I have considered using my FE206e facing rear, in a sealed bi-pole with a smaller/smoother wide range facing forward and 12” u-frame open baffle bass below. This is not small in width (14”at the base, tapering going up), and taller, but to my senses feels smaller, and the over all volume would be significantly less than the almost 3cu ft back horn that I use now----which feels bulky.
I have done this sealed bi-pole arrangement (in prototype---separate boxes etc) with rear firing FE167e and front firing FE127e, and will build a finished pair this winter. These will be about 6” deep OA, above the U-frame woofer.
On this design I use the whizzer cone equiped FE167e on the rear because the smaller single cone FE127e is more coherent sounding to my ears and has more, and smoother, treble response. The passive components used to blend the responses of the drivers, and other details, are omitted here for brevity in this post.
The sealed volume for the FE206e should only be about 6 or 8 liters larger (guessing) than that for the FE167e, which is about 9 liters, Q about .707
This arrangement gives a soundstage that is much like my cone driver di-poles of the same general dimensions. Adjustable L-pads (or resistor networks) on front and rear FR drivers could be used to move the soundstage forward/back and alter the imaging/depth ratio. More output toward the rear tends to give a deeper spatial sound field illusion, but precise imaging is reduced.
I have done this sealed bi-pole arrangement (in prototype---separate boxes etc) with rear firing FE167e and front firing FE127e, and will build a finished pair this winter. These will be about 6” deep OA, above the U-frame woofer.
On this design I use the whizzer cone equiped FE167e on the rear because the smaller single cone FE127e is more coherent sounding to my ears and has more, and smoother, treble response. The passive components used to blend the responses of the drivers, and other details, are omitted here for brevity in this post.
The sealed volume for the FE206e should only be about 6 or 8 liters larger (guessing) than that for the FE167e, which is about 9 liters, Q about .707
This arrangement gives a soundstage that is much like my cone driver di-poles of the same general dimensions. Adjustable L-pads (or resistor networks) on front and rear FR drivers could be used to move the soundstage forward/back and alter the imaging/depth ratio. More output toward the rear tends to give a deeper spatial sound field illusion, but precise imaging is reduced.
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Thanks for the excellent idea. I shall give my mothballed 2nd-hand 206e a chance at life, backing up F120A-Fonkensteen/supertweeter or another FR. Would appreciate more details on blending etc.
I apologize that this is getting away from the simplicity of single driver full range. Hopefully the fact that the thread is old, gives us some leeway to venture away from the OP's original question.
10/19/22 wchang said:
“Thanks for the excellent idea. I shall give my mothballed 2nd-hand 206e a chance at life, backing up F120A-Fonkensteen/supertweeter or another FR. Would appreciate more details on blending etc. “
I started a reply and realized that it would be helpful to know what degree of knowledge and experience you have with passive crossover components and/or active equalization. Not knowing that, I wrote the following:
Planet10 said: Doc Bottlehead would suggest putting them in a sealed box and then adding a woofer with a plate amp brought in below the natural sealed roll-off of the FE206e (i don’t have a sim handy but a good guess would likely be <10 litres and somewhere around 125 Hz).
The above concept is basically the same for adding bass to the bi-pole. Dave's guess at the box size was closer than mine---not a surprise.
The main benefits/differences of this bi-pole approach are greater output/dynamics and a very different sound field/sound-stage. The challenges of building are likely many and varied.
Using the driver parameters for the FE206e, that are already in my download of WinISD (free), I was surprised to see that a tiny 3.51 liter cabinet modeled with a Q of (.702). It did not change things radically to go bigger—the roll-off started earlier and was more gradual, with output at 100hz decreasing. So, pretty much any small box that you could fit it into would get you started.
It would be good to stack the boxes so that the drivers are as close as possible to the same vertical height, with the F120A at ear height, if possible. The FE206e faces rear-ward. Put the stacked boxes 1 meter or more from the back wall, and clear of sidewalls.
For experimenting, it would be very helpful to have a separate integrated amp for each pair-so you can adjust relative levels. The result will be bass-shy, regardless.
Without bass and lower midrange support, the FE206e in combination with the F120A-FONKENSTEEN, will be very, very bright in the upper midrange. However, having the FE206e pointing toward the back wall should lessen the unfortunate aspects of its less than ideal dispersion. Also deceasing the output of the FE206e could help to adjust the overall frequency balance. Or—you could find compensation circuit on the internet for this driver to lower the mid range.
