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Loudspeaker Technology & Innovation
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proffski
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PostPosted: Fri Mar 02, 2012 8:39 am    Post subject: Loudspeaker Technology & Innovation Reply with quote

Same principle as that used by KEF with the activated carbon granules.
I have always wondered about the active longevity of the carbon as it gradually absorbs other contaminants in the air.
Same with this new product... any chemists out there? Wink

http://www.elektor.com/news/miracle-material-doubles-speaker-volume-for.2091163.lynkx?utm_source=UK&utm_medium=email&utm_campaign=news&cat=audio/video/foto
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audiolabtower
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PostPosted: Fri Mar 02, 2012 11:46 am    Post subject: Reply with quote

It must wear out? same as cooker hoods without venting, the carbon foam becomes less useful with age? Maybe with less contamination inside a cab it works for the lifetime of the speaker?... but surely not for some of our classics, 30 years old and still going strong...?
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ColinR
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PostPosted: Fri Mar 02, 2012 12:39 pm    Post subject: Reply with quote

Quote:
It must wear out
&
Quote:
inside a cab it works for the lifetime of the speaker



A "sealed" box loudspeaker is essentially a pseudo adiabatic system to avoid barometric effects where external pollutants such as cigarette smoke, burnt food, aerosol sprays, perfume, nearby roads, dodgy central heating, etc., will shorten the lifespan of any activated carbon product.

I suspect it’s engineered to last the expected product lifespan; about 6 years not 30+.
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proffski
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PostPosted: Fri Mar 02, 2012 6:25 pm    Post subject: Reply with quote

Sadly that is the sort of answer I was expecting but hoping not to get Colin.

This could be an interesting long term study for somebody, measuiring the performance of a bass driver in an enclousre over eight years in an "average" domestic environment.
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Thierry
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PostPosted: Wed Mar 14, 2012 10:58 am    Post subject: Reply with quote

Product seems to be oriented to cellular phones rather than relatively large bass cabinets used in home loudspeakers : http://www.knowles.com/search/nbass/h_nbass.jsp
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proffski
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PostPosted: Wed Mar 14, 2012 1:15 pm    Post subject: Reply with quote

I remember the 1st Philips MF loudspeakers from the early 1970s?
The models I listened to were smaller and the tweeter was mounted in the classic position. I heard another pair much later in Delmenhorst, Germany when visiting friends. May have been RH 544s???

Some nice pictures thank you, fascinating!
https://plus.google.com/photos/109296933751482509949/albums/5728370414172947121?banner=pwa&gpsrc=pwrd1
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Thierry
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PostPosted: Thu Sep 27, 2012 6:09 am    Post subject: Reply with quote

The model you listened to was probably the RH532, a 2 ways small box. First issue had a foam surround woofer. Few years later (1975 ?) it was replaced with model RH541, rubber surround woofer and black plastic cabinet. I have this model along with the bigger (3 ways) RH544.
Actually I have picked up some of them for experiments on possible electronics improvements and testing better modern HF drivers than the original one, allowing a lower crossover frequency.

Of course the smaller 541 sounds different from the 544, it has less power in the low frequencies and the 3 ways speaker is able to play much louder as it has 2 amplifiers built in : a 40W amp for the woofer and a 20W for the mid and HF drivers, whereas the 541 has a 20W amp powering the two drivers. But the 2 ways 541 has more consistency in the midrange and better imaging than the 3 ways RH544.
Both models are very, very good sounding speakers in quite small enclosures. Bass is powerful, very tight and controlled. Many people will find them ugly - indeed they look strange - but to me they are wolves in sheep clothing.

link towards pictures showing the innards of the smaller model : https://picasaweb.google.com/109296933751482509949/PhilipsRH541#

Here's my small stack of 2 ways RH541s




The two Philips MF speakers standing beside my beloved 105/2s.


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proffski
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PostPosted: Thu Sep 27, 2012 5:19 pm    Post subject: Reply with quote

Blimey, you maske my mink Hi-Fi museum look empty and sad.
I had no choice but to sell previous loudspeakers or lend permanently to family due to space restrictions.

I got a nice warm glow from your pictures, thank you! Smile
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Thierry
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PostPosted: Thu Sep 27, 2012 5:35 pm    Post subject: Reply with quote

proffski wrote:
Blimey, you maske my mink Hi-Fi museum look empty and sad.
I had no choice but to sell previous loudspeakers or lend permanently to family due to space restrictions.

I got a nice warm glow from your pictures, thank you! Smile


Glad you enjoy it Wink
Yes I feel lucky.
This is only part of my speakers museum, the rest is here : http://dcx2496.fr/vintage_2.php

Note the very scarce Korn & Macway system, another FB system based on cone speed control (called Voigt Bridge).
Strange design but an awful lot of bass again, given the size of the boxes. Didn't find much documentation about these.

