Fostex FE168NS in a Frugel-Horn XL

Discussion in 'Speakers' started by purr1n, May 21, 2022.

  1. purr1n

    purr1n Burned out

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    I can't believe this much time as passed. A "few" years ago, I built a pair of Madisound's BK-16 back loaded horn hits and dropped some Fostex FE168EZ drivers them in. You can read about it here: https://www.superbestaudiofriends.org/index.php?threads/set-and-fostex-blh-speakers.1358/

    What I wanted to do next was build out the Frugel-Horns, the XL version that would fit the larger 6" drivers. I'm years late. There are some differences between the FHXL and BK-16. The Frugel-horns have the horn exit towards the back, are of an arguably simpler design, and have a longer section behind the driver with a choke near the exit flare. With respect to use, I gravitated toward the Frugel-Horn because it was designed to be used against the wall, instead of needing to pull them several feet from the walls. The BK-16, especially with the 168ES I sound to be midbassy and murky if not placed at least one to two feet from the wall. Not so with the FHXL where I had them placed against the the wall angled in a bit.

    The drivers most often recommended with the FHXL are the Mark Audio Alpair. I had used the Alpair 10P before and didn't like them. I gave them away or sold them for cheap to a SBAF member. The 10P did a lot of things right, they sounded smooth with respect to frequency response; however, they didn't resolve enough information, lacked immediacy and liveliness, and needed more power than what SET and many PP tube amps could provide. Maybe one day I will try the latest and greatest TOTL Mark Audio MAOP drivers, or maybe not because I don't think I necessarily want to drop solid-state True HiFi capable monoblocks into the mix. I already have too much crap in the house.

    Anyway, I've had always had success with Fostex, particularly their higher-end drivers, so why not? I ended up with the fairly new FE168NS (not ES) but accident because I didn't look carefully while I was on shopping Madisound's site. Oh well, but it turned out to be a happy accident. The NS are based on the limited edition SOL series. I have kept away from Fostex's limited edition series because I never know when one of my kids is going to poke a hole through a driver (boy and girl, but they fight like cats and know stuff over). The last thing I wanted to worry about was to be stuck with one expensive driver with no possibility of replacing the other.

    This is how I've set them up. @Boops: for the record, I decided on the EC Custom 45 for amplification. The PP Fisher amp very worked well, more heft, warmer tone, and takes the edge off the highs more. Ultimately the Custom 45 was more musical, spacious, and honest. Sometimes honesty may be too much for wide-banders's frequency response nonlinearities in the highs. I swapped out the neutral sounding DAC for the dark sounding DAC, the Yggdrasil LIM to obtain the best synergy.

    PXL_20220521_182236268.jpg

    Having be running BWC "big woofer club" speakers for a while, the first thing I noticed on the FHXL was mid and high bass not being anywhere what I was used to. However, everyone in the family agreed that somehow these diminutive drivers, through the clever science of leveraging the backwave to augment the low frequencies, offered a certain musicality that the JBL4698b were not capable. They also look much better in the living room, so I guess these are staying.

    The FHXL with the 168NS doesn't seem to be quite as punchy or snappy as the BK-16 cab with the 168ESs. On the other hand, the bass seems to extend more effortlessly, and there appears to be a lot more latitude for adjustment via placement of the speakers and internal acoustic stuffing. I have small weights over the top lid to get a good seal while I still tweak things. I'll glue the top in once I feel comfortable that I have gotten things right.

    PXL_20220519_221317986.PORTRAIT.jpg

    Obviously there are limits. They aren't going to be able to blow out your ears, and do it cleanly without distortion, like these. AC/DC at 100-110db effortlessly just ain't gonna happen. These are better for girl + guitarist, jazz, sparse electronic, chamber orchestra, and solo.
     
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    Last edited: Jun 14, 2022
  2. purr1n

    purr1n Burned out

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    One of the things that completely drives me nuts is the lack of very basic measurements on the Internet for these horn designs. Lots of talk on DIY forums. Lots of lots of people putting these together. All this takes effort, and a ton of clamps, a lot of sanding. With all this effort, no one can buy a cheap measurement microphone and post a frequency response? I always feel like people are trying to hide stuff.

    PXL_20220515_024321904.PORTRAIT.jpg
    PXL_20220429_023915817.jpg

    What I had gathered so far that the the FHXL was rather flexible and that a lot of drivers would "work" with it, among them the following: Fostex FE168eS, FF165wk, FE166En, FR168NS, and Mark Audio Alpair 10.3, 10p, MAOP among them. Well, I can honestly say that the Frugel Horn XL with the Fostex FE168NS works very well.

