I Want To Take A Knife To My Altecs

[Geekstar]

i admit that i am responsible for spreading the idea of yanking the bug screens. Somebody i talked to on the phone told me it really opened up the sound so I tried it on a spare 802...yep, he was right!

I posted it on a mailing list I ran and got a lot of positive responses from brave souls who did it.

Later, I pulled the screens out of the 288s in my A5. rig and WOW, liked it!

Then one day I took down the 1505s to do something and placed them mouth down on the floor. A handful of dead bugs fell out!

Well, that's Texas for ya. No shortage of critters flying and crawling about. A horn might look like a nest or something.

I now think some kind of screen/bug protection is not a bad idea in some environments.

Bowtie427 made the suggestion that clean screens aren't so deleterious. Maybe he is right? Many bug screens in older used drivers are gooked up with junk, cutting off a substantial part of the open area.

Funny, I talked to an old friend last month who said he hated his JBL 2440s until he pulled the screens and thanked me for the tip. He said the difference was enormous. This said when I told him that I just picked up a pr of 2440s to use with some Klangfilm tractrix replicas I recently purchased.

My current Altec drivers still have the screens. I do have an old pr of 802Ds without bug screens and maybe I should get off my seat and compare this again. I'm now in DC where the insect population is moderate and the pests are mostly humanoid.

Certainly, screen removal won't solve xover issues but it might pay to make sure that they are at least clear of debris.

[mah]

I read somewhere that the affect of the bug screens was included in the design.

I can't find the reference. Over to the experienced old-timers.

[voice of the theater]

I keep the grills on my Altecs at all times except when I'm listening to them--that keeps the bugs out. Not to mention, I live in upstate New York--no bug problem in my house anyways. The model 14's sound noticeably "better" without the screens--the high end sounds more open and clear and extended. I wonder if sound bouncing/reflecting off of the screens and back into the throat of the horn was causing some type of distortion? I still have the screens -- they are intact but I highly doubt I'll ever re-install them since I don't plan on ever selling them. I left the screens in my Model 19's (802-8g drivers) because from what I've read here it's more involved to remove them from that driver (and keep the screens intact) and I don't want to do anything to my Model 19's that is irreversible--they are still the best sounding speakers I've ever heard (although the 14's are pretty darn close IMO)....

[GM]

I read somewhere that the affect of the bug screens was included in the design.

I can't find the reference. Over to the experienced old-timers.

Don't recall any specific reference ATM, but FWIW, my 'take' on it is that at the time these were designed, a nominally flat 50-11 kHz BW was considered to be sufficient for 'high fidelity' reproduction according to an early '50's era RCA recording/mastering studio, cinema sound design manual, which is no problem for Altec small format horn driver throat screens at their power ratings when driven with the variable DF tone controlled high output impedance systems of the time.

'Squeezing' the throat's design WL [~22 kHz/~0.196" diameter] 'bubble' oscillating through it though will represent a significant resistance that doesn't ~fade away until down ~ an octave [~11 kHz], right in line with the then prevailing HF design limit. Note though that with today's high power capability to massively EQ it flat it can create destructive VC heating that in my case caused one VC to delaminate from the dome .


After gluing the VC back on and not worried about bugs, I removed the screens on a hunch, centered EQ at 16 kHz and liked the results, which added a bit of artificial 'air' around the instruments, especially on live recordings done in nightclubs which already had some.


The younger females OTOH didn't like it at all, so always had to defeat it when they were part of the listening session/party goers. Later on, I found out that the ~top octave is generated off the VC's surround, i.e. it's all just noise, so no wonder they found it 'harsh'/'shrill', got on their 'last' nerves', etc..


GM



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I wonder if sound bouncing/reflecting off of the screens and back into the throat of the horn was causing some type of distortion?

Most definitely, though my SWAG is that the diffraction horn's mass quantities of mouth reflections are enough to 'absorb' them. Plus, unless stretched tight enough to push its resonance [Fs] above the driver's pass-band [highly unlikely], it's acting as a large, wide BW diaphragmatic absorber, a [potentially] far worse distortion generator/modulator, so most likely making the most audible difference.


The M19's foam surrounds helps with mouth, cab flange diffraction's, so doing similar to the 14s theoretically will further smooth out/'focus' its HF response. Fish tank foam filter or similar ppi [30 IIRC] covering its baffle with a thickness determined empirically, 'recessing' the tone controls, may prove beneficial.


GM