Seat to seat consistency for bass...(sharing and how-to)

It has been a long time since I post any tutorial. This one is a fairly easy one and is most overlooked by many HT enthusiasts. Most of us know getting good sound or bass at the MLP (golden seat) is relatively easy when you are the one occupying the “emperor seat” but did you know the bass can get a bit uneven even though the graphical frequency response showed a perfectly flat curve. If you don’t believe me, play some music or movie soundtrack with some good bass effect and try the left and the right seat and tell me whether you feel some “unevenness” in bass response. This is not uncommon but fortunately, there is a way to resolve it? I will try to share my method where everyone can try. But before I talk about my method, I will like to know your method. I always believe there are "many roads lead to Rome"…share yours as well.

You can go direct to my method here: Seat to seat consistency for bass...(sharing and how-to) - #10 by desray

Using REW, I average out the measurements from various seating positions before EQ then run Audyessy.

Noted. are there any difference in your SPL readings amongst the seat? Let’s say 2 or 3 seaters.

Didn’t measure the SPL. The seat near the corner of the room is definitely louder especially the bass which makes sense.

That is precisely what I am trying to solve in this thread. Making the bass more “consistent” in every seat. I have a 2 seater recliner and it is important for me so that I can switch to any seat any time. BTW if you have the time, try to use REW and the UMik 1 to measure the SPL readings for all the seats and post here.

For my situation, i dont really invest much time to perfect this as 99% of the time, only MLP watching. 1% of the time, 2 seats watching. 2 seater sofa.

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This is something that takes time to solve I believe?

I see…if this is indeed the case, then I guess this does’t apply to you. But just imagine every seat is a good seat. That’s the ultimate goal for that ultimate home theatre experience.

Not really, it can be easily done. I’ll share my method tmr…In fact, I am actually looking forward for members to share their own creative solutions to get this consistency thingy to work for your home setting. As I suspected, not many really care about it.

This is a simple tutorial tailored for those who have multiple seats - e.g. a 2 or 3 seater sofa. If you are like me who desire consistency in bass output for all seats, you may want to give this a shot. It works for me, and I hope it works for you as well.

Caveat #1

This works for two or more subwoofers only. This is not applicable to a single subwoofer setup. If you have 4 subwoofers placed at an equidistant to your Main Listening Position (MLP), then your seat-to-seat variation should be minimal. Instead, you should focus more on time-aligning the subwoofers using REW. But this is not what we are here for…

The image depicted above is for illustration purposes. Let’s assume that there is another “phantom subwoofer” that existed diagonally at the rear of the setup, making it a dual subwoofer setup. In my case, I have 3 JL Audio subwoofers – 1 pair of E112 in front and a E110 at the rear right of my seat, making it a challenge to get an even response, let alone a good and uniform SPL reading.

Many of us have spent time to time-align to get an even frequency response and then bump up a few dB (increase in output) from 15Hz to the 120Hz range to get that “house curve”. And that’s all good but what happens if you are sitting near to a subwoofer, say on the “Too much bass” seat on the left? What you get is amplified by 2db due to the room mode and the position of your seat. Conversely, you will get a weaker bass if you are sitting on the right side of the sofa couch. The “Emperor seat” gets all the best stuff because you are the one who spent the money and the man-hours to get the family dream home theatre set up. But let’s say you are feeling generous and you want all seats to sound and feel “good”. The way around it is of course to get all SPL readings to read 72db (single subwoofer will be tuned at 75db while dual subwoofer setup will be tuned to around 72db so the summation of both subwoofers will get you around the output of 75db) for all 3 seats. This is challenging but not mission impossible. Here’s what you need to do:

Getting the SPL readings

First, switch off the rear subwoofer and focus only on the front subwoofer for now. If you have a REW with UMik 1, you can use the built-in SPL meter and pink noise generator for the subwoofer calibration to play a sine tone of 50Hz and take a measurement of the SPL reading at each seat location. Ideally, all 3 seats should read 72db but more often than not, this will not be the case due to the proximity of the seat to the physical subwoofer, the layout of your décor, furniture, and walls. This will create a “unique” room mode that will ultimately have an impact on the SPL readings.

The trick here is not to make the “Emperor seat” read 72db and instead lower the gain knob on your front subwoofer to read about 72db. Of course, this will ultimately cause the SPL reading to drop for the middle seat and the right seat. It is ok. What you are trying to do here is to ensure the “Too much bass” seat reading will always get reference level at 72db in order to attenuate the overbearing bass effect. While the “Emperor seat” may register a drop in SPL reading, it will not have a very big impact. Proceed to take the readings for the middle and the right seat as well. Do not worry too much about the SPL readings, for now, just make a cursory check to ensure the drop in readings is well within the reasonable 3 – 6 dB range.

