Martyn Miles
pfm Member
They seem to have fallen off the radar.
I’ve certainly not seen anything about it.
I’ve certainly not seen anything about it.
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Graham Audio BC1-50 speakers.
- Thread starter Martyn Miles
- Start date
Geoffreybombom
pfm Member
My BC1s cost £60 25 years ago, second hand of course. Best Hifi buy I ever made. Second was £40 for an A&R A60, still got them both. Wonderful.
Martyn Miles
pfm Member
I had the exactly the same combination in 1979.
As you say, wonderful.
As you say, wonderful.
sktn77a
pfm Member
FWIW - A Celestion HF2000 supertweeter that's missing its perforated brass grille will be down on output from 5kHz-17kHz by as much as -3dB in places (I know this because I've measured it!). So, if you've got speakers with HF2000s that are missing their grilles and find the top end a bit reticent, buy and fit the brass grilles, they are a crucial design feature!
Interesting observation. The same is true of the T27 tweeter in the LS3/5a. The perforated metal grill increased HF output significantly and was also part of the design (as was the heavy Tygan material on the front cover).
tuga
Legal Alien
Does it "increase" HF output or only refocuses/changes the directivity?
ToTo Man
the band not the dog
Good question!
I can't remember where I read it, but apparently the perforated brass grille increases air pressure in the gap between the tweeter's diapragm and the grille. How this results in increased SPL I don't know as I'm not a physicist, something to do which changing the impedance coupling between the tweeter and the air in the room?
By refocusing directivity do you mean reducing the amount of output the tweeter sprays horizontally and vertically off-axis and sending more of it forwards, like a horn? I can only comment here from subjective listening but a T27 with brass grille fitted sounds louder in the top octave or two than one that doesn't have the brass grille, even when listened to off-axis, but I'd need to measure to be sure as the last time I listened to a T27 without the brass grille was almost a decade ago!
tuga
Legal Alien
Apparently the Kef "tangerine" tweeter works like that too:
Not only does the outside of the dome move slower than the center, it also moves at an angle to the center.
This has a not-so-subtle effect on the quality of the sound a tweeter produces.
A perfect surface normal velocity for a tweeter would be the same over the entire dome surface, but this isn't possible because the dome surface would have to stretch and tweeter domes that stretch don't sound very good at all (well actually, they wouldn't even make any sound in the first place).
Because the Tangerine Waveguide corrects for this non-ideal dome motion, sensitivity at the top end of the audio band is increased.
Dispersion is also improved because we have shaped the fins and channels of the waveguide specifically to control the expansion of the soundwave into the waveguide (horn).
https://us.kef.com/blog/the-sweet-sound-of-kef-s-tangerine-waveguide