Paul W said:
thats a tough one - more a product of experimentation for a particular driver. (lower mass drivers need more attention to this than higher mass drivers, but this isn't neccesarily a product of "stuffing" proximity.) Ideally there wouldn't be any "stuffing" - but this of course causes other problems. Fostex has a solution to this in the form of reflectors (to de-corelate the reflections and lower their "time"). I believe the better solution is absorption without significant "drag" from this (especially on the driver's frame):
http://www.hytechsales.com/insulating_paint_additives.html
there isn't any information on this subject that I'm aware of. However many people have noticed this phenomon, including designers as respected as S. Linkwitz (..under the stored engery section of #3 on the "Loudspeaker" page of Linkwitzlabs.com).
Because of the mass issue (for a given sd), fullrange driver are typically more suseptible to this (because all else equal - they have less mass for a given sd). Additionally they have suspensions that typically provide lower initial resistance than normal Hi-Fi drivers (after the driver's been thouroughy "broken-in"), and because of this the effect it can be even more noticible. So you are likely to find a greater percentage of "posts" on this problem in the fullrange section.
Now it may not be a cause for concern at all in a particular "acoustic resistance" design IF the resistance portion is soley a function of "stuffing" the aperiodic holes in the cabinet and not as cabinet filler or applied to the driver itself.
Did I understand you wrong or are you suggesting that cabinet stuffing is the "acoustic resistance" that makes driver lifeless?
Jussi
Jussi
Jussi said:
Yes and no.. 😀
yes, cabinet stuffing can (often) make a driver sound "lifeless".
no, that the acoustic resistance design neccesarily implies utiilizing it. For instance a traditional aperiodic vent does not have "stuffing" spilling out into the cabinet, rather JUST the vent has stuffing (and of course in a traditional design it has a rather dense application of stuffing).
David Gatti said:
I checked up those Peak Consult, Sonus Faber and Rockport reviews in Stereophile. Good reviews, all of them propably very good speakers. All of them got very good ratings from their dynamics so AT talk about acceleration factor, highish efficiency and 2" coils sounds accurate. I think Dynaudio is also relying to same things and why shouldn't they, both are founded by same persons and that way same methology.
Sonus Faber Extrema didn't have that smooth and stable response and that's why I'm a bit allergic to 1st order filters. At least between mid and tweeter. And if midrange is dipole 1st order aka no electrical highpass isn't that smart between woofer and midrange as well.
Darn. This SS-AT-Esotar combination doesn't feel that dumb option. AT-Esotar combinations seemed to create pretty nice speakers so I guess it's possible for me too. And adding SS there shouldn't make things that much worse...
AT seems to use pretty stiff suspension in their products. For example 5" and 7" C-Quenze models have stiffer suspensions compared to same size Seas models. Personally I'd like that Scan Speak low loss approach but I don't know is combining AT with low loss is a good idea. I'll have to check things from Per and find out do they test their drivers thoroughly and make sure they don't have major flaws because what customer desired.
Jussi
Jussi said:
Not a "dumb" option at all (even considering the added expense)..
Of them all I think I like the lower limit (the midranges highpass charcter) on the Verity Audio Sarastro:
http://www.stereophile.com/loudspeakerreviews/305verity/index.html
Notice that the "7" inch driver does NOT appear to be a flex unit (no double screws) - therefore I'd have to conclude that its a c-quenze.
Ah, one more AT commercial. Underhung motor, 93dB efficient, I'd say it's pretty well customized. To me Per told they can't make underhung drivers that efficient.
150Hz would be fine but not without any baffle or cabinet. Efficiency runs out. 300-350Hz, 2nd should be fine, could try 1st.
Sadly my wife would prefer the MTM standmodel. Looks dull, normal box and not so much I can do about it. Crap. I'd like to use some creative thinking to speakers appearance, they don't have to look like dull black boxes like the stereotype.
