Will this cause out of phase?

slopps · 22nd March 2010, 10:45 PM

So I'm building a speaker enclosure with two small (3 inch) full range drivers from Fostex.
I was going to create a single box with one of the drivers aiming out the front of the box and then create an 18 inch horn (similar to these) sticking out of the top of the box with the second driver placed inside of it (like a front mounted horn).
Since one speaker will have 18 inches of space to travel up the horn before hitting the open room is this going to cause any sort of weird echo or sound strange or will it be fine?

picowallspeaker · 22nd March 2010, 11:29 PM

Dear Slopps , you answered yourself .
There are many more experiments you can do with two same drivers in a box.
One is to make a dipole ,placing them back to back in a closed box (opposite faces of the box)and connecting the in anti-phase . Then a bipole ,by connecting them in phase.
In the first ,size (internal volume) really isn't a matter ,because the air is pushed and pulled by the two membranes in sinchrony. Geometry of the cabinet and size indeed are important ,for the many interactions of front and rear waves.
Or just put them nose-to-nail ,bare ,with four long screws-barrels to keep them firm,close and parallel ,connected in phase of course...in this way I don't know what happens but it's nice ( maybe some harmonic cancellation)and a subwoofer is needed.

rjbond3rd · 23rd March 2010, 01:35 PM

Hi guys,

Slopps, the mini-horn you link to is a BLH, although it fires upward. The front wave and backwave from a single cone are always out of phase, unless and until you use a cabinet trick to get them in phase again. So the out of phase aspect is inherent in cab designs (except sealed, I guess!)

In the case of BR, I believe there is a phase reversal over a narrow band. In the case of BLH, usually you try to get the path length of the back-wave / back-horn to be an odd number of wavelengths of the effective xover frequency. You also need to take care regarding the distance of the horn's mouth to the front of the cone, just as you would in center-to-center spacing of woofer and tweeter.

What specifically are you trying to accomplish with the 2 drivers and horn? More bass output? It sounds like your second driver will be an FLH, and I'm not sure you're really getting more bass -- more efficient loading, yes. More bass (if that's your goal) -- I don't see that personally.

22nd March 2010, 10:45 PM	#1
slopps diyAudio Member Join Date: Feb 2010 Location: chicago	Will this cause out of phase? So I'm building a speaker enclosure with two small (3 inch) full range drivers from Fostex. I was going to create a single box with one of the drivers aiming out the front of the box and then create an 18 inch horn (similar to these) sticking out of the top of the box with the second driver placed inside of it (like a front mounted horn). Since one speaker will have 18 inches of space to travel up the horn before hitting the open room is this going to cause any sort of weird echo or sound strange or will it be fine?

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22nd March 2010, 11:29 PM	#2
picowallspeaker diyAudio Member Join Date: Apr 2007	Dear Slopps , you answered yourself . There are many more experiments you can do with two same drivers in a box. One is to make a dipole ,placing them back to back in a closed box (opposite faces of the box)and connecting the in anti-phase . Then a bipole ,by connecting them in phase. In the first ,size (internal volume) really isn't a matter ,because the air is pushed and pulled by the two membranes in sinchrony. Geometry of the cabinet and size indeed are important ,for the many interactions of front and rear waves. Or just put them nose-to-nail ,bare ,with four long screws-barrels to keep them firm,close and parallel ,connected in phase of course...in this way I don't know what happens but it's nice ( maybe some harmonic cancellation)and a subwoofer is needed.

23rd March 2010, 01:35 PM	#3
rjbond3rd diyAudio Member Join Date: Jan 2007	Hi guys, Slopps, the mini-horn you link to is a BLH, although it fires upward. The front wave and backwave from a single cone are always out of phase, unless and until you use a cabinet trick to get them in phase again. So the out of phase aspect is inherent in cab designs (except sealed, I guess!) In the case of BR, I believe there is a phase reversal over a narrow band. In the case of BLH, usually you try to get the path length of the back-wave / back-horn to be an odd number of wavelengths of the effective xover frequency. You also need to take care regarding the distance of the horn's mouth to the front of the cone, just as you would in center-to-center spacing of woofer and tweeter. What specifically are you trying to accomplish with the 2 drivers and horn? More bass output? It sounds like your second driver will be an FLH, and I'm not sure you're really getting more bass -- more efficient loading, yes. More bass (if that's your goal) -- I don't see that personally.

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