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#418119 - 03/25/16 06:29 PM What to do about a 50hz black hole
MatManhasgone Offline
connoisseur

Registered: 05/06/14
Posts: 1027
Loc: Lost in the great wide yonder
So I finally got my new Anthem AVM60 to play nice in my room with ARC. Got it so the software could see the amp and had it take some measurements.

I know that there is quite a bit that needs to be done inside my room. From the top, I need to get all the boxes and garbage out of the room. I don't have anywhere to put speaker boxes however and have thrown out the boxes for the LFR and VP speakers. I have the sub woofer boxes stacked at the back of the room. I am just going to have to bite the bullet and toss them as I have no ability to store them.

But even with my mess, I did take some measurements and there is a definate black hole in the room sucking out everything around 50hz. Every speaker measures a sizeable dip at that point. it's most apparent on the sub where the spl drops a good -45db. Hence saying it's a black hole.

I don't have the brain power right now to dedicate towards figuring out what needs to get done. I think I will just spend the next month or so trying to get the room looking nice and then hire someone to tackle the mess that I have.
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Anthem: AVM60
Axiom: ADA1000, LFR1100, VP180, QS8, EP500, M3, M3comp
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#418123 - 03/25/16 07:47 PM Re: What to do about a 50hz black hole [Re: MatManhasgone]
Gr8_White_North Offline
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Registered: 07/12/09
Posts: 2272
Loc: Whitehorse YT
Matt this all depends on what you want your room to look like. If you have plenty of freedom plenty can be done using treatments. Room correction can only do so much depending on how un co-operative your room is. The big hole is cancellation. The bass wave basically coming back on themselves which is why bass traps can help by stopping the returning waves. Doing a sub crawl is a good place to start if you have freedom to move the subs around. My space is small with few options so I let Dirac do what it can and live with it. I have done measurements with REW and a calibrated mic but it only showed me what I had and again I am limited though I plan on bass traps once the weather gets better. Start like you suggested and get the room squared away then look into some panels and traps.

Ps ... I know lots of people don't like AVS but I spend time there reading lots of stuff and in between the bickering and what not there is some usefull info. Also Home Theater Shack is a good site and if you post your curves people who know a lot more than me will chime in and lend a hand and it a great place to learn about room correction if you really want to know.
Richard


Edited by Socketman (03/25/16 07:50 PM)
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#418206 - 03/28/16 12:59 AM Re: What to do about a 50hz black hole [Re: MatManhasgone]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10634
Matt, assuming that the "hole" around 50Hz has been measured accurately, it would appear to be, as Richard comments, a cancellation effect, rather than being an inherent artifact of the room itself. 50Hz has a wavelength of about 23'(1120ft/sec/23ft). Cancellations at a particular frequency can occur between different drivers playing it and spaced about a half wavelength(e.g., 11')apart and/or if the drivers are about a quarter wavelength(e.g., 5 1/2')from a room boundary. So you might take note if your sub/speakers separations or their distances from room surfaces are similar to these numbers.
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#418212 - 03/28/16 10:02 AM Re: What to do about a 50hz black hole [Re: MatManhasgone]
nickbuol Offline
axiomite

Registered: 09/16/04
Posts: 5329
Loc: Marion, IA
I'll chime in as well that it is most likely what the other gents are saying. A few strategic acoustical treatments could really do wonders for the "black hole." Try moving things around a bit like mentioned since that just costs some time, but be ready to look at some bass traps. They don't have to be huge monsters in order to provide benefit, it is just making sure that they are big enough to make a noticeable benefit.
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#418224 - 03/28/16 05:04 PM Re: What to do about a 50hz black hole [Re: MatManhasgone]
2x6spds Offline
connoisseur

Registered: 03/16/02
Posts: 3139
Loc: CA, USA
Have you tried the 0* - 180* function? You may also want to check that your main's drivers are in phase. QC deficiencies may have resulted in wiring errors in your speakers. Maybe an equalizer would help though I figure the less in the signal path the better.
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#418231 - 03/28/16 10:23 PM Re: What to do about a 50hz black hole [Re: MatManhasgone]
MatManhasgone Offline
connoisseur

Registered: 05/06/14
Posts: 1027
Loc: Lost in the great wide yonder
if it was a speaker out of phase, would it not kill all the sound coming out of that speaker? I am getting a hole at just 50 but below and above this seems to be working quite fine.
_________________________
Anthem: AVM60
Axiom: ADA1000, LFR1100, VP180, QS8, EP500, M3, M3comp
AudioSource: Amp One/A

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#418235 - 03/29/16 07:03 AM Re: What to do about a 50hz black hole [Re: MatManhasgone]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6789
Loc: The Peoples Republic of Il.

As John points out, it's most likely in the placement of your speakers. It could also be where your sitting position is. Move your seating forward or backward by a foot or two and see if that helps.
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#418239 - 03/29/16 12:16 PM Re: What to do about a 50hz black hole [Re: 2x6spds]
TroyD Offline
aficionado

Registered: 02/17/04
Posts: 610
Loc: Bridgewater, Nova Scotia, CA
Originally Posted By 2x6spds
Have you tried the 0* - 180* function? You may also want to check that your main's drivers are in phase. QC deficiencies may have resulted in wiring errors in your speakers. Maybe an equalizer would help though I figure the less in the signal path the better.


ARC checks the phase when it runs, if I can remember correctly ...... Nickboul ? would know he just ran ARC, I believe.
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#418243 - 03/29/16 04:36 PM Re: What to do about a 50hz black hole [Re: MatManhasgone]
nickbuol Offline
axiomite

Registered: 09/16/04
Posts: 5329
Loc: Marion, IA
Correct. ARC is supposed to check the phase for all speakers, including the subwoofer(s)...
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2-M60s, VP180, 8-M3s, SVS 20-39PCi, DIY Sub, 8-Shakers, JVC RS45, Anthem MRX-1120

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