Originally Posted by zheka
What does special averaging measuring technique have to do with seat to seat FR consistency?
The seat-to-seat consistency is really described by the deviation of a series of measurements. But one of the proposed approximations is to take an average of the measurements. I personally think the averaging procedure is less important than the mean deviation, whether done mechanically by physically sweeping the microphone or by taking a series of masurements and mathematically averaging them together. Averaging tends to tell power response and deviation tells seat to seat consistency.
Originally Posted by JackNC
I should have been more specific in my question about ceiling bounce. I'm contemplating a corner horn which sits on top of a direct radiator base bin or a base horn, such as the pi7 corner horn, and has no flanking subs. I don't see enough spatial separation for the direct radiator to fill in the null but, when I penned that question, I hadn't considered the path length of a corner horn, which add to the effective spatial separation. Ultimately though, there ought to be something I can do with a miniDSP equalizer on the woofer to introduce a peak at the null frequency to smooth out the null, at least for my own seat. The ability to introduce phase shift just at the null frequency would be nice but that isn't quite as simple as a PEQ term. (any suggestions?)
The calculated null in my geometry is 235 hz with the speaker centered at 3' elevation. Should I just lower the speaker 6" and raising the null.to 325 hz and then hope I get enough attenuation from the carpet and pad to make the null go away?
You're on the right track here, in my opinion. The way I handle this is to use the proximity to the apex of the corner remove any possibility of anomalies from the adjacent walls. The distance from midhorn to woofer and their overlapping band helps smooth the vertical anomalies, much like a truncated line array.
In fact, line arrays are what made me come up with the whole flanking sub / helper woofer approach in the first place. We were having those early multisub discussions and I also recalled how line arrays suffered no notch from ground reflection like a point-source speaker elevated off the ground does. So I tried a pair of drivers elevated off the ground and found this did a great job of mitigating floor bounce too. That's when I knew that the approach was effective.
So my suggestion is to put the woofer near the ground and the mid a couple feet up, overlapping them in the low midrange. That will mitigate the notch when it falls in the region of the band where the midhorn isn't directional enough to limit off-axis output. That's what my design does anyway.
Originally Posted by sdurani
I don't see Geddes talking about using subwoofer placement to achieve seat to seat consistency, instead choosing to measure/optimize at one location (unless he's changed his mind, yet again).
That's possible too. Geddes seems to shift around and change position sometimes. But the multisub configuration is (or should be) intended to reduce seat-to-seat variation and
improve smoothness of response, simultaneously. Otherwise, I see little point in going to the trouble to use multiple subs.
The conversations we had in 2005, and the internet discussions that followed it, were about using multiple subs for the simultaneous goals described above. You can see that in the threads. Geddes was pitting his approach against Welti's, and even bet me that his approach would do the same things and do it better. It did not prove to be true, which is perhaps why he decided to morph his stated goal.
If one decides to tackle just one problem by itself, they've reduced the problem to a much simpler one. Like I said earlier, if all you want to do is make the bass response really smooth indoors, get a nice sweep on a response chart, then just close mic the subwoofer. It will be as smooth as an anechoic chart. No need for multisubs at all.