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post #91 of 600 Old 07-06-2013, 10:45 AM - Thread Starter
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Originally Posted by Joshjp View Post

Have you made a graph with only one sub on?

I did yes, but I can't seem to find them amongst my plethora of graphs. I will do just an on/off graph and post it here.

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With my dual xv-30's i get a better response with one sub on, now i stacked them and the same happends, btw are graphs are almost the same.

You, I thought of that this morning..... stacking them, but I really don't have any place I could move them where they'd be stackable.

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post #92 of 600 Old 07-06-2013, 11:21 AM
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Yes , a single fv 15 would fit behind the couch perfectly. smile.gif

I would love to compare these to two Rythmiks or SVS Ultras to see if there was any huge difference. Hmmmm..... Wife- or more speakers-wife-or more speakers eek.gif

Anyways.... I got the traps in floor to ceiling and treated the entire upper front wall with 4" thick OC. What a job that was. I have just enough panels left for first reflection and rear walls. If the ceiling clouds aren't much more I'll buy them vs. make them. With my wall treatments/traps it's no biggie because I'm throwing false walls up all around, wrapped in GOM. Anyways......

Measurements. Two graphs of the best settings, before and after treatments. The 100 hz issue is much less of an issue, but as expected the lower hz didn't change. rolleyes.gif

I can sure notice a difference in the overall sound though.



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Lol. No kidding man..... Although i didn't expect much from the low hz.

Had i known i would have gotten four vs two. I think i can get this close with an EQ.

I do have one movement option left. It would be behind the seats, but not against them. I could face the subs into the listening area pushed back just into the L area under our desk that is back there.

My friend, these "dips" are true nulls... room mode induced cancellations. Look closely at the trough of the nulls. One is at 48 Hz, and the other is at exactly double that frequency... 96 Hz. These nulls are caused by the same room dimension(s).

A frequency of 48 Hz has a wavelength of 23.46 ft. The 1/4 wavelength is 5.87 ft.
http://www.1728.org/freqwavf.htm

If you have one or more room boundaries at 5.9 ft from the LP, it is these dimensions that are causing the cancellations. Floor/ceiling, front/back walls, side walls, if they converge at 5.9 ft., they are your problems Your *best* solution is to move your listening position out of these dimensions.

More importantly, because these nulls are cancellations, they don't respond to EQ. Adding energy, (boost) to a cancellation just cause more cancellation. EQ can be effectively used to knock down peaks, such as the ones you have at 37, 63 and 78 Hz. But boosting nulls is not an effective use of EQ. In fact, it is detrimental to use EQ to try to boost nulls; it uses amplifier power and driver excursion without having any impact on the problem. It eats up massive amounts of headroom, adds distortion and it will make the sound in other locations REALLY bad.

The good news is that nulls are not "heard." You "hear" peaks as boominess and smearing of bass notes. But the sound in the null is cancelled, like noise cancelling headphones. So all you might notice is some thinness, especially of the fundamentals of notes in the range of the null. Still, a null over a brad range of frequencies, like the 48 Hz null, which extends from 42 to 58 Hz, will have a significant impact on the

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I do have one movement option left. It would be behind the seats, but not against them. I could face the subs into the listening area pushed back just into the L area under our desk that is back there.
Looking at your pics, that would have been my 2nd option, the first being as far back into that L area as you could get, preferably on the opposite side wall from the sub in the front. Can you try either of those locations?

Nonetheless, IMO, the *best* option you have is to move your listening position OUT of the nulls.

Craig

PS. It's hard to tell from your pics, but it looks like you're measuring from the point between the 2nd and 3rd seat. No one will ever sit there, (unless you shift the entire row left or right.) Try picking either the 2nd or 3rd seat, make it the primary LP, and then measure from there. You may find that the nulls you're measuring are in a location where no one will ever hear them, and the response at your "new" primary LP is better than at your current measuring location.

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post #93 of 600 Old 07-06-2013, 11:52 AM
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Originally Posted by pdxrealtor View Post

I did yes, but I can't seem to find them amongst my plethora of graphs. I will do just an on/off graph and post it here.
You, I thought of that this morning..... stacking them, but I really don't have any place I could move them where they'd be stackable.
OK great i would like to see them to see if they are close to my graphs.

