Yes, I suppose the term comes from "voila"🙄, but not speaking French I didn't put that together.
The magnet vibrate against the frame and I would not want to couple that vibration into the enclosure, although in some cases it might tame this resonance being the worse problem. In older ceramic drivers this was a problem, in the newer ones with neo, it is not.
The obvious point is the exact center of the box - or close to it. I found that the longer members - to the top and base - were not worthwhile and those were the smallest panels. The front-back and side-side are the most effective and the largest panels (in my case!!)
if a magnet is vibrating against the frame i would view that as a faulty driver and i've encounter that sort of thing more with stamped frame drivers then cast frame drivers.
part of the reason i asked is i once had occasion to work with a Turbosound rig that had a support structure for the driver magnets which i thought was more for mechanical support (PA stuff can have a ruff life) but after a lengthy discussion with a company rep was told it has a twofold approach mechanical support and vibration damping,so yeah i'm kind of unclear as to why attaching or supporting the mass of magnet isn't considered a benefit doesn't additional mass counter vibration?
part of the reason i asked is i once had occasion to work with a Turbosound rig that had a support structure for the driver magnets which i thought was more for mechanical support (PA stuff can have a ruff life) but after a lengthy discussion with a company rep was told it has a twofold approach mechanical support and vibration damping,so yeah i'm kind of unclear as to why attaching or supporting the mass of magnet isn't considered a benefit doesn't additional mass counter vibration?
Most of our designs brace the magnet against at least 3 sides. It works well.
http://p10hifi.net/FAL/downloads/CGR-MarKen103p-plan-040414.pdf
dave
http://p10hifi.net/FAL/downloads/CGR-MarKen103p-plan-040414.pdf
dave
Helpful, thank you.
For what it's worth, the enclosure type I was describing was a resonant one (a pipe, which suits a driver I have) where the extensions would travel either side against the room walls to conserve space.
I've reasoned thus far that the near driver walls can be consolidated into a reasonably compact chamber with a sensible local ground point, and the extensions can be made with their own local grounds and be loosely coupled to the main section, where physical displacement/movement between the sections will produce a result fairly superfluous to the operation of the enclosure, and only panel resonance itself would seem to be of interest.
Mark Dodd designs (that includes the old Tannoys as well as the LS50) usually have a brace close to the back of the driver with a dollop of damping material between backplate and brace.
The LS50 looks a lot like the old Tannoy DMTs in detail.
Copious bracing in foam core is key to keeping a lightweight box that doesn't buzz. Here is a dual driver 6th order series band pass sub.
http://www.diyaudio.com/forums/full-range/268524-xki-xs-ab-initio-karlson-6th-order-bandpass-26.html
http://www.diyaudio.com/forums/full-range/268524-xki-xs-ab-initio-karlson-6th-order-bandpass-26.html
Measurements measurements measurements
Build a box well using the drivers parameters in the design. Make sure it doesn't leak, vibrate etc. Play music. If you like it, even enjoy it, then carry on enjoying it.
If not try again. Just don't worry too much about measurements. Measurements can't confirm if it will sound nice to your ears.
So build sensibly and play music
Build a box well using the drivers parameters in the design. Make sure it doesn't leak, vibrate etc. Play music. If you like it, even enjoy it, then carry on enjoying it.
If not try again. Just don't worry too much about measurements. Measurements can't confirm if it will sound nice to your ears.
So build sensibly and play music
Theorically speaking : does the best material is the one which can't transmit the sound by vibration ? E.g. : steel : very bad idea as it's transmit the sound very fastly?
But what is the part of sound radiation coming from the cabinet external walls and the one coming back from inside the cabinet through the rear of the cone towards the external (front of the cone) ?
I assume a part of the internal volume acts as a spring in a sealed load... but a part of the waves which come back towards the rear cones are enough powerfull to go through it ? Are ther etwo signal out of phase coming from the cone ? The wave created by the mvt of the cone + a rear wave coming through the cone with less energy (loss) ?
Is it just acoustic suspension vs Infinite load ? (in any cas : the stiffer the cone the better ? (and the cabinet vibration behavior of a less importance ?)
Ah, I can say something usefull about "Voilà !" : in english I believe the best way to say this is Vou-a-la (like the "v" of Viper in shorter, not Wagon ! Example : "Vive la Reine" and not "Wife la Reine" as Henri VIII said at the court as he spoke french and also saxon...)
But what is the part of sound radiation coming from the cabinet external walls and the one coming back from inside the cabinet through the rear of the cone towards the external (front of the cone) ?
I assume a part of the internal volume acts as a spring in a sealed load... but a part of the waves which come back towards the rear cones are enough powerfull to go through it ? Are ther etwo signal out of phase coming from the cone ? The wave created by the mvt of the cone + a rear wave coming through the cone with less energy (loss) ?
Is it just acoustic suspension vs Infinite load ? (in any cas : the stiffer the cone the better ? (and the cabinet vibration behavior of a less importance ?)
