Loopback/timing refence question - Home Theater Forum and Systems - HomeTheaterShack.com

 
Thread Tools
post #1 of 5 Old 05-01-17, 08:16 AM Thread Starter
Shackster
bomholt
 
Join Date: Jun 2007
Location: Bergen, Norway
Posts: 88
Loopback/timing refence question

I'm trying to figure out whether there's something wrong with my connection/set up or if my DSP isn't adding delay correctly now.

I've a Sound Devices USBpre 2 sound card that has internal loopback function.

Connection is the following:
- Right channel output to DSP
- Left input to mic
- Internal loopback from left output to right input

My settings in REW are like the following:


Looking at the ETC and impulse, it looks like the timing reference works:




But there two matters:

1. Delay in DSP doesn't change anything. Might be a problem with the DSP though. After all, I'm seeing difference in delay between drivers in speakers. So can I conclude from that the DSP must be the problem?

2. If I remove the internal loopback I get a message that the level is too low, but the timing/arrival is still the same. How can that be?
Attached Thumbnails
Loopback/timing refence question-screen-shot-05-01-17-03.08-pm.png  

Loopback/timing refence question-loopback-etc.jpg  

Loopback/timing refence question-impulse.jpg  

omholt is offline  
Sponsored Links
Advertisement
 
post #2 of 5 Old 05-01-17, 04:22 PM
REW Author
 
JohnM's Avatar
John
 
Join Date: Apr 2006
Location: UK
Posts: 6,566
Re: Loopback/timing refence question

Your timing reference output is selected as the right output (2) though, shouldn't it be the left (1)? Crosstalk might be enough to keep it working without the loopback connection.
JohnM is offline  
post #3 of 5 Old 05-02-17, 01:20 AM Thread Starter
Shackster
bomholt
 
Join Date: Jun 2007
Location: Bergen, Norway
Posts: 88
Re: Loopback/timing refence question

Quote:
JohnM wrote: View Post
Your timing reference output is selected as the right output (2) though, shouldn't it be the left (1)? Crosstalk might be enough to keep it working without the loopback connection.
The picture was wrong. I've been trying different setups and forgot to set it correctly when taking the print screen. Sorry.
Attached the correct one which was used in the previous showed measurements.

Can you elaborate on what you mean by crosstalk being able to make it work without loopback connection?

Here's from the manual concerning the internal loopback function:

Quote:
Input 2 Loop Source
Input 2 has an additional source labeled LOOP. This input source does not correspond to any physical
connections on the USBPre 2. When LOOP is selected, input 2ís source is derived from the left
channel of the computer audio signal (post digital-to-analog conversion). The input 2 Gain Control
affects signal The Output Gain Control does not affect the level of the signal going in to input 2.
The LOOP source is useful for test and measurement applications where a reference signal is required
to be routed back to an input.
Attached Thumbnails
Loopback/timing refence question-screen-shot-05-02-17-08.12-am.png  

omholt is offline  
 
post #4 of 5 Old 05-02-17, 12:44 PM
REW Author
 
JohnM's Avatar
John
 
Join Date: Apr 2006
Location: UK
Posts: 6,566
Re: Loopback/timing refence question

Even if you haven't selected the loop connection there will be some internal crosstalk between the channels of the soundcard, that might be enough for the loopback code to detect a reference signal.
JohnM is offline  
post #5 of 5 Old 05-02-17, 02:48 PM Thread Starter
Shackster
bomholt
 
Join Date: Jun 2007
Location: Bergen, Norway
Posts: 88
Re: Loopback/timing refence question

Thanks John.

Seems like the issue here is the DSP, which isn't responding to delay right now. I'll experiment some more.
omholt is offline  
Reply

Bookmarks

Tags
loopback or timing , question , refence

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









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



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