More pics when clicking photo on the above linked page.


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proffski
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PostPosted: Thu Sep 27, 2012 5:45 pm    Post subject: Reply with quote

I've had some adventures with the IMF Super Compacts, never been a fan of Bose though... Cool

I recognise some others but a few strangers amongst the collection.
Have you ever heard a loudspeaker with MF working when it goes wrong?
Not for very long...
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Thierry
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PostPosted: Thu Sep 27, 2012 7:42 pm    Post subject: Reply with quote

proffski wrote:
I've had some adventures with the IMF Super Compacts, never been a fan of Bose though... Cool

I recognise some others but a few strangers amongst the collection.
Have you ever heard a loudspeaker with MF working when it goes wrong?
Not for very long...


I have experienced this situation : amongst the Philips RH541 lot I bought there was one example with a strangely pointing out woofer. It was dead stuck in the maximum excursion position. As I had nothing to loose and enough speakers I dimanstled it and performed some surgery that resulted in an unexpected reanimation : https://picasaweb.google.com/109296933751482509949/WooferPhilipsRH541MFB#slideshow/5743799625598029218
Since that surgery it works like a wonder. During experimentations I also blew an woofer amp. The driver produced a funny wheezing sound before the output transistors released the magic smoke that had been kept inside them for so many years of trouble free operation Smile

I own the Bose 901 MkII not for sound quality but just because (in my modest opinion) they are a milestone in consumers loudspeakers history.
Truth is also that theses speakers handle an awful amount of electric power and are able to deliver unbelievable distorsion-free sound pressure, enough to make your ears bleed before they show the slightest audible stress - as far as you drive them with a decent amplifier, i.e. the Bose 1801. A system meant for BIG SOUND lovers. Only the KEF KM1 was able to deliver such distorsion free pressure (with much better sound quality of course).
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proffski
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PostPosted: Thu Sep 27, 2012 9:45 pm    Post subject: Reply with quote

Hmm, the Bose might have gone loud, but not as an average domestic consumer product. All those small units and all that equalisation, not too elegant.
I would vote the AR LST as just ‘one’ of the milestones in the history of acoustic transducers worthy of a mention amongst many others.

Going back to MF, there was a magazine which featured a DIY project, I cannot remember which sadly. For subwoofers as with Velodyne the concept is indeed rather appealing!
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clubsport911
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PostPosted: Fri Sep 28, 2012 3:12 am    Post subject: Reply with quote

I love that collection ! If ever you needed proof that there is diversity in design, this was it. I always think it incredible that the laws of physics apply to all designers, they (mostly) All have the objective of making excellent sounding transducers, but the outcome....is so varied

Of all your collection, it's the Phillips MFB's that I'd like to hear the most !

Good work
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Thierry
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PostPosted: Fri Sep 28, 2012 3:52 am    Post subject: Reply with quote

proffski wrote:
...
I would vote the AR LST as just ‘one’ of the milestones in the history of acoustic transducers worthy of a mention amongst many others.

Going back to MF, there was a magazine which featured a DIY project, I cannot remember which sadly. For subwoofers as with Velodyne the concept is indeed rather appealing!


Ah yes the AR LST ! I am after a pair of these since many years but they are a rare find. I have a pair of AR4 xa which are really nice little speakers. The principle of acoustic suspension was definitely a major step in enclosure design and box size reduction, thanks to Edgar Villchur, founder of AR. Sadly he passed away last year and I haven't seen many tributes to his inventions, although many of them changed things for ever in audio.

clubsport911 wrote:
...
Of all your collection, it's the Phillips MFB's that I'd like to hear the most !

These are a relatively easy find, at least on the continent. They were such a success 30 years ago and so well built that many examples survived and they pop out from time to time on well known auction websites.
Problem is to avoid paying the silly price that sellers are usually asking for (like anything rare enough associated to the word "audiophile" ). I paid €80 for the big RH544 pair and €50 for the smaller RH541. These are fair prices in my opinion. I have seen some examples going for 5 times this Rolling Eyes
If you can source a pair, go for it, you'll never regret your purchase, both models are true jaw-droppers.
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clubsport911
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PostPosted: Fri Sep 28, 2012 4:18 am    Post subject: Reply with quote

My memory on the MFB's is fading somewhat, and if I recall, I first heard them in the early 80's. Am I correct ? They take me to a time when "revolutionary" speakers like the Wharfedale E70 were released (whatever happened to them ) and I felt that there was certainly more experimentation going on.

Cheers
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