WRT this part in particular - you repeatedly bring up the cost of your equipment and years of experience as if that has any bearing whatsoever.
As a sanity check let's go back and review post 232.
http://www.diyaudio.com/forums/subw...binet-16-hz-organ-speaker-24.html#post4412240
In that post you DEFENDED the fact that you believed 843g MMS was correct when TB46 originally brought it up. It wasn't until much later that I brought up the fact that 843g was absurdly ridiculous and posted MMS of a bunch of other extremely high MMS drivers for comparison, none of them having anywhere near that much MMS that you reconsidered and took another look.
Despite all your fancy equipment and years of experience you made a mistake with the weights. And rather than taking a closer look at that point you insisted that the driver itself had changed and MMS had doubled in between production runs to a record setting 843g.
And I am suggesting that despite all your fancy equipment and years of experience you have also made a mistake with the measurement environment.
It would take approximately 5 minutes to take the stupid driver out of the car and measure it properly but you don't want to do that, apparently you would rather insist that EVERYONE ELSE that has measured this driver (and there are a lot and they are all in close agreement) have done it wrong and you are the only one with correct measurements.
Last kick at the can.
And I am done with this.
All the openings of the vehicle were open.
Trunk, and Doors.
The cone movement is minuscule. There can be no pressure zone differences in this test versus a test on a table, or on a IEC baffle. And this is again known from exhaustive testing of hundreds of drivers in many different conditions.
Don't pretend that you have this figured out. I certainly don't have this figured out!
I design drivers for a living and can tell you that there is every possibility that each of those measurements are as accurate as the ones I did. I only measured one of those drivers. I have no experience with any others.
So I thought I would share a little of what goes on in the real world of loudspeaker production.
There can be driver parameter variations on a budget driver.
The components that stay the same are as follows.
The coil should stay the same I hope.
The basket. For sure.
Now for the parts that have a variability concern:
The size of magnet should be constant.
The variability in the magnet is two fold. Type of magnet? Just because it is dark grey does not mean you know the grade of the ferrite that you are looking at. You have to measure the charge voltage and amperage and the resulting flux density on the magnet to know for certain what you are dealing with.
And the level of charge. The quality factories in China have generators that kick in when the power voltage dips.
This will effect the Qts and Qms numbers the most.
Why is this important?
Your magnetizer runs on the line voltage and when it drops so does the state of magnification.
Steel. Which type did they use? This will effect BL as the total flux density can be a little different if you are using higher carbon steels.
I use 1008 steel from Sumitomo in Japan or silicone iron if you are really interested in the highest flux density. And yes the steel comes from Japan. And yes it is verified to be from Sumitomo on each of the four to 8 trucks that come into the forging factory that I work with. They are the largest loudspeaker motor parts manufacturer in the world.
Machining tolerance. I think that the woofer uses a one piece backplate/Tyoke. If it does the tolerance differences are not that big a deal. The area where they make the largest difference is the gap between the toplate and the pole piece where the voice coil fits in. Depending on the driver you need pretty good tolerances in your metal pieces to keep your desired flux density. If you are to wide by even 0.3mm you will be loosing motor force.
If the pole piece and the back plate are swaged all bets are off. I don't do these for a very simple reason. They are a desperate problem waiting to rear it's ugly head. There is little control on the method used to swage or mushroom out the pole piece. And you need to loosen up your tolerances quite a bit because you don not know if the two pieces are installed with proper perpendicularity. One piece backplates and pole pieces only for me.
I think that Nick has the same design philosophy. Because on the driver I tested it was indeed a one piece backplate and pole piece.
The adhesives are variable unless you are using regulated and calibrated automatic dispensing systems. Mms is the subject of this variability. And the calibration must be done on a very regular basis. The pneumatics settings drift quite a bit if you are not keeping them in check. We do it every twenty minutes.
The spider is the object of most variability due to where you are sourcing it.
I get mine from a company in Taiwan. And only from that company. Because they are Japanese owned and run like a Swiss watch company. Fully automated in the processes that make a difference. I talk to the people that make them and I get what I ask for. If we need changes they get made.
