How does the above horn sound when used in a high quality audio home system.
Any preference ?
Driver will be a GPA 902.
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How does the above horn sound when used in a high quality audio home system.
Any preference ?
Driver will be a GPA 902.
Don't have 511's anymore, and have not had the MR931, but casually speaking I prefer CD horns.
I'd expect distance to the listening position to be a factor in your decision.
CD versus non-CD horns is often down to personal preference. Most audiophiles prefer non-CD these days, such as the tractrix or JMLC horns, which have a collapsing directivity with frequency. CD is preferred for PA use where you need to broadcast sound more or less evenly to the crowd in a club, but if you sit in a specific spot for listening, CD is not necessarily a good thing; all that power broadcast in other directions simply creates more reflected sound. CD horns in particular usually use a diffraction slot in some form, which can affect the sound by creating an internal reflection. That leads to ripples in the frequency response, which can be EQed out, but the reflections within the horn will emerge later than the direct sound causing time smearing. Still, it's a matter of taste, and some people are OK with that, and think it's a good trade-off for the better dispersion. Of course, if you want CD without using a diffraction slot, a waveguide is a good answer, since they don't have the constraints of a true horn.
I should add that I have 511s and am happy with them. I run them toed-in to a spot about a foot in front of my listening position, which helps the imaging. Used that way the limited dispersion over 10kHz isn't a big issue.
What, you use a laser sight to aim them? :)Quote:
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.Quote:
Originally Posted by VolvoHeretic
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.Quote:
Originally Posted by fpitas
Believe it or not, I've done that. Green laser, in case you were wondering. :DQuote:
Originally Posted by VolvoHeretic
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).
https://live.staticflickr.com/65535/...1bdba280_b.jpg
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...
Here are the off-axis (45 degree) comparisons MR934 (Blue), 811 (Grn), 511 (Red):
https://www.hostboard.com/forums/hbm.../2012/08/1.jpg
Yeah, a good rule-of-thumb for most rising on axis horns is to aim the left one to the far right LP and vice versa and if it's a solo seat, then at least 2 ft offset on each side.Quote:
Originally Posted by fpitas
GM
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.Quote:
Originally Posted by Alien_Shore
GM
Many thanks Allen_Shore for the graphs. These will be very helpful as references.
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.
Weren't they of the 806, which indeed is a much poorer performing driver compared to the 802, 902 series?
GM
GM, you are indeed correct about the ones which were rolling off at 7KHz.Quote:
Originally Posted by GM
Zilch did some graphs of the 811/902 which indeed showed more extended response than the 806, but they were much more uneven than the ones measured by Allen.
Don't recall those nor the resolution they were measured at, which can make them look somewhat different, not to mention driver condition, especially the AlNiCo ones.
GM
Why would you measure below 300hz? Seems like it would be easy to damage them.Quote:
Originally Posted by Alien_Shore
Can you detail your test setup for us?
And, because I'm lazy, what is the MR931? The little guy used on the model 14?
Edit: I went and looked...I never did like those.
I have a pair of MR994 that I like quite well but have never really built into a system for critical evaluation. Small format 500hz, they are huge!
Ron
Quote:
Originally Posted by theophile
Bear in mind lots of different Altec frams, even in aluminum, and as GM said, Zilch did 806's. A big thanks to zilch BTW for all he's done.
Thanks for the plots, very nice reference. :Thumbs up:
As a long time user of HOLMImpulse here are some tips to give you cleaner results:
- Keep the volume up. It looks like you are not running these very loud, at least not compared to the noise floor. You want a good S/N ratio.
- Use the high pass filter. If you look down just to the left of the impulse window, you'll see High Pass and Low Pass filters. For horns and drivers, a 200Hz HP is a good idea. No low frequencies going into the driver and HOLM won't pick up junk down there
- You can start your sweep at 100Hz or higher. That's in the first tab. It's handy, but the high pass filter is the real tool you need.
I'm a little surprised to see how similar at least two of plots are. That's encouraging.
Here's a more critical vertical scaling ( of Alien's measurement ) to compare to Zilch(s) work ;
http://www.hostboard.com/forums/hbmc.../2012/08/1.png
- Zilch ( in his time ) measured a few Altec 802s & 902s on both 811s & 511s .
- He also started to keep track of diaphragm models when it became apparent that various combos of diaphragm/phase-plugs made a difference ( & if he didn't, then I did ) .
- Gallery
http://www.hostboard.com/forums/hbmc.../2012/08/2.png
http://www.hostboard.com/forums/hbmc.../2012/03/2.png
http://www.hostboard.com/forums/hbmc.../2012/08/3.png
http://www.hostboard.com/forums/hbmc...2012/08/34.jpg
http://www.hostboard.com/forums/hbmc.../2010/12/1.png
And the ( 9-slit radial ) GPA version of the 802G ( not EQed ) .
http://www.hostboard.com/forums/hbmc.../2012/08/4.png
:)
Bear in mind, I'm an utter noob with measuring, but I really am interested in getting better and putting up some more quantitative info about Altec gear (I'm inspired by the work of Zilch, Earl, Vin, and others here). Taking some advice I've received, I did a full-sweep with low SPL to avoid any damage.Quote:
Originally Posted by RonSSS
My test setup is pretty simple:
ECM-8000 $55
Blue Icicle USB preamp $40
Creative Labs SB1095 X-fi Pro USB external sound card $60 (this has a highly rated DAC for the money and doubles as a great replacement for my crappy laptop integrated sound)
Old laptop w/ windows XP
Mic Stand $20
XLR Mic cable $4
Holm Impulse Free
Mic and pre-amp calibration by CSL $75 (includes off-axis and polar response measurements)
I did the measurements with no filters inline whatsoever, just the test rig hooked up to an old Onkyo SS amp and straight to the 902.
