A couple of years after my first failed attempt at making a tapped horn subwoofer, David McBean added tapped horn simulation capability to Hornresp.  Armed with this new software I decided it was time to try again.  I used a Tang Band 6.5 inch W6-1139SI.  First I measured the t/s speaker parameters using LIMP.  Then I spent a lot of time studying the few previous commercial and diy tapped horns that had been measured and finally I got  started playing with the tapped horn wizard.

 

 

 

 

At the time, I thought this undamped response would work out fine once liberally stuffed.  Even though the picture below says .5 pi, the picture above is shown simulated in 2 pi space at xmax with 130 watts applied.  Impressive SPL vs low frequency extension from this tapped horn.  As the measurement below shows, this is not a perfect design but as an inital educated guess it turned out all right.  I was planning on making a set of four of these tapped horns anyway, and if I do decide to complete the remaining three it would be easy enough to make them slightly different so their combined frequency response would be considerably flatter.

 

 

 

 

The next step is to take the Hornresp inputs (above) and convert them into tapped horn subwoofer plans (below).  Fortunately my buddy is an Autocad wiz and I was able to convince him to help fold it up as well.  Material thickness in this drawing is 5/8 inch and the internal width is 8 inches.  The driver tap position is marked with 3 small red dots, look close and you will see them.

 

 

 

 

Then I performed the unenviable task of building it.  I used some fibreglass to very lightly stuff the first half of the tapped horn.  It wasn't nearly enough, the large undamped peaks were clearly visible in my measurements.  Since it was already glued and screwed I was only able to add additional stuffing through the mouth.  I had to nearly fill the tapped horn from the mouth back to the driver to get the damped response you see below.

 

 

 

This measurement was taken using REW out in my driveway at about 10 meters distance.  I use my laptop as source and uncalibrated mic.  As you can see, fully stuffed this tapped horn rolls off around 20 hz, a bit lower than planned.  Unfortunately the stuffing did little to even out the big null around 80 hz.  This null is exacerbated by the room induced null created by standing waves between floor and ceiling in typical 8 foot high rooms.  I was hoping for smooth response up to almost 200 hz but unfortunately this big hole limits response to a 70 hz or so top end.

 

This tapped horn subwoofer is a joy to listen to, if anything a bit bass heavy down low in my current listening room.  Very clean bass even though the impulse response doesn't look ideal.  I'm sure I can do a much better job on my next tapped horn.  It's a bit tricky getting the full three octaves of potential response but it can be done.  Tapped horns are always going to have slightly spiky response though.  Even the commercial models manufacturer's measurements look very similar to the picture above.