Wayne Parham Messages: 18782 Registered: January 2001
Illuminati (33rd Degree)
Physical position of midrange and tweeter drivers is sometimes offset to get the summing right. It's kind of similar, except in this case, the goal is to match the phase of each subsystem.
In multisub setups - both flanking and distributed - we're actually going the opposite direction. Since we know we can't match phase of all reflections, we're trying to smooth the anomalies using dense interference.
So the goal of driver baffle offset is phase-related, but it is an attempt to match phase to reduce interference. The goal of mutisubs is to increase interference.
Wayne Is there an explanation why zero delay was flatter then most other options I tried? Any delay configuration I tried just moved the dips somewhere else in the response?
One thing I did try before I got my new amp was to change the mains distance to further away then the real distance /auto setup suggested distance,as I think because the sub goes through eq and sub amp it's probably behind the mains in arrival time? And delaying the subs only made this gap bigger, I know this is not the idea behind multiple subs, but from memory it may have helped raise the dip slightly in the 100hz area... I need to try it again with the new amp, I just did auto setup for distance etc.
Wayne Parham Messages: 18782 Registered: January 2001
Illuminati (33rd Degree)
Delay is equivalent to making the distance further in one dimension. So naturally, this changes the frequency where self-interference cancellation happens.
The thing is, our goal is not achieved by this. We need to create dense interference by increasing the number of sound sources to mitigate the anomalies caused by boundary reflections.
I remember earl geddess suggesting having adjustable Phase knobs on the back of subs in a multi sun set up, so presumable like you say you can move the points in the frequency where the cancellations happen to help smooth the response.
Wayne Parham Messages: 18782 Registered: January 2001
Illuminati (33rd Degree)
You can manipulate electrical phase and/or delay, certainly. I'm just saying that it's pretty limited in what you can accomplish with that. The better solution is to set the delay with position in 3D space.
johnnycamp5 Messages: 354 Registered: June 2015 Location: NJ
Grand Master
Wayne Parham wrote on Sun, 17 July 2016 16:31
You can manipulate electrical phase and/or delay, certainly. I'm just saying that it's pretty limited in what you can accomplish with that. The better solution is to set the delay with position in 3D space.
How important is sub enclosure shape?
Lets use a 40"x40"x40" cube as a huge example.
Instead of a cube, could one build sub enclosures tall and thin, for example- 40" wide x 80" tall x 20" deep?
This does not change internal volume.
This example could locate both the subs and mains approx. 20"s closer to the front wall vs. a typical 40" box.
While maintaining the mains and subs offset in depth, could this be acceptable?
You can manipulate electrical phase and/or delay, certainly. I'm just saying that it's pretty limited in what you can accomplish with that. The better solution is to set the delay with position in 3D space.
Did welti use electrical phase/delay or just 3D space? is that another way geddess and welti are different, aside from the symmetrical vs random?
Wayne Parham Messages: 18782 Registered: January 2001
Illuminati (33rd Degree)
Subwoofer cabinet shape isn't really important because the cabinet is acoustically small. Standing waves cannot setup inside.
Welti started off doing just position but later added equalization. Geddes proibably followed suit. It's an Nth degree thing - The biggest improvement comes from using multiples and placement, but equalization is also useful to a lesser degree. Nobody would advocate equalization in lieu of multiple subs, but once you already have multiple subs, it is potentially worthwhile to equalize for an incremental improvement.
Wayne can I ask how important you feel phase is between the drivers in a speaker?
The manufacture of my speakers feels this is crucial and much more important then flat amplitude.
If you also feel this is crucial can you explain why the phase between flanking subs and the mains doesn't seem to matter and we don't hear that there not in phase?
Is it because of the frequency flanking subs operate in?
I hope it makes sense what I'm asking.
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