# More about subwoofer placement



## Synthsayer (Dec 19, 2007)

Getting my MAD1259 & O Audio 500W BASH amp system properly placed has taken quite some time. If I turned it up really loud, I would get tons of bass but it didn't sound good at all because of *room mode problems* at approximately 45Hz and 65Hz.

The O Audio sub amp owner's manual contained a link to a site that helps one to determine the bad *ROOM MODES *in your listening area. *Room Mode / Standing Wave Calculator ©*

Another common problem encountered during subwoofer setup is *Boundary Cancellation*. This can suck the life out of any sub system. I have experimented exhaustively with this; mostly *not* by choice.

*Peavey Tech Notes* is the best site I have found related to *Boundary Cancellation*; *Peavey Tech Notes - Boundary Cancellation PDF format ©*

Or go to this *Peavey Tech Notes page of links*, scroll towards the bottome of the page to find:
*Boundary Cancellation - How to Eliminate Low Frequency Cancellation with Proper Woofer Placement © - PDF Format*​
This nice site from *Tim Padrick*, has a very handy and easy to understand chart explaining how you can *manipulate both boundary cancellation & room modes *to quickly find a very good starting point for getting your sub into the right spot. *Boundary Cancellation and Room Modes*

In the end I placed my sub where it cancels out the 45Hz room mode of almost 12db. This required placing the sub roughly 4.5 feet from nearest boundary/wall. I then used the parametric EQ on the sub amp to EQ down the more noticable/annoying 65HZ room mode created by the distance from the sub to the 8.5 foot high ceiling. It made all the difference in the world. The bass is now well defined and the annoying room modes that nearly rendered the system useless are gone.

Good luck. *This method of positioning your subwoofer can greatly improve the sound of your subwoofer system.* No kidding.

Have a great holiday.

Go Kentucky, beat Louisville!


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## Synthsayer (Dec 19, 2007)

Over the last few days I listened to my HT setup with the new location of my powered subwoofer system. I have to say this has made a vast improvement in the sub's performance. With the room modes toned down using placement and a little parametric EQ as mentioned in the previous posting, the lowest bass sounds are way more noticable. 

I haven't hooked up my measurement system yet, and not sure I will. It sounds so much better that there is no reason to test. What a relief!


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## nerk (Sep 3, 2010)

many thanks for the links, this is something i am looking into doing today. just picked up a boston acoustics PV800 for a really nice price (under 90$) in mint condition at a pawn shop. there was a TON of boston acoustic gear there but i only had eyes for this beauty.


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## Synthsayer (Dec 19, 2007)

You're very welcome.

Sounds like a great deal on the sub you bought. I hope the setup tips help.

Good luck with the setup and have a great day.


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## Synthsayer (Dec 19, 2007)

Another interesting tool to help with subwoofer setup is Jeff Bagby's "BAFFLE EDGE DIFFRACTION SIMULATOR".

***This runs in MS Excel 2003 - 2007 with Visual Basic Macros. 

BAFFLE EDGE DIFFRACTION SIMULATOR is a powerful tool for predicting subwoofer placement by calculating Room Boundary Reinforcement, Room Pressurization Gain, and combining that data to provide a useful graph of the combined Baffle Diffraction/Room Augmentation Sum. This can help to diagnose problematic room & subwoofer response and gives the user an _idea_ of low frequency behavior when a sub of a certain diameter is placed regarding distance from nearest boundary, distance from floor, & room longest dimension.

Forum readers using DIY speakers may be familiar with Baffle Step Attenuation from incorporating this theory in their designs.

Those forum readers NOT using DIY speakers can disregard the need for Baffle Step Attenuation and focus on the Boundary Reinforcement and Room Pressurization. Remember to toggle and select "POWER RESPONSE" at bottom right of Room Boundary Reinforcement graph.


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## Lucky7! (Jan 7, 2008)

Other worthwhile reads on sub/speaker placement are of course the Harman paper, Low-Frequency Optimization Using Multiple Subwoofers and Syn-Aud-Con's "How Boundaries Affect Loudspeakers".


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## Kenobi (Aug 11, 2010)

Thanks guys for all these resources. A lot of reading to do before the experiment.

Best regards,

Kenobi


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## Synthsayer (Dec 19, 2007)

A9X - Thanks for the great links. I have been looking for just this type of information. It is well worth the time to read these papers if you are setting up or tuning a subwoofer system in a room.

These are great papers that give in depth info on how low frequencies behave in closed, or open spaces

I thought the *Syn-Aud-Con paper by Pat Brown ©2008 *was very detailed and showed some very practical and useful response graphs. Thanks again for the link.

I thought the *HARMAN Low-Frequency Optimization Using Multiple Subwoofers* paper by TODD WELTI AND ALLAN DEVANTIER from J. Audio Eng. Soc., Vol. 54, No. 5, 2006 May ©2006* were also full of great info about; using multiple subwooofers, where they can be placed to optimize response, very useful graphs depicting room/subwoofer interaction.

These papers may take a few minutes to read, but IMO are indespensible to somebody setting up a home theater subwoofer as a professional installer or consumer.

Thanks again and have a great day


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## Lucky7! (Jan 7, 2008)

I'm glad you found them useful.

The Room Response Calculator is also a useful tool for visualising the effect of the room on FR due to speaker and listener position. Lots of other great design software there too.


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## Synthsayer (Dec 19, 2007)

Thanks again for another great link. I'll try using the Room Response Calculator right away.

Actually, my next post was going to be about the question of whether listener position room modes and dips ( frequency response ) could be predicted using the same methods as with subwoofer placement. It would seem that there might be peaks and nulls in that spot, too. One thing we all have experienced that I noticed in the Harman paper about multi-seating coverage and Sound Field Management is that even though one seat may sound good, what another listener may hear can be awful.

Thanks again and have a great weekend everybody


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## ojojunkie (Jun 23, 2010)

Thanks! nice reading, being not a tech person will take sometime to fully comprehend all the technicalities in the article..


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