ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
This week's instalment is now online at
http://www.tonmeister.ca/wordpress/
Nothing there on how we make our loudspeakers. This one's about one of the things that I listen for when I'm working on them.
Cheers
-geoff
Thanks anyway - these are things that make you enjoy listening to music even more
Ha' en god weekend.
Millemissen
There is a tv - and there is a BV
Geoff Martin: This week's instalment is now online at http://www.tonmeister.ca/wordpress/ Nothing there on how we make our loudspeakers. This one's about one of the things that I listen for when I'm working on them. Cheers -geoff
Hi Geoff
I've been following your Blog with great interest and was delighted to see some internal pics of the Beolab 9s on article # 16 - gives me a good idea where the money goes.. AND makes me even more of a satisfied and very proud owner. I certainly appreciate reading about the sort of technology, R&D, and design aspects of what I own, as I do find that kind of knowledge very interesting and cements my appreciation of B&O as a brand that is at the cutting edge of speaker design.
Is it fair to summarise that with cabinet materials design, the main advantages of plastic would be that it can be made to be as acoustically 'inert' as MDF/plywood/veneered cabinets, but can be moulded into much better acoustic shapes (curves and cones) as regards edge diffraction and so on, plus being lighter, is going to represent better value to the end customer than a heavier MDF/plywood/veneered cabinet due significantly less shipping cost?
With respect to your latest article, my Lab 9's are placed a bit ad hoc, in that they are in front of my old Naim SBL speakers which I've yet to dispose of, and given a somewhat overcrowded room, whilst they're at 30 degrees and equidistant, I don't have them toed in on axis, but rather at just a slight angle.
So the placement is not ideal.... but...at the risk of boring you and the good people here, the following is a copy/paste of a comment I wrote on WHF in response to a query about Beolab 9's. The OP has consequently actually gone out and bought a pair of the Lab 9's and seems eminently pleased with them, not that I can claim, nor would wish to claim any influence in his decision.
"I had an experience last night actually, that prompted me to write and qualify some of my praise for the Lab 9's.
I play piano, trumpet and sing (all classically trained) and still perform occasionally, albeit only on an amateur level.
As such, and for me personally, authenticity to the original performance, is paramount in choosing kit - I'm of the school of thought that says a hiFi should be designed and engineered such as to give the 'closest approach to the original sound'
I went to hear a friend playing at a small jazz club - he's a brilliant pianist, and on a 9 foot concert Steinway, Acoustic Bass and Drums (all unamplified) the sound was stunning, as the room was a medium to largish rectangular room with good balance of acoustics, and they are all excellent players.
Coming home, I played back some jazz trio recordings I have of some of the jazz standards they played, and when one upped the volume to subjectively near the live performance levels that I'd heard, the sound from the Beolab 9's was exceptionally realistic indeed - to put it mildly!
It was all there;
Resolution - i.e. clarity, detail, and with it the most wonderfully natural tonal timbres - no shout, or bark, or honk, thinness or excessive hardness or brightness in the sound - just wonderfully authentic reproduction of the tonal timbre of live acoustic instruments.
Spatial perspectives - the acoustic lenses and the cone shaped cabinets can get right away from the large headphone presentation usually offered by rectangular/cuboid box loudspeakers, and gives a very convincing reproduction of the spatial perspectives as heard in real life only an hour or so before.
Transient Response - the subtlest nuance of musical dynamics, expression and contrast made for the same sort of spellbinding and involving listen that ones gets in live performance - there was no sense of compression, or sudden dynamic leaps from triple piano (ppp) to triple forte (fff) being compressed unnaturally, in any way. Rubato, synchopation and the most complex of interchanging rythms all clearly revealed as one hears in a live performance.
Dynamics: Most systems when you crank up the volume to near, or at live levels (a 9 foot Steinway grand is formidably loud in a medium sized room) simply compress the dynamics as they run out of either amplifer headroom, or loudspeaker driver limits, and the sound becomes congested and hardens, and the dynamics appear to be 'sat on'.
Not so with the Lab 9's - Whilst I don't feel they are quite as good in this regard as the Lab 5's (which are much more powerful again) nonetheless at neighbour annoying levels which subjectively approached the live sound, things held up without issue in any area that I could hear.
Simply put, this was the first time I've come home from a live performance, and put on a similar recording and not been disappointed at how far behind the live musical event most HiFi systems are - including systems that I've previously owned, and some very expensive systems I've heard in in-store demos.
For me, as a musician, the 'closest approach to the original sound' is always going to be the goal for me in a Hifi, music reproduction system, and apart from the Lab 5, the Lab 9's get me closer to that aim, than anything I've ever heard or owned in the many years of being involved in this hobby.
And as a musician, I cannot give them higher praise than that.
Simply superb.
Congratulations again on your choice, and I think you will have many countless hours of musical pleasure from your new system! "
I can't claim to have your ears Geoff as regards the precise spatial perspectives of instruments upon a stereo sound stage, however, I do feel that the Lab 9's and 5's really do deliver something significantly more realistic than 'conventional' loudspeakers (the big B&W 800 series comes to mind) when it comes to a presentation that is less 'large headphones' and more 'real life' as in a 'concert hall' balance of the sound.
