Quote: "...Oh, you can hear the difference easily enough "
Oh, no I can't. When I was 15 I made boxes that did all the work - flex, jiggle, emit alien flatulence. Now I build speakers where there are only one or two places sound comes from - the driver and the port. That is, sound that I can hear.
Oh, no I can't. When I was 15 I made boxes that did all the work - flex, jiggle, emit alien flatulence. Now I build speakers where there are only one or two places sound comes from - the driver and the port. That is, sound that I can hear.
Thanks a lot for the replies 🙂
I've very roughly drawn what I think is what Scottmoose specified, I expect i'm way off the mark though
. The response down to mid 20's is good enough I reckon, my speakers (602's) are down 3db at 49Hz, so its a fair bit extra extension 🙂
I always thought MDF was the better material. Clearly that isn't the case, is plywood as easy to use (it doesn't split apart easily?). I don't see there being too much resonance in either material with a folded line however.
The push push construction is interesting. I'm not as keen on the physical appearance of it, but then I might find myself wondering if i've missed out on something by not using it in the future. For now I think i'll stick with the PMC type arrangement.
I've very roughly drawn what I think is what Scottmoose specified, I expect i'm way off the mark though
. The response down to mid 20's is good enough I reckon, my speakers (602's) are down 3db at 49Hz, so its a fair bit extra extension 🙂I always thought MDF was the better material. Clearly that isn't the case, is plywood as easy to use (it doesn't split apart easily?). I don't see there being too much resonance in either material with a folded line however.
The push push construction is interesting. I'm not as keen on the physical appearance of it, but then I might find myself wondering if i've missed out on something by not using it in the future. For now I think i'll stick with the PMC type arrangement.
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Dr.Em: What you have drawn looks good. You might want to position the drivers away from the start of your line, as in reverse the placement of your dividers.
What P10 and scottmoose are saying is that baltic birch plywood is better than MDF. As the resonant freq. of either material is greater than 200 Hz, I believe it doesn't matter. Baltic birch ply is pretty expensive though, and can be hard to come by.
First and foremost: have fun.
What P10 and scottmoose are saying is that baltic birch plywood is better than MDF. As the resonant freq. of either material is greater than 200 Hz, I believe it doesn't matter. Baltic birch ply is pretty expensive though, and can be hard to come by.
First and foremost: have fun.
Another thing about MDF i just remembered -- i don't know if it is relevant, especially once a finish is applied, but MDF is not air tight. You will see on occasion a piece of 19mm MDF used as a convient platform for smaller pieces on a big vacuum hold-down CNC panel router. The vacuum sucks the top pieces down right thru the sheet underneath it,
We could have as much free MDF as we wanted. But we'd rather go out and buy BB ply because of the sonic benefits.
I am convinced that MDF has gained its status because some smart fellow promoted this new material (when i started speaker building it was not available -- we used K3 particle board) as new superior tech. He did it not because it was better, but because it was cheaper, cheaper to work with, and cheaper to finish. Now the myth is so ingrained even vetern speaker building companies believe it to be true.
dave
We could have as much free MDF as we wanted. But we'd rather go out and buy BB ply because of the sonic benefits.
I am convinced that MDF has gained its status because some smart fellow promoted this new material (when i started speaker building it was not available -- we used K3 particle board) as new superior tech. He did it not because it was better, but because it was cheaper, cheaper to work with, and cheaper to finish. Now the myth is so ingrained even vetern speaker building companies believe it to be true.
dave
I have taken a break from burning all of my inferior quality speakers to write this. Another thing about MDF is that it doesn't burn well.
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Joined 2002
Well, it has to be good for something... the the bonfires be built. 😉 Vile stuff. Chipboard (particle board) is better. At least this one would be well-braced, but that's still not going to prevent audible panel vibrations. In this case, to push them below the passband of operation, you'd need to go to over 2 1/4in thick of the stuff, which instantly causes even more problems with energy storage. Nah. Not for me.
MDF, yes, it can cause problems in wide range boxes with large unsupported panels, like the typical single driver lorn loaded cabinet, but for your limited bandwidth bass bin with all those internal baffles providing support, then I can see no problem, personally speaking. 😉
pinkmouse: Finally, a voice of reason.
Planet10: Impressive piles. Apart from creates the worlds finest speakers, you also have a sideline in waste management🙂
scottmoose: The esteemed expert acoustician. I bow before you😉
Planet10: Impressive piles. Apart from creates the worlds finest speakers, you also have a sideline in waste management🙂
scottmoose: The esteemed expert acoustician. I bow before you😉
Thanks for that design Planet10. I'm still probably going to do the PMC type driver arrangement (I don't doubt the push push arrangement is better but i'm too set on the original designs appearance 😱) , but I noticed something on your design which I had thought about. That is the slanting of the panels. This reduces standing waves? I will definately try to do that, however I don't have a way to cut the wood ends so that they fit flush with the other boards (that probably made no sense so I attached an image).