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post #94 of 600 Old 07-06-2013, 12:27 PM - Thread Starter
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My friend, these "dips" are true nulls... room mode induced cancellations. Look closely at the trough of the nulls. One is at 48 Hz, and the other is at exactly double that frequency... 96 Hz. These nulls are caused by the same room dimension(s).

A frequency of 48 Hz has a wavelength of 23.46 ft. The 1/4 wavelength is 5.87 ft.
http://www.1728.org/freqwavf.htm

If you have one or more room boundaries at 5.9 ft from the LP, it is these dimensions that are causing the cancellations. Floor/ceiling, front/back walls, side walls, if they converge at 5.9 ft., they are your problems Your *best* solution is to move your listening position out of these dimensions.

My seat to ceiling height is 4.91 ft, The Mic to side wall is 8ft. (but above the ledge 8'10") I also have the alcove area which is being wall off to be symmetric with the upper and lower walls respectively. So currently the alcove area adds 2-3 ft of depth depending on height. The mic to back wall is 5 ft. exactly. The mic to front wall is 10 ft exactly.

It seems I have a few boundaries that are close to the 5.9' problem area, though not exact.

I don't know how much it matters about the side wall having the alcove area. But it's next on my list to fix that area.


More importantly, because these nulls are cancellations, they don't respond to EQ. Adding energy, (boost) to a cancellation just cause more cancellation. EQ can be effectively used to knock down peaks, such as the ones you have at 37, 63 and 78 Hz. But boosting nulls is not an effective use of EQ. In fact, it is detrimental to use EQ to try to boost nulls; it uses amplifier power and driver excursion without having any impact on the problem. It eats up massive amounts of headroom, adds distortion and it will make the sound in other locations REALLY bad.

While not what I wanted to hear- I kind of suspected from what others have said that I would have this issue.

The good news is that nulls are not "heard." You "hear" peaks as boominess and smearing of bass notes. But the sound in the null is cancelled, like noise cancelling headphones. So all you might notice is some thinness, especially of the fundamentals of notes in the range of the null. Still, a null over a brad range of frequencies, like the 48 Hz null, which extends from 42 to 58 Hz, will have a significant impact on the

Looking at your pics, that would have been my 2nd option, the first being as far back into that L area as you could get, preferably on the opposite side wall from the sub in the front. Can you try either of those locations?

I can go all the way back in the opposite corner of the L area. Will it have an affect if the cabinet is placed on its side vs. standing up? There is a sliding glass door back there so I'd much rather stand it up in the very corner vs. lay it down in front of the glass. However, the front speaker needs to remain on it's side.

Potential problem?? Would there be any affect of standing both speakers upright in the front of the room vs. them laying on their side? Guess I could just try it.



Nonetheless, IMO, the *best* option you have is to move your listening position OUT of the nulls.

Below is a graph with a movement of the mic back towards the back wall. I'm not sure how much closer to the back wall I can go because of the massive rear surrounds. I like the idea of putting the one sub in the back corner of the L area and keeping the seating at the 4-5 ft. mark. Currently the two center chairs are at 5'.

Craig

PS. It's hard to tell from your pics, but it looks like you're measuring from the point between the 2nd and 3rd seat. No one will ever sit there, (unless you shift the entire row left or right.) Try picking either the 2nd or 3rd seat, make it the primary LP, and then measure from there. You may find that the nulls you're measuring are in a location where no one will ever hear them, and the response at your "new" primary LP is better than at your current measuring location.

You are correct. I've moved the mic in between chairs and gotten big differences, but have not focused yet on placing the mic in one chair. I would like to have a nice average between the two center chairs.

See replies in above in bold

Thanks for the advice. Gives me a lot to think about and some options to explore. I will most likely get more out of your post when I read it a couple more times at a later time. I always seem to pick up more when I walk away and come back and read again later.

Here's that graph of the mic in center of the room (8 ft) and back from the 5ft mark to the 43" mark.


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post #95 of 600 Old 07-06-2013, 01:49 PM
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From that graph, I would set up a "house curve" from 70dB @ 20Hz to 65dB @ 100Hz and live with a tiny drop at 50Hz.

Do you have any way to eq yet or do you still need the exercise?

