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Hi All,I'm currently building a 300B SET amp and (nearly) full range speakers, to experience some of that SET - Fullrange magic I hear about. I want to be able to play complex, bass-heavy music without congestion, so my strategy is to use the 300B/fullrange system from 120hz or 180hz up, and relatively inexpensive (PartsExpress) dual powered subwoofers below that.
My understanding is that by relieving the fullrange speakers of base excursions, I will be able to play louder without congestion.
My bogie system is the S.E.X.y speaker on the Bottlehead site-- Fostex FE166E speakers in 1/4 cubic foot sealed boxes. As I understand it, the sealed boxes will create an acoustic 2nd order highpass filter with rolloff at around 120Hz, and prevent large drive excursions -- cleaning up the sound, and protecting the drivers.
This sounds great to me but, always having been a fan of planar speakers, I'm wondering if I can apply the same principle to open baffle mounted full ranges, and get a more airy, holographic sound?
I'm thinking a Fostex FE166E or FE167E in an approximately 3' open baffle (no WAF here) driven directly by my SET amp, with a 2nd order passive 120Hz or 180Hz passive highpass filter between the preamp and SET amp.
I invite all comments, concerns, suggestions, experiences on sealed versus open baffle in my situation, and whether to use the FE166E or FE167E in an open baffle with an SET amp with a low damping factor (output impedance).
Questions like--
Which speaker would provide better performance in this OB configuration?
What will the sonic tradeoffs be between OB and SB in this setup?
Will the OB with electronic 2nd order highpass be as uncongested and excursion limited (protected) as the sealed box with its mechanical/acoustic 2nd order highpass?
What have I overlooked?
I'm hoping that the OB configuration would let me get a more airy, electrostatic sound, yet the highpass filter will allow it to play loud and complex music without congestion. And that the large baffle will eliminate the need for a Baffle Step Correction filter ( BSC ).
Thoughts? :)
Follow Ups:
Hey Thanks Guys,I appreciate your ideas and encouragement. Now I'm debating between open baffle bass, or sealed box. thoughts?
I think I have a handle on passive line level crossover ( PLLXO ) design, but I haven't found a source for suitable inductors--does around 1H, low dc sound right? If you could suggest specific components and resellers, I'd be grateful.Thanks again,
George
If you're interested in OB sound you might as well give it a try. Definitely consider a highpass PLLXO arrangement to filter the bass from the FR cones. Off-the-shelf subs can work. OB bass (on same baffle) is better and more complex. You might try just one sub and see if you like the results -- get the second later if you do.If you appreciate the natural qualities of FR drivers, then an OB/sub combo can give you about the best you can get from dynamic drivers -- or at least you can do very well indeed for not much work or "design risk."
I have tried the fe167e w/ 300B & dual subs in the configuration you describe, it was good, but sub quality is a biggie. once you get above 80hz or so it better be good & fast subs or you will know what is going on with the subs & you shouldn't of course. I have went to open baffle. If you have the 167's just put'em in a 24 x 36 inch 3/4 MDF baffle, high pass the amp & use a pair of nice sealed subs, OR get a reputable bass driver for Open baffle bass augmentation, I use Vifa M26wr0908's on the same 24x 36 baffle mounted low & use BASH plates installed in small boxes I built. seemless integration is way easy. The sonics are WAY more natural, airy, & if you value imaging,, OB is crazy good at it. I run clean with no correction curcuits on B200's..with SET's -SEP's-PP amps & 300B in PPP , even 1/2 watt SET's . High pass on that amp should be very easy. I use plug in DIY high pass moduals I build, with Vitamin Q or whatever you like.You will be able to play clean at much higher valume. I listen to some seriouse hard music at times..& these simple OB's don't let me down..There are some Daytons that are very good for OB bass, I just can't remeber which ones they are..bbut there is lots of posted drivers that do it great.. Bass will be fast, tight,, & integrate easy. * likely not to have boom problems..run the plates of the amp outputs, this is the best I have found..any other way doesn't seem to keep up. I would try to drive your chosen driver clean.I actaually sometimes use a .22uf cap on some G2 ribbons, but not needed really.. I am getting 40.. also the B200 is something to consider.
Jandg,Very sound suggestions.
LA
Thanks JandG,Your experiences are interesting and informative.
Now for the followup questions. (grin) I'm fairly clueless about open baffle, so I hope you'll tolerate me.
Okay, now your bass solution sounds neat, but what about cancellation effects? Do you have any theoretical or measured info on how low your woofers go before they roll off? I'm certainly looking for full, natural bass.
Can you give me some sources for your DIY high-pass modules, and vitamin Q caps? What about your bass plate amps?
Again, forgive my cluelessness, but what are B200 s? (I plan to do some searching on B200 and Vifa M26wr0908 after I post this).
Thanks for the info and encouragement. I've always loved boxless sound--Dahlquist DQ-10 and Magnepans--so I'm excited about OB.
Best,
George
I don't have measurements to show how low the Vifa's are going, but I assure you they are doing 40hz fine. The Vifa's mentioned are discontinued & I am the only one I know of using them in OB, the have low Qts for OB, but for some reason they work very well. There are many drivers out there in production that are made for OB Bass augmentation or are a good match a proven in OB, look at the Decware forum, DIYaudio.com,Hawthorne audio has a excellent OB only forum.Huge thread called Dark Star,, google that,, it is huge. I would read all you can on the mentioned forums on open baffle, many people have headed that way , it will be easy to pick the bass augmentation driver.. alot of peoele use a Behringer DCX 2496 for active XO.. I am no fan of op-amps & such so I choose not to use them on the fullranger, direct to amp if possible for me..& sometimes a way out the xo , 1st order cap to a ribbon. The B200's can be purchased at E-Speakers.com. in Cal. $137.00 a pop I think. far superiour to the fe167e IMO.No whizzer, nice driver. As for refecttion, speaker placement is a biggie.. No hard & fast rules, most run them well into the room, I run mine 2foot from back wall. & just use material to cover the wall partially. most just treat the back of baffle with somekind of material..I can also calculate for you your PLLXO cut, just need to know your amp input impendence. or you can download the program @ TubeCAD.com just a couple rca's, very few parts & your cut, actually you can do it in your amp, but I like plug in's for now cuz I roll amps ALOT...I have tried lots & lots of alnico drivers in OB,, & these B200's are hard to beat.. Hemp Acoustics has some fullrange drivers coming out specifically for OB. Hawthorne Audio also has OB driver's & OB bass augmentation drivers.
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