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 (http://www.lansingheritage.org/html/altec/catalogs/1971-mon.htm) ( located here in the Lansing Library (http://www.lansingheritage.org/) ) & GPAs' pdf product sheet for the 604-8H-III (http://www.greatplainsaudio.com/downloads/604_8H_III.pdf)found over at the GPA website . (http://www.greatplainsaudio.com/products.html)

- This picture is also acting as a 'linked source' & is presently displayed over in this thread (http://www.hostboard.com/forums/altec-users-board/187143-gpa-altec-604-series-3-crossover.html)/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 (http://home.earthlink.net/~jmarkwart/id22.html) as it is used by the 604E Super-Delux . It's schematic is here ! (http://home.earthlink.net/~jmarkwart/sitebuildercontent/sitebuilderfiles/n1500a.pdf)

- JeffM also talks about his best attempt at modding this crossover here at his website (http://home.earthlink.net/~jmarkwart/id22.html).

- 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.


:yes::yes::yes:

[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 (http://www.lansingheritage.org/html/altec/catalogs/1971-mon.htm) ( located here in the Lansing Library (http://www.lansingheritage.org/) ) & GPAs' pdf product sheet for the 604-8H-III (http://www.greatplainsaudio.com/downloads/604_8H_III.pdf)found over at the GPA website . (http://www.greatplainsaudio.com/products.html)

- This picture is also acting as a 'linked source' & is presently displayed over in this thread (http://www.hostboard.com/forums/altec-users-board/187143-gpa-altec-604-series-3-crossover.html)/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 ! :D:applaud:

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??

[Steve Mac]

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??
Ha! didn't notice that!
Well, took a picture and the label on my driver is different!
http://www.superbadcat.com/images/stereo/511e_6.jpg

[Steve Mac]

Steve, Great Stuff ! :D:applaud:

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.

Thanks Earl...big thanks to Greg (GM) and the great whack pack over at the altec forum for their advice/theory/opinions and understanding of horns and especially altec history. Also, thank God GPA is up and running making brand new 515s and 288s.

The system is essentially built around the 210 LF horn....chopping off the reflex...re-shaping for home theater...allotting within the curve for an inset mid range horn...designing a rear chamber....getting the horn to load down to 80Hz.
The midbass design was 90% of the work...
Here's a link when I was doing some 3d modelling if yer interested:
http://www.superbadcat.com/midBassDesign/midBass.htm
I had a blast building up this system. When I finish the system I'm probably going to drill through the mid bass base with a pipe to route the mid range speaker wire and toughen up the support for the mr horn...it's all just getting held in place temporary right now.

I haven't figured out how I'm going to finish it all...my rock and roll friends have all voted for snake skin tolex... :)

(I'm sorry if this thread is getting hijacked....)

[darkmatter]

Hi

Has anyone got a copy of the crossover schematic of the N604-8A for GPA 604 8H III Driver?

TIA

Simon :)

[Horn Fanatic]

Hi

Has anyone got a copy of the crossover schematic of the N604-8A for GPA 604 8H III Driver?

TIA

Simon :)

If you're using the 604 8H III, IMHO, the stock network isn't really suited for high end audio. I own a pair, so I will suggest you either design and build your own, or pay someone who knows that speaker intimately to design a decent network for them. I believe Jeff Markwart designed a network for the 8H II some time ago. AFAIK, the 8H II and 8H III are the same speaker, save for the new horn Bill Hanuschak implemented about 5 years ago. That Mantaray horn is a real dog. The 604 8H III IMO, is the best sounding 604 model ever, provided it's driven by a decent network. Either that, or run them active as I have.

Just curious. What volume of enclosure are they loaded in?


H.F.

BTW - Jeff is a very nice chap to chat with, if you can pry him out of his Corvette.

FYI - http://home.earthlink.net/~jmarkwart
(http://home.earthlink.net/~jmarkwart/)