Altec 604E vs GPA 604-8H-III

[Earl K]

Hi,

- Here's a comparison of frequency responses for the old 604E ( circa 1971 ) vs GPAs' 604-8H-III ( 2009 ) .

- I've stretched the vertical scale ( of the originals ) so that any interested party will get a better idea of what's actually going on .

- The sources for the FRs in this collage / are / the Altec 1971 Monitor catalogue ( located here in the Lansing Library ) & GPAs' pdf product sheet for the 604-8H-III found over at the GPA website .

- This picture is also acting as a 'linked source' & is presently displayed over in this thread /at Todds' Altec Hostboard .

>< cheers

[robertbartsch]

So the difference is that for the new driver(s) the HF does not roll off as much past 10K as the old Altec, I suppose.

Could you provide any data on the diaphragms and crossovers that were used for the tests?

[Tom Brennan]

I wonder if the GPA was using a crossover with high frequency compensation. I doubt the Altec was.

[Earl K]

Could you provide any data on the diaphragms and crossovers that were used for the tests?

- The 604E was a full 16 ohm duplex ( HF & LF ) .
- I don't know if Altec used in the CD portion of the 604E(s) a "light-weight" 16 ohm version of the 23744 ( the "lightweight" 8 ohm diaphragm version of the 21597 ) . From the looks of the curve that I've shown , it doesn't too likely .

- Jeff Markwart outlines the N1500A crossover here as it is used by the 604E Super-Delux . It's schematic is here !

- JeffM also talks about his best attempt at modding this crossover here at his website.

- Re; the diaphragm in the GPA 604H duplex / ask Todd White, he'll know ( I can only speculate it's the standard 34647 ) .

So the difference is that for the new driver(s) the HF does not roll off as much past 10K as the old Altec, I suppose.

- It's not just the UHF that is better, the LF extension and the transition in the crossover region are both better .

I wonder if the GPA was using a crossover with high frequency compensation. I doubt the Altec was.

- I assume that's the case with the GPA crossover .
- Jeff Markwart shows that the original N1500-A had no HF compensation ( in the pdf of the schematic that he publishes ) .

>< cheers

[pierce]

I'm not sure its that valid to compare two different frequency responses taken at differnet times on different equipment. I'd feel a lot better about the comparo if both charts were made on the same setup by the same neutral person at the same time.

[John]

I'm not sure its that valid to compare two different frequency responses taken at differnet times on different equipment. I'd feel a lot better about the comparo if both charts were made on the same setup by the same neutral person at the same time.

[JBLRaiser]

Hi,

- Here's a comparison of frequency responses for the old 604E ( circa 1971 ) vs GPAs' 604-8H-III ( 2009 ) .

- I've stretched the vertical scale ( of the originals ) so that any interested party will get a better idea of what's actually going on .

- The sources for the FRs in this collage / are / the Altec 1971 Monitor catalogue ( located here in the Lansing Library ) & GPAs' pdf product sheet for the 604-8H-III found over at the GPA website .

- This picture is also acting as a 'linked source' & is presently displayed over in this thread /at Todds' Altec Hostboard .

>< cheers

was that driver combo(604E) considered TOTL as far as frequency response goes?

[Earl K]

Historically speaking......
was that driver combo(604E) considered TOTL as far as frequency response goes?

- This is the duplex driver that was Altecs' standard offering to studios seeking monitoring .

- It was current to the time period that JBL developed & released the 4310 ( which targetted the 604 duplex in a successfull attempt to redirect monies from Altec to JBL ) . So, in my eyes, there's historical importance about what was considered "studio-standard" response for the time .

- The "Big Red" series of monitors also came from this time period ( with it's improved FR response ) .

- If one has ever looked at the 4310s' FR and the interactions that occur when adjusting the pads / one can surmise just how easy a target, Altec made themselves.
- ie ( the 4310 ) ; More bass from a smaller box / same forward FR characteristics from the upper midrange / & still,,, easier to listen to because it was an all cone system that was cheaper ( & easier to place ). Since flat-line frequency response was obviously not important it was a new game .
- Like shooting fish in a barrel I'd say ( IMHO )!


