Tweeter/mid dispersion

[ifsixwasnin9]

In general, how are tweeter and mids designed to disperse in a 3-way system? Mids usually have a wider dispersion than tweeter? My JBL L110 mids seem to have wider dispersion than the tweeters (or the tweeter loudness seems to drop off much more drastically than the mid loudness when off-axis, ie. periphery). I think I get a better overall balanced sound when tweeters are on-axis. I haven't noticed this so much in other speakers I've owned like Infinity, Polk, B&W. Is my general analysis anywhere on-track? Any input? (mid is 3.5", tweeter is 1")

(I've fooled a lot with the tweeter and mid controls. This speaker needs lots of taming when it comes to tweaking loudness. It's virtually out-of-control. The designers had a field day with the output of these things).

 

[j_garcia]

Tweeters tend to be more focused and yes, because those frequency waves are narrower and will tend to "beam" in a smaller area than a midrange or woofer. Off axis performance will almost always drop off earlier for a tweeter than midrange, which is why nearly all speakers have a "sweet spot", the area in which they sound best at your seating position. Some speakers are better than others with respect to off axis performance because they are designed that way, but you will still want to be in the sweet spot for best performance.

 

[Swerd]

In general, how are tweeter and mids designed to disperse in a 3-way system? Mids usually have a wider dispersion than tweeter? My JBL L110 mids seem to have wider dispersion than the tweeters (or the tweeter loudness seems to drop off much more drastically than the mid loudness when off-axis, ie. periphery). I think I get a better overall balanced sound when tweeters are on-axis. I haven't noticed this so much in other speakers I've owned like Infinity, Polk, B&W. Is my general analysis anywhere on-track? Any input? (mid is 3.5", tweeter is 1")

(I've fooled a lot with the tweeter and mid controls. This speaker needs lots of taming when it comes to tweaking loudness. It's virtually out-of-control. The designers had a field day with the output of these things).

Dispersion of each driver depends on its physical diameter.

In general, physics says a speaker driver can disperse sound widely if the sound's wavelength is larger than the diameter of the radiating surface, the cone or dome. As the wavelength get shorter (increasing frequency) and approaches the diameter of the cone or dome, sound begins to beam in a narrowly dispersed pattern. The transition from widely dispersed to beaming is gradual, not all at once.

The L110 is a 3-way with a 10" woofer, a 5" midrange, and 1" dome tweeter. These diameters are from this link: JBL L110. The crossover frequencies are at 1000 and 4000 Hz.

These frequencies suggest that at 1000 Hz (a wavelength of about 13.5") the 10" woofer is beginning to beam, and similarly at 4000 Hz (a wavelength of about 3.4") the 5" midrange is also beaming. Just how much is the question.

Instead of guessing at dispersion, it is best measured for each driver (while mounted in the cabinet) by a test rig with bursts of pink noise and an omidirectional test microphone placed at various on-axis or off-axis positions.

How are you estimating dispersion?

And are those tweeter and mid controls (the variable L pads) operating cleanly without static, noise, or cutting in and out? This is often a problem with older speakers with those variable controls, such as JBL used to make.