Home Theater Forum and Systems - HomeTheaterShack.com - Reply to Topic

Thread: Comments on my first measurements? Reply to Thread
Title:
Message:
Post Icons
You may choose an icon for your message from the following list:
 

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










  Additional Options
Miscellaneous Options

  Topic Review (Newest First)
07-20-09 04:45 PM
1972nosay
Re: Comments on my first measurements?

I think ,all is too difficult to undestand!I need to study the software and I'll make my first test.
07-12-09 05:09 PM
brucek
Re: Comments on my first measurements?

Quote:
major dip at around 150Hz from my right front speaker. It seems to even out when both speakers are on. Is this kind of thing to be expected?
Of course. You can add the red and gold line together yourself and end up withe result of the blue....

Quote:
The green line in graph 2 shows my seats moved forward about 12" and my front speakers moved about 24" closer to the front wall. Better?
No, it's worse.

Quote:
Is there any method to narrowing in on the seemingly infinite number of combinations of these three factors?
Fourth factor. Adjust your subs phase control, since 71Hz is at your crossover area.

Quote:
Graph 3 shows a reading from 200Hz to 2,000Hz. This is clearly way choppier. Is this normal?
It's called comb filtering. Normal. Turn on the smoothing feature to reveal the underlying trend.

Quote:
How does the waterfall graph look? Are my bass traps paying off?
Compared to what?

brucek
07-12-09 04:08 PM
Wayne A. Pflughaupt
Re: Comments on my first measurements?

Quote:
1. The first graph below shows a major dip at around 150Hz from my right front speaker. It seems to even out when both speakers are on. Is this kind of thing to be expected?
It happens, especially in asymmetrical rooms.

Quote:
2. I also played around with moving my seats and front speakers. The green line in graph 2 shows my seats moved forward about 12" and my front speakers moved about 24" closer to the front wall. Better?
Not really – levels below 30 Hz are significantly reduced.

Quote:
3. All of my readings thus far were taken with my sub set at 28Hz/Low Damping. The purple line in graph 2 shows my sub setting changed to 20Hz/Low Damping. Looking better?
If you mean “better than graph 1,” the answer is yes.

Quote:
4. Is there something that I can do to address those dips at 71Hz and 172Hz? Should I just keep trying different speaker/seating/sub locactions? Is there any method to narrowing in on the seemingly infinte number of combinations of these three factors?
The only problem is 71 Hz. The rest of it is perfectly normal.

Quote:
5. Graph 3 shows a reading from 200Hz to 2,000Hz. This is clearly way choppier. Is this normal?
Yes.

Quote:
6. How does the waterfall graph look? Are my bass traps paying off?
Looks good, but we’d have to see a “before” waterfall to say for sure.

Regards,
Wayne
07-12-09 03:22 PM
elee532
Re: Comments on my first measurements?

I did some tweaking today using the ThinkPad for my readings. Not surprisingly, I now have more questions. :-)

1. The first graph below shows a major dip at around 150Hz from my right front speaker. It seems to even out when both speakers are on. Is this kind of thing to be expected?

Blue = Sub + Both mains
Gold = Sub + RF
Red = Sub + LF
Green = Sub only

2. I also played around with moving my seats and front speakers. The green line in graph 2 shows my seats moved forward about 12" and my front speakers moved about 24" closer to the front wall. Better?

3. All of my readings thus far were taken with my sub set at 28Hz/Low Damping. The purple line in graph 2 shows my sub setting changed to 20Hz/Low Damping. Looking better?

4. Is there something that I can do to address those dips at 71Hz and 172Hz? Should I just keep trying different speaker/seating/sub locactions? Is there any method to narrowing in on the seemingly infinte number of combinations of these three factors?

5. Graph 3 shows a reading from 200Hz to 2,000Hz. This is clearly way choppier. Is this normal?

6. How does the waterfall graph look? Are my bass traps paying off?

Thanks!!
07-04-09 01:32 PM
brucek
Re: Comments on my first measurements?

Quote:
Any thoughts on why this might be the case?
It does look like the computer is the source of the problem. I made the suggestion to check that because before I got my fancy new laptop, I use to have a second computer that I would use for REW, and it was certainly challenged by REW and would always stumble at the start of a sweep and I would have to try quite a few times before it didn't hitch at the beginning.

I'm surprised that the computer giving you the problem is the faster one of the two you've tried, but who knows what other resources you have tying up the bus besides running REW.

Anyway, looks like you should use the thinkpad for your testing from now on....

brucek
07-04-09 01:22 PM
elee532
Re: Comments on my first measurements?

I gave this a try on another computer... 0 to 200Hz sweep using 128, 256k, 512k, and 1M sweep lengths (graph 1, seperated traces is turned on). Graph 2 shows 0 to 20,000Hz sweeps at 128k and 1M.

Computer 1 is my HTPC... 2.5ghz dual core, Gigabyte GA-E7AUM-DS2H motherboard using the onboard Realtek Digitial Input and Output.

Computer 2 is a Lenovo ThinkPad X61T, Core2Duo 1.6Ghz, using USB Soundblaster X-Fi.

As you recall, my initial question surfaced when my results from a 0 to 200Hz sweep were different from the results from a 0 to 20,000Hz sweep between 0 and 20Hz (graph 1 below for reference).

Anyway, comparing these with the earlier readings, it looks the computer was the source of the difference and not the sub or pre-pro. Is my understanding correct? (I suppose if I was really motivated, I'd connect the X-Fi to Computer 1... just don't have the time or energy right now.). Any thoughts on why this might be the case?

Thanks!


07-03-09 06:10 PM
elee532
Re: Comments on my first measurements?

Quote:
brucek wrote: View Post
It looks like you did everything correctly, although I am a bit confused by the statement:I ran Calibrate and set my pre-pro until I got a reading of about 75db.

Generally, you first run the Check Levels routine (during which time the pre-pro volume is adjusted to get a reading of 75dBSPL on the RadioShack meter).
Yeah, I meant to say Check Levels not Calibrate.

I do have a second computer that I can give this a try with. Will try to do so over the weekend.

Thanks!
07-03-09 09:03 AM
brucek
Re: Comments on my first measurements?

Quote:
Were my nearfield readings done correctly? Do they offer any insight?
It looks like you did everything correctly, although I am a bit confused by the statement:I ran Calibrate and set my pre-pro until I got a reading of about 75db.

Generally, you first run the Check Levels routine (during which time the pre-pro volume is adjusted to get a reading of 75dBSPL on the RadioShack meter).

Then the Calibrate routine is run to match the REW SPL meter to the 75dB reading of the Radio Shack meter.

Anyway, there's no way to establish what's wrong without substituting one of the possibilities. You have to substitute either the measuring computer or the subwoofer.

brucek
07-03-09 08:42 AM
elee532
Re: Comments on my first measurements?

Quote:
brucek wrote: View Post
Yes....
Thanks. Were my nearfield readings done correctly? Do they offer any insight?
07-03-09 07:11 AM
brucek
Re: Comments on my first measurements?

Quote:
I've been setting my SPL meter for C Weighting, Slow Response. Is this correct?
Yes....
This thread has more than 10 replies. Click here to review the whole thread.

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!

 


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