DIY speaker enclosure, maybe TL?
I bought a mint condition used vintage Yamaha receiver a few months ago. The seller also gave me a pair of speakers that were built and sold by a local stereo dealer (three brothers that were in business for years but are now retired). They are a three way design without a port. The center plug of the woofer is rotted. The midrange driver looks a bit decayed. I am thinking of refinishing the cabinets and replacing drivers. Any suggestions before I buy drivers that I regret? Thanks |
"I have tried transmision lines MLTL Martin King design and ported etc. Sealed cabinet is always better IMHO, I put a big chunk of plywood covering the ports of Martin Kings design for Lowther DX3 and things got much better, I also changed the Lowther for Fostex 207, I get better balance and less detail. Find a good quality woofer that will go really low and build from that, go for a 3 way! Martin Kings is a good design but I always hear some reverb in the bass." Jsadurni, If you heard reverb..something was very wrong my friend. I have never heard reverb in my MLTLs. Who built your MLTLs? Some times it's best to leave the building to the designers. Sounds like you were pushing the drivers past their limits. |
Tom, In my opinion the C92-6 is the only Accuton unit I see on Madisound's website that's a reasonably good candidate for transmission line loading. I have built roughly 50 different transmission line designs, though many were experimental only. Here is what I learned: Go by the physical line length, measured down the center of the line. Ignore anything you read about the speed of sound slowing down in a fibrous tangle. Bass extension to the 1/4 wavelength frequency is not easy to get. Maximum reinforcement will be at the 1/2 wavelength frequency. Up at 1 wavelength, we have a problem: The output from the end of the line is out-of-phase, so it will cancel the frontwave energy and you'll get a notch in the frequency response. Now notches are not nearly as objectionable as peaks, so one option is to try to ignore it. But once you know it's there, you'll probably hear it as a leanness in the midbass. By increasing the stuffing in the line, you attenuate the backwave energy that emerges 180 degrees out-of-phase at the 1 wavelength frequency. But, you are also attenuating the reinforcing backwave energy that would have helped out at lower frequencies. So, it's a trade-off - in exchange for smoother midbass, you give up deep bass. In my opinion the solution is to start out with too much deep bass to begin with. So I'd suggest high Qts woofers for transmission lines, so that when you overstuff the line to smooth out the midbass dip you're also bringing the deep bass back down to where it sounds balanced. I'd go for a Qts of .6 to .9, which is higher than any of the Accutons but the C92-6 comes the closest. Finally, you can smooth things a bit more by locating the woofer 1/3 of the way down the line instead of at the very end of the line. Or, you can use two woofers with the midpoint between them 1/3 of the way down the line. You get maximum power handling and reinforcement if the woofer is at the far end of the line, so once again it's a tradeoff between smoothness and bass extension. In my commercial efforts I don't use transmisson lines because the woofers that have the qualities I place high priority on do not work very well in transmission lines. The woofers I like are better suited to vented enclosures, so that's what I use. Best of luck to you, Duke |
I have tried transmision lines MLTL Martin King design and ported etc. Sealed cabinet is always better IMHO, I put a big chunk of plywood covering the ports of Martin Kings design for Lowther DX3 and things got much better, I also changed the Lowther for Fostex 207, I get better balance and less detail. Find a good quality woofer that will go really low and build from that, go for a 3 way! Martin Kings is a good design but I always hear some reverb in the bass. |
Speaker building is very exciting and rewarding (IMO). Please don't misunderstand me however, if I say that designing can be a bit tricky for an "entry level" builder. TL is particularly difficult and until King & other came up with modelling (very recently) it was a hapless task. You absolutely must see Mr Linkwitz' site Info and links here Interesting stuff here. Advanced stuff by Kreskovski here And, another "must read" from Mr Ludwig Don;t be daunted by the looks of this site, just go right in -- it's readable! Good luck |
Thanks to everyone--I'll check out the recommended websites. I won't know which Accuton drivers until I have a slightly better idea of what's possible. I'd like to avoid a subwoofer, which suggests to me a 7" mid-bass unit rather than a 5" or 6" one--unless I use two mid-basses along with, say, their 1" tweeter. John Risch's writings have been the most useful to me so far, but they're marked "obsolete--historical interest only" in the website they appear in. Discouraging! |
I have built many ported designs but never a TL. There are boat loads of links out there on the topic. The best speaker book I have found for the beginner is speaker buidling 201 by ray Alden. I would start with that and read the Vance Dickinson books after. Tony Gee has a great web site with projects and the forums on Parts express web site and madisound have oodles of info as well. http://www.humblehomemadehifi.com/ |
You could also contact Bob Brines. He maybe able to steer you in the right direction. I'm a fan of TLs..they have a certain type of bass that I haven't experienced from other designs. Here's Bob's site Brines Acoustics. |
