Vil said:
If you already have the Lambda then I'd say go for it, BUT remember that the quality of the enclosure can make a HUGE difference - so don't base the performance soley on that attribute (..though the basic freq. response and extension will be similar - so you should have some idea if you like the Lambda that way).
Vil said:
I think this depends on how long you'll have to wait.. If you can get the lambda's now and could not possibly afford the Supra's for a year+ then I'd go for the Lambdas. If you are within 9 months of the Supra's then I'd wait. (just my 2 cents though..)
And remember, you could probably "unload" the lambda's pretty quickly for half that amount so that your effective cost IF you purchased both (lambda's now and supra's in the future) would likely be less than an additional $250.
just some things to think about..
Once again Scott I'm somewhat overwhelmed by the sheer detail in your post.
BTW I'm still going for the supravox's, despite my 'revelation' regarding the seas, I've got the money set aside, I'm building completely new enclosures so I figure why the hell not.
I'm struggling to visual you whole laminar air flow thing and some implementation details would be impossible or simply impratical for me to pursue.
What I'll do is knock up a rough sketch of what I think your describing and then post it here, you can then say yay or nay and correct where I've gone wrong.
The impraticalities for me would be the concrete, for me to make it work the duct would need to be made out of MDF in an octagon shape or something like sonotube.
Micro rocking would be best done by bracing the magnet from the rear as I already do now.
I'll pop back with that sketch and tell me where I'm missing the point.
BTW I'm still going for the supravox's, despite my 'revelation' regarding the seas, I've got the money set aside, I'm building completely new enclosures so I figure why the hell not.
I'm struggling to visual you whole laminar air flow thing and some implementation details would be impossible or simply impratical for me to pursue.
What I'll do is knock up a rough sketch of what I think your describing and then post it here, you can then say yay or nay and correct where I've gone wrong.
The impraticalities for me would be the concrete, for me to make it work the duct would need to be made out of MDF in an octagon shape or something like sonotube.
Micro rocking would be best done by bracing the magnet from the rear as I already do now.
I'll pop back with that sketch and tell me where I'm missing the point.
An externally hosted image should be here but it was not working when we last tested it.
Thats my take on things so far.
Blue is the driver.
Green is the straws.
Grey is the driver back brace connected to the duct walls.
Yellow is a 3" thick layer of MDF
Red is bracing that holds the duct in place and fully encapsulates it and connects it with every wall of the cabinet.
Am I close?
It looks a bit more like the traditional method I mentioned, note however that you will have some driver "micro-rocking" even with the driver braced in the cabinet. (and this, contrary to the claims by DK Designs, was the major reason for the superiority of their milled aluminum speaker. http://www.positive-feedback.com/Issue20/dkdesignsf7.htm )
It seems then that you don't want to work with cement at all? - OK, lets pair it down then. (correct me if I'm mistaken here..)
And yes - VERY close!
1. Lets keep with double-wall construction but simplfy it. No "fluting" - just double up the boards, however in between them use several thumb-size pieces of the thinest Microsorb. This time however we will do this for all the panels except the bottom, (i.e. the top as well as the sides). In otherwords "sandwich" construction - 2 pieces of mdf with a bit of microsorb in between. (You'll still need to seal the gap between the boards near the driver with some caulk or filler.)
btw, this is my source for microsorb (pg. 19 of the pdf):
http://www.percyaudio.com/Catalog.pdf
who knows.. if you ask Wimslow, maybe they will carry it?
2. We will use the driver brace method, but you have it wrong in the drawing (the grey brace). You have the brace vertically behind the driver's magnet, instead what you should have is a horizontal grey line extending from the rear cabinet wall, through the middle of the reflector and ending abutted to the back of the driver's magnet.
3. The Duct/Port is essentially correct, however you don't need a flare at the exit and you need to extend the straws forward around the magnet assmebly (..currently they are stopped at the back of the magnet assmebly).
