[Toecutter]

Watched the video on comb filtering. If you can't put two tweeters on the front of a speaker how do the line source get away with it?

[Hobbsmeerkat]

I tend to think of it more like you have so many peaks and nulls across the entire line due to the range in time delay that they all average out, esp the further away you get from them. And the closer they are, the better they're going to balance out, esp in the top end.

Now, if you're using a single, several-foot tall ribbon tweeter its likely not an issue, since its still a single continuous source.

[Early B.]

Watched the video on comb filtering. If you can't put two tweeters on the front of a speaker how do the line source get away with it?

Danny answered this question a couple of months ago somewhere in this circle. Maybe someone can find it and re-post it here.

[RonP]

I think he said something about you still being in the near field and that's why it's different.

[planet10]

All speakers have to make compromises.

Anytime you have sources with driver centre-to-centre greater than a quarter wavelength the frequencies above that point start to comb.

This annoys some people and others not so much.

A visual representation looks quite bad, but Toole say sthat the human ear/brain has mechanisms to deal with this, and the audio is not as bad as the audible.



If you are going to do an array of drivers the line really needs to be floor to ceiling, or you need to be listening in the far-field so that the spacing of the drivers is minimized.



https://p10hifi.net/TLS/downloads/taylor-line-array.pdf
https://audioroundtable.com/misc/nflawp.pdf

dave

[emailtim]

Watched the video on comb filtering. If you can't put two tweeters on the front of a speaker how do the line source get away with it?

Check out @ time code 9:00.

Tech Talk 13: Line Source AND Line Array Loudspeakers
https://www.youtube.com/watch?v=7bwU5HagoQo

A way to test this is to have a tall line array, point the mic at the middle of the line array and then take a measurement with and without about 1 foot of the middle of the line array covered.

[Scott Joplin]

Listening to the beginning of that video one may get the impression that comb filtering causes cancellations only. The effect is caused by interference which is both destructive and constructive.

[HAL]

Also measuring a line array in a room is an interesting process.

From the diagram above and research on segmented line arrays, you need to make measurements in farfield at least the length of the line array away.  This is much different than the 1m measurements that systems like MLSSA used for their technique.  If you look at the diagram above, you can see that on axis, the reinforcements start being more defined after the length of the line array away.  The longer the line array, the farther away the measurement or seating position should be.

You usually have to accept some room reflections in the measurement to get enough gate time to see how low it will go in frequency response.  If the mic needs to be X feet away, then all other reflectors have to be the same distance away for a quasi-farfield measurement (gated time measurement). 

[planet10]

the 1m measurements that systems like MLSSA used for their technique

Toole says that any loudspeaker should be measured farfield and the results scaled to 1m distance.

Line arrays are usually listened to (mostly) near-field. Where near-field transitions to far-filed is frequency dependent.

dave

[HAL]

Toole says that any loudspeaker should be measured farfield and the results scaled to 1m distance.

Agree, but in the case of a line array with cylindrical spreading, I would adjust by 3dB/2xdistance, not 6dB/2xdistance like a spherically spreading speaker.
[/quote]
Line arrays are usually listened to (mostly) near-field. Where near-field transitions to far-filed is frequency dependent.

dave
[/quote]
If you call 1 lambda the length of the line array, that is the lowest frequency the line array baffle will effect.  Hence the reason I would be at least that distance away for a measurement or at or past that for listening in a room. 

[Danny Richie]

The linked video explains a lot.

[Toecutter]

I definitely  understand  alot better now thank you.