DrWho Posted March 12, 2008 Share Posted March 12, 2008 DrWho, Does not seem as engineered in what ways? What would you do differently? Thanks, Robert Sorry I didn't get back sooner...I just spent a week of constant all-niters and then ended up in the ER on Monday... For what it's worth, I think there is an important distinction between overbuilt and well-engineered. Throwing a crap load of amp into a ton of drivers is a sure way to get a lot of bass, but I'd wager that there are little things that could be done to help refine things a bit. For example, the sheer size of the enclosure opens you up to all sorts of cabinet resonances within the sub's passband. You also could have gone with drivers that fire at each other with one of the cones inverted, which would dramatically reduce odd-order harmonics, not to mention cut down on the amount of cabinet rocking. The pressure distribution in the rear cabinet volume also isn't uniform at every frequency, so it makes sense to position the passives at pressure peaks so as to maximize their efficiency. It also doesn't hurt to tweak the tuning so that things are still well behaved when entering the non-linear region of operation (the lower you tune, the more dramatic this difference will be). I dunno, it just looks and is presented like a brute force approach...at the same time, it's real easy to be an "armchair engineer" and critique anything presented on the web - I hope I'm not outta line sharing some of my opinions. Quote Link to comment Share on other sites More sharing options...
Mr. RF62 Posted March 12, 2008 Share Posted March 12, 2008 I hope your okay Doc. Quote Link to comment Share on other sites More sharing options...
robertcharles Posted March 12, 2008 Share Posted March 12, 2008 First, thanks for the info. Next, there was significant time put into the design of these subs. The cabinets will be built using opposing forces which will result in minimal rocking and cabinet movement. I talked in length with many people reguarding this design and they were all for it. Kyle Keating, who worked at TC sounds says everything should be fantastic. Ilkka, the Finnish subwoofer tester is all for it. Dan, who helped design the whole rig has built a host of very impressive subwoofers. The drivers were tested and shown to be of the highest quality. The boxes are being built to serve one purpose, to fit where they are put in my home. We will see how they perfrom when all is said and done. I am seeing these guys first hand and let me say, everytime I see them, they look more impressive to me. If I can finish them to a high standard, I feel that they will be able to hold their own with any sub avaiable today. We will see. Also, it is easy to see the flaws in other's work, it is also easy to see the flaws in your own work, but sometimes you just have to go forward and finish a project to see the final outcome. Thanks, Robert Quote Link to comment Share on other sites More sharing options...
geoffstgermaine Posted March 13, 2008 Share Posted March 13, 2008 Sorry I didn't get back sooner...I just spent a week of constant all-niters and then ended up in the ER on Monday... For what it's worth, I think there is an important distinction between overbuilt and well-engineered. Throwing a crap load of amp into a ton of drivers is a sure way to get a lot of bass, but I'd wager that there are little things that could be done to help refine things a bit. For example, the sheer size of the enclosure opens you up to all sorts of cabinet resonances within the sub's passband. You also could have gone with drivers that fire at each other with one of the cones inverted, which would dramatically reduce odd-order harmonics, not to mention cut down on the amount of cabinet rocking. The pressure distribution in the rear cabinet volume also isn't uniform at every frequency, so it makes sense to position the passives at pressure peaks so as to maximize their efficiency. It also doesn't hurt to tweak the tuning so that things are still well behaved when entering the non-linear region of operation (the lower you tune, the more dramatic this difference will be). I dunno, it just looks and is presented like a brute force approach...at the same time, it's real easy to be an "armchair engineer" and critique anything presented on the web - I hope I'm not outta line sharing some of my opinions. Inverting the cones (which could still be done) would only have the effect of reducing odd-order harmonics. Cabinet rocking would not be affected since the cabinet is already set up with the active drivers and PRs in an opposed-firing setup. I'm not sure if you're referring to standing waves with the statement about the pressure not being uniform at every frequency, but in the pass-band of the PRs the wavelengths are in tens of feet (more than 50 feet for the tuning frequency) and so I can't see what effect trying to position the PRs at the "pressure peaks" would have. At such low frequencies the pressure should be fairly uniform. Where would you have placed the PRs? Perhaps you mean something else and if so could you expand on your point? Could you expand on what you mean by the non-linear region of operation and how tweaking the tuning frequency is going to affect this? Quote Link to comment Share on other sites More sharing options...
