mburgess Posted April 3, 2009 Share Posted April 3, 2009 Hi all, I am planning on doing a set of CornScalas and thought I would post the plans I came up with for review. Also, if they are of use to anyone, feel free to use them. I am going to construct them so the bass bin is separate from the mid/high end and I want the top part at ear level. I am using an apt-150 for tweeters and I will be making 1" tractrix horns (fs=300) mated to k-55s. Matt Quote Link to comment Share on other sites More sharing options...
mburgess Posted April 3, 2009 Author Share Posted April 3, 2009 And the top hat... Quote Link to comment Share on other sites More sharing options...
jwc Posted April 3, 2009 Share Posted April 3, 2009 Your measurements have the internal volume at 10687.5 sq in or 6.18 cu ft. Your internal depth is 18" and interanal height is 25 inches. That would be a new type config vs what most have done here. One thing to note is that if you put any bracing or any extra material inside that bass bin...besides the woofer....you might not have the volume "like" what is in a cornwall. jc Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted April 3, 2009 Share Posted April 3, 2009 I've noticed that the specifications for woofer internal volume can be very wide. Like at the Eminence website. Im using the Kappa Pro 15a 8 ohm woofers and my volume is approx 6 cu ft and it sounds real good. But according to Eminence anything from 1.9 to 6.5 is good. I thought that was interesting. http://www.eminence.com/proaudio_speaker_detail.asp?web_detail_link=KAPPAPRO-15A&speaker_size=15&SUB_CAT_ID=1 Quote Link to comment Share on other sites More sharing options...
mburgess Posted April 3, 2009 Author Share Posted April 3, 2009 Your measurements have the internal volume at 10687.5 sq in or 6.18 cu ft. Your internal depth is 18" and interanal height is 25 inches. That would be a new type config vs what most have done here. One thing to note is that if you put any bracing or any extra material inside that bass bin...besides the woofer....you might not have the volume "like" what is in a cornwall. jc Thanks for the input and good point about the bracing - I may bump the depth out to 19". These are still somewhat preliminary, and the point was to play around with ideas I had. Matt Quote Link to comment Share on other sites More sharing options...
mburgess Posted April 3, 2009 Author Share Posted April 3, 2009 I've noticed that the specifications for woofer internal volume can be very wide. Like at the Eminence website. Im using the Kappa Pro 15a 8 ohm woofers and my volume is approx 6 cu ft and it sounds real good. But according to Eminence anything from 1.9 to 6.5 is good. I thought that was interesting. http://www.eminence.com/proaudio_speaker_detail.asp?web_detail_link=KAPPAPRO-15A&speaker_size=15&SUB_CAT_ID=1 Very interesting. I found the "Download PDF Cabinet Design" link to be of particular interest. The graphs for each of the 3 box sizes show somewhat different characteristics. Matt Quote Link to comment Share on other sites More sharing options...
jwc Posted April 3, 2009 Share Posted April 3, 2009 My recs would be to definately keep the width as you have it and do whatever you want with the other dimensions. My Cornscala bass bin was..... interenal H x W x D 21.5 x 23.75 x 22.375 = 11425.23438 cubic inches 11425.23438 - 10641.51650144 = 783.71787856 cubic inches. So it was 11425 cu in before my bracing. Bracing displacement volume was 784 cu in. The end volume was similar to what you have now with no bracing. The cabinet was very rigid and sounded great. Are you considering other woofers besides a Crites or K33?? jc Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted April 3, 2009 Share Posted April 3, 2009 There is a thread here about the comparisons between the different woofers that included the Eminence woofer with graphs. Quote Link to comment Share on other sites More sharing options...
mburgess Posted April 3, 2009 Author Share Posted April 3, 2009 My recs would be to definately keep the width as you have it and do whatever you want with the other dimensions. My Cornscala bass bin was..... interenal H x W x D 21.5 x 23.75 x 22.375 = 11425.23438 cubic inches 11425.23438 - 10641.51650144 = 783.71787856 cubic inches. So it was 11425 cu in before my bracing. Bracing displacement volume was 784 cu in. The end volume was similar to what you have now with no bracing. The cabinet was very rigid and sounded great. Are you considering other woofers besides a Crites or K33?? jc I have not acquired the woofers I am going to use yet. My thought at the moment is the crites cast frame woofer, but I am certainly open to suggestions, especially where money might be saved ;-) Matt Quote Link to comment Share on other sites More sharing options...