Jussi
150Hz would be fine but not without any baffle or cabinet. Efficiency runs out. 300-350Hz, 2nd should be fine, could try 1st.
Sadly my wife would prefer the MTM standmodel. Looks dull, normal box and not so much I can do about it. Crap. I'd like to use some creative thinking to speakers appearance, they don't have to look like dull black boxes like the stereotype.
Jussi
yup there are financial constraints...
and then there are the even more onerous spousal constraints..
😀
and then there are the even more onerous spousal constraints..
😀
Well I don't feel this 2-way + stereosubs basic principle to be any inferior than this 3-way idea. 2x7" MTM with Esotar gives pretty much best performance from both drivers and separated woofersystem gives nice adjusting potential. Single 18" per side is also a helluva lot more than 2x25W.
But still I don't like normal boxes. Does anyone have great visions how to make a 2x7" MTM standspeaker (with integrated stand perhaps) without following this normal box trend?
Jussi
But still I don't like normal boxes. Does anyone have great visions how to make a 2x7" MTM standspeaker (with integrated stand perhaps) without following this normal box trend?
Jussi
Can anyone name me few good reasons why to pick C2-95/11 Accuton over W18EX Seas? Don't consider price.
W18 is more efficient, from manufacturers specs it has lower distorsion, basket is much more open...
Jussi
W18 is more efficient, from manufacturers specs it has lower distorsion, basket is much more open...
Jussi
Progress..
Got myself prototype cabinets. They can hold twin 18cm Seas mids and waveguided tweeter. Already tried the Esotars in waveguide and seems to be working. Just need to measure some distorsions to make sure later...
As for mids I invested pair of Seas W18. Some acoustic resistance developing should follow...
But I'd need some good suggestions how to handle the bass. Below say 150-200Hz or so. In theory 2xW18 could handle 80Hz in AR cabinet but it's very propably just stretching it causing nonlinear behavior in AR, distorsion and limited SPL capacity for the mids.
So, flat baffle with stack of 12" woofers on it, maybe a ripole design?
Jussi
Got myself prototype cabinets. They can hold twin 18cm Seas mids and waveguided tweeter. Already tried the Esotars in waveguide and seems to be working. Just need to measure some distorsions to make sure later...
As for mids I invested pair of Seas W18. Some acoustic resistance developing should follow...
But I'd need some good suggestions how to handle the bass. Below say 150-200Hz or so. In theory 2xW18 could handle 80Hz in AR cabinet but it's very propably just stretching it causing nonlinear behavior in AR, distorsion and limited SPL capacity for the mids.
So, flat baffle with stack of 12" woofers on it, maybe a ripole design?
Jussi
Scott,
Do you have experience of ripole bass solution? How deep structure could I use to have desired 150Hz top extension? Cross can and propably even has to be steep.
Linkwitz used 490mm deep W-baffle in his Phoenix design and that seems to extend up to 120Hz or so with steep crossover. Phoenix has 2nd order 100Hz with notch filter on it. 120/150 would make 80% which is about 400mm from 490mm but that feels pretty deep structure. Something around 350mm which could hold 12" woofers in there perhaps?
Single ripole on each layer makes pretty narrow appearance. Personally I'd like narrow and deep structure over the 1:1 cube two drivers in each layer would lead.
Jussi
Do you have experience of ripole bass solution? How deep structure could I use to have desired 150Hz top extension? Cross can and propably even has to be steep.
Linkwitz used 490mm deep W-baffle in his Phoenix design and that seems to extend up to 120Hz or so with steep crossover. Phoenix has 2nd order 100Hz with notch filter on it. 120/150 would make 80% which is about 400mm from 490mm but that feels pretty deep structure. Something around 350mm which could hold 12" woofers in there perhaps?
Single ripole on each layer makes pretty narrow appearance. Personally I'd like narrow and deep structure over the 1:1 cube two drivers in each layer would lead.
