Re: Will Greenies Kill Bass

by hughesths on Fri Apr 30, 2010 12:08 pm

Besides discussions, anyone here has experimented with your own system for any sound quality difference without and with air-con switched on during hifi listening sessions?
Please kindly share the sound quality differences of your findings if you have already tried, thanks.

by THT89 on Fri Apr 30, 2010 12:35 pm

mugenfoo wrote:Sound waves are mechanical in nature.
Light waves are electromagnetic in nature.

Nevermind la, you don't know what i mean..

hughesths, i have an uncle who told me that, his "er hu", made by some animal skin, actually gives different characteristic of sound in different season, summer vs winter. But, if within few degrees of changes in temperature, i'm not sure.. He told me that this is caused by the skin (like what harbeth tells about rubber cone), not by air flow, but i don't know how true is his conclusion. My 1 cent.

by mugenfoo on Fri Apr 30, 2010 2:15 pm

THT89 wrote:
mugenfoo wrote:Sound waves are mechanical in nature.
Light waves are electromagnetic in nature.

Nevermind la, you don't know what i mean..

Yeah, so mebbe someone else might .... so can answer your question better... Razz

by sflam on Fri Apr 30, 2010 2:26 pm

THT89 wrote: i have an uncle who told me that, his "er hu", made by some animal skin, actually gives different characteristic of sound in different season, summer vs winter. But, if within few degrees of changes in temperature, i'm not sure.. He told me that this is caused by the skin (like what harbeth tells about rubber cone), not by air flow, but i don't know how true is his conclusion.

musical instruments are different from hi-fi equipment. in fact they are the opposite of hi-fi in the sense that they need resonance to 'amplify' the sound. for e.g. the guitar, you strum the strings and the sound goes inside the chamber, and the wooden body resonates and the sound goes out of the hole to the listener.
a piano also has a sound board at the back to increase resonance.
the sound of musical instruments is affected by humidity and the amount of water content in the wooden parts. that is why people will also recommend having a heating rod inside a piano and it is left on 24/7. that is why musicians keep their expensive and sensitive instruments, especially those made of wood, in dehumidifiers. horns are not so susceptible to humidity.

in hi-fi, designers do everything they can to reduce or remove resonance completely because resonance can colour the sound.
that is why you have isolation platforms, dampening sheets, spikes, cones, constrained layer dampening, spring suspensions, etc.
speaker manufacturers use braces, composite materials, mass-loaded materials, etc to stop vibrations and resonance.

by THT89 on Fri Apr 30, 2010 6:34 pm

sflam wrote:
musical instruments are different from hi-fi equipment.

It's just to point out that the skin type of material can actually change the sound characteristic, and can be affected by temperature.

Anyway, oddly enough, (nothing related to the "er hu" ok?) Harbeth do believe speaker is like instruments, that resonant is meant to contribute to the speaker's sound signature. One of my friend told me before about this.. That's why usually Harbeth is not very heavy, and open frame ya?(nothing related to the "er hu" ok?). Other speaker designers usually do not have this kind of design philisophy.

mugenfoo wrote:Yeah, so mebbe someone else might .... so can answer your question better...

If you can't, no one else can

..

by mugenfoo on Sat May 01, 2010 12:44 am

sflam wrote:
in hi-fi, designers do everything they can to reduce or remove resonance completely because resonance can colour the sound.
that is why you have isolation platforms, dampening sheets, spikes, cones, constrained layer dampening, spring suspensions, etc.
speaker manufacturers use braces, composite materials, mass-loaded materials, etc to stop vibrations and resonance.

Not really. If u look at the design of the Magico speakers for example, there are 3 "tunable" knobs at the back of the speaker cabinet that alters the resonant characteristics of that massive metal internal brace-frame. (or at least what I've been told by the local seller), and hence altering the overall freq curve and most likely also alters the dispersion patterns of the loudspeaker system.

Sonus Faber are also built upon the design philosophy that cabinet resonances play a crucial role in the end product o the loudspeaker's sonic presentation. This includes the Guineari (never can spell this right) and its frontal grille strings and you'll appreciate that its not just all for looks.

Even a speaker cabinet's enclosure relies on the resonant inernal volume for the woofer to produce its sound. If you've listened to plain woofers (like in car stereos), the sound from the woofer itself without an enclosure sounds really crappy.

