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Author Topic: Youth Room SM80F & Acoustic Treatment - Previously: It depends always the answer  (Read 5717 times)

Nathan Riddle

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Working on a design, had some thoughts I couldn't quite shake.


Some Background:
The client has two K12's (75* pattern) & 2x KW181. Subs L/R of (stage width = 30.3ft) with K12's being ~12ft high.


Issues with the room being extremely reverberant and muddy and generally sounding bad.
Asked me to look into it for them. I thought Danley is probably best bet given the pattern control.


-Music is for students and newer contemporary thus lots of bass (Hillsong Young and Free) etc.
-dBA = 97 slow (110ish? C/fast)
-Room (LxWxH) (72.4ft x 47.7ft x 21ft)


My gut feeling was the SH50 center next to ceiling.. But I wanted to model it first. Once I modeled the room it confirmed my suspicion that the SH50* was the best speaker for the mains. Though I am open to an expert's opinion on the matter.


*The SH46 also looks like a good bet or the new SM80F.


Additionally, I also wanted to give the option of replacing their two KW181 subs. Not that a matched system is necessary, but that the sound quality would improve and they can re-purpose the existing system elsewhere.


I own the TH118, so I have a good idea of what it can do. The stage height is 20" so I had to find a sub under that height.


I found the following might work:
-BC412
-TH212
-TH112
-TH Mini
-TH Mini15


After consulting the spec sheets I found the TH212 to be the best fit.
I'd love for the BC412, but it is probably out of the price range and overkill for the room.


The TH212 seems like a good fit. But while modeling when I compared to a TH118 for kicks and giggles the TH118 came out lower in volume ~weird?


While playing with delay times between the sub/main I found I could cancel in the 100-160Hz range along the back wall without much issue on the floor.
Thoughts if that would help?
http://www.sengpielaudio.com/calculator-roommodes.htm


Issues:
-TH212 has more output than TH118 (mismatch with spec-sheet), what?
-Thoughts on TH212 vs 2x KW181?
-SH50 seems to need a much lower angle than I expected, but models well. Go with 36*?
-Thoughts on using a DFA under the SH50 for the front row? (I'm inclined to think it's not needed).
-Delaying main/sub for cancellation in the 100/125/160Hz range along back wall to help control room modes?
-Anything else I'm missing?


Linky to files:
https://www.dropbox.com/sh/xsmiwp8zd0b3z5y/AADylV_U0hdIbdtSDZfF9bu7a?dl=0


SH50 @ 18' with 36* tilt
TH212 @1' End mode
xOver 70Hz LR 24 Global


Mics @
6ft (blue)
36ft (red)
69ft (green)
-3ft (black)

« Last Edit: February 07, 2018, 10:28:57 am by Nathan Riddle »
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Cailen Waddell

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Re: "It depends" is always the answer.
« Reply #1 on: April 08, 2017, 11:20:53 pm »

Good speakers don't fix a bad room.  Is there a reason for an upgrade besides the sound of the room?  An acoustician and some well places treatment isn't sexy but might be a better use of funds?


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Nathan Riddle

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Re: "It depends" is always the answer.
« Reply #2 on: April 08, 2017, 11:53:05 pm »

Good speakers don't fix a bad room.


Is there a reason for an upgrade besides the sound of the room?


An acoustician and some well places treatment isn't sexy but might be a better use of funds?


Good points that I forgot to address.


Another is pics. I've been in the room enough times to where I can easily visualize things, but I should have taken some for the forum's benefit.


---


The venue has already had acoustic treatment (It's the thin stuff so it is only really helping in the 1kHz+ range.) And an acoustician has been through the venue. He thinks the room is just fine as it is very 'lively' I don't agree with this design goal and after a year or so, neither does the client.

It came up in conversation and I said I bet I could fix that with a single point source Danley solution. And now here we are.

I'm not sure about this as it is just a thought but limp mass bass traps tuned to the eigen frequencies would help the standing waves. The problem would be by how much, would the improvement justify the cost? THIS* is uncharted territory for me. I just know it works for smaller studios.

---


Sound quality improvement over current speakers is one goal, but that could be accomplished cheaper via upgraded speakers (SRX8xx) variety (as my mains (SRX835p) at their events have proven themselves to the client).


One factor of the room's 'bad' sound is the 75* angle on the K12's that gets all over the walls and back of the room instead of on the audience adding to reverberation. This is proved via modeling (see attached photo).



