You don't lack bass, you have too much treble

@minorl The problem for most audiophiles is they have no idea what they are listening to. They have no reference. The best thing you can do is invest in a usb microphone and an acoustic measurement program. Then when you get a equalizer you will know exactly what to do. If you get a room control system it will do it for you and probably do it better, certainly much faster. Digital processors can also determine launch times and correct delays. '

I do not care for a flat amplitude curve and most people don't either, but the right curve is not far off flat. We have been dealing with target curves for 30 years now and we know what suits most people in residential situations and that is a boost below 100 hz and a slow cut above 1000 Hz so the 20 kHz is down between 6 and 12 dB. This is a good starting point for most systems. The problem is that if you do not have subwoofers the low end boost can really increase distortion in most woofers at volume. Full range drivers are at severe risk. 

@erik_squires When you limit reflective sound in any room the sound obviously becomes more localized to the speaker. The speaker gets sonically smaller. If you treat a room by hardening the walls and removing the carpet, then yes, you can make a speaker sound larger. That would be an odd approach that few of us would take. My suggestion to you is to put the carpet back down. 

When you limit reflective sound in any room the sound obviously becomes more localized to the speaker. The speaker gets sonically smaller

@mijostyn 

For the record, I'm not just spouting theory from books or an AI app.  I've heard this work many times.

You are missing almost all the context from the title of the thread and the additional context I added in other messages.  When I say that absorption can make a speaker sound bigger I'm specifically talking about their bass output.   Says so right there:

You don't lack bass you have too much treble

The common acoustic absorber has two functions and you are only thinking about one of them, which is about reflections and imaging.  The other function, perhaps the most researched and most important is in providing band-limited absorption to the total energy in a room.  This function is why high end panels have charts of Sabines vs. frequency.   If you can hear how wide and tall your speakers are then you probably need new speakers.

So, now that we've established I'm not actually talking about height, width and depth of your speakers but how much bass they seem to put out (see title of thread, again) you need to consider that most acoustic panels are limited to the mid to treble ranges. 

So, then what happens when you take mid and treble energy out of a room?  You end up with more bass.  It's like taking out the veggies from a stew until you only have the meat left.  Is there less stew?  Sure, but now it's beef stew and that's better than it was before. 

As also mentioned, so before you go that route, this is not the only approach possible.  I mention it to help A'goners consider multiple options.  Since taming coherent reflections is also a good thing, this approach may have multiple benefits.

If you treat a room by hardening the walls and removing the carpet, then yes, you can make a speaker sound larger.

Which is the opposite of what I'm recommending, but you do you.

Brightness isn’t just caused by the equation of the speaker’s frequency response to room size and dampening ratio as Erik mentions, but also due to other forms of noise in the chain. This could be found through:

- Poor resonance control in the speakers, rack, and components where vibration induces slurring, peaks, and nulls of certain frequencies. Great resonance control will result in much improved image solidity, making for more audible, impactful bass /and less noise through the rest of the frequency spectrum so sonics are more effortless and easier to discern.

- Jitter and EMI are usual culprits that induce high frequency noise into a system to a point where people find their system to be bright, peaky, piercing, and /or fatiguing. In such case it may be improved by using better components or cables, or introducing technologies or accessories that are designed to lower noise floor.

- Poor speaker and amplifier matching is a common challenge I see my customers and others face. Often times, people think their amps can properly drive a speaker just by looking at the specs. Some speakers require a lot of power, and it’s easy for many that are uninformed to look at the speaker sensitivity to the watts of an amplifier and be done with it. Sometimes they get lucky, but in most times, amplifiers cannot fully handle the impedance set by the speakers. Klipsch are great examples, since I know that while they claim to be of high impedance, many of them actually have an impedance dip in the midbass. Regardless, a few may look at the Klipsch’s sensitivity (say high 90s dB) and nominal impedance (usually 8 Ohm or greater) and believe a low power OTL amp would work well. Well, they’re wrong, as the OTL amp can’t handle the impedance dips, and this further makes Klipsch speakers sound “bullhorn-ish”. Sadly, even many solid state power amplifiers don’t deliver the high current needs to truly drive and control smaller speakers, which tend to be lower in sensitivity and lower in impedance. I’ve in many times guided customers to better amplification that simply wakes the speakers up to the point where no subs or larger speakers are needed.

Case in point, Erik suggests a very good point on treating the room to address and optimize  full-range frequency delivery, but it is one of many ways to address it. The whole system’s performance depends on any and all bottlenecks being addressed to a certain level.

Also, if your stew has too much salt, add more potatoes.  Same Yin-yang balance I'm trying to talk about here.

+1 to the OP and to blisshifi  😊