Bug Screens

I know this is a controversial procedure, but I'm always thinking of ways to improve my speakers/acoustics/electronics etc.--and bottom line--overall sound quality. I know that to remove bug screens from 802-8G's, you need to cut them out with a knife. I'm just not going to do that -- I'd feel like I was taking a knife to the Mona Lisa. They sound amazing and I just won't deface them. However, I've heard that there's an easy and reversible way to remove the bug screens from 902-8A drivers (that I have in my Model 14's). I can't find the tread with our current search feature here, but I know someone here mentioned it once.

Question 1) Anyone know how to remove the bug screens from 902-8A drivers? Is it located between the driver and the Mantaray Horn? Do I just unbolt the driver from the horn and pull out the screen?

Question 2) Has anyone tried this with ANY classic Altec Lansing h.f. driver? Did you noticed increased clarity, or better imaging, or better h.f. sound in general (or anything else or any combination of the above)? Does any resulting "change" cause the driver to be out of spec--are the screens factored into the design and does removing them makes the drivers "too bright" or too loud or "wrong" in some other way?

Question 3) These speakers sit in my living room. If I remove the bug screens and notice an improvement in sound, is there a downside? I don't have bug problems here, but will that allow dust into the driver and cause problems down the road? Or does dust get through the screen anyways and get "blown out" when I crank them up!? (so, no downside?).

I'm in a tinkering mood--thanks in advance for any input....

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Originally Posted by voice of the theater

I can't find the tread with our current search feature here, but I know someone here mentioned it once.

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I'm looking into it now. I have the same problem.You have to use Google for the time being.I contacted Steven to ask him when the software upgrade will happen.I will let you guys know when I hear something back.It will also improve the Marketplace as well as everyone will be able to open their own thread there.We just have to wait for version 4.1.8.When that is ? Is anyones guess.

Interesting thought.... If you find the post make sure you link it here I'd like to see it too. If you were to have speaker cloth over your horn I would imagine it would keep the bugs out while not restricting as much as I would think the dust screen does. I still haven't done the felt cap no loading cap thingy yet. I did Start a new cabinet design this morning though so look for that coming soon. :)

Altec 511 question - AudioKarma.org Home Audio Stereo Discussion Forums

found one thread on AK....

hope it helps, i have no experience with this sort of modification...

Great thread, thanks for the link JMN. Some people over there say they heard a substantial improvement once the (dirty) screens were removed. One post there has me concerned about trying this with my 902's.
"I leave my screens in for two resons on the 802/808 drivers, I hate crawling bugs and removing the screen can cause the throats to resonate as it leaves play in the space taken up by the screen (the throat moves up and down without it)." Anyone know if this is an inevitable problem with removing the screens?

Found this thread here, but it isn't the one I'm thinking of. There was a thread here where someone said it was easy and reversible to remove the screens from a 902-8A but I can't find that one and have no idea what that method is....

http://www.hostboard.com/forums/f700...g-screens.html

I pulled the bug screens out of my 288s. Could not hear or measure any difference. I was surprised and a bit disappointed.

I've removed the bug screens on two pairs of 802Ds and heard subtle differences back before age too its toll on my HF hearing, mostly improvements in dynamics, i.e. 'air' around instruments, especially when the ultralights began aging.

GM

Use the "advanced" search window on the top of the page. Works fine.

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Originally Posted by Panomaniac

I pulled the bug screens out of my 288s. Could not hear or measure any difference. I was surprised and a bit disappointed.

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I agree Pano. I would leave them unless they are encrusted (clogged, eBay specials ). IMO there are only probably only a very small percentage of Folk's who can actually tell a difference.And I'm not one of them. Of course as the post states YMMV....

I have done this on all my small format drivers.

I noted the biggest effect in the imaging.
Try this. Listen to pink noise from your listening position. Move your head back and forth a foot to either side and note the phasey sound.
Remove the screens. Note that for the most part, the phasey sound disappears.
The sweet spot gets bigger.
This is my experience.

On the 900 series drivers it's easy as the screen is simply glued to the driver face underneath the gasket. Easy to remove and replace if you so desire.
800 series drivers you have to cut it out with an exacto or similar. I suggest you remove the diaphragm when doing this and suck any debris out (from the front) with a shop vac.

