Using RTA to position subs/mains - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 80 Old 05-23-09, 03:25 PM Thread Starter
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Using RTA to position subs/mains

Hey Guys,
If this isnt in the right area please let me know...
I have decided to start over with my setup.
Step one,i want to make sure ive got sub(s)in the best location for my room to get the best response.
Is using Rta in Rew my best bet for this?Put sub in lp and move the mic around to find smoothest response?then swap positions?
i have the HSU vtf mk3 ho and the MBM12.how do you do this with 2 subs?
Can i also us the Rta to get the mains in the best position.Toe in,distance apart,distance from wall etc...for the best soundstage?
Can someone please clue me in on the rta setup.ive looked through online help files,but dont see what i need,i did see a post from Brucek from 3/7/2009 on the subject(.RTA 1/24 octave.pink pn.fft 65536.average=2.window=rectangular.no bars.y axis=dbfs with scale -70 to 0)
Any thoughts?im i going about all this correctly?
Dean
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post #2 of 80 Old 05-23-09, 06:16 PM
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Re: Using RTA to position subs/mains

Quote:
Is using Rta in Rew my best bet for this?Put sub in lp and move the mic around to find smoothest response?then swap positions?
Yep.

Quote:
have the HSU vtf mk3 ho and the MBM12.how do you do this with 2 subs?
A lot of trial and error if you aren't planning on co-locating them.

Quote:
Can i also us the Rta to get the mains in the best position.Toe in,distance apart,distance from wall etc...for the best soundstage?
You can give it a shot, but again the problem with two mains will make it difficult. The RTA is certainly useful at the listening position to adjust the subs phase control when you have the sub and mains playing to obtain the smoothest crossover region.

Quote:
Can someone please clue me in on the rta setup.ive looked through online help files
Follow the info below on using the RTA:

To use the RTA feature of REW, you must first setup the levels as if you were about to make a standard response measurement.

This involves running the Check Levels routine for the mic at the listening position to 75dB and the Calibrate routine. You can even run a measure to have a reference.

Then, select the Spectrum tab in REW and setup the controls as shown in the picture below.

Then, select the REW Generator and select Pink PN and start the signal using the play button.

Press the Red record button on the Spectrum page.

You can monitor your Input Level on the Spectrum page in the bottom left hand corner.

If it reads clip at any time (because you're moving the mic around when using the RTA), then simply turn down the REW input level a bit.

Below shows a response measure I took (that gets transferred to the RTA graph), and the black line is the RTA itself. Now I'm ready to move the mic around and watch the black line change.




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post #3 of 80 Old 05-23-09, 06:28 PM
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Re: Using RTA to position subs/mains

Quote:
i have the HSU vtf mk3 ho and the MBM12.how do you do this with 2 subs?
No different, since the two function to cover the entire low end: put them both at the listening position for testing, then put them both in the location with best response.

Quote:
Can i also us the Rta to get the mains in the best position.Toe in,distance apart,distance from wall etc...for the best soundstage?
Not sure there's a definitive answer for this - others may want to chime in with their thoughts. My thinking is that REW won't do anything to help determine the best soundstage, since it's a mono signal. That's something you'll just have to do by ear.

As far as determining the best position from walls, etc. REW can help there. Smooth your RTA reading to 1/3 octave (hopefully you can do that with the RTA? I've never used it full range) and look for the larger peaks or dips in response below 500 Hz or so (which is about the frequency that the room really starts to influence things). See if re-positioning can minimizing the peaks and dips, but not at the expense of placement for the best soundstage.

Regards,
Wayne



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post #4 of 80 Old 05-23-09, 08:08 PM
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Re: Using RTA to position subs/mains

Hey Dean,

We have not heard from you in awhile. Maybe post a full range graph of your current set-up and list some of things you are not happy with. Wayne and brucek are great at reading the graphs and making suggestions for improvement. Another option you may want to start researching is sound treatment panels. I have noticed an actual improvement in my current set-up with just a few diy panels.
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post #5 of 80 Old 05-26-09, 09:17 AM Thread Starter
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Re: Using RTA to position subs/mains

