So here is a first go of experiments.....
Only thing in the boxes for no stuff measurements is a 4mm thick felt behind the woofers.
Here I have added 6cm thick foam cut to wedge shape on top and bottom of the box + some acusta stuf behind the woofers + 0.5lb acusta stuf at midpoint of enclosure......
Only thing in the boxes for no stuff measurements is a 4mm thick felt behind the woofers.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Here I have added 6cm thick foam cut to wedge shape on top and bottom of the box + some acusta stuf behind the woofers + 0.5lb acusta stuf at midpoint of enclosure......
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
To Steve
I run into a bit of trouble with the "mdf sandwich" project. I hoped that glueing the panels would be enough and I do not need to install metal rods from top to bottom. But at finishing stage before painting I made a mistake that I put the boxes into too hot enviroment to dry the plaster and small cracks appeared starting from woofer hole.
These are not too worrisome but I decided to drill the holes and install metal rods (4 per box) from top to bottom, just to be on safe side. It's easier before final finishing than to do it later when the box is finished (if it gets worse).
Anyway, this delays the project a bit and I hope to get the drivers in the boxes in about 3 weeks..... In Estonia it's all but easy to get a drill bit that are 45cm long.... I had to special order it.
Ergo
I run into a bit of trouble with the "mdf sandwich" project. I hoped that glueing the panels would be enough and I do not need to install metal rods from top to bottom. But at finishing stage before painting I made a mistake that I put the boxes into too hot enviroment to dry the plaster and small cracks appeared starting from woofer hole.
These are not too worrisome but I decided to drill the holes and install metal rods (4 per box) from top to bottom, just to be on safe side. It's easier before final finishing than to do it later when the box is finished (if it gets worse).
Anyway, this delays the project a bit and I hope to get the drivers in the boxes in about 3 weeks..... In Estonia it's all but easy to get a drill bit that are 45cm long.... I had to special order it.
Ergo
I've decided to put a sock in it.
Hi guys
After playing around with the helmholtz resonator and partitioning ideas. I've decided to put a sock in it.
The sock is filled with sand (there's cling-film around the sand). Then I coil it like a snake and fix it to the bottom of my columns with a little silcone.
I think this incorporates a good part of the angled-panel, wedge concept and also is less reflective than the MDF (non-reflection would cut the standing wave at source).
Of course, you have to add volume to allow for that taken up by the sock.
Upside: Seems to work, simple
Downside: I had to buy an extra pair for my wife.
I'm taking my finished prototypes (Nonsuch IVs plus Little Awesome and Bigger Awesome subs) to the High End Show in Frankfurt and I'm leaving next week. Wish me luck.
Thanks for all your help. I've enjoyed this thread and met some good people.
And so in return, I'm proud to present to all you crazy DIY Column Builders out there ......
Steve's Super Sexy Seventh Veil Sandy Snake Sock
Or ... "S3-7V-S3"
Steve
Hi guys
After playing around with the helmholtz resonator and partitioning ideas. I've decided to put a sock in it.
The sock is filled with sand (there's cling-film around the sand). Then I coil it like a snake and fix it to the bottom of my columns with a little silcone.
I think this incorporates a good part of the angled-panel, wedge concept and also is less reflective than the MDF (non-reflection would cut the standing wave at source).
Of course, you have to add volume to allow for that taken up by the sock.
Upside: Seems to work, simple
Downside: I had to buy an extra pair for my wife.
I'm taking my finished prototypes (Nonsuch IVs plus Little Awesome and Bigger Awesome subs) to the High End Show in Frankfurt and I'm leaving next week. Wish me luck.
Thanks for all your help. I've enjoyed this thread and met some good people.
And so in return, I'm proud to present to all you crazy DIY Column Builders out there ......
Steve's Super Sexy Seventh Veil Sandy Snake Sock
Or ... "S3-7V-S3"
Steve
x. onasis said:
Thanks x. I do feel that I'm going as one of us rather than one of them.
Seriously, on the "shoe" ... I haven't had time to get it absolutely right yet (cosmetically) but I've made it detachable. I'll get some made with slightly more extension at the rear and a bigger cut-out egg in the front. Think it will look better balanced.
Zozo said:Hi Steve !
Could you please tell a little bit more about how your sand in the sock design works? I guess it's not the smell of the sock which prevents the standing waves come alive
BTW the cabinet is pretty nice !
Zozo
Thanks Zozo.
The sand-sock is coiled like a little snake lying in the bottom of the enclosure. It works as a false bottom but unlike the actual MDF bottom, this false bottom is not flat and is less reflective.
A vertical standing wave thrives with a narrow enclosure, parallel top and bottom and reflective top and bottom.
Does this answer your question?
Steve
PS: Maybe the smell helps too.
It's a judgement call Zozo. Depends on the cross sectional area of the column and thickness of the snake. Remember that the volume of the snake is taking up good volume in the enclosure and the enclosure must be bigger to compensate.