Cones. Again just because a cone looks the same as another one does not mean that it is the same as the other ones. Every cone is made by a mix master. The additives used and the quantities are kept proprietary to the company producing them. And they are varied according to the experience of the person controlling the mix. Where you get your cones from makes some of the largest changes in consistency and the tonality of your product.
I work with only a few cone vendors. You will not find them on the net. They don't have to advertise. Last time I was there I was watching cones for the B&W midrange cones being formed. The fancy Kevlar ones in the 800 series. I get all my cones weighed when I do driver runs. For the explicit reason that we reject the ones that do not meet specs. And we can keep a tight rein on the overall quality control.
The next time I go to the factory we will be setting up a simple and effective Cms testing rig to qualify the surrounds as well. That will be the last frontier where we can control and measure the production parameters of a driver.
The surround is not as simple as you might believe either. The "rubber" ones are an admixture of many types of elastomer. And depending on where you get them they may or may not be the same from product run to product run. They are difficult to quantify until you have them in a driver testbed.
The foam surrounds are an entirely different animal as are the clothe surrounds. They depend on more variables than even the "rubber surrounds". The foam surrounds are pressed out of a very thick foam that is heated and forced between top and bottom formed dies. Think of the foam blank as being 4 to 6 inches thick and the the the foam surround in pressed out. Heating and cycle time are very important in keeping these consistent. The foam itself is the next variable factor as it is dependent on the additives and the mixing process used to create it. I pretty much only use foam on a few applications where it is difficult to use something else.
Cloth surrounds are subject to the type of cloth, the coating. The warp and weave of the clothe if it is not setup correctly in the cutter. Al these things have a bearing on how the parts behave when put into actual use. And you can tell almost nothing from looking at them. How sharp were the cutters used to blank out the cloth? dull ones stretch the weave pattern and change the flexibility of the fabric matrix. And where are the doping agents for the cloth coming from? are they mixed under controlled repeatable conditions or is someone doing it by wrote? The more expensive products are just as good as anything you can get here. But you have to qualify the vendors. Know for a fact that they are indeed vendors. And not resellers of parts made in garages and alleyways. The reasons why I travel to China a qualify those who I work with in the first place.
So Anthony as far as I'm concerned this is done.
You don't know in your whole body what my pinky finger knows about drivers. And yet I treat you with respect. Because you are an intelligent fellow. Just remember this part. Treat others how you yourself would like to be treated.
And I am done with this.
All the openings of the vehicle were open.
Trunk, and Doors.
The cone movement is minuscule. There can be no pressure zone differences in this test versus a test on a table, or on a IEC baffle. And this is again known from exhaustive testing of hundreds of drivers in many different conditions.
Don't pretend that you have this figured out. I certainly don't have this figured out!
I design drivers for a living and can tell you that there is every possibility that each of those measurements are as accurate as the ones I did. I only measured one of those drivers. I have no experience with any others.
So I thought I would share a little of what goes on in the real world of loudspeaker production.
There can be driver parameter variations on a budget driver.
The components that stay the same are as follows.
The coil should stay the same I hope.
The basket. For sure.
Now for the parts that have a variability concern:
The size of magnet should be constant.
The variability in the magnet is two fold. Type of magnet? Just because it is dark grey does not mean you know the grade of the ferrite that you are looking at. You have to measure the charge voltage and amperage and the resulting flux density on the magnet to know for certain what you are dealing with.
And the level of charge. The quality factories in China have generators that kick in when the power voltage dips.
This will effect the Qts and Qms numbers the most.
Why is this important?
Your magnetizer runs on the line voltage and when it drops so does the state of magnification.
Steel. Which type did they use? This will effect BL as the total flux density can be a little different if you are using higher carbon steels.
I use 1008 steel from Sumitomo in Japan or silicone iron if you are really interested in the highest flux density. And yes the steel comes from Japan. And yes it is verified to be from Sumitomo on each of the four to 8 trucks that come into the forging factory that I work with. They are the largest loudspeaker motor parts manufacturer in the world.
Machining tolerance. I think that the woofer uses a one piece backplate/Tyoke. If it does the tolerance differences are not that big a deal. The area where they make the largest difference is the gap between the toplate and the pole piece where the voice coil fits in. Depending on the driver you need pretty good tolerances in your metal pieces to keep your desired flux density. If you are to wide by even 0.3mm you will be loosing motor force.
