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Thread: I Want To Take A Knife To My Altecs

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    Senior Hostboard Member voice of the theater's Avatar
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    I Want To Take A Knife To My Altecs

    Seriously. I remember reading here a few years ago that some people cut the bug screens out of their 902 drivers with a knife. Does anybody recommend AGAINST doing so? Does anybody have any advise as to the best way to do this? Snap knife? I have a pair of Model 14's with 902-8a h.f. drivers and I'd like to perform surgery ASAP. The high end of my 14's isn't quite as "clear and open" sounding as the high end of my Model 19's--I thought that maybe this would help. I can't imagine that it's good for sound (especially high end) to have to pass through a screen. FYI, I always keep the grills on them when not in use, and they sit in my living room 24/7 -- never outside so bugs aren't really an issue. They have Altec 34647 diaphragms in them which I believe to be original. I'm not worried about the potential for a small reduction in the resale value of my Model 14's if it makes them sound "better" ( I will probably never sell them anyways). Thoughts?
    Being of "Sound" Mind

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    Senior Hostboard Member LOUDER's Avatar
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    Re: I Want To Take A Knife To My Altecs

    Are you sure that's what's giving you the difference ? Are the screens out of the 19's ? If I remember correctly there are four different versions of the 14 crossover. Could you need a capacitor upgrade ? I've never cut the screens out of any of my drivers, but i'm not trying to listen to the finest detail either. The Markwart article descibes a exacto knife and hemostats. Just be careful and make sure you get every last piece. One little strand in the gap or touching the phram will drive you nuts and cause you more work.

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    Senior Hostboard Member voice of the theater's Avatar
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    Re: I Want To Take A Knife To My Altecs

    My 19's still have screens in their 802-8g's. No, I'm sure the screens aren't causing the difference but figured removing them would help the sound of the 14's. Surprisingly, they actually sound almost as good as the 19's but I think there has to be a way to get the high end to sound "as good" as the 19's and not "almost as good". Both my model 14 and model 19 crossovers have been re-capped with Solen capacitors and sound noticeably better than they did before I re-capped them. I have the "preferred" version of the Model 14 crossover that people who discuss the variations prefer--and the overall balance of treble to mids to bass is excellent IMO. Can you provide a link for the Markwart article that discusses this?
    Being of "Sound" Mind

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    Senior Hostboard Member Audio_by_Goodwill's Avatar
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    Re: I Want To Take A Knife To My Altecs

    This doesn't sound like a good idea to me. Why? I don't know, but it reminds me of a popular automotive modification from a couple years ago. "Descreening" the MAF (Mass Air Flow) sensor. The idea was that without the screen, which was much thicker than window screen, you would get more air flow to the engine, and make more power. The reality, is the screen was to smooth the airflow so that the sensor could get a better reading, by eliminating/reducing turbulence. So while a slight increase of air would be possible at wide open throttle, the turbulence prevented the accurate measurement of that air, at all throttle positions. I was one of the dummies that did it. Finally, yesterday while replacing my MAF with a used one, I was able to carefully (they're delicate) move the screen from the used unit to my housing.

    Bowtie, this engine is the big brother to your 427.... mine's a 454 :-) (Okay Okay, mine's a stock Vortec, so you probably make more power)
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    Senior Hostboard Member Earl K's Avatar
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    Re: I Want To Take A Knife To My Altecs

    All my 902's ( & 908 ) have that windscreen held in place by the cardboard gasket ( apparently, because I haven't removed any of those c-board gaskets ).

    Removal seems simple enough though ( given a sharp hobby/exacto knife ).

    Restoration would seem to be just as straight-forward.

    FYI, all the response curves that I've seen generated in the last 15 years for the M14 ( & it's horn/driver combo ) lead me to one in-escapable conclusion;
    > the HF has a builtin curve that's most appropriate for Rock & some Popular music ( where it's roughness goes unnoticed ).

    It's HF is far from flat and can't actually ever be made even flat(ish) except with a "Heroic Network" intervention & redesign.
    - RichardC ( who was briefly a moderator over at the short lived GPA forum ) said as much ( though he's now a proponent of active everything when it comes to fixing the M14's draw-backs).

    Sorry for the bad news, but you'll never get the the same amount of HF from the stock M14 Horn/Driver/network combo ( as what's available from the M19s radial horn ) .

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    - The standard ( 30923 ) Altec mid-range suppression circuit will take down the mids ( while obviously enhancing what's there in the HF ) but it'll do nothing about filling in that gigantic "V" shaped hole you that see centered at 9K which is an area that most of us can still hear( and notice its absence ) .

    (Below) the grey trace shows what's typically available ( HF wise ) from the original M14 horn/driver combo ( EQed with a Z19 network ).

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    The top trace shows the 511a/GPA 902-8a combo.

    Last edited by Earl K; March 19th, 2018 at 06:02 PM.

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    Senior Hostboard Member BillWojo's Avatar
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    Re: I Want To Take A Knife To My Altecs

    I removed the screens on my 902's and it was no big deal. Since I was doing a bunch of mods at the same time I can't say if it made a noticeable difference.
    I tend to agree that they can't be helping the sound. The primary purpose is to keep bugs out in outdoor installations.
    If I remember correctly, I had the gaskets off so I poked through the screens and ripped them out. I do remember it was easy and no big deal.

