Acoustic treatment for bass resonance?

[Dr.EM]

I ask on behalf of my brother, who has recently bought a large oak bookcase for his room. Adding this into the room has brought about a bass resonance at his listening position, which bothers him.

I think I know the cause. It is likely that where the bookcase is located has accentuated the depth of a cove in the room. This has always caused some exaggeration of bass frequencies but the effect seems confounded with the new bookcase in place. Shown below is a rough floor plan with and without the bookcase:



So the bookcase end has extended the wall of the cove, in effect. It would perhaps also decrease the side-to-side wall distance too, but a lot of the bookcase front is open, it's not loaded fully with books.

For acoustic treatment, there aren't too many areas in the cove where foam bass traps could be installed:




In fact, the only acceptable place is on the back of the main door (the one without a jamiroquai cutout!). My question is, will 100mm thick acoustic foam on this door have much impact on the bass resonance? Thinking 2 or 3 600mm square panels can be used.

The distance from door to wall (with calendar)/bookcase end is 1.5m.

[AllenB]

Room treatments are a great thing but you may have mixed results with that amount of damping. Another option is to use a sub to counter the peak.

[bentoronto]

While generally a false hope, a parametric equalizer might help. It tames the amplitude of the bad note(s), but the offending tone remains in the background.

Hopeless to try to tune absorption at home.

A room's absorption is a function of the total absorber-stuff anywhere in the room, under beds, in closets, etc.

Tectum with air-space behind is one of the few feasible absorbers of bass.

[FrankWW]

Replace it with a bookcase with open sides (and maybe open back,as well).

BTW, is this emphasized resonance really a new thing?

[dabbler]

I had the same problem in my room. Broadband absorption completely cured it. Eq won't work.

[dabbler]

Hopeless to try to tune absorption at home.

Not at all. Broadband absorbers in the corners will fix the problems without unbalancing the sound.

[whgeiger]

What happens to the resonance when you open the doors? Either or booth?

Check the back pannel of the bookcase. Maybe it is resonating.

Regards,

WHG

[dantheman]

I'm my studio experiments, opening a door, or 2 and windows didn't do much. I've put some heavy duty amounts of treatments up an they haven't done much in the deep bass. Resonant walls(CLD) or those perf boards absorbers are where I'd look.

Dan

[bentoronto]

Originally Posted by dabbler

Not at all. Broadband absorbers in the corners will fix the problems without unbalancing the sound.

Well, you're wrong on all counts.

First of all, what I said was it wasn't feasible to tune the absorbers to the offensive frequency esp. in a home and DIY context - so your dismissive put-down "Not at all" seems, ah, misplaced.

Second, an elementary examination of the specs of absorbers will show each is very much tied to a frequency compass and room location of the absrober affects all the tones that "use" that location in bouncing around. Which is why I recommend working with Tectum for a whole bunch or reasons, including having a fairly broad-spectrum extending into the bass, when installed in certain ways,

However, it is true to say that an inept listener on first casual listen might just think he/she has installed a "broadband absorber" that didn't "unbalance" the sound from the previous or any state of the system. But then you hear all kinds of opinions on the web.

[AllenB]

I have had success with broadband absorbers (resistive bass trapping) and it is viable to target all room modes. The stronger they are, the more they'll respond, it seems.