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Desk reflection Channel Strips
Old 11th December 2014
  #1
Gear addict
 

Thread Starter
Desk reflection

Hello,

After reading DanDan post on desk reflection I resize my desk and speaker placement. I have a big dip around 650. I have put up to 3 moving blankets, raise/lower desk, tilt forward/backward, slide forward/backward but this is the best i can get it. I can move the desk completely and get great freq meas but that's not an option for me. I don't want to work with the desk to the side of me.

I have the speakers 4ft from front wall and 10ft from side walls. I'm sitting 6ft2" from front wall with speakers at 3ft distance from my ears and all sounds great. I been listening to a lot of well mix music to get use to the speakers being that close. I never like my speakers that close until i found the spot I'm at now and both pair sounds great and very revealing.

Any thought on what causing the dip. I have place blankets around the desk floor but nothing helps. I have the a77x vertical with the mid woofer on bottom and bass woofer up top. Its sounds best and give the best freq meas so it has to be the mid woofer and desk interaction.

Any help is welcome.
Thanks denlig
Attached Thumbnails
Desk reflection-adam-a77x-both.jpg   Desk reflection-adam-a77x-both-waterfall.jpg   Desk reflection-adam-a77x-both-rt60.jpg  
Old 11th December 2014
  #2
Gear addict
 

Thread Starter
Desk Reflection

This is the little desk. Nothing fancy but works for me. I think the measurements is good compared to measurements of others i have seen. I would like to fix the dip if possible without making other parts of the freq worst. I thought maybe I was getting bounce off the over head beam but after putting 2" foam and a fold up thick moving blanket it also make comb filter worst.
Attached Thumbnails
Desk reflection-studio-measurement-pictures-12-10-2014-019.jpg   Desk reflection-studio-measurement-pictures-12-10-2014-017.jpg  
Old 11th December 2014
  #3
Lives for gear
Hi denlig.

Some ignorant comments-- That is a nice-looking setup and an excellent freq response as far as I can tell.

Your graph seems to indicate the null in the ballpark of 750 rather than 650?

If caused by a muti-path cancellation, the difference in flight-distance of direct audio versus the travel distance of the reflection ought to be in the ballpark of 1130 / (2 * 750) = 0.753 feet. Or about 9 inches. Or about 230 mm.

If reflecting off something between you and the speakers, there would be one measurement for the direct path from speaker to ear. Then there would be a triangle-bounce of two coincident angle lines off a surface. The total distance of the reflection path would be about 9 inches or 230 mm longer than the direct path.

If it is bouncing off the desk, perhaps a vertical absorber that extends higher than the desk level, between the desk and speakers? Behind the desk and in front of the speakers. But not tall enough to block the speakers from your ears.

That might block the speakers from shining on your desk surface. But maybe it is some other surface. Just some dumb ideas for what it's worth.

Or it might be multi-path from ceiling, back wall, or whatever. The difference between direct and reflected, in theory, would theoretically need to be in the ballpark of 9 inches. If it is a multi-path direct cancellation.

If it is the desk, and curable by an open on the front and back absorptive panel between the desk and speakers, am guessing the panel would also need to be open and absorptive on the top of the panel. If the top of the panel was a wood board, it might fix the desk reflection but cause a new reflection off the top wood board.
Old 11th December 2014
  #4
Gear addict
 

Thread Starter
Thanks jcjr,

It sound amazing at the mix position.

I ran test tone from 800hz to 600hz and i don't hear any cancellation at mix position. I also use spl meter at the mic position with only a db or so different.

I have tried thick 10" pillows over top/bottom, both sides but everything makes worst in other freq. If i angle the desk to reflect the reflection from the mic position it helps but make the comb filtering 10 times worst.

I'm thinking if it's a bounce off the desk and then the beam over the mix position would it need thick treatment to flat out a freq of 750 hz ?

Also i notice that it's a strong low end tone behind the speakers. I have covered the front wall and computer screen with thick moving blankets and cover the back wall diffuser but very little change. The cancellation is to severe to just leave it alone. I just hope It will be an easy fix and that i don't have to do any odd over the beam trapping.

I will try raising the desk up again to see if i can make the bounce miss the mic.
denlig
Old 11th December 2014
  #5
Lives for gear
 
jhbrandt's Avatar
Dennis,

Hey man! Send me an email, let me know when we can get on Skype together and we'll go over the testing together. It's part of my service even though it's been over 3 years.

I'll help you find the issue and fix it.
Cheers,

John
Old 11th December 2014
  #6
Gear addict
 

Thread Starter
John,

WOW !

It's been a very long time since we completed the studio. As you know I suffered major water damage that really put a hurting on my heart. I also had to sell some of my best eqp to finance the rebuild. I wasn't expecting to use your service every time something go bad or when i change desk size of speakers.

Your service was complete years ago so that's why I was asking for help here. I was hoping someone else has been thru this and had a quick answer/fix.

Since we are on a different time zone I will email you later tonight and hopefully we can chat.

Thanks for the extended service John.
denlig
Old 13th December 2014
  #7
Gear addict
 

Thread Starter
Solved

I fix the problem by putting the speakers back horizontal, moving them around to 4ft from the test mic and Placing the racks next to the side of desk. This fixed the problem at 700-650. I'm getting a little more desk reflection in the upper freq with the speakers further behind the desk then before but placing small pillows on the corner of the mixer controller fixes that also.

Also the roll off at 10-20khz has straighten out. I still have the nulls around 100hz etc and while running test tone I'm getting strong build up on both sides of my rear bass traps. I will work on flatten out the lower end more after I finish some old mixes of clients.

denlig
Old 13th December 2014
  #8
Lives for gear
Per your earlier chart, those Adam A77x seem capable of kicking serious butt to below 40 Hz!
Old 13th December 2014
  #9
Gear addict
 

Thread Starter
jcjr,


They do pretty good. I crank these alot and I've never heard them poop/fart out. The air coming from the ports drives me nuts tho.

I ran test tones from 10hz up to see what I hear and the first low tone I heard was 24hz and a good tone at 32hz. I was just testing to see how low my ears could hear.

denlig
Old 6th February 2018
  #10
Quote:
Originally Posted by denlig View Post
John,

WOW !

It's been a very long time since we completed the studio. As you know I suffered major water damage that really put a hurting on my heart. I also had to sell some of my best eqp to finance the rebuild. I wasn't expecting to use your service every time something go bad or when i change desk size of speakers.

Your service was complete years ago so that's why I was asking for help here. I was hoping someone else has been thru this and had a quick answer/fix.

Since we are on a different time zone I will email you later tonight and hopefully we can chat.

Thanks for the extended service John.
denlig
I was curious to know if you ever fixed your reflective issues ?
Id love to know what you did.
Old 3 days ago
  #11
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jhbrandt's Avatar
Quote:
Originally Posted by dreckdirect View Post
I was curious to know if you ever fixed your reflective issues ?
Id love to know what you did.
Derek,

He did!

post #7 .
Cheers,

John
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