My sense is that the snake must be thin enough to coil inside the enclosure, so the thicker the enclosure, the thicker the snake can be. It's difficult to coil a thick snake into a narrow enclosure. The coil should be long enough take up the cross section of the enclosure but your estimate is probably just as good as mine.
The sock is just knotted at both ends.
Let me know what you discover.
Steve
BTW the answer is "nothing at the moment" (the question is "What is he on?")
And for anyone wondering, here's the S3-7V-S3 link again.
My sense is that the snake must be thin enough to coil inside the enclosure, so the thicker the enclosure, the thicker the snake can be. It's difficult to coil a thick snake into a narrow enclosure. The coil should be long enough take up the cross section of the enclosure but your estimate is probably just as good as mine.
The sock is just knotted at both ends.
Let me know what you discover.
Steve
BTW the answer is "nothing at the moment" (the question is "What is he on?")
And for anyone wondering, here's the S3-7V-S3 link again.
7V:
Although the sand filled sock does take up enclosure space, you might have addressed two problems of tall, narrow enclosures at once-standing waves and the tendency to tip over.
Since adding a weight at the bottom to increase balance would not be a bad design idea, in a certain sense the space the sand-sock takes up could be said to come "for free".
Of course, in the promotional literature you give out at the show, you musn't call it a "sand-filled sock". Instead, I would suggest you extoll the virtues of your own "Helical Silicon Technology" which "creates a synergistic interaction between enhanced structural stability and suppressed negative reflectivity." Or something like that.
After the Nonsuch becomes a smash hit, the next model you make should be named The Argyle.
Although the sand filled sock does take up enclosure space, you might have addressed two problems of tall, narrow enclosures at once-standing waves and the tendency to tip over.
Since adding a weight at the bottom to increase balance would not be a bad design idea, in a certain sense the space the sand-sock takes up could be said to come "for free".
Of course, in the promotional literature you give out at the show, you musn't call it a "sand-filled sock". Instead, I would suggest you extoll the virtues of your own "Helical Silicon Technology" which "creates a synergistic interaction between enhanced structural stability and suppressed negative reflectivity." Or something like that.
After the Nonsuch becomes a smash hit, the next model you make should be named The Argyle.
kelticwizard said:Of course, in the promotional literature you give out at the show, you musn't call it a "sand-filled sock". Instead, I would suggest you extoll the virtues of your own "Helical Silicon Technology" which "creates a synergistic interaction between enhanced structural stability and suppressed negative reflectivity." Or something like that.
After the Nonsuch becomes a smash hit, the next model you make should be named The Argyle.
Brilliant keltic, "Helical Silicon Technology", of course.
Maybe you can come up with technical terms for the other features of the Nonsuch: crossover at 100Hz (well below midrange), linear array, egg-shaped interior cross-section with downward reflecting slats, slim baffle, oval outer for smooth diffraction, etc. With your skill at naming we could out Bose Bose. Hopefully have something half decent to listen to as well.
Actually, my columns are so slim that the HST device doesn't have enough weight to make much difference. It could on a wider cabinet.
Why Argyle? Call me dense. I'm only a speaker designer.
Steve
kelticwizard said:Why Argyle? For Argyle socks-the ones with the designs on them. As opposed to socks which are all black and white, for instance.
Aren't they the ones with little metal bits? According to my calculations there would be a 0.00017dB peak at 7,439Hz due to reflection. Sorry, out of the question.
Steve
PS: Actually, I used two socks in layers to prevent leaks so, from inside to outside:
sand, sock, clingfilm, sock. This is my Helical Silicon Dual Technology.
reducing vertical standing wave in column speakers
I have put up a page on my web site detailing the approach that I eventually took to this problem: reducing vertical standing wave in column speakers.
Since participating in this enjoyable thread and examining a number of different approaches including Helmhotz resonators, I have found that this simple solution seems to work effectively and has the added advantages of requiring very little skill to build and costing practically nothing.
I post this to introduce the idea to any 'new boys' out there and, perhaps to restart this line of questioning.
I have put up a page on my web site detailing the approach that I eventually took to this problem: reducing vertical standing wave in column speakers.
Since participating in this enjoyable thread and examining a number of different approaches including Helmhotz resonators, I have found that this simple solution seems to work effectively and has the added advantages of requiring very little skill to build and costing practically nothing.
I post this to introduce the idea to any 'new boys' out there and, perhaps to restart this line of questioning.
Hi All,
Though this thread is old, the idea persisted in my mind and I would like to share my findings.
The internal Helmholtz resonator can be used to damp an enclosure resonance, and I have found what formula to use for its calculation.
This type of frequency-targeted damping can be used to damp:
1. High (> 0.7) Q for an intentionally small enclosure (design aesthetics)
2. Half-wave mode (closed pipe) resonances as exhibited by tall enclosures
In my test, I used a closed box design. The enclosure was divided arbitrarily into two as physical configuration of tweeter/mid placement dictates, and a vent connected the two volumes. My goal was to damp the problem in number 1 above.