If the pole piece and the back plate are swaged all bets are off. I don't do these for a very simple reason. They are a desperate problem waiting to rear it's ugly head. There is little control on the method used to swage or mushroom out the pole piece. And you need to loosen up your tolerances quite a bit because you don not know if the two pieces are installed with proper perpendicularity. One piece backplates and pole pieces only for me.
I think that Nick has the same design philosophy. Because on the driver I tested it was indeed a one piece backplate and pole piece.
The adhesives are variable unless you are using regulated and calibrated automatic dispensing systems. Mms is the subject of this variability. And the calibration must be done on a very regular basis. The pneumatics settings drift quite a bit if you are not keeping them in check. We do it every twenty minutes.
The spider is the object of most variability due to where you are sourcing it.
I get mine from a company in Taiwan. And only from that company. Because they are Japanese owned and run like a Swiss watch company. Fully automated in the processes that make a difference. I talk to the people that make them and I get what I ask for. If we need changes they get made.
Cones. Again just because a cone looks the same as another one does not mean that it is the same as the other ones. Every cone is made by a mix master. The additives used and the quantities are kept proprietary to the company producing them. And they are varied according to the experience of the person controlling the mix. Where you get your cones from makes some of the largest changes in consistency and the tonality of your product.
I work with only a few cone vendors. You will not find them on the net. They don't have to advertise. Last time I was there I was watching cones for the B&W midrange cones being formed. The fancy Kevlar ones in the 800 series. I get all my cones weighed when I do driver runs. For the explicit reason that we reject the ones that do not meet specs. And we can keep a tight rein on the overall quality control.
The next time I go to the factory we will be setting up a simple and effective Cms testing rig to qualify the surrounds as well. That will be the last frontier where we can control and measure the production parameters of a driver.
The surround is not as simple as you might believe either. The "rubber" ones are an admixture of many types of elastomer. And depending on where you get them they may or may not be the same from product run to product run. They are difficult to quantify until you have them in a driver testbed.
The foam surrounds are an entirely different animal as are the clothe surrounds. They depend on more variables than even the "rubber surrounds". The foam surrounds are pressed out of a very thick foam that is heated and forced between top and bottom formed dies. Think of the foam blank as being 4 to 6 inches thick and the the the foam surround in pressed out. Heating and cycle time are very important in keeping these consistent. The foam itself is the next variable factor as it is dependent on the additives and the mixing process used to create it. I pretty much only use foam on a few applications where it is difficult to use something else.
Cloth surrounds are subject to the type of cloth, the coating. The warp and weave of the clothe if it is not setup correctly in the cutter. Al these things have a bearing on how the parts behave when put into actual use. And you can tell almost nothing from looking at them. How sharp were the cutters used to blank out the cloth? dull ones stretch the weave pattern and change the flexibility of the fabric matrix. And where are the doping agents for the cloth coming from? are they mixed under controlled repeatable conditions or is someone doing it by wrote? The more expensive products are just as good as anything you can get here. But you have to qualify the vendors. Know for a fact that they are indeed vendors. And not resellers of parts made in garages and alleyways. The reasons why I travel to China a qualify those who I work with in the first place.
So Anthony as far as I'm concerned this is done.
You don't know in your whole body what my pinky finger knows about drivers. And yet I treat you with respect. Because you are an intelligent fellow. Just remember this part. Treat others how you yourself would like to be treated.
If you haven't noticed, this is the whole problem. You entire attitude is dripping with condescention. Do you really think I don't know about parts variability?
If you were as bright as you think you are you should have noticed that 843g MMS was absurd right away.
Really? Do we need to recap post 311 and a bunch more like it?
"I really don't give a rats *** what you think.
You seem so self impressed by what you think you know that it blocks your ability to see and understand the obvious.
I suggest you go out and get your knowledable fingers on said driver. Drop a cool $1500 on some quality measurement equipment. Learn how to measure drivers and then argue.
Bloody hell you can be an agrivating little son of a motherless dog!"
http://www.diyaudio.com/forums/subw...binet-16-hz-organ-speaker-32.html#post4442451
I treat others EXACTLY as I would like to be treated. If your perspective is different than mine, come at me with everything you have. PROVE your point of view. If I can't prove mine then it really isn't worth much, is it?