Infinite baffle cabinets (sealed enclosures) are resonant designed based on internal volumes and some other parameters.
Bass reflex cabinets, also utilise a "tuned" port which again is playing on the port's pipe resonances to give the bass extension.

Or consider the cabinet design of a typical Transmission line speaker (TDL comes to mind) . Its the resonant track of the baffled pathways what make it possible for such puny cabinets to produce really low bass extensions.

It's the careful art of controlling such resonances that permits loudspeakers to re-produce the lifelike sound.

by hughesths on Sat May 01, 2010 9:06 am

Another example of resonance concept designed speaker brand - Bosendorfer.

by sflam on Sun May 02, 2010 8:56 pm

in hi-fi, there r many ways to skin the cat.
some speaker designers do all they can to deaden vibrations and resonances.
some know that zero vibration and resonance is probably an impossibility and try to use vibrations and resonances to their benefit by making them add to the sound beneficially.

mugenfoo wrote:

Even a speaker cabinet's enclosure relies on the resonant inernal volume for the woofer to produce its sound. If you've listened to plain woofers (like in car stereos), the sound from the woofer itself without an enclosure sounds really crappy.

Infinite baffle cabinets (sealed enclosures) are resonant designed based on internal volumes and some other parameters.

the sound from the woofer itself without an enclosure sounds really crappy simply because the back waves generated by the rear of the cone interacts out of phase with the front waves generated by the front of the cone.
that is why there is this design concept called infinite baffle i.e. a baffle so large that the longest sound waves from the rear of the cone cannot interact with the front waves.
since it is impossible to have an infinite baffle, designers came up with the sealed box solution to trap the back waves in a box to prevent them from messing up the front waves.
to say that "a speaker cabinet's enclosure relies on the resonant inernal volume for the woofer to produce its sound" is inaccurate.
also, sealed enclosures are not resonant designs.
in fact to reduce "box talk" i.e. the walls of the box vibrating and resonating and creating their own sound, designers dampen them with bitumen sheets, etc, or use mass-loaded materials. some use low-mass materials like aluminium.
and to reduce standing waves inside the box which can add colorations to the sound via the cone, designers stuff the box with wadding and foam to make the internal volume of air less 'noisy'.

Bass reflex cabinets, also utilise a "tuned" port which again is playing on the port's pipe resonances to give the bass extension.

yup, this is correct.

Or consider the cabinet design of a typical Transmission line speaker (TDL comes to mind) . Its the resonant track of the baffled pathways what make it possible for such puny cabinets to produce really low bass extensions.

i don't think it's the "resonant track of the baffled pathways" that allow puny speakers to produce low bass. in a transmission line speaker, the designers stuff the 'tube' with wadding of different types and densities to absorb the high and mid frequencies so that only the bass frequencies escape from the openings in phase with the sound from the bass driver. i am now using the pmc ob1i speakers and that's what the manual says.

hughesths wrote:Another example of resonance concept designed speaker brand - Bosendorfer.

i hv never heard bosendorfer speakers before but i went to its website. they r using techniques used for making musical instruments to make loudspeakers such as using sound boards to amplify and colour the sound with resonances. they must be the only speaker company in the world using this technique. it shld be interesting to find out how the speakers sound like...

the majority of speaker makers do all they can to deaden vibrations and resonances. famous ways of doing so include wharfedale using two boxes in one with the space inbetween filled with sand; B&W's Matrix system of internal braces; and Wilson Watt's high-density composite 'X' and 'M' materials for the box and baffle. Wilson Watt also uses lead blocks to dampen vibrations.

by mugenfoo on Sun May 02, 2010 9:23 pm

sflam wrote:in hi-fi, there r many ways to skin the cat.
some speaker designers do all they can to deaden vibrations and resonances.
some know that zero vibration and resonance is probably an impossibility and try to use vibrations and resonances to their benefit by making them add to the sound beneficially.

mugenfoo wrote:

Even a speaker cabinet's enclosure relies on the resonant inernal volume for the woofer to produce its sound. If you've listened to plain woofers (like in car stereos), the sound from the woofer itself without an enclosure sounds really crappy.

