Getting Good Bass for your Home Theater Setup

Topics of discussion will include:

  1. Bass Management
  2. Subwoofer Placement
  3. Calibration
  4. Listening for Final Adjustments
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Discuss everything you want to know about bass traps and how they can be used in conjunction with multiple subwoofers to get a uniform bass responses in your entire listening area.

It is actually totally possible to get flat bass response in more than one seat with multiple subwoofers and EQ to take the room modes.

So why do we still need to have acoustic treatment and bulky bass traps? Grimani said it best - the room is the Boss and will impart it’s sound and make all the expensive hardware perform less than optimal.

Even after flattening all the modal peaks, there is still strong possibility that we hear the room more than we hear the content of the bass/movie soundtrack.

The reason is decay time. Especially in small rooms, multiple subs required to achieve even bass response really overloads the room with sound and bass energy… Without any treatment, the energy hangs in the room long after the signal has changed or decreased below the room energy level. When that happens, we are hearing the reverberation of the room, not the sound being playback.

We are all roughly familiar with the concept of room modes, with the first modal peak related to the longest dimension of the room. A 4m length with have the first peak ~ 42Hz.

There is also a zeroth room mode - below the first modal peak. The entire room is pressurised, imagine trying to blow up a balloon inside a box. The balloon will press against the walls of the box. That’s what the zeroth mode is doing. Any bass below the first mode is literally trying to pressurise the room.

All these bass energy has to go somewhere, or it hangs around a long time and the bass sounds slow and muddy and less defined.

This is the reason bass traps drastically improves the quality of the bass sounds in the room. It will not actually have much effect on a modal peak, especially in the 40-50hz range. Those still need to be Eq-ed out. Even 8-12 large bass traps in a room setup will only reduce the main peak by ~5-10db at best. And peaks can easily be 20db in a bare room.

What the bass trap does is to dissipate the sound energy, so that we can hear the speakers and subs playing the soundtrack, not the energy overhang in the room.

This is the way.

:grin::grin::grin:

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Yes, I always love hearing Grimani talking about home theater setup and how to improve the overall sound presentation and bass. This guy really knows his stuff and explain in an easy to understand concept. The one he touched on is the Harmon Room Mode and I have the excel calculator to help with the MLP. The key idea to this is not to place your seat in the null position and understanding that along with the acoustic treatment that you’ve mentioned in your preceding post makes a complete package.

10000% agree with the above statement. Nice sharing.

After a few years tweaking my setup and trying to tame the 43Hz mode, no reasonable treatment can deal with a +15dB peak due to the square room. EQ is the only solution at that sort of wavelength. A couple of bass traps still helps with dissipating some of the bass energy.

Have you try this Harmon Room Mode Calculator to help “avoiding” certain common room modes? I’m not sure many is aware of it or not but it certainly helped me a ton with my 3 subwoofers placement.

I have not tried the Harmon excel worksheet. I just checked it out, a little to raw for me. I have used (and prefer) REW RoomSim which is more graphical, and probably does the same thing. I used RoomSim to position my lonely sub. Thanks for sharing the worksheet, interesting…

From what I understand, room modes are mostly pre-determined by the room physical dimensions. Mine is a dedicated room (actually a bedroom converted into a Study/HiFi/HT room). May I know what you mean by “avoiding” certain common room mode? Do you mean where not to place the sub where it may add on to the room mode? or something else?

Very good video by grimani, I enjoyed 3 of his videos so far, from acoustics to diffusion and getting good bass version. Was listening through their webinar whilst having picnic with the family at gardens by the bay… not bad…

Looking forward to his videos next week , lotsa solid and valid points …

It was also mentioned in the video, it’s the quality of the bass we want…accurate bass and not just SPLs

I was waiting for him to reveal the secret… the answer is one front one back… he hasn’t revealed it…

Yup…that Harmon Kardon Room Mode Calculator is pretty much what Grimani was talking about in his video. In a nutshell, this room mode calculator helps you to determine the MLP to “avoid” sitting at a null (or bass suck-out) position. This worked in tandem with your subwoofer placement. In general, as soon as you figure out where you decide to place the subwoofers relative to your MLP, you can figure out whether to move your MLP or your subwoofers “out” of the null position. By filling in your room dimensions - L x W x H, the spreadsheet will provide an estimation of where the 1st, 2nd, 3rd and 4th harmonic standing waves will be and the goal is to “avoid” those positions as your MLP.

