FR/WR125S in MAPD?

I was reading the issues concerning the FR125S in MLTL and BR enclosures and was thinking to myself, I wonder if these drivers would be suitable for a MAPD enclosure like North Creek uses for one of their kits. So I pulled up the NCM page and found the whitepaper for MAPD. George states that the best driver for this enclosure has a Qts around .6 and a small VAS... well the WR125 has a Qts of .64 and a VAS of 5.8L. Sounds perfect!

Using a small aperiodic first chamber 2L (.07 ft3) that ports to a 5.8L (.2 ft3) via a tuneable aperiotic vent should do it by their ways.

Has anyone tried this yet? If so, how did it work out?

I have a pair of empty baffleless cabs that I built long ago for a pair of MB-OW1s that I never bought the parts for. They're about .37 ft3, I'm gonna try to jerry rig together a MAPD enclosure out of these to bring to DIY Orlando on Saturday, no idea if I'll be able to do it in time.

I'll let ya'll know how they turn out. Peace.
I'll have the cabinets done this weekend. With gas prices where they are and DIY Orlando postponed, I'll have plenty of time. In fact, the cabs and crossovers are done - I just need to make up some baffles and then work on tuning. I'll be comparing them to the standard 7L ported cabs and 7L sealed cabs. The sealed were too weak in the bass department and the ported have caused the woofers to go into a bit of a coniption a couple of times with some deep bass. I'm a bit sceptical that these will provide what I'm looking for, but who'll be a fun experiment. What I'm hoping is that the highish Q in the aperiodic compartment will provide a natural response rise for BSC. And if the bass isn't satisfactory, perhaps I will try porting the second airspace which should prove nearly impossible with anything other than ear.

The results are in!

I have no doubts that the MAPD configuration has been around for 30 years or so and I'm not sure that's what George was implying.

Regardless, I played around with the tuning a bit and listened to these enclosures for the better part of the week. Regardless of the aperiodic vent tuning, I was unhappy with the bass. The midrange was perhaps a bit more focused but I found that they did not provide nearly enough bass for listening without the subwoofer. Since these are going to be for my sister in a small apartment and no sub for the time being, I've decided to stick with the 7L ported alignment which I think works very nice with these. If she had more room, I would give TL a try, but these need to be tiny.

For those that are curious, I have these WR125s paired up with a HiVi RT1L round planar tweeter which does a very nice job. They use 2nd order electrical filters for approximate 4th order LR slopes around 3500Hz. The picture below is the nearly final network... in my room (which is a bit lively BTW) I found the tweeter to be a touch hot, so I changed the 5.2 ohm resistor to 6 ohms which seems to have done a fantastic job. I had noticed the brightness mostly on TV audio, not so much on music.

I plan to have them measured at DIY Orlando in late October to see how closely they compare to SW's model. All I know now is that they sound absolutely fantastic...worlds better than the original network which had the WR running full range with the tweeter coming in around 8500Hz.


Very nice work, and great looking design! If it weren't for the cost and the ugly face plate on that tweeter, I would probably build it myself. As is the dx19 option is a bit more appealing.

About the MAPD loading - can you expand on your thoughts posted here about it? I planning on building a 'reference' fullrange using the fr125, and am having a hard time choosing between MAPD and a double chamber reflex arrangement. My system will be crossed at 120hz, 3rd order to stereo servo-subs, but I still worry about the maximum output of these drivers in a sealed or aperiodic arrangement. Plus as you alluded to, the hump created by the BR alignments gives a bit of warmth that lessens the need for a BSC network. Can you comment on how you think the MAPD version sounded relative to just sealed, and the vented box as far as the midrange goes?