Hello all !
I have a pair of Altec 511 b's on 811 a horns. I would like to use them in my system. Is it nornal that the top end of this configuration only produces highs to about 8khz ? I thought these would do about 15k .
The 511B is the 500Hz version of the 800Hz 811B lens so I seriously doubt it's 'driving' the 811B. If Altec, the drivers used could be 802, 804, 806, 807, 808, 902, or 909 series depending on their age, app, and what diaphragm is in them. Then there's the component versions used in some consumer apps, so without knowing which driver is on the 811Bs..........
Regardless, the 800 series drivers all have AlNiCo magnets which will weaken over time depending on their amount of use/abuse, so yours may just need to be drained/rezapped. Also, these 1" drivers are done by ~4300Hz so are in direct radiator/break-up mode above this point. Consequently, between this fact and that the 511/811 lens is a constant directivity (CD) design they must be EQ'd to get a ~flat response out to 15-20k depending on the driver/diaphragm used and acceptable amount of shelving/EQ.
Thank you both for your reply.
I have 806a's on h-811 b horns. I am curious about the possibility of getting them to work up to at least 15k flat ( flatish). Ha Ha .
Also, What is this about the magnets ? Please explain this to me. What is the process ?
As far as use and abuse, I know the original owner and the were well taken care of.
If still stock, then the 806s have alum. diaphragms, so assuming the magnets are still strong it will take either ~+12dB boost at 15kHz or this much shelving with a bypass cap (R/C network). IOW, it rolls off 2nd order above ~7.5kHz and why many folks switch to the later 802-8G or 909 series driver which goes out to 20kHz with minimal EQ. Other folks just use a R/C network to shelve to match the LF section and if still too weak on the topend, then they add a supertweeter to fill in. This improves off axis response somewhat so is a better solution if folks sit outside the 811's rather narrow HF 'sweet spot'.
AlNiCo loses its charge over time, and rather rapidly if struck or overheated. If these were only used in a HIFI app, then they may still be fine, but if PA then they will need to be drained/re-magnetized by someone set up to do it, like Great Plains Audio.
Oops! I forgot to mention that if at some point you choose to upgrade to a later Tangerine phase plug driver to get the increased HF response will require an 800 Hz XO min. or it will need excessive shelving due to the fact that a compression (bandpass) driver can only work over so many octaves, having to 'rob Peter to pay Paul' as they say.