The basic tube would be something like this cut to length:
http://www.quikrete.com/catalog/Quik-Tube.html
(the 8 inch version)
Because the walls of this are thin you will need bracing (with a good deal of surface area) - which you pretty much have in red. The difference then is that I would add:
1 red line at both ends of the Duct/Port, and one red line effectivly where the cone meets the magnet.
4. your missing the aperiodic vent (and it can go on the back panel if you want it to) - and you might as well purchase the Scan Speak version (I've used them and they still work, they just are not as good as the solution I was suggesting). They spec 1 for up to 50 liters so 1 should be OK.
5. Instead of a triple layer of mdf for the bottom - consider an mdf box filled with lead shot and fine sand. This can help quite a bit.
6. The driver should be further up (only about 10 % of the way down from the top panel).
Also, I realize that the micro-sphere paint isn't something that would be shown on a diagram, but with this version it will become even more important (i.e. add a several more coats to the "equation" on the interior).
It seems then that you don't want to work with cement at all? - OK, lets pair it down then. (correct me if I'm mistaken here..)
And yes - VERY close!
1. Lets keep with double-wall construction but simplfy it. No "fluting" - just double up the boards, however in between them use several thumb-size pieces of the thinest Microsorb. This time however we will do this for all the panels except the bottom, (i.e. the top as well as the sides). In otherwords "sandwich" construction - 2 pieces of mdf with a bit of microsorb in between. (You'll still need to seal the gap between the boards near the driver with some caulk or filler.)
btw, this is my source for microsorb (pg. 19 of the pdf):
http://www.percyaudio.com/Catalog.pdf
who knows.. if you ask Wimslow, maybe they will carry it?
2. We will use the driver brace method, but you have it wrong in the drawing (the grey brace). You have the brace vertically behind the driver's magnet, instead what you should have is a horizontal grey line extending from the rear cabinet wall, through the middle of the reflector and ending abutted to the back of the driver's magnet.
3. The Duct/Port is essentially correct, however you don't need a flare at the exit and you need to extend the straws forward around the magnet assmebly (..currently they are stopped at the back of the magnet assmebly).
The basic tube would be something like this cut to length:
http://www.quikrete.com/catalog/Quik-Tube.html
(the 8 inch version)
Because the walls of this are thin you will need bracing (with a good deal of surface area) - which you pretty much have in red. The difference then is that I would add:
1 red line at both ends of the Duct/Port, and one red line effectivly where the cone meets the magnet.
4. your missing the aperiodic vent (and it can go on the back panel if you want it to) - and you might as well purchase the Scan Speak version (I've used them and they still work, they just are not as good as the solution I was suggesting). They spec 1 for up to 50 liters so 1 should be OK.
5. Instead of a triple layer of mdf for the bottom - consider an mdf box filled with lead shot and fine sand. This can help quite a bit.
6. The driver should be further up (only about 10 % of the way down from the top panel).
Also, I realize that the micro-sphere paint isn't something that would be shown on a diagram, but with this version it will become even more important (i.e. add a several more coats to the "equation" on the interior).
ShinOBIWAN said:
oops, got there ahead of me..
1. yup
2. nope
see my recent post for quasi clarification.
oops again, re-read your post above.. yes sonotube should be preferable (more massive). It needs to be a cylinder (not a hexagon) - still you could build up a lot of cross sections (like the laminations of a transformer) of mdf with a circular cut-out and glue it all together. Come to think of it that sounds pretty damn good..(but a LOT of work).
If you want to handle airflow behind the driver, this is probably the most important place.
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Joined 2003
No offense taken Shin.
I think this is a common mistake in any kind of scientific enquiry. It's easy to draw the wrong line of conclusion when we think we've exhausted all possibilities.
From personal discussions with Troels I know that he is extremely rigorous in his methodology, sometimes even a bit pedantic. So I had no reason not to believe him when he said he had found a good configuration for the L22RNX4P.
When he cannot find a good solution, he just says so. eg.
'I couldn't get as good a sound with the parallel filter as my series filter, so I gave up' .But I've never heard him concluding or championing that "series filters are therefore better".
