Axiom Home Page Forums General Discussion Advice from Axiom Owners Mixed Dual Sub system

John,
Thank you for a great explanation (justification) for using more than one sub. The article is fairly short but illustrates that using up to 4 subs can minimize variation of FR from one location to the next within the seating area and helps to minimize the variation of overall FR within the seating area. By the way, the study is on only one low frequency audio channel sent to all the subs. They mention that there is "questionable" advantage to having stereo or more bass channels/subs. My processor does not create a stereo LFE output to two subs, but it has the capability to redirect bass from the left main and left rear channels into a left subwoofer and redirect bass from the right main and right rear channels into a right subwoofer while giving the same LFE signal to both. Since separate bass channels is of questionable benefit, good news is that I can use the same SMS-1 to run 2 EP-500s if needed.

PS: John, in reply to your comment about the only processor that allows for stereo subs and a separated LFE only output being the Lexicon MC12. My processor is identical to MC-12 in this regard with 3 sub outputs, one for LFE, two others for L and R channels for redirected bass +/- LFE. In essence, I don't have to set the low-pass to 40Hz to hear more stereo bass from the mains since the 2 sub channels in the processor can run two subs in stereo.
John

Nice processor, John, . I thought only the Lex had that feature. Which one do you have?

John, it is the Yamaha DSP-A1, now several years old but still running strong. It has 3 subwoofer outs (2 for stereo subs and 1 for mono) with custom bass management options for LFE and redirected bass for all 3. In addition, the subwoofer output levels for DD and DTS can be set individually, meaning that when DD signals are being processed, the LFE out can be set to have one level, and when DTS signals are being processed, the LFE output can be set to a different level. The two levels are stored and automatically recalled when playing one format or the other. This is potentially useful since DD apparently has an LFE output that is 10 dB above the main signal, as recommended by Dolby. In my case, I decided to keep the same subwoofer level between DD and DTS soundtracks. Despite all of these wonderful features, I think it will soon be time to upgrade.
John

I would think that DTS has the same 10dB boost. The receiver makes the adjustment as the line signal doesn't have the extra 10dB of headroom above the other channels. This is just because LFE effects were designated to be much louder than the other channels. This is just my opinion, as I have not noticed a large difference in LFE volume between the two types of encoded soundtracks.

Dave,
I think the DD spec of 0dB for LFE channel is actually +10dB relative to other channels. For DTS, equivalent setting is +10dB for the LFE. The recorded signal has been attenuated on incoming signal to allow more headroom when large explosions and such take place. Yamaha DSP-A1, Casablanca Theta processor, and perhaps some others that came out around '98 had the ability to set different LFE levels for DD and DTS. I keep DD at 0dB and DTS at +10dB and adjust the LFE from spekaer level menu during calibration, which then automatically adjusts both DD and DTS levels by the same amount. It may not be a bad idea for a processor to be able to adjsut LFE for DTS and DD separately since there is some inconsistency among various music and movie sound tracks; for instance, some have reported that early DTS music tracks require the +10dB setting whereas the later ones require the 0db setting.
John

Yes John, flexibility is always best as there are many variances among source content out there.