PDA

View Full Version : Room Gain and Predicted Response



Robh3606
08-05-2003, 01:11 PM
I have a couple of questions for you. With room gain can you predict how much and at what frequencies??

The reason for the question is I seem to getting more low end out of my E-145's than the box programs would predict. Especially at 40Hz where I should be about 10db down. Its a pleasant but rather unexpected surprise. I tried pink noise for 1/3 octave averages and sine sweeps while monitoring the levels on the RTA. They all read about the same are consistant, and confirm what I was hearing which had me scratching my head. :confused:

If you know your room gain vs. frequency do any of you take it into account when tuning boxes for your room?? Looks like a way to avoid the boom with a flat box. Any thoughts?? I am wondering if that is what I am seeing.

Rob:)

GordonW
08-05-2003, 04:00 PM
Oh heck yeah, I take that into account!

Most of my box designs, I tend to tune for an initial rolloff starting around 35-40 Hz, but VERY SHALLOW, down to the mid-20s or so, where they roll off steeply below port resonance... usually by tuning the port lower than normal. This tends to alleviate the 40-70 Hz "room boom" found in many places, and has yet to bite me in the @$$... :D

Sometimes, I'll also slightly oversize or heavily stuff a box as well, to lower the bass output at 50 Hz, at the benefit of more output at 25-30 Hzm (lower Q, effectively). Same results as above, generally... works for me!

Regards,
Gordon.

Earl K
08-05-2003, 04:45 PM
Hi RobH

I get similar real world results from my le14a in their original S99 boxes. The 42 hz Fb, in an effective volume of @ 1.9 cu ft gives a curve with a bump around the 60 the 70 hz region . In my room , in my normal listening position, I get great response at 40 hz. This stopped me cold in my tracks , as far as building up the planned "test boxes" for my vertical twin / MTM - thingy .
Now I think I understand why the orient prefers the smaller box sizes of the K2 -S9500 to the M9500 .

Do you have any of Dr. Floyd Tooles pdf papers that he has at the Harman Website ? One called "Loudspeakers and Rooms - Working"(???) is particularly good in that it deals with room axial modes and such along with their gain .
I'd post a link to it , if I could find it . I just looked for it. I have 4 of his pdfs , all aimed at the home user . I can post parts of these files if we can't find the original links .

regards <. Earl K