People that like to hide behind resumes, constantly need to reiterate how many years of experience they have and where they have worked, what types of fancy equipment they have in lieu of actually technical facts have a HUGE blind spot that even common sense can't break through. You are probably sick of hearing about it but you posted that this driver had 843g MMS and tried to defend it. Where were all your years of experience in preventing you from making that beginner mistake? And why not just measure the driver properly instead of quoting your resume once again and talking about parts variability? Your measurements are vastly different than anyone else's, that's a red flag.
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About this part in particular, you brought this up before and I addressed it. It doesn't matter if the cone movement was miniscule, the environment ABSOLUTELY will affect the impedance curve.
If you don't believe this, measure the driver t/s in a sealed or ported box. The box itself IS an environmental influence. Go ahead and tell me that the miniscule cone movement means the environmental influence of the box isn't going to affect the t/s parameters. This is beginner stuff, it should be REALLY obvious.
A baffle, a box, a wall, a cavity A CAR INTERIOR, these are all environmental influences that will affect the impedance curve and also the t/s parameters. Open windows and doors or not, the impedance curve will be affected.
Just to be really clear about this here's a couple of pictures of random cars. Even if you do not consider ANY of the car except the area between the red lines in the first pic (which is unwise) you have what amounts to a OB H baffle that's about 3 feet deep (about 18 inches deep in the front cavity, about 18 inches deep in the rear cavity). The green line is about where the driver would be. If you don't think that will affect the impedance curve and think it's ok to measure t/s parameters in a 36 inch deep H baffle you simply are not doing it right.
4 door cars will not have as much cavity on the front side but they still have very deep trunk cavities as you can see in the second pic of a best selling car in the North American market. You have a 18 - 24 inch or so deep cavity before the nearest edge of the open trunk. This is going to affect the impedance curve regardless of whether the cone movement is miniscule or not. And it will affect the impedance curve at fairly low frequencies as well, which is why OB U baffles and H baffle subs never have cavities this deep since it creates audible and measureable huge resonances in subwoofer frequencies and subsequent changes to the impedance curve.
Even if you have smaller cavities in the particular model of car the driver was measured in it is never appropriate to measure t/s parameters in any car.
4 door cars will not have as much cavity on the front side but they still have very deep trunk cavities as you can see in the second pic of a best selling car in the North American market. You have a 18 - 24 inch or so deep cavity before the nearest edge of the open trunk. This is going to affect the impedance curve regardless of whether the cone movement is miniscule or not. And it will affect the impedance curve at fairly low frequencies as well, which is why OB U baffles and H baffle subs never have cavities this deep since it creates audible and measureable huge resonances in subwoofer frequencies and subsequent changes to the impedance curve.
Even if you have smaller cavities in the particular model of car the driver was measured in it is never appropriate to measure t/s parameters in any car.
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.
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Now here's the impedance of MJK's default H baffle example with the Alpha 15A in a H baffle with 15 inches of total depth, that's 7.5 inches deep front cavity and 7.5 inches deep rear cavity. This is the impedance result regardless of power level, whether the cone movement is miniscule or not. Even with only a 15 inch deep H baffle the difference in impedance is massive. This will have a huge impact on t/s parameters.
An externally hosted image should be here but it was not working when we last tested it.
I used one of the Stereo Integrity HT18 drivers in our organ project.
I just saw that the price had been lowered from $174 to $159. Shipping is only $5. Heck of a deal IMHO.
HT18 18″ Subwoofer | Stereo Integrity
Bach On
I just saw that the price had been lowered from $174 to $159. Shipping is only $5. Heck of a deal IMHO.
HT18 18″ Subwoofer | Stereo Integrity
Bach On
Price is reduced because Si said he's going out of the direct sales game and clearing out his inventory. He says he will only continue a few of his product lines and only deal with OEMs with the exception of the HST line ($$$) and very specialty items ($$$) like the 24 inch sub driver. He says Sundown is going to continue producing one of his products but the SI value subs are no longer available after the inventory sells out.