DrWho Posted March 13, 2008 Share Posted March 13, 2008 Pardon the crude drawing, but this is what I was trying to ellude to with the active driver configuration on the baffle (attached below). The idea isn't entirely my own, but I think I first saw the design posted by djk and then I've seen it posted in multiple places afterwards. Getting rid of odd-order harmonics is certainly no trivial matter at all - especially considering they are classically considered less musical than even order harmonics. Btw, does each passive have its own passive firing away from it? Or are the actives and passives opposite from each other? The actives and passives each have their own maximum excursions at different frequencies which means that opposed firing actives and passives don't cancel out their motion. As far as the pressure distribution inside the cabinet - I'm not referring to standing waves. I'm referring to the fact that sound takes time to propogate and that the intensity of that wave goes down as a function of distance. These are two things that the classical T/S model chooses to neglect, but it's very real. Ever notice that the efficiency of a PR is less at lower SPL's than at higher SPL's? [^o)] I must confess that I have not experimented with this behavior enough to have a feel for how to optimize things, but I've talked with subwoofer engineers that claim they are taking these things into account... I suppose technically you're always in a non-linear region of operation, but there is a definite point in every system where the non-linears start to grow fast. Klippel has done a great job documenting a lot of this behavior:http://www.klippel.de/pubs/papers.asp It's interesting to note that the LMS drivers have a lot of engineering trying to offset a lot of these things too... Also, you can't just change the mass on a PR without also altering its Q...the shape of the Q will have a direct impact on the active driver cone excursion, which in turn has a direct impact on the distortion - even if the frequency response is measuring the same... Quote Link to comment Share on other sites More sharing options...
geoffstgermaine Posted March 13, 2008 Share Posted March 13, 2008 The PRs are opposed from PRs and the active drivers from active drivers in Robert's design. I'd have to see calculations to be convinced that the fall off of pressure with distance within this cabinet was enough to be a significant worry. I'd be interested to see a subwoofer that supposedly took this into account. Most of the PR subwoofers I've seen are close to square boxes with PRs mounted on opposing faces. Quote Link to comment Share on other sites More sharing options...
robertcharles Posted August 17, 2008 Share Posted August 17, 2008 Here is an update. Currently, I am waiting on the granite top and base. I have acquired the grill cloth and I am getting ready to finish that particular aspect. Waiting on primer and paint to be delivered. Any thoughts? Thanks, Roberthttp://i228.photobucket.com/albums/ee292/robertcharles123/100_1470.jpg Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted August 17, 2008 Author Share Posted August 17, 2008 looks great Quote Link to comment Share on other sites More sharing options...
CAS Posted August 30, 2008 Share Posted August 30, 2008 Looks nice and sweet ,But home made subs never work the way they should in the end. Been there, done it several times.Thats why i just purchased the Gotham. Buy it ,and be done ! Or better yet buy 2 Heres the real monster ! http://asia.cnet.com/crave/2007/10/05/us-11-000-monster-subwoofer/ Hmmm. I don't think that's the case at all. At least not in my experience. Use some basic design techniques, some basic construction skills and the right equipment...you've got yourself a winner. To be honest if you apply those principle you'll have a better quality and more potent product than 90% of what's out there...at a lesser cost. 1 Quote Link to comment Share on other sites More sharing options...
TheEAR Posted September 1, 2008 Share Posted September 1, 2008 I have no choice but to agree with CAS here(no choice at all!!!). [] I have built simple subwoofers that outperform much more expensive commercial ones. The catch...you need to invest time into these projects. One thing the vast majority of DIY builders will never match is the custome electronics and cabinetry of a Gotham. All else can be matched and better... Take the AudioPulse LMS-Ultra this driver bests the JL variant of the W7 used in the Gotham or Fathom. But these are hard to find and cost more than the average joe can muster for a whole sub...I have now four LMS-Ultra 15's...he he he(cheap brag).Also take Acoupower's 15 or 18" monster and you also can build a one of a king ubber performer.After the proper cabinet is designed and constructed...you need the proper amp (Crwon iTech,MacroTech and QSC PowerLight)to power these...plus a proper PEQ. The results are OUTSTANDING. This of course I take as a given one has more tham basic understaning of acoustics. Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted September 1, 2008 Author Share Posted September 1, 2008 the jl 13w7 costs more than a lms Quote Link to comment Share on other sites More sharing options...
jwc Posted September 1, 2008 Share Posted September 1, 2008 So if you were to build a cabinet for say the Acoupower's 18", would you still go with a sealed box? Or even the Audiopulse in a sealed box? jc Quote Link to comment Share on other sites More sharing options...
