Crossfiring

[will33]

When crossfiring does the SPL add up the same way?

Using a piezo as an example. If one gives 90db, 2 would give 93. If you crossfired 4 of them would you end up at 96 on axis or would you have 93 going left, 93 going right and thus 93 in the middle? Or 93 off axis and 96 on axis?

I'm going to assume the rule would apply to all drivers, if it doesn't, let me know. This is without taking coupling into account.

Thanks.

[DukeLeJeune]

In general, a configuration that spreads out the area covered will result in reduced on-axis SPL but increased off-axis SPL relative to a configuration that results in a narrow pattern. Imagine one of those adustable nozzles for a garden hose: The wider the pattern the less intense it is on-axis, but now you have off-axis coverage that you didn't before.

With crossfiring, the details matter: spacing, angle, and radiation pattern of the individual elements (which usually changes somewhat with frequency). Assuming you're cross-firing with the goal of roughly doubling the pattern width, two 90 dB tweets would give you 90 dB across roughly twice as wide an arc as a single tweet. So crossfiring two 93 dB stacked pairs would give you 93 dB across the wider arc.

I've done a bit of over-simplifying here; in practice, often the radiation pattern of cross-firing drivers starts looking like a puffy "V" at higher frequencies because each driver is beaming. But this will still usually be an improvement in coverage compared to a single driver.

As a general configuration guideline, keep the horizontal spacing between the cross-firing drivers (or arrays) as small as practical while still getting the angle you want.

Duke

[billfitzmaurice]

Originally Posted by will33

When crossfiring does the SPL add up the same way?

Using a piezo as an example. If one gives 90db, 2 would give 93. .

In a forward firing arrangement parallel wired you get a 6dB increase for each doubling of driver count. When cross-fired you'll generally get only 3dB additional on-axis, but with nearly twice the dispersion, so the overall power response is up 6dB, but spread over a wider area.

[will33]

Thank you guys for the info, making my life easier here.