Jussi
Jussi said:
Sorry, no experience.. I was just thinking about your desire for more restrictive dispersion. (..plus they look cool.)
If you want something narrow and deep then consider a "U" baffle with a honeycomb path/interior.
If you wanted something that was just plain "easier" and narrow/deep.. then consider JohnK's CRAW.
http://www.musicanddesign.com/craw.html
Member
Joined 2003
Hi Jussi,
Good to hear you are making progress with your project.
I have been thinking about a project with an XO of 150 Hz, or maybe a little higher. The ripole is one alternative, but I don't care for the back-front path length differences with a relatively high crossover frequency.
The current idea is similar to what Scott suggests...a 15" metal cone with high breakup frequency, shorting rings etc, in a short U-baffle only about the size of the driver. The backwave sent through a wool felt pad suspended tightly between two plastic light grids or some other rigid but open material.
Paul
Good to hear you are making progress with your project.
I have been thinking about a project with an XO of 150 Hz, or maybe a little higher. The ripole is one alternative, but I don't care for the back-front path length differences with a relatively high crossover frequency.
The current idea is similar to what Scott suggests...a 15" metal cone with high breakup frequency, shorting rings etc, in a short U-baffle only about the size of the driver. The backwave sent through a wool felt pad suspended tightly between two plastic light grids or some other rigid but open material.
Paul
Paul,
That sounds like a AR experiment. Some builders in Finland have succesfully done such systems. Even high rear cancellations are possible to achieve but as for damping room modes it's better to stay in hypercardioid radiation pattern. This means about 15dB cancellation to rear as well to 90 degree angles. Should be even better than a dipole. True cardioid doesn't have that much cancellation to sides which leaves couple room modes alive. This also means more AR load which can lead to non-linear resistance behavior at bass range.
With midrange AR isn't a problem. Normal sheetcloth is stable enough but for bass it needs to be stiffer. Normal cloth starts to move and causes problems.
I've also thought of this AR bass solution. I should propably build a prototype and test it. Maybe stack a regular 10" driver on it and have a look. At least it's very intresting field to try. Most or even all of these already build systems aren't that well tested as far as I know. Works but I like to know how well. So such proto could visit a anechoic chamber and have some punishment. AR testing is pretty simple. Just hit more gain and see how cancellations to different directions handle it. If off axis responses starts to twinkle or collapse there starts to be problems with the resistance.
And as for the overall solution AR collapse isn't a good thing. It can lead to more dipolar radiation pattern when levels rise which causes more reflections from front wall which eats off front radiation (like good old dipole) and causes visious circle. So testing how it handles at different levels is important. Can it for example play at normal levels and handle dynamic peaks without collapsing the radiation pattern at those peaks and so on. Distorsion is another thing...
At least AR cabinet is a cabinet. It's easier to build rocksolid than some open structure dipole.
Jussi
That sounds like a AR experiment. Some builders in Finland have succesfully done such systems. Even high rear cancellations are possible to achieve but as for damping room modes it's better to stay in hypercardioid radiation pattern. This means about 15dB cancellation to rear as well to 90 degree angles. Should be even better than a dipole. True cardioid doesn't have that much cancellation to sides which leaves couple room modes alive. This also means more AR load which can lead to non-linear resistance behavior at bass range.
With midrange AR isn't a problem. Normal sheetcloth is stable enough but for bass it needs to be stiffer. Normal cloth starts to move and causes problems.
I've also thought of this AR bass solution. I should propably build a prototype and test it. Maybe stack a regular 10" driver on it and have a look. At least it's very intresting field to try. Most or even all of these already build systems aren't that well tested as far as I know. Works but I like to know how well. So such proto could visit a anechoic chamber and have some punishment. AR testing is pretty simple. Just hit more gain and see how cancellations to different directions handle it. If off axis responses starts to twinkle or collapse there starts to be problems with the resistance.