 

I, too, have found that slight changes in mic position have a dramatic effect on REW results.

http://www.hometheatershack.com/forums/rew-forum/52923-location-location-location.html

 

Sorry I can't help with the insulation question. My only experience is first hand and unpleasant, so I avoid the stuff as much as possible.


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post #96 of 600 Old 07-06-2013, 02:05 PM - Thread Starter
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From that graph, I would set up a "house curve" from 70dB @ 20Hz to 65dB @ 100Hz and live with a tiny drop at 50Hz.
Do you have any way to eq yet or do you still need the exercise?

I, too, have found that slight changes in mic position have a dramatic effect on REW results.
http://www.hometheatershack.com/forums/rew-forum/52923-location-location-location.html

Sorry I can't help with the insulation question. My only experience is first hand and unpleasant, so I avoid the stuff as much as possible.

LOL.... My Rane PE-17 will be here on Monday, but it's an analog. I might swap that out for a BFD or , ugg... a MiniDSP, but we will see.

I just scrubbed down with some soap that has a built in brush in it. Cool stuff actually. It's the wifes. I had long sleeves, long pants, tight gloves, a beanie cap and face mask. But I cut so much yesterday, 28 sheets, that there was just no escaping it completely.

I'll check out your post


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post #97 of 600 Old 07-06-2013, 02:12 PM
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My Rane PE-17 will be here on Monday, but it's an analog.

"Rane PE 17 Parametric EQ is a single-channel, five-band device of incredible versatility."

So that's for one sub?

Or are you going to try to EQ both subs with one curve (which can be done, it's just not ideal, hence the DSP1124P)?

confused.gif

 


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post #98 of 600 Old 07-06-2013, 02:14 PM
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I had long sleeves, long pants, tight gloves, a beanie cap and face mask. But I cut so much yesterday, 28 sheets, that there was just no escaping it completely.

And no one took a picture?!

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post #99 of 600 Old 07-06-2013, 02:20 PM - Thread Starter
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"Rane PE 17 Parametric EQ is a single-channel, five-band device of incredible versatility."
So that's for one sub?
Or are you going to try to EQ both subs with one curve (which can be done, it's just not ideal, hence the DSP1124P)?
confused.gif

News to me. I've never played with home subs, just car. So, when Tom recommended the BFD and I replied I want simple he replied the Rane, and gave a link to one. To answer your question yes i was going to EQ both subs as one, after I find ideal location, phase, etc....



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And no one took a picture?!
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Nope no pictures.... didn't even think about it for some reason.

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post #100 of 600 Old 07-06-2013, 02:22 PM
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But boosting nulls is not an effective use of EQ. In fact, it is detrimental to use EQ to try to boost nulls; it uses amplifier power and driver excursion without having any impact on the problem. It eats up massive amounts of headroom, adds distortion and it will make the sound in other locations REALLY bad.

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post #101 of 600 Old 07-06-2013, 03:36 PM
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Quote:
Originally Posted by LastButNotLeast View Post

"Rane PE 17 Parametric EQ is a single-channel, five-band device of incredible versatility."
So that's for one sub?
Or are you going to try to EQ both subs with one curve (which can be done, it's just not ideal, hence the DSP1124P)?
confused.gif
Actually, EQing BOTH subs TOGETHER is ideal. If you EQ each sub to be perfectly flat individually,.. and then you combine them, they will interact with each other and the resultant sound will no longer be flat. You don't *hear* the subs individually. You *hear* the subs together. They combine their room interactions and become one sound. Therefore, they should be EQ'd together, as one sub.

Levels and distances are open to discussion, but EQ should be applied as a single filter set to the combined output of all the subs in the system.

Craig

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Good, 'cus that's how I'm doing it now.

wink.gif

Thank you.

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post #103 of 600 Old 07-06-2013, 04:39 PM - Thread Starter
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Originally Posted by craig john View Post

Actually, EQing BOTH subs TOGETHER is ideal. If you EQ each sub to be perfectly flat individually,.. and then you combine them, they will interact with each other and the resultant sound will no longer be flat. You don't *hear* the subs individually. You *hear* the subs together. They combine their room interactions and become one sound. Therefore, they should be EQ'd together, as one sub.

