[lesmor]

Hi Folks
This is my first post so as usual be gentle
I have read extensively about room acoustics and room tratments and really appreciated the effect the room could be having on my home theater but the more I read the more confused and frustrated I get.

I have read loads on Subwoofer placement but am non the wiser where to position mine before doing any EQ.

Ive looked at buying the "XTZ Room Analyzer Package " but wonder if this is a false economy if I end up buying a SVS AS-EQ1 SubEQ

Of course there ia also the free REW software, brilliant graphs but how does an idiot like me analyse and understand them

If it shows a hump / dip does it also show where in the room that is? how do you treat it? reposition your sub? adjust something on your AVR ?
Because REW is not the same as a SVS AS-EQ1 SubEQ which I believe is left in line how do you adjust the freq reponse.
By now you should realise I am stupid and need to either give up or get some back to basics help which I havn't so far found searching around on REW
My dedicated room is an awkward 20ft X 17ft + a 8ft 7"X 31.5" Alcove , the room is 8' High
My System is a Panasonic AE-3000 , Denon 2500 BT Transport, Yahama Z7 AVR, M&K S-150 L/C/R, M&K SS-150 Surrounds , Polk Ls/FX Rear Back and a M&K MX-350 Sub.
Can anyone point me in the right direction?
Thanks in advance

 

[Wayne A. Pflughaupt]

Can anyone point me in the right direction?

First of all, why get the XTZ package? It does basically the same thing as REW, and REW is free. Okay, not totally free, as you have to buy at the very least a compatible sound card (assuming the one your computer has isn’t) and an SPL meter (if you don't already have one). Still, it’s far cheaper than XTZ.

XTZ does appear that it may be easier to set up and operate than REW, so if you’re technically challenged with computer stuff, it might be worthwhile for you. However, the problem most people seem to have getting REW going is choosing sound cards that aren’t compatible with their operating systems.

I have read loads on Subwoofer placement but am non the wiser where to position mine before doing any EQ.

The frequency response graphs REW generates can help with that. Basically, you can situate the subwoofer at your listening location and take response readings with the measurement mic at potential subwoofer locations. The one that gets the best response reading is the best location for the sub. From that point, equalization can be performed, and response readings will show the results of equalizing.

Of course there ia also the free REW software, brilliant graphs but how does an idiot like me analyse and understand them

We are here to help people understand the graphs. Or at least let them know they’re headed in the right direction.

If it shows a hump / dip does it also show where in the room that is? how do you treat it? reposition your sub? adjust something on your AVR ?

Repositioning usually gets the best results. There is only so much equalization or treatment can do to compensate for a bad sub location.

Because REW is not the same as a SVS AS-EQ1 SubEQ which I believe is left in line how do you adjust the freq reponse.

The SVS equalizer does room evaluation and equalization automatically. Other equalizers require manual adjustments, using frequency response plots as a guide.

By now you should realise I am stupid

Eh, don’t be so hard on yourself. No one is an expert at everything. I don’t know a blessed thing about designing microchips, for instance. I’m sure you’re an expert at something that I don’t know anything about. :T

Regards,
Wayne

 

[lesmor]

First of all, why get the XTZ package? It does basically the same thing as REW, and REW is free. Okay, not totally free, as you have to buy at the very least a compatible sound card (assuming the one tour computer has isn’t) and an SPL meter (if you don't already have one). Still, it’s far cheaper than XTZ.

XTZ does appear that it may be easier to set up and operate than REW, so if you’re technically challenged with computer stuff, it might be worthwhile for you. However, the problem most people seem to have getting REW going is choosing sound cards that aren’t compatible with their operating systems.


The frequency response graphs REW generates can help with that. Basically, you can situate the sub woofer at your listening location and take response readings with the measurement mic at potential sub woofer locations. The one that gets the best response reading is the best location for the sub. From that point, equalisation can be performed, and response readings will show the results of equalizing.


We are here to help people understand the graphs. Or at least let them know they’re headed in the right direction.


Repositioning usually gets the best results. There is only so much equalization or treatment can do to compensate for a bad sub location.


The SVS equalizer does room evaluation and equalization automatically. Other equalizers require manual adjustments, using frequency response plots as a guide.


Eh, don’t be so hard on yourself. No one is an expert at everything. I don’t know a blessed thing about designing microchips, for instance. I’m sure you’re an expert at something that I don’t know anything about. :T

Regards,
Wayne

Thanks for the quick response Wayne and confirming some of my concerns especially XTZ v REW ,
While researching all products come into the radar it is sometimes not obvious that some things that flag up may be a few years old and superseded by something more up to date.

I will try your suggestion of putting the Sub at my listening position and using REW at possible Sub locations , that makes sense to me.

