Broke down. Got a duplex.

[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 )

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[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