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Thread: Altec 9844-8B

  1. #301
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    Quote Originally Posted by Skywave
    When you rig them into a box sooner or later, I'd be interested to know how the sibilance range sounds without the notch. As you said earlier, graphs are open to interpretation, and to my eye, given your stringent display mode, the notch may not be needed. I guess you'll have to put your ear on it.
    - I'm pretty sure I would be adding a bit of notch-filtering into the 7-8K region.

    - Even though todays' FR study shows the @ 7200 hz peak somewhat dimished from yesterdays pic .
    - I would need to shoot a bunch of polars before deciding on a final contour circuit ( as well as the addition of any notch-filtering ).

    - Here's the previous FR ( from yesterday ) for review ;



    vs todays', which is seen below ( this is the same driver-horn combo as yesterday / just a bit of physical movement of the test mic position has occured ) .

    >< cheers
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  2. #302
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    Zilch,

    - Here's your normalized CSD/"Sonogram" for the 902-8b/H811 combo ( you ran this @ a year ago ) .
    - There's a lot of midrange energy ( in green, up to 3K ) just 10 db down ( @ half as loud as the fundamental ) .


    - Here's your Selenium 220 on the JBL "econwave" wavequide . The FR is Eqed & hipassed. The following pic is the FR curve of the same .
    - There's less energy at 10 db down ( now displayed in yellow ) / one now has to drill down to minus 20 db to find "it" ( again , it's the green streaks with this scale used /& it's a pretty even spread across the spectrum of interest ).
    - For those watching, a change of 10db is subjectively ( depending on direction ) either twice as loud or half as loud .




    - Here's my Altec hybrid combo ; first the FR then the CSD/Sonogram .
    - It's pretty clean , I'd say ( subjectively ) .
    - My 802d driver uses the same Altec 35480 diaphragm as in your study / though it is coupled to a completely different horn.
    - It's ( mostly ) midrange resonances are 18 to 24 db down ( depending on how one interprets my EQed/"normalized curve" ).


    >< cheers

    PS; One interpretation here ? Comparing my CSD ( to yours of the Altecs that you studied ) doesn't say very good things about the H811 horn ( because of its' significantly hotter resonances / by @ 10db / to my eyes ).
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  3. #303
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    Our windows are about the same lengths, so the results are comparable. I rarely do 50 dB FS, unless I just forget to double the resolution. It kinda looks like I was trying to show how long that 811B midrange resonance was lasting, and yes, it looks pretty significant to me.

    The culmination of all of this was an A/B evaluation Steve Bliss and I did one day, 4507 w/ 2235H on the bottom, we swapped between 811B w/ BMS 4550 and PT-F95HF w/ BMS 4555. 811B coloration was NOT subtle, and neither of us has looked back since.

    I'm not sure which P-Audio horn you're using, the small butt-cheek? That may be the difference.

    In any case, I abandoned 811B and 511B primarily because they beam the VHF when you get them to make it, and their coloration, which I thought I liked at first, and the Altec tangerine drivers because they "undulate," and BMS doesn't. There are other options for the Altec drivers, perhaps, such as Radian diaphragms but, in my view, none are worthy of pursuit when modern compression drivers are slam-dunk better at doing what I want them to do, brand new off-the-shelf for less $$$, and in "vintage," LE85s kick them to the curb, basically.

    Not that I'm seeking affirmation of that judgement, but your earlier CSD evidences undulations at the same frequencies as the tangerines lurking there; compare the tangerine response curves to see it. I don't think it's coincidence, nor is the same characteristic measured in Gary's 802-8Gs with new GPA diaphragms and the CBS Labs Model 19 response from 30 years ago. Let the "Believers" figure it out, if they are so inclined, which they apparently aren't. I'm done fighting with them; they have a different agenda and I am not a crusader....

  4. #304
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    Quote Originally Posted by Zilch
    I'm not sure which P-Audio horn you're using, the small butt-cheek? That may be the difference.
    The horn that I'm using with my 802D Hybrid ( for the previous measurements ) is identical looking to the following pic ; ( I bought a pair about a decade ago, when they were marketed by a Korean Co. called "Sammi" / at the time they were described as an exponential hybrid ).

    >< cheers


  5. #305
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    Zilch,

    - Above is my Altec802/PH230 combo ( for a quick review ) .

    - Below is the B&C DE-16 on the same PH230 horn ( though it'll always be a "Sammi" to me ).
    - First pic is the FR of what's being studied .
    - Second is the CSD / Sonogram .( The CSD is "lowpassed/cut-off" at 14K to eliminate the downward skewing effects of the 17K peak .)

    - I've expanded the depth of the CSD so that I could get the resonances to showup in a more vibrant color ( now, yellow in this case ) .

    - One can see that the area where the Altec/Horn combo has it's primary resonances is pretty similar ( in Freq. region & Amplitude ) to the B&C/Horn combo .
    - That leads me to believe that it's the horn dominating the "addition" of the "coloring" resonances in this area .

    - I'd be interested to see a similar study done of your BMS 4550 driver on the Altec 511 versus the JBL waveguide ( PT-F95HF ) . Since Skywave uses the H811( with BMS driver ) , it might interest him to know just how much ( in db terms ) the horn colors the sound .
    - Then a fix" might be attempted ( a la "Geddes foam" or Urei horn treatment ).

