Need help with ETF and feedback into system... (1 Viewer)

[Craig Chase]

I just saw the part about the BFD-Pro, too... sorry about that.

And Dave, Since you want to correct for room modes, as BruceD suggests, you want a greater than 200 MS response sweep, which will show where your peaks are...

Then you want to flatten those peaks as much as possible, WITHOUT causing a lot of nulls... IT is FAR better to "tame" a peak than to "pump up" a null ...

 

[Wayne A. Pflughaupt]

*sigh* This “rule” of sub EQing just won’t die, will it? Depending on the curve you have, boosting or cutting can be academic in the end, so I usually recommend taking the approach that uses the fewest filters, rather than religiously avoiding boosts all together.

For instance, if you have only a couple of low points to deal with, it’s of no benefit to go overboard cutting everything in site to bring everything else down to that level. Details at this old post of mine:

http://www.hometheaterforum.com/htfo...17#post2034217

Regards,
Wayne A. Pflughaupt

 

[Craig Chase]

Wayne, I agree... if you look a few posts earlier, we already discussed getting the flattest response possible with location. Then use the BFD to finish the job.

THEN adjust for a curve which may sound better to Dave.

 

[Dave Dahl]

Bruce,

The highest the time slice option seems to go is 160. Am I missing something?

-Dave

 

[BruceD]

Dave,

My apologies, I wasn't referring to the Slice Spacing , but instead to the Gate Time.

The Gate Time dictates how long a time period is actually analyzed during the FFT analysis. If the Gate Time is too short, the modal reflections simply won't show up on the graph at all.

The initial impulse response records everything, so you can go back and re-look at the originally recorded data with different settings (longer Gate Time ) to get a more detailed picture.

On the low frequency graph, the Gate Time is adjustable up to 1500ms, although as I said something >200ms is probably all that is necessary.

 

[Dave Dahl]

Bruce,

It's interesting that you've said this. I have, in fact, already had the gate time set to slightly over 200.

What should the slice time be?

-Dave

ps. thank for the help everybody. It's great that the people on this forum take time out of their busy days to help each other.

 

[BruceD]

Dave,

The number of slices and the slice time are really only relavent to reverberation decay. i.e. multiple slices with "user-selectable" times between slices isn't going to provide much more information than the single time slice described below.

What multiple slices can confirm is what frequencies are mostly reverberation components and how long they take to decay (i.e. similiar graphs of multiple slices liked you described).

By using a single time slice (1) and setting the Gate Time to >200ms, the low frequency graph includes both the speaker's initial response plus the room's contribution similiar to the way your ears hear it.

In evaluating this one graph, the sharp peaks and dips are where your ear will hear the bass peaks and nulls.

 

[David Fabrikant]

This is really a great thread and offers an abundance of knowledge to the general public.

As my name was mentioned here, I must make a few comments as to some of Craig's posts:



I did NOT state this, nor would I ever. I just re-read an email you sent me where you stated that you actually placed your mic so it was sitting on top of a subwoofer while you measured a speaker. As I told you in the email, you can not do this! I do not want to get into a technical discussion of the problems associated with this but it negates ALL measurements,. as I am sure BruceD would agree with. A mic must be fully isolated and as far away from reflective objects as possible.

Craig, please, do not use me as a basis or verification of the accuracy of your measurements. It is true that I spent quite a bit of time assisting you but you cut this short when you did not send me many of the very specific measurements I asked for, nor any of the digital pictures of the room, speaker locations, mic location, and testing rig. The process of me evaluating your system ended there

You have forced me to say this publicly.. In no way do I or anyone at Ascend Acoustics verify and confirm the accuracy of Craig Chase's measurement setup. Quite the opposite, actually.

Please be extra careful to not publicy state false information about me again. Forgive and forget this time...

 

[Craig Chase]

I now understand why some people tape phone conversations.

 

[Parker Clack]

Moderators note:

I have reopened this thread so that Dr. Fabrikant was able to respond to comments that were made about previous conversations.

I remind everyone to keep this civil.

Parker

 

[BruceD]

David,

Thanks for the clarification. I think it always has a positive influence on forum discussions when industry professionals weigh-in with their perspectives and observations.

Also, thanks for your kind words.