DrWho Posted January 24, 2006 Share Posted January 24, 2006 Oh I forgot to mention, how about since DrWho is adamant about 12 inch drivers, to use acoustic elegence's av12 that is now available for 199? Well for a more apples to apples comparison...try modelling two 12" titanics versus a single 15" titanic. You get about the same SPL and lower extension in the same sized cabinet with about the same power requirements too. Two AES AV12's in a 5 cubic foot enclosure would outperform the Titanic 15". Same F3 and 1dB more output. (But you're spending twice as much on the drivers). One AV12 would go in a 2.5 cubic foot enclosure and would have 6dB less output. But with such a small cabinet you would be forced to go with PR's. Btw, a port doesn't need to reside entirely in the subwoofer enclosure....you can have "smoke stacks" that extend out and beyond. Depending on your room you might be able to hide such a thing - in which case there is nothing wrong with such an approach. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 24, 2006 Share Posted January 24, 2006 obviously we both have too much time on our hands as were posting post after post. oh well. How is Michael Hurd doing? He said he had to take time off from the forum. your temperature effect gives me an idea. Did anyone ever actively tried to cool a subwoofer? I know like many fans, the motor actually moves air through the coil to keep it somewhat cool. What if someone did a watercooled approach like cpu's? and drag the lines outside the box where there can be an active cooling system or so forth. I remember bose once claiming liquid cooled tweeters. I know different size and bad speaker company but, no one ever tried did they? Also I have my master subwoofer using the same two tumult 15d2 in a different enclosure. DrWho, try modeling two tumult 15d2 in a 16 cubic feet enclosure, I was thinking 24x24x60 using the height theory and Kyle Richardson's Everest design but bigger and six stryke 18 inch 2500 gram passive radiators instead of 4. I believe from what I can remember a f3 of 17 hertz, pretty much flat +- 1 db from 17-200 hertz. Able to reach 123 db anechoic in that range too. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 24, 2006 Share Posted January 24, 2006 Btw, a port doesn't need to reside entirely in the subwoofer enclosure....you can have "smoke stacks" that extend out and beyond. Depending on your room you might be able to hide such a thing - in which case there is nothing wrong with such an approach. I know I know and been told that many times but my brain and eyes would not like to see a mini industrial factory in my own room, I live in New Jersey which is notorious for smokestack buildings along the nj turnpike or garden state parkway..... smokestack does not equal acceptable in my eyes and practically every subwoofer that is mass marketed. Heck SVS tubes get enough heat for being a mini waterheater Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 24, 2006 Share Posted January 24, 2006 You only need 2 18" PR's per driver. So two tumults in a 16 cubic foot cabinet requires 4 PR's and you can get 123dB with an F3 of 18.5Hz or 120dB with an F3 of 14Hz after EQ. Mike and I were just talking about cooling subwoofers tonite...apparently some ppl have tried fluid cooling too. Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 24, 2006 Share Posted January 24, 2006 I know I know and been told that many times but my brain and eyes would not like to see a mini industrial factory in my own room, I live in New Jersey which is notorious for smokestack buildings along the nj turnpike or garden state parkway..... smokestack does not equal acceptable in my eyes and practically every subwoofer that is mass marketed. Heck SVS tubes get enough heat for being a mini waterheater But if you have curtains or the subwoofer near a couch you can send the "smokestack" behind where it's no lonver visible. It's just nice to know that option is there - I've only seen it used in one situation and it was out in the open and very ugly looking, lol. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 24, 2006 Share Posted January 24, 2006 Which too me I believe is very impressive with just two speakers and a not soo insanely huge box. Edit: I forgot to add that I forgot exactly what but the added two pr did lower the response or such. I have to model both of them tommarrow and my desktop with the winisd is off but my roommate is sleeping. 19 inch crt is very bright at night.... I am on my laptop with the monitor on lowest setting. As with cooling I am not sure exactly where to actively cool? The magnets? the motor itself? the voicecoil? Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 24, 2006 Share Posted January 24, 2006 I know I know and been told that many times but my brain and eyes would not like to see a mini industrial factory in my own room, I live in New Jersey which is notorious for smokestack buildings along the nj turnpike or garden state parkway..... smokestack does not equal acceptable in my eyes and practically every subwoofer that is mass marketed. Heck SVS tubes get enough heat for being a mini waterheater But if you have curtains or the subwoofer near a couch you can send the "smokestack" behind where it's no lonver visible. It's just nice to know that option is there - I've only seen it used in one situation and it was out in the open and very ugly looking, lol. The only semi smokestack subwoofer that I liked was that ultra low hitting subwoofer by that rather famous engineer. I believe the subwoofer could hit 130 db using a 12 inch driver. That was the system that took up about one square foot but was 12 feet high. Though its semi hideable.... Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 24, 2006 Share Posted January 24, 2006 I think you're talking about the Danley DTS or something tapped horn subwoofer....it uses the rear wave of the driver to correct for what would otherwise be a very jagged response from having a LF horn whose mouth was too small. Basically two horns where their responses added up to an end flat response - way cool design. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 24, 2006 Share Posted January 24, 2006 yes its the danley dts. Can you elaborate more on the principle? Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 24, 2006 Share Posted January 24, 2006 I think I get it after looking at the picture. BTW sorry zealot for turning your thread into a drwho/me discussion of subwoofers but I hope you are jotting notes of different ideas. Basically what I see from the picture is two ports that are horn shaped internally? and that one port is for the front and one port is for the back?. A more complex 6th order bandpass system in very basic concept? Quote Link to comment Share on other sites More sharing options...