Ah, I can say something usefull about "Voilà !" : in english I believe the best way to say this is Vou-a-la (like the "v" of Viper in shorter, not Wagon ! Example : "Vive la Reine" and not "Wife la Reine" as Henri VIII said at the court as he spoke french and also saxon...)
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Edam
While I do not deny that some amount of sound comes back through the cone, I do deny that it is significant. I have tried to measure this as well and could not find it. It will, of course, differ significantly with the cone thickness etc. I like and use heavy cone speakers, so maybe that's why I can't measure it.
Steel would be good for transmission, but not so good for internal standing waves - which are significant and can be measured if bad enough. Not so if the cabinet is well damped inside.
A sealed volume is acoustically a spring and this is what the rear wave does - this is already accounted for in the total radiation as a lowering of output due to wave cancellation effects from the box back onto the cone - which also results in the apparent added stiffness to the cone.
While I do not deny that some amount of sound comes back through the cone, I do deny that it is significant. I have tried to measure this as well and could not find it. It will, of course, differ significantly with the cone thickness etc. I like and use heavy cone speakers, so maybe that's why I can't measure it.
Steel would be good for transmission, but not so good for internal standing waves - which are significant and can be measured if bad enough. Not so if the cabinet is well damped inside.
A sealed volume is acoustically a spring and this is what the rear wave does - this is already accounted for in the total radiation as a lowering of output due to wave cancellation effects from the box back onto the cone - which also results in the apparent added stiffness to the cone.
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In my experience, I have seen speakers that don't measure well, sound subjectively good with some genres or tracks. But a speaker that measures well, will almost be guaranteed to sound good with almost all music genres. Measuring well means a relatively flat frequency response, relatively low HD, clean impulse response. The thing that sets apart a good from a great speaker, polar response smoothness, good timing accuracy and ability to produce a right triangle step response, and ability to have wide dynamic range.
Thanks for the hints.
It should be tricky to measure a cone ! Laser tools ?
Btw, when in the Dickason book we read the measurement of two cabinets with different material & thickness (he shows a Fourier transform for each cabinet iirc), I always asked what was the technic to supress the cone measurement from the cabinet (or did he measure simply the whole combo each time : cabinet + same drive and made a soustraction of the raw driver measurement at the same place ????).
Or maybe an accelerometer tools can do it ?
Yes you converted me to the importance of a thicker cone with the Summa (a big 150 g if I remember). And when I look at the catalog of the good PHL Audio PA drivers which here are not more expensive than others : I see the ones rated "Excellent sounding" have the two sides of the cones damped by an acrylic "resine"... not only the front side as the majority of the line. The result is the a x2 of the Mms !
It should be tricky to measure a cone ! Laser tools ?
Btw, when in the Dickason book we read the measurement of two cabinets with different material & thickness (he shows a Fourier transform for each cabinet iirc), I always asked what was the technic to supress the cone measurement from the cabinet (or did he measure simply the whole combo each time : cabinet + same drive and made a soustraction of the raw driver measurement at the same place ????).
Or maybe an accelerometer tools can do it ?
Yes you converted me to the importance of a thicker cone with the Summa (a big 150 g if I remember). And when I look at the catalog of the good PHL Audio PA drivers which here are not more expensive than others : I see the ones rated "Excellent sounding" have the two sides of the cones damped by an acrylic "resine"... not only the front side as the majority of the line. The result is the a x2 of the Mms !
Let's assume there is no measurement error.
If I build a new foam core horn and before applying CLD, take frequency response, and measure RTA to show HD at various frequency locations indicated in the FR, you are saying that I should see broadband noise, and not spectral peaks and harmonics? Then I apply the CLD, this broadband noise goes away due to reduced panel vibrations, then see HD values go down.
If however, with the no-CLD case does not show broadband noise under sine wave excitation, but instead shows harmonic content which is then reduced after CLD is applied then my measurement and interpretation is correct?
Take out "relatively low HD" and I can agree completely. "HD" has no single number level definition on which to make any judgments. THD, as a measurement metric, is weakly negatively correlated with perception, i.e. higher THD is rated better. But not significantly. No linear measure of nonlinear distortion has ever shown a correlate to loudspeaker audibility. Toole and Olive discount it completely (which I don't do). But the point is that you cannot tell me at what point a speaker has inaudible "relatively low HD". The tests that I have done strongly suggest that nonlinearity is a loudspeaker need not be audibly significant if just a few things are tended to. Comparing two sets of loudspeakers based on any measure of nonlinearity is likely to be insignificant, certainly with THD.
Either "Measurement OR interpretation" is incorrect, yes, because you cannot show any theory by which such a thing is possible. And trust me, I am an expert in nonlinear dynamics, so not much theory is beyond me or unknown to me.
Can I please have a little primer or definition on what is linear and non linear distortion / dynamics in the systems we are talking about?
I can hear 3rd HD pretty easily and it doesn't sound good. Maybe I need to do a Subjective Blind Test thread with sound clips of HD audibility?
Do you have link to the peer reviewed publication for the above?
If I can show this:
What would be the interpretation?
Do you have link to the peer reviewed publication for the above?
If I can show this:
What would be the interpretation?