Infinite baffle cabinets (sealed enclosures) are resonant designed based on internal volumes and some other parameters.

the sound from the woofer itself without an enclosure sounds really crappy simply because the back waves generated by the rear of the cone interacts out of phase with the front waves generated by the front of the cone.
that is why there is this design concept called infinite baffle i.e. a baffle so large that the longest sound waves from the rear of the cone cannot interact with the front waves.
since it is impossible to have an infinite baffle, designers came up with the sealed box solution to trap the back waves in a box to prevent them from messing up the front waves.
to say that "a speaker cabinet's enclosure relies on the resonant inernal volume for the woofer to produce its sound" is inaccurate.
also, sealed enclosures are not resonant designs.
in fact to reduce "box talk" i.e. the walls of the box vibrating and resonating and creating their own sound, designers dampen them with bitumen sheets, etc, or use mass-loaded materials. some use low-mass materials like aluminium.
and to reduce standing waves inside the box which can add colorations to the sound via the cone, designers stuff the box with wadding and foam to make the internal volume of air less 'noisy'.

Bass reflex cabinets, also utilise a "tuned" port which again is playing on the port's pipe resonances to give the bass extension.

yup, this is correct.

Or consider the cabinet design of a typical Transmission line speaker (TDL comes to mind) . Its the resonant track of the baffled pathways what make it possible for such puny cabinets to produce really low bass extensions.

i don't think it's the "resonant track of the baffled pathways" that allow puny speakers to produce low bass. in a transmission line speaker, the designers stuff the 'tube' with wadding of different types and densities to absorb the high and mid frequencies so that only the bass frequencies escape from the openings in phase with the sound from the bass driver. i am now using the pmc ob1i speakers and that's what the manual says.

hughesths wrote:Another example of resonance concept designed speaker brand - Bosendorfer.

i hv never heard bosendorfer speakers before but i went to its website. they r using techniques used for making musical instruments to make loudspeakers such as using sound boards to amplify and colour the sound with resonances. they must be the only speaker company in the world using this technique. it shld be interesting to find out how the speakers sound like...

the majority of speaker makers do all they can to deaden vibrations and resonances. famous ways of doing so include wharfedale using two boxes in one with the space inbetween filled with sand; B&W's Matrix system of internal braces; and Wilson Watt's high-density composite 'X' and 'M' materials for the box and baffle. Wilson Watt also uses lead blocks to dampen vibrations.

OK, agreed & correction: Its not the internal volume of the speaker enclosure that gives rise to the resonance of the volume. Resonant is not the right word here. But there is a formula that for a given woofer cone surface, the internal space needs to be of certain volume to get a certain particular freq. response .... maybe someone who has a loudspeaker cookbook can shed more light into this.

For the Transmission line speaker, its not just a matter of letting out the bass via the long tracts, but more like using the tracts as a wave-guide pathway to enhance bass response. Perhaps an analogy would be the transmission path is actually a long folded bass-reflex port... Resonant designs definitely come into play here. (anyone with reference to a speaker design cookbook can verify or dis-spell this would be most appreciated).

As for ABC materials used for dampening, yes, the structure of the cabinet designs themselves should not vibrate or resonate to any freqs, hence all the deadening and exotic materials, and clever construction techniques used.

But fact of the matter is, loudspeakers, just like any sound producing (and re-producing) product, still need to utilise resonances , but of course in a controlled and intended fashion. Now back to those three knobs behind that Magico V2 speaker...

by sflam on Sun May 02, 2010 10:12 pm

just remembered that jvc makes speakers with cones made of specially treated wood (sake is used to soften the wood) so that the music will sound harmonically rich like the instruments used by musicians
chk this link http://www.jvc.eu/woodcone/index.html

will these speakers be affected by heat, humidity or the air-con? i don't know.

by cmboy on Sun May 02, 2010 10:40 pm

sflam wrote:
will these speakers be affected by heat, humidity or the air-con? i don't know.

I popped a similar question to the Dynaudio head honcho (when he was here) about cone deformation, and he did answer that if that happened it was certainly a defect in the cone material and shouldn't happen as they manufacture car speakers and they're subjected to all sorts of weather wherever they export to.

by mugenfoo on Sun May 02, 2010 10:44 pm

sflam wrote:
the sound from the woofer itself without an enclosure
sounds really crappy simply because the back waves generated by the rear
of the cone interacts out of phase with the front waves generated by
the front of the cone.

