Room EQ Wizard study

Having done some IB designs for the Venom 15inch drivers, my need for bass was awakened once more...

To evaluate potential locations for an IB installation, I downloaded the Room EQ Wizard from Home Theater Shack. Note - You will need to become a member (free) before you can access the downloads

The software allows a frequency sweep to be sent to the sub whilst monitoring the response via a microphone. I used the microphone built into the Radio Shack SPL meter that I've been using for ages. By putting the sub in the listening position and moving the mic to potential subwoofer locations, the effect of room nodes can be seen.

The software also knows about several different equalisers such as the Behringer Feedback destroyer (BFD). It can auto-model the effects of filters and show the optimised response. The filter settings can then be uploaded to the BFD via your MIDI port.

This page is an example of how Room EQ Wizard can be used to make informed choices about subwoofer location


I get on well with my neighbors, and was concerned that the traditional above-ceiling or below-floor locations would require a lot of soundproofing to be viable. This just left adjacent rooms as potential IB sites, as shown below.

Location A would be the most convenient, whilst Locations B and C may have potential phase problems.

Original room layout
Drawing of listening room

The following graph shows the sub at Location A at the side of the room.
The huge dip around 50hz is the result of a room node activated across the room from side to side.

Graph of frequency response

I had read that the height of the microphone can change the reading.
Hoping that this might account for the hole, I repeated the test with four different microphone heights.

As can be seen, the results do change, but that hole is still there! This would suggest that Location A is unsuitable for a subwoofer.

Graph of frequency response at various heights

Next we have Locations B and C

Graph of frequency resonse for different subwoofer locations

The two positions vary, but the average response is encouraging, showing only minor dips and peaks.
It seems that Locations B and C produce a better result than that obtained at Location A

The new seating position is a result of rearranging the room by 180 degrees as shown in this drawing

New room layout
Drawing of new room layout

This arrangement puts the mains next to Locations B and C thus solving the integration problem.


The next graph shows the response at the new seating position.
Again, both sub locations were tested, and the average response is also shown.

Graph of response at new listening position

A pair of subs mounted at Locations B and C will produce far better results than what could be achieved at Location A.
The backwave will be contained in an adjacent room 3.9m wide * 3.9, same height, for a volume of around 48 m^3.

The IB has now been built - here's what was actually measured after installation
The flatter response is a result of moving to an EP2500 amp which doesn't have the limitations of the Jaycar unit used above.
Green is a nearfield measurement from within one of the manifolds
Red is the original seating position.
Blue is the new position after the room was rearranged. The low-end lift provided by room gain can be seen here.
Either position can be successfully tamed with the BFD.

Graph comparing frequency resonses at different locations
/room_eq_wizard_study.htm last modified: 31 August 2019
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