Dumb speaker impedance question - Altec Content

ictwoody

I like vintage gear — my preamp is from 2007.
I'm a moron, so I need help.

This weekend I hope to build some Altec 614 Cabinets to build a set of speakers that are essentially the JE Labs 2-way setup. Discussed here...

http://jelabs.blogspot.com/2014/01/altec-2-way-horn-system-redux.html

and here

http://jelabs.blogspot.com/2014/01/altec-2-way-xo-update.html

I have 414's that I'll be having re-coned at GPA and a pair of 802's that need 'phrams, so I have the ability to get them back as either 8 or 16ohm drivers.

Because I'm a neophyte who is better with the aesthetic design than the technical side, I'm confused as to final impedance of the system when completed. I want an 8ohm final load for this speaker (or thereabouts) — so, my question is do I want to keep these units as 16ohm drivers so that in parallel they yield an 8ohm-ish final impedance? Or do I want them as 8ohm drivers?

Sorry for the bush-league question... but I just need someone to give me the definitive answer so I can get them going.

Thanks in advance,
- Woody
 
Get 8 ohm drivers if you want 8 ohms, but you will have to recalculate the xover, which is specified for 16 ohm drivers.

A simple matter.

Think about this: The purpose of a crossover is so that the drivers do not operate in parallel!

aka "Dividing Network"
 
Get 8 ohm drivers if you want 8 ohms, but you will have to recalculate the xover, which is specified for 16 ohm drivers.

A simple matter.

Think about this: The purpose of a crossover is so that the drivers do not operate in parallel!

aka "Dividing Network"

Glad you chimed in Joe... didn't you help Joseph develop that solution, running the 414 fullrange and using this network?? He actually posted a modded schematic for 8ohm drivers... here it is. Is this correct?

That's the simple answer I was looking for. Thank you.

- Woody

File Nov 14, 5 51 05 PM.jpeg
 
JE doesn't need my help. He is a world class super nerd on his own!

I didn't use a HF peaking network and used a ~1.5uF cap (16 ohm driver). Given the natural rolloff of the 802/32, the sensitivity at this 7-8k crossover point approximates the sensitivity of the 414Z, so things blended quite well. Two slow, overlapping rolloffs. Depending on the box and the room, a touch of HF attenuation might be in order and possibly adjustment of the cap value.

I kind of like rolled off treble which sounds more realistic and natural to me than the insistent TSSS TSSS of modern speakers, but if you want more tizz, the EQ in the crossover above will get you some of that.

I used an RTA app for my iPhone to rough things in. I have speaker measurement software but the phone is handy and does the job.

I sent a pr of 802s to GPA for remag and new diaphragms and they came back sounding really superb.

This is a great setup that JE is promoting (even though he destroyed the cheap availability of the 32 horns) and you can experiment with different xover options to suit your preference. I like to let the 414 run free. The 414 is a really nice 12" and plays "full range" quite nicely.
 
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