I would assume a lot of this is down to the cabinet shape, and in particular the acoustic lenses and with it the balance of direct and reflected sound from room boundaries.
But yes, that's the first time I've come home from a live performance, popped on a similar recording on the HiFi, and not felt completely underwhelmed by the relative experience.
All I can say, is that I wish I'd discovered B&O aeons ago - I would've saved myself an awful lot of audiophool angst!
And lastly, would you prefer to discuss your blog articles here, or prefer that we comment directly?
I rather feel that there are quite a few 'ex' audiophools like me here, and a good chat/discussion about some of the topics you mention would be most interesting I feel.
What do you think about isolating drivers from cabinet wall vibration (B&W do this in their 800 series with a rubber encased gel substance, they call Isogel) as whilst it seems to make good audiphile sense, there may well be mitigations against it in the real, as against theoretical world.
I also note, that B&O don't provide spikes for the bottom of their speakers to mechanically 'couple' them to the floor - again another audiophile 'Bible' habit, and I'm sure B&O must have done some research and formed some conclusions as to not needing to do this.
Anyway, just some random thoughts...lol... I'm enjoying the blogs immensely and thanks again so much for your time and most interesting technical articles - always appreciated...
Kind regards
John...
I've been enjoying Geoff's blog, and Sean Olive's blog at Harman. Sean covers a lot about listening tests and how to run them, while Geoff focuses more on acoustics in general and B&Os approach in particular. I always enjoy reading about how B&O goes about things, since it's one of the few brands I have any interest in.
I believe plastic is easier to get an inert cabinet out of than MDF, if only because you can analyze the resonant patterns and devise a molded cabinet with built in strengthening ribs more easily than you can cut wood to brace cabinets. I have seen old Wharfdales that had double walls you filled with sand, those were pretty inert for the day. Sand, due to the individual particles rubbing against each other as the walls flex, provides ample damping due to friction between the particles. Weigh a frapping ton though. They were to be filled up by the user after delivery to the home naturally.
Years ago I had a paint designed for DIY'ers to help damp cabinet resonances. It was a kind of rubbery paint that stayed a bit soft, and it had a lot of sand in it. You painted several coats on the insides of the speaker walls and it was quite effective at improving cabinet resonances. Heavy stuff too.
Interesting to hear your experiences with the Lab 9s, when I finally got to sit and listen to them at a dealer in a decent room I was very impressed as well. Not quite the bass extension of the 5s but a very smooth and articulate speaker with great imaging and depth.
Jeff
I'm afraid I'm recovering from the BeoVirus.
Hi John
John: Is it fair to summarise that with cabinet materials design, the main advantages of plastic would be that it can be made to be as acoustically 'inert' as MDF/plywood/veneered cabinets, but can be moulded into much better acoustic shapes (curves and cones) as regards edge diffraction and so on, plus being lighter, is going to represent better value to the end customer than a heavier MDF/plywood/veneered cabinet due significantly less shipping cost?
In short: yes.
In long: Of course, you want a loudspeaker where the only thing moving is the driver. Vibrations in the cabinets are undesirable for lots of reasons (magnitude response, frequency-dependent directivity weirdness, and rub-and-buzz problem are the big three that immediately come to mind). So, the question becomes "how do you build a cabinet that doesn't vibrate (either in whole or in places) - and from what materials should it be made?" Lots of different materials can fulfil the purpose, but you want the one that does the job acoustically, is reliably repeatable on a production line, is relatively easy and cost-effective to manufacture, doesn't have health implications for the people doing the manufacture, doesn't require immense amounts of diesel fuel to transport around the planet, can handle the thermal implications, and so on and so on. The balancing act between these factors (as well as some more that I'm sure I'm forgetting...) will determine the best solution for a given product and a given manufacturer. It would be very hard to make a loudspeaker that looks like a BeoLab 3 out of MDF or plywood on a production line and stay within a tight tolerance window. On the other hand, it probably wouldn't make sense to build a rectangularly box-shaped loudspeaker out of aluminium or plastic.
John: With respect to your latest article, my Lab 9's are placed a bit ad hoc, in that they are in front of my old Naim SBL speakers which I've yet to dispose of, and given a somewhat overcrowded room, whilst they're at 30 degrees and equidistant, I don't have them toed in on axis, but rather at just a slight angle.
One thing to check in this specific case is whether your passive loudspeakers are singing along with the 9's. I've found in the listening room and at home, that if you have a passive loudspeaker in the room, not connected to an amplifier that's turned on, the woofers in particular (and the port/slave if they're there) will ring at their natural resonance. If you know where that resonance is, you might be able to hear it. Just play your 9's a little louder than normal and gently put a finger on the Naim's woofers to see if they're moving. If they are, you could try to put a small piece of wire across the terminals of the Naim's (i.e. connect + to - on the back of the speaker) to help keep it a little stiffer. The reason this works (if it does...) is that the electrical generator (of the coil moving in the magnetic field) works in opposition to the motor (of the current in the coil moving it in the magnetic field). In other words, the woofer's electrical output is always trying to push itself in the opposite direction to which its diaphragm is moving. Of course, it's better to just move them to a different room. :-)
John: And lastly, would you prefer to discuss your blog articles here, or prefer that we comment directly? I rather feel that there are quite a few 'ex' audiophools like me here, and a good chat/discussion about some of the topics you mention would be most interesting I feel.
