The "Official" xtz Room Analyzer Thread - Page 10

OK, there's the misunderstanding.... The RX-Z9 has dual subwoofer outputs and they can be set up as "Monaural", "Front/Rear" or "Left/Right". I can find no explanation of what the processing does for the different settings, but they are available. I don't know if the "Stereo" setting retains separate signals for the L & R subs, or if it runs them together. Either way, the way you have them placed, there is little benefit to "stereo" subs, so I would run them as "monaural" subs.

You can also set the Distance for each sub separately, but using the monaural setting simplifies things because you set the the Distance of both subs at the same time. If they are equidistant to the LP, it shouldn't matter..

Here's what I would do:

Reset the processors in the DD subs. This will erase all the EQ settings and set all the other settings back to baseline.

Connect one sub to the RX-Z9 and set the Z9 to "Monaural" subwoofer. Connect the 2nd sub to the first one via the "daisy-chain" method. This will gain-match the subs and allow them to be EQ'd as a single sub, which is how you "hear" them. Place them so they are equidistant to the LP.

Run YPAO.

When YPAO is done, set the crossovers for your speakers to 80 Hz for your mains and to whatever is optimal for your surrounds, (you don't list surrounds, so I don't know what they are.)

Measure the response with XTZ, being especially aware of the response at 80 Hz. Adjust the subwoofer Distance setting to optimize the response around the 80 Hz crossover point.

Run the manual EQ in the "Master" DD sub. This will EQ the combined response of both subs. You can try the EQ recommendations that XTZ suggests, but when I had an SMS-1, I didn't find them too useful. I found it easier to just do the EQ using the SMS-1 software.

This should provide smooth, flat response all the way up through the crossover.

Craig

If the goal of "true stereo subs" is to realize stereo separation of the bass, I suggest the subs be placed outside the left and right main speakers. With them inside the speakers, they are probably too close together to yield good separation. How far apart are they?

However, I'm not sure that the way you have them set up in the receiver will yield "true stereo bass." I don't know if that is what the L & R subwoofer outputs and the "Stereo" setting does. I could find no explanation of those settings anywhere. Usually when you set up "stereo bass", you use the L & R main channel outputs to drive the subs, (or you wire them at speaker level.) That way the L & R signals a fully maintained separately into the subwoofers. Then you turn off the subwoofer outputs in the receiver and do all the Bass Management at the subwoofers. The way the RX-Z9 is set up is unique in my experience. It would be interesting to see what happens to the LFE channel and the re-directed bass when the system is set up the way you ahve it set.

The other point about "true stereo bass" is that there is significant controversy about whether humans can actually hear stereo separation at low frequencies. Some claim they can hear separation down to 40 Hz. However, with an undistorted signal, (no harmonics in the signal), most humans lose the ability to localize sound at about 80 Hz. So, if you're like most humans, "stereo Bass" below 80 Hz is not going to be a benefit. The benefits of monaural bass will far outweigh the "benefit" of stereo bass.

To get this thread back on topic, can you post some XTZ measurements of your speakers and subs in their current configuration?

Craig

These full range measurements are not helpful for setting the Distances. You need to run the speakers and subs *together* in order to check the blend of their outputs at the crossover. The Distance setting is actually a "timing" setting. The Bass Management system looks at the Distances and uses them to set delays. For example, if the sub is the furthest away, it will "fire" first, and the speakers will be delayed relative to the sub. The goal is to have all the waves from all the speakers and sub(s) arrive at the LP at the same *TIME*.

Why is this important? If the waves arrive at different times, then the waves will be out of phase. If the negative side of one wave arrives at the same time as the positive side of another wave, they'll cancel each other and there will be no sound. I showed a graph of this phenomenon on the previous page. Here it is again:



The blue trace shows the cancellation cause by the out of phase arrival of the waves from the subs and the waves from the speakers. The green trace has had the subwoofer Distance adjusted so the delays are correct and both waves arrive in-phase with each other. The cancellation is gone.

The crossover in these traces is 80 Hz. The cancellation happens because both the speakers and the subs are generating 80 Hz. Above 80 Hz only the speakers are generating sound, while below 80 Hz only the subs are generating sound. The crossover filters are not hard "brick walls", but instead they have slopes. You can see the slopes in the response a little above and a little below 80 Hz.

Here is another system where the subwoofer Distance setting was much better to start with. Still, with some adjustment, I was able to get another 5 dB around the crossover frequency:



Above I suggested some steps to optimize your system. Two of the steps were:

When I suggested measuring the response with XTZ, I meant to use the Room Analyzer screen to check the response around the crossover. YPAO will have set the Distances, including the subwoofer Distance. Use that as the starting point. Then try adding some distance to the subwoofer and see if the response improves. If it does, add a little more, continuing until you get the highest response at the crossover frequency. If you can't get it all the way up to "flat", you can then try using some boost in the DD software, but you should always try to get as close to flat first before adding any boost.

Here's a question: When you run YPAO with the subs set to "Stereo", does YPAO chirp the subs separately, or together? Or, does it chirp the subs separately... and then also chirp them together?

Craig

I found this: If this is indeed the case, the RX-Z9 does have a unique Bass Management capability. Still, just because one has this unique capability doesn't mean it is best to use it. I still think there are significant benefits to monaural bass reproduced by multiple subwoofers placed separately around the room.

Craig