Audioholics pay him quite a bit for his time to do all these online webinar. :stuck_out_tongue:

I never miss a session from Anthony Grimani.

Multiple subs and room treatment go in tandem in order to achieve bass nirvana. Proper placement of multiple subs can eliminate the nulls and bass traps to reduce the decay. Can’t wait to build my dedicated HT room when my kids grew up.

I see. Positioning sub & MLP. Based on cursory analysis, looks like my MLP (L=25% from back wall, W=dead center) is quite optimal where the 43Hz mode is a mix of almost peak (L) + null (W). Only concern maybe is with the 4th (172Hz) where it is peak + peak, which may be the cause of occasional honkiness in the deep male voices. I cross checked with RoomSim, and RoomSim shows the same thing.

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The room sim is the best, I use that all the time. So good and easy and u can see things on the fly

The best placement, is having the subs where there is a null in the resonant frequency area

I did one just recently

We were just exploring the possibility of lowering ceiling heights from 2.65 to 2.3m

Diagonal front back almost always the way to go…

Observe the above, we have a natural house curve, without any EQ. This is the best. Subs at corners, best transient attack and superior timing, no boosting EQ needed, no eq required at the 40hz room mode location… the best .

When the diagonal subs are stacked, then :muscle:t2::muscle:t2:

Here is front two left right with one left back

Slightly off

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For surround, ATMOS and back, most likely it will be smaller speakers that normally cross over from 80hz to 120Hz.

If the plan is to use multiple Sub to EQ the bass, what is the cross over for the LCR?

In my experience, I found that 100hz seems to be the magic number most of the time, not 80hz or 60hz… but 100hz

I do this for all the speakers, I draw a clear line, anything below 100,hz, I go “ Mr subwoofers, please deal with it!”

Anything above, I tell the speakers :” your territory, show them what you can do”.

This is consistent across even for Atmos speakers and including LFE.

Finding the ideal XO takes time, if u r using the same GX300 as me, then I can tell u 100hz is the best . When the gx300 has enough headroom, they can really sing… especially when they are relieved of bass duties down 100hz

Agreed with Bryan on this…80Hz is a good starting point but usually, the x-over is higher even for very good speakers with good bass response. Unless you use REW to do some measurements and patiently plotting the points until you get a smooth x-over between the speakers and the subwoofer(s), you can’t really tell. For those with no time (due to work), you can either take some time over a period (on weekends) to perform all those REW measurements or you can just play some 2 channel music and try to achieve a smooth transition from the Mains to the subwoofer(s). Playing with phase control also helps.

100 Hz is great. It is harder to find ceiling speakers that cross over below 100Hz with good SQ.

That also means that unless we have a very big room. No point getting very large speakers that can go 40 Hz for the LCR.

I will stick around with my GX300, Gold 100 and In wall 380. Might consider slightly bigger ATMOS speaker that can cross over comfortably at 100Hz or 80Hz as compared to AG Diva that I have.

Will focus on learning and doing EQ with multiple Subs. I got 2 Rythmik E15hp

that is correct… subwoofers are best for low frequencies… enjoy the journey!

Looking at your other post, you are building a dedicated HT room in a non symmetrical room. You will not be able to use the Room Sim since your room is an odd shape. You can use the alignment tool if you want to achieve a smooth bass response with your dual subs then run the auto eq from your receiver.

If you have a full-range high-quality LCR, maximize the use of the high-quality speaker by crossing lower, or don’t cross at all. I have the full range Usher LCR that digs down to 30Hz, personally I find crossing at 40Hz works extremely well for me. The remaining speakers crosses at 80Hz.

Do also check your own hearing ability to localize low frequencies. If you can localize say at 120Hz or 100Hz, crossing below that is better. For me personally, below 80Hz, I can no longer localize where the sound is coming from.

Personally, I prefer to let the sub handle mainly the boom boom LFE.


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