D-MAN Posted June 16, 2006 Share Posted June 16, 2006 Wayne Parham of Pi speakers has got a opposed dual 12" driver sub horn. Here's the link. CNC looks like the way to go. I wish I could find a CNC shop around here! http://audioroundtable.com/PiSpeakers/messages/19853.html Dana Quote Link to comment Share on other sites More sharing options...
soundbound Posted June 16, 2006 Share Posted June 16, 2006 Wow.... He did a great job on that sub. A nice job on the photos of construction to. It was a lot of work building that monster sub horn! I bet it sounds great. I wonder how long it took him from start to finish? You know your sub is big when you need a huge handle and wheels. I like the Pi speakes. I bet they all sound nice. Thank you for the link. Quote Link to comment Share on other sites More sharing options...
jorjen Posted June 17, 2006 Share Posted June 17, 2006 Dana, I know this may be a silly question, but have you checked ALL the cabinet shops in your area? I thought that in the small town we live in there was no way that anyone would have a CNC Router. Well, I was wrong. The last shop I called(the one that I thought would never have one)had one. I can get from my house to his shop in under five minutes, go figure. After hitting his place for the first time, I realized he had the best equipped shop of the bunch. I would kill for a place like that. Larry, the owner, is cool as can be. In fact now, he does'nt even charge me for some of the things I need. He does his design work using AlphaCam. Adds the tooling in the CNC computer and starts cuttin'. I am trying to learn CAD as time permits so that I can take him a design on memory stick, have him add the tooling and roll. Very cool stuff. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted June 17, 2006 Share Posted June 17, 2006 which cad program? Solidworks is becoming popular but Autocad is the defacto Quote Link to comment Share on other sites More sharing options...
djk Posted June 17, 2006 Share Posted June 17, 2006 I had a shop that makes lighted signs make me 18 pcs of a front baffle that had three cut-outs in them. I was charged $150 total. Quote Link to comment Share on other sites More sharing options...
djk Posted June 17, 2006 Share Posted June 17, 2006 Posted by djk ( M ) on May 16, 2003 at 17:26:18 In Reply to: Subwoofer configurations posted by Wayne Parham on May 16, 2003 at 02:49:27: The reductions in 2nd harmonic distortion from PP mounting on a flat baffle are well known, the non-linearities are equal and opposite and thus the 2nd harmonic is canceled. Because of the driver spacing it only happens in the bottom octaves. The cheaper the driver, the bigger the improvement. I have measured as much as a 20dB change. By mounting in a plenum several things change. The spacing becomes much tighter so the cancellation will work at higher frequencies, and a cavity is formed. The cavity does several things, in no particular order: The size, especially the depth, acts like a low pass filter. This can reduce 3rd harmonic distortion products near the top end of the passband, the effect is small, but audible. The cavity sizes I use have to be crossed in the 150hz~250hz region. It gives a slope of roughly 12dB/oct that must be taken into consideration in the design of the crossover. There is a small peak about two octaves above this point, ~800hz on many that I have done. By varying the Q of the 12dB/oct lowpass filter a LR4 I can get a LR4 transfer function. This filter also reduces the out-of-band peak to -30dB or better. There is also a big reduction in FMD, on the order of 6dB. The air mass at the exit of the plenum seems to act like a point source with no doppler, the cones are moving back-and-forth sideways rather than towards-and-away from you. At first glance this would seem to eliminate the FMD, in practice the reduction is on the order of 4dB~10dB depending on the frequencies. I mounted a pair of drivers in another cabinet in a face-to-face, push-push mode. The box became very 'thick' sounding and had a broad peak centered at 160hz, just like the EV MTL4. In room the response of the push-pull was 6dB smoother in the 100hz~200hz octave. Being compared side-by-side with the Klipschorn and Cornwall was interesting. At first the push-pull sounded 'funny'. Couldn't put my finger on it. Went back to the push-push cabinet. The push-push cabinet had that 'hi-fi' sound, similar to the Cornwall, but a bit 'thicker'. Klipschorn, much cleaner sounding. Back to the push-pull. The reason the push-pull sounded 'funny' was the total lack of distortion. Much less than the Klipschorn. I have not built a basshorn since. I still use horns, but only above 150hz. There are some drivers that are not suitble for home hi-fi, mainly those with small magnet vents that can make 'chuffing' sounds when up close. If enough interest, I can discuss other practical points related to construction and use. In Reply to: Re: PPSL posted by djk on May 18, 2003 at 02:38:51: Hi Dennis! I've been thinking about this configuration since you brought it up, and it seems to me that it might reduce second harmonics whether they are caused by non-linearities in the suspension or the magnetic structure. Pretty cool idea, really, and I'm surprised it isn't more commonly used on systems that have multiple woofers. I never gave it much thought before now, because none of my stuff uses more than one woofer. But it does seem like a good configuration for dual woofer designs whether they be baffle loaded, plenium loaded or horn loaded. Please do post more references if you know of any. I'd like to see more quantified data, if there is any that's available. Looks to me like you've found a good thing here. Wayne Quote Link to comment Share on other sites More sharing options...
jorjen Posted June 17, 2006 Share Posted June 17, 2006 Jay, I am demoing AutoCad 2007 and have talked with a guy from Autodesk a couple times. If things go well and I like it, I will probably buy 2007 LT. I do not really need 3D. But on the other hand if I had it, you never know. Not sure yet what the difference in price is, but either way they are not cheap. I am also looking into the Alphacam that my woodshop guy uses. Alphacam has multiple versions which are pretty industry specific. Consequently, the one for cabinet and woodworking shops may be quicker and less cumbersome for what I/we would be using it for. We shall see. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted June 17, 2006 Share Posted June 17, 2006 Autocad is what I personally know and can help you.... Geez I am old I remember the last version is autocad 2003...... [:$] Also if you need help getting an older copy......... pm me To be honest though I remember most cam and Alphacam should be crosscompatible with autocad. There might be a few errors transfering it over but all the same it takes a couple minutes to fix. Quote Link to comment Share on other sites More sharing options...
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