[JeffB]

I only have room for a baffle of about 12".
I could add wings, but they would need to go straight back.
Basically a box with no back.
I fear such an open back box would lose many of the benefits of going open baffle.
Any thoughts on this?

[nodiak]

Hi Jeff,
You are talking about uboxes.
Here's a link to some work JohninCR has done with them.

http://www.hawthorneaudio.com/forum/viewtopic.php?t=20

He also has done a smaller ubox using B200's. I couldn't find the photos right now. You should ask him about it, he'd be into that. Might fit in your space.

[JLM]

JGP,

You query includes an often overlooked aspect, that the F200A is a true full range driver.  I'm not aware of any other "reasonably" priced driver that has the stated 30 - 20,000 Hz range of the F200A.  Like most drivers that are touted as "full range", the B200 is essentially a midrange/tweeter.   Box designs, like the Omega, can help these extended range drivers reach upper bass frequencies (close to 50 Hz).  Note that the large majority of the single driver crowd have learned to ignore the bottom octave, which also explains why they are satisfied with open baffle designs (which are also bass limited).  It's always been curious to me that any music lover or audiophile would want to live without the bottom octave of the piano (32-64 Hz).

I've owned the Bob Brines FTA-2000 floorstanding mass loaded transmission line speakers that use the F200A for nearly two years now and am very pleased with them.  I'm a big MLTL fan, check out Bob website and t-linespeakers.org for lots of information.  Like any whizzerless 8 inch extended/full range driver they the high frequencies beam, but that can be turned into an advantage.  They can go flat in room below 30 Hz.  The term "in room" are fighting words to many, but that's where we listen.  It's not scientific, but is practical.  Like many extended range drivers the F200A has a fairly limited spl output, but in all but the largest rooms and most demanding listeners does reach more than adequate levels.  

And I'm not sure where a comment like "midrange is totally missing" (from the F200A) comes from, because to my ears, by my crude measurements, and the manufacturer's response curves they don't show anything like that.  Perhaps it's because the F200A lacks the shouty midrange that several popular extended range drivers have and more than a few listeners have acclimated to.

BTW, some do use and prefer the F200A in open baffles.  Open baffles tend to reduce resolution (probably due to the uncontrolled mixing of front and rear sound waves) while a few have commented that the B200 is too detailed, so the combination may compensate well for each other.  Because of their dipole wave dispersion characteristics open baffles need more space behind and in front for the soundstage to "gel".  

As defined by the graph on the single driver website simple open baffles have limited bass frequency range, which works well with typical mid/treble extended range drivers.  The graph indicates rather large baffles are needed just to reach mid/bass frequencies.  Note that drivers with higher Qts values (0.5 and above) like the B200 work best in open or infinite baffles.

If I hadn't found the F200A/Bob Brines combination, I would have given up on the single driver ideal and gone with powered subs and crossed over around 80 Hz to mid/treble drivers in open baffles.  I've heard a few open baffle examples, but not the B200.  I have no axe to grind regarding either, just trying to share what I know of them compared to the F200A.

[nodiak]

My favorite speaker systems were TL's. In '87-88 I was helped to make MTM's using 7" and 8" Focal drivers. For budget diy they blew me away. I just loved the smooth bass, tone and openness of those tl's. Especially with the 8" mtm tl's under 30hz was no problem.
I'm finding working with OB's that again I can get totally pleasing smoothness, tone and openness. With a high qts. bass driver sub 30hz and up is no problem. (If I owned my own home I would definitely go with Cult of Infinitely Baffled ideas tho.)
OB's require adjusting to the room, they are diy in that respect and come with no owners manual. I'm guessing the necessity to make their output blend with in room response is a big reason there aren't many commercial units (but they're coming, like the Jamo). Along with size, shape, and general differentness.
There are ways to suppress some of the backwave if needed, as well as contain near wall reflections to a degree. Example: a ubox with material draped over the back (something of an aperiodic?).
There is tons and tons of experience and info on the net about their use. But it is definite that you have to be willing to work with the room to get the best from them.
I look at it as a continuum from TL's (of which there are many variations too) to uboxes (variations....) to flat baffles.
A transitional system I'm making for sale locally will use small Fostex in small OB on top of 8" bass in TL or vented. Crossed @300hz. Looks like conventional medium size floor stander (~ 12" x 10" x 38"), with more open sound than usual. Woofer in it's own 40 liter chamber, Fostex in usual tweeter spot but no back to this top section of box. Needs 3' to wall, maybe 2' in a pinch. It's an evolutionary step from some 3-way systems I learned to make in the late 80's, then using short TL's for the midwoofers, tweeter on top. To deal with rear reflections draping material across the back of OB is helpful. I would think this starts edging into aperiodic or tl definitions at some point.You might want to try something similar. Biamping with electronic xo would be sweet.
Also I think some minds get stuck on definitions or like to pick sides, does it really matter if your system is part OB/Aperiodic/TL if that gets the sound you want?  
For the discussion my main point is you can get a widerange of "sound" and room adapting from ob's, but you have to work on it. Some of us like this work and consider it play.
Don

