About The Sub Zone: Testing Methodology and Environment - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

Reply
 
Thread Tools
post #21 of 37 Old 11-02-12, 11:33 AM
Senior Shackster
Erin
 
Join Date: Aug 2009
Location: North, Alabama
Posts: 290
Re: About The Sub Zone: Testing Methodology and Environment

Quote:
acoustat6 wrote: View Post
Thats great, we have to show consistency and that is why you should start measuring at 75db. That is what everyone else is holding to at REW forum, unless there is a house curve or for measuring for compression.
Why 75dB? I think it's more important to start somewhere where compression becomes a legitimate concern. If the driver is moderately efficient (mid 80's), compression isn't of concern until you're at least there. So, to me, 75dB testing is moot.

Quote:
acoustat6 wrote: View Post

"While 75db is the default for REW it is hardly a standard per se. There has been a lot of emphasis over the years on 75db being a standard of some sort but it is really just a reference guideline for level setting speakers. "

Right, so stick with it! If you started at 75db then you could go up in 10 db increments and have this reapeatable for all of your measurements. Would this not make sense from a sciencetific/reference standard.

Looking at your graphs of the 5 woofers that you measured there are no target lines. If you are not measuring at 75db you then need to state the target level for the measurenent taken. IE: on the graph for the Emotiva where would you place the target level? And in the graph for the SVS is the target level 116db? If so you missed it by 20db!
I have a very fundamental issue with the talk around compression testing here. What's catching me off guard here is people saying to test compression by increasing the output to achieve 10dB steps. This is flawed. Compression shouldn't be solely focused on the FR. Compression is a measurement of input vs output. It is not a measurement of response as you increase the output itself. For example, if you increase the input voltage at a speaker's terminals then you should get that same relational value in dB output by the DUT. Anything less is due to the effect of compression.

Yes, you are looking to see how the response changes but what's the point if a driver is so inefficient at higher output that you're having to feed it twice as much as you should for the same output?

Consider this: What happens if you're increasing SPL by 10dB but your voltage ratio from your previous input voltage of 4v to your new voltage input, which should be 12.6 volts, is actually 14.6v? All you've done is increase the output but you've failed to acknowledge the 2v loss in your test, which equates to about 14watts or 6dB! Yikes! So, yea, the curve at the reference frequency increased by 10dB, but it's not illustrating the fact that you just had to make up more than 6dB by turning the amp gain up higher and higher.

This is what compression testing should tell you. Again, voltage in vs SPL out vs what should be there. Then you get the FR curve, but most importantly, you get to see how efficiently the driver is able to use the power provided to it.

Hope that makes sense. Maybe my assumption on how this kind of testing is being performed is wrong so please correct me if so.

- Erin


Below I've attached a picture of compression testing I did on a Seas w18nx driver. This is the 20-110hz band. As long as the lines are stacked on top of each other, what you're seeing is what is expected; no loss in output vs voltage input. Where the lines deviate, is an indication of how much output (in dB) is lost with the input vs the initial voltage vs frequency. As you go higher in frequency in the chart, you can see a loss of about 0.4dB from 1v to 8v input.






This is the same thing but from 400hz to 6khz. You can see a loss of about 0.8dB at 3800hz. Likely due to inductance issues (yet to verify).

Erin H is offline  
Sponsored Links
Advertisement
 
post #22 of 37 Old 11-02-12, 12:13 PM Thread Starter
Elite Shackster
 
Dale Rasco's Avatar
Dale Rasco
 
Join Date: Apr 2009
Location: Houston, Tx
Posts: 4,127
My System
Re: About The Sub Zone: Testing Methodology and Environment

Quote:
acoustat6 wrote: View Post
Thats great, we have to show consistency and that is why you should start measuring at 75db. That is what everyone else is holding to at REW forum, unless there is a house curve or for measuring for compression.
Bob, I understand what your preference would be however; I have clearly outlined what the methodology is and how I will go about taking the measurements. If I were to cater to everyone's preference I would never get anything done. The purpose here is to compare my measurements to the measurements posted, published, etc by the manufacturer. 75db is not a standard. I do not know how else to explain that. Additionally this is not REW forum discussion, The Sub Zone is it's own forum and the fact that I happen to use REW is irrelevant to this discussion outside of the defined methodology. The consistency comes from the measurements listed and outlined below taken directly from the methodology.

Frequency Response (FR)
Frequency response is measured utilizing a 512K (11.9s) sine sweep from 0 Hz to 200 Hz via REW (Room Equalization Wizard). The microphone is placed on the ground at a 2 meter distance measured from the center of the subwoofer driver. In the event a particular subwoofer requires a deviation from this it will be noted within that particular set of measurements. For example, if a ported/vented sub with multiple drivers requires different mic placement in order to capture accurate results, it will be spelled out within that particular subwoofer test.

