power alley question: If I were to lay the keystone cabinets on their side on the ground, how far would I need to move them apart to counter the power alley effect? from the online calculations that I've seen it looks like around 9 feet apart. but is that measured from the center of the box or from the largest part of the keystone opening where more of the air comes from?
Moving cabinets apart creates the "power alley" effect of +6dB down the center with lobes at frequencies dependent on the distance of separation.
To avoid the power alley place all your subwoofers in a single location.
For modeling purposes you could use the center of the box for calculation.
https://www.fulcrum-acoustic.com/wp-content/uploads/2019/10/3_The-Subwoofer-Power-Alley-1.pdf
To avoid the power alley place all your subwoofers in a single location.
For modeling purposes you could use the center of the box for calculation.
https://www.fulcrum-acoustic.com/wp-content/uploads/2019/10/3_The-Subwoofer-Power-Alley-1.pdf
That's what I normally do, but I just watched a video where the guy was explaining how to calculate how far to move the cabinets away from each other to limit the beam effect and get more of a round coverage. I saw some information on it from a company that sells PA stuff. I want to say it was somebody like nexo. There are some calculation for it to know the distance based on the upper cut-off frequency. According to those measurements, I can put the cabinets 9 ft apart. But they're talking about 9 ft from each center. The keystone doesn't exactly put out bass from the center. It actually sucks in air at the top of the port and pushes it out the larger part. That's what we experienced when some guy was holding a shirt in front of the cabinet watching the air blow. Lol
I've been doing a lot of related research lately, but for how to best set up a fairly small system. (Dave Rat primarily focused on various setups using eight subs, of varying designs.) One very interesting thing I saw in a Youtube video seems to relate directly to Singtall's original question:
The idea is that, instead of a wide center sub array made up of lots of subs, you can achieve somewhat the same narrowing of the horizontal dispersion by simply using two subs and pulling them apart. Theoretically this distance has to be 1/2 the wavelength of whatever frequency you deem most important. I figure that's a kick drum fundemental, which is typically about 50 Hz or higher. So we're talking about 2 subs roughly 14 feet apart.
And that raises what I thought was Singtall's question:
How far apart can you go before you start getting power nulls in the operable frequency range?
I searched and searched, but couldn't find an answer.
Does anyone know?
The idea is that, instead of a wide center sub array made up of lots of subs, you can achieve somewhat the same narrowing of the horizontal dispersion by simply using two subs and pulling them apart. Theoretically this distance has to be 1/2 the wavelength of whatever frequency you deem most important. I figure that's a kick drum fundemental, which is typically about 50 Hz or higher. So we're talking about 2 subs roughly 14 feet apart.
And that raises what I thought was Singtall's question:
How far apart can you go before you start getting power nulls in the operable frequency range?
I searched and searched, but couldn't find an answer.
Does anyone know?
Easy to model - ASSUMING the setup is outside with no reflective boundaries (ie walls) nearby.
Here's 2 subs at your suggested 4.2m spacing at 50, 63, 80 & 100Hz.
As the interactions are wavelength dependant, we can see that once we are an octave above the target frequency, the main lobe of the coverage pattern is ~half as wide and the side lobes are substantially larger.
HTH,
David.
Here's 2 subs at your suggested 4.2m spacing at 50, 63, 80 & 100Hz.
As the interactions are wavelength dependant, we can see that once we are an octave above the target frequency, the main lobe of the coverage pattern is ~half as wide and the side lobes are substantially larger.
HTH,
David.
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I have some chinese Lase 18" drivers. they are a rcf lf18x451 clone. Currently I have them loaded into reflex cabs tuned to 30hz but the output that low just does not seem to be there. I don`t have a way to measure them but I think I saw in the past @weltersys is in deland fl which is about 20 min away from me. I am hoping he can help me measure these or discuss if they would work good in the keystone to get me down low. I have attached the Basta prediction with the drivers advertised T/S. I have heard that drivers do not go well below Fs and also Heard that it does not matter, Please HELP!
Hope you can measure the real T/S parameters, there is a device that cost around 150 that can help. Don't remember the name but you can measure the real T/S of a given driver...just a side note ,even brand name drivers sometimes deviate more than the adequate from the published specs, I guess the Chinese drivers QC is not that much tight so no wonder you don't have low end in your enclosure
Mark,
I'm living in Santa Fe NM now, so the drive would be a lot more than 20 minutes
Output drops considerably when a cabinet is tuned as low as 30Hz- the Keystone Fb is around 36Hz.
If you really want to get down to 30Hz with efficiency, the cabinet has to be big.
The LASE LF18-3600 18" has a 4" voice coil, the RCF LF18x451 has a 4.5" voice coil, so without going much further we can assume the TS parameters won't be the same.
If you have valid TS parameters for the LASE 18", you could plug them into Hornresp and see how it compares to other drivers.
Art
I'm living in Santa Fe NM now, so the drive would be a lot more than 20 minutes
Output drops considerably when a cabinet is tuned as low as 30Hz- the Keystone Fb is around 36Hz.
If you really want to get down to 30Hz with efficiency, the cabinet has to be big.
The LASE LF18-3600 18" has a 4" voice coil, the RCF LF18x451 has a 4.5" voice coil, so without going much further we can assume the TS parameters won't be the same.
If you have valid TS parameters for the LASE 18", you could plug them into Hornresp and see how it compares to other drivers.
Art
Based on your published specs, near enough dead on for a T/S max flat alignment : Vb = Vas, Fb = Fs, so tuned too low and assume the box is too big.