Levels and distances are open to discussion, but EQ should be applied as a single filter set to the combined output of all the subs in the system.

Craig


Thanks for clarifying that. Lastbutnot through me for a loop. I couldn't see how it was possible you'd gain match the subs, play with phase, location etc all as if they were one unit only to separate them when it came to EQ. Even in car audio when using one amp for each sub we eq'd and crossovered together.
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Good, 'cus that's how I'm doing it now.
wink.gif
Thank you.
smile.gif

Oh now mention the fact..... lol.... In any event I'm glad you're doing it the correct way!

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Dumb luck.

 

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post #105 of 600 Old 07-06-2013, 05:28 PM - Thread Starter
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Right and left separate and then both together. Phase at 0 on both cabinets.


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Right and left separate and then both together. Phase at 0 on both cabinets.


I think this graph shows that the deep trough from ~40 Hz to ~60 Hz is caused by a confluence of room modes, all around the same dimensions. Note that the right sub has a trough at 46 Hz while the right sub has a lowest trough at 50 Hz, whereas the combined grapg has the trough at 48 Hz. The nulls around 96 Hz show a remarkably similar pattern.

Another interesting observation is that 1/2 of the 48 Hz frequency, 24 Hz, doesn't exhibit the null. This is probably because 24 Hz is below the room modal response point and into the "pressure vessel gain" response of the room.

In addition, this graph is a proof of the "mutual coupling theory" that we've discussed on the forum in the past: http://www.avsforum.com/t/1068195/dual-subwoofers-of-different-sizes/90#post_15011679 For the most part, these co-located subs "sum" or couple and add 6 dB across the board.

I am surprised by the relentless nature of these nulls. Usually, one can fill in a null with an additional sub, (or subs), placed in a dissimilar location, or by movement of the LP out of the null(s). Neither of those solutions seems to have any significant impact on the nulls. If the nulls where peaks, it would be easy... just EQ them down. But that doesn't work with nulls. With nulls, the only good weapons available are subwoofer and listening position adjustment.

pdx, have you been able to find any one position of a single sub anywhere in your room that doesn't exhibit these deep nulls? How about a measurement location that doesn't exhibit these nulls?

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More graphs, Moved the mic back 1 ft so it is 4 ft from the back wall on all tests. I started with mic in center, then moved to behind the right chair at ~40.5" high. I'll start with the best-

45 Phase on the left speaker, 0 on the right. Gain at 3/4 for this and all graphs below. Will the nulls around 100 be an issue? I don't understand why the AVR is not crossing them off the chart. It's set at 80hz. Anyways.. HUGE improvement. IF I am reading this right I have a little peak to bring down @ 38hz, from 83db to 73db.



Alright..... I had to get the best graph out of the way. The other graphs are tests from center of the room where all other previous test have been taken (with the exception of being a foot further back), followed by tests from dead center behind the right chair. All the same height.




This last graph below is the two best from the behind the right seat location. The higher DB line is the same measure as the first graph in this post. The graph directly above is all tests behind the right seat. I'm wondering if the black line might be the better choice as the DB are up in the lower hz, and while it dips a bit more at 48 hz it doesn't dip nearly that much at the ~100 hz area.


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post #108 of 600 Old 07-06-2013, 06:34 PM - Thread Starter
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Quote:
Originally Posted by craig john View Post

I think this graph shows that the deep trough from ~40 Hz to ~60 Hz is caused by a confluence of room modes, all around the same dimensions. Note that the right sub has a trough at 46 Hz while the right sub has a lowest trough at 50 Hz, whereas the combined grapg has the trough at 48 Hz. The nulls around 96 Hz show a remarkably similar pattern.

Another interesting observation is that 1/2 of the 48 Hz frequency, 24 Hz, doesn't exhibit the null. This is probably because 24 Hz is below the room modal response point and into the "pressure vessel gain" response of the room.

In addition, this graph is a proof of the "mutual coupling theory" that we've discussed on the forum in the past: http://www.avsforum.com/t/1068195/dual-subwoofers-of-different-sizes/90#post_15011679 For the most part, these co-located subs "sum" or couple and add 6 dB across the board.

