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SME

My living room "make over" (aka the "surrounded by bass" project)

155 posts in this topic

So lately, I've probably been enjoying my existing system too much and not spending enough time working on my subs.  I've continued to make very minor tweaks to the system.  The biggest change was to back off on the boost to 190 Hz on the center channel and instead make it ~flat "on-average" across the seats.  This is mostly because I often sit off-axis, and it didn't sound so good in those other spots.  The excess 190 Hz tended to overwhelm and mask out a lot of detail in voices whose fundamentals hit that spot.  It is an acceptable compromise until I extend the baffle.  The center still sounds very good, and it's nice to not have the weird feeling (literally) that arose from the build-up of later arriving energy at that frequency.

 

Otherwise, I boosted my sub bass response a bit, giving it a bit of an upward tilt.  I think the "first arrival determines tonal balance" concept doesn't apply in the same way to bass because room gain tends to naturally boost even first arrival sub bass in most situations.  An anechoically flat speaker will typically run hot in the bass without EQ adjustment, and that's often just the way things are monitored.  Instead, I've opted to adjust things by ear, and a few extra dB with some slope up toward the bottom seems to sound better.  There is a very clear point where too much low end washes out much of the transient detail.  Kick drum might go boom but not really thump, and bass instrument can sometimes go from being punchy and well-defined to indiscernible sludge.  If I raise the response to that threshold and then back-off about 0.5 dB, repeating this process for different regions of the response, I get a very solid, satisfying thump with no overhang from most kick drum.

 

Where I've struggled more is with taming the high end.  Running the top end flat just doesn't work for my ears and for most others.  In fact, it can be very irritating with a lot of content that I think most would regard as being well recorded.  What I'm finding is that the shape of the roll-off is to an extent more important than the amount of roll-off involved.  Very minute changes to the shape can have a big impact on the sound.  At the same time, content is quite variable in overall top octave strength, so I feel that having an adjustable UHF control will be advantages. 

 

I recently decided to experiment with a hypothesis that the best roll-off shape will almost approximate the roll-off caused by dissipation of sound as it moves through the air.  I was surprised to see that dissipation is actually pretty significant even over short distances for the highest frequencies.  After reviewing data of UHF roll-off vs. distance at various humidity levels, I settled on simulating distance roll-off via a single biquad centered at 12750-13000 Hz (higher for greater roll-off amounts) with a Q of 0.5 and gain ranging from 0 to -10 or so, approximately equivalent to roll-offs due to distances ranging from 0 to 20 meters or so.  With most content, I seem to do well by about -3 dB or ~6 meters of distance and occasionally opt to push it out to -6 or -10 dB for ~12 meter or ~20 meters of distance.  The consequence of adjusting the roll-off while maintaining the constraint of physical realism is is remarkably subtle.  It kind of acts like the audible equivalent of a sharpness control.  Too much, and the transients have a bit too much bite.  Too little, and there is a loss of fine detail as well as crispness.  These changes are very subtle, even compared to say boosting 15-20 kHz by 1 dB *without* altering the frequencies below and thus ending up with a physically unrealistic curve.

 

Along these lines, it's very fascinating to me that UHF and very low frequencies can mask one another substantially.  For a few hours, I accidentally had 15-20 kHz and up running about 1 dB hotter than I meant to run it, and it caused much of the sub bass to sound very distant and lose almost all of its weight and feeling.  But it only happened on certain soundtracks, those with full extension.  I was really weirded out until I recognized that it was the UHF that was masking the bass and causing it to diminish.  I tried pushing the subs up 3 to 6 dB, and it did nothing for its subjective loudness or power and merely muddied the sound.  Without fixing the UHF, there was no helping the bass.  Bringing the UHF to proper balance totally fixed the problem completely to my great relief.  I have also observed masking in the other direction.  When I had some harshness in the UHF, boosting around 45 Hz or so seemed to quell it considerably, even when I couldn't conciously hear any content down there.  Psychoacoustics are very weird.

 

Another thing I encountered when playing with UHF response and ending up too hot in parts was a sort of unrealistic hyper-detailed sound.  I haven't seen a Darbee before, but I imagine it to be the audio equivalent of turning the Darbee effect up way too high.  Upon first impression, the sound is incredibly enhanced, with far more richness and detail than is heard normally, but only upon more careful disciplined listening does it become clear that the sound is completely inaccurate and unrealistic.