Long Term Output
Maximum long-term output is measured using a 1M (23.8 second) sine sweep from 0 Hz to 200 Hz. The first sweep is taken after level matching 50Hz at 90db. The level is then raised by 5 db for each successive sweep until the output level is clearly compressed. Compression measurements are taken at the same time as the max output. The compression graph reflects the relative compression to the original 90 db sine sweep.

Quote:
acoustat6 wrote: View Post
Right, so stick with it! If you started at 75db then you could go up in 10 db increments and have this reapeatable for all of your measurements. Would this not make sense from a sciencetific/reference standard.
You have just made my point. I could start using 75db, but it is irrelevant to the tests that I perform. Saying it repeatedly does not make it true. You are more than welcome to start your own forum and start all of your measurements at 75db or whatever number you would like. Starting at 75db and moving it up 10db per sweep is no more scientific than starting at 90db and raising it by 5db as I have outlined in the methodology.

Quote:
acoustat6 wrote: View Post
Looking at your graphs of the 5 woofers that you measured there are no target lines. If you are not measuring at 75db you then need to state the target level for the measurenent taken. IE: on the graph for the Emotiva where would you place the target level? And in the graph for the SVS is the target level 116db? If so you missed it by 20db!
Uhm.. What? I did state the target. 'From 0 Hz to 200 Hz starting at 90db and raising it 5db until the signal compressed. Please let me know what part of this is unclear to you.

Quote:
acoustat6 wrote: View Post
Of course it would, you are describing what you hear in your room, we need to see the actual in room freq resp to correlate what is measured with what is heard.
One has absolutely nothing to do with the other. You cannot correlate a subjective opinion to a sine sweep. The best you could hope for is to correlate it to a given part of a song or film that I happen to capture that I also commented on. Subjective, emotional responses to audio are not measurable.

Regards,
Dale Rasco



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.


“Opportunity is missed by most people because it is dressed in overalls and looks like work." -Thomas A. Edison


Dale Rasco and
To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
Dale Rasco is offline  
post #23 of 37 Old 11-03-12, 04:11 AM
Elite Shackster
 
robbo266317's Avatar
bigbadbill
 
Join Date: Sep 2008
Location: Newcastle Australia
Posts: 5,771
Re: About The Sub Zone: Testing Methodology and Environment

OK, You have my attention. Nice work Dale.

Silence is golden but duct tape is silver.

DIY completed:

To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
robbo266317 is offline  
 
post #24 of 37 Old 11-03-12, 06:18 AM Thread Starter
Elite Shackster
 
Dale Rasco's Avatar
Dale Rasco
 
Join Date: Apr 2009
Location: Houston, Tx
Posts: 4,127
My System
Re: About The Sub Zone: Testing Methodology and Environment

Thanks Bill, I have some cool stuff headed to the Sub Zone so stay tuned!

Regards,
Dale Rasco



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.


“Opportunity is missed by most people because it is dressed in overalls and looks like work." -Thomas A. Edison


Dale Rasco and
To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
Dale Rasco is offline  
post #25 of 37 Old 11-03-12, 06:20 AM Thread Starter
Elite Shackster
 
Dale Rasco's Avatar
Dale Rasco
 
Join Date: Apr 2009
Location: Houston, Tx
Posts: 4,127
My System
Re: About The Sub Zone: Testing Methodology and Environment

Quote:
Erin H wrote: View Post
Why 75dB? I think it's more important to start somewhere where compression becomes a legitimate concern. If the driver is moderately efficient (mid 80's), compression isn't of concern until you're at least there. So, to me, 75dB testing is moot.



I have a very fundamental issue with the talk around compression testing here. What's catching me off guard here is people saying to test compression by increasing the output to achieve 10dB steps. This is flawed. Compression shouldn't be solely focused on the FR. Compression is a measurement of input vs output. It is not a measurement of response as you increase the output itself. For example, if you increase the input voltage at a speaker's terminals then you should get that same relational value in dB output by the DUT. Anything less is due to the effect of compression.

Yes, you are looking to see how the response changes but what's the point if a driver is so inefficient at higher output that you're having to feed it twice as much as you should for the same output?

Consider this: What happens if you're increasing SPL by 10dB but your voltage ratio from your previous input voltage of 4v to your new voltage input, which should be 12.6 volts, is actually 14.6v? All you've done is increase the output but you've failed to acknowledge the 2v loss in your test, which equates to about 14watts or 6dB! Yikes! So, yea, the curve at the reference frequency increased by 10dB, but it's not illustrating the fact that you just had to make up more than 6dB by turning the amp gain up higher and higher.

This is what compression testing should tell you. Again, voltage in vs SPL out vs what should be there. Then you get the FR curve, but most importantly, you get to see how efficiently the driver is able to use the power provided to it.