    By very well, I mean several things. The bass extension was surprisingly good, significantly better than the BK-16 with either the FE166En or FE168ES, to the point where I didn't feel the need for a subwoofer, although I still feel a subwoofer would be desirable. Unlike the FE168ES, I felt absolutely no need for an EQ network. The FE168ES regardless of enclosure, has a big plateau from 1kHz to 2kHz (the Fostex honk) that IMO requires a notch circuit and a peak at 7kHz which is more debatable.

    The FE168NS on the other hand, while not perfect, is more agreeable like the FE166En. There's narrow peak in the upper mids around 4-5kHz which I find less annoying than peaks and plateaus elsewhere. This possible because I could have hearing damage in that region which would result in a null in my hearing response. The FE168NS does beat the FE166En outright with respect to clarity, transient speed, resolution, and treble extension (I won't comment on bass extension because this will be a function of driver and horn). Despite the treble extension being better than the FE166En, he treble extension of the FE168NS does fall short compared to the FE168ES. Even with my old ears, I feel a supertweeter is warranted here.

    Here is the frequency response provided by Fostex for the 168NS. I am assuming this is with the driver mounted on an infinite baffle. Based on this, I thought I may not need a supertweeter because of the rising response and treble extension seemingly to 20kHz and beyond on-axis.
    [​IMG]

    However, reality seems to be different. Below is a close measurement with the microphone two feet away on-axis with the FE168NS mounted onto the FHXL cab with the cab against the wall. It looks like the highs start to take a dump after 13kHz.

    Fostex FE68NS in FHXL against wall
    Frequency Response
    Microphone 2' away on-axis
    upload_2022-5-21_14-55-31.png
     
  3. purr1n

    purr1n Burned out

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    Finally, here is a listening position measurement, per the above room photo.

    Fostex FE168NS in FHXL against wall
    Frequency Response
    In Marv's Texas listening room
    Microphone at couch listening position, speakers angled directly toward the microphone
    upload_2022-5-21_15-0-13.png
    1. Not quite B&K downward slope, but speakers are angled directly toward the microphone position. That being said, not as bright as the in-room listening position frequency response measurement would suggest. I'm actually fine with the speakers oriented like this and I hate bright. This goes to say that simplistic measurements won't capture everything that we hear.
    2. Given that this measurement is in-room and only 1/12 octave smoothed (typical presentation is 1/3 octave), the frequency response is remarkably smooth for a wide-bander.
    3. The FHXL design works amazingly well to fill in the lows, at least with the FE168NS. We getting down to 42Hz here, for a 6" driver. Not only that, the most important thing is that with many small speakers, the lows will start a gradual rolloff much higher! The FE166NS maintains the levels in the bass until the the drop without any gradual rolloff. Now we actually have some solid data on the Internet!
    4. Little bit of lift between 3.5-4.5kHz.
    5. High frequencies take a shit after 12kHz. As I mentioned, needs supertweeter. I'm not that old - yet!
     
    Last edited: May 21, 2022
  4. purr1n

    purr1n Burned out

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    For comparative reference purposes. I cannot express how important listening room measurements are!!! Sure listening rooms different, but trust me, most people's listening room measurements don't differ that much for a given speaker.

    Fostex FE166ES in Madisound BK-16

    Frequency Response 1/12 oct
    In Marv's Calabasas listening room
    Microphone at couch listening position, speakers angled directly toward the microphone, placed 1.5' away from wall
    upload_2022-5-21_15-41-7.png


    Fostex FE166En in Madisound BK-16
    Frequency Response 1/3 oct
    In Marv's Irvine listening room
    Microphone at couch listening position, speakers angled directly toward the microphone, placed 1.5' away from wall
    upload_2022-5-21_15-43-1.png

    Finally, measurements don't capture everything. The BK-16 cabs have a nice punchiness and snappiness that the FHXL do not have. It's not significant, but it's there. The Fostex FE166NS seem to be like a maxxed FE166En. I can't help but feel that perhaps the FE168ES is just a tee more resolving, especially with a good SET amp. The FE168NS has smoother frequency response like the FE166En, but does have a rising response which the En does not have. All three Fostex drivers mentioned could use a supertweeter. The FE168ES maybe can get away without one especially you are older and lost high frequency hearing. the FE166En definitely needs one. The FE166NS is somewhere in the middle.

    Finally some pictures:

    FE168NS (used here with the FHXL)
    upload_2022-5-21_15-51-8.png

    FE168ES/EZ
    upload_2022-5-21_15-52-6.png

    FE166En
    upload_2022-5-21_15-53-14.png
     
  5. purr1n

    purr1n Burned out

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    This should give you guys a sense of the internals.

    https://www.diyaudio.com/community/...3-flat-pak-mock-assembly-instructions.203264/
    [​IMG]

    --

    I wanted to see what was coming out of the horn in the back. That is I was curious to the effect of the horn. Here's a measurement from the back of the FHXL with the Fostex FE168NS. The speaker is against the wall slightly angled in. I put the microphone behind the speaker in between the flares. The microphone is on a tripod pointing down with the tip 1.5 feet above the opening.