- My take here is that improving the duplex just wasn't a big priority to Altec at the time / and / they were essentially asleep at the wheel when others decided it should be .

>< cheers

[JBLRaiser]

I frequent GPA's site and click for updates on their products. It seems there complete system promises have taken an excruciatingly long time to materialize. Just wondering, do they have a prototype box in mind for their duplex drivers and would they have tested their duplex in such a box?

[Steve Mac]

The GPA 1" driver utilizes the radial waveguide plug. The high end probably reflects this.

recent experience:
I've got a new pair of the GPA 288H drivers and the high end is much better than the 808a driver(alnico,removed loading caps,lined the back chamber mod,had gpa install new diaphragms+remag). The drivers were both installed on the 511 style horn(511e,511b). No comparison on the UHFs...and I gotta believe the phase plug is the reason.

[Earl K]

I frequent GPA's site and click for updates on their products. It seems there complete system promises have taken an excruciatingly long time to materialize. Just wondering, do they have a prototype box in mind for their duplex drivers and would they have tested their duplex in such a box?

- I wouldn't know / & being a DIY sort of guy, I would most likely ignore anything that they might offer in the way of enclosures ( & crossovers ) .

- Anyways, with the apparent demise of Iconic ( Manufacturing ? ) I figure the market ( over the last few years ) has quite firmly spoken out against "turnkey" products or solutions from them.

>< cheers

[Earl K]

I've got a new pair of the GPA 288H drivers and the high end is much better than the 808a driver(alnico,removed loading caps,lined the back chamber mod,had gpa install new diaphragms+remag). The drivers were both installed on the 511 style horn(511e,511b). No comparison on the UHFs...and I gotta believe the phase plug is the reason.

Nice purchase ! any chance of a few pics of these new guys ?

I use 288-8Ks & find their huge UHF boost at 12K perfectly suited to my hearing ( which has trailed off by 14K ) . I'm confident the spike is the result of the radial phase plug .

Here's an ARTA "look-see" at what my right channel MTM looked like a while back ( the horn is a JBL 60 x 30 / paragon elliptical plus 1.4"-2" adapter ) .

This MTM uses a sealed 10" over a ported 14" ( le10H & le14H ) / both in smallish boxes .

cheers ><

BTW;
Pic #2: The JBL 2431H looks like this on the same horn ( though with a passive notch at 6K ? ) . I can actually make the 2431 a bit smoother when compared to the Altec / but I do need to use a tweeter to emulate that UHF spike ( which I need as fake UHF ) . Here's a look see at its' FR . I use these for SR work where actively goosing the UHF is not a problem . They're a great sounding driver between 1K & 11K / outside of that range they struggle somewhat .

Pic #3: Here's the 288-8K on the Emilar EH-500 "baby" radial horn . The H5038 ( paragon horn ) seems to be smoother .

[Steve Mac]

Here's some pics I took today...forgive the unfinished nature...but that phase...with the addition of the 288 drivers is now ready to think about.
Enjoy:
http://www.superbadcat.com/images/stereo/511e_5.jpg
http://www.superbadcat.com/images/stereo/511e_1.jpg
http://www.superbadcat.com/images/stereo/511e_2.jpg
http://www.superbadcat.com/images/stereo/511e_3.jpg
http://www.superbadcat.com/images/stereo/511e_4.jpg

here's a driver pic(courtesy of the Lynn Olson thread)
http://www.superbadcat.com/images/288_rear.jpg

[Earl K]

Steve, Great Stuff !

Love that big home-theatre thing you've got going there, wow !


>< cheers

ps; If you don't mind, I'll upload some of your pics into this thread / so that / if & when your picture hosting provider changes / it's not all lost into the digital ether.

[hjames]

That is an amazing looking system - would love to give it a listen, but ...

Its Shielded not Sheilded

... they really mispelled it on the label??