And as for the overall solution AR collapse isn't a good thing. It can lead to more dipolar radiation pattern when levels rise which causes more reflections from front wall which eats off front radiation (like good old dipole) and causes visious circle. So testing how it handles at different levels is important. Can it for example play at normal levels and handle dynamic peaks without collapsing the radiation pattern at those peaks and so on. Distorsion is another thing...
At least AR cabinet is a cabinet. It's easier to build rocksolid than some open structure dipole.
Jussi
Paul W said:
I responded to this once before on this thread.. since then another member has observed similar problems with stuffing:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=75940&pagenumber=2
Member
Joined 2003
Jussi,
Yes, it is AR, but the main intention is to damp pipe resonance of the U-baffle. In this particular case, cardiod is second priority.
The room is very large and the layout has been "rotated" 90 degrees to provide longer distance to walls...wall interaction is now very low and well balanced. Unfortunately 90 degree rotation placed large speakers in front of large windows and the speakers block the view! So, I have been instructed to "make something smaller".
U-baffle seems to be the most compact OB with forward facing driver (I may want to push xo as high as 200). 45 degree wings would be better, but baffle would be too large visually. However, U's do resonate and I would rather fix resonance at the source than electrically EQ it.
Do you have any photos of your prototypes or are they not representative of what you are thinking for your final design?
Scott,
The baffle I'm thinking of would also be the base for the upper range drivers so it would be 12-16" deep for physical stability. The acoustic "filter" would close the end of the pipe, so no resistance near the driver. I was listening the last time you mentioned this.
Paul 😉
Yes, it is AR, but the main intention is to damp pipe resonance of the U-baffle. In this particular case, cardiod is second priority.
The room is very large and the layout has been "rotated" 90 degrees to provide longer distance to walls...wall interaction is now very low and well balanced. Unfortunately 90 degree rotation placed large speakers in front of large windows and the speakers block the view! So, I have been instructed to "make something smaller".
U-baffle seems to be the most compact OB with forward facing driver (I may want to push xo as high as 200). 45 degree wings would be better, but baffle would be too large visually. However, U's do resonate and I would rather fix resonance at the source than electrically EQ it.
Do you have any photos of your prototypes or are they not representative of what you are thinking for your final design?
Scott,
The baffle I'm thinking of would also be the base for the upper range drivers so it would be 12-16" deep for physical stability. The acoustic "filter" would close the end of the pipe, so no resistance near the driver. I was listening the last time you mentioned this.
Paul 😉
Paul,
I don't have any photos of them. Nothing that special. AR grilles on the sides, triangle shape cabinet cavity and so on.
Still I haven't found proper bass solution for it. Got a fine idea of stacking six 12" Peerless SLS drivers into a straight baffle and bolt those to sidewalls but seems like such placement isn't possible and also contains very low WAF rating.
Darn.
Jussi
I don't have any photos of them. Nothing that special. AR grilles on the sides, triangle shape cabinet cavity and so on.
Still I haven't found proper bass solution for it. Got a fine idea of stacking six 12" Peerless SLS drivers into a straight baffle and bolt those to sidewalls but seems like such placement isn't possible and also contains very low WAF rating.
Darn.
Jussi
Paul W said:
🙂
..the only reason I posted the addition is that it helps to have someone else to confirm the problem - otherwise its just me blowing "cheese". 😀 (..also I think I did a better job explaining the subjective effect this time than last, which could be helpful.)
Note: I actually prefer a dipole (forward directed U baffle) in the 70-300 Hz range, and it isn't just about free-air operation benefits (i.e. low air resistance, reflections, and compression that a true IB would offer). There is something "right" about this bandwidth for dipole operation over even cardoid and hyper cardoid. When you start going further into the bass region though - cardoid/hypercardoid seems to be better. Freq.s lower than 35 Hz (for all but the largest rooms) are best served by monopole operation. Again though, thats my "current" view.
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