Lack of low-bass response because of a high ceiling

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Re: Lack of low-bass response because of a high ceiling

Postby Scott R. Foster » Wed Mar 31, 2010 11:01 am

I blame George Bush!
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Re: Lack of low-bass response because of a high ceiling

Postby Zaphod » Wed Mar 31, 2010 7:18 pm

Flav, did you listen for yourself? Do you agree with him?
I try never to get involved in my own life. Too much trouble. :mrgreen:
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Re: Lack of low-bass response because of a high ceiling

Postby ChrisAC » Fri Apr 02, 2010 12:46 am

Hello everibody,

I'm the person with the problem room.

First of all, THANKS FLAV for your help and 100% dedication. Meentime I'm a litle bitt confused, a whole ACOUSTIC FORUM and nobody has an experience with a 4m height room? Strange...
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Re: Lack of low-bass response because of a high ceiling

Postby Scott R. Foster » Fri Apr 02, 2010 2:33 am

37
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Re: Lack of low-bass response because of a high ceiling

Postby J.F.Oros » Fri Apr 02, 2010 9:06 am

Hi Chris and welcome to the forum!
You can find here a lot of knowledgeable and helpful guys and I'm sure you will learn interesting things while being around.
Hopefully, your problem will be solved soon too and you can then stick around here in a more relaxed way.

@Zaph : I did listen, of course. But only for a short time, when I was there to take the measurements. And i did perceive the lack of bass and some mid/high harshness, but I don't know the sound system so well and not even (most of) the music he was playing, so It was hard to me to get a good feeling of what is going on. And by no means i can compare my practical experience of listening high-end speakers to Chris, who is into this thing for many many years and he knows his tools and his favorite recordings much better than me.

@Scott : hey, stop messing with my friend's head. He already has a lot of numbers giving him nightmares now :mrgreen:
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Re: Lack of low-bass response because of a high ceiling

Postby ChrisAC » Fri Apr 02, 2010 10:00 am

A lot of thanks for your answers Scott ! Now it's all clear!
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Re: Lack of low-bass response because of a high ceiling

Postby bert stoltenborg » Fri Apr 02, 2010 3:09 pm

Chris,

did you already put those speakers as close to the back wall as possible and listen then?
A high ceiling is not a problem.
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Re: Lack of low-bass response because of a high ceiling

Postby Scott R. Foster » Fri Apr 02, 2010 6:56 pm

Welcome Chris:

There aint nothing evil about 4 meters - the world is full of decent sounding rectilinear rooms with an axial dimension of this magnitude.

There may be something seriously wrong with the room's spectrum of modal excitation and decay - or perhaps the way the speakers are setup has created some sort of weird SBIR problem or maybe you have got them in a profound LF null. or perhaps you have a resonate structure in the room. Sometimes problems hide very well.

I once had a absurd problem with a system null in the low mids. There was no sound at this frequency band - until after the note was gone... then this band would reverberate for several seconds. I was mystified until I realized we had 3" conduits in the floor with the ends left open. They were working like inverse organ pipes - suck the sound in - then blow it back at the room. Stupid mistake - took me a week to it figure out - 5 seconds to fix. I suspect you have a problem of this sort. Something simple is wrong - and hiding. Go around the room while a test tone is playing the problem frequency band and lay your hands and ears on things high and low. Listen and look for an anomaly while you repeat under you breath, "There is nothing inherently unworkable with a 4m ceiling!"

My $0.02
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Re: Lack of low-bass response because of a high ceiling

Postby bert stoltenborg » Fri Apr 02, 2010 7:07 pm

Flav,

After adjusting ARTA I looked at those measurements again.
They don't seem so weird to me; maybe post 'm and have the guys here look at 'm?
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Re: Lack of low-bass response because of a high ceiling

Postby J.F.Oros » Fri Apr 02, 2010 8:44 pm

First, thank you guys for keeping your interest into this. It really helps us (me and Chris) and I hope others too will learn valuable things from our experience.