Big Stereo Integrity News - AVS Forum | Home Theater Discussions And Reviews
But anyone that is paying attention will know that he's done this before - he announced he was discontinuing the value line of sub drivers last year I think. And that caused a very predictable surge in sales. As soon as he sold out, he announced he was bringing them back again - and I believe the driver you bought was from that resurrected product line. It wasn't really out of stock for any length of time at all.
Big Stereo Integrity News - AVS Forum | Home Theater Discussions And Reviews
But anyone that is paying attention will know that he's done this before - he announced he was discontinuing the value line of sub drivers last year I think. And that caused a very predictable surge in sales. As soon as he sold out, he announced he was bringing them back again - and I believe the driver you bought was from that resurrected product line. It wasn't really out of stock for any length of time at all.
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And one last post to round this out in case the definition of MMS is not clear.
The definition of MMS is (from Eminence) - This parameter is the combination of the weight of the cone assembly plus the ‘driver radiation mass load’. The weight of the cone assembly is easy: it’s just the sum of the weight of the cone assembly components. The driver radiation mass load is the confusing part. In simple terminology, it is the weight of the air (the amount calculated in Vd) that the cone will have to push.
In other words it's the mass of the moving parts (cone, surround, former, spider, VC, glue) and the mass of air in front of the cone. It has NOTHING AT ALL to do with quality of steel and ferrite, charging voltage, parts tolerance or assembly tolerance of the motor, cone tonality, elasticity of the surround or the sharpness of the surround cutter.
You can literally measure MMD (not to be confused with MMS, MMD does not include the air load) by cutting the soft parts out of the driver and measuring them on a scale. So the bulk of this post is completely off topic hot air to divert attention by bringing up a lot of things that have nothing to do with anything.
Unless all the soft parts manufacturers were falling down drunk and completely negligent there should be no reason to see 100 - 150 grams difference in soft parts between production runs. I don't care what factory was assembling the parts. The new factory didn't slop an extra 100 grams of glue in there either. And again, these are all off the shelf parts, no previous production runs were 100 - 150 grams off the mark and there's no reason the new production run using the same off the shelf parts should be either.
SMALL differences are to be expected, both because of parts variability and because of the way t/s parameters are derived from an impedance curve. But 592 grams is not a small difference compared to all the other measurements.
And since there's multiple measurements in the 416 - 499 gram range taken as recently as a few months ago and Mark's is the only one sitting way out at 592, the most logical conclusion is that he measured wrong. Either that or the cone he measured is holding 100 - 150 grams of moisture which is probably possible especially in a car environment but not likely. As I showed (technically as MJK showed), even cavities with shallow depth can have a large effect on impedance (and the impedance curve directly affects t/s parameters that are derived from it). In fact this cavity loading is the whole basis of his work with OB U and H baffles.
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Just for fun, and since most people don't have MJK's worksheets, I recreated MJK's Alpha 15A H frame project in Hornresp. This is something anyone with Hornresp can do so there's no excuse for anyone here to not know about how cavities affect impedance. And simulating U frames is even easier.
Assuming I did all the unit conversions right, this is what it looks like. The Alpha 15A in a 15 inch deep H frame, with a 7.5 inch cavity to the front and a 7.5 inch cavity to the rear. This is a VERY shallow cavity and look at the effect on impedance. Not quite as much effect as MJK's worksheet shows but still a huge effect that will have a huge subsequent effect on t/s parameters if they are derived from this curve.
The blue line shows the 7.5 inch depth cavities as per MJK's project.
The red line shows the cavities reduced to .1 cm, effectively eliminating the cavities.
Power level and "miniscule cone movement" makes no difference.
I am fully aware that this is different than what Mark measured (both the driver and the boundary dimensions) but this is a quick and easy way to show that the measurement environment is VERY important.
It's not appropriate to measure t/s parameters in a car, and insisting that opening the doors and trunk will produce the same results as the normal procedure of measuring a driver is ridiculous.
Assuming I did all the unit conversions right, this is what it looks like. The Alpha 15A in a 15 inch deep H frame, with a 7.5 inch cavity to the front and a 7.5 inch cavity to the rear. This is a VERY shallow cavity and look at the effect on impedance. Not quite as much effect as MJK's worksheet shows but still a huge effect that will have a huge subsequent effect on t/s parameters if they are derived from this curve.