Once we are done with the front subwoofer, we will move on to the rear subwoofer. Before that, remember to turn off the front subwoofer. Recall the rear subwoofer is placed at the rear right of the sofa, hence the right side will now register a higher SPL compared to the middle and the left seat (opposite of what we get when we measure the front left subwoofer placement). So the same method applies, just make sure the SPL reading for the right seat measures at 72db and take a cursory reading for the middle and the left seat.

Next, fire up both subwoofers and take a measurement for all the seats. You will see variations when both subwoofers are fired up due to the interactions of the room mode. So long as the readings fall within the 3 – 6db deviation, you are alright.

Caveat #2

Proper subwoofer placement still plays a large part here. For 2 subwoofers, the preferred layout should be one at the front and the other at the rear of the MLP. Whenever possible, do a diagonal placement for 2 subwoofers, meaning one on the front left while the rear subwoofer will be placed at the right rear or vice versa. I have personally tested the placement of 2 subwoofers at the front (at 0-degree polarity) and it does not yield a good frequency response relative to the MLP unless you move your seat to compensate for any peak and nulls created by your room. More trial and error need to be done. To overcome the guesswork, I highly recommend everyone to use the Harman Room Mode Calculator (HARMAN International). I have been using it extensively over the years to help me determine the optimum seating distance relative to my subwoofers. This calculator is extremely useful for beginners and advanced users to help understand your room mode better so that you know where and how far (in distance) to place your sofa and subwoofers. Remember, placement of your speakers and subwoofers relative to your MLP is extremely critical to take the guessing out of the equation when you set up your home theatre. Once you have the foundation set and know exactly where to put your “Emperor seat” and where to place your subwoofers, room calibration and aftermath EQ’ing will be at its minimum. There is literally no need for miniDSP if you have a solid “ground foundation”. The only time you need it is due to the imperfections that are present in your ground foundation. Proper placement of the speakers, subwoofers, and your MLP take up 70% while any form of room EQ calibration will take care of the 20%. 10% will be allotted to acoustic treatment. My mantra is to get it “right” the first time and every time.

Bass “level output” tuning

Now comes the part to tune the bass evenly. For this exercise, you do not need REW anymore. The REW and SPL combo can only do so much. It set the foundation right and provides you an average SPL reading at different seats, to better understand the way your subwoofers interact with your room relative to your MLP. Forget about the various sine wave test tones as it will not help you in getting an even bass output (notice the emphasis is on tangible levels of output, something you will hear and feel and not the actual SPL reading) at your seats.

The real tuning begins with listening to a good “bass-looping” track that you are familiar with. Choose a track with a good amount of bass range from bass to low-midrange (60Hz – 500Hz) and not the sub-bass range (20Hz – 60Hz).

I highly recommend Jesse Harris’s Mizayaki soundtrack (short but looping). You can download the clips from Youtube here: Jesse Harris with Star Rover - "Miyazaki" (Live at Dangerbird) - YouTube

Before you start, if your subwoofers are in the front and rear layout arrangement, make sure to switch one of the subwoofers to “180 degrees” (inverse) for your polarity while the other at “0 degrees (normal). In gist, what this does for the subwoofer driver with inverse polarity to move in the opposite direction of the main speaker drivers when content is being played while normal polarity will move in tandem with the main speaker drivers.

Next, set the phase control knob to around 45 degrees as a good starting point for both subwoofers. With the soundtrack playing, take turns to cycle between the left and the right seats. Use your ears to “hear” and “feel” the soundtrack as you slowly make minor adjustments to the phase control on both subwoofers. You will know you get it right when you start to “perceive” the same level of loudness and full body of the soundtrack for all seats. The “Emperor seat” will be averaged out and you will still get the best sound/bass experience while your wife and children will also get to share the fruit of your labor and investments.

Demo Time!

Fire up some of your familiar movies with bass like Ready Player One or the clips from my XP Demo Disc 8 and test out all the scenes. Make finer adjustments along the way if you need.

Try it out during one of the weekends or your off days and you will appreciate what this brings to you and your family.

