speakers immune from room effects. can this even be possible?
some time ago I discovered one great (IMO) speaker invention in the form of a CBT36 speaker. I didn't turn your attention to this speaker because I knew few people here dig deep enough into technicalities behind hi-fi design to even start a thread. but today I discovered some flicks at youtube that might prove very useful in showing the advantages of the technology better than any graph could do. but first some foreword.
why CBT? it stands for Constant Beamwidth Transducer. as the name suggest the speaker should produce a stable wave launch regardless of the surroundings it's placed in. or in other words it should not matter if the speaker is playing in anechoic or echoic conditions because its performance will be unaltered. why 36? the speaker is slightly bent, it's like a fraction of a circle. and the bend arc is 36 degrees. the speaker was invented by speaker design veteran Don Keele.
and now the flicks I was mentioning above:
- the speaker itself in action (please read the introduction in the movie): http://www.youtube.com/watch?v=McbuV1jSOs8
- some theory behind the design by Don Keele himself and more action: http://www.youtube.com/watch?v=ImSOzhI5JJA
just for comparison's sake I link to some other flicks:
- a very hi-fi system, video courtesy of a forum member: http://www.youtube.com/watch?v=Lcs_emvt9gA (regards Iceman )
- and "the second best speakers money can buy" as some want us to believe, just to show you it's not a problem of passive speakers, or active, but all quasi point source speakers placed in an untreated room suffer similar problem: http://www.youtube.com/watch?v=slcpDA7adhw
note excessive echo camera mic picks up in both cases, and also you can hear considerable deviations from flattish frequency response at some points in frequency response spectrum. of course if you were in that room and heard the speakers for yourself they wouldn't sound half as bad due to our brain doing a lot of filtering out of unnecessary sounds and flattening some freq deviations to make sounds sound as the brain remembers them they should sound (if you don't believe in what I just said make a simple experiment - record your hi-fi playing through a mic (with no echo cancellation), like on a photo camera and then listen to the recording. I'm sure the revelation will be totally different to what you're accustomed to).
if, however, someone is interested in how the technology works I recommend checking out those pdfs:
- CBT36 vs. B&W 801 Matrix - comparison of in-room measured performance. the significance of this exercise is that it shows how your average quasi point source speakers interact with a room (you could replace B&W speakers with any other similar design and the results won't vary much) and how CBT36 seems to be immune to effects of early reflections (freq response deviations) and how they manage to maintain virtually unaltered character regardless of the listening distance from the speaker or the listening height: http://www.audioartistry.com/brochures/B&W%20801%20vs.%20CBT36%20Ground-...
- this pdf here shows graphic representation of how different speaker designs behave in "free air" a.k.a. anechoic conditions (highly unlikely to ever occur in practice to most) and on ground plane (most common situation). those graphs should give you some food for thought, I hope:
- similar to the one above but much more in depth; comparison of performance of different line-array speaker systems: http://www.audioartistry.com/Papers/CBT%20Paper6%20PerformanceRankingof%...
maybe some pros and cons for the ending:
- as already mentioned - immune from room effects, uniform soundfield over a wide array of listening distances and heights.
- nearly purely resistive 4 Ohms impedance curve with little electrical phase shift - meaning very easy load on the associated amps, but need to be rated into 4 Ohms load. as a side word; this feature came to me as a big surprise because the speakers use conventional (albeit custom made) voice coil drivers. since there is a voice coil in the signal path there has to show up inductive load on impedance curve at some stage. but the speakers are designed in such a way that there are resistors in series with the drivers. nothing to do with impedance linearisation, it's simply like some of the driver banks need to be attenuated somewhat with relation to the others and flat impedance curve comes as a bonus. OK, some may argue that because of this any potentially beneficial effect of amps damping factor onto drivers' movement control is wasted (the driver will "see" impedance from the resistor and not the amp), but since there are so many drivers working in tandem none of them has to work too hard on its own. excursion will always be minimal, even at high volume levels, hence the effect of amp's DF shouldn't be crucial here IMO.
- as they say: de gustibus non est disputandum, but IMO the speakers look just stunning! very interesting looking design. and this is for a speaker where form follows function.
- IMO rather affordable price of $2000 per pair...
- ... but the speakers so far are only available in the DIY version, AFAIK. which means you get all the necessary parts, including drivers and cabinetry, but you have to do the whole assembly and finishing yourself, or let somebody knowing do it for you. AFAIK the speakers will also be offered in fully assembled version but at much higher price.
- not just plug-and-play. what I mean by that is in order to get the speakers up-and-running you'll also need an active crossover and 4 channels of amplification (like 2 stereo amps or 4 monos). the speakers are meant to be working in active principle, there's no option of a passive version. because of the associated equipment requirement definitely not an option for minimalists.
- the speakers are spec'ed to reach down to 45Hz (despite small woofers used). that should be low enough for most but if you're one of the nether region lovers you'll need augmentation from subwoofers (and a 3-way active xover if you're a perfectionist ).
I'm hoping all that English would come useful to someone. please input below your thoughts on the whole idea, if you have any.
P.S. I'm thinking I'd like to see an integrated 4-channel amp with built in 3-way active xover on the market soon. That would solve the multi-box requirement to drive the speakers for me...