The blue line shows the 7.5 inch depth cavities as per MJK's project.
The red line shows the cavities reduced to .1 cm, effectively eliminating the cavities.
Power level and "miniscule cone movement" makes no difference.
I am fully aware that this is different than what Mark measured (both the driver and the boundary dimensions) but this is a quick and easy way to show that the measurement environment is VERY important.
It's not appropriate to measure t/s parameters in a car, and insisting that opening the doors and trunk will produce the same results as the normal procedure of measuring a driver is ridiculous.
An externally hosted image should be here but it was not working when we last tested it.
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I gotta ask, how about woofertester.com ?
The cheap version of your WTPRO.
Is that good enough to base a design om?
Yes sir it is an awesome little box.
Exceedingly accurate.
And it is the test gear I recommend to all people I work with that do not have test gear.
The WT2 from Smith and Larson is the best bet for a ready made solution on a budget, at least until DATS v2 gets enough feedback. The original WT3 and DATS had some serious issues, but I've never read about it being inaccurate or inconsistent. If the DATS v2 solves the issues with the original unit it will be a much cheaper alternative to the WT2 and it's plenty accurate.
But if you want to diy and save some money you can build a jig for LIMP (ARTA) for about $2, all you need is a couple of 3.5 mm jacks and a resistor. And if you don't have a line in on your computer you can use a $10 USB sound card. That's what I have now and it works fine. There are lots of people using this inexpensive solution and it does allow you to measure straight from the soundcard output for low level measurements or insert an amp in the chain for high power measurements. This is something you can't do with some of the other devices listed.
Don't let Mark fool you, you don't need fancy equipment. You just need to know what you are doing.
This would include avoiding making stupid mistakes like measuring t/s parameters in a car.
Clearly Mark does not want to comment now that I've provided what I consider to be irrefutable evidence that even very small and shallow cavities can cause serious problems with the impedance curve, but that's understandable. At this point he's been defending this silly mistake for months; he will be unable to admit this mistake at this late date and that's fine as long as it is understood that it is not appropriate to test t/s parameters in a car. I don't want other people thinking this is ok and posting up their own bad data from measurements done in inappropriate conditions. It's hard enough trying to find reputable data we don't need garbage data published from people that don't know what they are doing.
Make no mistake, you do need an appropriate open environment for testing drivers. You do NOT need fancy expensive equipment.
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We've now had the new Artisan system in place for about two weeks. I'm generally pleased with the results. But that is not to say things are perfect.
A particularly vexing problem is with the bass line - particularly in the digital 16 foot pedal ranks. Sympathetic vibrations are beginning to occur around 32 - 40 Hz. The noise continues for some individual notes down to 16 Hz. The pipes in their individual windchests seem to be vibrating - creating an unpleasant buzzing noise. These lower sounds are, of course, produced by some of the 32 foot ranks I've tried.
The bass speakers reproducing these ranks are the two homemade boxes I built. I'm still trying to double check that the speaker cabinets are not the sources of the buzzing. Rattles are not uncommon for such large cabinets, though I don't think that is the source for this noise. I can't rule it out completely. But I'm trying to eliminate noise in all areas.
But I'm currently looking for ways to isolate vibrations of these cabinets from the floor of the pipe/speaker chamber. The windchests sit on this same floor with no isolation between the floor and the chests. Clearly, the metal pipes can vibrate in their wooden windchests. The toe (bottom) of such pipes are typically simply set down into the aperture where the valve is located. No mechanical "lock" holds the pipe firmly in place. So vibration between the toe and the wood can easily occur.
I obtained some foam from an old King sized waterbed mattress. It is just under three inches thick. My thinking is to use this foam as a cushion between the speaker cabinet and the floor. The triangular cabinet weighs well over 100 pounds. This isn't particularly dense foam. Think in terms of foam between one's body and the support tubes of a waterbed. One layer of the foam is hardly enough cushion to create a lot of isolation. But I don't have unlimited space above head to put in multiple layers of the foam, though the weight of the cabinet will compress the foam considerably. I've got far more headroom over the bass cabinet with the two 15 inch Dayton drivers. I'm experimenting to figure out which cabinet is causing more of the vibrations.