The thing that's so frustrating is that the problems (what Chris described in the quote i posted a few messages ago) keep appearing in 3 rooms of that house, not just one, even when we move the speakers or the mics in the rooms. So it might be indeed something that's not obvious in the measurement diagrams. OK, we have those LF peak/dips, but the lack of bass is not the only problem Chris accuses. And as Bert noticed, they don't look so bad afterall.

But all of those 3 rooms have at least one thing in common, the 4m ceiling, while a 4th room Chris tested in the same house, which sounds much better according to him, has only a 3m high ceiling. That's why all of this 4m ceiling "paranoia" ...

Chris even considers the possibility that the mineral wool I recommended him (Isover PLU, 40kg/m3 basaltic boards) its not working properly and makes things worse in the room, so he decided to use a more fluffy type (roll type not boards) for the treatments.

Anyway, here are the frequency responses for two speaker positions in the main room.
For every spot there 3 diagrams, a full audio range (1/3 oct smoothed), a low frequency range (1/3 oct smoothed) and a non-smoothed low frequency range.
I also attached the room impulse wav files, if any of you has the curiosity to analyze them more indepth.

Room dimensions are : 4.1m x 4.85m x 6m.
For Room1-M03 diagrams we have : speaker to front wall = 1.45m , spk. distance to left wall = 1.3m , mic distance to rear wall = 2m , mic distance to side walls = aprox 2.4m (middle) , mic height = 1.05cm
For Room1-M29 diagrams we have : speaker to front wall = 1.9m , spk. distance to left wall = 1.25m , mic distance to rear wall = 2m , mic distance to side walls = aprox 2.4m (middle) , mic height = 1.05cm
Attachments
Room1-M03_FR-All-SM.png
(20.37 KiB) Not downloaded yet
Room1-M03_FR-LF.png
(20.71 KiB) Not downloaded yet
Room1-M03_FR-LF-SM.png
(19.07 KiB) Not downloaded yet
Room1-M29_FR-All-SM.png
(20.25 KiB) Not downloaded yet
Room1-M29_FR-LF.png
(20.61 KiB) Not downloaded yet
Room1-M29_FR-LF-SM.png
(18.84 KiB) Not downloaded yet
Room1-M03.wav
(128.75 KiB) Downloaded 216 times
Room1-M29.wav
(128.75 KiB) Downloaded 217 times
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Re: Lack of low-bass response because of a high ceiling

Postby ChrisAC » Sat Apr 03, 2010 12:03 am

Hi guys,

Thank you very much for your answers and kindnes! It realy help us in our investigation, I feel like you, it has to be something simple but we can't find. The most frustrating is the fact we have a simple form room , nothing unregular but the behaviour is realy unprevisible. I made some tretments in the past, in our show-rooms, at customers ( with knoledges got from Flav - thank you again ) and all were succesfull , very simple hearable their benefic efects. It's true, they all were made in smaller rooms and no one was over 3, 3.5 m height. In this room(s), strange, but looks like no ( major) diference between the completly untrated ore masive treatment aplied. It looks like a powerfull fingerprint superimposes it's personality ( described by me) over any acoustical treatment. This efect is more pregnant is the bigger room ( 4/5/6 let's say nr1 ) than in the smaller ( 4/4,7/5,3 - nr2 ), but there is present too in the last one. There is too a third room, but the results are not concludent due to it's regips ceiling .

The only one diference is the fact that the room nr2 has an aprox. 2/2m hole in the midle of the ceiling wich comunicates with the garret ( but closed with wool and regips ) and I'm not sure about the crossbeams if they have the same structure. I ask myself if a few metalical crossbeams ( like rails ) could have such an effect? In the 3m room, except the dimensions, the only structural diference is th crossbeams, wich are all made by wood.

Other posibility I could think is the treatment materials to do not work ....
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Re: Lack of low-bass response because of a high ceiling

Postby Ido » Tue Sep 07, 2010 11:43 am

howdy Flav,
been catching up (evading work is more like it),
do you have any final conclusion-insight into this? why?
I have a thought that longs rooms don't like bass, also to be influenced by ratios,
but it's just a thought.
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