Remotia Posted January 24, 2006 Share Posted January 24, 2006 expect great things from this driver. http://www.tcsounds.com/Images/LM_news.pdf<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> Its not offically out, but Eclipse is already adopting the technology and Im damn sure SVS will change at least their Ultra woofers very soon.With the new voice coil the new driver is able to increase the SPL by about 6+ dB while maintaining the same THD - yes, very impresssive. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 24, 2006 Share Posted January 24, 2006 You only need 2 18" PR's per driver. So two tumults in a 16 cubic foot cabinet requires 4 PR's and you can get 123dB with an F3 of 18.5Hz or 120dB with an F3 of 14Hz after EQ. Mike and I were just talking about cooling subwoofers tonite...apparently some ppl have tried fluid cooling too. I tend to like the linear graph as shown below with 6 pr instead of 4. It does not hit as low but the f3 is now pushed 3 hertz down and is flatter. Although it would cost 300 more dollars for two more passive radiators. Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 24, 2006 Share Posted January 24, 2006 6 PR's cost a lot more than 4....and you can achieve any tuning point you want as long as you use the right passives. The only reason to use more than one PR is because it reduces the amount of cone excursion needed for the same SPL (due to the increase in surface area). Sure, multiple PR's affect the tuning point too, but there are better ways to achieve that. You don't need any more than dual 18's per 15" active because they will have no problems displacing enough air (even with a very low 14Hz tuning). Btw, the QMS for the 3.36 Fs 18" PR is 84.53, not 92 http://yellow.mynethost.com/~bv126368/shop/catalog/product_info.php?cPath=24&products_id=39&osCsid=34fbf0b9f3d5374f3003edbc95b8cf27 And here is an alternative 18" PR depending on your intended tuning point: http://yellow.mynethost.com/~bv126368/shop/catalog/product_info.php?cPath=24&products_id=38&osCsid=34fbf0b9f3d5374f3003edbc95b8cf27 With EQ (2nd order peaking highpass filteer) I'm looking at an F3 and Fb of 14Hz with the 4PR design (2PR per driver). Voice coil temp rise doesn't hurt the response much at all and you can get a clean 119dB in the process. Without EQ I seem to be getting the same plot as your purple one with only 2PR's per driver (so 4 total). Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 24, 2006 Share Posted January 24, 2006 oh I got the QMS at kyle's website here I prefer to have as flat a subwoofer trying to not actively using eq. I think as a diyer you are able to manipulate the enclosure to your specs and eq should be the last thing considered and the enclosure should try to be as flat and low on it's own Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 24, 2006 Share Posted January 24, 2006 I prefer to have as flat a subwoofer trying to not actively using eq. I think as a diyer you are able to manipulate the enclosure to your specs and eq should be the last thing considered and the enclosure should try to be as flat and low on it's own DIY'ers like "dB," Danley, and Tom Nousainne (one of these days I'll learn how to spell their names, lol) would entirely disagree with that statement. When chatting online they say one of their pet peaves with the DIY world is their lack of understanding of the system as a whole. Sadly I'm also included in that group of the DIY world that isn't aware of the entire system, but at least I understand where I am and know where I need to learn...now to find someone willing to reveal all the secrets [] Anyways, the use of filters does a lot of things....it lowers distortion, it controls cone excursion, it can compensate for large signal nonlinearities, it allows for deeper extension in the same cabinet without sacrificing SPL, etc etc....the model we see in winISD is merely the small signal behavior of the driver. There is a lot more at play here - mechanical compressions, thermal compressions, the temperature of the voice coil changes the electric properties of the motor, etc etc... For example (and keep in mind this is just the tip of the iceberg of what I've learned so far)....the peaking 2nd order high pass filter was designed to take advantage of the fact that the cone excursion of the active driver is much lower at the tuning point of the system. And then it also behaves as a high pass filter which prevents lower frequencies which would totally throw the driver out of the box. Look on your models and observe the cone excursion behavior below the tuning point....it goes through the roof and lands the driver on the moon. It is extremely dangerous to operate a subwoofer near it's peak at frequencies above the tuning point because all it'd take is one low note to destroy your system. Usually we're not listening at levels to cause instant failure, but it's still a bad design flaw. To see for yourself, model a subwoofer to be as flat as possible (using the technique I described with the dayton). Now instead of adding EQ to model the amplifier and all that, add a 2nd order high pass at the tuning frequency with 3dB of gain (so around 24Hz?) Now lower the tuning point until you get back to a flat response. You have just extended the F3 point down about half an octave