Spring-mass analysis of the HR system leads to a configuration where the two volumes’ compliance act in parallel to the common mass that is the vent.
Getting the target frequency to damp. I measured the box system frequency with only a hole (where the vent pipe was to go through later) in the divider. Its effective HR frequency at this moment is well above system frequency, and not yet enough to affect the closed box frequency.
For port length calculation, the volume I used is V1||V2, due to the spring-mass analysis. Both port mouths are then damped by covering each with two layers polyester batting that is used in making pillows. I did not use the Helmholtz formula as there is already a simpler formula (and calculator abounds) – I used the vented box port formula.
Assembled box with the vent tube in place. When I measured the system impedance, at first two humps about the system frequency were visible due to the allowance of my port cut. Further, the phase plot was like vented box zero crossings and indicated mistuned HR port. Frequency response had a dip where the valley of the two humps were located.
When I cut the port again to the dimension calculated, on the impedance plot the two humps disappeared, and a single low Q hump is left at system frequency. The phase plot now resembles closed box zero crossing. The frequency response has no dip anymore, and a low Q hump is in place.
I admit the driver I used is a very large Q’ed one, in the range of 1+. I didn’t measure Vas as I do not intend to follow the calculated box volume as it would be huge for the driver’s size, and I chose a box volume based on driver physical size alone instead.
I haven’t yet tested problem two above, as I have limited time and resources, but the spring-mass analysis still applies for the calculation of the HR.
For the original problem presented by KW in which the tall enclosure would be possibly vented outside (maybe it doesn’t matter from which of the two volumes), the spring-mass analysis can be applied by breaking down the problem as follows – cap the outside vent, then calculate the HR as in closed box above. The resulting two volumes still act in parallel on the common port. For the outside vent calculation (lower vented box frequency), ignore the partition and use the sum of the two volumes.
Thanks all,
Dexter
Though this thread is old, the idea persisted in my mind and I would like to share my findings.
The internal Helmholtz resonator can be used to damp an enclosure resonance, and I have found what formula to use for its calculation.
This type of frequency-targeted damping can be used to damp:
1. High (> 0.7) Q for an intentionally small enclosure (design aesthetics)
2. Half-wave mode (closed pipe) resonances as exhibited by tall enclosures
In my test, I used a closed box design. The enclosure was divided arbitrarily into two as physical configuration of tweeter/mid placement dictates, and a vent connected the two volumes. My goal was to damp the problem in number 1 above.
Spring-mass analysis of the HR system leads to a configuration where the two volumes’ compliance act in parallel to the common mass that is the vent.
Getting the target frequency to damp. I measured the box system frequency with only a hole (where the vent pipe was to go through later) in the divider. Its effective HR frequency at this moment is well above system frequency, and not yet enough to affect the closed box frequency.
For port length calculation, the volume I used is V1||V2, due to the spring-mass analysis. Both port mouths are then damped by covering each with two layers polyester batting that is used in making pillows. I did not use the Helmholtz formula as there is already a simpler formula (and calculator abounds) – I used the vented box port formula.
Assembled box with the vent tube in place. When I measured the system impedance, at first two humps about the system frequency were visible due to the allowance of my port cut. Further, the phase plot was like vented box zero crossings and indicated mistuned HR port. Frequency response had a dip where the valley of the two humps were located.
When I cut the port again to the dimension calculated, on the impedance plot the two humps disappeared, and a single low Q hump is left at system frequency. The phase plot now resembles closed box zero crossing. The frequency response has no dip anymore, and a low Q hump is in place.
I admit the driver I used is a very large Q’ed one, in the range of 1+. I didn’t measure Vas as I do not intend to follow the calculated box volume as it would be huge for the driver’s size, and I chose a box volume based on driver physical size alone instead.
I haven’t yet tested problem two above, as I have limited time and resources, but the spring-mass analysis still applies for the calculation of the HR.
For the original problem presented by KW in which the tall enclosure would be possibly vented outside (maybe it doesn’t matter from which of the two volumes), the spring-mass analysis can be applied by breaking down the problem as follows – cap the outside vent, then calculate the HR as in closed box above. The resulting two volumes still act in parallel on the common port. For the outside vent calculation (lower vented box frequency), ignore the partition and use the sum of the two volumes.
Thanks all,
Dexter
I would like to add that in the original problem of tall enclosure beset by standing waves, the target frequency for the HR would be the fundamental frequency of the closed pipe, which is c/2L.
Two volumes in parallel compliance mode would have an effective volume:
Veff = V1||V2 = V1V2/(V1 + V2)
Thanks,
Dexter
Two volumes in parallel compliance mode would have an effective volume:
Veff = V1||V2 = V1V2/(V1 + V2)
Thanks,
Dexter
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