for my 808 drivers (converted to 802) and i can confirm there has been a big increase, not quite double though but i thought i better get in before another increase. I also got a pair from china for pennies to compare, not expecting much though
 

Audionut

Next Round Is On Me
If there's one thing I'm really good at, it's waffling on the implementation of audio gear.

I'm meeting with a local cabinetmaker the first week of October, in hopes of coming to an agreement on building a pair of unfinished plywood cabinets.

Next up is where I wish I had some graphic design skills:

My plans right now are for towers that are 47" tall x 23" x wide x 16" deep. Cabinets would be slightly narrower than the Altec 620, with Duplexes mounted slightly closer to the top of the baffle - the hope being that the baffle width and driver placement aren't fudged to the point that the Markwart crossover wouldn't work well, if implemented.

Cabinet dimensions are somewhat beholden to the available sizing of 4' x 8' 3/4" marine-grade plywood sheets and 2' x 8' veneer rolls. Also, the height helps get the tweeter at ear level.

Drivers would be surface-mounted, and the front baffle recessed ~1". The grills would be also be made out of cloth-wrapped 3/4" ply, and would have cutouts for the drivers - almost like recess-mounting the drivers.

I want to commission two sets of front baffles, and two sets of horizontal upper bracing, so that I can configure the cabinets either with the 604 and Fostex FW-405 15" woofer on the baffle, with a solid interior divider, or just the 604 on the baffle, with a window brace instead of divider. Preliminary configuration would divide internal volume between a ~3.5 cu. ft. chamber for the 604-8G and a larger ~5.25 cu. ft. ported chamber for the Fostex FW-405. In this configuration, the helper woofer is always run via DSP crossover and separate amp, regardless of what I'm doing with the 604. In the alternate configuration, the 604 is by itself in the ~8.8 cu. ft. ported enclosure.

First off, is that description clear? Second, does it seem like a good idea, over building a plain-Jane 620 or MLTL?
Not sure how I missed this post but wondering how things went with the plans on the cabinetry and design along with the other implementation/ideas listed?
Pretty excited for you in getting them shipped out. The Work GPA does is first rate and well worth it.
 

John Frum

Secret Society Member
Not sure how I missed this post but wondering how things went with the plans on the cabinetry and design along with the other implementation/ideas listed?
Pretty excited for you in getting them shipped out. The Work GPA does is first rate and well worth it.

The cabinetry plans are still somewhat in flux, but rapidly gelling.

I still love the idea of putting the Duplexes above the Fostex FW405 lowboys in smallish cabs or open baffles. But honestly, it’s less and less appealing to think of having two pairs of speaker cabinets, two or three stereo power amps, and an electronic crossover or DSP. That’s especially true since I’ve been having so much fun with the Almarro A205A MkII integrated amp.

I’m reasonably sure, at this point, that the 604-8G will be housed by themselves in a pair of 1966 Japanese custom towers (after remodeling the front baffles and adding bracing). They’re only 20” wide, but the WAF is high, they’re on-hand, and they’re 8.5 cu. ft.

Of course, that plan marks the Fostex woofer cabs as XXL surplus speakers that it would pain me to get rid of...
 
I’m reasonably sure, at this point, that the 604-8G will be housed by themselves in a pair of 1966 Japanese custom towers (after remodeling the front baffles and adding bracing). They’re only 20” wide, but the WAF is high, they’re on-hand, and they’re 8.5 cu. ft.
Please post pictures of the cabinet candidate.
 

Audionut

Next Round Is On Me
This may have been stated elsewhere; if you’re happy with those speakers and the fabric then you are more than halfway there. Worst case scenario you can change the fabric on the grills and get the wife involved with it (for her to be all the more on board with these cabinets and project as a whole).
I have a little Almarro envy BTW. :smile:
 
Thanks for sharing. I agree with Audionut . Those look very nice. You may be able to sell the drivers from those cabinets for more than you think.
 
Yeah, that depth adds to the numbers pretty quickly. It's gotta come from somewhere.
They look nice. Getting the driver up to ear height would be the only issue it appears then.
 
So about here on drivers? That may leave room for your added driver idea.
 

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Very similar to mine actually which currently hold 12" Tru-sonics and the fostex sitting up on top. Mine are the same width and height with small riser under. But only 14 deep.
 
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