 

At this point, I am declaring this experiment a success.  The sound seems to have improved by another notch.  Cymbals and hats sound absolutely great.  Indeed, I'm hearing cymbals emerge in background content of soundtracks where I never heard them before.  And there's even less harshness than there was before.  For the occasional soundtrack that still "bites" a little, I can easily dial-down the UHF without losing detail or weirding out the tonal balance.

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I tend to agree with much of the above. I tried a ruler flat on axis response outdoors and at the LP in smaller rooms a few times and neither sounds good to me. The top end is subjectively too much for my tastes. Sounds unnatural and the low end sounds anemic. This was especially true for the LF outdoors. I assume it is from the lack of direct vibrational queues, or other types of coupling with the body directly, that are much more prevalent in a vehicle or small room, that might help fill in the LF experience. Overall I prefer a bit of a downward tilt from the bass to the treble range, with the bass becoming a bit more aggressively boosted below 100hz. Most of my friends who are not very technically savvy when it comes to acoustics or speakers seem to agree with that type of general shape as well. Maybe it's technically a coloration preference but whatever. At the end of the day it is all about enjoying your music or movies isn't it?

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Good posts :)

 

I smiled at the first part, though - it does seem as though sometimes the tweaking time overtakes the actual time spent just playing content for fun!

 

I tend to like the presentation of mine, but I'm just running Audyssey for processing.  Perhaps one gets to like what one is used to until one is presented with something that is better?

 

I do take my hat off to everyone who spends so much time improving their system - I've still not got round to putting the MiniDSP (which I bought about 18 months ago) into the system, and I really must do it soon before I have to move out and back into the missus' dad's house so we can save for a bigger place...

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I added a discussion along with some in-room response measurements of my system, as it was last time I measured, to the first post of this thread.  (Scroll down to the second section.)

 

I tend to agree with much of the above. I tried a ruler flat on axis response outdoors and at the LP in smaller rooms a few times and neither sounds good to me. The top end is subjectively too much for my tastes. Sounds unnatural and the low end sounds anemic. This was especially true for the LF outdoors. I assume it is from the lack of direct vibrational queues, or other types of coupling with the body directly, that are much more prevalent in a vehicle or small room, that might help fill in the LF experience. Overall I prefer a bit of a downward tilt from the bass to the treble range, with the bass becoming a bit more aggressively boosted below 100hz. Most of my friends who are not very technically savvy when it comes to acoustics or speakers seem to agree with that type of general shape as well. Maybe it's technically a coloration preference but whatever. At the end of the day it is all about enjoying your music or movies isn't it?

 

As per the discussion in my first post, there's a world of difference between flat *first arrival* frequency response and flat frequency response in a typical listening room.  I'm fairly certain that this is why a frequency response with significant slope sounds better indoors.  As for outdoors, I would expect a flatter looking response to sound better, albeit with some high frequency adjustments and some bass boost.  I already discussed the reasoning for high frequency adjustments in my first post.  I did not discuss the bass boost however.

 

I believe I've stated this elsewhere before, but I believe bass boost may actually be more correct.  The reason is that a typical monitor with flat anechoic response will exhibit room gain in a typical listening space, even for the so-called first arrival.  In the early days of audio, this room gain was probably never compensated for in the monitoring systems.  Instead, the room size and speaker placements in the mastering studio were chosen to be approximately representative of listener's homes.  Even today, room gain is likely not compensated for directly.  Instead, a lot of mixers will adjust the bass response of the monitoring system by ear until it sounds good, using trusted recordings for guidance.  In other words, bass boost is established by precedence, just like high frequency adjustments are.

 

When you say that you and most of your friends prefer the response a certain way, it's probably not because you prefer a colored sound.  Sure, there are people that prefer to play their subwoofers as loud as possible so they can experience their eyes wobbling and struggle to breathe.  That's a special case, where extreme bass at the expense of the rest of the sound is enjoyed as sort of a sport.  But when it comes to fully appreciating real world music and movie content, outside of a few dedicated "bass" genres, I believe preference is a lot less subjective than we are commonly led to believe.  The sound that you and your friends prefer to listen to may be a lot closer to what the mix and mastering engineers heard than you would think.

 

 

Good posts :)

 

I smiled at the first part, though - it does seem as though sometimes the tweaking time overtakes the actual time spent just playing content for fun!

 

I tend to like the presentation of mine, but I'm just running Audyssey for processing.  Perhaps one gets to like what one is used to until one is presented with something that is better?

 

I do take my hat off to everyone who spends so much time improving their system - I've still not got round to putting the MiniDSP (which I bought about 18 months ago) into the system, and I really must do it soon before I have to move out and back into the missus' dad's house so we can save for a bigger place...