    >< cheers

    PS: I added a third pic below which is another type of CSD. This "Burst Decay" is from an "end perspective" which I find helps me see the areas of resonance ( big picture wise ) .
    BTW: the DE-16 is "NLA" ( it's now more than a 10 year old design from B&Cs' earlier product lines .
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  6. #306
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    Earl, I just stumbled onto this thread and saw your mention of the B&C DE16. I am looking for more information / opinion on this driver, can you comment?

    Thanks,
    Martin

  7. #307
    Senior Member Skywave-Rider's Avatar
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    Quote Originally Posted by martinq View Post
    Earl, I just stumbled onto this thread and saw your mention of the B&C DE16. I am looking for more information / opinion on this driver, can you comment?

    Thanks,
    Martin
    Hey Martin....
    Earl has some amazing data and I'm sure he'll pop in.
    Saw ur post in DIY.

  8. #308
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    Quote Originally Posted by Skywave-Rider View Post
    Hey Martin....
    Earl has some amazing data and I'm sure he'll pop in.
    Saw ur post in DIY.
    Hey Skywave, I saw your post too. Guess we're chasing around the same bush.

  9. #309
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    Hi Martin,

    - There's not much to tell , since I've never put these DE16s through any serious listening tests . This is mostly because I prefer to listen to ( at home ) a driver that can be crossed over at 800 hz or lower ( & that criteria excludes most available drivers designed after about 1980 ) .

    - I believe that I did use this driver for a while in my SR work back when I owned a pair of EAW JF80s . B&C oemed quite a few components for EAW & Yorkville Sound & my memory of the EAW driver was that it looked exactly the same as the DE16 ( just a different decal ).
    - In the EAW box / coupled with the RCF 10" / it represented a very nice combination .

    - FWIW, this B&C driver is a previous generation to B&Cs' current offerings ( ie ; its' now obsolete / & it's repalcement is the DE160 ) .

    >< cheers

    ps ; sorry I can't be more definative on the matter .
    - if you found a pair to buy ( cheaper than what PE sells the DE160 for ) / they are worth owning, if you don't mind a 2K crossover point .

  10. #310
    RIP 2011 Zilch's Avatar
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    Augerpro's 414 measurements here:

    http://sites.google.com/site/driverv.../gpa-altec-414

  11. #311
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    Thanks for your take on them Earl. I don't see the DE160 for sale at PE, but they are going for $120 as US Speaker so I'll take that as a baseline.

    http://www.usspeaker.com/B&C-DE160-1.htm

    Any comments or tips on where to find specs or replacement diaphragms?

  12. #312
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    Quote Originally Posted by Zilch
    I'm suspecting the "TANGERINE Radial Phasing System" is the culprit here. Has no one else ever measured these Altec drivers and horns? Where are the curves? :dont-know
    Quote Originally Posted by Zilch
    At first, I thought it was the vanes in the sectoral horns, but I believe Skywave and I have both demonstrated that the HF "undulations" do not occur using BMS drivers. Next prime suspect, the radial tangerine phase plug.
    - Blaming the Tangerine phase plug for the observed notches ( 2.5 - 3K & 6K ) in the above plots, is a no-go from my perspective .

    - See below ;


    - This highly critical look at the Altec 802-8T (a "T" is a "G" with a loading cap in place ) shows little sign of the notches in question .
    - IIRC, this curve was accomplished by using a 10uF Hipass followed by a simple RC contour circuit ( comprising another 10uF cap paralleled to an 8R resistor / no LCRs, as I am sometimes liable to toss into the fray ) .

    - This plot is of the "alnico" driver fitted up with the more modern 35647 diaphragm ( still available from GPA ) .
    - The horn is a Sammi exponential that I keep around because it creates a nice on axis response for most drivers bolted to it ( though, it has awful off-axis response ) .

    Quote Originally Posted by Zilch
    My most expert analysis of the roller-coaster thing at this juncture is, "I don't know," and I can only point to some of the same indications you have observed. I see it with Gary's 802-8G tangerines on 811 and 511, and I see very similar in the CBS Labs measurements of Model 19 from 30 years ago.
    - I think it's safest ( for now ) to go back to this (now 2 year old ) conclusion ( which I happen to share ) .
    - FWIW, it seems that most of the Altec measurements that you did ( with Gary Ls or Skywaves drivers ) were of drivers fited up with either the first or second generation of Altec "LITE" diaphragm ( ie; 23744 or the 35480 ) .


    EarlK

  13. #313
    RIP 2011 Zilch's Avatar
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    I have no more info today, and with respect to Altec inventory, just a 511 kicking around under the bench.

    Has anyone over on the Altec forum followed up on any of this?

    [Have the purveyors of Altec gear gotten around to posting any actual data yet...? ]

  14. #314
    Senior Member Skywave-Rider's Avatar
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    Earl, are you saying I should re-measure the 902s with the loading caps back on? I think I kept them.

  15. #315
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    Quote Originally Posted by Zilch
    Has anyone over on the Altec forum followed up on any of this?
    - Not that I'm aware of / though member "Panomaniac" is a willing practitioner of his measuring equipment .

    Quote Originally Posted by Zilch
    [Have the purveyors of Altec gear gotten around to posting any actual data yet...? ]
    - I don't think so . I suspect there's a good reason for that .
    - The last rumour I heard was that the phase plugs' slit count is now down to 9 ( from the standard 11 ) which itself was down from the original 13 Radial slits mentioned in all the official Altec literature .
    - Another rumour is the possible re-release of an Alnico magnet-ed 802 . ( FWIW )

    <> cheers EarlK

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