Altec Lansing A8 – Revoicing the VOTT
Now that the A8’s have settled into their new home, the new Great Plains Audio 909-16 drivers have hundreds of hours on them, and their new partner, the Toolshed Amps Euphoria Stereo 45 amp is tethered to them, there’s just one thing left to do. Crossover rebuild.
The stock (40+ year old) crossovers (N800F) sound really nice. Frankly, I was surprised considering the condition of the stock high freq drivers when I brought them home. It wasn’t pretty. In contrast, the inside of the box, and the low freq drivers were in prime condition. Mind you, the Altec networks are sealed in a metal enclosure, so it’s unlikely the elements would threaten their safety. That said, I think these drivers need an upgraded N800F clone to elevate them a bit more. So, I built brand new networks with some nice components I’ve had success with on other projects.
There are hundreds of threads on the Lansing Heritage forum and Altec Users boards, but neither site has robust search functions. Or, I just couldn’t figure them out. I did get some help – the forum groups were great. I just didn’t want to sift through thousands of posts, so, I ran with what I had. It was difficult to find anything outside the schematics and lots of opinion around topics peripheral to my quest. So, for new builders like myself, I’ll try to be more thorough here.
I’m not certain, but in my reading I found that there may be more than one version of the N800F. Unclear. I’ve got Altec A8’s from the late 70’s with plastic 32b(c?) horns, 909-16 high frequency drivers from Great Plains Audio, and the original 416-16C 16ohm low frequency drivers with ferrite magnets, and, the network boxes stamped N800F. So, I went ahead and built new from this schematic.
I had to learn how to read a schematic – which was cool – and, I found some good resources online. I did require some additional direction. Matt Formanek of Toolshed Amps was gracious enough to help fill the gaps in my knowledge. Ultimately, I found I had over-complicated things, and a two way crossover like this one is a simple thing. For each speaker, we have two inductors, two capacitors, one resistor and one variable resistor for padding the mid-range driver. I did add a terminal strip for binding the outputs to the drivers. And, I bought some nice new speaker binding posts to replace the stock pairs. You’ll see four caps in my photos because I was running them in parallel to reach the rating I needed.
After testing, I chose to solder everything together, with as few parts as possible. Simple is better. I used boards roughly 7″x14″, which were bigger than I needed, but at some point I may want to experiment with different and larger parts.
I’d used all the capacitor brands before, except the Arizona’s. I’ve combined a .47uf green with the 10uf Obbligato for the low frequency signal path. The inductors are Jantzen 3.5 mh air cores – new to me. Inductors can get expensive, so I opted for 18awg. I wanted to go large, but maybe we can experiment more with those down the road. I’ve also got a 25ohm Clarostat resistor for the lpad, and a Duelund 20ohm resistor. I’m using some Duelund tinned copper 16ga wire for all internal wiring.
They’ve been running a couple days now, and are starting to open up. It’s sounds fantastic. My goal is to take advantage of these drivers sensitivity and get as much texture, nuance and tone as I can out of my Euphoria Stereo 45.
I will follow up later on listening impressions.
Thanks for listening.