weak bass in room 12x14. Help please

michaelv · « **on:** 2 Jun 2006, 05:25 pm »

Hi,
I use room mode calculator in Ethan's website (thanks Ethan). I get the output but i have trouble of understanding how this relates to my room. After trying here and there i still get weak bass at listening position, but the case that i move away from the seat.

Based on many readings from the forum, i think sit at the null where the signal canceled out.. I need to at least to treat this. Therefore, i decide to measure my room.

How do i post the picture here so that anyone can see?

thanks.[/img]

Ethan Winer · « **Reply #1 on:** 2 Jun 2006, 05:43 pm »

Michael,

> i have trouble of understanding how this relates to my room. <

My ModeCalc program is useful mostly when designing a new room, where you have the chance to establish the room dimensions. For an existing room it's not that valuable.

> i still get weak bass at listening position <

Many rooms have this problem, and the solution - as I'm sure you know! - is bass traps as well as having good speaker and listener placement. The worst place to sit is halfway in the room front to back because there's always a deep null there. The best place to sit is with your ears 38 percent from either the front or rear wall. If you have high-speed Internet, I just made a video for my company's web site to explain all this.

--Ethan

michaelv · « **Reply #2 on:** 2 Jun 2006, 05:54 pm »

Thanks, Ethan,

When you say 38%, does it relate to distance from speakers too or it does not matter as long as i am in 38% distance from rear or front wall?

fajimr · « **Reply #3 on:** 2 Jun 2006, 06:39 pm »

great video ethan!!! thanks for continuing to inform us!

bpape · « **Reply #4 on:** 2 Jun 2006, 06:44 pm »

He's referring to your seated ear position being at 38% of the room length from the front wall (or 62%). The speaker position can also play a part in the bass response but for reasons of reinforcement and cancellation based on their distances from the wall behind and beside them.

Start by moving your seat. Then play with speaker position to find the place where you get the smoothest response and still have good imaging.

Bryan

tdangelo · « **Reply #5 on:** 3 Jun 2006, 02:27 am »

michaelv, my room is the same size as yours and my bass is great. Here's a Visio drawing of what I've done - maybe it will give you some ideas. I sit about 2' from the back wall. My ceiling height is 9'. The stuff in between the speakers is my Ultrasonic rack and amp stands. The rack is about 23" tall

Tony

Folsom · « **Reply #6 on:** 3 Jun 2006, 05:24 am »

Can you draw a picture to post?

It works like this

Pretty easy, just put the url inbetween those two, and yes the / is important.

I am really curious how your speakers and or subwoofer/s are positioned. Placement of such things can be key, and the adjustments on the plate amplifiers of subwoofer DO have affects.

Bass traps are not always the answer necessarly.

michaelv · « **Reply #7 on:** 3 Jun 2006, 06:04 am »

Tony, thanks for the drawing.

Before i read this, i tried to move the seat back, about 3 ft from the rear wall. And the speakers are still 8 ft apart and 9 or 10ft from my listening position. I know this configuration does not meet the 38% setting. But i can hear much better bass now. One thing i notice that the soundstage seems to be bigger besides the bass is more defined.

I'll keep playing....

95bcwh · « **Reply #8 on:** 3 Jun 2006, 06:37 am »

Quote from: Ethan Winer

Many rooms have this problem, and the solution - as I'm sure you know! - is bass traps as well as having good speaker and listener placement. The worst place to sit is halfway in the room front to ...

One question about this 38% rules: What if you can afford to cover both your front and rear wall with bass traps. Does this rule still applies?

Also, if you cover the walls with bass trap, can floorstanding speakers be placed closer ( less than 3 ft ) to walls?

Thanks
barry

Ethan Winer · « **Reply #9 on:** 3 Jun 2006, 02:51 pm »

Barry,

> What if you can afford to cover both your front and rear wall with bass traps. Does this rule still applies? <

Absolutely! For the best results you want as much bass trapping as possible and you should place the speakers and listening position optimally.

> if you cover the walls with bass trap, can floorstanding speakers be placed closer ( less than 3 ft ) to walls? <

Speaker distance to walls is only one of several factors. But to answer your question, bass trapping does help reduce placement problems. I once tested exactly what you're asking. I put the speakers flat against the front wall of a room with no bass traps and measured the LF response. Then I moved the speakers out from the wall in six inch increments measuring each time. Then I put them back against the front wall and brought in 8 traps. Without traps some distances were definitely better than others. But having traps gave the best response by far, even with the speakers flat against the wall.