I am surprised by the relentless nature of these nulls. Usually, one can fill in a null with an additional sub, (or subs), placed in a dissimilar location, or by movement of the LP out of the null(s). Neither of those solutions seems to have any significant impact on the nulls. If the nulls where peaks, it would be easy... just EQ them down. But that doesn't work with nulls. With nulls, the only good weapons available are subwoofer and listening position adjustment.

pdx, have you been able to find any one position of a single sub anywhere in your room that doesn't exhibit these deep nulls? How about a measurement location that doesn't exhibit these nulls?

Craig

See my graphs above! Finally a break in the 50 hz null. This did not happen when I tested at 43 or 46" before. Maybe something else was off? I'm not sure what the heck.

On the best measurements above, behind the right chair (facing the subs) I also compared a couple measures with the mic placed at listening levels while fully reclined and no difference. That's good.

Phase is definitely playing a role. The left speaker phase adjustment is huge, as you can see a single notch up or down changes a lot.

I am now going to test the exact same but behind the left chair. Which is behind the open L area.

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post #109 of 600 Old 07-06-2013, 06:51 PM
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Originally Posted by pdxrealtor View Post


See my graphs above! Finally a break in the 50 hz null. This did not happen when I tested at 43 or 46" before. Maybe something else was off? I'm not sure what the heck.

On the best measurements above, behind the right chair (facing the subs) I also compared a couple measures with the mic placed at listening levels while fully reclined and no difference. That's good.

Phase is definitely playing a role. The left speaker phase adjustment is huge, as you can see a single notch up or down changes a lot.

I am now going to test the exact same but behind the left chair. Which is behind the open L area.

Nice work! The EQ should do wonders with that peak, and then you'll be looking very good!

 

All this tweaking...it's gonna be nice when you actually can 'properly' listen to these bad boys!

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Nice work! The EQ should do wonders with that peak, and then you'll be looking very good!

All this tweaking...it's gonna be nice when you actually can 'properly' listen to these bad boys!

eek.gifeek.gifeek.gif Thanks!!!

So stoked with these results behind the right chair!

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Here is the exact same 4ft from the back wall, ~41" high behind the left chair.

I didn't separate any lines because they're all pretty visible and well, they don't appear quite as good as the right chair.


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post #112 of 600 Old 07-06-2013, 07:06 PM
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More graphs, Moved the mic back 1 ft so it is 4 ft from the back wall on all tests. I started with mic in center, then moved to behind the right chair at ~40.5" high. I'll start with the best-

45 Phase on the left speaker, 0 on the right. Gain at 3/4 for this and all graphs below. Will the nulls around 100 be an issue? I don't understand why the AVR is not crossing them off the chart. It's set at 80hz. Anyways.. HUGE improvement. IF I am reading this right I have a little peak to bring down @ 38hz, from 83db to 73db.



Alright..... I had to get the best graph out of the way. The other graphs are tests from center of the room where all other previous test have been taken (with the exception of being a foot further back), followed by tests from dead center behind the right chair. All the same height.




This last graph below is the two best from the behind the right seat location. The higher DB line is the same measure as the first graph in this post. The graph directly above is all tests behind the right seat. I'm wondering if the black line might be the better choice as the DB are up in the lower hz, and while it dips a bit more at 48 hz it doesn't dip nearly that much at the ~100 hz area.


Now we're on to something!!!

As expected, moving the measurement position turns nulls into peaks. This is how it's supposed to work! This is further evidence that the nulls are related to the room dimensions. If you were to play a 48 Hz tone, you could walk around your space and, literally, stick your head into and out of the peaks and nulls.

Going forward, here's what I would suggest: Take your measurements as "spatial averages" of the 2nd and 3rd seats plus the spot in between them. Measure at different listening distances and then place your seating at the point with the best "spatial average" of the 3 positions. If you want to go even further, take spatial averages of all 4 of your seats and the exact middle.

Now, I have a question for you... will there be a video display in this system? If so, where is it going to go? How big will it be? Will it be acoustically transparent?

Craig

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Here is the the three measurements (Left chair, center, right chair) at the best phase level, 45 on the left cab. I can't for the life of me remember how to average these three results!



