Altec Lansing

[GM]

Originally posted by Cal Weldon
My throat opening is only 7.5".........

Greets!

FWIW, cabs with throat openings narrower than the 8" horn wall width are ideally only used with 800 Hz XOs, so unless you know when yours were made they may pre-date the introduction of the 511 in the mid '50s, especially if it has the added brace at the top of the throat that further reduces the low pass filter's area. By the time Altec began using 800 Hz XOs on the 511 loaded M.I. horn cabs circa '70, the 'bean counters' had long since dropped the option due to the A7-500 ~wiping out A7-8 sales, so for those folks with either a keen ear and/or response measuring equipment, there's some subtle sonic gains to be had by reducing the filter area when 811s are used with the larger throat cab.

Note that this applies only to Altec woofers listed for this cab or similar response mid-bass horn drivers since ones optimized for non-horn apps won't have the strong stepped response in the 500-1 kHz BW that you would be smoothing.

GM

[GM]

Originally posted by jeff mai
The benefits of big midrange horns are more than worth the hassle of interfacing a tweeter above 8kHz.

Greets!

While I agree with, and actively promote, 'BIB' where applicable, to maximize the performance benefits of a 300 Hz compression loaded multi-cell you'll need a much lower HF XO point, especially if the app is multi-channel. Also, ideally you'll need a larger horn unless a really steep XO and/or it's used in a very low power app since even the huge 1803 (http://www.wmeckle.com/BOYD/1803rca1.jpg) is no bigger than it absolutely had to be for acceptable performance in a PA app driven with a ~matching impedance amp and why there's no doubt in my mind this is why all the (relatively few) 1803 loaded cinema installs I saw when they were being dismantled used a 500 Hz XO, though I don't know if these were original or were swapped out when higher power and/or SS amps were installed.

GM

[Geoff H]

Hey Ken,
'78 was a good year. My daughter (now my best mate) was born.
So was 76, for wine.

Geoff.

[jeff mai]

Originally posted by GM
to maximize the performance benefits of a 300 Hz compression loaded multi-cell you'll need a much lower HF XO point, especially if the app is multi-channel.

Only if you don't use EQ. And you'll face that issue with any CD horn even if much smaller.

Also, ideally you'll need a larger horn unless a really steep XO and/or it's used in a very low power app since even the huge 1803 (http://www.wmeckle.com/BOYD/1803rca1.jpg) is no bigger than it absolutely had to be for acceptable performance

What home app isn't very low power? FWIW, I used an active 24db/octave xover at 350-400Hz with my 1803B.

FYI - the RCA cabinet in that photo is one of the ones I owned and used with my 1803s. Boyd drove 1500 miles to Kansas to pick them up from me.

[Cal Weldon]

I have now received my bolt on midranges so I started with this pole mount.

[Cal Weldon]

Cut it, added some set screws.

[Cal Weldon]

Resized the holes, added a cork gasket and mounted it.

[Cal Weldon]

And now I have this.

[Cal Weldon]

and from the front.

[Cal Weldon]

First listening impressions are good. They continue to remind me they are a far field speaker so I'll have to wait till spring before I have a good listen from 50 or 100 feet. (15 - 30 m)

Fun project, used up some spare parts. All in all, very worth it.