Hope that makes sense. Maybe my assumption on how this kind of testing is being performed is wrong so please correct me if so.

- Erin


Below I've attached a picture of compression testing I did on a Seas w18nx driver. This is the 20-110hz band. As long as the lines are stacked on top of each other, what you're seeing is what is expected; no loss in output vs voltage input. Where the lines deviate, is an indication of how much output (in dB) is lost with the input vs the initial voltage vs frequency. As you go higher in frequency in the chart, you can see a loss of about 0.4dB from 1v to 8v input.






This is the same thing but from 400hz to 6khz. You can see a loss of about 0.8dB at 3800hz. Likely due to inductance issues (yet to verify).

Wow Erin, that is a great example! Thank you for contributing your knowledge to the conversation!

Regards,
Dale Rasco



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.


“Opportunity is missed by most people because it is dressed in overalls and looks like work." -Thomas A. Edison


Dale Rasco and
To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
Dale Rasco is offline  
post #26 of 37 Old 11-03-12, 12:11 PM
Senior Shackster
Bob
 
Join Date: Mar 2008
Location: Barkhamsted, CT
Posts: 164
Re: About The Sub Zone: Testing Methodology and Environment

Hi Dale, I will give you that what you are measuring, the reason why and your methodology is different form mine. As this is your forum, so be it.

Though, I have no idea why you would bother measuring speakers like this, but thats OK, I am a little behind the obvious learning curve. Does it not matter most what the speaker is doing in your room, rather than out in your driveway? But that is your methodology, and I will respect it.

But when you measure your system as you listen to it in your room, and give SUBJECTIVE reports to how it sounds then I am sure you will go by the standard REW specifications.

You have not answered my question as to which SPL meter you use, .... so please do.

Dale said, "Uhm.. What? I did state the target. 'From 0 Hz to 200 Hz starting at 90db and raising it 5db until the signal compressed. Please let me know what part of this is unclear to you.

Uhm....Yes that is correct, you have to state a target level as you are the one measuring. Otherwise I can infer any level I want to on your graph if you don't state what is the actual level. So you say that in all of your graphs, the first measurement is 90db going up in 5db increments, is that correct? Then looking at the following graphs:
the Axiom your initial reading of 90db is 4db too high.
the Chase is so wrong I dont know what to say
the Emotiva is 5db to high
the power soud is about correct is about correct but we need to see it overall freq response since it is clearly not a "subwoofer"
the svs graph clearly shows that you did not correlate 90db with you intended target.

Dale said, "One has absolutely nothing to do with the other. You cannot correlate a subjective opinion to a sine sweep. The best you could hope for is to correlate it to a given part of a song or film that I happen to capture that I also commented on. Subjective, emotional responses to audio are not measurable."

I say, really? Then why are you measuring? If measured freq response has no correlation with what you are hearing, why bother measuring?


Bob
"Make more progress, less excuses"
acoustat6 is offline  
post #27 of 37 Old 11-03-12, 12:28 PM
Elite Shackster
 
Sonnie's Avatar
 
Join Date: Apr 2006
Location: L.A. (Lower Alabama)
Posts: 22,577
My System
Re: About The Sub Zone: Testing Methodology and Environment

Quote:
acoustat6 wrote: View Post
Though, I have no idea why you would bother measuring speakers like this, but thats OK, I am a little behind the obvious learning curve. Does it not matter most what the speaker is doing in your room, rather than out in your driveway? But that is your methodology, and I will respect it.
I can answer this one...

Take a look at our Subwoofer Tests - Archived forum.

That forum has more views than any other forum on our site with as few threads as it has. 10's of thousands of views for most of the threads... most likely over a million views total. Obviously there are quite a few viewers who appreciate this type of testing. We are indeed going one step farther with subjective reviews on many of these we will be testing. We will try to do them all if we can. However, the purpose of our testing has been thoroughly explained.
Sonnie is offline  
post #28 of 37 Old 11-03-12, 01:41 PM Thread Starter
Elite Shackster
 
Dale Rasco's Avatar
Dale Rasco
 
Join Date: Apr 2009
Location: Houston, Tx
Posts: 4,127
My System
Re: About The Sub Zone: Testing Methodology and Environment

Quote:
acoustat6 wrote: View Post
Hi Dale, I will give you that what you are measuring, the reason why and your methodology is different form mine. As this is your forum, so be it.

Though, I have no idea why you would bother measuring speakers like this, but thats OK, I am a little behind the obvious learning curve. Does it not matter most what the speaker is doing in your room, rather than out in your driveway? But that is your methodology, and I will respect it.

But when you measure your system as you listen to it in your room, and give SUBJECTIVE reports to how it sounds then I am sure you will go by the standard REW specifications.

You have not answered my question as to which SPL meter you use, .... so please do.