I'll have a look for plywood, I may end up going to a new (and very big) hardware store opening here in about a month for cabinet supplies. They might well have it but I tend to agree with pinkmouse's comments about the matter. The airtight point is interesting though, does it have much bearing acoustically? I don't imagine the pressure is enough for it too really.
Also, in the design Scottmoose layed out is the TL length critical to the drivers? Could I extend it to achieve further extension or will it not function properly then?
Once I get to a certain level of construction we'll be onto the interesting point of stuffing. The PMC stuff looks like studio foam 😱 . Can you use that (possibly in conjunction with wool or similar)?
I'll have a look for plywood, I may end up going to a new (and very big) hardware store opening here in about a month for cabinet supplies. They might well have it but I tend to agree with pinkmouse's comments about the matter. The airtight point is interesting though, does it have much bearing acoustically? I don't imagine the pressure is enough for it too really.
Also, in the design Scottmoose layed out is the TL length critical to the drivers? Could I extend it to achieve further extension or will it not function properly then?
Once I get to a certain level of construction we'll be onto the interesting point of stuffing. The PMC stuff looks like studio foam 😱 . Can you use that (possibly in conjunction with wool or similar)?
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Reason?!? We don't want any of that around here! Let acrimony and hatred rul... nah. Sorry. My twisted sense of humur getting the better of me. 😀 Pink' has indeed a wonderful gift of compromise, something which I lack. That's why he's such a good moderator and speaker builder / designer / enthusiast. Envy is a terrible sin (although some terrible sins are fun... 
), but I really wish I had that gift.
Dave indeed has some of the finest FR designs on the planet (sorry) on his sites. Too many to count really. State of the art Fonkens and bipoles, hosting Ron Clarke's horns, the Frugal-horn (the most advanced compact corner-horn available) etc. The list goes on. We all owe him a debt of immense gratitude.
Me? Expert? At anything? Particularly acoustics? I wish! 😉 Removing tongue from cheek, I'll take this opportunity to say that, in all honesty, if I know anything at all, it's Greg, Martin, Ron and Dave I owe it to. Terry Cain too. I must drive those guys mad with some of my elementary 'mistakes' (a polite way of putting it). No pretense here guys -I'm a novice in this game compared to many here, especially the above-mentioned.
), but I really wish I had that gift. Dave indeed has some of the finest FR designs on the planet (sorry) on his sites. Too many to count really. State of the art Fonkens and bipoles, hosting Ron Clarke's horns, the Frugal-horn (the most advanced compact corner-horn available) etc. The list goes on. We all owe him a debt of immense gratitude.
Me? Expert? At anything? Particularly acoustics? I wish! 😉 Removing tongue from cheek, I'll take this opportunity to say that, in all honesty, if I know anything at all, it's Greg, Martin, Ron and Dave I owe it to. Terry Cain too. I must drive those guys mad with some of my elementary 'mistakes' (a polite way of putting it). No pretense here guys -I'm a novice in this game compared to many here, especially the above-mentioned.
Dr.EM: Those angled baffles can have a straight cut on the end, with the gap (which will be small) filled with a sealant such as silicone. For a five degree angle, the gap would be less than 1 mm.
I think the original looks great with the drivers up front and the box slim. Will you go the extra step and veneer it?
Having built TLs before, I can tell you the stuffing can take a while to get right. Too much and you choke the bass.
Good luck. Have fun.
I think the original looks great with the drivers up front and the box slim. Will you go the extra step and veneer it?
Having built TLs before, I can tell you the stuffing can take a while to get right. Too much and you choke the bass.
Good luck. Have fun.
MJL21193 said:
My sense of not throwing stuff in the trash is sometimes a burden... steel gets picked up by a fellow down the road... he fills his dead cars with it before sendng them to the crusher (and gets an extra 420 or so a ton). Plastics go to a local place that makes plastic "timber" aluminum & copper i save for myself -- the price has gone up enuff that it actually generates some spending money. I'm patiently waiting for the PCB recycler (can't have all that gold & copper go to wast not to mention having the real toxic stuff get into the environemt. The burden comes in separating an item into its recyclable bits.
dave
Dr.EM said:
The slanting of the panels is what give you the 3:1 taper in the design. This improves the low pass function of the TL and allows it to be shorter (and therefore smaller) at the same time.
No you cannot willy nilly change the design without changing its performance.
Going to dual front loaded drivers may fit your asthetic better, but will noticably decrease the downward dynamic range of the speaker. But you have to live with it, so the set of compromises you chooe are your own.
dave
MJL21193 said:
I don't know about that. I do hope that my designs at least push towards the goal of the end user putting together a frugal-phile(tm) system that lets them enjoy the music, and that puch above their weight (price) class. Ignoring finish & labour many of these can be achieved for <$200-250/pr and i have heard speakers costing 10 time (or even more) that i don't enjoy as much.
Every design takes advantage of some 30+ years of experience in hifi and in speaker building and has accelerated of late with the interaction that the internet now allows with the experience & skills of many others. New tools flike MJK & Fuzzmeasure don't hurt either.
My goal isn't to design the best speakers... it is to design very good speakers that cost very little money and that takes every trick in the book.
dave
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