My turn...A7 restore...

[GM]

..........so I was going to start with 1 longer 3" dia and adjust the length to see how it goes.

Don't be surprised if you get weird readings since in theory a 3" pipe is much too small to tune such a large cab to any usable Fb, i.e. better to just seal it up.

GM

[analog addict]

Well, it's only been a month, but I finally got over the hump of dealing with cutting out some reinforcement for the bases, which were getting a little soft. Cut some 1/4" plywood to size and slid it into the base between the rails along the sides....



Finally.....











Starting to look like speakers now. Also went through the 501s with some deoxit and fader lube. They look unmolested with the original pair of red tipped electrolytic 28uF caps in each. I will definitely be upgrading the X-overs, hopefully with help from Dennis Had. But as a starting point, is there a schematic floating around for any existing upgrade?

[bowtie427ss]

But as a starting point, is there a schematic floating around for any existing upgrade?

Remember A, you're dealing with well engineered drivers and cabinet system. A straight 2nd order network is much closer to ideal with an A7 system than most speaker systems.

That said, for non duplex XO upgrade i'd be searching out the work of Jean Hiraga. But, i'm not sure how much he experimented with a stock 825/828 cabinet based system, i'd still look into his work though. I've heard an Onken based 2-way system with Hiraga designed networks and they were the stuff envy is made of.

[Panomaniac]

The crossover that came with my A7s was bloody awful. Nicely built, but very ill suited for any Hi-Fi or home use. All midrange shout. Just under-lapping the crossover points would help a lot, but a well designed crossover can do wonders for the same drivers, horns and cabinet.

Agreed. Mr. Hiraga can do crossovers like few others. I was privileged to hear quite a few of his. Wish I had known more about x-over design at the time and learned more from him.

[analog addict]

The crossover that came with my A7s was bloody awful. Nicely built, but very ill suited for any Hi-Fi or home use. All midrange shout. Just under-lapping the crossover points would help a lot, but a well designed crossover can do wonders for the same drivers, horns and cabinet.

Agreed. Mr. Hiraga can do crossovers like few others. I was privileged to hear quite a few of his. Wish I had known more about x-over design at the time and learned more from him.

Well I have them up and running and Pano was right. The midrange shout is immediately noticeable. However, I detect the glimmers of a nice set of speakers in there somewhere. I'll need to spiffy up the boxes the 511s are in too.






Here are Hiraga's A5 crossovers. Should I look to leave the HF portion the same since at least at this point I'm running 802s on the 511?

http://web.archive.org/web/200502060...s/HiragaA5.pdf

[Panomaniac]

Hiraga's crossover was for the A5 we built together, not the A7. We used a 1505 horn and a Westrex driver that is similar to the Altec 288. FWIW, I could not get the this published crossover to sound worth a damn with my 416s, 1005s and 288s. I tried and tired. I've been searching for notes on were I ended up with the 511s and the 1" drivers, but can't find them. If I can't find or remember the crossover points that worked, I'll try again.

FWIW, you need to close up those ports to about 1/2 the size you have now. That will help extend the bass.

[cradeldorf]

I'd shrink the port down to more like 2 inches high for full length, I'd do it along the bottom too. Just my .02. Not that I know anything.

[GM]

What XO do you have? Regardless, the horn must be shelved since it's ~5-7 dB 'hotter' than the mid-bass. Once shelved, the extreme HF will be MIA, so a by-pass cap around the autoformer or pot is required to let some portion of it through unattenuated. Basically, what you want is CD horn EQ.

Some folks dispense with a proper XO in a HIFI app, letting the mid-woofer run full-range and just use a matching impedance series resistor to shelve the horn and wire the by-pass cap around it.

GM

[analog addict]

Right now it's just a set of stock N501s, mainly since I wanted to hear what these things sound like out of the box. But I can tell you I'm not going to listen to them like this much. In fact I've prolly already heard enuff.

I have an active crossover around here somewhere given to me by Tom Brennan over on the AK forums. I've been saving it for just such a purpose. I have to figger out how to set it up, but assuming I can do so, anyone want to suggest some good starting crossover points?

[GM]

So I take it you haven't tried tonally balancing [level matching/attenuating] the horn through the XO BW to get rid of its 'shout' [and normally much of its HF also as a consequence]?

GM