Ron

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Originally Posted by Altec Best

I agree Pano. I would leave them unless they are encrusted (clogged, eBay specials ). IMO there are only probably only a very small percentage of Folk's who can actually tell a difference.And I'm not one of them. Of course as the post states YMMV....

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288 may not go high enough to notice I would think.

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Originally Posted by RonSSS

800 series drivers you have to cut it out with an exacto or similar. I suggest you remove the diaphragm when doing this and suck any debris out (from the front) with a shop vac.
Ron

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If you get a piece of the screen or any kind of metal filings from exacto in the gap (Which get sucked into the mag.field) good luck getting that out.Off to GPA they go, so they can be demagnetized, and cleaned, then remagged. You just need to be real careful.

Quote:

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Originally Posted by RonSSS

I noted the biggest effect in the imaging.

The sweet spot gets bigger.

800 series drivers you have to cut it out with an exacto or similar. I suggest you remove the diaphragm when doing this and suck any debris out (from the front) with a shop vac.

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Correctomundo!

GM

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Originally Posted by Altec Best

If you get a piece of the screen or any kind of metal filings from exacto in the gap (Which get sucked into the mag.field) good luck getting that out.

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The screens I cut out were brass, so not a problem to vacuum out. For sure, I was super careful with the Xacto though.

GM

Wire mesh bug screens percent open run from approximately 50%-75% open (depending on mesh size) or in other words the driver throat is 25%-50% blocked (again could be less depending on the mess size used-but the opening is blocked somewhat). It would seem that sound 25%-50% blocked by the screen will send the sound waves will bouncing back into the driver and cause some sort of distortion. Based on that I have to believe removing screens is going to have a positive impact on sound and as a result I have removed screens from my 288s and 902s a hear a positive effect in particular that wider sweet spot that is mentioned above.

Yes!

BTW, the 802/806 screens were brass as GM said. The 902 screens appear to be stainless, but then no need to hack on them.

On the 288s I was hoping to reduce or eliminate the sharp FR dip at 8300Hz. No dice. Since the bug screen is just about at the right distance from the 'fram for that frequency/wavelength, I had high hopes. They were dashed. ;(

May try with other drivers and listen for sweet spot and phasing. Thanks.

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Originally Posted by GM

The screens I cut out were brass, so not a problem to vacuum out. For sure, I was super careful with the Xacto though.

GM

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My concern lies with the gap really, brass or not you still don't want debris in the gap and the screens start to fray and fall apart once cut and can go everywhere.I heard no difference, so for me it is a waste of time.And opening a can of worms IMO. For me anyway, YMMV !

I tend to sit in the same sweet spot (Right in front of my Laptop) all the time when listening to music so the phasing isn't an issue for me.

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Originally Posted by Panomaniac

On the 288s I was hoping to reduce or eliminate the sharp FR dip at 8300Hz.

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Isn't the entry of the conic section about 13/16" in diameter?

GM

I have been totally occupied with my main profession, so no activity here for quite sometime. But I go thru the posts.

Two issues came to my mind after going thru this thread......

First.....yes the bug screens reduce the throat exit area by around 25% to 50%. So will not the removal of this restriction affect the FR-curve as this changes the throat loading ? For this size of compression drivers, the throat area will be sensitive to changes of 1/10th of a mm^2 loading even !

2nd...... while all these drivers were spec-ed, these bug screens were sitting there in the throat passage or they were just added on later just as 'a ' bug screen ? Hard to believe that these meticulous manufacturers were not taking this into account while designing them.

I had once gone thru a phase similar to this around 3 yrs back while trying to restore a pair of Goodmans Midax drivers (for a friend of mine), one of which had a completely blocked/clogged screen, and in huury I had decided to do away with it. And I still remember that when I had A/B-ed it with the normal good one, though at first shot it had sounded cleaner (more air) than the standard one, it quickly became apparent that it had shifted its FR linearity. There was a definitive peak in the lower spectrum, which was not there in the other one. I had very quickly (& carefully) cleaned the clogged screen & fitted it back. And the sound was back. I think proper loading at the throat is responsible for the flatness of the response spectrum of the driver concerned.

