How good is the Altec 511B horn compared to todays tweeters

[fpitas]

I thought dome tweeters had sensitivities in the 91dB/1W/1m sort of range?

An apples n' oranges comparison. To even try and compare the two, you'll need to XO the 511 high enough that it's merely a WG [guessing around 2 kHz] and once EQ'd flat I doubt it will sound much different or be much more efficient than a very high end cone/dome tweeter except that the latter will have a bit more top end 'air' that depending on one's hearing, may not be noticed.

You want the best of both and can afford them, buy a prosound WG loaded ribbon if they still make them.

GM

[joyspring]

I thought dome tweeters had sensitivities in the 91dB/1W/1m sort of range?

They do.

A 1 inch compression driver has a mass-induced -6 dB/octave drop above 3 kHz. A good CD horn will have an on-axis response nearly identical to its terminated tube (plane wave tube) response; that is, the unequalised CD horn output will match the driver power response. It must be equalised to be flat.

In the upper octave with equal electrical input power, the dome and compression driver will have comparable acoustical output power.

BobR

[joyspring]

Anyhow, I'll agree with Old Guy that choice of horn type / HF driver is a personal preference or - for a manufacturer - an application dictated by swings and roundabouts... that is, finding a balance of attributes that fits the matter at hand.

I had a set of 802/511Bs + 515B in 825 cabinets during the 1980s and they certainly sufficed at the time -- the 511s were quite pleasing on-axis so I understand why they're still sought.

BobR

[Panomaniac]

A 1 inch compression driver has a mass-induced -6 dB/octave drop above 3 kHz.

Which would put it down between about -11 & -22 dB in the top octave. Or about as efficient as a good dome. But don't forget, down low it's still much more efficient than the dome. That's where the energy is and were it should be used.
A great tweeter it would not be, but a great extended mid-range, it is.