    Fostex FE168NS in FHXL
    Frequency Response
    Microphone behind speaker in between flares point down1.5' above the mouth
    Speakers against the wall slightly angled in
    upload_2022-5-22_21-42-32.png

    Using the back wall for reinforcement, we're getting some very good output for a 6" driver. Results are consistent with the earlier measurement at the listening position where we are getting bass extension down to 42Hz. This is a really good design. As I said before, I don't miss not having a subwoofer, although it wouldn't hurt to have one. Any sub in this application would be a true sub playing stuff below 40Hz. This often yields much better results, more seamless integration, than crossing over at 80Hz, say with the KEF LS50.
     
  6. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    I have to ask... is that a commercial flat pak, or do you have someplace you were able to source the 3/4" baltic birch? I can't find any decent plywood in my area...:(
     
  7. purr1n

    purr1n Burned out

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    It's a commercial flat pack from https://www.bigwoodstudio.net/

    I'm pretty sure that the one I have is "baltic birch" or high-grade plywood. Supplies were kind of bad before the Russia-Ukraine war, but now I hear it's very bad. Not sure how much comes from the baltics or russia. Big Wood Studio is offering the flat packs now in maple/birch, which I don't think is as good.

    Anyone who wants to do this should get a chisel, a ton of clamps, a sander, and test fit everything together. CNC flat packs can only take you so far. Sometimes the fit is too tight or the wood isn't perfectly straight. The more woodworking experience that you have, the easier.

    P.S.

    So who wants me to be build the regular Frugel-Horn using the smaller 4" drivers and report back?
     
  8. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    Most definitely - that looks like 13 ply... regular is usually 5 (or maybe 7).

    That's an understatement... baltic birch (or russian birch/finish birch) was almost non-existent prior to Russian/Ukraine idiocy. The only real domestic competitor was appleply, which initially just became super expensive, but has now gone the non-existent route as well (I assume its all going to commercial clients).

    The "regular" 5-ply veneer plywood is pretty much crap for anything except cabinet carcasses or shelving. It warps too easily and has too many void.
     
  9. Boops

    Boops Friend

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    *Raises hand*
     
  10. Cspirou

    Cspirou They call me Sparky

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    I know you don’t have the BLH speakers anymore but any comment of transmission line vs BLH bass?

    Since Covid lockdown timber prices went nuts and plywood quality went way down. Caintuck Audio makes open baffle speakers and has said he only makes solid wood baffles now because he refuses to sell plywood in the state he finds it.

    For UK people Custom Cans has this available

    https://jfunk.org/wpc/product/fruge...r-full-range-speaker-for-mark-audio-alpair-7/
     
  11. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    I'm planning the same thing... solid wood (probably hard maple, but I'm also pondering walnut)
     
  12. CEE TEE

    CEE TEE MOT: NITSCH

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    Whoa, yeah I think I am used to 1/3 smoothing. At first, "1/12 octave smoothed" looked really sawtooth. Very interesting display, makes it easier to see chunks of sections such as the Madisound "honk" range.

    Seems like this driver + cabinet pairing really does the FAT of most music incredibly well with only the 6" widebanders.

    Then it's up to people whether to further complicate the system with a sub and/or super-tweeter if they even have the desire.

    @purr1n : What's the lowest wattage tube amp that you think can power these fairly well at a medium/reasonable listening level?

    Regarding the 4" version...is the estimation that it might save ~$300, will give up some low end extension (~50Hz?), plus save a few inches in each overall dimension?

    FE168NS 6": ~$550
    FHXL Kit: ~$650 (sold out at the moment)

    FE108NS 4”? ~$330
    Which kit? ~$550?
     
  13. dasman66

    dasman66 Self proclaimed lazy ass - friend

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    raises hand


    I have a set of FE108EZ that I got from @philipmorgan was going to build a mk3 for... and then decide if I wanted to do a BLH or XL for the FE168EZ that I picked up from @tommytakis
     
  14. EagleWings

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  15. Cspirou

    Cspirou They call me Sparky

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    @CEE TEE - Plans are open and I remember getting a quote from someone that does CNC wood projects for $220. That was back in 2018 though

    I do have fe108sol driver I haven’t put in anything yet. I’ll need to find someone around here that can help


    I always wanted to know why someone would want a small 4” driver in a gigantic cabinet like that
     
  16. purr1n

    purr1n Burned out

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    Last year I paid around $400 for what seemed like a few pieces of plywood sheathing, the super low quality kind, for flooring in the attic space. Yup, it's crazy. I'll get in touch with Bob @ Bigwoodstudios. Curious to the workability of the cabinet grade plywood.