jwc Posted April 3, 2009 Share Posted April 3, 2009 crites cast frame woofer That would be my first choice. Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted April 3, 2009 Share Posted April 3, 2009 I cannot seem to find that thread but there was a comparison between maybe 4 different woofers with freq. response plots too. One of the woofers was expensive in comparison to the others. A brand I hadn't seen before. Maybe I'll think of a few key words in the thread. I found this where "D-Man" had the K33 and the 15C in a pair of speakers. They may be the same woofer for all I know. "My buddy who built these is a bass player, and he was suitably impressed enough that he went back home and immediately started building himself a pair. We tried one cab with the Eminence Kappa 15C (4 Ohm) which I had sitting around and only one cabinet totally kicked tail. 30 watts was flabbergasting. These not only blow out matches, they blow the extinguished matchstick out of your hand! Real pant-flappers. I was amazed at how much air these can move. He also couln't believe how loud they were at 1/3 watt." Quote Link to comment Share on other sites More sharing options...
Guest " " Posted April 3, 2009 Share Posted April 3, 2009 There's a direct relationship to the vent size (exit area, lenth of the shelf, and distance from the end of the shelf to the rear wall) and the cab volume. If you deviate from standard volumes...then you will need to re-compute these variables....otherwise....the tuned frequency of the vent will change and it won't reinforce the lower end of the woofers performance range. Quote Link to comment Share on other sites More sharing options...
mburgess Posted April 3, 2009 Author Share Posted April 3, 2009 There's a direct relationship to the vent size (exit area, lenth of the shelf, and distance from the end of the shelf to the rear wall) and the cab volume. If you deviate from standard volumes...then you will need to re-compute these variables....otherwise....the tuned frequency of the vent will change and it won't reinforce the lower end of the woofers performance range. Thanks, speakerfritz, Do you happen to know of any good, free, calculators out there? I would like to keep the dimensions approx. as they are, and hopefully the ports can be adjusted to match. Matt Quote Link to comment Share on other sites More sharing options...
Marvel Posted April 3, 2009 Share Posted April 3, 2009 I found this where "D-Man" had the K33 and the 15C in a pair of speakers. They may be the same woofer for all I know. They aren't the same Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted April 3, 2009 Share Posted April 3, 2009 They aren't the same Interesting. Whats the difference? Quote Link to comment Share on other sites More sharing options...
Marvel Posted April 4, 2009 Share Posted April 4, 2009 They aren't the same Interesting. Whats the difference? You don't expect me to remember that far back do you? I just vaguely remember the thread, but they weren't the same speaker by a long shot. ...I'll see if I can find the info. DMAN was, how shall I say iy... a little controversial Bruce Quote Link to comment Share on other sites More sharing options...
Crossman Posted April 4, 2009 Share Posted April 4, 2009 There's a direct relationship to the vent size (exit area, lenth of the shelf, and distance from the end of the shelf to the rear wall) and the cab volume. What is the relationship? I have noticed in someone's pictures (can't remember who) that the shelf length was approximately half the distance of the cabinet depth. Also I think that I recall B Crites bass bin as being 24x24x24 with the port shelf being 4" high but I could be wrong. I thought that I was wrong once but I was mistaken. Crossman Quote Link to comment Share on other sites More sharing options...
mburgess Posted April 4, 2009 Author Share Posted April 4, 2009 I downloaded WinISD pro (had to use wine - I'm a Linux guy ;-) ) and interestingly it doesn't mention speaker depth at all. I would appreciate it if someone could explain the relationship. I would like to, if at all possible, keep the dimensions I have roughly the same and adjust the port dimensions to fit. Matt Quote Link to comment Share on other sites More sharing options...
Guest " " Posted April 4, 2009 Share Posted April 4, 2009 The cornwall uses a vent port, that is square, known as a slot type, and has a specifc lenth into the cabinet. Here is a calculator to drill one's mind thru the thinking process. since you know your volume you would use "Calculate Your Vent Length " which would provide data based on the targeted tuning frequency You need to select square port, vented, slot, and note the spot for the vent lenth. http://www.carstereo.com/help2/Articles.cfm?id=31 Quote Link to comment Share on other sites More sharing options...
mburgess Posted April 5, 2009 Author Share Posted April 5, 2009 Thanks guys. I think after digesting all of the great info posted, I think I will stick to the tried-and-true 24x24x24 internal dimension for the bass bin - it's not too different from what I had and bunches of people have had success with it. Why mess with a good thing, right? The port shelf I have seen for that configuration is 9" from the back of the motorboard with 50 sq. in. of port space. Does that sound right? Matt Quote Link to comment Share on other sites More sharing options...
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