Ed Collier's Concave Rapide. More surface area for damping can be achieved by using this technique.
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That's a novel idea!
Clearly exotic interior shapes have more appeal than simply letting fiberglass do its job.
I haven't seen any response measuements that show that exotic shapes are better or that simple damping is inadequate.
David S
What is your opinion of minimal Qtc (or Qtc approaching Qts) designs - a large box and damping? Similar to an infinite baffle?
Toole has interesting information about irregular room shapes in "Sound Reproduction". He says that there are no real differences in the modal resonance structures between regular or irregular shapes. Just regular rooms are easier to work out mathematically!
Given that a loudspeaker enclosure is just a small scale room, it seems logical that it holds true for speakers too.
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Just came to me, how about a piece of automotive catalytic converter?
It has more holes than surface, it can be cut or milled in different shapes.
And I have read that there is a complete separate science for small pipes and smth like that... There was analogy with human body blood vessels, where the veins and artery pressure is far less than the one in capillary system.
The other thought is for spherical enclosure with dense rubber ball in the center, but that was already mentioned.
Maybe an enclosure connected to a sphere with short pipe or flange.
What about the compression chamber of horns? It is known that with it's volume the HF output is lost. How is it lost? Maybe a sphere loading through a chamber that doesn't transmit HF and mid energy properly?
It is known that amplitude is at maximum in the center of a sphere and at minimum at the borders, but how about past the borders through a flange and in the chamber connected to the sphere?
And here it is :lol: a fiber glass lined chamber connected through a flange with catalitic converter in it to a fiber glass lined, double tuned sphere with a rubber ball in the center. :lol:
That's my contribution
... while I remain unsure whether it will be more effective than simple connection to the sewer... cheers for that!
It has more holes than surface, it can be cut or milled in different shapes.
And I have read that there is a complete separate science for small pipes and smth like that... There was analogy with human body blood vessels, where the veins and artery pressure is far less than the one in capillary system.
The other thought is for spherical enclosure with dense rubber ball in the center, but that was already mentioned.
Maybe an enclosure connected to a sphere with short pipe or flange.
What about the compression chamber of horns? It is known that with it's volume the HF output is lost. How is it lost? Maybe a sphere loading through a chamber that doesn't transmit HF and mid energy properly?
It is known that amplitude is at maximum in the center of a sphere and at minimum at the borders, but how about past the borders through a flange and in the chamber connected to the sphere?
And here it is :lol: a fiber glass lined chamber connected through a flange with catalitic converter in it to a fiber glass lined, double tuned sphere with a rubber ball in the center. :lol:
That's my contribution
... while I remain unsure whether it will be more effective than simple connection to the sewer... cheers for that!
Hi Toshko,
Good translation via Google of your "home" website and your hard work - very impressive.
On your Crossover on post 8, what is the freq point and the dB/oct slope?
Plus could you explain/link for your use of the 10mH transformer/choke, please, and the purpose of the variable resistor on the secondary winding - most interesting.
I'm following in the path of the B&W and other previous deigners using the "tapered resistance" method of suppressing the backwave without exceesive damping of the cone - tricky, but good results with high efficiency, light cone drivers and particularly with extended transient signals.
The idea of the Catalytic converter "insides" as a diffuser/damper is interesting and there's a mention/post about the Nautilus 802 speakers, I think, that uses something similar.
I haven't great success with the Fibreglas 703 (above post 39) as an internal bass box damping material but perhaps it maybe better in a version of a "bass trap/diffuser"
Good translation via Google of your "home" website and your hard work - very impressive.
On your Crossover on post 8, what is the freq point and the dB/oct slope?
Plus could you explain/link for your use of the 10mH transformer/choke, please, and the purpose of the variable resistor on the secondary winding - most interesting.
I'm following in the path of the B&W and other previous deigners using the "tapered resistance" method of suppressing the backwave without exceesive damping of the cone - tricky, but good results with high efficiency, light cone drivers and particularly with extended transient signals.
The idea of the Catalytic converter "insides" as a diffuser/damper is interesting and there's a mention/post about the Nautilus 802 speakers, I think, that uses something similar.
