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Making muy own acoustic panels

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almikel   

I doubt such a narrow Q dip is audible (the one around 160Hz)

the broad dip around 55Hz would be

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Bilbo   

Yes, I'm still trying to get rid of that one!

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You're right in saying the suckout at 55Hz would be audible. Bass is really lacking in impact at the moment, and music sounds a little hollow.

 

Smoothing out the low frequency response is definitely one of my main targets, as well as reducing decay times across the full spectrum. 

 

I figure multiple subs will be the solution for the first issue, and room treatments for the second. 

 

 

 

 

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almikel   
18 hours ago, iversons13 said:

You're right in saying the suckout at 55Hz would be audible. Bass is really lacking in impact at the moment, and music sounds a little hollow.

 

Looks like you have 1 sub already from the frequency response

Have you tried different sub positions for that suckout?

Also try some phase adjustment on the sub assuming it has some.

 

Definitely not saying don't go multiple subs - just that you may be able to get a better result with what you have now.

 

cheers

Mike

 

 

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almikel   
On 7/6/2017 at 0:47 AM, iversons13 said:

Thanks for the info almikel and Bilbo. Even though I have a dedicated theatre room I really only have the real estate for superchunks about 600mm wide, but can go floor to ceiling in all four corners.

 

600mm wide superchunks floor to ceiling in all 4 corners will make a significant difference.

 

As mentioned above, if going with superchunks, normal fluffy batts cut into triangles 600mm wide on the hypotenuse stacked floor to ceiling will work well.

That's lots of cuts to make.

As much as I hate fibreglass, they will be easier to cut neatly compared with poly.

That said, fluffy poly is easier to cut than Polymax XHD (and way cheaper).

 

Buy a bag of Greenstuf Poly batts for approx $35 and try different cutting methods.

 

A quick calc shows the sides of the right angle triangle with 600mm hypotenuse are 424mm, so the 430mm wide batts would be perfect.

You can even get rolls that are 430mm wide like this

http://buybuildingsupplies.com.au/r20-underfloor-insulation-116m-430mm-roll-pack-p-28424.html

that link there is a minimum order though - but that was 1 Google search

 

Mike

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aechmea   

I didn't built a box/frame at all.

 

I just got Mrs. A to make covers from a linen/hessian material for the full (2400 x 1200 x 100) and half sheets of 32kg and 64kg fibreglass.  They are rigid enough to be self supporting (propped up against something) and I can place them wherever I want.  One covers a doorway! and at one time I had 2 in a teepee formation out in the room.

No walls were drilled/damaged and the lot can be thrown away at any time with no lasting effect.

 

I have a lot of fibreglass.  5 full sheets and 2 half sheet plus 10 DIY tube traps made from sectional pipe insulation (= pre-formed round tubes).  This is effective down to about 80Hz or maybe a bit less, but doesn't help much below that.  Positioning is the best solution at those freqs.

 

The number 1 thing that fixed my initial problem with the world's largest suck-out from 30 - 50Hz, was to move a sub from the front of the room to the back wall where it did not suffer from SBIR at those particular frequencies.  You have to be a bit adventurous with sub positioning to get the desired result; neat, tidy and out-of-the-way is unlikely to work.

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Nigel   

Mrs A is very tolerant.

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@almikel

Yeah I'm running one SVS PB-12 Plus, equalised using a SVS AS-EQ1. The sub is located at the front of the room, between the L and C channels. I've tried all available spots along the front wall, but they were actually a little worse. I've also tried running a second sub (albeit a far less capable one) in the back right corner, and those results were even worse again. Phase could be worth a try. I must admit I just relied on the AS-EQ1 to make that decision. 

 

I'll post up the measurements I took during that process just in case anyone is curious. 

 

Thanks a lot for the bass trap suggestions too. Definitely going to look into the poly. I've read that industrial scissors might work to cut it down...now I just need to work out what industrial scissors are!  

