[Mikeyb]

I have a Titan II sub and the Subwoofer Setup CD provided by ACI.  Sorry for being too newbieish, but:

While playing the warble tones and using an SPL meter, how should the (in my case) A/V recevier be setup?  Should the mains be disconnected?

To get started, I just popped in the CD and played the tones using my receiver's "Direct" mode and all speakers connected (and configured small with a fixed 80Hz crossover).  This was 2-channel and includes the subwoofer (sub is configured as Sub Only).  In this case, I thought my receiver filtered out anything in the mains below 80Hz and sent it to the sub.  While playing the tones, it was evident the sub-80Hz tones WERE being played back through the main speakers (along with the sub).  Is this expected?

With this, my graph didn't appear too bad.  It showed about +/-2db from 60Hz to 120Hz.  But there was a peak of about +5 to +8db from 30Hz to 55Hz.  Where do I go from here?

Thanks for any input.

[Mike Dzurko]

While playing the warble tones and using an SPL meter, how should the (in my case) A/V recevier be setup? Should the mains be disconnected?

It depends if you are just trying to improve the response of the sub or integrate it into the system. Playing the sub alone is helpful if you're experimenting with subwoofer placement or doing EQ on the sub. Otherwise, you'll want the complete system playing so that you can get the best system balance.

To get started, I just popped in the CD and played the tones using my receiver's "Direct" mode and all speakers connected (and configured small with a fixed 80Hz crossover). This was 2-channel and includes the subwoofer (sub is configured as Sub Only). In this case, I thought my receiver filtered out anything in the mains below 80Hz and sent it to the sub. While playing the tones, it was evident the sub-80Hz tones WERE being played back through the main speakers (along with the sub). Is this expected?

Filters are not brick walls, they are a rolloff of frequency. Most rec have a 12db/oct rolloff below the turnover point. So you'll see the response diminishing at 12db/every octave below 80Hz. At 80Hz the main speaker response will be down approx. 3db. An octave below that they will be down about 15db, etc.

With this, my graph didn't appear too bad. It showed about +/-2db from 60Hz to 120Hz. But there was a peak of about +5 to +8db from 30Hz to 55Hz. Where do I go from here?

Your initial graph doesn't sound bad at all. Most rooms have several major peaks in the response. This will change somewhat with subwoofer placement. Additionally, moving your measurement microphone will change your measurements. You can trying using the filters on the subwoofer to knock down some of that peak. Try bringing one of the filters down, maybe even all the way down to 35Hz and see what happens. This is where you start to experiment to see the interaction of the filters, the phase and the subwoofer volume. Be sure to take time to listen to how the changes in settings effect the sound. I personally see this as a learning experience where the more time you take, the greater the rewards.

Ultimately, the best tool for really making that response flat will be the R-DES unit  which will very soon be released.

[Mikeyb]

Thanks Mike!

Very helpful.  I will play some more....

Additional questions:
How is a processors crossover point different from the hi-pass filters ACI offers?  Is it the rolloff (slope) that is different?

I think I have read where the 25th anniversary Sapphires have a rolloff that is different depending on the use of the port plugs.  Would you explain the difference (inserting them and not)?  I am assuming this rolloff would begin at the +/- 3db low point of 42Hz.  Is this correct?

Is there any correlation between the rolloff at the processors crossover point and the main speakers rolloff at it's rolloff point?  Does it matter if the slopes are different?

Thanks!

[Mike Dzurko]

Thanks Mike!

Very helpful.  I will play some more....

Additional questions:
How is a processors crossover point different from the hi-pass filters ACI offers?  Is it the rolloff (slope) that is different?

I think I have read where the 25th anniversary Sapphires have a rolloff that is different depending on the use of the port plugs.  Would you explain the difference (inserting them and not)?  I am assuming this rolloff would begin at the +/- 3db low point of 42Hz.  Is this correct?

There are really no standards for the filters in processors. Many do have 12db/oct slopes and commonly offer a choice of say 80-100-120Hz. They are active filters, meaning they generally use OP amp circuitry. Our passive filters use only resistance and capacitance and are 6db/oct filters. They are really designed for use in two-channel systems that do not already have high pass filters available.
Any ported speaker can be "plugged" and then becomes a sealed speaker. The ported speaker exhibits a lower F3 point with the cutoff at a sharper rate beyond that point (24db/oct). The sealed system has a higher cutoff with a shallower, 12db/oct cutoff. I have seen technical arguments about sealed vs. ported go on forever. You might want to do some forum searching or googling for WAY more than you want to know One thing, quite often, plugging the port yields an improvement in integration with a sub.

Is there any correlation between the rolloff at the processors crossover point and the main speakers rolloff at it's rolloff point? Does it matter if the slopes are different?

Another great topic for a book To quickly summarize to the two best choices;
1) One way to do it is to have the processor crossover one full octave above the true 3db cutoff of the speaker
or
2) Have the 3db point of the speaker at the same point as the cutoff point of the processor. This is why our Essence series, Veritas series, and Protege series are all designed for sealed, less than .7 Q, rolloff at 75Hz. When you add this to an 80Hz processor cutoff, you get a perfect 4th order rolloff which is VERY effective.

Great questions!

[Mikeyb]

Good stuff!  Thanks Mike

[Mikeyb]

Another question:

The Subwoofer CD instructions say to aim the db meter at the main speakers.  I have read other calibration instructions that say to aim the meter at the ceiling.  When the instructions say "aim", does that mean the tip points at the disired direction, and if at the main speakers, the meter would be lying on it's back with the display facing the ceiling?

For 5 or more channels, is it then appropriate to point the tip at the ceiling?

[Mike Dzurko]

Another question:

The Subwoofer CD instructions say to aim the db meter at the main speakers.  I have read other calibration instructions that say to aim the meter at the ceiling.  When the instructions say "aim", does that mean the tip points at the disired direction, and if at the main speakers, the meter would be lying on it's back with the display facing the ceiling?

For 5 or more channels, is it then appropriate to point the tip at the ceiling?

It seems that the best results are with the meter pointed up.. I rarely use the RS meter as I have other equipment. If I get the chance, I'll try to do a compaison vs. a calibrated mic to see where it should best be aimed. In the meantime, you're safe aiming it up.