It's also possible that the intense standing waves being produced are contributing to some of the sympathetic vibrations. But I'm trying to focus first on direct contact vibrations emanating from the floor. This is the thorniest issue I'm experiencing with our sound package.
I'd be very interested in any ideas others have used for similar cabinet/floor vibration isolation in their setups.
Most of the Artisan samples we received are blending pretty well with the Estey pipes. I believe most of our samples are from Aeolian Skinner organs. These sounds seem similar in "style" - at least to my ear.
Bach On
A particularly vexing problem is with the bass line - particularly in the digital 16 foot pedal ranks. Sympathetic vibrations are beginning to occur around 32 - 40 Hz. The noise continues for some individual notes down to 16 Hz. The pipes in their individual windchests seem to be vibrating - creating an unpleasant buzzing noise. These lower sounds are, of course, produced by some of the 32 foot ranks I've tried.
The bass speakers reproducing these ranks are the two homemade boxes I built. I'm still trying to double check that the speaker cabinets are not the sources of the buzzing. Rattles are not uncommon for such large cabinets, though I don't think that is the source for this noise. I can't rule it out completely. But I'm trying to eliminate noise in all areas.
But I'm currently looking for ways to isolate vibrations of these cabinets from the floor of the pipe/speaker chamber. The windchests sit on this same floor with no isolation between the floor and the chests. Clearly, the metal pipes can vibrate in their wooden windchests. The toe (bottom) of such pipes are typically simply set down into the aperture where the valve is located. No mechanical "lock" holds the pipe firmly in place. So vibration between the toe and the wood can easily occur.
I obtained some foam from an old King sized waterbed mattress. It is just under three inches thick. My thinking is to use this foam as a cushion between the speaker cabinet and the floor. The triangular cabinet weighs well over 100 pounds. This isn't particularly dense foam. Think in terms of foam between one's body and the support tubes of a waterbed. One layer of the foam is hardly enough cushion to create a lot of isolation. But I don't have unlimited space above head to put in multiple layers of the foam, though the weight of the cabinet will compress the foam considerably. I've got far more headroom over the bass cabinet with the two 15 inch Dayton drivers. I'm experimenting to figure out which cabinet is causing more of the vibrations.
It's also possible that the intense standing waves being produced are contributing to some of the sympathetic vibrations. But I'm trying to focus first on direct contact vibrations emanating from the floor. This is the thorniest issue I'm experiencing with our sound package.
I'd be very interested in any ideas others have used for similar cabinet/floor vibration isolation in their setups.
Most of the Artisan samples we received are blending pretty well with the Estey pipes. I believe most of our samples are from Aeolian Skinner organs. These sounds seem similar in "style" - at least to my ear.
Bach On
... and what I use is... (esp for wrapping things like dishwashers that are noisy beasts instead of the nearly useless 50-cents stuff that comes with "deluxe" models for $150 extra)...
heat insulation composed of a ⅛-inch rubber gooey sticky layer and a heavy aluminum foil cover. Comes in rolls with widths to a foot wide. That stuff really deadens vibrations. Don't know if your local stores have the same insulation riches as Canadian stores at this time of year.
There's also stuff used on car hoods although not as perfect to use as the heat insulation stuff.
There's also cartridges of the rubber goo for temporary caulking we talked about earlier.
Ben
heat insulation composed of a ⅛-inch rubber gooey sticky layer and a heavy aluminum foil cover. Comes in rolls with widths to a foot wide. That stuff really deadens vibrations. Don't know if your local stores have the same insulation riches as Canadian stores at this time of year.
There's also stuff used on car hoods although not as perfect to use as the heat insulation stuff.
There's also cartridges of the rubber goo for temporary caulking we talked about earlier.
Ben
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Yes. Better foam might be better.
I've also had someone suggest that I use a partially filled tire inner tube for the corner cabinet. If nothing else, it would allow me to inflate the tube to lift the cabinet up. Then the foam could be squeezed in between the raised cabinet bottom and the floor. Then the tube could be deflated to see how much the foam has compressed. The tube could then be removed.
