1971 Magnavox Console - MTM? Dispersion?

[Fourthlaw]

Well one option is a high power DC supply and to use car amplifiers with built in active crossover functions depending on what your really after, or car amps with graphic EQ can also be useful. Its a useful approach for jukeboxes or games cabinets with lots of different drivers.

I already have some spare behringer crossovers and an RTA/PA system sitting around, so I'm going to try to use what's at hand.

I'm certain the polystyrene sections are not original and probably don't help.

Strangely enough, if not original, then they constitute an immediate after-market modification. When I took off the rear panel, the Styrofoam pieces seemed contemporary to the rest of the innards.

Side firing bass units and forward horns are not a bad idea in principle. Are the horns still working properly ?

As good as ever...hard to say with the 40 year old capacitors.

http://www.diyaudio.com/forums/multi-way/207530-vintage-style-stereo-console-design.html

Is a thread where I discuss a miles better alternative to an MTM,
and probably the best quality alternative of all your likely to find,
for a room filling wide dispersion sound at seated ear height.
T/M/B on the front, 0.5 B on the side, well braced boxes.

rgds, sreten.

Took a look through, very interesting. I think I can officially take MTM off the table. Right now, I'm circling a two or three-way system with a sub.

 

[Fourthlaw]

I'd rather you would buy my full range Karlsons and a pair of tweeters from me

I know it, but that may be a touch nuanced for this particular exercise in absurdity.

...the Seas coax with helper subs sound better, and have wider dispersion and frequency range.

Check. Got 'em down on my crib sheet.

Getting the crossover right is what really makes a difference between "so-so" and great sounding speakers, if you don't plan on going active or getting a measurement set up it is best to go with a proven design like the one I suggested.

My thought is to go with an RTA/EQ/Xover, take the out-of-the-box settings and then start to fiddle. Where to begin trying to simulate this crazy thing. At that point, I can switch to passive but probably won't. I just want to retain the flexibility to adjust the system to the room as needed--I get the feeling this thing will get moved a lot. So, ultimately, the back may sport a built-in behringer dcx or something.

 

[Fourthlaw]

BTW, since a few comments have covered the horns. The original horns are wide, but mounted vertically. I presume that is to try to mitigate the positioning so near the floor.

 

[weltersys]

Hi,

Fair enough. Just wondering about the "muffled" sound.

I've heard some dreadful old valve stuff, but if you can forget about
real bass and treble, imaging and high output, also some nice stuff.

rgds, sreten.

The Heppners top out about 10,000 Hz, after a pronounced midrange peak.
The side firing woofers had no crossover at all, IIRC.

I think the Magnovox consoles were built in regional shops, there are differences in construction and the components used, my parents unit had no styrofoam for instance, but did have perf board on the back. It was a "new fangled" 1960's solid state unit, not tube (valve), and unlike tube gear, sounded absolutely horrific when driven in to clipping, which was about "5" on the knob that went to 10.

Art

 

[sreten]

Hi,

Still think the 3 way I suggested tuned low with no sub, is the way to go.

And a correction, there is no 0.5 way bass unit, still a vertical T/M/B
on the front and a side mounted B would still work well. Biamping
Bass and Mid/Treble is feasible losing more x/o components :
(the bass components, series C and impedance stuff for the mid).

rgds, sreten.

 

[weltersys]

BTW, since a few comments have covered the horns. The original horns are wide, but mounted vertically. I presume that is to try to mitigate the positioning so near the floor.

Good for that "floor bounce" we love.
The Heppner is so narrow it acts like a diffraction horn in most of it's range, vertical probably makes as much (or little) sense as horizontal.

The Magnovox consoles had about as much design integration as ordering from the dollar menu at MacDonalds .

They did hide all the junk inside nicely though, and provided a place to show flowerpots and knick-knacks.

 

[sreten]

BTW, since a few comments have covered the horns. The original horns are wide, but
mounted vertically. I presume that is to try to mitigate the positioning so near the floor.

Hi,

Yes it will to an extent, but also make horizontal dispersion very finicky.

rgds, sreten.

 

[Fourthlaw]

That cavity looks suspicious to me. It could induce all kinds of artifacts in the sound.

I've moved away from this setup based on everyone's input, but I realized that from the image, it may not be easy to see what I was attempting. I had "guides" from the edge of the driver to the edge of the opening. Adding complexity in where it isn't needed.

An externally hosted image should be here but it was not working when we last tested it.

 

[Fourthlaw]

Hi,

Still think the 3 way I suggested tuned low with no sub, is the way to go.

And a correction, there is no 0.5 way bass unit, still a vertical T/M/B
on the front and a side mounted B would still work well. Biamping
Bass and Mid/Treble is feasible losing more x/o components :
(the bass components, series C and impedance stuff for the mid).

rgds, sreten.

So, two bass drivers per channel? One side-firing and one front-firing? What sizes did you have in mind? 1/4/8/8?

 

[Fourthlaw]

Here is a three-way concept. It uses a 12" on the end, a 6" mid, and a wide-dispersion horn mounted on a piano hinge affair to allow for aiming. Actually, with no sub in the middle, I'm not sure I need the inside wall on the right.

An externally hosted image should be here but it was not working when we last tested it.

In spite of my in-born tendency to over-engineer, I can't imagine that I will get the value out of top drivers in this beast. And by cutting back on driver cost, I can spend more on a dac, cross-overs, and--dare I say--a large *touchscreen*.

 

[sreten]

So, two bass drivers per channel? One side-firing and
one front-firing? What sizes did you have in mind? 1/4/8/8?

Hi,

I'm suggesting a very specific design for all the reasons described in the
linked to thread, but to summarise, to modify a centre channel design :

The design is 3/4"dome/2"dome/2x6.5" 3 way (Zaphs ZD3C).

Optimum axis is designed to be 12" above the tweeter level.

40L (33Hz tuning) to 60L (30Hz tuning) per side should give
subwoofer territory bass extension (but room interactions
and placement issues mean I can't guarantee the bass end).

The design could be actively bi-amped, with passive mid/treble.
(In fact PLLXO - passive line level x/o's, wouldn't be too hard).

Mid and treble levels are easily (subtelty) adjustable by means
of series resistors, relatively in the case you are bi-amping.

rgds, sreten.