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Author Topic: homemade reflexion filter  (Read 45705 times)
rightonthemark
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« on: August 09, 2013, 12:19:51 AM »

i just built a homemade portable vocal booth/reflexion filter.
it was pretty easy and inexpensive.
done for about $25.


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Zax
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« Reply #1 on: August 09, 2013, 02:26:03 AM »

Looks pretty cool, Mark. 
Is it attached to the mic stand, or the wall?

Frank
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rightonthemark
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« Reply #2 on: August 09, 2013, 02:50:04 AM »

Looks pretty cool, Mark. 
Is it attached to the mic stand, or the wall?

Frank

I got it clamped to the mic stand with c-clamp style vice grips --- until i figure something better out.

here's what i used & how i did it...

i used two paint grids.
straightened the tabs.
opened one set of the tabs & slid the other straitened tabs into the open ones & used vise grips to pinch closed.
then shaped the two grids together into a half-circle.
i used air conditioner side panel foam for the dampening.
i had to do some cutting to piece it together since the foam isn't the same size as the paint grids.
used a multi-purpose spray adhesive --- the loc-tite brand i used said it worked on foam & could bond it to metal (among other materials).
once all the pieces were cut i practiced putting them on the grid before i actually sprayed the adhesive on it and applied the foam to the grid for real.
then in the pack of the a/c foam were plastic border pieces that i cut down & put on the ends.
I'm thinking on adding some cardboard or posterboard to the back for a little extra containment.
i haven't used it yet.
probably won't until sometime next week.
but i figure it's gotta be better than nothing.





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Paulo
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« Reply #3 on: December 21, 2013, 06:59:48 AM »

MacGyver culdn't do better  Grin
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« Reply #4 on: December 21, 2013, 11:37:43 PM »

How does it perform ?

The real one has very small holes and a 'sandwich' construction with air gaps to increase it's efficiency.

I place mine in front of a broadband absorber that I made which seems to work pretty well but of course is not portable.

You can see it on one of the pics here  http://www.musicianscollaboration.com/forum/index.php?topic=5296.0

CD
 
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rightonthemark
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« Reply #5 on: December 22, 2013, 12:18:17 AM »

i have since added black fabric to the back covering the metal grate applied with spray adhesive.

as for performance...i have nothing to compare it other than nothing at all. and it's clearly better than nothing.
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« Reply #6 on: December 22, 2013, 10:50:36 AM »

as for performance...i have nothing to compare it other than nothing at all. and it's clearly better than nothing.

You could post a with & without test and see how much drier it sounds

CD
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rightonthemark
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« Reply #7 on: December 22, 2013, 12:37:37 PM »

yeah. I'll do that later this week.


as for performance...i have nothing to compare it other than nothing at all. and it's clearly better than nothing.

You could post a with & without test and see how much drier it sounds

CD
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rightonthemark
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« Reply #8 on: December 24, 2013, 01:01:51 AM »

here's a test of my homemade reflexion filter.
i used the chorus for living after midnight for the test.
first is dry spoken no reflexion filter
second is dry spoken with reflexion filter
third is dry singing no reflexion filter
and last is dry singing with reflexion filter
i used a cad gxl2400 going into a tascam us-600 into reaper.
the room is essentially a home office with carpet on the floor and typical home office furnishings (desk, bookcase, etc --- no wall treatments).
my work station is a cabinet in which i do isolate myself to some degree with the cabinet doors.
i don't think it really made a difference when speaking but when singing without the reflexion filter i hear a sort of hollow ringing that's not there when the reflexion filter is used.
note that the narration did use the reflexion filter and a minimal amount of processing (comp, eq, d-ess --- no reverb or delay was used on this test at all)
« Last Edit: January 01, 2014, 11:05:57 PM by rightonthemark » Logged

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« Reply #9 on: December 24, 2013, 10:06:22 AM »

MacGyver culdn't do better  Grin

Too many pieces for MacGyver. He would have used a single shoe string. Wink Cheesy

Great job, Mark! I wouldn't even have enough imagination to figure out how to do this.