The Midax is a peculiar driver, in the sense that it (the throat chamber) is tuned for a range between 1k-5k Hz only. May be due to this it was more sensitive to such changes. But after this incident, I have never tried to tamper with a compression driver again, especially when it is from a very reputed maker.

I couldn't reach the screens on my 604's for some reason...theres a metal piece with some small round slots in it just behind the phram and I couldn't figure out how to move it. So all I did was the Markwart suggestion of removing the loading caps and felting the inside of the rear covers. I used the peel and stick loop part of some velcro I bought and covered the whole inside of the rear cover. It has excellent stickyness so it'll stay where it was put. I will admit it was close to a vast improvement in clarity and soundstaging although one other point was that when I opened up the push on connector phram the red dot was by the terminal on the right side of the phram and when I opened up the other speaker phram the silver L1 was by the left side terminal of the phram so for once in their life both the red wires from my crossovers are hooked to the proper terminals. I'm still trying to dial them in but I like how much nicer they sound now. :) Thanks Jeff.

Yes......felting the inside of the back covers is really very good for home-use, as it will mellow down that almost jarring Altec brightness quite a lot.

My Valencia's that I purchased new in the 70's did not come with bug screens so if bug screens were taken into account with the design the question is which design home or pro?

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Originally Posted by endeeinn

My Valencia's that I purchased new in the 70's did not come with bug screens so if bug screens were taken into account with the design the question is which design home or pro?

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This is interesting info..., at least for me. Does the Valencia use a standard Altec crossover or it has its own specific model ? Like many others here I am no Altec expert to know all these, but if the bug screens were taken into account, then the xover should be model specific.

Quote:

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Originally Posted by RonSSS

I have done this on all my small format drivers.

I noted the biggest effect in the imaging.
Try this. Listen to pink noise from your listening position. Move your head back and forth a foot to either side and note the phasey sound.
Remove the screens. Note that for the most part, the phasey sound disappears.
The sweet spot gets bigger.
This is my experience.

On the 900 series drivers it's easy as the screen is simply glued to the driver face underneath the gasket. Easy to remove and replace if you so desire.
800 series drivers you have to cut it out with an exacto or similar. I suggest you remove the diaphragm when doing this and suck any debris out (from the front) with a shop vac.

Ron

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I'm going to leave my 802-8G's alone (Model 19's). I just can't bring myself to take a knife to them. However, from what you're saying it sounds like it will be easy to remove the screens from my 902-8A's (Model 14's) and reversible if I don't like the change. If I do like the change, I will still keep the screens in a safe place so they can be returned to their "home" i.e. drivers returned to their original factory condition at any time. BTW, I have never removed or attached a h.f. driver from a horn. Yes, I'm still very much a rookie in a technical aspect with Altecs especially as far as the nuts and bolts end of them--but hopefully not as far as the strictly audio side of them--speaker placement, acoustics, putting together the "right" combination of components for a great stereo system, setting the crossover EQ, etc. (and general appreciation)....... As far as "nuts and bolts"--I've recapped crossovers (and replaced diaphragms in my old A7's), and that's about it......

QUESTION ONE: If the screen is "simply glued to the driver face underneath the gasket" does that mean all I have to do is unbolt the driver from the horn and the screen is right there? Just peel it off and that's it? Or will there be a gasket in front of it that I have to remove first to get to the screen and if so, is that glued to the screen or will it just come right off?

QUESTION TWO: If I'm careful not to over-tighten the bolts when reattaching the 902 to the (plastic) Mantaray, there's no danger of damaging the Mantaray in this process, right?

QUESTION THREE: Is there any danger of having the alignment "off kilter" when reattaching the driver to the Mantaray or if the bolts are tight is it automatically aligned properly? (I'm assuming no need for shims, etc.) Sorry for all the questions, but this is a new tweak for me and if I mess up my Model 14's, I'll be wishing I wasn't tinkering/striving for improvements.....

