# help with further construction off cinema / music room sloped front and rear wall



## mikesp1

*help with further construction of cinema / music room sloped front and rear wall*

Hello,

I would love to hear some tips for improving my music/ cinema room
Room is about 3.55m X 6.35m x 2.3m high

I am concirned about the sloped front and rear wall and how to treath them well, should i make the front wall completely death?
I have the idea to instal an acoustic transparant projectioj screen about 1.2 m from the front wall and maybe put the front speakers behind the screen.

Right now everything is harsh sounding with no imaging, kind of compressed sounding, boomy aswell. All energy seems to stay in front of room.

I will do everything that is necessary to turn this in a well balanced sounding room. So all your tips are welcome and much appreciated!

by the way here are first pictures and measurement 1/24 octaaf smoothing:

red is front speakers only
green is with sub x-over 80Hz


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## chrapladm

What EQ is being used?

1.2m baffle wall with acoustic dampening would definitely deaden the boomy sound.


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## mikesp1

Would you place the absorption behind the speakers or on the sloped ceiling above the speakers, also what thicknes?


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## chrapladm

Have you seen GIK acoustics videos?

This is how I learned what to do.
http://gikacoustics.com/treated-and-untreated-listening-room/

There are many other videos there also that will help you in choosing what you need. I am no expert but Bpape or others I am sure will help you.


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## mikesp1

thank you for your kind help, any advice is much appreciated as i am in the progres of learning.


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## bpape

Front wall should be 100% dead with something like 2" 703 or ECOSE. Front corners you will want chunk style bass absorbers. A false wall will allow all of that to be done but not seen for a nice clean look.

Rear wall - I prefer to use 6-8" thick panels, potentially with diffusion pending how many rows and how close the seating is to the rear wall to allow the diffusion to develop properly.

The dip around 120Hz is likely a phase cancellation off of the side walls. Could also be the front wall in which case you'd want to thicken up the center of the front wall to address it. 

Bryan


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## mikesp1

Bryan,

thanks for helping me out.
this raises another question: will this treatment have an effect on the rear ports of the front speakers?
Also my subs are frontwall firing and have a passive radiator pointing in listening direction.

if room is 60% music and 40% movie, does the entire frontwall still have to be 100% dead?


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## bpape

Front wall dead will not hurt 2 channel and will definitely help home theater. Should not impact the rear waves being only 2" thick.


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## mikesp1

I can make front corner absorbers a large as 47" each side of his corners or 120 cm and 130cm or 52" high filled with 703 or glasswool.
Good idea or too much absorption?


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## bpape

Don't know that you need 47" wide. Maybe 24" wide and 12" deep?


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## mikesp1

Bryan thanks a lot for your feedback.
I will continue building in steps starting with the front wall and make mesearements between each steps and post here.

It would be great if you can give me further advice between each steps.


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## chrapladm

Do you have a picture of his room or crude drawing at least?


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## mikesp1

For pics, please see first page of this tread.


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## chrapladm

Ok sorry. You were talking about the room earlier then mentioned "his," so I thought maybe there was another room you were doing. Was just confused. Understand now.


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## mikesp1

Installed two superchunkcks in front.
New measurement 1/24 octaaf smoothing.
Altough i think sound has improved, i do not see much progress in the measurement.

All advice is much appreciated.


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## bpape

waterfalls looks pretty good. 30 will be tough to address. The ply across the front may be resonating.

Looks like the overall sub level is too high. 

Pull the mic forward or back a foot and see what happens to the null around 120


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## mikesp1

Tommorow i will try to adres the 120hz null and post here.
Maybe i can tame the 30 hz region by putting one of the subs behind the listening position and leave the other in place, will try tommorow.

What about 120 till 800hz range, i see many dips aswell?


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## mikesp1

front wall is treated New measurements:


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## mikesp1

mic 4.2 foot to the front. this is middle of room!
120Hz problem is smoothed out, altough this position gives best sound this seating position is not doable for me bacause of too close to the screen.
Its strange that in my room sitting in the exact middle gives best overall pereformance, i think it has something to do with the sloped ceilings.
I could install a new backwall without sloped ceiling but that would decrease room size by aprox 3.2 foot, maybe the experts can tell me to do so or not?
There is also a doorway without door on the right side of the couch, i can remove that doorway?


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## mikesp1

One sub behind couch in red.

Backwall is made of one layer drywall, you can see in the graph that its resonating on multiple frequencies when i place one sub behind the couch.
Maybe this wall is making cancellations with frontwall and therefor best performance is in middle of room?