[Dmason]

Don,

Sounds like a good plan. Transmission Lines blend nicely with OB sonics. I have used dual TL bass machines calc'd by Greg Monfort a few years ago with the DarkStars, using HiVi M8N, (an outstanding, obscure driver,) and they mesh nicely; you seem to be on to something. Nothing from a box can match TL bass for smooth.

[GHM]

The TL bass is something I've found I can't go without.  As posted previously, there will always be a compromise some where. I'll compromise a smaller sweet spot, efficiency and a little top end for well integrated bass and a midrange free of shout. Something many box speakers have a hard time doing. Especially module type speakers. I had a pair of multi ways that even had a shout that would tear your ears off on certain recordings. I hope the midrange isn't too bad on the F200As .

 I've owned a couple of planars and spent a lot of time with a well made planar hybrid. The F200As easily match and in some areas surpass these speakers in speed and openess of the midrange. I would definitely get a listen before dismissing them totally.

Also as JLM mentions above if you're familiar with the shout of some single drivers. It's refreshing to hear one without it. I didn't realize just how shouty my previous SDs were until I got the F200As in the MLTL with BSC circuit inline. There's no way I could go back to a shouty driver in any configuration whether box or OB. Good luck with your future project.

[Bemopti123]

Especially module type speakers. I had a pair of multi ways that even had a shout that would tear your ears off on certain recordings. I hope the midrange isn't too bad on the F200As .

 I've owned a co ...

The prominence in the midrange that makes people state that SD drivers have such great delivery and palpability, is what I have come to conclude a distortion in the frequencies that makes one wonder about the design and the accuracy of the music being played.  

I agree with Nodiak, in that there are alternatives to constructing speakers implementing both OB and TL in design, giving the best compromise.

Nevertheless, I see that attempting to flatten acoustics humps of drivers, where they are the most audible, unless, one is a speaker designer or have experiment at length with x over contouring and cabinet design, will for most people out here not be a stroll in the park.

F200As are expensive in comparison to the B200s, almost 150-180 USD more, but the differences that you get are
1-decreased efficiency

the benefits being:

2-excellent linearity and fairly flat response, free of midrange peaks.

Sure, in contrast to peaky midrangey drivers, the F200As might seem boring, but what one get after $700 worth of raw drivers is excellent performance at the extreme ends of the spectrum and the lack of shout in the audible midrange WITHOUT the need of augumentation in the lower end or upper end.  That is something worth writing about.  

After living with this driver set on my FTAs for almost 1 year and counting, I can clearly say that the F-200As are superior to the plethora of commercially executed brand name speakers that I have heard in the last 16 years and the best part of it is that it is NOT an amplifier demanding speaker, being happy with either very high end SS, with High output or
very happy with low end Op chip power amplifier (20 watts+).  

Heck, I even tried a 9 watt per channel SET tube channel with these speakers and they sound excellent for the power rating.

F200As break the stereotype of single fullrange speakers, for what I have experienced.  There are other fullrange speakers, but they will need more work in order to get them playing everyday music.  

 

 

[Paul_Bui]

Ditto, JLM, GHM, and Bemopti123.  The F200A's midrange, especially when used with Bob Brines BSC filters, is so smooth I can listen to music all day long.  Quite opposite to "boring", I found them to be neutral, true to the tone of vocals and acoustic instruments.  The overall impression when listening to music through them is the antithesis of being "hot", "forward", and "in your face".

I used to use two REL Storm IIIs to augment the lower end of my other SD speakers, yet I found using them a compromise between getting a decent bass vs.  total integration of the entire spectrum.  Listening to the FTA-2000s for 30 seconds made clear to me that no sub is the best sub, that the low extension of the F200As would allow me to have the cake and eat it.  You just need to pump enough juice into them, and they will sing.

