my first altec (604G)

[joe3rp]

I made my plunge ...my first ALTEC. I am a low powered SET -45 / 2a3 / 300B addict. I needed high efficiency speakers. I started with Klipsch KLF-20 and then TWQP Fostex 208es and now this TWQP Altec. How does it sound? I am now selling the other 2 speakers.





Why is the tweeter/mid mounted vertically, I am just experimenting with horizontal vs vertical dispersion control ... I have a smallish room ...Will try the more "normal" install soon.

imaging, bass, clarity, dynamics and EFFICIENCY ...WOW

[Albert B.]

Those are beautiful speakers. I am sure you are very happy. Don't take this wrong, but do you think they would benefit from super tweeters? I don't know. I am just asking if you have any plans or think they might me needed.

[joe3rp]

I did try it with a FOSTEX T-96A super tweeter with a simple first order hi-pass filter run without attenuation (same output level as the woofer). This tweeter has a claimed efficiency of 103 db/watt and a VERY FLAT frequency response to 35,000 hz. Did a I hear a difference or did it help? Not much for me to keep it on. I am in my 40's so maybe my ears are not as sensitive to Hi frequency as the younger ones. But in my opinion using material with a lot of "supertweeter material" ...the 604 can tweet way up there as is.



FYI the stock altec 604G crossover was also not to my liking. I found it too dark, slow and veiled. So I made my own a simpler one. Maybe the stock crossover was designed for more modern amps and not low damping SET amps which I prefer.

[hmole]

That is a beautiful cabinet, where did the design come from?
Harry

[boltupright]

Absolutely stunning! those cabs are just gorgeous, I would give those drivers a 1/4 turn.

[bfish]

Beautiful wood cabs! Do you get any early HF reflections with the drivers rear-mounted? I see the opening is chamferred, but it's still a reflective surface in front of the horn, but maybe out of the pattern enough.

[joe3rp]

Originally posted by boltupright:
Absolutely stunning! those cabs are just gorgeous, I would give those drivers a 1/4 turn.

<font size="2" face="Verdana, Helvetica, sans-serif">Thanks for the compliment. The top, front and bottom is made of 1" solid ash. Lots of acrylic varnish. If you notice the outboard crossover are also of solid ash hardwood.

As to the quarter turn ...I am still trying it out. I know I am going out of norm. I have a relatively small room and am experimenting on controlling the horizontal dispertion. I am trying to see if the side wall reflection with a vertically mounted horn has less negative effect. My theory is that since these drivers were designed for large area P.A. system ...the normal dispersion might be too much for my "small room".

I will rotate it "normal position soon".

Beauty with us DIYer is we go "out of the box" to prove ourselves wrong ...the hard way ...

[joe3rp]

Originally posted by bfish:
Beautiful wood cabs! Do you get any early HF reflections with the drivers rear-mounted? I see the opening is chamferred, but it's still a reflective surface in front of the horn, but maybe out of the pattern enough.

<font size="2" face="Verdana, Helvetica, sans-serif">Thanks for the compliment.

I did not think of that, but maybe just from inspection ...the end of the sectoral horn is not that much recessed with respect to the opening...maybe the driver/horn pattern is more forward. How do you suggest I check, I am in the process of making another cabinet for a friend using a UREI 604 ...I would like to correct it befor I cutout. Any advice would be appreciated.

[bfish]

This is really a question for someone with more knowledge of acoustical physics than myself. I suspect it may have even been an issue in the developement of the 604 series, as the 'long' ends of the radial-shaped horn mouth are behind the mtg face of the driver itself, something which the MR-style horn improved upon, notwithstanding the improved dispersion pattern.

I think the possibility of early reflections should only apply to frequencies with a shorter physical wavelength than the distance from the horn mouth to the reflective surface. Were I to test for this, I'd compare the same 604 in a front-mounted, equivalent cab to the one in your setup, using a sine wave sample of frequencies in the suspect band, with a mic at signifigant distance (listening distance) feeding a scope, looking for any out-of-phase, secondary traces. I'm sure this has already been done exhaustively, and someone with knowledge of the phenomena could likely tell by looking at your setup if this would be an issue, or not. The only reason I even wondered about it, is that all the factory-mounted 604s I've seen were front-mounted, which leaves me wondering how the earlier small-frame duplexes were handled, as the small-frame is conducive to rear-mounting only.

[GM]

Greets!

Nice woodworking! I wish I had the patience!

FYI, dispersion is controlled by a radiator's angle at whatever dimension you're calcing/measuring, so from just looking at the 604's horn you can see that its wide dimension controls to a much lower frequency than the other. IOW, as it's now positioned it's acting somewhat as a slot to *increase* its horizontal dispersion and limit its vertical, like a ribbon or line array, up to the point where it begins beaming in each axis. Since we are much more sensitive to horizontal dispersion, the driver should be oriented per the factory pics in a typical Hi-Fi app to limit room interaction and as you now have it in a really large space.