Anybody that has been following my antics with my HeathKit AS101's knows that I'm on an upgrade path to make them sound the best that they can.
Yesterday I installed my 902 drivers with new aluminum diaphragms from GPA along with the adapters I made to go from 7/8" throat to the 1" inlet 811b horn. After installing them I found the midrange to be very hot but I could hear potential in the sound quality.
A few months back I found a set of 30904 attenuators on ebay for cheap. So today I grabbed my friend that got me into this whole Altec mess and we got to work on them. Before I did anything I let him play some music and he agreed that they needed a bit of work.
So we opened the speakers back up and installed the attenuators. Right away we could hear the difference, much smoother with no peaky midrange, overall very very nice. I could live with these just as they are now, they have never sounded better.
I remembered that I had a CD with a very slow frequency sweep so I played that. I've played this before in the past while they were fairly new to me and found that the higher midrange was very bright, so much so that I would turn the volume down so I wouldn't damage the diaphragms. I could hear the dips and peaks in the volume as the frequency increased. After today's modifications there were no noticeable dips or peaks till my hearing gave out.
My friend Dave is 28 years old and has always taken good care of his ears. As we played the sweeps I looked at him and when it became silent I said "I'm Out". He could hear it to 20KHz and tell me it stopped. Said it dropped off somewhat at the higher end but was nice and smooth.
We continued playing music for quite some time and chatted about Altec stuff. We spent a little time checking out the 291-16K drivers that I picked up, he was surprised at the great condition that they were in. Thanks to elitopus1 on the board, I have a set of Symbiotik diaphragms coming in later this week.
When they arrive I'm going to install them and drop by his place for some Altec fun. He has a huge set of EV fiberglass horns, about 3 foot across that will fit up to the Altec drivers. Also has a set of large JBL 15" bass bins. I dropped him off with a Rane crossover to check out, it was intermittent and I fixed a few cracked solder joints on the board. So next weekend if he is up to it we should be cranking out some tunes large format style. Should be fun.

BillWojo