Quote:
Originally Posted by
genesplitter
I have a few additional questions:
1) I removed the avr from the sim by setting min delay = 0 and max delay = 40 ms. Am I correct to assume this is not the same as min delay = -20 and max delay = 20? I initially wanted to remove the avr to keep things simple, but I'm ready to add it back in if needed.
They are not the same thing, that's correct. It's unlikely you'd need anything close to 40 msec delay, unless the sub distance were way off in the AVR. One thing you can do is the "Rearrange delays" command in the "Subwoofer channels" node of the Config View after doing an optimization. For N sub channels, this will make an equivalent configuration with one shared delay and N-1 individual delays. These individual delays can then be constrained to be positive, matching the available physical delays in the amps or DSP box. But the shared delay represents the AVR sub distance, so it can be allowed to have a negative value, corresponding to increasing the sub distance relative to the measured condition. I've found it makes sense to start with all individual delays first, then doing an optimization. Doing a "Rearrange delays" afterwards determines which sub channel will end up with zero delay (as the maximum number of delay blocks is N). If you do this, sometimes the delay limits are changed as this is sometimes the only way to get an equivalent configuration, so keep an eye on that.
Quote:
Originally Posted by
genesplitter
2) I ran an MSO sim with 8 PEQs per channel to max out the iNuke, but there was only a small improvement compared to 3 PEQs. I assume trying to optimize 5 positions needs more than 2 subs. Is there a rule? maybe N subs for N positions? I'm going to add a 3rd, IB sub into this setup over the Christmas break. I'll read up on how to model dissimilar subs later, but MSO should really help to combine ported and sealed/IB subs.
That's exactly right about the number of subs. I don't have rigorous mathematical proof, but there is for another sub optimization method, the matrix solution method with FIRs used in the old JBL BassQ. This is described in section 5 of
Welti and Devantier (equation (8)). Their matrix equation shows a 2x2 matrix, but it can be generalized to a matrix with M rows and N colums. The number of rows in the matrix is equal to the number of positions measured. The number of columns is equal to the number of subs with independent filter control. When these are equal and the matrix is non-singular, there is a solution. When the number of positions is greater than the number of subs, a least-squares solution is possible using the pseudo-inverse, but the more rows (measurement positions), the larger the mean-squared error. That's linear least-squares. MSO is nonlinear least-squares using an optimizer, but the basic idea is similar. Based on this, I'd say, "make the number of listening positions at least as large as the number of subs, but if it's made too large, the mean-squared error will increase."
Quote:
Originally Posted by
genesplitter
2) I have a 2nd system in the living room with 4 JBL 550p subs in the 4 corners. Unfortunately they are self-powered so I need a separate DSP. Is the miniDSP what most use? MSO help files warn not to buy the unbalanced miniDSP 2x4. Is there a preference between the balanced 2x4 or unbalanced 2x4 HD? My Marantz avr and jbl subs use RCA but I assume the balanced phoenix connectors can work with RCA too.
The only thing I don't like about the balanced miniDSP 2x4 is the maximum delay of 7.5 msec, which is limiting. It means more fiddling with MSO.
Quote:
Originally Posted by
genesplitter
Oh, and thanks again Andy for creating such amazing software. I can't imaging using multiple subs without using a tool to optimize their combined response.
You're welcome! Thanks for presenting your data. I was getting a bit worried that you found a bug. It would have been a pretty serious one. Also,
@
rumpeli
deserves the credit for finding out that the iNuke uses the RBJ convention for Q.