To me that comes with age and experience. Again, no offense intended, but you and me- we're both the same age and fom the "first time" thread we've both revealed that we've only just started in this hobby. We have a lot to learn...
One more thing I can say about the L22RNX4P is that if you haven't investigated a notch filter in the low pass, to tame the primary 4Khz resonance and further hash, perhaps it's worth a try. Yes the peak is a few octaves away from your crossover point, but without a notch filter Troels found it audible on pink noise testing. Notching it out lead to improvements in test tone material, and may lead to improvements in bass-mid integration when listening to program material.
ShinOBIWAN said:
soongsc said:
Just be aware that time aligned is phase aligned, but not vice versa unless you get to minimum phase alignment. Time/Phase aligned XO does not mean that the acoutics will be time/phase aligned. Acoustics will can be time/phase aligned at specific points only, unless you can achieve the same acoustic radiation pattern throughout the audio range.
soongsc said:
Yep understood. Already knew that but thanks anyway.
Time alignment is the physical matching of acoustic centers relative to the listening position ie. sloped/stepped baffle, offsets etc.
Phase is the matching of the drivers radiation patterns.
And the XO's phase gets completely changed when it hit the drivers.
Lo Scott,
I've redone the sketch with the changes you have suggested, a few things that I'd like to ask though:
I've changed the reflector to a 'guide' since I really wish to mount the 215 GMF as close to the ATC as possible and it seems that this would work better, am I mistaken?
The aperoidic venting is confusing me, where exactly does it go and what does it look like?
I've redone the sketch with the changes you have suggested, a few things that I'd like to ask though:
I've changed the reflector to a 'guide' since I really wish to mount the 215 GMF as close to the ATC as possible and it seems that this would work better, am I mistaken?
The aperoidic venting is confusing me, where exactly does it go and what does it look like?
An externally hosted image should be here but it was not working when we last tested it.
Ola!
Everything looks good except:
1. The reflector should be like it was b4 but with a slighty larger diameter (as large as, or slightly larger than, the diameter of the Duct/Port) - AND a more aggresive (triangle-like) angle. Don't worry about it being close to top panel - all other surfaces but the reflector will have 10+ coats of the NASA paint (which absorbs freq.s between 10 Hz to 20 kHz with little airflow resistance).
The reflector has 3 basic functions:
I. Reflect higher freq.s into absorptive boundries. Important with the thin diaphram on the Supravox. Otherwise of little importance.
II. Provide a dispersive airflow. Minor importance, and this relates to the question about being near a boundry like the top panel.
III. Breakup standing waves, particularly those that would generate between the back panel and the driver (and in the Duct/Port). This is by FAR the #1 reason for this device - so my use of the term "reflector" is a bit of a misnomer.
2. The aperiodic vent is as follows (and your UK supplier should have it):
http://www.madisound.com/cgi-bin/index.cgi?cart_id=6445770.11910&pid=1607
I think the interior diameter is 4 inches, don't remember what the exterior diameter is.. Don't believe the bit about increasing the volume 20% - the effect in some circumstances is like this, but you should be working with your max 50 liters (or a bit more if you can..).
In a perfect world we would have a supercomputer to model the interior standing waves and see where the placement of the "vent" should be.. but we don't. So, experienced guessing (when considering esthetics) leads me to say that it should be on the back panel 20% up from interior's bottom, centered.
3. The grey brace doesn't have to be that large a diameter - (though if it was you could probably find some pvc pipe (plumbing section) that was close to being the perfect "fit" for the magnet). If you do go the PVC route then you need to fill it with something like sand, or a lot of caulk (to dampen it). (I've done the latter b4 and it works rather well.)
4. The vertical bracing looks good UNLESS you have a "thin" profile tube. If however the sonotube is fairly massive (and non-resonant) then its perfect. (BTW, inspect the sonotube b4 purchasing - it needs to be ROUND not oval - and make sure the seller will cut it to the length you want.. I personal had a @@@@ of a time just cutting that cheap tubing I provided a link to - I shudder to think what real sonotube would be like to cut.) Also consider at least one horizontal brace (for the box, not the Duct/Port).
