Recently came across some very large home made cabinets that contain Altec 803b bass drivers (16 ohms per Altec literature) and 804a high frequency drivers (also 16 ohms per Altec literature) with 811B sectional horns. "Dividing network" in an Altec N-800E. Both speakers rated at 30 watts.
They sound quite good, though I am guessing they'll sound better once crossover caps are replaced (and I get through the "goo" that seals them).
The cabinets are way too big (and ugly) as is. Given these are basically A7 Voice of the Theater components, the cabinets could be much, much bigger.
I need to get these cabinets smaller (or I may have to sell these beauties!), and the closest I can come in an approximate "stock" cabinet was the Altec Valencia, though I'm not sure the Valencia cabinet typically used the same driver I have.
Goal is either a cabinet that contains both drivers, or a cabinet for bass only with horns mounted externally on the top, but absolute minimum make sense size.
I can find loads of calculators on line for enclosures calculating with Thiele Small parameters, to yield cabinet size in cubic feet and port size, etc, but I am clueless as to how to discern these parameters for this ancient bass speaker. I do NOT want a cabinet that gives me "subwoofer thump" (Dave Brubeck, Diana Krall, Eric Clapton, et all, do not require subwoofers, nor do Brian Eno or Mahler, but they can all appreciate a decent bottom end.)
Any guidance as to cabinet size in cubic feet, port diameters, tubes or not, etc?? Driver specs in photos below.
Thanks!
You could build some valencia clones. Those are basically the same components.
You can go smaller than that if you want but bass will suffer. If you run a sub it will make up for that.
I'm not sure about T/s specs for your 803 drivers but I know the later ones (with cloth spider and surround) have the same specs as the 416a.
Thats what I know about these. Some others will chime in with more cabs options.
Welcome to the forum and good luck with your project
Among others, measured 416A, -8A here: https://web.archive.org/web/20070806055141/http://www.wmeckle.com/ASHLEY/Ashley.htm
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Thanks, I can use 416 parameters for 803 and see how it comes out. Most likely, I will just clone the Valencia.
Acoustically, it's so small that it may need to be either tuned lower or sealed up or somewhere in between ['leaky' sealed], such as 'sticking a sock' in it [damp/stuff the vents].
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
Wish you lived closer - I'd LOVE to have your old cabs, especially the 606!Originally Posted by SanJoseMichael
I've come across some Altec published information that appears inconsistent.
The era of the 803B:
The 1962 publication "Loudspeaker Enclosures, Their Use and Design" includes a chart that suggests a 25 CPS resonant frequency enclosure would, at minimum, require 7 1/2 cubic feet port area of 10 square inches.
The era of the 416-8A:
The 1968 "Loudspeaker Enclosures, Their Use and Design" includes a chart that suggests a 25 CPS resonant frequency enclosure would, at minimum, require 4 1/2 cubic feet port area of 20 square inches.
Assuming the 803B was later renamed the 416-8A, but otherwise remain the same, why the discrepancy?
Charts:
http://s397891146.onlinehome.us/chart1962.jpg
http://s397891146.onlinehome.us/chart1968.jpg
Note that these charts were based on prosound apps and in '62 they were driven by high output impedance amps that raised the driver's effective Qts [lower effective motor strength = bigger box = weaker air mass 'spring'] and by '68 were using very low output impedance amps, so low Qts [strong motor = smaller box = stiffer air mass 'spring'].
Basic vented boxes are Helmholtz resonators if you want to learn more about its vent system design.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
If these Altecs are driven with an amplifier with an 8 ohm output, would that suggest a smaller cabinet is within reason?
I have modern amps with 4 or 8 ohm outputs, and an as-yet unrestored Scott 229 tube amp with 4/8/16 ohm output, plus various Magnavox console amps (6V6).
8 ohms output, which means it has 8 ohms of series resistance = ideally needing a 10x larger cab! Or, it has 8 ohm taps, which just means it's designed for hooking up an 8 ohm speaker?
Big difference!
Do you know the output impedance or damping factor of your amps?
Otherwise all I can say is that you can put them in any size you want, but smaller = increasingly less bass and more mid-bass 'hump', which up to a point can be damped down with fiberglass insulation.
Below this point you begin removing portions of the rear cover to smooth it out and of course will increasingly roll off the mid-bass too.
Once the rear cover's gone, then you start with the largest flat baffle, etc., until there's nothing left but a driver with even part of its lower mids rolled off.
Next up is start with a smaller woofer........
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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