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## bpape

That's possible that you are introducing a null to compensate for the resonating wall.


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## mikesp1

Bryan,

When i place the mic closer to the front speakers aprox 4.2 foot, the 120 hz problem is gone.
What is your conclusion to this? 

Thanks,
Mike


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## bpape

It could be either a modal problem or a boundary interaction from reflections on the side walls. Try going back to where you were and measuring a foot off to one side and see what happens.


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## mikesp1

Bryan,

I have made the frontwall completly dead like you suggested.
There is much more imaging and i can hear things that i could not hear before because of frontwall reflections. It seems treathing the upper wall, from where the sloping begins made a hugh improvement regarding reflections.

But, i find the room sounds too dead right now, its not pleasant listening to music, ht is fine..

As for the 120hz problem, i have not measured but moving my head one or two foot to the right or to the left does not seem to help. Moving head two foot to the front, and bingo everything is there...but that is on middle of room and not doable with movie watching.
Its not only 120hz related, overall performance is much better two foot the front.

What do you think, has it something to do with the one layer sloped back wall? Is it possible the low frequencies go trough this one layer drywall and are stuck in the 2meter cavity bhind?

Also the entire ceiling is one layer drywall with lots of cavity behind, i am thinking this is acting like a helmholz resonator...

I am willing to do anything to make this room sounds great!

THANKS A LOT!


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## bpape

Well, 2 channel and HT are different design goals. If moving forward fixes the problem and nothing else has, then moving is the answer. This is why one gets the seat right first, then picks a screen size.

Bryan


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## mikesp1

Hmm, well i am not moving much further.
Goal was 60% music, 40 % ht

I made some progress ( rew wise )but also moved backwards.

Still a lot of questions stay unanwserd.

MORE CONFUSED THAN BEFORE!


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## AudiocRaver

Personal opinion: a well-controlled room may sound a bit dead, but dead (acoustically) beats poorly controlled any day. And great imaging is the best goal you can reach for with 2-channel. Give yourself a chance to start discovering more detail in the music and I'll bet you never want to go back to a more live sound. Just a guess.


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## bpape

I would agree 100%. It is very different certainly than what you're used to. If you live with it a while and then were to undo it, you'd be surprised how quickly you'd go back.

You can use a thin facing like some 5-10 mil plastic high on the front wall to minimize the high frequency absorption from that portion but you still want the middle of the wall full range.

Bryan


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## mikesp1

You guys are probably right, i am alreay finding it a bit less dead.
New question: what about ceiling, its about 2.3 m high and i am planning on installing a star ceiling, do i have to absorp it also? Or leave it?


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## bpape

I wouldn't do the whole thing in absorption. Maybe just the reflection zone and leave the rest live.


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## mikesp1

While i was further studying room treadment, i found this:


Highly Directional Speakers (horns, rear-absorbed electrostatics, ribbon panels)
With more direct than reflected sound placement is usually easier. Electrostatics and 
ribbons with wider horizontal dispersion require greater care in placement.
Spaciousness: fair to good
Localization: fair to excellent

Actualy i am using horn speakers, so it could be possible that afterall there simply is not enough reflected sound (ambiance, spacines) anymore...( complete frontwall, first and second sidewall reflection points are already treated.)


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## mikesp1

Well, i have my sound back!!! And i dont have t move to the front.

By turning the isolation ( i have a diffusor) in the first reflection zones so the aluminium is facing frontwards, i have my sound back, front stage is hugh, refind, voices are super, image is good, ambiance is greath and even bass and midbass are a lot better and refind.

One problem, i can hear the aluminium vibrate from time to times.

this is defenitly de way i have to go but need a solution for the vibrating aluminium.
if anyone as a solution i am curieus to know!


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## bpape

remove the aluminum and cover with thin plastic - something like maybe 5 mil or so. That will still give you some highs back but be easier to stretch tighter.

Bryan


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## mikesp1

Bryan thanks again for the recommandation, will try it tommorow.
I also did a quick test and covered the isolation with mdf, it gave not the same result as with the isolation covered with aluminium, i think the latter diffuses more...gives also some mid absorption aswell.

Sometimes you can not follow the standards, trial and error...


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## mikesp1

Frontwall is almost done, i removed the resonating ply on the upper sloped ceilig and covered with fabric.
This made a huge difference!!!

In the second step i removed the resonating ply on the backwall aswell, behind the ply is 8" of isolation covered with plastic.

Soundwise this is even worse than before on the graph i can see that the huge dip on 120Hz has moved to 90Hz.