This option is actually available on the Lyngdorf processor. It’s termed as Focus vs Global. Focus is more for single MLP seat, all other seats doesn’t matter. Global on the other hand, will try and average the readings and ensure eq is applied to reduce seat to seat variation

For the past 21/2 years I have been using, I always prefer the global eq. Which is to have consistent seat to seat variation . With single focus , I can still hear resonances in the room, especially at corners towards the kitchen area. Decay is not as good as global eq as the “focus option” eq programme only focuses on MLP, not the entire room

The eq programme doesn’t just take into consideration the direct frequency response of the system as a whole, it factors in the power response. The direct frequency response, is just one side of the story , we have energy reflecting off the ceiling and walls to combine with the direct energy. So this aspect is important as it also determines the decay of the given frequency

Once we take care of the power response to have the consistency , automatically the seat to seat variation will reduce.

This approach is highly recommended by lyngdorf because it doesn’t only improve seat to seat variation, it also improves the timing response. This is also the reason why I went with the line array woofers.

If we use line source speakers, almost every seat will have that consistency in levels as well.

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I see. thanks for sharing that Lyngdorf AV processor comes with this feature…I guess there is a reason why we are paying top dollars for a flagship AV processor. My approach is more layman and simple and suitable for the majority who still use AVR and Pre/Pro like from big-box brands like Denon and Marantz with Audyssey XT32 featured as the room EQ. Even Anthem ARC also doesn’t have this feature.

Ha! Therein lies the catch. I only have 1 sub.

For discussion sake, in the picture shown, if the 2-3 subs are placed directly behind the seats, they will be pretty much near-field therefore can setup same volume & phase, should work quite well. Correct?

Yes, same phase. The volume you can use SPL to measure and level all the subs. The purpose of using multiple subs at the front and back is to solve the room modes and flatten the FR. Due to WAF, I have to flank my dual subs at the front left and right.

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Nice share! While I did not use any method for seat to seat consistency when using previous Denon and Marantz, but I do know the importance of it.

That’s being said, most of the time I’m the only one that is concern when comes to sound as compared to family members, however I do use seat to seat when I have friends or family members over.

I’m have a 3 person L Shape couch and how Trinnov does it is by weightage.

Using presets, I can have single MLP measurement in a preset at 100% (selfish mode), and/or multi seat measurements in another present with 34% MLP, 33% left and 33% right couch (friendly mode)

Using the multi seat measurements, i can change the MLP on the fly to either left or right seat and set the weightage more on one side, eg, left couch (now becomes the MLP) at 70%, center couch (former MLP) at 15% and right at 15%. Or you may choose 100% at one side totally.

With the multi measurements, respective time domain, reflection, phases etc will shift accordingly to weightage and newly selected MLP.

But usually multi measurements should remain just 34/33/33% for seat to seat consistency. :smiley:

Otherwise just activate selfish mode if I’m watching alone. :crazy_face:

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So Trinnov also has such a feature. I guess all top of the line flagship has it. How about StormAudio? Anyone has experience?

I did not find time to use REW to measure the bass from seat to seat but I have retrieved the FR from Audyessy which are supposed to be quite accurate.

Seat 1 is the MLP, seat 2 is the LS and Seat 3 is the RS. I usually listen at seat 3. Seat 2 is at the corner of my living room and you can see the there is peak at around 60Hz.

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So based on all these finding, what will be your personal preference when comes to dB differences?

Ya it has the feature, we can also add multiple focus positions after the room eq. Meaning I can make my left seat the focus position, by me measuring just the left seat and saved as focus left. Everything then shifts to left as MLP or measure another at right seat and name it focus right, the right seat then becomes the MLP. So much versatility with the higher end processors. In the end, i still settle down with global

But I have read through the approach you are using above. You need to also look at the headroom as well. The problem with the approach above is it uses the level matching approach . Most often with this approach, one of the subs in the chain, will be working harder over the other sub. The smaller sub, E110 will be the weakest link in the chain and assuming if the 10” sub is located at the place where it needs to pump out the most amplifier power into the room, that will be the weakest link dragging the entire system down . The smaller sub will run out of steam very fast before the other two, assuming it is set with a requirement for a higher amplifier power

To solve this, You might want to move the “smaller” sub to a location that requires the least amount of amplifier power (a location where there is maximum boundary gain). To balance the headroom required by the 12” subs

So in your case, it looks as if the balance between 2 x 12” will happen with one of it in front and the other at the back. The 10” little brother is then used and moved somewhere else to smoothen out that variation

The approach above will work if you are listening at levels not past a certain volume maybe -15mv? Depending on the boost and house curve applied to make sure there is no compression and harmonic distortion

Seat to seat variation reduced at the expense of headroom? That’s the other factor one would need to consider and check if taking the above approach

Seat 3 is where I usually sit. Fewer peaks and troughs. The average for all 8 mic positions and Audyessy should yield a better FR.

I have limited placement for the subs so can only use PEQ and delay to flatten the FR as much as possible.

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