Quote
Good speakers don't necessarily fix a bad room.
Fixed it for ya  ;) 


Would it not be correct to say that properly aimed, deployed, and pattern control can help increase objectively quantifiable sound quality results (SPL variance, reflection lessening, intelligibility, etc) in a room.
Additionally, higher quality speakers would increase sound quality even if the reflection and standing wave issues remain the same.
Lastly, LESS speakers would help freq response and phase issues when moving about in the room thus improving intelligibility.
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Jean-Pierre Coetzee

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Re: "It depends" is always the answer.
« Reply #3 on: April 09, 2017, 05:41:57 am »

If the room is muddy and boomy then it was not treated correctly.

You need full bandwidth treatment, simply slapping fiberglass or something similar on or spaced away from the walls will still not be effective down low, neither will a different speaker since they physically cannot be direction down low.

I think your problems are with room modes and no speaker upgrade will fix it.

If there isn't fiberglass at least 4" thick used as treatment it will 100% be the cause of the muddiness since you will still be getting reverberation at low mid frequencies but the higher frequencies are attenuated by the treatment. It your problem is below 120Hz or so you need proper bass traps place at the junction of two surfaces or even better at the junction of 3 surfaces. Also the fiberglass will absorb lower if you move it 2-4" from the wall but more that 2-4" is probably wasting your time since you should be using a bass trap.

Do your predictions at 500Hz with reflective surfaces and you will notice the problem.

EDIT: Linky There are some absorption coefficients to backup the acoustic treatment.
« Last Edit: April 09, 2017, 05:45:02 am by Jean-Pierre Coetzee »
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Nathan Riddle

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Re: "It depends" is always the answer.
« Reply #4 on: April 09, 2017, 02:55:24 pm »

If the room is muddy and boomy then it was not treated correctly.

You need full bandwidth treatment, simply slapping fiberglass or something similar on or spaced away from the walls will still not be effective down low, neither will a different speaker since they physically cannot be direction down low.

I think your problems are with room modes and no speaker upgrade will fix it.

If there isn't fiberglass at least 4" thick used as treatment it will 100% be the cause of the muddiness since you will still be getting reverberation at low mid frequencies but the higher frequencies are attenuated by the treatment. It your problem is below 120Hz or so you need proper bass traps place at the junction of two surfaces or even better at the junction of 3 surfaces. Also the fiberglass will absorb lower if you move it 2-4" from the wall but more that 2-4" is probably wasting your time since you should be using a bass trap.

Do your predictions at 500Hz with reflective surfaces and you will notice the problem.

EDIT: Linky There are some absorption coefficients to backup the acoustic treatment.


Thanks,


That's basically what I thought and said originally when they were considering treating the room. But i'm not an acoustician, and the acoustician said that bass traps and absorption was a fad and wasn't really beneficial and so they didn't put any up.  :-\


The muddy/boomy issues are one aspect. The absurdly long total reverb time (seriously sounds like a giant hall and the snare is louder in the room than on stage [fixed via drum cage]) is also an issue.


Getting the HF off of the walls will help the HF issues, but you're right it won't help the LF issues.


I was considering suggesting additional treatment for the midbass frequencies, but I wasn't sure if that would be a good idea.


Anyone have good suggestions for manufactures for acoustic treatments (specifically, midbass = 100hz-500hz range)?


Actually, never mind I should practice what I preach and search for it myself.
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Jean-Pierre Coetzee

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Re: "It depends" is always the answer.
« Reply #5 on: April 09, 2017, 05:37:08 pm »

Resonant absorbers are really not hard to manufacture and there are plenty resources out there that will tell you exactly how to do it. If this is a HOW which is what I'm picking up between the lines that I'd something that could possibly handles by a handyman as long as you do the research and make sure they apply it correctly, getting paid of course.

If your a consultant take their situation in mind.

EDIT: To start reading
« Last Edit: April 09, 2017, 05:42:46 pm by Jean-Pierre Coetzee »
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Jean-Pierre Coetzee

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Re: "It depends" is always the answer.
« Reply #6 on: April 09, 2017, 06:29:20 pm »

Some maths from a textbook

FR =(approx)= 60/(SQRT(M' * DL))

Where FR is the resonant frequency(resonant panels act as a "peaking" type eq so this is the center)

M' = Area related mass of the resonant material in kg/m2

DL =  Distance between the resonant material and the back wall(the depth of the panel) in m

Area related mass is calculated by area/mass or density * thickness

You can decrease the Q of the panel by filling it with porous material(such as rockwool/fiberglass) and you can mount fiberglass to the resonant panel to create a broadband absorber(as is shown in the article from the last post I made).

It's recommended that the resonant panel not be smaller that 0.4 m2

You generally want 5 solid very dense pieces and one less dense piece that is just slotted in with a dado joint so that is is able to resonate.
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Ivan Beaver

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Re: "It depends" is always the answer.
« Reply #7 on: April 10, 2017, 12:48:30 pm »

Why not put a single SM80F in the middle-turned on its side?