Should i cover the backwall less absorbing and cover with MDF or something?
Behind the lower backwall is some cavity, should i cover this also with MDF or use it later for maybe a pannel absorber?

Your help is much appreciated!


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## bpape

Is the last picture your rear wall?

Bryan


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## mikesp1

yes, thats correct, 2 last pictures are rearwall


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## bpape

By removing the ply, you've essentially uncovered the 'horn' in the rear of the room. I think the absorption in the rear is still a good thing. I would try some MDF on the REAR (hidden) side of the rear wall. Cover the front(exposed) side of the insulation with some 5-10 mil plastic and then fabric.


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## mikesp1

Bryan,

"5-10 mil", do you mean milimeter?


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## mikesp1

oh i see its 0.127 to 0.254 milimeter!

25,4 × 10-6 meter (0,0254 mm)


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## bpape

Sorry. When measuring thin sheet goods, a 'mil' is 1/1000 of an inch. So .005 to .010 inch plastic. Think of a disposable drop cloth.

Bryan


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## mikesp1

Hi Bryan,

Today i started reinforcing the backwall from behind but i could not manage before removing the front ply. When the front ply was removed i couild not resist taking a new measurement.

First rew graph (blue): upper and lower ply removed from backwall
second graph: (red) only upper ply removed from backwall
(green) backwall untouched

What are your thoughts and recommandations?


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## bpape

what is what?


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## mikesp1

A different front firing sub.


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## mikesp1

rew graph with blue curves: upper and lower ply removed from backwall
second graph: (red curves) only upper ply removed from backwall
(green curves) backwall untouched, upper and lower ply is not removed


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## bpape

Just shifting problems around pending the room length. Really hard to tell much until we get something solid back there.


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## mikesp1

Ok thanks Bryan,

Will report back when rear wall is finishes!


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## mikesp1

Installed reinforced backwall.

New graph

Blue: starting point
Red: reinforced backwall two layers mdf
Black: one sub behind couch (not listenable!)

I see no improvement with new backwall, as tou can see more above on this page the 24 to 80 Hz region was almost perfect flat without lower backwall removed.

How to move further...? Superchuncks on backwall?


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## bpape

Looks to me like it's a sub position issue - listenable or not, that fixes the big null down low.

500-2k is also much better this way.

The wall is just providing a boundary that's more predictable. It will still need to be treated.


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## mikesp1

Ok Bryan,

So what do you recommend, 24" superchuncks in corner of backwall, 8" rockwool covered with plastic (surround speakers ambiance) in middle of backwall?

I can treath the left and right wall corner to ceiling with 1' chunks aswell, good idea or not?

Thanks for your kind help Bryan!


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## bpape

Front corners with chunks and the center of the back wall as thick as you can tolerate. Hold off on the other unless you need it.

Bryan


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## mikesp1

Ok, backwall is 3.6m wide, 1.4m high, at 1.4 m the sloped ceiling begins ( wich we already treated by removing the ply, after the removed ply is 8" rockwool covered with plastic) so do i tread the entire lower backwall 3.6 x 1.4 or just, lets say 2m x1.4 m and leave the corners untreated?

Front wall is already treated with 24" superchuncks in corners and entire frontwall is made death as per your recommandations.

If i sit in the backwall corners, i do not feel any bass pressure at all.


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## bpape

Just do the 2m x 1.4m in the middle.


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## Jason_Nolan

I tried a sub directly behind me as well and didn't like it. Everyone says you cannot localize under 80 Hz, but I can tell if a sub is directly behind me. Plotted well, sounded horrible.


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## bpape

turn the level down on the one behind you. Every meter closer you'll gain about 6db. You can also dial down the xover point on it to just be high enough to address the dip.


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## mikesp1

I agree, i can localise that sub behind me, even when i turn the volume much lower.
X over is on 80Hz for both subs, i will make a listen with the sub behind me on x-over 50Hz.

I tried with treadment on the backwall (blue curve), 1.5' of rockwool, 1.2m x 1.4m did maka things wurse!
All energy stays at front half of room, if i cross the midlle of the room there is not much pressure. This was before i made treatment and stays with treadment. it must be the type of room sloped ceilings on back and frontwall.

I do not know what to do anymore...

I think my best beth is to turn the volume on the front sub higher, so the 80hz dip is gone (yellow curve on graph) and then eq the peaks (maybe an antimode can do this?) from 50 to 70Hz and 20 to 40Hz.