As for adjusting any anomalies , I take it this would have to be done manually inside the AVR using the Yamaha Z7 YPAO , now thats frightening

I suppose the answer would be to get a SVS Sub equalizer , by then the Sub position should at least be in the ballpark

 

[glaufman]

Another thing to consider (not to confuse you) is that the location of that listening position is just as important as the sub location. Sometimes options are limited due to aesthetics and WAF. Also, even if you get the SVS EQ, you may find the desire to use REW to measure before and after, just for bragging rights!
One thing you could do is post a sketch of your room for placement suggestions.

 

[Tufelhundin]

New guy here and Greg is right on, I have dual PBU's in a 2800 cft room and I use the ASEQ due to having duals and I love it, but I do use the REW along with an SPL/UCA202 just to see what it shows. I enjoy using REW alot but I found that after I got the ASEQ dealing with my duals became less of a heartache. Maybe one day I'll get more than 5 post so I can post my graphs and ask some questions concerning them

 

[glaufman]

Looks like you just got there!

 

[lesmor]

Another thing to consider (not to confuse you) is that the location of that listening position is just as important as the sub location. Sometimes options are limited due to aesthetics and WAF. Also, even if you get the SVS EQ, you may find the desire to use REW to measure before and after, just for bragging rights!
One thing you could do is post a sketch of your room for placement suggestions.

Hi
Thanks for the reply , I was/am hoping to use REW to optimise the listening position as well ,as I am aware that by accident you could have your position in a null ( Any suggestions as to how to avoid this before running REW appreciated )

Dont think I can post a sketch yet , not enough posts
Regards
Andy

 

[glaufman]

Sorry for the delayed reply...
Best way to avoid the deepest null is to avoid the direct center of the room. If the room is "regular" 38% off the front or back walls is often a very good spot.

 

[Siamize]

Hi
Thanks for the reply , I was/am hoping to use REW to optimise the listening position as well ,as I am aware that by accident you could have your position in a null ( Any suggestions as to how to avoid this before running REW appreciated )

Dont think I can post a sketch yet , not enough posts
Regards
Andy

It seems that you aren't alone ... many people don't know/can't find how to set up a room. I recommend first that you have a read of the thread

http://www.hometheatershack.com/forums/rew-forum/12661-target-curve-new-discovery-4.html

There's been a good bit of information there.

After reading all that I've been testing my room. My biggest mistake I must admit was that I was only testing at one location. I'd read that taking averages from like 4 locations produced the same results basically as at one. I followed that advice and wondered why my results changed each day of the week. Answer ... enviromental factors. See:

http://siamize.vpscustomer.com/sound/Enviromental Effects on the Speed of Sound.pdf

For even more details see: http://siamize.vpscustomer.com/sound/atmos sound absorbsion.pdf

So from there I tested in a range of listening locations which seems representative. If you only ever listen from one location I guess you only need that location but unless it's at a studio mixing desk, I think that you'll have more than one location. From experience I've found that this removed all the ups & downs that occur due to nodal points. When you think about it, the wavelength of 1kHz is about 300mm or 1 foot, so every 300mm each way you are likely to experience an interferance and a construction node of varing degree depending on how much reflection you have in your room. In short, you will have sound going everywhere in your room in all directions so you need to take that into account when testing and setting up your system.




Also as to the response that you "want"/"need", I've found that the Modern X Curve as describe in the following page is pretty good:

http://siamize.vpscustomer.com/sound/the_mythical_x_curve.pdf

For a bit more of a background see:
http://siamize.vpscustomer.com/sound/Dolby_The X-Curve__SMPTE Journal.pdf
and
http://siamize.vpscustomer.com/sound/Article-Xcurve.pdf

 

[Siamize]

Also see
http://siamize.vpscustomer.com/sound/StdHouseSoundResponse.html

 

[lesmor]

Hi guys
Thanks for all your replies which will take a minute to digest
the 38% off front /back wall is interesting ,I take it that is the seat position ,so on a 20ft long room that equates to 7'6"
the reason I ask is.
I have been reading an artical by George Cardas , (rules wont allow me to post the link)
who gives a formula for speaker/ listener placement ,it looked promising but when set up on a 20ft long room you end up with the front of the speakers at 7'6" from the front wall , then your seat is at 7'6" from speaker fronts which only leaves 5'0 of room left behind the listener, the speaker position to me looks to be too much in the centre of the room , is anyone familiar with or used this formula, or has any comments on it?
Thanks again appreciated

 

[laser188139]

I think that is two sides of the same idea for avoiding a position that is a simple fraction of the overall distance. As you recognized, moving the seat that distance from the back wall and moving the speakers that distance from the front wall does not leave much space and does not make much sense. You could try one or the other as a starting point. Not many of us have the space to leave the couch at the wall and move the speakers 38% from the front wall.

