Broke down. Got a duplex.

[Alien_Shore]

I gave in and picked up a beat up 604E. Sent it off to Bill to have him give it the GPA treatment.

Woof T/S:


Vas:


Horn T/S:

[Panomaniac]

Cool. Let us know how it is when it gets back from Oklahoma.

[voice of the theater]

Nice! Please keep us posted. I'll bet that speaker sounds amazing after you get it back from Bill/GPA. BTW, I'm inventing a triplex speaker. Altec 15" Biflex woofer with h.f. driver/horn (not to be confused with a triflex?)....

[donaldpatten]

Congrats

Welcome to the Duplex family
Are your magnets alnico or ceramic
I noticed the woofer R is about 7 Ohms. I expected to see about 12. What V.C. Are you getting on the new GPA?

Don

[Alien_Shore]

Ummmm,
I got it back from GPA yesterday - those measurements reflect the "GPA treatment"...
It's a huge mother - 604E so it's Alnico.
And yes, Don, I expected the same thing from the woofer VC - Bill told me he was putting in 16 ohm VCs for both HF and LF...

I only had time last night to very briefly hook it up through the Behringer dcx2496, as I don't have a XO for it yet. No cabinet either. It sounded...meh. The mids were very clear, and I think I got a glimpse of what everyone talks about that "point-source" sound - some extremely revealing details from the recordings, but as you'd expect I guess from an unmounted speaker it was utterly lacking any low end. I need to throw together a passive XO (plan to use Markwarts design as a starting point). But it is curious that the Woofer R is reading like an 8ohm VC is in there. Some of the other T/S params match very well with what is posted on Todd's list, while others are off by quite a bit. Does the MM number look right? I thought it was curious that DATS came back with a number that essentially equaled the amount that I applied to the cone to calculate the Vas. The math for that doesn't work out...

[Panomaniac]

Ah, those are after - sorry! I'd say Mms looks low, that's a light cone. But I'm not sure. I'll see if I can dig up files on some GPA reconed 604s (ferrite) I had here.
From the plot, it looks like an ohm woofer and horn to me.

[Altec Best]

Mike very nice schematic.. Draw them things up nice these days .

[Earl K]

@Alien_Shore

Mike, nice to see you kicking around these old haunts again.

If ( when ) you see this, can you answer a question or 2 please?

A good decade back you displayed a pic of the response of your 604E using the N1500a as the crossover.

"Was that with your GPA refurbished 604E's after Bill ( GPA ) had used the lower than expected impedance voice-coils ( more or less 8 ohms versus 16 ohms )" ??

If so, I'm really intrigued at how well your non-604E ( 8-ohm ) elements actually modelled for LC values originally chosen ( by Altec ) for the N1500a and it's higher impedance drivers.

Also, do you remember what distance you used for the off-set of the 2 drivers Acoustic Centers ( within PCD )??

Thanks! EarlK

PS: ( link included below for a much larger version of the pic >> if a member at HFH )

Log in | HiFi Haven

[Alien_Shore]

I'm looking through some of my old posts, computer files, notes, etc. to see if I can answer your questions. Yeah, it's been a minute hasn't it!?

Mike, nice to see you kicking around these old haunts again.

Hi Earl and thanks - sorry for the lag in replying here - the holiday rush has had me strapped for time.

A good decade back you displayed a pic of the response of your 604E using the N1500a as the crossover. Was that with your GPA refurbished 604E's?

The graph I posted was not from a FR test, it was the sim output from a model that I had done with PCD. In that model, I had imported the FR curves and impedance data, so I presume that data was from the drivers with the refurb'd VCs. Glad to publish those data if you want to see it! Looking at the sim in excel, it appears that a parallel two-way config was used. Driver offsets were zero. The woofer design in the sim is 2nd order L/R crossing at 1.5 kHz 70 dB. There is a series RC (Zobel) with C=13 uF and R=10 Ohm, followed by the lowpass 2nd order section with L2=1.5 mH and C2=8 uF. For the HF section, it was 2nd order parallel with C9=6.0 uF and L9=1.0 mH, with a 0.3 Ohm DCR. There is a 3.0 Ohm series resistor after the HP section AND there is an 8.0 Ohm resistor in parallel leg 1. It will take me a bit to draw this out in a schematic, as I'm sure this description is confusing

[Alien_Shore]

@Earl K

Here's a quick / dirty schematic from that sim network:

604e Sim network design

Let me know if something looks weird or you have any questions...