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Review and Measurements of Benchmark DAC3

etc6849

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Can you add multiple subs and cross the speakers to the subs at 80Hz or 100Hz? Multiple subs throughout a room will fix your SPL issues and will negate needing to use that much EQ.

I kept adding subs to my room until I had +/-5dB with no EQ at all. It took 5 subs for me, but hopefully you are luckier. I also have 13 bass traps and absorption at first reflection points for a 5.1 system.

My subs are each time aligned and level match at the main listening position, then get summed together. My theater is using 3 Xilica XD4080 speaker processors, and I send digital AES to them from my PC (only playback device) using an RME HDSPe PCI-E card. I could use Dirac on my PC, and the PC software version lets you set the attenuation if I remember right.

Thanks for your response and no I do not mind.

Speakers are 3 way. Crossover points are 500Hz and 6kHz at -12 dB per octave.

I wondered myself regarding the phase/ linearity.

Can try swapping speakers while I re-measure - but I suspect corner v open wall is the culprit.

Mic has calibration file and I use the 90 deg version (not that it seems to make much difference with MMM).

My method is to measure, create a PEQ filter in REW. Then mount that filter in the respective channel of the miniDSP SHD Studio, and run the DIRAC measuring process. So presumably the PEQ is upstream from DIRAC because the measured responses DIRAC generates are much different with PEQ then without. It seems by popular opinion and measurement that this gives the best results with DIRAC if your room is quite bad. A valid argument has been made that excessive correction places demands on other areas of the system which may be net negative. Unfortunately all I can do is try the alternative method and see what the difference - if any - actually is.....
 

anmpr1

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I kept adding subs to my room until I had +/-5dB with no EQ at all. It took 5 subs for me... I also have 13 bass traps and absorption at first reflection points for a 5.1 system.
I don't think I've known anyone with five subs. I've never heard a system with that kind of bass power. I think five would be a lot for most people, but I understand your argument about minimizing EQ.

Out of curiosity, what program material do you find that necessitates the use of five subwoofers? I take it from your post that it is mostly movies and sound effects?, or is it helpful for music? If so, what sorts of recorded music are best enhanced by this setup? Is your room particularly large? Thanks in advance.
 

etc6849

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I don't use the subs anywhere near their rated power; I understand some might though. I am after absolute accuracy in sound reproduction.

I use five subs because more subs substantially reduces measured THD at the main listening position (MLP). Concurrently, it greatly helps get rid of any influence a small listening room makes even when no bass traps are used.

This plot is with no EQ. The slight slope is on purpse and I am using FIR filters for all speaker XOs, and the subs where I use a bessel XO. The difference is night and day compared to an ordinary setup with double digit THD measured acoustically at the MLP; usually measured around 10-20% at 30Hz vs .3% for my setup. THD improves as shown at 80Hz measuring .131% while most systems will still be double digital distortion or high single digit.

I would go as far to say that there is no comparison to any setup you have heard. The bass will be audibly more accurate. If you have an accurate drum recording, it absolutely sounds like someone is playing the drums.

FR THD 30 Hz(1).png


Front Right THD at MLP No EQ 10.28.2018 80Hz(1).png


I don't think I've known anyone with five subs. I've never heard a system with that kind of bass power. I think five would be a lot for most people, but I understand your argument about minimizing EQ.

Out of curiosity, what program material do you find that necessitates the use of five subwoofers? I take it from your post that it is mostly movies and sound effects?, or is it helpful for music? If so, what sorts of recorded music are best enhanced by this setup? Is your room particularly large? Thanks in advance.
 

Vasr

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I use five subs because more subs substantially reduces measured THD at the main listening position (MLP).
Is there a technical reason to support this? You are suggesting more subs decrease non-linear distortions? I am not an expert on this so would really like to know if this is true.
 

RayDunzl

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Is there a technical reason to support this? You are suggesting more subs decrease non-linear distortions? I am not an expert on this so would really like to know if this is true.
Each bass driver can play at a lower amplitiude, which typically reduces a speaker's distortion faster than the reduction in volume of the fundamental.

I have cheap subs assisting/duplicating the woofer in the mains.

The combination of three drivers on each side allows a 9dB reduction in the output of any one of the drivers.
 

anmpr1

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Is there a technical reason to support this? You are suggesting more subs decrease non-linear distortions? I am not an expert on this so would really like to know if this is true.
Generally, the louder a single speaker plays, that is, the more air it moves, the higher will be its distortion. By moving the same amount (or more) of air with multiple speakers than with a single speaker, I can understand how overall distortion would be lowered. Especially with bass since it's usually a non-directional thing. Multiple drivers mounted on a single baffle in a 'full range' loudspeaker can, however, result in different problems other than distortion at loud SPL. With subs, at their intended frequencies, you don't have the same problems that you could experience with a large-baffle full range loudspeaker comprised of a bunch of mids and/or tweeters lined up.

Certainly @etc6849 has gone to lengths to integrate multiple woofers into his listening room, evidently eliminating most typical subwoofer problems, and I'm pretty impressed on a 'theoretical and technical' level. I never thought about such a large-scale system (five subs), but would certainly like to hear it, or another like it. I am not convinced that on most acoustic music this sort of setup would offer a significant benefit over something simpler, but I am happy to be disabused about it.
 
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I don't want to go into too many details here as this has already derailed this thread for an outstanding product that I also own and love...

But, my post said multiple subs reduces THD and concurrently gets rid of unwanted room issues. Your post is only focusing on distortion from the speaker, and ignoring issues from small room acoustics (major contributor that should always be tackled first before buying new equipment).

I would encourage you to read the help files on this site then study the two charts below...
https://www.roomeqwizard.com/betahelp/help_en-GB/html/graph_waterfall.html

When I compare my setup to any I've heard, the ringing in the bass region versus what I'm used to is easy for me to hear. Note my setup has a decay time of ~120ms for a -45dB decay, and this is consistent for frequencies above 40 Hz. In case you are wondering, yes Dirac can improve this even more at the expense of digital headroom. I don't use an analog volume control, so I like the extra headroom though.

Here is the waterfall plot for my front right speaker crossed to the five subs with no EQ:
Front Right Waterfall No EQ 10.28.2018(3).png


A lot of systems have decays two, three or even more times what I'm showing above, and most plots will look very uneven in the decays too with ringing at several frequencies. Here is a random plot I pulled from the REW help file. If you look -45dB down from the localized peaks, you can indeed see ringing is 2-3 times my setup and very uneven.
1596498886824.png


The affect of multiple subs is well researched and there are multiple white papers if you look around on google. I also have a lot of room treatments too. Many of the best recordings I have already include echos from the space or venue they are recorded in, why add all the ringing in the bass region during playback that shouldn't be there as it's from your room? If you are ever near South Carolina, feel free to drop me a line. I promise you can hear the difference ;)

@anmpr1
 
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