What an absolutely fantastic thread and much kudos to
and others for giving us all the knowledge they derived experimenting with their BOSS builds.
I have come across the Hideaway Theater thread from the Crowson actuator thread and this is by far and away a more wallet friendly entry point into low frequency TR.
I have read through quite a bit of the thread and have confused myself with all the in depth analysis various bass enthusiasts like
and others have done. So I thought I would reach out to you for advice.
First a little background. I want to build a mini riser in our living room home cinema. My wife is very tolerant of my addiction but to keep her on side it should basically disappear as much as possible under our 4 seat sofa. The base of the sofa is 8' by 3' with plenty of space for the drivers. The sofa has six large wooden feet (1 in each corner and 1 middle front and 1 middle rear) that are 12" long by 6" wide and 2" high. So in terms of the build my thought process is as follows
Make the platform the same size as the base of the sofa. As it has been emphasised that the key factors for good results are the rigidity of the mini riser board and the quality of the isolators, my thought is to use two 3/4" sheets of plywood glued and screwed together to make the board as rigid as I can and have 4 drivers.
Now to the questions
1) In the drawing in post 29 is shown an enlarged drawing of where the sofa arm and the sofa foot rest on the 3/4" plywood. Then under the plywood is the isolator and the floor. The added height of the BOSS in the diagram is 3/4" + 1". In my case with the two sheets glued together the total height of riser plus isolator will be (3/4" x 2) + 1" =2.5".
At this point I have three options
a) Place existing sofa with feet onto riser platform with isos beneath. Overall height of sofa from floor will increase 2.5"
b) Remove 2" high feet from sofa and use the existing threaded screw holes where those feet attach to the sofa to rigidly screw the boss board to the sofa. Total increase of sofa height from original now only 1/2" - more WAF
However after reading post 2079 I wondering if this will compromise performance?
"3. Drivers mounted directly to the chairs/couch....BOSS experience will be about the same as 2 but not as much TR from the far field subs and nearfield subs since the BOSS platform surface area tends to be the smallest in this configuration."
c) Remove 2" high feet from sofa and place sofa onto boss board without securing the sofa and board together. Total increase of sofa height from original again 1/2" -again more WAF
2) Having looked at other builds subwoofer placement seems to vary from a central position to a more rearward position. Some of this will be due to the space available under seating but I seem to be seeing a trend toward rearward placement if possible. Is my assumption correct?
and his lovely build here
I am assuming the rearward position is to do with having the drivers under the trunk of the seated person rather than under the legs. Due to having plenty of room under the sofa I can put my drivers as far forward or back as you guys suggest as long as they remain under the sofa.
I also have room for four more drivers if I place the first row of drivers toward the rear of the panel with a second row in front of them so that there will be two drivers under each seat. Will I gain anything by adding four more? Or will I lose out by weakening the overall structure of the board, introducing more flexing, and so reducing the total TR produced by the BOSS?
3) In post 1741 are listed the speaker parameters to focus on for a BOSS device. I am in the UK and have access to the following JBL drivers
GT-X1200: Freq response 23Hz-450Hz, Mms 179, Xmax 12.1mm Best price currently £67.99
S2-1224 : Freq response 25Hz-175Hz, Mms 154, Xmax 10.25mm Best price currently £67.99
GT5-12: Freq response 27Hz-450Hz, Mms 223, Xmax 14.2mm Best price currently £49.99
Is the GT5-12 the better driver and the cheaper price is a bonus? Or is the slightly higher frequency response at the low end more of a disadvantage than the bigger Xmax and Mms?
Sorry for the long post and all the questions and thanks in advance for your help. Also if you have any more thoughts or suggestions for me I would appreciate them greatly.