It would have much greater output and be less expensive than a SH50 + subs.

You would not need subs with the SM80F.

You would have more even sub coverage across the room.

The alignment between mains and sub would be perfect-because they are in the same box.
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Nathan Riddle

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Re: "It depends" is always the answer.
« Reply #8 on: April 10, 2017, 04:53:48 pm »

Resonant absorbers are really not hard to manufacture and there are plenty resources out there that will tell you exactly how to do it. If this is a HOW which is what I'm picking up between the lines that I'd something that could possibly handles by a handyman as long as you do the research and make sure they apply it correctly, getting paid of course.

If your a consultant take their situation in mind.

EDIT: To start reading

Some maths from a textbook

FR =(approx)= 60/(SQRT(M' * DL))

Where FR is the resonant frequency(resonant panels act as a "peaking" type eq so this is the center)

M' = Area related mass of the resonant material in kg/m2

DL =  Distance between the resonant material and the back wall(the depth of the panel) in m

Area related mass is calculated by area/mass or density * thickness

You can decrease the Q of the panel by filling it with porous material(such as rockwool/fiberglass) and you can mount fiberglass to the resonant panel to create a broadband absorber(as is shown in the article from the last post I made).

It's recommended that the resonant panel not be smaller that 0.4 m2

You generally want 5 solid very dense pieces and one less dense piece that is just slotted in with a dado joint so that is is able to resonate.

Thank you,
I believe I have a fair amount of research to do.
I'll report back once I've gotten a bit further.

Why not put a single SM80F in the middle-turned on its side?

It would have much greater output and be less expensive than a SH50 + subs.

You would not need subs with the SM80F.

You would have more even sub coverage across the room.

The alignment between mains and sub would be perfect-because they are in the same box.

I considered this. The price savings would be really good.

I wanted to model it in Direct, but it hasn't made it into the software yet. I could probably stick a TH118 and SM80 in the air in the same place and that would work/model well.

My main concern with that is the 80* coverage vs the 50* coverage (the intent being to get the HF off of the walls).

Secondly, I wouldn't mind widening the freq response range from the 50hz of the KW181 to 35-40hz. But that's probably unnecessary. It would be nice because its mainly a youth room so the LF would be good.

Third, while I'm sure the SM80 sounds good, it probably doesn't sound as 'good' as the 'flagship' SH50. Am-I-right? I think it's time I spend a weekend and drive up to Atlanta and take a full line-up listen.

The alignment is nice, but I was curious if the cancellation might be helpful (just a thought by a curious mind).

Lastly, it would be nice to prove to their AV guy that flown subs work just as well as ground subs. (We had a nice discussion about how subs on the floor 'hit harder' than flown subs...)

As far as it being a 'new' product, what kind of long term testing has it been put through? The HOW client has a history of 'early adoption's' in the tech world and has been burnt many times by it (QSC's PLD amp's low pass filter stage causing oscillations, streaming services with bugs, etc) [not my fault].
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Jean-Pierre Coetzee

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Re: "It depends" is always the answer.
« Reply #9 on: April 10, 2017, 07:14:07 pm »

Thank you,
I believe I have a fair amount of research to do.
I'll report back once I've gotten a bit further.

I considered this. The price savings would be really good.

I wanted to model it in Direct, but it hasn't made it into the software yet. I could probably stick a TH118 and SM80 in the air in the same place and that would work/model well.

My main concern with that is the 80* coverage vs the 50* coverage (the intent being to get the HF off of the walls).

Secondly, I wouldn't mind widening the freq response range from the 50hz of the KW181 to 35-40hz. But that's probably unnecessary. It would be nice because its mainly a youth room so the LF would be good.

Third, while I'm sure the SM80 sounds good, it probably doesn't sound as 'good' as the 'flagship' SH50. Am-I-right? I think it's time I spend a weekend and drive up to Atlanta and take a full line-up listen.

The alignment is nice, but I was curious if the cancellation might be helpful (just a thought by a curious mind).

Lastly, it would be nice to prove to their AV guy that flown subs work just as well as ground subs. (We had a nice discussion about how subs on the floor 'hit harder' than flown subs...)

As far as it being a 'new' product, what kind of long term testing has it been put through? The HOW client has a history of 'early adoption's' in the tech world and has been burnt many times by it (QSC's PLD amp's low pass filter stage causing oscillations, streaming services with bugs, etc) [not my fault].

Remember that ground stack sub's are half spaced so theoretically they have 3dB more power then flown subs(you need double the amount of flown sub's to get the same 'punch'), there are distinct advantages to flown sub's though that cannot be ignored in many rooms.
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"If you want "loud", then run a piece of sheet metal through a table saw------

If you want "watts"-then plug in a toaster"
- Ivan Beaver
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