 

I've put an enormous amount of time into tweaking, and I believe it's really paying off for me now.

 

I liked Audyssey MultEQ XT while I used it, but I now consider it to be seriously flawed.  Unless one's room is acoustically dead, it yields a very top heavy tonal balance.  Admittedly, I didn't realize this is for at least a couple years.  It certainly improves the sound in some aspects, but these improvements come at great cost with respect to other aspects.  Once I got the Pro kit with the adjustable target curve, I figured out how wrong flat was, but unfortunately, the Pro kit was too limited (+/-3 dB max difference in the target curve) and too tedious to use for me to find an optimum target curve.

 

I've heard that XT32 uses a completely different algorithm, but I'd hazard a guess that the result is still very top heavy.  Audyssey makes many claims that their system leads to a "reference" response, implying that a flat frequency response (with a tiny bit of top end roll-off) allows one to hear what the mix/mastering engineers heard in their studios.  Audyssey also claims that if one does not like the flat sound, then he/she has a preference that is inconsistent with the reference response.  These claims are totally wrong, and I'm not sure if anyone at Audyssey actually knows any better.  It's really quite absurd, because despite all of the psycho-acoustic research that supposedly goes into their technology, their approach appears to be based on a flawed understanding of how hearing works and a flawed understanding of how mixes are produced.

 

Definitely get that MiniDSP unit up and running.  Are you going to use it for your mains or just your subs?  Either way, I suggest using the MiniDSP exclusively for EQ and turning off Audyssey.  If your speakers are decent, they should have a much nicer tonal balance than what Audyssey gives you, and if you have EQ capability for them with the MiniDSP, then you can fine tune them as needed.

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I recently migrated bass management from my AVR to my custom DSP.  This will allow me to do BEQ correctly and to do more powerful room EQ when I get there.

 

I've mentioned in the past that I found calibrating "first arrival" flat sounds best, with some exceptions.  One of those exceptions is the apparent need for a shelf of -1 dB centered in the upper mids for some music.  However, I'm trying a different approach now using a bass boost instead.  The idea is that an anechoic flat speaker has a bass boost from the floor reflection that shows up somewhere in the low mids or upper bass, depending on the design of the speaker and listener distance.  The boost is roughly in the range of 3.5-4.5 dB or so, and I make the center frequency of the boost adjustable to account for different mastering environments.  I'm still doing a lot of experimentation and listening, but moving the center frequency of the boost a bit higher seems to work well (as in sounds good) in lieu of the upper mid shelf.  It's not perfect, but I don't know if it ever will be.  A real floor bounce also has a dip in first arrival sound that appears above where the boost sets in.  Should I simulate the response dip too?  I'd rather not, especially being that its location, shape and depth will vary a lot more in different environments than the boost will.

 

So I'm pretty happy with how my music sounds.  However, I've been recently reminded that cinemas and dub stages are usually calibrated so that in-room power response follows the X curve.  Because of this, some movie content needs the X curve applied to the highs to sound right.  Some also seems to need an extra bit of upper mid cut, perhaps because some room reverb may be present there.  It depends on the room.  Making matters worse is the low frequencies.  In a dub stage with a lot of bass build-up the mains may be calibrated with a lot of attenuation down there in order to keep the power response flat.  As such, the bass boost I use is likely inappropriate for a lot of films.  At least its presence is less likely to be offensive than the lack of X curve where it's needed, but the bass boost may cause some boominess in some of the voices.   To make matters weirder, I actually need that bass boost in my calibration in order for my near-field subs to give me the same SPL as my mains via pink noise.  So is my bass boosted or not?

 

Needless to say, the cinema standard is a disaster for good sound.  The existence of home mixes just throws another wrench into the works.  Do they calibrate to a target curve or do they let the monitors run as they are designed (i.e. flat anechoic)?  Unfortunately, the one example of a home mix I'm aware of is very irritating without a -3 dB high shelf in the upper mids, and the voices are boomy unless I disable my bass boost.  I have no idea how they calibrated their system, but clearly it produced a mix with a very different tonal balance than most music.

 

It's now abundantly clear to me that the only way to get high end sound with a wide variety of movies is to re-EQ them as needed, and not just to restore filtered bass.  Right now, I must make the EQ changes manually, which is disruptive when trying to watch movies, but in the long run, I plan to implement a handful of enlightened tone controls that I can adjust remotely while a movie.  I could use this for music too, where I'd like to be able to adjust bass boost center frequency and UHF/distance roll-off amount more easily as well.

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