DrWho Posted September 2, 2008 Share Posted September 2, 2008 So if you were to build a cabinet for say the Acoupower's 18", would you still go with a sealed box? Or even the Audiopulse in a sealed box? It all depends on your application and the goals you have in mind... Quote Link to comment Share on other sites More sharing options...
TheEAR Posted September 2, 2008 Share Posted September 2, 2008 13W7 costs more than a LMS... back into reality please. 13W7 does not retail for $1599 (LMS-Ultra 15"),the old pricing on the LMS is no longer in effect. The Acoupower 18 sells for $850 apiece.The 13W7 can be had at many places for under a grand. Try to find the LMS-Ultra for under a grand these days,good luck...only second hand. Having four I say...HA HA. Sealed ...ported Sealed will put more demand on the amp and driver,as the excursion will grow when you drop in frequency.Less efficient as no port or PR will add to the driver's displacement.With a ported you make sure you have the space to acomodate a cabinet large enough to let you tune near the frequency the extension can start falling. Acoupowers work great in sealed or will have blow your winsows output when working in a optimal tuned cabinet(where ported properly,not underported(restricted)). Quote Link to comment Share on other sites More sharing options...
Jay481985 Posted September 3, 2008 Author Share Posted September 3, 2008 I got my lms 5400 at 875 dollars shipped JL I asked was 1199 + Tax Quote Link to comment Share on other sites More sharing options...
Ricci Posted September 3, 2008 Share Posted September 3, 2008 Pshhhht! 1199 plus tax! I can get 13W7's all day long for under $600 shipped. Good luck even finding an LMS now, let alone one for less than a G shipped. Gotham is very nice, but not $11K nice. If it was $5.5K it would be reasonable. You can DIY something just as good looking and more powerful for less than 5.5K. For the full retail you can have something as nice or better than the G213 and a killer set of Klipsch mains. Quote Link to comment Share on other sites More sharing options...
TheEAR Posted September 3, 2008 Share Posted September 3, 2008 You will not get a LMS-5400 for $875 anymore,this is why they went belly up. I paid ~$1500 per LMS-Ultra...as price ..I do not give a damn if I have to have the best. [] And the quote you got on that 13W7...LOL I can get them for ~$700. $1199 is a ripoff. Quote Link to comment Share on other sites More sharing options...
darkside Posted September 3, 2008 Share Posted September 3, 2008 Ear, you don't give a *** because you have a steady, high income apparently. Those of us that don't, well, don't [:S]. But yeah. 1199 for a 13w7; it's stuff like that that has made me a true believer in Ebay. There's one on there, brand new BIN 579.95 plus 60 shipping...639.95, which is barely half of 1200. And you can always find one cheaper in good condition used, just like a car. Quote Link to comment Share on other sites More sharing options...
TheEAR Posted September 3, 2008 Share Posted September 3, 2008 The dont gibe a "d a m n" was about the price of the LMS-Ultra,the $875 is a ancient price people will never see them sold at. The LMS-Ultra will sell for over $1000 in great condition,my two spare LMS-Ultra I would only sell them for $2000 apiece,not a cent lower and I may need them later and regret my sale. The 13W7 can be had for under $700 ...I reapeat for under 700 little ones. Less than the low price on the LMS-Ultra. No question the LMS-Ultra is a superior product. Quote Link to comment Share on other sites More sharing options...
darkside Posted September 3, 2008 Share Posted September 3, 2008 Oops. My bad. I thought you were saying you don't give a *** about the price because you can afford it [:#]. But yes, the 13w7 is, in my opinion, still expensive as hell even at under 700, though you're paying a lot for the name like with, say, BMW. And this will be my last post on this as it seems we've successfully hijacked another thread [:S] Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.