When/if you feel this approach has promise, and you have woodworking skills/tools, you could make a single cabinet for the drivers. I found very little in the way of existing Bi-poles of this type on the internet. Lots of home theater surround speakers, but not much in the way of systems for stereo that do the same job as open baffle di-poles. Di-pole radiation is out-of-phase , front-to-back. Bi-pole is in-phase.
At some point when I build my final cabinets, I hope to find the time to describe the build in it's own thread. I suppose it should go in WAW/FAST forum?
If you have a powered sub-woofer you could try using it, but you will not likely get good integration, because the roll-off of the two pair of Fostex will not be an ideal match for that of the sub, but it is worth a try to see if you like the overall effect. Most likely there would be a lack of upper bass impact and low mid warmth. Also most subs will sound slow/muddy compared with the Fostex, I think.
A 15” or 18” U-frame open baffle sub with a high sensitivity pro woofer, with it's own amplifier, would be a decent way to go about providing bass. Usually it is said that the Qts of the woofer should be high (approaching 1.0) for open baffle bass, but I have had good luck with a woofer Qts of around .35, using a little more LF boost.
I have used an inline 10 to 20 mH inductor coil to good effect when integrating each of a pair of these U-frame woofers into a stereo pair of full-range speakers. The bass tends to fall off at the (single peak) frame-loaded resonance of the woofer. My fs=30hz 18” woofers are useful down to about 35hz.
Getting something like this right can take a long time. It is helpful to have a trusted pair of high quality full-range speakers to use as a reference for frequency balance. Also great to have a measurement mic(less than $100) and software (some free).
10/19/22 wchang said:
“Thanks for the excellent idea. I shall give my mothballed 2nd-hand 206e a chance at life, backing up F120A-Fonkensteen/supertweeter or another FR. Would appreciate more details on blending etc. “
I started a reply and realized that it would be helpful to know what degree of knowledge and experience you have with passive crossover components and/or active equalization. Not knowing that, I wrote the following:
Planet10 said: Doc Bottlehead would suggest putting them in a sealed box and then adding a woofer with a plate amp brought in below the natural sealed roll-off of the FE206e (i don’t have a sim handy but a good guess would likely be <10 litres and somewhere around 125 Hz).
The above concept is basically the same for adding bass to the bi-pole. Dave's guess at the box size was closer than mine---not a surprise.
The main benefits/differences of this bi-pole approach are greater output/dynamics and a very different sound field/sound-stage. The challenges of building are likely many and varied.
Using the driver parameters for the FE206e, that are already in my download of WinISD (free), I was surprised to see that a tiny 3.51 liter cabinet modeled with a Q of (.702). It did not change things radically to go bigger—the roll-off started earlier and was more gradual, with output at 100hz decreasing. So, pretty much any small box that you could fit it into would get you started.
It would be good to stack the boxes so that the drivers are as close as possible to the same vertical height, with the F120A at ear height, if possible. The FE206e faces rear-ward. Put the stacked boxes 1 meter or more from the back wall, and clear of sidewalls.
For experimenting, it would be very helpful to have a separate integrated amp for each pair-so you can adjust relative levels. The result will be bass-shy, regardless.
Without bass and lower midrange support, the FE206e in combination with the F120A-FONKENSTEEN, will be very, very bright in the upper midrange. However, having the FE206e pointing toward the back wall should lessen the unfortunate aspects of its less than ideal dispersion. Also deceasing the output of the FE206e could help to adjust the overall frequency balance. Or—you could find compensation circuit on the internet for this driver to lower the mid range.
When/if you feel this approach has promise, and you have woodworking skills/tools, you could make a single cabinet for the drivers. I found very little in the way of existing Bi-poles of this type on the internet. Lots of home theater surround speakers, but not much in the way of systems for stereo that do the same job as open baffle di-poles. Di-pole radiation is out-of-phase , front-to-back. Bi-pole is in-phase.
At some point when I build my final cabinets, I hope to find the time to describe the build in it's own thread. I suppose it should go in WAW/FAST forum?
