Altec 511B horn compared to the GPA MR931

**VolvoHeretic** · August 14th, 2012, 11:00 AM

Originally Posted by fpitas

I run them toed-in to a spot about a foot in front of my listening position...

What, you use a laser sight to aim them?

**fpitas** · August 14th, 2012, 11:04 AM

Originally Posted by VolvoHeretic

What, you use a laser sight to aim them?

Nope, just sight them by eye. It's not real crucial as long as the apex is a little in front of the listener.

**cradeldorf** · August 14th, 2012, 03:47 PM

Originally Posted by fpitas

Nope, just sight them by eye. It's not real crucial as long as the apex is a little in front of the listener.

I stand against my speakers facing towards the listening position keeping myself square with the cabinet and aim my head straight and adjust the cabinet until I'm staring straight at the listening position.

**Panomaniac** · August 14th, 2012, 06:30 PM

Originally Posted by VolvoHeretic

What, you use a laser sight to aim them?

Believe it or not, I've done that. Green laser, in case you were wondering.

**Alien_Shore** · August 14th, 2012, 09:44 PM

I did some measurements tonight, since my test rig happens to be set up right now.

I took a 902 and measured from 1 meter, on-axis. Comparisons of MR931 (Blue), 811 (Red), and 511 (Grn).

54816258254 891bdba280 b

The reason for the lower response from 0 to 120Hz on the 511 is the attic fan turned off (which was running during the other two tests and contributes some LF rumble).
If I am feeling motivated this evening, I'll take some off-axis measurements...

**Alien_Shore** · August 15th, 2012, 12:29 AM

Here are the off-axis (45 degree) comparisons MR934 (Blue), 811 (Grn), 511 (Red):

GM · August 15th, 2012, 12:45 AM

Originally Posted by Alien_Shore

I took a 902 and measured from 1 meter, on-axis. Comparisons of MR931, 811, and 511.

Thanks, once again proof of what me and others say about the 902, 908 needing an 800 Hz or higher XO point for best overall performance.

GM

**aditya** · August 15th, 2012, 01:20 AM

Many thanks Allen_Shore for the graphs. These will be very helpful as references.

**theophile** · August 17th, 2012, 10:00 PM

I found Allen's graphs interesting mainly because of the contrast between them and the ones done by Zilch and posted at AudioKarma. Zilch's graphs showed the Altec horns to have a frequency response like a rollercoaster and rolling off at around 7KHz, being around 10dB down at 10KHz.

Allen's graphs are quite different.