Can slat/slots help with midrange nulls at MIX

guavatone · Post by **guavatone** » Wed Dec 06, 2006 5:35 pm

I have been ironing out some bass issues and moving up the spectrum every couple days. I plan to post a diary soon. anyway I know this is general, but,

I am seeing and hearing huge nulls in my midrange 1-8k. Can slats help me, maybe space 1/2". I am running out of places where my speakers will have a direct shot on any more surfaces. Will slats help even if they are not in a direct path of monitors. I'll have to figure out how to upload my response, I am not sure if "fuzz measure exports pics.

( I though I had at least a intermediate grasp on acoustics but this is f-ing me up. I have everest's 3 books by my nightable.... hmm , I guess this just shows how dense I am....oh well).

AVare · Post by **AVare** » Thu Dec 07, 2006 3:31 am

Without having any additional information, I would look some reflectiion path analysis to see where the offending reflections are from. At 1k the wavelenght is 1.1FT so the problem is a .55FT differential. I wouild suspect something like a strong reflection of the mixer, or keyboard, etc.

Good luck!
Andre

guavatone · Post by **guavatone** » Thu Dec 07, 2006 7:43 am

Thanks for the reply, and yes, sorry for the lack of info. I played around with placing 2" auralex around the early relfection spots and it yielded no significant results. I have 2 questions:

1. most people say that modes do not affect higher frquencies, but isn't it posible that modes continue to resonate at higher harmonics, eg past 1K?

2. Maybe this problem is with the speakers (Mackie HR24). They read flat within 6" from the monitor. Is it possible they radiate in a strange pattern?

OH! - sometimes I'll get a response that doesn't have these huge nulls, but then 2 seconds later they return. This is a bit strange, but on average the nulls prevail in my measurements.

AVare · Post by **AVare** » Fri Dec 08, 2006 12:34 am

1. most people say that modes do not affect higher frquencies, but isn't it posible that modes continue to resonate at higher harmonics, eg past 1K?

Uh, I don't understand your POV. If you have a room with perfectly reflective surfaces with perfectly specular reflection, nothing to difuuse the sound in the room (like lighting fixtures, furniture, equipment, people, or yourself), then yes. Does the above descrive your room as you use it?

Is it possible they radiate in a strange pattern?

Uh, yes it possible with your speakers. With the lack of additional information it is impossible to say if that is what is happening.

I would look at reflection paths.

Keep us posted!
Andre

guavatone · Post by **guavatone** » Fri Dec 08, 2006 10:40 am

I think I know what you are saying andre, and my reflections are not totally optimal. -my desk could be lower with more angle, and my racks are to the left of my ear by 2 feet. The monitor tweeters are avout 1.5' from he mixer. I don't think anything is 6" away though.

There is a huge 4" OC703 panel directly behind the monitors, but these midrange nuls were there before the 703.

I will buckle down and try to illustrate with smartdraw or sketchup soon.

AVare · Post by **AVare** » Sat Dec 09, 2006 1:11 am

Thanks. The drawing will help alot.

The filtering is caused by a difference in travel distances of half wavelenghts, NOT of of objects being a half wavelength different in distance.

Andre

guavatone · Post by **guavatone** » Sat Dec 09, 2006 4:22 am

AVare wrote:The filtering is caused by a difference in travel distances of half wavelenghts, NOT of of objects being a half wavelength different in distance.

Andre

For some reason my brain isn't picturing this, do you think you could give me an example, or point me to a page in an Everest book?

AVare · Post by **AVare** » Sat Dec 09, 2006 6:24 am

guavatone wrote:
AVare wrote:The filtering is caused by a difference in travel distances of half wavelenghts, NOT of of objects being a half wavelength different in distance.

Andre

For some reason my brain isn't picturing this, do you think you could give me an example, or point me to a page in an Everest book?

Unfortunately I can not think of one off hand. Would anyone reading who knows of a good link to show this, post the link please? Thanks.

Trying to help:
Andre

guavatone · Post by **guavatone** » Fri Dec 15, 2006 8:22 am

here's some sketchup draft of the layout, there's actually more treatment on the walls but it gives the basic idea. The space is awkward and this was what I found to be best placement of the desk and gear. There is a synth workstation to the left of mix as well.

Oh well.... anyone know why this is black?

here is my large sketchup file:
http://www.guavatone.com/free/Guavatone-4.skp

guavatone · Post by **guavatone** » Sun Dec 17, 2006 7:01 am

I got my pics up. Also, I have been testing various spots in my studio and keep getting these huge nulls at 1.4-1.8 KHz. Makes me think it's the speakers. My walls are mostly wood treated with 2" and 1" 703. The ceiling has 703(1" and 2") mixed with some acoustic tiles(10-20%) that were there since I moved in.

Post by **kendale** » Sun Dec 17, 2006 11:57 am

Aloha Charlie,

Any chance you could resize your pics & graph down to about 700 pixels wide, please. (forum guidelines) It'll make following your thread much easier.

Thanks!

Aloha

guavatone · Post by **guavatone** » Sun Dec 17, 2006 12:24 pm

Sorry man, it was a PITA to export them, I had to use a PC.

update on the way

Post by **kendale** » Sun Dec 17, 2006 12:42 pm

Aloha,

No worries!

Thanks for resizing them pics.

Have you considered arranging your setup to accomplish a more symmetrical footprint? Here's some advice I was given (courtesy of Knightfly):

Left/right room symmetry (at least within a foot or two of ear height) is important for good stereo imaging,

A couple of points to ponder:
- Is it possible for you to set up in the upper right hand corner of your room, with your speakers firing down the length of the room? (toward the area where you are currently setup)
- Does your ceiling slope at all, and if so, which way?

Aloha

Post by **kendale** » Mon Dec 18, 2006 1:55 am

Aloha,

- Is it possible for you to set up in the upper right hand corner of your room, with your speakers firing down the length of the room? (toward the area where you are currently setup)

Hmm, I don't think that would work after checking out your skp file.

Here's another design idea Knightfly offered during my design phase:

For your application, a movable panel about 4" thick would help the wall unit "disappear" acoustically - it could be moved against a wall somewhere when not in use.

Would/could something like this work?

Aloha

Post by **kendale** » Mon Dec 18, 2006 1:18 pm

Aloha,

I am seeing and hearing huge nulls in my midrange 1-8k. Can slats help me, maybe space 1/2". I am running out of places where my speakers will have a direct shot on any more surfaces.

After buildng and installing the side and rear absorber panels for my place, the results were a vast improvement:

Update: Finished rear panel/insulation install on side absorbers. (Still waiting for Guilford - they're stuffed, but not pretty!)

Initial listening test: Hey, this stuff really works! Reference cuts sound cleaner, crisp even. Depth perception has improved, and even more refinements of initial improvements posted earlier. (bottom end tighter/ imaging clearer/ drums sound clearer, more defined in mixes/able to hear clearer at lower volumes than before/room sounds quieter without music playing, louder & tighter with less effort when music played/less fatigue/more enjoyment in listening to mixes!)

A lot of the low-mid/mid haze is gone - like somewhere between defogging/cleaning your windshield. It's amazing how much of a difference each step of the treatment makes. Even more so, it's interesting to note how much mush was there in the first place! No wonder that first CD in this location was such a struggle. Rolling Eyes

Food for thought perhaps?

Aloha