# 50hz null............Suggestions



## bigbang (Feb 20, 2007)

So below is where I am at with no room treatment (to speak of anyway). This is stereo dipole speakers (Carver Platinums) with no sub and no intention of adding one.

I've got a null centered at 50hz and this is as good as it gets with speaker placement and combination of open/closing doors/closets.

Will corner traps help this?


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## Ethan Winer (Jul 21, 2006)

bigbang said:


> Will corner traps help this?


Yes, but you'll need a lot of them to reach that low. However, even a modest number of traps is worth doing because you have problems at other, higher bass frequencies too.

--Ethan


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## bigbang (Feb 20, 2007)

The one between 40 and 60 is the most noticeable though. Very noticable actually.

I thought the rest looked and sounded fairly good considering there is currently no treatment. Am I missing something?


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## bpape (Sep 14, 2006)

You're missing decay time. It's not just frequency response.

Also, you made no mention of having tried shifting seating position. The null could easily be seating position related.

Bryan


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## bigbang (Feb 20, 2007)

It's prevailent throughout the room with the exception of one corner of the rear/listening side of the room.

What should I be shooting for for decay times ie what's realistic?

Sorry for the noob questions and thanks for the replies.


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## tonyvdb (Sep 5, 2007)

What sort of receiver/preamp are yo using? do you have an external amp powering your mains if so an EQ would do wonders.
EDIT: Have you tried moving your main speakers out from the wall or closer to the wall behind them?


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## bigbang (Feb 20, 2007)

I'm running a pre in to mono amps for each speaker.

How can an eq help in solving my null?

Is my graph that bad? 

I've done a search to compare and don't really see much. What I do see looks worse as far as fr goes and on the waterfalls the decay times usually arent on the graph.

What is an acceptable time to reach the 60db mark and just how even throughout the bandwith can be expected and/or acceptable?


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## mike c (Apr 25, 2006)

worth a try, but I solved my 50hz null with a second subwoofer 

or the boring way is you can just re-locate the subwoofer/listening position.


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## tonyvdb (Sep 5, 2007)

bigbang said:


> I
> 
> How can an eq help in solving my null?


An EQ will boost the missing or low frequencies given that its only one area thats bad a simple 9band EQ will easily do the job but a 1/3 octave two channel EQ would be the best. Used they can be found on ebay for cheep.



> Is my graph that bad?


No its not that bad but as I said a 1/3 octave EQ will fix all your issues.


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## Ethan Winer (Jul 21, 2006)

tonyvdb said:


> a 1/3 octave EQ will fix all your issues.


If only...


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## tonyvdb (Sep 5, 2007)

Ethan Winer said:


> If only...


LOL, ok so I'm a bit of a optimist. But it would help allot.


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## bpape (Sep 14, 2006)

For EQ, I wouldn't have anything but a parametric. Even a 1/12th or 1/24th octave is a guessing game to try to get lucky and match what you need to their band centers - not to mention Q.

If the null is all around the room, answer me this. Is it all through the room standing up or sitting down or both?

If it's everywhere in the room, it's almost got to be something in the setup. Quite honestly, looking at your graphs, the FR is actually pretty good. You're within about a total of 5db up to 100Hz except for a small bump about 38Hz. 

Realistically, if you can get +/-4db in a room - especially without a sub - you're doing very well. I personally wouldn't mess with it. Target decay time will depend on the room size.

Bryan


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## bigbang (Feb 20, 2007)

Least amount of null is in between speakers. Bad on one side and worse on the other. I'm pretty sure it's just the room.

I'd never consider anything but a PEQ for something like this, but only after room treatment.

I'm thinking a panel type across the corners to start with. I'm already in good shape above 300hz.

Am I on the right track? Does filling in the corner behind the panel help/hurt low end absorbtion?

Typical decay for 200hz and below in a 16x17x8 would be?

Thanks again for all the input!


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## bpape (Sep 14, 2006)

Corners are always a good first choice.

In a room like that for 2 channel, I'd be looking around .35 in the midband, slightly lower at the top, that or slightly longer in the bottom. Now, those numbers are for RT60 (60db drop) Your graph from the average level is not quite 50db

Bryan


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## omholt (Jun 5, 2007)

Helmholtz resonaters is the best option to treat bass that low.


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## bpape (Sep 14, 2006)

Sealed wooden membrane absorbers can also be used to good effect and are a bit more broadband and not so particular as to placement. In either case (membrane or Helmholz) you'll need a decent amount of square footage of them to make a good difference as they're not nearly as efficient per square foot as other types of absorbers.

Bryan


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