If you have a powered sub-woofer you could try using it, but you will not likely get good integration, because the roll-off of the two pair of Fostex will not be an ideal match for that of the sub, but it is worth a try to see if you like the overall effect. Most likely there would be a lack of upper bass impact and low mid warmth. Also most subs will sound slow/muddy compared with the Fostex, I think.
A 15” or 18” U-frame open baffle sub with a high sensitivity pro woofer, with it's own amplifier, would be a decent way to go about providing bass. Usually it is said that the Qts of the woofer should be high (approaching 1.0) for open baffle bass, but I have had good luck with a woofer Qts of around .35, using a little more LF boost.
I have used an inline 10 to 20 mH inductor coil to good effect when integrating each of a pair of these U-frame woofers into a stereo pair of full-range speakers. The bass tends to fall off at the (single peak) frame-loaded resonance of the woofer. My fs=30hz 18” woofers are useful down to about 35hz.
Getting something like this right can take a long time. It is helpful to have a trusted pair of high quality full-range speakers to use as a reference for frequency balance. Also great to have a measurement mic(less than $100) and software (some free).
206 are lots of fun in a "K12" Karlson - they seem to like the rather large (~32 liter) rear chamber. I would make the cutout for a 12" then use an adapter ring/board with the 206 mounted to the front of the adapter.
A single vent could play stronger than Karlson's distributive 6-slot array.
A single vent could play stronger than Karlson's distributive 6-slot array.
Thank you for the detailed reply, I read it a few times and will pay close attention to upper bass dynamics and low mid warmth as you have warned. I have many of the tools you mentioned such as amp-pair, plate amps, fast subs, and xo/notch filter parts. Less experience with active xo or dsp. Plan on getting more measurement tools, been getting by with tone-sweep and listening. Right, couldn't find much info on bi-pole stereo. Your answers will be of help to others as well, I'm sure!
Freddi said:
“206 are lots of fun in a "K12" Karlson - they seem to like the rather large (~32 liter) rear chamber. I would make the cutout for a 12" then use an adapter ring/board with the 206 mounted to the front of the adapter.
A single vent could play stronger than Karlson's distributive 6-slot array.”
Could you point me towards a primer on the Karlsons?
What would you say about why you like them? Do they do anything to improve the beaming/dispersion issues with whizzer cone drivers?
“206 are lots of fun in a "K12" Karlson - they seem to like the rather large (~32 liter) rear chamber. I would make the cutout for a 12" then use an adapter ring/board with the 206 mounted to the front of the adapter.
A single vent could play stronger than Karlson's distributive 6-slot array.”
Could you point me towards a primer on the Karlsons?
What would you say about why you like them? Do they do anything to improve the beaming/dispersion issues with whizzer cone drivers?
I don't know why this bi-pole stereo thing is not done more. I got the idea because I wanted to use the FE127/167, that I am nostalgic about, and they have full vintage Planet10 mods. The 167 plays louder, but I prefer the 127's sound overall. Neither can play very loud/clean on it's own. So, why not put both in small sealed cabs, as front and rear bi-pole and add bass support? I had pleasing success with a multi-way dipole----how different would a bi-pole be? Heck, you could even flip the phase and have di-pole response (which would mostly just change any bass response the drivers produced).
I find that most of the really admirable qualities of the small/wide range FE127 are intact in this arrangement. As with a di-pole, the sound stage is deeper, and imaging somewhat more diffuse. To me it simulates a live sound nicely---the extra dynamics help here too.
So far, it seems best to separate the woofer from the small front firing full-range by somewhere between 18” and 28” O.C. Closer together ends up sounding more like a large woofer multi-way, than the special/sweet single driver coherence. Helps here to blend (cross-over?) below 180hz. I have not discerned lobing being an issue. Stereo woofers are ideal, with vertical alignment.
I tried adding a mini-AMT tweeter above 8khz, facing forward, but it took away from the FE127 coherence; so I pointed it at the ceiling, and I like the effect.
Come to think of it, a few months back I had unknowingly done something like bi-pole. I scrounged six near-identical cheaper Loewe (?) 6x10 "redback" DEW-alnico radio speaker drivers whose sweetness I really liked, made tissue-box-sized "enclosures", the main pair openback "OB-U", the next pair sealed with 3mH LPF and pointing sidewise, for BSC purpose and (supposedly) widening the soundstage. The last pair for low bass boost was ineffective but otherwise the FR was very nicely balanced, and much better sounding than adding BSC/notch to the main drivers. Creme-brulee-crust sound.
