Altec MR64

[jkc]

Altec MR 64A


I acquired these horns as part of my collection and cobbled this setup together to give them a go.

Seen here they have 288-16K compression drivers and are sitting on a 2220 with 2242 for subs and slots on top.


The horns sound great, very open and detailed.


When I first installed them they were pointing down a little and exhibited a very strange effect of making the piano float up on the ceiling and one had the feeling of wanting to reach up and pull it down, most strange.



I was going to try them with the 2220’s in some 4560 horns and set them up in my garage just for fun.

[pelly3s]

thats a really large cabinet. That looks like an altec from the Telex days. They made some good horns then. i have 2220's and I think they may end up in a pair of VOTT boxes sometime soon

[jkc]

When it comes to horns size does matter.



As far as I can figure the 2220 isn’t very happy in an A7 but should work in the Altec 816 cabinet.



Apparently JBL originally recommended the 2220 for the 4560 but people started demanding more bass and suggested other drivers i.e. E140 2205

JBL allude to this in their brochure were they mention a loss of midrange sensitivity with other drivers in the 4560.

[Earl K]

Hi jkc


When it comes to horns size does matter.

- ( among other things , I'm wondering what your crossover points are ? )

- How low have you taken those large planar surface, MR64s before they unload ?

:)

[jkc]

When I cobbled this together I stuck to Altecs recommendations for the 288’s and crossed over to the 2220’s at 700Hz.

It is not just unloading the horns but driver resonance is down there somewhere to.

Altec state the lowest usable frequency for the horns is 500Hz.


The 2220’s cross over at 150Hz as they are in a small 1 cubic foot boxes and have no LF output.

They really should have asymmetrical filters on them where they cross to the subs.


I was going to try crossing over the horns at 500 Hz which may be OK with 24dB/octave filters but I have to build the boards as my home made active crossovers (Burr Brown Op Amps with Polypropylene Capacitors) are fixed frequencies and arranged as individual boards, I find it easier to have a selection of boards to swap out as required.

1 KHz is on the list to try as well.


The bottom end of these is not right and as it stands would be better off with a single driver, say a pair of 2235’s, but I wanted to check out the 2220’s as well.

The 2242’s don’t seem happy crossing over at 150Hz either a little high for them I thought.

There is a problem with the crossover between the 2220’s and the horns, which I put down to a combination of time delay and the difference in dispersion patterns the horns being 60 x 40 degrees.

They are also very efficient and the slots don’t keep up.


Having said all that the horns sound very good indeed, I compared them to a friend's Magna planers and thought the Maggie’s sounded very muffled in fact it was so noticeable that I had to go listen to another pair which gave the same impression.


Hence the decision to set them up with some 2220’s in some 4560 cabinets as it should help fix the dispersion problems and time alignment.

I though to try some 2241’s tuned to 31Hz with the same 150Hz crossover for the Subs.


I am just plain curious to try out a horn loaded system with sensitivity well up over 100dB and this is what came to hand.

[pocketchange]

Here's another idea for consideration.
The above with Klipsch drivers (because that's just the way it is).
Mr. Crites A series XO's and tweeter's.
I'm wondering if things could be improved with a change to the 288-16K in place of the K55 (Atlas PD-5VH) Mid, leaving the balance of the system in place, unless it needed something else.
Food for thought, :blink: pc

[allen mueller]

The 2242’s don’t seem happy crossing over at 150Hz either a little high for them I thought.

Interesting, I have a pair of vs3218's that use the 2242 all the way up to 250Hz . I am not sure of the tuning of the cabinet but I am very happy with the sound. Here is a link to the thread where i posted a picture.

http://www.audioheritage.org/vbulletin/showthread.php?t=15265