Altec 511B horn compared to the GPA MR931

GM · September 5th, 2012, 11:01 AM

Actually, it looks like the driver didn't have a good seal on either horn since neither load down to ~1200 Hz more than the little 931. That, or the driver 'died'.

GM

**Panomaniac** · September 5th, 2012, 02:13 PM

Good call, GM. The graphs don't look anything like what I've measured - but I don't have a 902.

GM · September 5th, 2012, 04:24 PM

Here's one:

902 on a 511 - 1.5 m on axis.jpg

GM

**Alien_Shore** · September 5th, 2012, 10:48 PM

Thanks for the analysis and comments. This evening, I tested the same three horns on a brand new B&C DE250:
MR931 (Blue), 811 (Red), 511 (Grn)

54816073606 83591bc94c z

I made sure to have the driver good and snug on the horn. I did notice that using the highpass settings in Holm were creating some weird issues (causing severe rolloff at 6k), so I turned that off and things returned to normal. It is odd that the 511b creates that spike at 950 in opposition to droop there for the other two horns. What would cause that? (perhaps the ringing? I'll try that horn again with some dampening on it and verify...)

**Alien_Shore** · September 6th, 2012, 11:06 PM

Veellllyy intelllessstink!
I dampened the 511b with sand bags and some foam pipe insulation:
Using the DE250 again with MR931 (Blue), 811 (Red), 511 (Grn)

54816074141 fdb144a2c5 z

Now the resonance of the 811b is standing out. Cool! I'm learning a lot here as I go.

**Panomaniac** · September 7th, 2012, 04:24 PM

Nice work, thanks. The 811 looks very nice, except for the little dip circa 1900Hz.
I may ask you for the HOLM zip file, for a closer look.

**Earl K** · March 15th, 2017, 09:27 AM

Mike ( Alien_Shore ),

Your ancient picture links are broken.

Any chance of restoring them ( or re-posting the latest measurements )

Thanks <> EarlK

**Earl K** · March 14th, 2025, 01:39 PM

Ha!

Eight years and still waiting on a response from Mike ( I'm not really that pushy, ya-know?? )

**Altec Best** · July 26th, 2025, 08:48 PM

Originally Posted by Earl K

Ha!

Eight years and still waiting on a response from Mike ( I'm not really that pushy, ya-know?? )

Earl he may have gotten lost on the way home !

**Alien_Shore** · September 27th, 2025, 06:35 PM

Originally Posted by Earl K

Mike ( Alien_Shore ),

Your ancient picture links are broken.

Any chance of restoring them ( or re-posting the latest measurements )

Thanks <> EarlK

Originally Posted by Earl K

Ha!

Eight years and still waiting on a response from Mike ( I'm not really that pushy, ya-know?? )

Originally Posted by Altec Best

Earl he may have gotten lost on the way home !

Well, my posts are ancient, now I'M ANCIENT, but hey, I got the pics working again.