SVS vs. Outlaw ? - Page 3 - AVS Forum
Forum Jump: 
Reply
 
Thread Tools
post #61 of 64 Old 07-18-2012, 05:09 PM
Advanced Member
 
jchong's Avatar
 
Join Date: Apr 2008
Posts: 864
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 32
Quote:
Originally Posted by its phillip View Post

Thanks to jchong/mktheater/ricci for the clarification smile.gif - that does mean that the SVS is NOT outputting 105dB at 16hz like it sounded mk was saying though.

Indeed the SVS is not outputting 105dB @ 16Hz. MK was referring to how the SVS completes the 105dB sweep test and in relation to THD, how clean it is from 16Hz up at the 105dB sweep level. Actual output @ 16Hz looks like 85dB @ 8% THD.

For the Outlaw in 2-port mode, actual output @ 16Hz is 79dB @ 26% THD. The 1-port mode gets much better output, 16Hz is 93dB @ 15% THD.
jchong is offline  
Sponsored Links
Advertisement
 
post #62 of 64 Old 07-18-2012, 05:15 PM
Senior Member
 
ironhead1230's Avatar
 
Join Date: Jan 2006
Location: Laurel, MD
Posts: 429
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 46
Quote:
Originally Posted by jchong View Post

Thanks for chiming in Ricci and giving a bit more details about the test.
How does this long term output compression test differ from the CEA test? I notice it is called "long term" vs the CEA test which is described as "burst".

Short answer, the compression test is a much longer duration signal and is more demanding on the sub. It takes more continuous power from the amp and puts a higher thermal load on the amp and driver. The CEA test is a short burst test. To pass, each harmonic has to be below a certain level. The CEA value will almost always be higher than the sweep level. From Ricci's site, data-bass.com:

http://www.data-bass.com/know-how

"Power compression sweeps are taken using a 24sec long sine wave sweep covering the range of 10-100hz starting at the base 90db at 50hz level. The level is increased by 5db for each subsequent sweep until the sub exhibits clear distress, the the amplifier exhibits clipping, or the output stops increasing notably. In some cases a final sweep of 2 or 3db higher level was tried as a jump of a full 5db at the extreme ends of performance is often far too much for the systems to handle. 2 types of graphs are generated from this test set. The basic overlay of each sweep which will show how the response changes with each increase in level and another graph which shows only the amount of compression that is occuring in the systems output. Ideally what you are looking for is the least amount of compression throughout the entire bandwidth at the highest sweep levels."

"CEA2010 maximum short term clean output. Maximum RMS short term output is measured at 2m ground plane. This test involved short 6.5cycle duration shaped sine bursts centered at 1/3rd octave intervals of 20, 25, 31.5, 40, 50 and 63hz. Additionally I added further test frequencies at both ends of the spectrum (10, 12.5, 16, 80, 100 and 120hz) to better represent more of the full bass bandwidth as long as the systems were capable of reproducing meaningful output in those bands. The DUT's output level is then increased while the distortion is monitored until either the DUT stops gaining in output level or the prescribed stair step distortion threshold for any harmonic is exceeded. (Disclaimer note: October 2010 1st round tests were not CEA2010 compliant. They were meant to be CEA2010 compliant but we did not have access to the software package to perform them at the time the 1st round tests were conducted in October 2010. The tests had to be approximated in a manual fashion which was very tedious. Since that is the case the data should not be compared to actual CEA2010 tests directly.)"

-Mike
ironhead1230 is offline  
post #63 of 64 Old 07-18-2012, 11:18 PM
Advanced Member
 
jchong's Avatar
 
Join Date: Apr 2008
Posts: 864
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 32
Thanks for that Mike.
jchong is offline  
post #64 of 64 Old 07-19-2012, 06:00 AM
AVS Special Member
 
Ricci's Avatar
 
Join Date: Mar 2007
Location: Louisville KY
Posts: 5,101
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 16 Post(s)
Liked: 219
Quote:
Originally Posted by ironhead1230 View Post

Short answer, the compression test is a much longer duration signal and is more demanding on the sub. It takes more continuous power from the amp and puts a higher thermal load on the amp and driver. The CEA test is a short burst test. To pass, each harmonic has to be below a certain level. The CEA value will almost always be higher than the sweep level. From Ricci's site, data-bass.com:
http://www.data-bass.com/know-how

"Power compression sweeps are taken using a 24sec long sine wave sweep covering the range of 10-120hz starting at the base 90db at 50hz level. The level is increased by 5db for each subsequent sweep until the sub exhibits clear distress, the the amplifier exhibits clipping, or the output stops increasing notably. In some cases a final sweep of 2 or 3db higher level was tried as a jump of a full 5db at the extreme ends of performance is often far too much for the systems to handle. 2 types of graphs are generated from this test set. The basic overlay of each sweep which will show how the response changes with each increase in level and another graph which shows only the amount of compression that is occuring in the systems output. Ideally what you are looking for is the least amount of compression throughout the entire bandwidth at the highest sweep levels."
"CEA2010 maximum short term clean output. Maximum RMS short term output is measured at 2m ground plane. This test involved short 6.5cycle duration shaped sine bursts centered at 1/3rd octave intervals of 20, 25, 31.5, 40, 50 and 63hz. Additionally I added further test frequencies at both ends of the spectrum (10, 12.5, 16, 80, 100 and 125hz) to better represent more of the full bass bandwidth as long as the systems were capable of reproducing meaningful output in those bands. The DUT's output level is then increased while the distortion is monitored until either the DUT stops gaining in output level or the prescribed stair step distortion threshold for any harmonic is exceeded. (Disclaimer note: October 2010 1st round tests were not CEA2010 compliant. They were meant to be CEA2010 compliant but we did not have access to the software package to perform them at the time the 1st round tests were conducted in October 2010. The tests had to be approximated in a manual fashion which was very tedious. Since that is the case the data should not be compared to actual CEA2010 tests directly.)"
-Mike

Gah! I still need to update a lot of things as I keep tweaking the tests and equipment. I bolded a couple of minor corrections above.

Mike thanks for posting that.

The CEA2010 test has prescribed distortion thresholds for each harmonic and for noise. It is a short term, shaped, bandwidth limited, burst for assessing realistic headroom levels available from a system for dynamic peaks. The sine sweep is continuous and loads the system heavily while sweeping the full frequency range. It is not a real world signal that would be seen but it is a sort of worst case scenario that will reveal compression, cabinet or other vibrations, buzzes and resonances and changes in the response shape and at what point in the frequency bandwidth these occur at. CEA-2010 will often produce slightly higher results especially in the upper bass range where distortion is generally lower. It is not too uncommon to be able to generate more output in the deep bass during the sweep because distortion is not limited during that test type where as a CEA-2010 passing result requires the distortion to be below a certain threshold. Another difference that may be seen is distortion levels between the two tests. This is partly due to the test signal and partly because with CEA-2010 it is easier to control the input level used for each burst. Another thing to consider with CEA-2010 you may often be able to eke out another 0.5 to 1.0dB by greatly increasing the input signal to the system but it may come with a large increase in distortion. Often it will still come in under the thresholds set for a passing result though, so is it better to present the lower distortion result or the higher SPL? I err towards the side of higher SPL as long as the result is still "passing". Both types of tests together give a good picture of the headroom and tracking abilities that a system will have with demanding or highly dynamic material along with distortion characteristics.
Ricci is offline  
Reply Subwoofers, Bass, and Transducers

User Tag List

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


Forum Jump: 

Posting Rules  
You may not post new threads
You may not 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 code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off