2 tweeters vs 1 tweeter vs no tweeter

[6thplanet]

Tweeters are the devil!! Evil I tell you, pure evil!!!

 

[agedhorse]

Spot on! So the important thing here is to look at the wavelength: At 2000Hz your wavelength is about 17 cm (half a foot), so for any realistic spacing between the tweeters you are in a realm where moving your head even a little bit will wash out the interference effects. Add in multiple reflections in the room (as agedhorse pointed out) and this is not something I would ever worry about in a real setting.

I've had great success demonstrating the above effect with two frequency generators finely tuned and speakers carefully placed at the front of a large lecture theatre with 200+ students. The frequency of 300 Hz gives a wavelength of a meter, which compares well to the average seat spacing. In a packed auditorium you can then ask people to stand up if the volume at their seat is loud (practical tip: give a reference tone to compare the volume to first). And then everyone can immediately see the resulting pattern in the room .

What I learned from that is that you really need to work on your setup, optimise speaker placement, minimise reflections, use pure tones (single frequency sine waves, no harmonics) only for the effect to be noticable at all. None of these conditions are fulfilled in a gigging scenario. You're good to go!

The results become even less critical with a harmonics filled signal from a bass guitar.

 

[agedhorse]

You have to look at the paths of travel, not just the driver spacing.

If you are on axis with the mid point between the two tweeters, the path lengths will be the same and there will be no cancellations (ignoring boundary reflections).

This is why it’s completely inconsequential in the far field, where the path lengths come close to convergence. It’s more of an issue off axis near field, but generally not much of an issue in practice.

 

[Al Kraft]

Tweeters are the devil!! Evil I tell you, pure evil!!!

Some are better than others and those that are higher quality and adjustable are fine for me. I like the mid/high speakers that Duke puts in his AudioKinesis cabs...and I will admit that some of that could be the way he designs the crossover network.

I especially like the smooth, seamless transition between high and low elements in the Mesa SW cabs and Bergantino cabs.

 

[JimChjones]

The results become even less critical with a harmonics filled signal from a bass guitar.

I was about to ask about that.

If I'm right in understanding that the comb lobe size and distribution is frequency dependant, doesn't that mean that it's going to be different for each harmonic and for each note? And does that in turn mean that out in the audience you're going to get multiple different interference patterns for each note, and also different interference patterns for each note? And then as noted you must add wall and ceiling reflections into the mix, and presumably another bunch of reflection be it minute, from the audience?

Seems to me that the disturbing simple graph of lobes one may draw in theory for a single frequency must turn into a conglomeration of varying and overlapping lobes, and, as the poet said, signify nothing?

 

[agedhorse]

I was about to ask about that.

If I'm right in understanding that the comb lobe size and distribution is frequency dependant, doesn't that mean that it's going to be different for each harmonic and for each note? And does that in turn mean that out in the audience you're going to get multiple different interference patterns for each note, and also different interference patterns for each note? And then as noted you must add wall and ceiling reflections into the mix, and presumably another bunch of reflection be it minute, from the audience?

Seems to me that the disturbing simple graph of lobes one may draw in theory for a single frequency must turn into a conglomeration of varying and overlapping lobes, and, as the poet said, signify nothing?

Generally correct, the simplified scenarios used to explain the principle are quickly dwarfed by the more complex reality.

 

[Aloe]

well, a tweeter is more directional than the low-frequency drivers. that's why when you raise it, you hear it better.

I usually start with disabling the tweeter on the bottom cab and maybe turning down the top one.

don't overthink the negative effects of two tweeters, you likely won't need two of them.

 

[agedhorse]

well, a tweeter is more directional than the low-frequency drivers. that's why when you raise it, you hear it better.

I usually start with disabling the tweeter on the bottom cab and maybe turning down the top one.

don't overthink the negative effects of two tweeters, you likely won't need two of them.

Generally a tweeter is less directional than a woofer at higher frequencies.

 

[S-Bigbottom]

Don't forget the tweeters in the PA.

Adjust your cabs as you like it. 1, 2, 3, 4 or no tweeter, it's all good.