Odd shaped room with low end grief: tuned or broadband?

[A.B]

Hi all, I’m new to the forum etc.

I have searched out quite a few posts already on this forum, all of them being incredibly useful in understanding the treatment my room needs. However I am still unclear on a few things. Firstly I will explain my set-up:

Currently in a room which is approx 13ft x 13ft ☹ x 7+1/2ft. The room is not a normal shape whatsoever though as although the ceiling is constantly 7+1/2 ft down the centre, but where it joins the walls on either side it curves down to 2+1/2 ft in the back corners. The result is a curved semi-circle type shape when facing the back half of the room, with windows at the very back. I have set up my listening position up the other “normal” shaped end of the room as I wanted to avoid the acoustics of the “eyebrow” shaped end (focal point?). My other issue is that at the normal shaped end, a door is in one corner and shelves in the other. Any treatment I do needs to be temporary as it’s not my property, so moving the shelves is out, and the door needs to open and close fully with no obstruction. The way I see it this leaves me with the front and side walls only for bass trapping, along with the back corners. I currently put my first axial mode at around 42 hz (though this was calculated on the room being a rectangle shape, as I don’t know how to factor in the odd shaped roof). My plan is to super chunk the back two corners, but with them both being short I am concerned this won’t be enough bass trapping. I also have already built 4 bass traps, 4ft x 2ft x 4inches rocksil in wooden frames spaced about 4 inches from the wall: 2 on either side of the listening position to counter flutter echo and two on the front wall. They’ve not made a massive amount of difference to the low end to be honest, so my questions are: to deal with my low end standing waves, what is the best option? More bass traps of the same spec covering the side/front walls? More bass traps of different (please advise) spec covering the side/front walls? Or a tuned panel trap? Also – am I better to fill in the back two corners with fibreglass or build tuned corner traps there too?


Thanks in advance for you help and sorry for the long post!


Alex

[Glenn Kuras]

My plan is to super chunk the back two corners, but with them both being short I am concerned this won’t be enough bass trapping.

In a room your size I would say NO. Your going to need to cover A LOT more corners to get the low end under control.

I currently put my first axial mode at around 42 hz (though this was calculated on the room being a rectangle shape, as I don’t know how to factor in the odd shaped roof).

Mode calculators are to give you a general idea, which they are never 100% right and actually used for planning a build (most of the time). To really know the problem areas you would need to test of the room. See the following FREE program.
Room EQ Wizard Home Page

More bass traps of the same spec covering the side/front walls?

Covering more corners is the ticket. Also you need Thick absorption on the back wall, to help with nulls and peaks coming from that area.

Or a tuned panel trap?

Tune traps are great, but for larger rooms. You have problems though out the frequency range, so broad band will work much better for you.

[A.B]

Hey Glenn – many thanks for the reply, much appreciated! Forgive me, but I have a few more questions/comments.

In a room your size I would say NO. Your going to need to cover A LOT more corners to get the low end under control.

Unfortunately those back two corners are the only two available for modification due to unfortunate door/shelf combo in the front two. I cannot modify shelves/door as the property is not mine. Would putting more traps on the side walls be sufficient?

Also you need Thick absorption on the back wall, to help with nulls and peaks coming from that area.

Thick absorption on the back wall sounds a good plan, but again space is limited. Most of the eyebrow shape is occupied by windows leaving me with a back wall about 2 ½ - 3 feet tall, 13ft across; there is also a radiator smack bang in the middle of this wall (see my very crude Photoshop diagram: http://www.hardbeatsdownload.com/delete/backwall.jpg). Would absorption either side of the radiator on this wall be enough? Also, when you say thick, how thick are we taking here? Would a similar design to my current traps (mounted off the wall leaving an air gap) be best?

To really know the problem areas you would need to test of the room. See the following FREE program.
Room EQ Wizard Home Page

Thanks for the link – I agree this program would be best. I don’t actually have a mic so I will look into borrowing one so I can run some tests!

[Glenn Kuras]

Unfortunately those back two corners are the only two available for modification due to unfortunate door/shelf combo in the front two. I cannot modify shelves/door as the property is not mine. Would putting more traps on the side walls be sufficient?

It would help but not like straddling corners. One thing you could do is lay the panel across the floor/wall corners. Like this picture (upper right picture)



Also you could put the panels on stands and put in corners.

Would absorption either side of the radiator on this wall be enough? Also, when you say thick, how thick are we taking here?

Sure it would help. I would make them 6" thick.

[A.B]

OK great advice – thanks. One more question and I think I’m done! The 6” bass trapping at the back of the room – should I mount this slightly off the wall? Also – I could afford to lose a bit more room at the back – would thicker fibreglass be beneficial?


Thanks for all of your help!

[Glenn Kuras]

Thicker is always better and yes you do want to space it off the wall a few inches if possible.