 

 

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jrhill   

You might just get those subs off the floor too and well out of the corners/sidewalls - there's papers published by the Harmon company about this (Welti & Devantier is very clear, for example) are quite applicable to hifi rooms rather than just pro-audio situations

 

As Mike has said 'a few times' - get the bass right first, despite the difficulty - a long term project for most of us unfortunately

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almikel   
7 hours ago, aechmea said:

The number 1 thing that fixed my initial problem with the world's largest suck-out from 30 - 50Hz, was to move a sub from the front of the room to the back wall where it did not suffer from SBIR at those particular frequencies.  You have to be a bit adventurous with sub positioning to get the desired result; neat, tidy and out-of-the-way is unlikely to work.

Aechmea has said it numerous times before, and I agree - Speaker Boundary Interference Response (SBIR) is often a bigger issue than modal behaviour.

 

33 minutes ago, jrhill said:

You might just get those subs off the floor too and well out of the corners/sidewalls - there's papers published by the Harmon company about this (Welti & Devantier is very clear, for example) are quite applicable to hifi rooms rather than just pro-audio situations

 

this advice will help to identify if that dip is room or position related (ie modal or SBIR), or something else (eg crossover).

For mid-bass drivers I like to keep them close to the floor to avoid "ground bounce" SBIR issues, but subs go where they need to go to achieve the best room response.

 

Ken Tripp (a member here on SNA) has a great SBIR calculator

http://tripp.com.au/sbir.htm

 

If you move the sub around, and the frequency of the dip changes, then the dip is likely SBIR related.

If the frequency stays the same, it's likely modal, unless that happens to be the Xover pt between mains and sub.

 

3 hours ago, iversons13 said:

@almikel

 Phase could be worth a try. I must admit I just relied on the AS-EQ1 to make that decision. 

 

I'm not familiar with the AS-EQ1 - but these days the DSP is pretty clever (mostly ;) ) - so probably not Xover or phase related.

I don't let my DEQX decide on much in the bottom end - I prefer to do a manual setup based on measurements, then measure again and tweak - but that's just me.

 

Ignoring all of my post above, if you install superchunks in all 4 corners it will clean up the mid bass markedly and make a big difference to the "in room" sound.

 

Below 100Hz, in my room which has a lot of absorption, I've found EQ to be very effective, as long as you're not trying to "fix" Xover/phase issues between mains and sub, or SBIR issues.

Modal "peaks" below 100Hz respond very well to EQ, so do shallow dips - don't attempt to EQ deep dips.

 

if you want to shoot for the best room response, I'd recommend the following reading:

Paul Spencer's Bass integration guide part 1 of 3 linked below

http://www.hifizine.com/2011/06/bass-integration-guide-part-1/

 

And the Acoustic Frontiers Measurement Standards Guideline

http://www.acousticfrontiers.com/wp-content/uploads/2011/10/acoustic_measurement_standards.pdf

 

Consider the Acoustic Frontiers' paper as the "Gold Standard" target - but don't get disillusioned if your room doesn't meet it - even after treatment - my room doesn't meet their spec and I've got a fair bit of treatment and EQ in a lightly constructed room.

That said, the bass response in my room is better than any other space I've critically listened to (in a domestic stereo environment).

Once you hear a room with the bass under control - you can't go back...

...be careful - you may find the sound in cinemas (bars/nightclubs/concerts) just doesn't cut it anymore :(...

...but the upside is you can't wipe the grin off your face every time you crank the stereo in your own room!

 

cheers

Mike

 

 

 

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Bilbo   

In the Acoustic Frontiers paper can anyone tell me what RC20 in "Noise Control" actually means?

Sorry if it's a dumb question.

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marten   
On 7/5/2017 at 6:13 PM, almikel said:

when applying room treatments I just ignore resonances at 50/100Hz that don't decay - they're always power supply/earth loop related, and hardest to pin down in active setups with many amps.

This is a whole different topic to room treatment, but IMHO only needs to be addressed if you can hear the hum at the listening position

 

Mike

 

Thanks Mike, a very astute observation.  Most likely to save me and other readers time when interpreting our REW graphs.

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frankn   
On 5/18/2017 at 7:43 PM, jrhill said:

Ah Frank, my mistake - sorry, but you get the gist of it, yes?  

On the other hand, BDA isn't just another studio either - have you any if his discs?

Hi @jrhillYes I have all the SoundKeeper albums from BDA..  Sound nice

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Bilbo   

I came across this YouTube video which may provide a use for old towels.

Not sure the testing regime is that accurate but the results are impressive for the cost.

 

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