--Ethan

95bcwh · « **Reply #10 on:** 3 Jun 2006, 03:41 pm »

Quote from: Ethan Winer

Barry,

> What if you can afford to cover both your front and rear wall with bass traps. Does this rule still applies? <

Absolutely! For the best results you want as much bass trapping as possible and you should place the speakers and listening position optimally.

> if you cover the walls with bass trap, can floorstanding speakers be placed closer ( less than 3 ft ) to walls? <

Speaker distance to walls is only one of several factors. But to answer your question, bass trapping ...

Thanks Ethan for sharing your experience. Sounds like it's easier to solve the speaker placement issues with bass trap. I guess with an extremely small room that I have right now (15 ft length, 10ft width), to follow the 38% rules, I have to place bass traps around my speakers so I can have my speakers closer againts the wall to give me some space between listening position and speakers.

Thanks again. Your advice is invaluable.
barry

michaelv · « **Reply #11 on:** 4 Jun 2006, 04:36 am »

Ethan,
About the rear(back) wall, i have a small window and bare wall. Can i use 2 or 3 2" thick panel and put flat against or spacing out 1 " from the wall to create a bass trap? I already have 4" bass trap on each corner of the room and i put it on floor against the wall and floor corner. Due to the WAF, i can't stack second trap on top of the first one. I don't know if i could lift the trap about 2 feet from floor will help more than laying it on floor.

thanks.

Ethan Winer · « **Reply #12 on:** 4 Jun 2006, 01:46 pm »

Michael,

> Can i use 2 or 3 2" thick panel and put flat against or spacing out 1 " from the wall to create a bass trap? <

Yes, but I'd use more than two inches thick with a one inch gap. Four inches thick with a four inch gap is a lot better because it will absorb to a much lower frequency.

--Ethan

Glenn K · « **Reply #13 on:** 5 Jun 2006, 03:09 pm »

Quote from: michaelv

Ethan,
About the rear(back) wall, i have a small window and bare wall. Can i use 2 or 3 2" thick panel and put flat against or spacing out 1 " from the wall to create a bass trap? I already have 4" bass trap on each corner of the room and i put it on floor against the wall and floor corner. Due to the WAF, i can't stack second trap on top of the first one. I don't know if i could lift the trap about 2 feet from floor will help more than laying it on floor.

thanks.

Bass traps on the floor in the corners work pretty well because you are covering a tri corner.. So I would leave them there.

Glenn

michaelv · « **Reply #14 on:** 2 Sep 2006, 03:05 pm »

i have tried many options and i am almost there.

My configuration right now as followed:
4 (6" ) bass traps . One for each corner
2 (2") first reflection point on left and right speaker.

Plan to add more below:

2 (4") bass traps placed behind the listening seat with 2" gap from the trap to the wall.

I sit 5 feet from the back(rear) wall.

Any other comments would be greatly appreciated.

thanks.

bpape · « **Reply #15 on:** 2 Sep 2006, 06:34 pm »

Sounds like you're on the right track. Have you taken measurements along the way to see what each installation change does in terms of FR and decay time?

Bryan

michaelv · « **Reply #16 on:** 5 Sep 2006, 06:34 am »

unfortunately, i don't have a way to measure it. I'll try to move speaker around again until i can hear stronger bass. Right now, it's ok, but not enough as when i move to the corner, the bass is more defined than the 38% rule

bpape · « **Reply #17 on:** 5 Sep 2006, 11:18 am »

You don't necessarily want 'stronger' bass. The idea is smoother response. The corner, in general, will give you the most output and the worst frequency response.

Bryan

michaelv · « **Reply #18 on:** 5 Sep 2006, 03:00 pm »

Thanks, Bpape.

Would you mind explaining it more in details? Sorry, i'm kind of novice in this area.

thanks again.

bpape · « **Reply #19 on:** 5 Sep 2006, 04:12 pm »

When you place a sub in the corner, you are more strongly exciting all of the room modes because the source is now at the end of all 3 dimensions. So, you're response in most cases will have the largest possible interaction, hence the most severe peaks and dips. However, you're also getting the most pure SPL out of it.

If you want to and have the space, try it by setting it up so that it's at some fraction of 7ths of the room dimension. So, you'd be say 2/7 or 3/7 of the width from the side wall, 1/7 from the front wall, and 1/7 off the floor ( on a strong stand that's well coupled). It may not be optimal but I'll almost guarantee you that the response curve will be much smoother than corner placement.

Bryan