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Synesthesia?
I remember seeing opposing side firing woofers on a build/design by Dave from Planet10. They are bi-poles, just not front and back, and his were doing support woofer duty, with a wide range facing forward, as I remember.
From Dave I first got the idea that BSC could naturally (my words) be accomplished by crossing to a midrange in the baffle step "band"(dependent on baffle width), with appropriate filter slopes.
Creativity and experimentation are fun for me, and a good way to learn; and with DIY speakers it really helps if the woodworking/crafting part is something one enjoys.
The idea of adding drivers to fill-in is attractive to me, while subtracting with filters is less so. Realizing it may be less precise, and there may be lobing issues, for multi-driver systems I like low order crossovers and large driver overlaps, when the drivers are sufficiently broad-band.
Though it may be naive, I have long imagined combining full-range type drivers that have inherently complimentary dips and peaks---not very sophisticated from an engineering POV. But in a bi-pole, with drivers that have way less than ideal dispersion characteristics, there may be a possibility of healing the overall reverberant soundfield power-response---if these terms are being correctly applied here.
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I just took the brownies out of the oven big sniff
About a dozen years ago I posted on audiogon an "Audio Nirvana" experience, playing simultaneously the very same F120A in a bookshelf BR, stacked on top of a cheap Monitor Audio 2.5 with "gold dome" but PP midwoofer. It turned out their frequency response curves were complementary, convex and concave. Several people chimed in at the time with similar anecdotes. Foolish me broke up the pairing... Well ten years later, I came upon two very special but flawed 5" speakers, a Michael's Audio/Hifi-bird using "UK drum paper" with incredible micro-dynamic linearity (brought to mind Axiom 80) and top extension but a very thin midrange, and a Correct "P-610" (which was a legendary Japanese studio monitor) with downsized cone but oversized magnet giving a beautiful midrange and nice lows. Given a second chance nirvana I jumped on it. This "stack" puts the musicians in the room with so-called palpable presence, not pin-point but embodied with believable dimension....
I'm with Freddi.
They'll do fine in the Dutch Karlson, not overly big and the slot makes for wide dispersion. Good for a party speaker, cone hardly moves. Johnny Cash used the big Karlson which is an unwieldy contraption and if memory services me right Meatloaf used them too in some concerts.
So, looks like sealed for the woofers, and short t-line for the FF85wk. Probably 5.5" Silver Flute woofers. The Silver Flute line is such a bargain (in USA) at Madisound. Warm, with tight bass.
I really like the Silver FLute W14. The larger ones ar eharder to work with. 4, 8, 16Ω availability is nice, and they are a bargain.
FF85wk & 4 W14 for not much more than a couple hundred dollars.
dave
FF85wk & 4 W14 for not much more than a couple hundred dollars.
dave
I want to try the W14.
I have used the W17 in a small sealed t-line above 100hz, and in an MLTL sub to support Fostex FE166e in back horns (low output, but good 30hz to about 100hz---then ripples above that).
Also used W20 in an approximately 20 liter PR loaded box. Rolled off below about 50hz, maybe due to the 10” PR cone mass/tuning. Bass was fairly tight and clean. Need to revisit that one, it has Planet10 EnABL treated FF85wk for a mid/tweet---plus a helper tweet that makes the high end a little too hot. The original design used the FF85 w/o the extra tweeter.
I have used the W17 in a small sealed t-line above 100hz, and in an MLTL sub to support Fostex FE166e in back horns (low output, but good 30hz to about 100hz---then ripples above that).
Also used W20 in an approximately 20 liter PR loaded box. Rolled off below about 50hz, maybe due to the 10” PR cone mass/tuning. Bass was fairly tight and clean. Need to revisit that one, it has Planet10 EnABL treated FF85wk for a mid/tweet---plus a helper tweet that makes the high end a little too hot. The original design used the FF85 w/o the extra tweeter.
By the way, Silver Flute is available on taobao, directly from the company's subsidiary (part-numbers SF 3-digit-diameter -1506X). I haven't tried them but they are recommended by bbs. hifidiy.net users. May I ask, how good are they really, say at resolving deep bass drumroll (Dvorak New World Symphony really a bass-drum concerto)? Can they keep up with really fast FR transcients? Thanks.