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You're using $3 drivers and a mile of wiring for 24 of them and worrying about what??
Hello Zobsky,I thought my experience with the Visaton B200 might be useful to you.I have been using open baffle line source speakers in my music system for around four years and can verify that the performance from this type of speaker can be excellent. My earlier experiments were less than satisfactory due to the use of budget drive units (MCM aluminium cone units). However the design did show promise so I persevered. The MCMs had resonance problems in the lower treble area and a falling output above around 5 KHz so I was forced to use an additional tweeter array with a simple crossover. I also tried various damping methods on the MCM cones. Better but still not satisfactory. Budget drive unit, budget results.Last year I decided that I had to find a good full range drive unit so I could remove the crossover and consequently improve the phase response of the line. I had noticed that the Visaton B200 8” full range drive units were getting good comments on the forums so checked out their specs and concluded that, with frequency response correction, they should work well in my application. I ordered two for appraisal and fitted them to my test baffles. Initially they sounded loose and disjointed at the bass end and generally untidy at the top end. The mid band sounded promising so I let them run in for a while in the AV system which is used daily by the whole family. After a few days they began to improve and after a month of general improvements they settled into a nice balanced and very musical performance. The bass was a little lightweight but that is to be expected from one B200 drive unit per side on an OB. The top end rolls off above 15KHz and the response curve for the unit shows a 10 dB trough at around 12.5 KHz. This could have accounted for the initial untidy top end, but after burn in it sounds a lot smoother, so I suspect the curve was measured on a brand new drive unit without the benefit of burn in. One day I will persuade myself to part with the cash for a loudspeaker measurement system so I can verify what I am hearing.My local wood craftsman just happened to be the guy who manufactured Torlyte products for Russ Andrews here in England. So I got him to machine my line baffles for me. Boy was he accurate. Everything screwed together perfectly with no fettling. I wired the drive units in parallel with a symmetrical wire layout to ensure that the drive units receive identical drive signal. I don’t like the series/parallel approach because putting a reactive loudspeaker voice coil in series with another drive unit gives too much interaction and it wreaks the damping and control provided by the amplifier. Each line has eight B200 drive units so the resultant impedance is 0.75 ohms. I don’t need to tell you that most amplifiers would not like this so I designed a nice single ended, DC coupled, Class A mosfet current amplifier to do the business. The prototype is rated at 2.5 watts into 0.75 ohms, but that’s fine as the line has an efficiency of 105 dB for one watt at one metre (horn efficiency territory). The theoretical power handling for eight B200 drive units is 320 watts continuous, 560 watts peak although I suspect that this may have to be de-rated a little for open baffle use. Those with large rooms could achieve well over 120 dB per channel at the listening position. So a full concert orchestra can inhabit your home.How do these speakers sound? Firstly I should state that my requirement from my music system is that it should convince me that I have a live performance in front of me. I am a retired musician and have designed a number of acoustic instrument PA systems for touring folk musicians who wanted to be louder (to cover larger audiences) without any clue that amplification was being used. I have also attended a considerable number of classical performances (totally acoustic) over the years. I also like my rock music to rock. These loudspeakers go loud without stress and the dynamic range is awesome, although, as I like to listen to music at realistic levels, 2.5 watts can’t quite manage a full concert orchestra, in overdrive, in my listening room (the scope shows slight clipping on crescendos). So a bigger amplifier is my next addition (perhaps 10 watts of class A to keep up with the orchestra). The speakers are idling most of the time and the distortion is correspondingly very low (the cones are hardly moving). The drive units are highly responsive and present subtle detail beautifully (critical for the illusion of a live performance). The imaging is very stable at all dynamic levels, and musical events have a well-defined place on the stage. It is not possible to locate the position of the loudspeakers. Tempo and timbre are very good. This is partly due to the drive unit quality and partly due to lack of a crossover to mess up the relationship between the fundamental notes of the music and their harmonics (this coherence is much more important than achieving extended bandwidth). The bass reproduction is very natural (no cabinet resonances to muddle up the bass) with little room interaction (line sources are very good in this respect). Good program from all sources is very convincing and I’ve spent a lot time in front of these speakers without listener fatigue. The room positioning isn’t critical as long as you leave reasonable space behind the speaker (a metre is fine in my room). There is no critical hot seat. If you move to one side you just get a different perspective of the sound stage. This is very convenient for communal listening. Interestingly, I haven’t found an overwhelming urge to apply frequency response correction, although I do intend to investigate this, when time allows, to see if I can do it without destroying the musical coherence I have at present.Downsides? Nothing drastic. The bass is well presented and goes deep with decent weight (probably due to the line source directivity reinforcing the bass and balancing out baffle losses) but it isn’t as full at the bottom end as a sub woofer could achieve. The extreme top end could be a tad more extended but I am not going to sacrifice coherence for this, as what is presented is very natural. Airheads would probably feel the need to supertweet.I am impressed with the B200 drive units. They were designed for music not measurement. I can understand all the positive comment on the forums. A line source using these drive units won’t dump the performance on your lap but it will present a nice illusion of a realistic sound stage with live musicians on it. The line is also very good in AV systems, if fact quite scary with some programs (excellent dynamic range).RegardsPaul
Hello Zobsky,I thought my experience with the Visaton B200 might be useful to you...................RegardsPaul
AudiotoneHello TonyGood to see you again. I’ve just posted some power supply afterthoughts in your direction on the Atman thread.
audiotoneHave you tried the Jordan units in the winged baffle? The specs look very good. Efficiency is low at 88 dB, but 16 per side would give around 100 dB for 1 watt/1 metre. The FO Hz is pretty low but Qt at 0.4 would probably mean you would need bass correction to get enough low frequency weight.
Hi tony,I've just e-mailed the line source pic to you.It's sleep time now.RegardsPaul
Zobsky,Solder your wires onto the drivers before attaching them to the baffles. Also, it's a good time to treat the baskets too, since you'll never want to fool with them once you get them mounted, and cheapie baskets typically ring pretty well. Good work! All those driver cutouts is the only thing stopping me from experimenting more with OB arrays.Also, before you mount the drivers, you may want to consider adding a triangular strip of wood to the inside corners in back. That will enable a nice radius roundover on the front edges.Lastly, are the wings the same depth? The only time I tried same depth tapered wings I got quite a resonance, which the skillsaw cured in short order.
