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PostPosted: August 14th, 2016, 7:52 am 
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I have an ACO Pacific 7012 mike plus pre-amp and power supply that you can borrow as a reference. Here is a graph of the response:

Tom


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PostPosted: August 14th, 2016, 7:35 pm 
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Quote:
The later Altec horn drivers with those damned plastic phase plugs and compression caps have a rep for sounding like crap when compared to the originals.


Walt, have you ever actually heard a tangerine 802?

I get the sense that the answer is "negatory." I also didn't hear the list of horns other than the 511B that you have intimate experience with.

So, you reject the work of specialist PhDs with empirical data in hand, yet you blindly accept the ravings of random goobers on audio forums, most of whom are passing along untested ravings of other random goobers. H'mm...

I have a realistic view of academic experts, having been through a couple Ivy league Universities and PhD programs at Yale and William and Mary. Truly, much of it is hogwash.

I guess if I am an expert in anything it is the field of social construction of knowledge systems, which I have been applying to audio in public discussion for three decades, with demonstrated utility.

Let me share my framework for approaching such analysis in audio settings , which I will call the "Roberts Ladder of Audio Authority"

When faced with the question "How do we know?" in the general sense, I propose the following ranking of evidentiary sources.

--Extensive and long term, multi-contextual personal experience

--Fleeting and/or single context personal experience

--Reports from friends who I know and trust, taken in light of what I know about their tastes, preferences, and levels of experience

--Reports from people who are specialized in a certain area whose actual standards and understandings I cannot evaluate directly but who seem to know their stuff.

--Reports and opinions from people who are experts in other fields besides the one under discussion. Wait...I might be overrating here. Maybe they belong at the bottom.

--Ravings of random goobers on audio forums

--People passing on ravings of random goobers on audio forums

--2016 presidential candidates on any topic whatsoever

For people trying to find their way through the forest of audio opinion and assertions, I think this may prove to be a useful heuristic.


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PostPosted: August 14th, 2016, 7:48 pm 
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I'm fairly certain that I know less than nothing about anything. Or do I? I don't know anymore..

Roscoe

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I can explain it to you, but I can’t understand it for you.


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PostPosted: August 17th, 2016, 7:25 am 
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J-Rob,

You are right, 511Bs are not designed for home use but they can be adopted with an attenuator network. Altec did adopt the sectoral horns in several models of studio monitors. Here is the frequency response chart of my speakers 9648-8a.

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http://www.lansingheritage.org/html/altec/specs/pro-speakers/9846-8a.htm


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PostPosted: August 17th, 2016, 8:57 am 
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:obscene-drinkingcheers:

Once we break free of the conceptual chains that attempt to standardize subjective preferences, we can happily say that what I like may not be what you like!



Roscoe Primrose wrote:
I'm fairly certain that I know less than nothing about anything. Or do I? I don't know anymore..

Roscoe


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PostPosted: May 29th, 2017, 5:18 pm 
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Joined: July 17th, 2016, 6:24 am
Posts: 1099
Altec A-5 with jean Higara crossover

Subjective impressions Vs response curve (ignore low freq, guy is using horn loaded subwoofer):

Quote:
With the Hiraga crossover circuit and top performing capacitors, the overall sound has a directness, immediacy, timbre, authority, nuance, ease and musicality that engage the listener, and don't let go. Further, these speakers are capable of producing a big sound stage with great width, depth, nuance, localization of instruments and voices and a great sense of space. The Altec Lansing people knew what they were doing.
...
full bodied, rich, directly engaging, punchy, present, immediate,smooth, sweet, musical, articulate, and nuanced, with a big sound stage, pin point localization of instruments, and lots of space. The sound stage lies well behind the loudspeakers.


Attachment:
a7_response_curve.jpg
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Quote:
Looking at the smoothed frequency response plot below, and noticing the shelving of frequencies above the 500 Hz. crossover point, one might suspect that raising the tweeter level about 3 dB would give a better result. It certainly would provide a flatter measurement. However the system sounds best with the tweeter set where it is.


http://www.vtaf.com/id107.html


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PostPosted: August 6th, 2017, 6:43 pm 
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Walt and J-ROB,

Roscoe was able to open the sealed enclosure back cover on my 9846-8A boxes. It was not easy, I would not been able to do it without his help. Thanks Roscoe.

A while ago, you both recommended using felt damper in 802-D compression drivers. Out of the four 802-Ds I have, three came with acoustical loading caps and one with felt damper. I want to try replacing the loading cap with damper. I cannot seem to find them on google. Any ideas where I can get them?

Rob, you wrote:
Quote:
Some pro models came with a black plastic loading cap over the back of the diaphragm, which won't make much difference at HF but will at 500hz. I made back covers with a much larger volume and really didn't think it was worth doing again but it did create a somewhat softer midrange.


What type of sonic characteristics does the loading cap induce?


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PostPosted: August 6th, 2017, 7:04 pm 
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Posts: 570
Anyone using an electronic crossover with the 511B so you could operate closer (larger crossover slope) to the horns cutoff frequency and equalize the horn response in that region. I would hesitate to increase the back volume on the driver. Altec picked a particular back volume for that particular driver for a good reason.


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PostPosted: August 6th, 2017, 10:00 pm 
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Joined: February 28th, 2013, 3:31 pm
Posts: 363
Here's a link to a thread at Lansing Heritage about replacing foam with felt in older compression drivers. Has some links and photos.
http://www.audioheritage.org/vbulletin/ ... light=Felt


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PostPosted: August 7th, 2017, 8:27 am 
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Jim G wrote:
Here's a link to a thread at Lansing Heritage about replacing foam with felt in older compression drivers. Has some links and photos.
http://www.audioheritage.org/vbulletin/ ... light=Felt


Thanks.

The 802-d has a soft 1/4" thick, 3.5" dia felt which fits perfectly in the dust cap. Ordered 1/4" felt with adhesive backing from Amazon

https://www.amazon.com/gp/product/B001BXC9SG/ref=ox_sc_act_title_1?smid=AEF8AWXR95D0&psc=1


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