A plan B is that the tube could be tried as the primary cushion between the cabinet and the floor. I'm just concerned about leaks occurring over time and causing the tube to deflate. Earlier, someone had suggested using tennis balls as cushioning "feet" placed in furniture leg carpet cups. But I have the same concern about air deflation with that method.
Anyone have any sage observations on either of these ideas?
BO
I've also had someone suggest that I use a partially filled tire inner tube for the corner cabinet. If nothing else, it would allow me to inflate the tube to lift the cabinet up. Then the foam could be squeezed in between the raised cabinet bottom and the floor. Then the tube could be deflated to see how much the foam has compressed. The tube could then be removed.
A plan B is that the tube could be tried as the primary cushion between the cabinet and the floor. I'm just concerned about leaks occurring over time and causing the tube to deflate. Earlier, someone had suggested using tennis balls as cushioning "feet" placed in furniture leg carpet cups. But I have the same concern about air deflation with that method.
Anyone have any sage observations on either of these ideas?
BO
Hi Bach On,
You may just be looking at acoustic coupling, when you energize a room with very low frequency acoustic energy everything that can will rattle.
As to vibration damping, multi-layer suspensions have worked for me, e.g.: a sandwich of a layer of carpet, a thin layer of wood (e.g.: OSB) and a layer of dense foam might work below the cabinets (you don't need to use the full contact surface, pads will do). Also, make sure that the cabinets are not rattling against the walls.
As to the insertion point of the pipes into the windchests, maybe some thin felt to take up any slack?
Regards,
You may just be looking at acoustic coupling, when you energize a room with very low frequency acoustic energy everything that can will rattle.
As to vibration damping, multi-layer suspensions have worked for me, e.g.: a sandwich of a layer of carpet, a thin layer of wood (e.g.: OSB) and a layer of dense foam might work below the cabinets (you don't need to use the full contact surface, pads will do). Also, make sure that the cabinets are not rattling against the walls.
As to the insertion point of the pipes into the windchests, maybe some thin felt to take up any slack?
Regards,
Two Kinds
of rattling:
1) that induced by acoustic energy transmitted through the woofer enclosure
Solutions:
a) use two drivers operated in opposition to each other in the same enclosure, i.e. >[]<
b) suspend units from the ceiling on cables
c) place enclosure on a resilient base (here compression from the weight of the enclosure becomes a problem).
2) that induced by acoustic energy transmitted through the air.
Any object with a large surface (force multiplier) is going to move, and if it slaps up against one of a much smaller surface, you are going to hear "buzzing/rattling".
Solutions:
a) Anchor them together
b) Place a resilient material between them
c) Remove the smaller Item
Hope this helps.
WHG
of rattling:
1) that induced by acoustic energy transmitted through the woofer enclosure
Solutions:
a) use two drivers operated in opposition to each other in the same enclosure, i.e. >[]<
b) suspend units from the ceiling on cables
c) place enclosure on a resilient base (here compression from the weight of the enclosure becomes a problem).
2) that induced by acoustic energy transmitted through the air.
Any object with a large surface (force multiplier) is going to move, and if it slaps up against one of a much smaller surface, you are going to hear "buzzing/rattling".
Solutions:
a) Anchor them together
b) Place a resilient material between them
c) Remove the smaller Item
Hope this helps.
WHG
Like other aspects of acoustics, often people have poor intuitions about how to deal with vibration isolation and damping.
For a big object you want to isolate from a floor, you pretty much have to think in terms of springs. Not big car-suspension like things, but something springy between the object and the floor. Once you find a source for springs, it will be easy to get what you need.
Ben
For a big object you want to isolate from a floor, you pretty much have to think in terms of springs. Not big car-suspension like things, but something springy between the object and the floor. Once you find a source for springs, it will be easy to get what you need.
Ben
Try foam rubber balls.
Most of the isolation benefits with none of the deflation detriments.
All the other advice is spot on.
I agree with Oliver that the coupling may very well be acoustic. If that be the case then you are pretty much getting what would happen in an organ with the same tonal output.
Most of the isolation benefits with none of the deflation detriments.
All the other advice is spot on.
I agree with Oliver that the coupling may very well be acoustic. If that be the case then you are pretty much getting what would happen in an organ with the same tonal output.
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