[Dmason]

Paul

I agree about "enough juice." It seems actually the more juice I used with them the happier they were; a 250 watt Hafler worked best. Unfortunately the F200A cannot be powered by such treasures as SE-EL84, 2A3, 45, etc., but they did come alive with current. Bemopti mentioned hearing them with a stout 300B. I think that might be the minimum bar set for DHT heaven with these things. I surely would have enjoyed that one. My biggest gripe with the F200A was the fact that the LFR heavily modulated the midrange, IMO. It is by no means something to be written off, nor the driver itself. Fostex has the advantage of economies of scale and research Yen that would embarrass any audio company on the planet. They do nothing half assed. Their half inch mastering decks for VCR cassette are legendary. I own one. Love it. Analogue, with the Red Wine Teac and the F200A were its best suit in my house.

[Bemopti123]

Paul
Bemopti mentioned hearing them with a stout 300B. I think that might be the minimum bar set for DHT heaven with these things. I surely would have enjoyed that one. My biggest gripe with the F200A was the fact that the LFR heavily modulated the m ...

the F200As are part of the studio line....implying can take a lot of power.  I remember seeing a Fostex studio monitor with three drivers per cabinet, a horn tweeter, a multi cell horn mid-low and a fat, 15" woofer...efficient, heavy, but chopped up with crossovers, allowing each driver to do its thing...but then, not quite single fullrange that foregoes x-cross networks and correctors.

Then, what is the different between something like the Fostex I have described and the older, Altec Voice of Theater speakers?

The only other driver that intrigues me with its design and execution is the Supravox 215 EXC field coil....that are voiced and engineered for OB...

So I guess OB design is on my future, until I get enough pretty pennies for them, I am as happy as a clam with the F200As on the FTA cabs.

[JLM]

I owned DIY'd Fried stereo passive subs circa 1980 that used 8 inch poly drivers.  Unfortunately I never tried bi-amping them because they simply overwhelmed any room size I could ever afford.  Fried said that they were capable of 114 dB at 17 Hz.  With my 20 wpc NAD 3020 receiver they filled a 20,000 cubic foot chapel with organ music wonderfully.  So I'm guessing that a good 6 inch woofer based TL may be all that most folks would ever need for music.

I and others tried the F200A with the little Red Wine Audio amps.  It sounded good, but it obviously benefitted from more power.  Several have commented of the positive synergy that single drivers, and the F200A in particular, has with chip amps.  I'm most satisfied using mine with Channel Island Audio VMB-1 40 watt monoblocks.

[nodiak]

I'd really like to hear the F200A. I've not been completely happy with any of the widerange drivers I've tried because of the shout. i'm giving some benefit of the doubt to the idea they need 100 or 200+ hours of breakin to calm down, so I'm trying to give some that time in a seperate room. I also need to give bsc a try on some. I like relaxed but clear mids, the SI coaxs have that but they are so big, they play plenty clear with the p2p xo I made but I could go a little livelier (quickness issue maybe). The Fostex 107 has the flatest response and least shout to me, I will try it with Tl bass soon.
The F200A may be a good driver for me, but the reality is I need high spl 20 hz in room as I listen to electronica and other low bass at loud levels at times. I think F200A is something I will have to hear. In my situation, so I wouldn't have both large mains and subs, I would need to use it in ob (above 200-300 ?) or smaller TL at 100hz+ cutoff. I could see this as a good solution. Especially from the descriptions you owners give of the sound. Of course if they were $400/pair I would've tried them already. Maybe the F120A could be used 100hz and up with ~ same mid qualities? But it shows an early upper roll off.
I've not doubted you guys with the F2000's, just think I need 10% more. And no, I wouldn't do the "learn to listen less loud thing"   , I bathe in concert levels at times, and have no neighbors to bother  . Not sure they could do that alone.
Good to hear about them. I'm sure I'll try them some time.
Don

[Dmason]

Don

I would say try em, who knows. Opinions are like a$$holes, everyone has one, and NO ONE is hearing the same thing. Horses for courses, you can throw down for a pair at Madisound and have a whole month to try and fry. The build quality alone is worth beholding; I cannot recall seeing anything built quite like the F200A. They weight ten pounds each.

 My thing is that they didnt work, For Me. My friend, for whom I built an F200A Bigger Is Better backloaded tractrix horn, is in love with them, and I will attempt to get him to sign on here, and give his impressions. This guy is using my 250 watt Hafler amp which is Class A for the first 15 watts, and it sounds pretty nice.

[nodiak]

Hey Dan, that's been the big lesson for me in all this, we all hear different. But we do travel in herds I think, with some intermixing. GHM and Paul enjoy gc's and the same dac I do, so it gives it some decent chance I may like the speakers they've settled on. Worth finding out when I can next afford to.
I took a look at the M8N, that could be a good tl, esp. in my medium small room. In the mean time I found a pair of Scanspeak 8554's for a great price, always been a Scans fan. Am checking for a good tl or mltl plan for them.