Actually after pondering on this point further, then how would one explain dipoles such as Electrostatics and Ribbon or similar Planar speakers ? Won't the rear portion also then "interfere" with the front portion and screw up the sound ? Same goes for sealed-enclosure arrangement woofers with a push-pull arrangement and some calculated internal volume of air in between.

But far from it, some people would swear on the uncanny realism,clarity and surreal life-likeness of planar speakers...

by mugenfoo on Sun May 02, 2010 10:47 pm

sflam wrote:just remembered that jvc makes speakers with cones made of specially treated wood (sake is used to soften the wood) so that the music will sound harmonically rich like the instruments used by musicians
chk this link http://www.jvc.eu/woodcone/index.html

will these speakers be affected by heat, humidity or the air-con? i don't know.

well, if the cones are hygroscopic in nature, then yeah, sure would eventually deform/decay in our climate.

Same goes for the electrostatic panels as well and the older Martin Logans were notorious for failing in tropical climates. Last i heard, they've improved their charge panels to be more humidity tolerant, but on the ML website, they still recommend an air-conditioned room at all times for their speakers. (remember seeing it there , sometime ago...)

by THT89 on Mon May 03, 2010 9:56 am

So in a tropical country, usually how long will a speaker survive? Anyone has any number to tell? Any experience?

by mugenfoo on Mon May 03, 2010 10:11 am

THT89 wrote:So in a tropical country, usually how long will a speaker survive? Anyone has any number to tell? Any experience?

friend, this question is so open-ended and too many other factors to consider.....
doubt if anyone can give u an intelligent answer on this one.

by sflam on Mon May 03, 2010 1:41 pm

THT89 wrote:
So in a tropical country, usually how long will a speaker survive? Anyone has any number to tell? Any experience?

i can only give u an answer based on my experience. i used to own a pair of jpw speakers and the woofers had foam surrounds. these disintegrated after 6-7 years. Replaced the foam surrounds and sold them and bought mission 782s which had rubber surrounds.

rubber surrounds last longer since most, if not all, speaker manufacturers use artificial rubber instead of natural rubber.

by sflam on Mon May 03, 2010 6:50 pm

by mugenfoo Yesterday at 10:44 pm

sflam wrote:
the sound from the woofer itself without an enclosure
sounds really crappy simply because the back waves generated by the rear
of the cone interacts out of phase with the front waves generated by
the front of the cone.

Actually after pondering on this point further, then how would one explain dipoles such as Electrostatics and Ribbon or similar Planar speakers ? Won't the rear portion also then "interfere" with the front portion and screw up the sound ? Same goes for sealed-enclosure arrangement woofers with a push-pull arrangement and some calculated internal volume of air in between.

But far from it, some people would swear on the uncanny realism,clarity and surreal life-likeness of planar

chk this link. explains everything with great graphics.

http://forum.blu-ray.com/speakers/66471-guide-bipolar-dipolar-direct-radiating-surround-speakers.html

by mugenfoo on Mon May 03, 2010 7:21 pm

Great graphics it is !

by THT89 on Tue May 04, 2010 9:46 am

sflam wrote:
i can only give u an answer based on my experience. i used to own a pair of jpw speakers and the woofers had foam surrounds. these disintegrated after 6-7 years. Replaced the foam surrounds and sold them and bought mission 782s which had rubber surrounds.

rubber surrounds last longer since most, if not all, speaker manufacturers use artificial rubber instead of natural rubber.

6 to 7 years is too fast isn't it?! I'd been offered before a pair of old mission (don't know how old it is), had its initial transparent woofers turned a little bit white in colour. So, i'm not sure whether those are the sign of dis-integration. When i audit (don't know whether it's my psychological effect), it sounded muddy, only if my ear is parallel to the tweeter, which is located in between of the top and below woofers. End up not buying..

mugenfoo wrote:
friend, this question is so open-ended and too many other factors to consider.....
doubt if anyone can give u an intelligent answer on this one.

Nevermind la, just to gain some knowledge on people's experience, i got none, don't have to be intelligent

Or amybe i souldn't ask too much b

..

But i think in the end, if that particular foam made speaker sounds good, although it may wear out and need a lot of maintainance.. Better not consider also?

by zul on Wed May 05, 2010 1:51 pm

Hi guys,
Have a read on S. F. Lam's Hi-Fi Avenue with Alan Shaw today....that's what Bite's starting thread all about. Interesting though.! That's why Sam named his shop as Tro***al Audio