I don't have a personal preference as to where the discussion takes place. Your place or mine - fine with me! :-)
John: What do you think about isolating drivers from cabinet wall vibration (B&W do this in their 800 series with a rubber encased gel substance, they call Isogel) as whilst it seems to make good audiphile sense, there may well be mitigations against it in the real, as against theoretical world.
The general concept is good - you don't want the cabinets to vibrate - and if they do, you don't want them to shake the diaphragm. In a best case, the basket of the driver is fixed on something that doesn't/can't move and there is no problem to fix. Of course, this is, in a real world, impossible - so isolation is one solution. An added benefit of some kind of gasket between the back of the driver basket and the loudspeaker cabinet is that you get an acoustical seal to prevent air leaks around the basket which can cause strange noises that sound like white noise modulated by the signal. However, you have to remember that, as soon as you put a screw through the isolating gasket, making a mechanical connection between the driver and the cabinet, any benefits of isolation from a vibration point of view are negated.
John: I also note, that B&O don't provide spikes for the bottom of their speakers to mechanically 'couple' them to the floor - again another audiophile 'Bible' habit, and I'm sure B&O must have done some research and formed some conclusions as to not needing to do this.
The floor, like a loudspeaker cabinet, shouldn't vibrate. If it does, it might be due to a mechanical coupling between the loudspeaker and the floor - however it might be due to an acoustical coupling (in other words, the loudspeaker moves the air which, in turn, moves the floor). You won't "cure" the acoustical coupling with spikes or rubber feet or anything else other than a structural change to the floor itself. That leaves us with mechanical coupling: if the cabinet of the loudspeaker vibrates and there is a physical connection between the loudspeaker cabinet and the floor, then the floor will vibrate. The question then is: how do you reduce the problem? One way is to ensure that the loudspeaker cabinet is not vibrating - at least at the points where its feet are mounted. Another way is to make the mechanical connection between the loudspeaker's feet and the floor as bad as possible at transferring the energy through to the floor. Whether you do that with a spike or a rubber foot or something else, depends on the floor, its surface, and the loudspeaker's vibration characteristics.
The important thing to always remember is that you can almost never point to one isolated thing in a complicated machine (like a loudspeaker) and say "THAT's the reason it sounds good (or bad)". I often hear/read things like "it sounds good because it has THAT DAC" or "THAT tweeter" or "a tweeter made out of THAT material" or "spikes for feet" or "rubber feet" or "interconnects made out of unobtanium" or whatever... It seems to be in our nature to want a simple solution to a complicated problem - and we like it more if we can put our finger on the simple solution (in other words, pointing to a spike is preferable to talking about a DSP algorithm, since you can't point to a DSP algorithm). Nobody says "A 1957 Ferrari 250 Testarossa is a great car because the spokes in the wheels were made out of steel." or "A Big Mac tastes good because of the type of sesame seeds on the bun." Yet we hear overwhelmingly encompassing claims about all kinds of excruciating minutiae when it comes to audio equipment. A complicated machine that works well is the result of a lot of solutions that work well together - it's a recipe full of ingredients. Change one ingredient, and you have to adjust the others as a result. And sometimes a solution that works well for one product isn't the best solution for another. And sometimes, it's just a matter of asking "what's the weakest link in the chain?" and fixing that one first.
Whew! Seems I'm long-winded today. Sorry...
Dom
2x BeoSystem 3, BeoSystem 5000, BeoSystem 6500, 2x BeoMaster 7000, 2 pair of BeoLab Penta mk2, AV 7000, Beolab 4000, BeoSound 4000, Playmaker, BeoLab 2500, S-45, S-45.2, RL-140, CX-50, C-75, 3x CX-100, 3x MCL2 link rooms, 3x Beolab 2000, M3, P2, Earset, A8 earphones, A3, 2x 4001 relay, H3, H3 ANC, H6, 2014 Audi S5 with B&O sound, and ambio
DMacri:Whew! Seems I'm long-winded today. Sorry... No need to apologize, we really appreciate your thoughtful responses. Keep 'em coming.
No need to apologize, we really appreciate your thoughtful responses. Keep 'em coming.
+ 1!
Geoff, no need to apologise - I love your clear, and yet technical chat, and am gladly putting much audiophile pseudo science/hype/myth behind me because of the likes of your clear, factual and erudite explanations.
Hugely appreciated - you are a huge asset to B&O, and if I may say so, to this forum and the B&O owners and friends who make up the membership here.
Many, many thanks!
Cheers..
John