Posted by Tan
Any audiophile who had spent enough time in this hobby would realize that room acoustic is that one factor that can make or break the performance of your HiFi system, regardless of how high-end your system may be. It thus makes sense for us to put in effort to solve our room issues, rather than to get on a never-ending equipment upgrade spiral.
Among the many possible room acoustic issues, the one most affecting listening pleasure is bass boom. That is when bass energy reflected from the walls causes the bass region to be excessively boosted and to also linger too long in the room after the music has passed. The effect is not only muddied and ill-defined bass but it may also affect the overall clarity in the midrange and highs, music just turns to mush.
Bass boom
is a most difficult acoustic problem to solve. As bass frequencies have
very long wavelength, their travel is hardly affected by small objects, such as
those we use for tweaking. Therefore, as we always see, in-room bass treatment
solutions are necessarily and invariably big and bulky (here, I mean passive treatment
solutions. There are also active treatment solutions which is of the size of a
bookshelf speaker for example, and there is also the DSP way, but those are discussion for
a different day).
Comes an
audiophile friend of mine, Mr. Beh. Bothered by bass issue in his own listening
room, Mr. Beh did his research and built his own bass treatment solution based
on a public domain BBC research paper. He called his creation Acoustic
Solutions membrane resonator. On the outside, it looks like a rectangular wooden
box measuring 2ft x 2ft x 7in (58 x 58 x 18cm), the inside is partially stuffed
with absorptive material, it is said to be most effective at treating room mode
in the 50-150Hz range.
The
resonator is to be placed at the walls where the bass energy is the strongest
(which will require the owner to do some experimentation to find the best
spots), with the front of the resonator (i.e., the membrane panel) facing out.
Multiple units are usually required to achieve the best results.
I joined a room
treatment session where Mr. Beh used his resonators to treat the room. His approach was not just subjective listening but also rooted in objective
measurement. At the beginning of the session, he used the REW acoustic measuring software to
identify the acoustic behavior of the room, and pinpointing the problematic bass
frequency ranges. Then, the resonators were placed at strategic places (corners, middle of wall, single box or multiple boxes stacked), then room
measurement was done again. The process was repeated multiple times to ensure
that the greatest effect was achieved.
We could
see that on the measurement graph the RT60 (reverb time taken for sound to
attenuate 60dB) was reduced by more than half from 1sec to 300-400 ms, the bass
peak at 60+Hz on the frequency response curve was also cut down, meaning that
bass would now sound tighter and cleaner, an excellent outcome.
We
confirmed in our subsequent listening session that bass notes indeed were
better defined, and bass response sounded more linear, which also improved the
overall clarity of the sound. The one not-quite-expected effect for me was that
I found listening now was more comfortable, less fatiguing, maybe it was due to
my brain not having to compensate for the disturbances in the bass region,
regardless of how subtle or prominent they were. A quick experimentation in my
own room also revealed that the resonator could add some richness to the mid,
and round out and smoothen the highs a bit.
The following photos show the use of the Acoustic Solutions resonators in Mr. Beh's own listening room:
Further details on the design and use of the resonators:
If you are bothered by bass issue in your listening room, and you are uncertain about the efficacy of room treatment products in the current marketplace, consider a Malaysian home-grown approach then. Who knows, may be Mr. Beh would be happy to visit you and help you with finding the solution. He has helped quite a number of his audiophile buddies solve their headache already.
List price RM980/pc. Special introductory price RM800/pc for a limited period. Contact Mr. Beh Thuan Wei +6012-5222453.
