Altec Build with 414a and 811

[larbor]

Hi,

Need some help on a crossover for Altec speaker build. Build will include 811 Altec Horns with 806a drivers. For low end going with Altec 414a’s, focusing more to the mid end. The box is around 3 cubic ft (using an old Electro Voice box for now). Horns will be sitting on top of the boxes. I want the cross over to be around 1200hz and to be outside the box for easy changes. I was going to use x-SIM software, but not sure how to get the frequency files (.frd and .zma). I don’t have equipment to test speakers and create these files.

Does anybody have a crossover spec. I can use to get started. I know I will be mixing ohms – Horns are 8 ohms and 411s’ are 16 ohms --- now sure if that will be a problem (hopefully not).

Any help will be greatly appreciated

Thanks

 

[timofred]

Is it 414 or 411 ?
The 411 will need a much bigger cab
5 1/2 - 8 cubic feet
Please don't judge that driver as bad, if using a small cab.

 

[EarlK]

Your component collection equates to the ancient Avalon ( 837A or 837B ).

You also mention that you have 806a drivers > yet state that they are 8 ohms . Why is that ??
( FYI, the dcr of the 806a's original 20275 diaphragms will be about 8 ohms > but that value is not to be confused with the actual impedance of the driver ).
- Maybe you bought ( # 34647 ) replacement diaphragms from GPA ?

No matter really, the original network for the Avalon was the N800F which is simple enough to build up for a listen ( as a first pass ).
- Swap out the original attenuation setup for an 8 ohm variable Lpad that's preceeded ( amp side ) by a 2 to 4 ohm inline resistor to present an approximate 10 to 12 ohm HF load ( assuming you still have the original 20275 diaphragms ) .



An older thread at LHF

Another good thread to read called Yet Another Altec 2-Way

 

[twiiii]

I had Altec Carmels using two 414's and n 811 with a 16 ohm 800 HZ crossover. I changed to an 802 for better highs nd greater efficency which meant I didn't need as much power for the horn and could turn down the crossover HF output a bit more. Ported correctly you should easily reach 45 HZ flat. not -10 db but -3 db. They will need to be placed against a wall. For even more bass move them closer and closer to a corner. You will get more bass but it won't go any lower. I use yo get down to 40 HZ with a 4.5 cu ft box at -3 db with either a 414 with a 32B horn or a 617-8a Altec 12" coax.

 

[Dr. Beaker]

For an easy and excellent sounding crossover, I suggest reading up on the JE Labs experiments with running the woofer full range.

https://jelabs.blogspot.com/2018/01/altec-2-way-xo-redux.html

The Z19 crossover will do very nicely with those components also, with appropriate modifications for the 16 ohm woofer. That's a nominal 1200 Hz crossover design.

Great discussion thread on HiFi Haven you may want to read up on, but it's long.

https://hifihaven.org/index.php?threads/altec-2-way-build-ala-jelabs-802-32-414.3452/

 

[twiiii]

Unless the driver acoustic c3enter and the acoustic center of the horn re in perfect alignment the last thing you want is two different sources, the woofer and horn covering the same frequencies. You will get real dips and peaks in the very important midrange where the ear is most sensitive.

 

[larbor]

Is it 414 or 411 ?
The 411 will need a much bigger cab
5 1/2 - 8 cubic feet
Please don't judge that driver as bad, if using a small cab.

It's a 414a -- 12 in hopefully my cab can do for now

 

[larbor]

Thanks,

I tested the horns and the ohms readout was around 6-7, where the woofers were around 12 ohms. I assumed the horns were 8 ohms and the woofers was 16 ohms.

Looking at the Z19 crossover now, need to research what to change for 16 ohms

Hi twiiii... not sure what you mean be alignment --- is that actual alignment of the speaker and the horn..(same plane).

This x-SIM software is pretty neat but not sure how to get the frequency files. I found software that could trace the frequency graph but I could not find a good graph for the 811/414s (pdf)

Thanks again.