Someone on the Audio Karma thread mentioned this. "I leave my screens in for two resons on the 802/808 drivers, I hate crawling bugs and removing the screen can cause the throats to resonate as it leaves play in the space taken up by the screen (the throat moves up and down without it)."

QUESTION FOUR: Anyone know if removing the screens will leave play in a 902 (and cause the throat to resonate) or since the screen in a 902 resides between the driver and the horn is that only a (potential) problem with other Altec drivers, not the 902 series?

QUESTION FIVE: Is the (glued in) screen likely to be ruined/disintegrate when trying to remove it due to it being glued in place or will it come out pretty easily and in one piece?

My Model 14's are in a relatively high traffic area of my house (the living room). For that reason, I keep the grills on them at all times except when listening to them. Then I take a minute to remove them, and promptly put them back on when done listening. (don't want something or someone accidentally hitting the exposed woofer or spilling something into the horn, etc. when I'm not in the room.....) I would think having the grills in place at all times would be sufficient protection from dust etc. and we have no insect "problems",

QUESTION SIX: The screens aren't really necessary for protection under these circumstances--correct?

QUESTION SEVEN: Are this many questions excessive--am I being a real pain in the @ss this morning? ;) On a side note (philosophical note--no pun intended) I guess I'm being this cautious before proceeding because my Altec collection (three pair of speakers--not a huge collection granted) is probably my most precious possession. I try to not be overly-attached to material possessions--family, friends, health, etc. all come first for me (in most cases!) However, when I have yelled at my wife for setting a drink on a speaker (the Valencias I used to own) she once commented that I love my speakers more than I love her. Not really true I guess, but I can't help but wonder if they'd be harder to replace than she would! (that's just wrong!).........

Thanks again in advance to everyone for any input. I'll be sure to report any audible changes (hopefully improvement) if any after I've pulled the screens. I probably wouldn't attempt bug screen removal for P.A. speakers. I'm guessing that a home hi-fi set up may have a lot more to gain (and less to lose) by pulling the screens (more critical listening environment with less debris and dangers for the screens to prevent) so it just might be a worthwhile tweak.....

OK, maybe six questions was a little excessive to expect a response! :) I think the answer to just three of them would do the trick for me.

QUESTION ONE: If the screen is "simply glued to the driver face underneath the gasket" (as RonSSS mentions) does that mean all I have to do is unbolt the driver from the horn and the screen is right there on the front of the driver? Just peel it off and that's it? Or will there be a gasket in front of it that I have to remove first to get to the screen and if so, is that glued to the screen or will it (most likely) just come right off?

Someone on the Audio Karma thread mentioned this. "I leave my screens in for two resons on the 802/808 drivers, I hate crawling bugs and removing the screen can cause the throats to resonate as it leaves play in the space taken up by the screen (the throat moves up and down without it)."

QUESTION FOUR: Anyone know if removing the screens will leave play in a 902 (and cause the throat to resonate) or since the screen in a 902 resides between the driver and the horn is that only a (potential) problem with other Altec drivers, not the 902 series?

QUESTION THREE: Is there any danger of having the alignment "off kilter" when reattaching the driver to the Mantaray or if the bolts are tight is it automatically aligned properly? (I'm assuming no need for shims, etc.) Sorry again for all the questions, but this is a new tweak for me and if I mess up my Model 14's, I'll be wishing I wasn't tinkering/striving for improvements.....

1, 4] No clue.

1a] None of mine did/do, so no clue what they're referring to. What it does do is leave a sharp groove that ideally needs to be filled/honed since it will cause some reflections back to the throat, though just smoothing it out with play doh or similar is sufficent.

3] The gasket is the shim and properly torqued, the driver lines up good enough for prosound and evidently the vast majority of Altec consumers. For the few, there's some audible wide spectrum improvement gained by ditching the cardboard gasket for a metal one and align honing the horn/shim/driver to tight specs to mimic the tight throat of the WE 555, using wax paper or similar for gaskets, or if you're as anal as I was in my youth and got a buddy with a machine shop, mill everything flat to tight tolerance and use a little bit of lubricant for gaskets, then DIY hardwood or similar alignment dowel to align them up if the driver is ever removed.

GM