Since I had the North Creek D25 tweeters and terminal cups sitting around as well as some salvageable MDF that was partially water damaged in my basement, I decided to do the only logical thing – build another speaker.
A quick search for loudspeaker projects revealed the Speakerbuilder.com PeeCreek project. This appeared to be a rather well known, easy to build project and inexpensive as well. Of course, I have great difficulty not to upgrade stuff, so the parts used in my build were of medium grade audiophile quality.
I won’t go too much into the basics of this project as they are well noted elswhere on the internet, but I would at least like to point out some of the finer details of my project for those who might like to build a pair as I have.
Building loudspeaker cabinets can be an excellent learning experience. This time I learned several important things:
I used the “glue & screw” or “two drills” method this time. While the construction of the basic cabinets went very quickly, it was very messy as the excess glue came out of all of the joints at the same time. I should have used plastic drop cloth, but I used newspaper which stuck to the cabinets while the glue cured.
Several details of my cabinet differ from the original Wayne J article:
The baffle cutouts were made on four ½” thick MDF panels and the panels were glued/laminated in the cabinet after the rest of the panels were assembled to keep them in perfect alignment. Personally, I don’t like cutting then laminating as I can never seem to get the edges perfectly straight, but this cabinet design lent itself well to this construction. IMO however, it’s always better to laminate panels before making any cuts at all.
The inside of the woofer cutout has a ½” roundover – this is to allow unimpeded air flow within the cabinet. This makes sense to me because the back of the cone is pushing as much air as the front of the cone and air tends not to flow smoothly around rough surfaces.
Two things went wrong with my cabinet construction that, at the risk of embarassment (but the gain of knowledge), I feel are worth mentioning:
Because I had some gorgeous curly maple veneer just sitting in the basement, I figured I’d finally have a use for it in this project. The veneer was rolled up for quite some time and never seemed to flatten out sufficiently. To try to get the veneer as flat as possible, I followed internet instructions (see above warning) to flatten the veneer using straight boards, clamps, kraft paper & glycerine mixed with water. I followed the instructions to the letter, yet the veneer still didn’t quite get flat. I decided to go ahead and veneer anyway using the “iron-on” method for raw veneer (again, see above warning). Suffice to say, this did not work at all for me as shown in the pictures. The veneer cracked like crazy and at this point I really wished I had used the “old fashioned” method of glue & pressure which had worked well for me in the past. It was very sad that I had to discard many square feet of already glued & bookmatched veneer. FWIW, I will ever more use paper backed veneer and FSV glue as it worked extremely well for the North Creeks.
To rectify the situation (the sides of the cabinets had dry glue and one side was quite shagged from removing the failed veneer) I used sandpaper, spackle & sealer to smooth the side of the cabinet that went wrong. Fortunately, I was able to execute an alternate plan for the cosmetics – I rounded all edges of the speaker cabinet and prepped it for the same color paint that I had painted the rears and bottoms.
The other thing that went wrong was that the countersink for the woofer was too large and there was a 1/8” gap around the woofer. I’m still not sure if this was a hole cutter, router, or measurement mistake, but it was something that absolutely had to be corrected. The woofer gap would probably contribute very little to the overall sound of the speaker, but it would just look terrible no matter how well the cabinet was finished. The solution was straightforward and simple – fill & re-drill. The edge was filled in with Plastic Wood Filler built up in four thin layers. Between each layer, the baffle was sanded to determine how much more filler was needed to fill the gap and to give the router a smooth surface to ride on. The countersink was rerouted with a slightly shallower rabbet. There is still a very small (less than 1/16”) gap around the woofer, but it’s not very noticable. I used this opportunity to fill in and smooth other parts of the cabinet prior to painting – I am rather pleased with the end result.
I went a little overboard on the crossover, but I wanted to be assured of good sound without spending too much or too little on the crossover components. I have learned a few things about crossovers from the North Creek Wiring Guide as well as helpful advice from experienced speaker builders and from messing with the crossovers of various speakers that I’ve owned in the past. I wanted to use the largest guage air-core inductors that I could use as I believe that this contributes to an open, dynamic sound. I also chose to use film capacitors throughout as I feel this contributes to clarity and speed. All these things add up to one big-ass crossover!
Inductors, caps (all film), resistors and eggcrate foam were all bought at Parts Express.
I could have tolerance matched all the crossover parts as I have access to an LCR meter, but I didn’t want to put too much effort into the XO as I may plan to make changes to the speaker in the future. Besides, this was supposed to be a budget project anyway. It always pays to match drivers though – these woofers were purchased from Meniscus Audio who will match your drivers for an extra $10.
As you can see from the picture, my XOs look signifigantly different than the designer’s XOs. While I’m certainly no crossover expert, I especially didn’t like the arrangement of the inductors at the Speakerbuilder site as I felt that they would have been too close to the woofer magnet. Basically, if you look through the core of an inductor and can see the core of another inductor, then there will be a magnetic flux coupling/interference between those inductors. I also wanted to connect the large inductor directly to the binding post to avoid using a wire. My goal was to use as few solder connections and as little wire as possible.
All parts were mounted on 6”x 9” pegboard and glued with hot melt glue. Inductors were strapped to the board with wire ties during and after gluing.
While these loudspeakers were still breaking in, I found the bass on these things to be mighty impressive. These speakers had a very easygoing sound with a receeded midrange and soft-ish treble. I did not consider these speakers reference grade, but they sounded far better than most ported consumer speakers that I had heard.
The last paragraph, if you'll note is completely past tense. Shortly after breaking in, I loaned these to an audiophile associate to not only get his opinion, but to gain a bit more room in the house for a little while. To my suprise, he liked them so much that he just had to have a pair! I just couldn't understand why he liked them so much (honestly, I didn't feel that they were complete - there was much tweaking to do), so I listened to them on his system and more specificly, in his room. Wow! they sounded much better in his small room than in my larger areas - the bass was still deep & firm, but the midrange and treble really came into balance in his room. Tonal balance and flat response from a loudspeaker is the top priority in my book; while these speakers did not sound very balanced in my rooms, there was just nothing to complain about in my friends system/room. Ah-ha!, another lesson learned...and another pair of speakers built & sold!
Okay...what next? Maybe similar drivers in a stuffed tapered quarter wave pipe, or maybe a sealed MTM, series XOs for sure...hmmm, so many chioces :)