Speaker cab gurus--help me clear something up

[Mr. Foxen]

Unused speakers in the room is negligible. Its just more stuff to absorb some sound and bounce it about. More stuff tends to make rooms sound better. Hence treating studio control room walls. Be more worried about people stood around absorbing the sound.

 

[DukeLeJeune]

Several years ago at a high-end home audio show, we were getting significant over-emphasis in the 70-80 Hz region. So I took a second pair of speakers and retuned them to about 75 Hz by shortening the ports (fortunately they were modular ports) and placed that pair in the corners, not connected to anything. They behaved as tuned Helmholtz absorbers. Worked pretty well... people who came back the next day commented on the improvement, and we just smiled and thanked them, and if anybody asked about the second pair of speakers in the corners, we just said they weren't hooked up.

 

[jnewmark]

Here we are!



This is the idea I was after! I had forgotten the key part about one of the speakers being shorted or unused. Apparently I had mixed it up with other posts/threads about beaming and comb filtering, obviously not related issues.

Do any of you happen to know where I could look for more authoritative details on this point? Thanks all!

I would ask your questions on Bill Fitzmaurices's forum. He is a degreed Acoustic Engineer, and as about as " authoritative " as they come.

 

[Wasnex]

Several years ago at a high-end home audio show, we were getting significant over-emphasis in the 70-80 Hz region. So I took a second pair of speakers and retuned them to about 75 Hz by shortening the ports....Worked pretty well

Duke,

I have heard said, "A little knowledge can be a dangerous thing." Thank goodness you are on our side! Very cool.

 

[T-Bird]

Hi.

... two drums would act as wave traps on each other. This is the point I especially want to know about--is this wave trap thing true, and if so, exactly how and why? How specifically does it play out in a speaker cab?

It's true.

But only to a degree, and usually only on rather narrow band.
Not as likely with bass drums as it is with ported enclosures.
Drums are IME rarely precision ported .


Mr. LeJeune there already pointed out the Helmholtz bass trap, here's some Google links:

https://www.google.fi/?gfe_rd=cr&ei=usPHU5u5JobK8gfY3IHADQ&gws_rd=ssl#q=helmholtz+bass+trap

Tried and proven concept, and utterly annoying if it happens by mistake.

Shorting the speaker BTW won't offer much help either way on a MI driver.

Regards
Sam