    BillWojo

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    Senior Hostboard Member LOUDER's Avatar
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    Re: I Want To Take A Knife To My Altecs

    The only links I know are golf coarse's. But if you google Jeff Markwart's corner, his website ? will come up. On the left, download the sound practice's article. Third page is about removing the bug screens. Hopefully this helps. Although Earl posted some interesting facts.

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    Senior Hostboard Member voice of the theater's Avatar
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    Re: I Want To Take A Knife To My Altecs

    PHOTOS BELOW
    I got out the knife and did the deed this afternoon. As described by Earl, the bug screen for 902-8a's is attached to the front of the 902 driver, underneath/edges surrounded by a paper gasket -- between the face of the driver and the horn. I removed the fram from the driver, then removed the driver from the horn--and there was the gasket with the outer edges of the screen under it. I pried up the part of the gasket that was holding the screen in place, and the screen lifted right out--the screen itself is not glued to the driver. It came out in one piece and is made out of a non-magnetic metal (Altec knew what they were doing). I left the gasket on the face of the driver and safely stowed the screen so I could replace the screen if desired. I started out with one Model 14 so I could do an A/B comparison between the one with the bug screen and the one without the screen. When I bought these Model 14's, one of the first things I did (as is my custom when I buy used speakers) was to place them side by side and do an A/B comparison (with a mono source) to make sure they sound identical to each other. They did. So, I set them side by side again today, and low and behold the Model 14 with no bug screen sounded noticeably brighter than the one with the bug screen. I was surprised that there was such a substantial difference--I thought it would be a little more subtle -- like when I recapped the crossovers--I did them one at a time and A/B'd the recapped Model 14 and the one that hadn't yet been re-capped and there was an improvement--but nowhere near this extent. Earl--you've mentioned the h.f. EQ issue with 902's before and you or somebody posted that f.r. curve before too. I've always had to use EQ to add a pretty substantial amount of treble to my 14's to get them to sound "right". I add the most at around 9k (a fairly wide range centered at 9k) based on that frequency response graph and corroborated by my ears. Well, with no bug screen I am now adding roughly half the high end EQ boost that I used to add! They sound much more open and airy, and more natural now that I don't have to add as much treble EQ. The mids seem to be wholly unaffected. I'm literally floored by the difference and couldn't be happier. Earl--you own 902's. I highly recommend removing the screen from one and doing an A/B comparison against it's mate--you will be surprised by the improvement! ...and as you said, it's easy to put the screen back if you're not happy with the change. Here are some pics of the front of my now screen-less Model 14's and a pic of one of the bug screens. As I previously stated I always keep the grills on them when I'm not listening to them--and they never leave my living room (they're never outside).

    PS when I had the fram and screen removed, and the horn disconnected from the driver, I blew air through the driver/tangerine to get out any dust (I didn't see any though) and then took masking tape (folded in half or course) to clean the gap -- the tape came out spotless -- there's never been any dirt or dust in any of my drivers when I do this -- maybe because they're home stereo speakers / not used for PA etc.

    PSS -- I'm curious about what my Model 19's would sound like with no bug screens but am afraid to mess with them -- it's a non-reversible move with an 802-8G driver due to the location of the screen, right?


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    Last edited by voice of the theater; March 19th, 2018 at 10:25 PM.
    Being of "Sound" Mind

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    Senior Hostboard Member Earl K's Avatar
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    Re: I Want To Take A Knife To My Altecs

    VOTT,

    It's great this has worked so well for you ( & all so easily too ).

    Using 1/2 as much boost at 9K is a substantial gain to achieve.

    I think all the pre-60's era 802's had the screens placed right beneath the gasket ( so even removing that screen > smaller, mind you down inside the throat > could be effectively reversed into a more 50's look by using the 902 sized mesh ).

    1php?id81655

    1php?id81655

    My 902's ( long ago ) became donor mules ( diaphragm #35480 ) for my 802D drivers ( so I won't be trying this on 902s ).

    My main listening drivers are my 288-8K(s) on EH500s, which have noticeably more authority in the mids ( especially on piano hammers ) and are almost as sweet in the highs ( to my ears when listening to classical ).

    I'm handy with the test mic ( as well as the building of HF compensation networks ) so I can pretty much optimize any horn/driver combo I decide to listen to ( after wiring up a different passive ).

    My latest ( horn-hack ) uses the 802D adapted onto some ( cheap ) rather largish plastic ZXPC BiRadials ( which are maybe about the size of an 811? and about 30% larger than my Emilars in sq inch mouth area ).

    I bought them because they have a really great looking horn bell ( IMHO ).

    678

    Unfortunately, this horn is really a bad joke in its straight ( from box ) raw form ( hardly worth the $$40. ) but with effort it can be pretty well fixed up using about 1/2 a pound of modelling clay/electrical duct seal, placed inside the bell ( smoothing out the initial expansion area ).

    It currently sounds so good that ( IF ) I was a confident wood-worker I would quickly copy my hacked-horn into a permanent wood form ( I did say "IF" )

    Last edited by Earl K; March 20th, 2018 at 08:47 AM.

  10. #10
    Junior Hostboard Member sonofagun231's Avatar
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    Re: I Want To Take A Knife To My Altecs

    Some caution may be in order here. There are insects even inside homes - spiders or other bugs may find that opening attractive. In place of the metallic screen, you might consider using some acoustically neutral open cell foam grille material to prevent arachnid incursion.
    Last edited by sonofagun231; April 16th, 2018 at 01:20 PM.

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