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## mikesp1

Todat i did a quick test with rockwool stacked in backcorners, again no benefit.

blue curve: starting point upper ply removed, lower ply untouced
green curve: no rockwool, upper ply removed, lower ply reinforced
red curve: rockwool in corners

As you can see rockwool in corners gives no benefit


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## mikesp1

This curve was with lower ply totaly removed, it sounded much better in the low end, altough there are big dips on other frequencies.

Its getting verry frustrating after all the hard work getting no where.


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## mikesp1

Well, today i did some further testing.
I played only with the two Klipsch Palladiums without sub.

It was a relieve, bass was so punchy, articulate.

I then A B'd with and without subwoofer, i can only say Without was so much better!

I think the sub's i am using are no match for the quality of the Palladiums...

Here is a graph of spl 1/24 octaaf with only the fronts:

If i could,bring those peaks at 55 and 100 Hz within 10db that would be a good starting point to move further and start with the blending of the subs...


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## mikesp1

Waterfall


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## mikesp1

1/3 octaaf smoothing, only fronts


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## mikesp1

Further listening is telling me that without subs, the room definitly sounds pretty good, there is an occasional boom in the bassfrequency, probably the peaks at 55 and 100hz, it would be great if i could get rid of those, without further lowering the overall rt60 times above 200Hz


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## mikesp1

Bpape,

i did different test with trapping in midlle of backwall aswell as in backcorners. (see posts above)
it did nothing to the spikes in the 55hz and 100hz range but instead created a dip in 200hz to 300hz range.

Do i need more trapping on frontwall or do you think left and right to ceiling corners can help here?

thanks a lot!


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## mikesp1

Anybody?


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## hjones4841

Your frequency response plots with smoothing really look pretty good. 

I read through your posts quickly and could not tell if any of the absorption is thick enough to be effective as bass traps. Traps need to be 6" to 8" thick to be effective. I ended up with 5 of GIK's Monster Traps in my room plus R30 insulation above a suspended ceiling before I got the waterfall plots to look acceptable. But, as you have noted, my room does sound rather dead. But, it is 100% HT, so that works for me. Perhaps adding some dispersion panels would liven up the room for music.

I can identify with your concern about matching the subs to the sound of Klipsch. I have Klipschorns in my system and found that sealed subs, in my case Hsu ULS-15s, matched rather well. I still have the excellent transient response of the horn bass plus nice, tight LFE from the subs. I recently added Hsu MBMs to the system in sealed mode to add more "punch" to the system.

In summary, I think you have made good progress in treating your system. I agree with Bryan that the first few plots appeared to have the sub level up a little high.


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## mikesp1

hjones4841,

The room is definitly sounding verry well now. I am verry verry happy.

Currently i am still playing without subs but ordered two SI18's and will put them in sealed enclosures.
I will report later on if they blend with the rest of the system.

Bpape helped me a lot with this room and he was right on almost all things he suggested, so a big thanks to him!

I have learned that at a point it's time to listen to music and dont look too much at frequency graphs!


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## mikesp1

How do you like your Klipschorns?


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## mikesp1

Ok, in the past weeks i managed to build four SI18 sealed subwoofers.

I am wondering if someone can give me some advice regarding placement of the four subs regarding room modes.

room is 11.7 foot wide
20.8 foot long
7.6 foot high

Thanks a lot!


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## mikesp1

finished frontwall:


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## mikesp1

Installed fiber optic star ceiling:


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## mikesp1

Finishend room.

Only backwall stil needs to be treated.


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## bpape

Nice job! Very comfy and clean looking. 

Bryan


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## mikesp1

bpape said:


> Nice job! Very comfy and clean looking.
> 
> Bryan


Thanks a lot Bryan!


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## mikesp1

finished ht

1/48 smoothing
No equalising in use

crossover 70hw


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## mikesp1

Installed new basstrap on middle of frontwall, look at the dip between 60 to 100HZ.

Green curve is with basstrap.

Now i would like to take care of the large dip at 350 to 500Hz, any recommandations?


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## mikesp1

This weekend i time aligned THE Four SI18 subs, THE dip AT THE crossover point (70hz) is smoothed out and even THE dip AT 200hz is gone.
I still need to adres THE dip between 300 to 500hz.

Note: no equalizer being used.


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## Owen Bartley

The room looks great, Mike. And with all of the work you have put into the room treatments, I bet it sounds amazing. What else can you ask for!?  Great job. Enjoy it.


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## mikesp1

Thanks Owen!

Yes we audiophiles should more enjoy our music, rather than constantly searching for optimisation...


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