For kicks here's what happens when I put my chair back and head up between the mic and subs. (I'm at 5 ft, mic is at 4)


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This has me very curious, and I don't have time to test right now, but this graph is of the mic 46" inches in from the back wall in the center of the room, but look how different it is from today's measures at the same location. The ONE thing that was different was height. It was higher by 6". That and there were NO room treatments. Oh crap... I'm almost positive phase were both set at 0 too.

Oh well, still goes to show you (AND ME) what 45* of phase and/or 6" of height will do!



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Originally Posted by craig john View Post

Now we're on to something!!!

As expected, moving the measurement position turns nulls into peaks. This is how it's supposed to work! This is further evidence that the nulls are related to the room dimensions. If you were to play a 48 Hz tone, you could walk around your space and, literally, stick your head into and out of the peaks and nulls.

Going forward, here's what I would suggest: Take your measurements as "spatial averages" of the 2nd and 3rd seats plus the spot in between them. Measure at different listening distances and then place your seating at the point with the best "spatial average" of the 3 positions. If you want to go even further, take spatial averages of all 4 of your seats and the exact middle.

Now, I have a question for you... will there be a video display in this system? If so, where is it going to go? How big will it be? Will it be acoustically transparent?

Craig

Ummmm... a few beers and a lot of measuring equals need to re-read that spatial average thing in the morning. I'm so tired of measuring and using my brain tonight. Time to hang speakers. But, I've made notes and will continue with your suggestions to further perfect the LP.

To answer your question, Yes it's 95% home theater! Any music will not be critical listening, just pandora or iTunes to pass the time. An AT screen is all but ordered, Seymour XD. Size will be between 120-105". 16:9. It will be the last thing I buy. Once I get the system and room somewhat dialed I will hang a sheet and analyze screen size as well as where the screen frame will fit with my mains. I don't want to block any sound with a 1x3.

Why do you ask?

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eek.gifeek.gifeek.gif Thanks!!!

So stoked with these results behind the right chair!

And you even have room there to spread your legs out.

Oh, that's right, you're STANDING there, right?

biggrin.gif

 

Eager to see your end results.


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post #117 of 600 Old 07-07-2013, 02:36 PM - Thread Starter
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Now we're on to something!!!

As expected, moving the measurement position turns nulls into peaks. This is how it's supposed to work! This is further evidence that the nulls are related to the room dimensions. If you were to play a 48 Hz tone, you could walk around your space and, literally, stick your head into and out of the peaks and nulls.

Going forward, here's what I would suggest: Take your measurements as "spatial averages" of the 2nd and 3rd seats plus the spot in between them. Measure at different listening distances and then place your seating at the point with the best "spatial average" of the 3 positions. If you want to go even further, take spatial averages of all 4 of your seats and the exact middle.

Now, I have a question for you... will there be a video display in this system? If so, where is it going to go? How big will it be? Will it be acoustically transparent?

Craig

Sorry if this is a dumb question but what the heck is a spatial average and how do I do it? I Googled it but left more confused.

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Sorry if this is a dumb question but what the heck is a spatial average and how do I do it? I Googled it but left more confused.

That is the space between your ears times four, and then divided by the space from your eyes to the back of your head times three plus one. wink.gifbiggrin.gif

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post #119 of 600 Old 07-07-2013, 03:17 PM - Thread Starter
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That is the space between your ears times four, and then divided by the space from your eyes to the back of your head times three plus one. wink.gifbiggrin.gif


LOL

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post #120 of 600 Old 07-07-2013, 03:58 PM
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All SPL

Impulse Graph

The All SPL graph is an overlay graph that shows all measurements (SPL and/or Impedance) that have been made. It allows an average to be generated of all selected traces or arithmetic operations to be carried out on pairs of trace to generate a new trace.

The frequency range of the averaging result covers the region where the traces used overlap, for example if one trace was measured to 200Hz, another to 500Hz and a third to 1000Hz the average would range to 200Hz (to the lowest end frequency). Any of the traces which are selected when the Average The Responses button is pressed will be included in the averaging. New measurements (those made after the last average was generated) show new next to the trace value, whilst those included in the last average show avg.
http://www.hometheatershack.com/roomeq/wizardhelpv5/help_en-GB/html/graphpanel.html#top

A "spatial average" would be to take multiple measurements across a "space", (such as all 4 of your chairs), and then use the averaging function to average them.

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