| 22 May 2011 | MEASUREMENTS | LOU'S HOME PAGE |
 3/4" Baltic Birch |
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This project was generated by my "green" (er...cheap) side. Xavier had built 4 of these boxes for another project. During that project he lost a couple of unobtanium drivers. So we had four of these boxes already built. I had to use them! Those of you who've been through my site know I'm a huge fan of the Peerless Nomex drivers. The 81375 has been on the Parts Express buyout page for a bit. It's a bit unusual in that it's actually useable in a sealed box at reasonably loud levels. Because of the baffle space available, I needed a smaller diameter tweeter that could hit 2000 if needed. I went back to a tried and true workhorse, the Dayton ND28 I used in the C-Killa. The boxes are 3/4 Baltic, with no addtional bracing. Measurements were taken with ground plane methods. Crossover Design After taking measurements and getting everything loaded and acoustic centers lined up, it became apparent this wasn't going to be a super simple crossover. With the tweeter placed so close to the box top, and the corresponding woofer peak at 5K, some shaping of the curves was required. For those of you who have palpitations when buying crossover parts, take a beta blocker. The tweeter circuit needed an RLC notch filter to tame some of the edge diffraction from the high tweeter placement. The split padding enabled a bit better control of the final SPL curve. |
The woofer has a gently rising response. So trying to target an appropriate value for the big inductor took some trial and error. I tried 1.0, 1.5, 2.0 mH versions. Based on the prototypes, I thought the 2.0 gave the best balance of bass and midrange. The L/C components helped with phase and dropped the 5k peak down quite a bit.
Listening Impressions
After building the pair Xavier and I listened to them for an afternoon. The final product is well worth the effort. Sealed box bass sounds so natural and balanced. While the sims suggest F3 = 60 Hz, the PeeDei sound much fuller than the specs indicate. The ND-28 doesn't have quite the ultimate sparkle of the Vifa I used in the Veepers it is emminently capable and "listenable" without fatigue. Overall these are very well balanced, image beautifully, and are capable of handling just about any genre and mastering quality we threw at them. They don't get down to the bottom end of synth bass, but do benefit more from the shallow rolloff and room reenforcement. It's hard to say what the baffle step is on these, I'd guess maybe 4 db with sensitivity in the 84-85 db range.
Side by side with the Veepers, I'd be hard pressed to pick a winner. They are "different", the Veepers are a bit more forward and revealing, the PeeDei's are smoother, a bit warmer, and less "picky".
