SEOS 12/AE TD12M Project - Page 14 - AVS Forum
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post #391 of 401 Old 11-03-2013, 05:52 PM - Thread Starter
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Quote:
Originally Posted by splotten View Post

Floor bounce maybe?

http://tripp.com.au/avfcbm.htm

I ran out of free time today. I left the center speaker as is and will grab some near field measurements and see if there is any difference closer. It definitely could be floor bounce. I am hoping the near field will give me a better picture. Then I will drag them outside individually.
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post #392 of 401 Old 11-03-2013, 08:54 PM
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Take a measurement with each driver individually. You can see if it is just interaction or something else. If it is, fixing the crossover would be the solution.

Take measurements with mic at different positions.

Take measurements with speaker at different distances from the wall behind it.

Also cover over the front of the waveguide and take a measurement. I have seen several measurements that were affected by that.

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post #393 of 401 Old 11-04-2013, 06:55 AM - Thread Starter
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Quote:
Originally Posted by John_E_Janowitz View Post

Take a measurement with each driver individually. You can see if it is just interaction or something else. If it is, fixing the crossover would be the solution.

Take measurements with mic at different positions.

Take measurements with speaker at different distances from the wall behind it.

Also cover over the front of the waveguide and take a measurement. I have seen several measurements that were affected by that.

I appreciate the guidance John. I got my sons ear protection out and am trying to see if he will "help" me take measurements today. biggrin.gif
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post #394 of 401 Old 11-04-2013, 08:20 AM - Thread Starter
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I managed a couple more. I made it into a game for my son. It didn't last long though. biggrin.gif

I started with the Center channel Track 2 FR 1ft 6in from baffle and in between the drivers and Stock Tweeter Polarity


Left channel Track 6 FR 1ft 6in from baffle and in between the drivers Swapped Tweeter Polarity (for comparison)


Then I swapped the center channels tweeter polarity
Center channel Track 2 FR 1ft 6in from baffle and between the drivers with Swapped Tweeter Polarity


I had to take a break for a bit for my sons sake and mine. We are working on task transition and it is slow going. cool.gif

It looks like the weird dip between 1200-2200 is smoothed right out. There are still a couple dips here and there centered at 550, 980, and 180.
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post #395 of 401 Old 11-27-2013, 08:58 PM - Thread Starter
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Quote:
Originally Posted by splotten View Post

Floor bounce maybe?

http://tripp.com.au/avfcbm.htm

So I went in and converted all my numbers to mm. None of my measured nulls matched the results from the calculator with regard to floor bounce. I am questioning if any of the results from the calculator can be taken into account due to the vaulted ceiling in this room. Do you think this factor can skew the results for both or either calculation? I am hoping to try moving the speakers around including away from the side walls and see how that effects this nasty dip I have.

I have also looked into paneling the wall behind the speakers but opened a can of worms that will take some research. I have seen 703 recommended from time to time and will continue my search.
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post #396 of 401 Old 11-28-2013, 05:01 AM
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So by flipping the polarity on the center channel we know that this cures the dip in the near field, as shown in that measurement above, but have you measured the center channel with the polarity reversed at the main listening position to see if that cured it?

I see where you are sitting 14' back from the center channel. Do you have a coffee table or any other furniture in between these two spots? You might look into some OC703 panels on the side walls. The best thing to do would be add some on the ceiling as well, but with a vaulted ceiling, and the WAF, that could prove hard to do!

I am still interested in finding out why the measured response is so different from the modeled response? What modeling program did you use?,
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post #397 of 401 Old 11-28-2013, 08:05 AM - Thread Starter
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Quote:
Originally Posted by Martycool007 View Post

So by flipping the polarity on the center channel we know that this cures the dip in the near field, as shown in that measurement above, but have you measured the center channel with the polarity reversed at the main listening position to see if that cured it?

I see where you are sitting 14' back from the center channel. Do you have a coffee table or any other furniture in between these two spots? You might look into some OC703 panels on the side walls. The best thing to do would be add some on the ceiling as well, but with a vaulted ceiling, and the WAF, that could prove hard to do!

I am still interested in finding out why the measured response is so different from the modeled response? What modeling program did you use?,

Yes, I measured both and the dip was more pronounced at both near field and at my MLP using the stock polarity. Reversing the polarity on the cd smoothed out the dip in the crossover region in both locations.

I was sitting on the couch just after I posted this and looked down at the coffee table and had the same thought. I want to measure with the table removed and see what the results are. My room is a hot mess, I knew it would be the biggest issue I had. I am also still on concrete floors. We are going to try the addition of an area rug as well, but that won't be an option until January or so. The wife is ok with the 2" 703 panels. smile.gif I do other projects to her satisfaction ad she knows that audio is my vice, so she has just about given me free range.

I didn't model these. I had input from several other people that had built these before and they helped check my math for tuning and enclosure volume. This is my maiden voyage with regards to measuring and trying to optimize, this could be an error in my methods. That is why I try and post everything and ask as many questions as possible. smile.gif

Chris
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post #398 of 401 Old 11-28-2013, 08:29 AM
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The easiest way to determine which issues are from reflections is looking at the impulse response. You can see bumps that occur at a given time after the initial impulse. Looking at the amount of time between that initial impulse and the impulse of the reflection lets you determine the difference in distance between the initial impulse and the reflected. Gating out those reflections lets you then measure only the direct response of the speaker.
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post #399 of 401 Old 11-28-2013, 07:12 PM - Thread Starter
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Quote:
Originally Posted by John_E_Janowitz View Post

The easiest way to determine which issues are from reflections is looking at the impulse response. You can see bumps that occur at a given time after the initial impulse. Looking at the amount of time between that initial impulse and the impulse of the reflection lets you determine the difference in distance between the initial impulse and the reflected. Gating out those reflections lets you then measure only the direct response of the speaker.

I opened OmniMic and started reading the help tab and found the information you are referring to. Thank you for the direction John. I have a lot to learn.
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post #400 of 401 Old 02-22-2014, 10:09 AM
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Whoa! These are awesome!!!
I can see building something like this for my L/C/R's.
Can you by chance give the external measurements for these cabinets?
I wonder how well these would work with a couple of LilWreckers on the front wall underneath..
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post #401 of 401 Old 02-24-2014, 09:56 AM
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filtor1, I may have missed it but can you tell me what the external dims of your cabinets are?
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