The nice thing about REW is that it is easier to move the mic and take spectrum or sweep measures than move the chair or the speakers.

 

[Siamize]

I have been reading an artical by George Cardas ...

http://siamize.vpscustomer.com/sound/roomsetup.pdf

when set up on a 20ft long room you end up with the front of the speakers at 7'6" from the front wall , then your seat is at 7'6" from speaker fronts which only leaves 5'0 of room left behind the listener, the speaker position to me looks to be too much in the centre of the room , is anyone familiar with or used this formula

I'm guessing that your room is kinda setup like so (sorry about the metric units) ...

It does look somewhat like in the centre of the room.

I would have thought that the room height would have had more of an effect than the distance from the speaker wall as such as most of the sound is projected forwards.

The suggested setups are mostly to try and deal with nodal points of low freq sounds. But as I said before, you usually listen from more than one position anyway, so it's all a bit of give and take.

 

[lesmor]

I'm guessing that your room is kinda setup like so (sorry about the metric units) ...

It does look somewhat like in the centre of the room.

I would have thought that the room height would have had more of an effect than the distance from the speaker wall as such as most of the sound is projected forwards.

The suggested setups are mostly to try and deal with nodal points of low freq sounds. But as I said before, you usually listen from more than one position anyway, so it's all a bit of give and take.

Many thanks again
laser188139 You are correct, when setting it up in this way it just doesn't look right , the diagrams on the Cardas Site do not seem to be to scale so do not show how bad it is in reality.
This of course should not be taken as a criticism of the theory regarding node points, as if this gives the best sound then so be it.
Also would suggest it lends itself More to 2 channel stereo than home theater

Nice sketch siamize what did you use to create it, as I may now have enough posts to send one of my room
which had previously been requested
Regards
Andy

 

[Siamize]

Nice sketch siamize what did you use to create it.
Andy

Thanks .... AutoCad ... seeing I'm a civil engineer I have access to such drawing packages & the ability to use them to produce a reasonable sketch.


I found this little bit of research (not just theoretical waffle but also real testing) into the analysis of room sizes, speaker locations & listening locations interesting. Particularly the last sections.

http://www.silcom.com/~aludwig/Room_acoustics.html

Horrible/Optimum Rooms - The response also changes a lot when the listening point is moved two feet in any direction.
From testing my room I couldn't agree any stronger. I found it interesting when I read in some article how the movement of a speaker by a few inches could make a huge difference. I believe it does just as much as so does moving the listener a few inches. My point being ... whoever sits that still fullstop.


Another bit I found interesting was this in the last section.

Don't take a speaker manufacturer's claim of ±1 dB frequency response too seriously either.
So you're going to have to have a graphic equalizer (or similar) at hand if you are to have an even response no matter what room you have. Therefore you can adjust it for whatever frequencies reverberate too much / not enough in whatever room you are in. Having said that, the location & positon of your speakers will determine how even the response will be over your target listening area.



I also found this little setup simple ... the first method of the Golden Rule has been mentioned prior in this post the the second seems a little more flexible.

http://siamize.vpscustomer.com/sound/Speaker_Placement_Simple.pdf

 

[lesmor]

Hi Guys
Back again
Many thanks to all who have responded ,very good feedback whick I have looked at and taken onboard
My room upgrade is near complete , and hopefully will be able to use REW in the next week.

I have just checked my meter and have some questions as to its suitability if you dont mind.

1.The leaflet says it is a Techcessories Sound level meter ,it was sold by Tandy ,although it says Radio Shack on the actual meter, there is no model number ( Cat.No 33-2050 ) bought in 1995 ,so which calibration file should I use?

2. The leaflet says the frequency response is flat from 32 to 10000 Hz , is that what is required for REW?

Regards
Andy

 

[Wayne A. Pflughaupt]

Hi lesmor,

The meter's rated "frequency response" is of no consequence. You'll find a calibration file for the 33-2050 meter on our downloads page. It's what you'll want to use if you're using the meter for your measurements. If you're using another mic for measuring, and the meter for SPL only, then no calibration file is needed.

Regards,
Wayne

 

[lesmor]

Many Thanks Wayne for the clarification
Looking forward to my first attempt with REW , will probably need some assistance to interperate the graphs so will post when I have some

 

[lesmor]

Hi Guys
Finally got REW set up ( I Think ) after having problems with my sound card ( see different thread )
One thing is still not clear is , when doing measurements , sub only at the moment , using the right channel , should you still have the left channel looped back to the sound card like you do when calibrating the sound card ?
Many thanks to all who have helped me so far on this and my other thread :clap:

 

[Wayne A. Pflughaupt]

should you still have the left channel looped back to the sound card like you do when calibrating the sound card ?

No reason to do that...

Regards,
Wayne