AND you will notice better control on the cone excursion. Readjust your power levels to get the excursion back to normal and then notice that you've sacrificed maybe 2dB of output. Different drivers aren't as excursion limited and in their case you don't sacrifice anything. To take it a step further....notice how the voice coil temperature rise affects mostly the excursion peak above the tuning point...and results in a boost at those frequencies. If we implemented a filter of some kind that brought those frequencies down as the power levels increased, it would both increase power handling and help to maintain a flat response. It will also increase the low frequency extension at the same time...provided your enclosure was tuned properly to anticipate this. How often do you get to hear that compression increases the volume? lol Well I have to go to class now, but I would love to talk more about this subject...I'm definetly not an expert but at least I've been pointed in the right direction by the true experts. Btw, are you on any messenging programs? It'd probably be a lot more productive to talk outside the forum - unless of course everyone else is finding this interesting....we're totally way off topic by now though [] Anyways, the end conclusion is that there are absolutely no downsides to using EQ - it can improve the response of every system...even if you start off from the beginning with no sacrifices on the cabinet design. You might need a slightly more powerful amplifier, but that's not a huge deal. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 24, 2006 Share Posted January 24, 2006 heh zealot125 must be like god I wanted help and these people are psychos..... MSN or AIM Jay481985@hotmail.com Jay481985 AIM Also for the eq and the cabinet design etc, it's like a racecar, some start from the engine (speaker) and make the chasis (enclosure) or some start with the chasis and make the engine as a derivative of what the chasis can deliver.... no one principle idea is better just different. Just like how subwoofers are seal, vented, passive, 4th order, 6th order, horned, etc etc.... DrWho how is you cad: autocad or solidworks? I used both and have some experience with cam. We should buy a CNC router [6] imagine what kinda speakers we could design! I heard aluminum is great! Just a tibit, honda spent over 200 million dollars on R&D on oval pistons for F1 or Indy or Cart I forgot but it really got nowhere (hence no oval pistons) but I bet they learned alot. Quote Link to comment Share on other sites More sharing options...
Zealot125 Posted January 24, 2006 Author Share Posted January 24, 2006 Guys, this thread has turned out to be a fantastic wealth of knowledge - and some of the most fun reading that I have done in a week! Thanks a million for your dedication to accurate subwoofer construction. Only one little problem. I know we modeled the FR with that parametric EQ at 20 hz with a Q of 2 +3 dB, but the parametric eq on the sub only allows a Q between .1 and 1. So, I changed the Q to 1 and the FR seemed to improve even more. Is there something else I need to change or is this right? EDIT with a gain of 4 dB the FR improves even further, and with a 20 x 1.5 inch 25 inch long port, port air velocity is still about 28 m/s. Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 24, 2006 Share Posted January 24, 2006 My autocad or any 3D rendering ability sucks hardcore...I just haven't gotten through that steep learning curve yet (and I'm trying to use free programs). So I just use MS word and scale things down and manually construct different views using a little bit of math. As far as EQ goes...just keep an eye out on the cone excursion. The wider the Q, the less honed in you get on the tuning point (where you have extra cone excursion available). Sounds like I wasn't doing my homework completely...though there is some ambiguity with their description of the EQ section (because they have their description of Q backwards in their PDF). Also, as you increase the EQ keep an eye out on the apparent amplifier load. You have to make sure the apparent load doesn't exceed the capabilities of the amp or the thermal limits of the driver. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted January 24, 2006 Share Posted January 24, 2006 Also remember as most amps start to distort/clip bad as you near max amplification. What wattage were you at Zealot125 with the 28.8 m/s reading? was that near or at max thermal wattage of either the amp or speaker? DrWho, autocad is the defacto standard and you should really really learn it. I believe I have some pdf books on it. QTC of 2!!! wow ummm I doubt its .2 as that means that it would not drop off until like 1 hertz.... 2.0 QTC must have some crazy drop off rates. BTW thanks zealot for your kind words. im me if you need any help or want me to make some autocad drawings for you. Quote Link to comment Share on other sites More sharing options...
Zealot125 Posted January 24, 2006 Author Share Posted January 24, 2006 will do buddy, but i gotta install trillian first, but its late and I have some differential equations to solve for homework, so that is a project for another day. Quote Link to comment Share on other sites More sharing options...
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