Dale said, "Uhm.. What? I did state the target. 'From 0 Hz to 200 Hz starting at 90db and raising it 5db until the signal compressed. Please let me know what part of this is unclear to you.

Uhm....Yes that is correct, you have to state a target level as you are the one measuring. Otherwise I can infer any level I want to on your graph if you don't state what is the actual level. So you say that in all of your graphs, the first measurement is 90db going up in 5db increments, is that correct? Then looking at the following graphs:
the Axiom your initial reading of 90db is 4db too high.
the Chase is so wrong I dont know what to say
the Emotiva is 5db to high
the power soud is about correct is about correct but we need to see it overall freq response since it is clearly not a "subwoofer"
the svs graph clearly shows that you did not correlate 90db with you intended target.

Dale said, "One has absolutely nothing to do with the other. You cannot correlate a subjective opinion to a sine sweep. The best you could hope for is to correlate it to a given part of a song or film that I happen to capture that I also commented on. Subjective, emotional responses to audio are not measurable."

I say, really? Then why are you measuring? If measured freq response has no correlation with what you are hearing, why bother measuring?


Bob
"Make more progress, less excuses"
I keep forgetting the SPL, it is a Galaxy CM140. For measuring I am using the IBF.

Quote:
acoustat6 wrote: View Post
the first measurement is 90db going up in 5db increments, is that correct?
No, what I stated was that the volume is level set at to 90db AT 50Hz and then I will begin the sweeps and raise the volume by 5db.

Quote:
acoustat6 wrote: View Post
the Chase is so wrong I dont know what to say
If you would actually read the words instead of just looking at the pictures you would have seen at the top of the Chase test that I stated:
"Before we start I would like to say that the tests that I did back in February on the Chase VS-18.1 were performed before any methodology was written for The Sub Zone and as a result the measurements for max output were based on maintaining <10% THD. This is different than other tests that have been performed on this beast utilizing the CEA 2010 standard."
Quote:
acoustat6 wrote: View Post
I say, really? Then why are you measuring?
To show an estimated room gain benefit.

Bob, I am done trying to help you grasp this as it seems you only really want someone to argue with.

Regards,
Dale Rasco



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.


“Opportunity is missed by most people because it is dressed in overalls and looks like work." -Thomas A. Edison


Dale Rasco and
To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
Dale Rasco is offline  
post #29 of 37 Old 11-03-12, 01:46 PM Thread Starter
Elite Shackster
 
Dale Rasco's Avatar
Dale Rasco
 
Join Date: Apr 2009
Location: Houston, Tx
Posts: 4,127
My System
Re: About The Sub Zone: Testing Methodology and Environment

Quote:
ironglen wrote: View Post
I guess no spl capability will be tested since that would be a very long power run; even at low current it will require a decent gauge cord.

Cool idea
Hey Glen, sorry I missed this one. I have been working out the SPL thing. I actually think it will be possible but probably will not be added until next Spring.

Regards,
Dale Rasco



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.


“Opportunity is missed by most people because it is dressed in overalls and looks like work." -Thomas A. Edison


Dale Rasco and
To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.



To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
Dale Rasco is offline  
post #30 of 37 Old 11-03-12, 04:51 PM
Senior Shackster
Erin
 
Join Date: Aug 2009
Location: North, Alabama
Posts: 290
Re: About The Sub Zone: Testing Methodology and Environment

Dale,
I really do implore you to consider what I wrote above regarding the fundamental purpose of compression testing. Raising the output by 5dB doesn't really tell us anything about compression other than how the curve changes. That's fine... but that's only one (small) part of compression. We need a way to gauge input voltage for each step vs output SPL. You can do this pretty easily with online calculators. Just figure what each voltage input will be, in steps, and that should tell you what your output should be. Make a table with 6-7 stepped voltages, then the theoretical (what you should get, if compression were not inherent in design), and the real result. Then you'll see how much output in SPL is lost due to inefficiency at your reference frequcney of 50hz and you can still provide your FR curves so we can see how the overall curve is affected. It's not quite as pretty as the examples I gave above, but it'll suffice. Once I get set up, I will be providing the compression testing the same way as I did above. Flying in the face of apparent standard REW convention. lol.


Playing devil's advocate: As far as subjective vs objective, I actually agree. I'm more of a 'let the data talk' kind of guy. I stay away from subjective thoughts regarding sound; I freely talk subjectively on my likes/dislikes with a product interface, usability, etc. I do agree that when a subjective review is given, objective data should be provided to help the both the reviewer and the viewers (possibly) understand why your subjective analysis came out the way it did. Subwoofers are especially prone to placement and as we know placement will dictate response at the seated position. A simple 6 point spatial average of frequency response would suffice in objective/subjective correlation.


Just my $.02....

- Erin
Erin H is offline  
Reply

Bookmarks

Tags
environment , methodology , testing , zone

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