Broke down. Got a duplex.

**donaldpatten** · September 21st, 2012, 02:18 PM

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** · September 21st, 2012, 05:21 PM

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** · September 21st, 2012, 05:34 PM

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.

**Earl K** · September 22nd, 2012, 09:54 AM

Originally Posted by AlienShore

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

From your measurements, it appears the "GPA treatment" is to turn a 16 ohm 604 into a 10 ohm 605 ( if that DAT measurement is to be believed ) .

Time will tell if your measurements hold water ( fyi, others using WT3, which was the G1 version of DATS , had many problems with it, maybe DATS is better ??? ) .

The current measurements tune up quite well ( if accurate ) using a 9.5 cu' enclosure tuned to 25hz .

**Alien_Shore** · September 23rd, 2012, 06:29 PM

Originally Posted by Earl K

From your measurements, it appears the "GPA treatment" is to turn a 16 ohm 604 into a 10 ohm 605 ( if that DAT measurement is to be believed )

Yep - that's what it looks like. I sent GPA an email - we'll see if they reply.
In the meantime, do you recommend another (more reliable) method for testing T/S?

**Earl K** · September 23rd, 2012, 09:11 PM

WT2 is more reliable than WT3/DATS ( different maker with a different way of measuring ) .

REW has a TS parameter measurement area ( you need to wire-up a small box ) that uses the same method as WT3 .

Personally, I wouldn't bother GPA with this type of thing until you've gotten similar measurements from at least one other measuring program.

**Earl K** · September 24th, 2012, 07:31 AM

- Every once in a while it is worth the diy hobbyists time to check ( recalibrate ) the validity of ones measurements by using another method ( really , it's simply part of the scientific method ).

- For TS parameters ( when checking these "all-in-one" devices ) one can use the old standby method outlined here !

- I believe that verifying Re, Fs & Qts ( Qms, Qes ) is enough to know where ones device stands .

**Altec Best** · October 21st, 2012, 12:46 PM

Originally Posted by Earl K

( fyi, others using WT3, which was the G1 version of DATS , had many problems with it, maybe DATS is better ??? ) .

I had issues with mine... After a couple months the software is the problem IMO. It kept crashing on my computer..So I sold it.. And worked fine for the gentleman I sold it too.. So if you have something on your computer (Other Audio Software) you could have some conflicts... I opted for the WT2 from Smith & Larson.. 10x better IMHO... And it worth the extra $60. A must for the DIY hobbyist IMO&E.

**Alien_Shore** · November 24th, 2012, 09:29 PM

The mad scientist experimentation lab has been getting a workout:

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And today, I wound my first coil... Pain in the ass, let me tell you. But really, it's amazing how accurate the Shavano DIY coil calculator is...I made my own form with pvc pipe and rolled that sucka LoL. ...
Anyway, here's the ugly thing - I affectionately call it the 2.287 mH Christmas coil!

54828180605 c1601a2b78 c

DIY coil winding is an interesting hobby, but I think to really get into it, you'd need something that can count turns or feet automatically for you, and some kind of oscillating line alignment gadget on there like a spinning reel does. I don't know, maybe I'll try it again and see, it is nice to be able to create precisely the inductance that your circuit needs, but it seems awfully time-consuming for what you get.