Everything looks good except:
1. The reflector should be like it was b4 but with a slighty larger diameter (as large as, or slightly larger than, the diameter of the Duct/Port) - AND a more aggresive (triangle-like) angle. Don't worry about it being close to top panel - all other surfaces but the reflector will have 10+ coats of the NASA paint (which absorbs freq.s between 10 Hz to 20 kHz with little airflow resistance).
The reflector has 3 basic functions:
I. Reflect higher freq.s into absorptive boundries. Important with the thin diaphram on the Supravox. Otherwise of little importance.
II. Provide a dispersive airflow. Minor importance, and this relates to the question about being near a boundry like the top panel.
III. Breakup standing waves, particularly those that would generate between the back panel and the driver (and in the Duct/Port). This is by FAR the #1 reason for this device - so my use of the term "reflector" is a bit of a misnomer.
2. The aperiodic vent is as follows (and your UK supplier should have it):
http://www.madisound.com/cgi-bin/index.cgi?cart_id=6445770.11910&pid=1607
I think the interior diameter is 4 inches, don't remember what the exterior diameter is.. Don't believe the bit about increasing the volume 20% - the effect in some circumstances is like this, but you should be working with your max 50 liters (or a bit more if you can..).
In a perfect world we would have a supercomputer to model the interior standing waves and see where the placement of the "vent" should be.. but we don't. So, experienced guessing (when considering esthetics) leads me to say that it should be on the back panel 20% up from interior's bottom, centered.
3. The grey brace doesn't have to be that large a diameter - (though if it was you could probably find some pvc pipe (plumbing section) that was close to being the perfect "fit" for the magnet). If you do go the PVC route then you need to fill it with something like sand, or a lot of caulk (to dampen it). (I've done the latter b4 and it works rather well.)
4. The vertical bracing looks good UNLESS you have a "thin" profile tube. If however the sonotube is fairly massive (and non-resonant) then its perfect. (BTW, inspect the sonotube b4 purchasing - it needs to be ROUND not oval - and make sure the seller will cut it to the length you want.. I personal had a @@@@ of a time just cutting that cheap tubing I provided a link to - I shudder to think what real sonotube would be like to cut.) Also consider at least one horizontal brace (for the box, not the Duct/Port).
I don't mean to sound like I'm trying to be a party pooper, but have you considered this? Very diminishing returns? This seems like an extremely time consuming and VERY complicated box construction. Forgive me for oversimplifying, but how much better than your standard sealed box with aperiodic vent will this really be? This stuff has pretty much left my league as far as knowledge goes (and definately as far as experience goes), but I often find that when I'm working on a project (even outside of audio) there is usually a simple elegant solution to a given problem. This seems like a very complicated solution.
m0tion said:
I second this comment. Normally, unless you have the mathematical part of all this simulated using finite element method to truly indicate the differences, it is much better to let the design grow via evolution process so that you can identify the improvements in each stage of the design. What we normally would do is try a certain technology on an existing product wto see if the difference is identifiable or not, if yes, then take the next step.
m0tion said:
I've actually tried this "formula" with fullrange drivers (high eff. low mms), and yes it does make a LARGE difference in the passband we are discussing (..and higher in freq. as well if your into fullrange drivers). With most HiFi drivers though - you could be correct that diminishing returns outweigh complexity (..don't know). Additionally, its not as difficult to build as you might think. I personally think that there are many cabinets that are FAR more complex (like Jensens with bitumen or lead lining) that can often yield significant audible benefits over your traditional bass reflex, (making them worthwhile despite the complexity). To me the real complexity isn't the cabinet build, but rather the cabinet finishing (..black laquer seems like such a simple yet elegant finish.. elegant it is, simple it isn't).
In any event, if Shin' wants to proceed with this design I'll try to be here to help-out. If he wants to dump-it in favor of somthing else, then thats cool too. Either way, I just hope that he gets the sound he is looking for (..or even better than what he presently "perceives" possible).
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