Regards,
  Steffen
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« Reply #10 on: December 24, 2013, 10:28:35 AM »

Hey Mark

It doesn't sound like you have too much of a problem to start with, the samples with no filter don't really sound particularly coloured by room sound.

Whatever the difference it's very slight...I think if you blindfolded me and asked me to spot the difference I may be hard pressed to tell you although room sound can rear it's ugly head more under heavily compressed signals as it brings up the background ambience so it may be easier to tell apart in an real mix situation.

It's funny that we're talking about this as I was reading this month's SOS Mag and there's a good point in there about these kind of relection filters.



Q Why are Reflexion Filters used behind the mic if the mic picks up sound from the front?

Published in SOS January 2014

Sound Advice : Miking
Hugh Robjohns

I've noticed that a lot of companies now market a variation on the curved screen theme to go behind a vocal mic, with the claim that these devices exclude the room acoustics and give you a cleaner recording. But surely, most vocal mics are cardioid pattern, which means they pick up sound only from in front — so how can a screen behind the mic help? Am I missing something or are we being sold smoke and mirrors?

Fred Savage via email

SOS Editor In Chief Paul White replies: If you look at the polar pattern of a cardioid pattern mic, you'll see that, although they are indeed most sensitive at the front as you suggest, the sensitivity doesn't fall by much by the time you're 90 degrees off-axis so they can also pick up quite a lot of sound from the sides. Furthermore, their HF response falls away once you're off-axis so what comes in from the sides can end up sounding somewhat dull. Indeed the only place that approaches being completely 'deaf' is a very narrow angle directly behind the mic.

A curved screen reduces the amount of reflected sound reaching the sides and rear of the microphone so 'room reverb' can significantly be reduced. However, such screens can't intercept sound reflecting from walls behind the vocalist, which is why we always suggest combining these screen, with an absorber of some kind hung behind the performer. This could be acoustic foam, mineral wool or a good old thick and cheap polyester duvet, and if you can arrange your screen in a curve or V shape so that it also intercepts some of the sound approaching the microphone from the sides, this combination of a commercial screen behind the mic and an improvised screen behind the performer can be extremely effective. In low ceiling rooms we sometimes go one further and suggest a foam panel above the mic and vocalist to prevent ceiling reflections from reaching the mic.

While such lightweight screens have little effect at low frequencies, they actually work very well in the vocal frequency range and the same tactic can be applied to non-bass acoustic instruments where necessary, such as acoustic guitar. Smaller curved screens are also available to fit behind instrument mics where space is tight, and these can be useful fitted to drum overheads to reduce the effect of ceiling reflections.

As you may well have discovered already, a bad-sounding room reverb can't be disguised by adding a good-quality artificial reverb, so any technique that helps dry up the sound at source is worthwhile, especially in the smaller rooms that tend to get used for home studios. So, the short answer to your question is that such screens are not just smoke and mirrors, but they do benefit from a bit of help from a duvet or two.  .
« Last Edit: December 24, 2013, 10:30:33 AM by CosmicDolphin » Logged

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rightonthemark
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« Reply #11 on: December 24, 2013, 05:44:12 PM »

thanks guys.

Steffen...i found this on youtube. I'm not that creative either.

Mark...yeah, i didn't hear a difference when speaking; only when singing. there was just a sort of hollow sounding ringing in my headphones.
and the room itself isn't really "live" sounding to begin with.
besides typical home office furnishings the walls are a bit different than most homes.
we had a fire a few years ago and when the reconstruction was done they put new drywall overtop of the old plaster walls. so with carpet on the floor it is a pretty dead room. and i do kind of isolate myself with the doors of the cabinet that houses my laptop, interface and the rest of my gear.
the test will be when i go to record a band in their crappy jam room (a basement or garage).
when that happens I'll see if i can do another test and post it up here.

thanks again...

Mark
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Mimmo
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« Reply #12 on: July 09, 2015, 03:24:53 PM »

I didn't see this post before...I made mine  with a wire coat hanger and some foam material I found in an apartment I renovated...The tenant there was also in recording...He left everything that was attached to the walls. I got to take it home and used it in my sound room. I put most of it on the ceiling


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« Last Edit: July 09, 2015, 03:26:39 PM by Mimmo » Logged

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