Thanks Pano - I'll use your tips to rework a couple of the measurements. The pre-amp I'm currently using is pretty much useless below 100Hz anyway. I welcome and appreciate any other tips - I have done a ton of reading, but again, pretty new at this. I had used the filters in Holm on an earlier set of measurements on my M14s, and will try that again. It's probably best to also use a series cap to protect the driver if I up the SPL. I probably won't pull the 511 down from the garage - it's a heavy bugger to carry up there to my man cave :)Quote:
Originally Posted by Panomaniac
Earl - thanks for posting those graphs and the link to your gallery - there's some great info in there I've not seen yet. I will definitely be looking through that in some detail.
Edit: Here's an updated measurement. This is from the same driver; OEM 902 (PN 34635), manufactured in May 1980, with the original diaphragm (PN 34647). For these two measurements, I adjusted the sweep range to start at 100 Hz, added a Hi-Pass electronic filter (200 Hz) in Holm, and added a 49uF cap in series. I cranked up the SPL considerably and plotted the graph using 2dB amplitude scale.
https://live.staticflickr.com/65535/...261aed96_z.jpg
Good work Mike. This is how we learn!
Too bad you don't have a 511 and a MR994 to throw that driver on.
Ron
That addition to your last post is interesting.
It shows me why Altec crossed the 416 over at 1200Hz in the Model 19. It also shows me why I cant put a 902 into my Valencia at the 800Hz crossover point.
I'm confused. The 902 does fine at 800hz on the 811 horn. Scale is 2dB/div. It doesn't look so hot at 800hz on the MR931, but that is a 1500hz horn.
There is no data here for an 802. So ?????
Ron
Quote:
Originally Posted by theophile
Well to my eye, on that graph the response at 800Hz is 5dB down from approx 1200Hz on the 811. If I was using a 902(which I have the GPA version of), I wouldn't put it on the Valencia using the 811 and the conventional Valencia 800Hz XO point. With an active crossover (like I use) it is a simple matter of adjusting the XO point and getting the output levels to blend with the 416Z. I wouldn't cross over at 800, given what I see in that graph. I'd be more inclined to use the 1200Hz crossover point that the Model 19 used.
Does that explain my statement, to you? That's my reasoning anywho.
If an 802/6 were measured and on the same graph and showed 5dB better at those frequencies, then yes, I would agree.
I suspect however that an 802/6 would look quite similar.
Remember that the model 19 used both 902 and 802 drivers depending on the year produced.
I think Altec switched to 1200 hz to keep the frams from blowing up. I may be wrong.
Ron
QUOTE=theophile;1841402]Well to my eye, on that graph the response at 800Hz is 5dB down from approx 1200Hz on the 811. If I was using a 902(which I have the GPA version of), I wouldn't put it on the Valencia using the 811 and the conventional Valencia 800Hz XO point. With an active crossover (like I use) it is a simple matter of adjusting the XO point and getting the output levels to blend with the 416Z. I wouldn't cross over at 800, given what I see in that graph. I'd be more inclined to use the 1200Hz crossover point that the Model 19 used.
Does that explain my statement, to you? That's my reasoning anywho.[/QUOTE]
Frams blowing weren't so much an issue in HiFi. Live, yes. The 902 is a lighter driver, so is gonna resonate. I am speaking of the driver body, at lower freqs. The lower you cross any small Altecs, the less loudly you can play them. The heavier 802 does better than 806 and 900's. At 500 I REALLY suggest large format.
Or use dual 802s which yields more performance overall at less cost.
GM
I went by my storage shed and grabbed a 511b - ran a few more tests. These are all using the same 902 driver, on-axis, at 1m. Compares MR931 (blue), 811b (green), and 511b (red):
https://live.staticflickr.com/65535/...76799372_z.jpg
Thanks for the graph. Kinda unexpected. I'd have guessed the plots for the 511 & 811 the other way, Hmmm....
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
Good call, GM. The graphs don't look anything like what I've measured - but I don't have a 902.
Here's one:
Attachment 1528
GM
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)
https://live.staticflickr.com/65535/...591bc94c_z.jpg
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...)
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)
https://live.staticflickr.com/65535/...b144a2c5_z.jpg
Now the resonance of the 811b is standing out. Cool! I'm learning a lot here as I go. :)
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.
Mike ( Alien_Shore ),
Your ancient picture links are broken.
Any chance of restoring them ( or re-posting the latest measurements )
Thanks <> EarlK
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 ! :biggrin2:Quote:
Originally Posted by Earl K
Quote:
Originally Posted by Earl K
Quote:
Originally Posted by Earl K
Well, my posts are ancient, now I'M ANCIENT, but hey, I got the pics working again. ;)Quote:
Originally Posted by Altec Best
