First up graphs, advice appreciated - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

Reply
 
Thread Tools
post #11 of 22 Old 02-07-09, 09:57 AM
Elite Shackster
brucek
 
Join Date: Apr 2006
Posts: 7,514
Re: First up graphs, advice appreciated

Quote:
how close to flat can one be realistically trying to achieve.?
The dip at 200Hz is quite bad. What's the problem?

Does a single speaker measured near-field in the middle of the room enjoy a flat response? Lets be sure that the room is the culprit.

brucek
brucek is offline  
Sponsored Links
Advertisement
 
post #12 of 22 Old 02-08-09, 11:52 PM Thread Starter
 
Join Date: Jan 2009
Posts: 24
Re: First up graphs, advice appreciated

I am sure the speakers are fine.
dodittydada is offline  
post #13 of 22 Old 02-09-09, 06:20 AM Thread Starter
 
Join Date: Jan 2009
Posts: 24
Re: First up graphs, advice appreciated

hmm, Im real suss on my chart. I mean, Im trapped to the * in here. Two front corner traps are a foot thick each, the ones behind the speakers 8 inches, rear traps are 6 inches thick....they are all 6ft tall and nearly reach to the ceiling. yet I still have a massive dip at 200hz in a rectangular room nearly 20ft deep??? I didnt expect flat of course, but this dosent seem right. I guess Im especially suss seeing its a dip and not a peak. Im sitting at the 38% point towards the front, I should be out of the way of any major modes.I just dont know what to do next besides start looking at slot resonators.
dodittydada is offline  
 
post #14 of 22 Old 02-09-09, 06:40 AM
Elite Shackster
Steven
 
Join Date: Jun 2007
Location: Midwest
Posts: 1,405
Re: First up graphs, advice appreciated

Quote:
dodittydada wrote: View Post
hmm, Im real suss on my chart. I mean, Im trapped to the * in here. Two front corner traps are a foot thick each, the ones behind the speakers 8 inches, rear traps are 6 inches thick....they are all 6ft tall and nearly reach to the ceiling. yet I still have a massive dip at 200hz in a rectangular room nearly 20ft deep??? I didnt expect flat of course, but this dosent seem right. I guess Im especially suss seeing its a dip and not a peak. Im sitting at the 38% point towards the front, I should be out of the way of any major modes.I just dont know what to do next besides start looking at slot resonators.
Have you tried some trapping on the ceiling between the LP and the mains before?
thewire is offline  
post #15 of 22 Old 02-09-09, 08:40 AM
Elite Shackster
HTS Moderator Emeritus
 
Anthony's Avatar
Anthony
 
Join Date: Oct 2006
Location: Virginia
Posts: 2,216
Re: First up graphs, advice appreciated

What are your exact room dimensions and relative speaker placement from wall/side/ceiling?

200 Hz 1/2 wavelength is about 5.5 ft. If you have an 11' dimension in the room and the speakers are right at this point, they'd be at a null.

Is there anything in the room that could be an accidental helmholtz or panel resonator? Sliding glass door, open doorway to another room. Dozens of empty water jugs in the corner? Originally my riser was acting as a panel resonator and sucking out a lot of bass until I added more insulation and doubled up on the plywood.

but that response is odd.
Anthony is offline  
post #16 of 22 Old 02-09-09, 10:26 AM
JohnM
Inactive
 
Posts: n/a
Re: First up graphs, advice appreciated

Try measuring forwards and backwards of your current position, 38% is not gospel, it is only a reasonable starting point to begin measuring to find the actual optimum for the room. Try moving the speakers also, as far as your space can accommodate. Easiest to use the RTA and the Pink PN generator when moving around, so you get immediate feedback of the effects.
post #17 of 22 Old 02-10-09, 02:07 AM Thread Starter
 
Join Date: Jan 2009
Posts: 24
Re: First up graphs, advice appreciated

Quote:
Anthony wrote: View Post
What are your exact room dimensions and relative speaker placement from wall/side/ceiling?

200 Hz 1/2 wavelength is about 5.5 ft. If you have an 11' dimension in the room and the speakers are right at this point, they'd be at a null.

Is there anything in the room that could be an accidental helmholtz or panel resonator? Sliding glass door, open doorway to another room. Dozens of empty water jugs in the corner? Originally my riser was acting as a panel resonator and sucking out a lot of bass until I added more insulation and doubled up on the plywood.

but that response is odd.

hmm, how about a fridge? Got one of those centre of the back wall. Could it possibly be sucking bass? with a closed door probably not. Width of the room MAY be around 11ft, not sure. Ill go measure it.
dodittydada is offline  
post #18 of 22 Old 02-10-09, 03:04 AM
Senior Shackster
Jim
 
Join Date: May 2006
Location: Wetumpka
Posts: 493
Re: First up graphs, advice appreciated

Have you calibrated your sound card and do you have any graphs of what the room was doing before adding any acoutic panels and bass traps.

I think another worthwild question is are we really sure that your amplifier speaker combination is not causing these dips?
JimP is offline  
post #19 of 22 Old 02-10-09, 03:53 AM Thread Starter
 
Join Date: Jan 2009
Posts: 24
Re: First up graphs, advice appreciated

Quote:
JimP wrote: View Post
Have you calibrated your sound card and do you have any graphs of what the room was doing before adding any acoutic panels and bass traps.

I think another worthwild question is are we really sure that your amplifier speaker combination is not causing these dips?

unofrtunately, no testing before treatment. What possible things amp/speaker wise could cause a dip like this? At least then I know where to start investigating. thanks.
dodittydada is offline  
post #20 of 22 Old 02-10-09, 07:14 AM
Senior Shackster
Jim
 
Join Date: May 2006
Location: Wetumpka
Posts: 493
Re: First up graphs, advice appreciated

I'm just saying that before you make yourself crazy fixing the room, be sure that you don't have something else going on with your electronics/sub/speakers. Unfortunately, if near field testing doesn't give you a flat response curve, then dragging it all outside to test it would be about the only other way to check it. How many feet of snow do you have?
JimP is offline  
Reply

Bookmarks

Tags
advice , appreciated , graphs

Quick Reply
Message:
Options

Register Now




PLEASE COMPLETE ALL REQUIRED FIELDS BELOW... THANKS!

REQUIRED FIELDS ON THIS PAGE
YOU MUST COMPLETE ALL OF THESE

Username
Password
Confirm Password
Email Address
Confirm Email Address
Random Question
Random Question #2




User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
PLEASE READ BELOW PRIOR TO ENTERING AN EMAIL ADDRESS!

ATTENTION!

YOU MUST ACTIVATE YOUR ACCOUNT!

Activation requires you reply to an email we will send you after you register... if you do not reply to this email, you will not be able to view certain areas of the forum or certain images... nor will you be able download software.

AN INVALID EMAIL ADDRESS WILL CAUSE YOUR ACCOUNT TO BE DELETED!

See our banned email list here: Banned Email List

We DO NOT respond to spamcop, boxtrapper and spamblocker emails... please add @hometheatershack DOT com to your whitelist prior to registering or you will get nowhere on your registration.


Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML is not allowed!
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 


For the best viewing experience please update your browser to Google Chrome