288 may not go high enough to notice I would think.Originally Posted by Altec Best
Enjoying Altec Speakers since 1972
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.
Correctomundo!
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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.
Enjoying Altec Speakers since 1972
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.
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.
Isn't the entry of the conic section about 13/16" in diameter?
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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.
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