I will try to get graphs up.
Its not that my setup doesnt sound good,it does.I just want more than good!!!
I still feel like im lacking that "room filling"low end,ive got descent bass,but no "pressure"
I can cut the HO off and there is really no audible difference whether its off or on.seems like the mbm does all the heavy lifting.
I did (for some reason)gut my mains and noticed that 2 screws on each woofer was pulled through.The woofers werent "sealed"to the cabinet.i fixed this and do notice a great deal of improvement in "clarity"now i want to start over and make sure im getting all i can from subs,location,setup etc...
I do have panels in the first reflection points and a few on the back wall.
I had considered adding another Ho but after speaking with Pete at HSU,he stated i should have plenty of sub for my size room?
I will try to get graphs up in a day or two.
Thanks for all the help.
Dean
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post #6 of 80 Old 05-26-09, 09:33 AM
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Re: Using RTA to position subs/mains

Quote:
jdeanmc wrote: View Post
I still feel like im lacking that "room filling"low end,ive got descent bass,but no "pressure"
I can cut the HO off and there is really no audible difference whether its off or on.seems like the mbm does all the heavy lifting.
Hey Dean,

Can you post a layout and give us more details on your room. "Pressure" is going to be very difficult unless you have a "sealed" room. Mine opens to other areas of the house. No matter how many drivers I add, I will never pressurize my space.
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post #7 of 80 Old 05-26-09, 09:49 AM Thread Starter
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Re: Using RTA to position subs/mains

This would be the latest room layout i have on my computer however,things have changed.The Ho is now on the right wall almost below the first reflection panel.I have also moved and added panels.I now have 2 on each side wall.
The room is a basement room that does close off from upstairs.
Maybe trying to "pressurize"my room was a bad choice of words.I actually just feel the low end is still a little weak.maybe i need a "steeper" house curve?
I do feel like a problem is the "blend"between the mains and the subs.Ie.i set up the subs with rew and get "wall rattling"low end then after i add mains and actually watch a movie there is no "wall rattling"low end.same for music,i can crank the sub level(in the avr) from 0 db to 6.0 db and dont notice much difference.
Its like when i watch a movie or listen to music at normal level,the low-end disappears.like the mains overpower the subs??
This is what im trying to improve on.
Dean
Attached Thumbnails
Using RTA to position subs/mains-ht-room-2.jpg  

Using RTA to position subs/mains-ht-room-001.jpg  

Using RTA to position subs/mains-ht-room-002.jpg  

Using RTA to position subs/mains-ht-room-003.jpg  


Last edited by jdeanmc; 05-26-09 at 09:54 AM. Reason: add pics
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post #8 of 80 Old 05-26-09, 10:05 AM
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Re: Using RTA to position subs/mains

Quote:
jdeanmc wrote: View Post
Its like when i watch a movie or listen to music at normal level,the low-end disappears.like the mains overpower the subs??
This is what im trying to improve on.
Dean
Gotcha. We will have to wait and see your graphs. I am sure Wayne and brucek will be a big help then. I would just read Wayne's house curve post again and try his suggestion of playing something like 30Hz. and comparing it to something near your crossover point (like 90 or 100Hz.) and see if they "sound" like the same volume. That should help with your house curve.
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post #9 of 80 Old 05-27-09, 12:26 AM Thread Starter
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Re: Using RTA to position subs/mains

o.k here is the mess im dealing with..
i set the subs only,check levels ,set target levels,have filters at ...
21 hz gain -16 bw 14
30.85 hz gain -6 bw 8
52.16 hz gain -12 bw 11
looked pretty good i thought.i have to set the avr volume to -18.5 to get to the proper level(at -18.5 with the mains added will run you outta the room,if not the house!!!)
then when i add the mains,set target level,check levels,i have to set the avr volume to -32
next is with the sub level maxed out
what am i missing?
makes since that when i set sub levels properly,then add mains and have to drop avr level so much here lies my problem.
i have got much better results than this before but the problem is the same.mains overpower the subs.
HELP.......
Dean
Attached Thumbnails
Using RTA to position subs/mains-may-26-subs-only.jpg  

Using RTA to position subs/mains-may-26-full-range-1.jpg  

Using RTA to position subs/mains-may-26-sub-level-maxed-out.jpg  

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post #10 of 80 Old 05-27-09, 03:15 AM
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Re: Using RTA to position subs/mains

the dip between 80 Hz & 90 Hz doesn't look right. It's not evident in the sub only graph?
Have you tried inverting the phase of the subs?

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