Don

[Dmason]

Don,

The best test equipment available is the Mark II Tympano-Cochleometer, and the best aspect of this equipment is the fact that every audiophool has his own personally calibrated test equipment. This is why, when someone points out someone else's  graphic test results in an attempt to prove me wrong, because Bob Brines says differently-and -he-oughta-know, for example, who gives a shit, because it has nothing to do with the results on MY Mark II. Most people actually dismiss this idea: the only ears to be satisfied, are their own. And then the "my speaker is better than your speaker" syndrome of argument sets in. This is why I completey ignore speaker reviews; just because someone indicates 'this,' doesn't mean, 'that.'  I was recently approached on the idea of writing equipment reviews for a major online audio emag we all know and love, and, -not interested. Too personal.

The HiVi M8N in its TL will provide yards of very grown up bass of an extreme high quality for anyone who needs it. Not a costly fix, and TL bass goes reeeellly well with open baffle systems too. The drawings are on DIY Audio, iffin you search M8N, TL, Jumbo, somewhere it is referred to as the Jumbo GM MLTL, calc'd by Greg Monfort, to whom we all owe much.

[jgpmhl]

I am grateful for the replies and the information. I have travelled some distance since my original question about the Fostex F200 and have visited the Visiton site following DMason's suggestion.  Ironically, the open baffle design they have for the B200 includes a (more expensive) 40mm woofer and requires a crossover, which is part of what I was trying to avoid (I am very new to this game).

The question of whether to use glass (19mm) is partly one of cost.  As much as it positively affects the WAF on an aesthetic level, a 45 liter box of North American glass came in at $650CDN a pop (which has an equal and opposite affect on the WAF on a fiancial level - was Newton amazing?).  I am waiting on a price for the Chinese product. I am also pricing 19mm glass for an OB design. I will at some point make a choice, pay the price, do (some of) the work, listen and let you know what I hear.

thanks.

[maxwalrath]

Fabaudio sent me this link last week. The plexiglass is probably a good deal cheaper than glass. Looks AWESOME to boot!

http://www.diyaudio.com/forums/showthread.php?s=&threadid=19883&perpage=10&highlight=&pagenumber=7

[JLM]

Nodiak,

Try test tones and a spl meter to determine if the F120A roll off would be an issue.  Of course off centerline it would beam less than the F200A or B200, so perhaps it's a wash anyway.  IMO there's no music beyond 15,000 Hz and precious little beyond 10,000 Hz (primarily cymbal shimmer).  Madisound shows the F120A as discontinued, but check.  A couple of guys around here have used it in Omega bass reflex designs and like it alot.  As long as you want to go down to 20 Hz, you'll need a sub anyway.  The main limitation I see for you is ultimate spls from either the F120A or F200A.

jgp,

Open baffles can be made of anything.  Personally seeing the back of the driver, wires, and possible crossover behind the baffle does nothing for me.  Solid core doors and countertops (laminated particle board, corian, or granite) come to mind.  With no significant pressure against it, mass and reflections (the sound from the other speaker) are the primarily concerns.  Unless you mount the baffles into the corners (and in effect turn them into infinite baffles) there little advantage to making them huge in order to try to squeeze more bass from them.  Again the B200, like nearly all "full range" drivers behaves primarily as a midrange/tweeter.

[mcgsxr]

jgpmhl - where in Canada are you?  If you are near TO, you are more than welcome to come over, and experience the b200 on open baffle in my listening room...

The other thing I would say is - you don't need that big woofer, or the box they suggest - see my gallery, in the Bunker Shots sub gallery, for how I have skinned this cat.

Also, amp synergy is critical for the b200, I have found best success with the JVC EX A1...

I don't have any other OB experience, with any other drivers, and at this point, am happy enough with things, that I am turning my focus on the last 2 octaves, and good sub integration...

[jgpmhl]

Thanks for the invite mcgsxr.  Unfortunately, but happily, I live in Calgary.  From what I saw in your gallery, you are very, very good with wood.  

For those who are curious about my original question, the Fostex recommended-dimension boxes in 15mm to 19mm glass (including the price of drilling the holes) ran from $233 CDN each for the 10 liter box to the $360 each CDN for the 45 liter box. This is wholesale pricing using Chinese glass (which is fine for the purpose but cheaper than NA sourced stuff).  For US$ prices, just multiply by .9.  Since the drivers run from $61 USD to $373 USD, I am not proceeding with that idea.  OB, 19mm mdf will be the next project, once I am done building the Shamrock Sound SE-1, in about 2 weeks I hope.  I am optimistic my old Onkyo can deliver the requisite juice for OB.


By the way, was that an FR125S I saw in your gallery?

Happy listening.