I haven't great success with the Fibreglas 703 (above post 39) as an internal bass box damping material but perhaps it maybe better in a version of a "bass trap/diffuser"
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Pretty much. One just has to hope that given its size, the dispesion that high is sucj that little of relevance gets to the edge.
dave
Guys, a straight through auto muffler actually has fiberglass in it for sound damping, hence the term "glasspack".
Most people are using polyfill, but fiberglass seems to be a fair superior material for sound damping.
Going from polyester "damping" material to fiberglass should bring great improvement. Twaron "Angel Hair" (aramid fibers) should even be slightly better.
Right on both counts. A glass pack is not the most efficient (soundwise) muffler, but they are good for flow. Air conditioner ducts are made the same way, A perforated barrier around the main flow area lets sound leak into the surrounding fiberglass where it is absorbed. Note that most mufflers are tuned resonators of various types. They use tuning to create cancelation of the most annoying exhaust frequencies. Designers are also very aware of what a "good sounding" exhaust note is and tune accordingly. I have read a couple of motorcycle articles that directly state that dB reduction is proportional to weight and volume of the muffler. i.e., you can't get good attenuation with a small muffler.
We don't need to flow hot exhaust gasses in our loudspeakers (at least not the ones I've worked on!) so we can concentrate more on sound absorption and less on flow drag. Mufflers, glass packs and catalytic converters are all mediocre to poor in terms of the real sound absorption that we want in a speaker.
I've been stating for years that polyfil is a poor sound absorber. It will increase box apparent volume but it won't absorb standing waves to any degree. (Yes, I have tested it in cabinets.) I went looking for the sound absorption properties in the usual acoustics web sites but apparently it has never been tested since its absorption is so poor.
David S.
I know that fiberglass works great, but am worried about the health issues associated with it.
Polyester fiberfill may not be 'best', but it does the job, is cheap, and is much safer to use, especially for a vented box.
http://home.earthlink.net/~ralphmeister/subbox.htm
Polyester fiberfill may not be 'best', but it does the job, is cheap, and is much safer to use, especially for a vented box.
http://home.earthlink.net/~ralphmeister/subbox.htm
But in a forum where everyone is obsessing about absorbing the back wave, polyfill is not only not "the best" it is downright poor. It will not absorb standing waves.
If you don't like FG then try some of the recycled cotton felts made from scraps.
Health effects? FG is itchy but it is not known to be carcinogenic.
David S.
If you don't like FG then try some of the recycled cotton felts made from scraps.
Health effects? FG is itchy but it is not known to be carcinogenic.
David S.
From Elliot Sound
Volume filling a reflex box
"The above shows reflection, (red), and absorption (green) of 50mm polyester, approximately 25kg/m³. The peaks at 1 and 2kHz are due to standing waves in the test fixture. As can be seen the polyester fibre does not start to provide any really useful attenuation until around 1kHz, and then over the range we want we can expect no more than 10-15 dB with a typical 25mm covering at the standard density."
"Exactly as Robert describes here, one design in particular used an open cell foam to line the interior walls. Although the designer swears by it, the foam is completely useless for damping the various resonant frequencies in the box. Adding fibreglass in these enclosures disturbed the bass to some degree, but the midrange was so much cleaner that it was well worth the small sacrifice."
Why you guys keep going on about bizzare box interior shapes and then ignore that some materials exist that can really absorb sound better than other materials??
David S.
Volume filling a reflex box
"The above shows reflection, (red), and absorption (green) of 50mm polyester, approximately 25kg/m³. The peaks at 1 and 2kHz are due to standing waves in the test fixture. As can be seen the polyester fibre does not start to provide any really useful attenuation until around 1kHz, and then over the range we want we can expect no more than 10-15 dB with a typical 25mm covering at the standard density."
"Exactly as Robert describes here, one design in particular used an open cell foam to line the interior walls. Although the designer swears by it, the foam is completely useless for damping the various resonant frequencies in the box. Adding fibreglass in these enclosures disturbed the bass to some degree, but the midrange was so much cleaner that it was well worth the small sacrifice."
Why you guys keep going on about bizzare box interior shapes and then ignore that some materials exist that can really absorb sound better than other materials??
David S.
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