Edgar Posted February 17, 2014 Share Posted February 17, 2014 An icy day in the Midwest. I'm stuck inside, thinking (dangerous). I got to wondering how close a vented box could come to a SPUD. So I started experimenting with Hornresp. I have a SPUD model that I obtained somewhere on the Internet. I'm not certain exactly how accurate it is, but, frankly, an inch of error here, an inch there, doesn't make a lot of difference in the response. I tried several different 8" woofers in the SPUD model, and found that the Ciare 8.50NDW produced the flattest response. (There may be other woofers that perform slightly better; I just don't have models for them.) That model is shown in the upper left of the attached graphic, with the frequency response at the upper middle and the diaphragm displacement at the upper right. Hornresp tells me that the SPUD internal volume is 296 liters. So let's build some 296 liter vented boxes. Well, 296 liters is enough volume to produce approximately a B4 response (4th-order Butterworth -- very desirable) with two Dayton TS400D-4 15" woofers. The Hornresp model for that is in the middle left of the graphic, the frequency response in the middle middle, and the diaphragm displacement in the middle right, in both cases with the SPUD in gray for comparison. Two-hundred ninety-six liters is also enough volume to produce approximately a B4 response with no less than six Dayton RSS315HO-4 12" woofers. The Hornresp model is in the lower left, with frequency response lower middle and diaphragm displacement lower right. I'll leave the interpretation to the reader. But I will add the Hornresp says that the low frequency, excursion-limited max SPL of the two Dayton versions is between 16 dB and 19 dB higher than for the SPUD. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted February 17, 2014 Share Posted February 17, 2014 Interesting, thanks for posting. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted February 18, 2014 Share Posted February 18, 2014 2-8" in a spud 2 high output 15" ts daytons in a ported and 6 dayton rss ho's in a ported have i got that right? from a cost standpoint, thats good news for the spud. did u try ANG = 2.0* pi? Quote Link to comment Share on other sites More sharing options...
ClaudeJ1 Posted February 19, 2014 Share Posted February 19, 2014 If you really want to have a high performance/low cost ratio, try the Kraken 212 on the DIY board. For twin JBL1214's at $80 each and 3 sheets of plywood, you can approach a $3,000 DTS-10 in performance below 15 Hz.. Quote Link to comment Share on other sites More sharing options...
Edgar Posted February 19, 2014 Author Share Posted February 19, 2014 (edited) 2-8" in a spud 2 high output 15" ts daytons in a ported and 6 dayton rss ho's in a ported have i got that right? from a cost standpoint, thats good news for the spud. did u try ANG = 2.0* pi? Yes, you have that right. But that is just a comparison of what can be done in the same volume as the SPUD. The other things that can be taken away from this are: 1. A single TS400D-4 in 1/2 the volume will still be competitive in frequency response and excursion. 2. A pair of RSS315HO-44 in 1/3 the volume will also be competitive in the same ways. 3. If you really want to use the full 296 liters, then you have many more options for enclosure shape with the vented boxes than with the SPUD. 4. It's easier to get a tapped horn to go below 20Hz than it is to get a vented box to go below 20Hz. (I had to experiment with a lot of woofers to find these examples.) 5. Since vented boxes tend to be much less finicky to build and tune than tapped horns, for systems that don't actually need to go below 20Hz the vented box may be a better option. 6. Vented boxes do not exhibit any of the high frequency "mess" that is characteristic of tapped horns, so vented boxes may be the better choice for use above 70Hz or so. A quick look at online prices puts the Ciare 8.50NDW at $135 each, the TS400D at $239 each, and the RSS315HO-44 at $156 each. So there are some definite price advantages to the SPUD with regard to drivers. As for the 2PI radiation angle, I did experiment a bit with that. The SPUD is somewhat less sensitive to the radiation angle than the vented box. That is to say, the cutoff frequency rises a bit more in the vented box than it does in the tapped horn, when the angle is increased from PI/2 to 2PI. But with the extra excursion capabilities of the larger drivers, EQ is an easy option. Overall it is not my intent to discourage anyone from building a tapped horn. But if you only need 20Hz or 25Hz, then there are other options that start to look better. EDIT: This does not address the sound quality issue. Personally, I like the sound quality of a tapped horn/transmission line/TQWP (all variations on the same theme). Just today I read on a forum somewhere that a person described the sound of a TH as "rumbly", as compared with the "woofy" sound of a vented box. That mirrors my own opinion, and I cannot think of a better way to describe it. Edited February 19, 2014 by Edgar Quote Link to comment Share on other sites More sharing options...
mustang guy Posted February 19, 2014 Share Posted February 19, 2014 I think TH sounds boomerish and vented subs are Smurphy. Quote Link to comment Share on other sites More sharing options...
DrWho Posted February 19, 2014 Share Posted February 19, 2014 I'd be interested if you could best the Othorn with a vented cabinet in the same volume....and you get a decade of usable response too. Quote Link to comment Share on other sites More sharing options...
Edgar Posted February 19, 2014 Author Share Posted February 19, 2014 I'd be interested if you could best the Othorn with a vented cabinet in the same volume....and you get a decade of usable response too. OTHORN is 419 liters. Quote Link to comment Share on other sites More sharing options...
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