    The FHXL with the 168NS are fine without a sub. I don't think I will bother will a sub, although I kind of want to build one from the big ~4.6 cu.ft. flat pack sold on Parts Express. There is a 18" woofer that will work beautifully for that size, better than the Dayton one suggested by PE, although the Dayton one ain't bad.

    Some days I miss the last half of the top octave. Other days I don't mind. In another decade, it probably won't matter for me. The good Fostex supertweeters are not only super expensive, but out of stock. I kind of want to do it just to have insanely priced almost unneeded supertweeters to cover 13kHz+ because of the sheer stupidity of the idea. I think they would look cool sitting atop the FHXL cabs:

    [​IMG]

    There wouldn't be extra complexity either. Just let the mains roll off naturally and a 2nd order HP XO (cap, coil, resistor) on the supertweeter would do the trick.

    I don't think the EC 45 Custom I'm using can do more than 2W at 1% THD so I am guessing 2W into 8-ohms would be the bare minimum recommendation. I am having no problems with what most people would consider moderately loud, although for this, I will need to move the volume knob to around the 3 o'clock position, almost maxxed, since the amp is fairly low gain. I can get Daft Punk Get Lucky up to almost 90db SPL sustained. It's more of a gain issue since the amp doesn't sound like it's running out of steam. (Keep in mind there is probably more gain available since I am using Roon's "replaygain" to keep levels consistent). I am kind of curious now and want to put the amp on the APx555 to see what kinds of distortion the amp is producing at various levels. The Fostex are a easy load, never dipping below 8-ohms, and usually way above that for most frequencies.

    SPL.png

    Not only the drivers, but the wood cost too. Add about $100-$150 more for the 6" version. I don't understand enough about BLH, and I am too lazy to pull up sim programs, so I have no idea. I do know that the smaller drivers have an Fs around 75Hz. The 168NS I'm using here has an unimpressive Fs of 60Hz according to the datasheet, but somehow I'm getting 43Hz -3db in the room. I'll do a quick impedance curve measurement of the 168NS in the FHXL, to see what the cab does with respect to the resonant frequency. If the 4" can do similarly, but maybe to 55-60Hz, then that would pretty darn good.

    The most important aspect which I cannot emphasize enough is no appreciable early rolloff in the bass starting up higher in the mid or upper bass. For example, the KEF LS50 does this in most rooms. This is why lots of people feel the LS50 sounds thin and needs a sub. (The LS50 shoved against a wall sounds muddy). A sub crossed over at a highish 80Hz, which is not a subwoofer IMO. It's a woofer.

    Anyway, this ain't the kind of speaker for cranking it up with rock or EDM. It's more for enjoying stuff like Ed Sheeran or Eva Cassidy in the evening at reasonable volumes that won't cause hearing loss. I actually have my system running at 1pm listening to stuff at 65db. One thing about these small Fostex drivers is that they still resolve fine detail and sound lively at lower volume levels.

    P.S. The pro sound guys' preferred SPL meters are the vintage RatShack with the meters. Not fancy lab grade stuff from B&K or GRAS. Meters > digital numeric displays for this kind of work. LOL, I think I've had mine since I was a teen.
     
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    Last edited: May 23, 2022
  17. Cspirou

    Cspirou They call me Sparky

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  18. purr1n

    purr1n Burned out

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    1/12, which is basically almost next to no smooth, will look jagged, particularly in real listening rooms. Here's 1/3 octave smoothing which we more typically see in Stereophile, etc.

    Fostex FE168NS in FHXL against wall
    Frequency Response 1/3 oct
    In Marv's Texas listening room
    Microphone at couch listening position, speakers angled directly toward the microphone
    upload_2022-5-23_17-36-0.png

    And another one after I moved the speakers a little bit. The prior one was with the speakers toed-in so the on-axis intersection crosses in front of the listening position. I tend to so this to get a strong center image, especially if not sitting center on the couch. This one is with the speaker toed-in so the on-axis intersection crosses at the listening position.

    upload_2022-5-23_17-37-35.png

    BTW, this is the KEF LS50 (META and non-META) in JA's listening room. Source is Stereophile. My guess is that the LS50 are pulled very far from the walls well into the room. It mirrors my experience with the LS50 and KEF's variants of them in most rooms.

    upload_2022-5-23_21-50-59.png
     
    Last edited: May 23, 2022
  19. purr1n

    purr1n Burned out

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    Now whoa! This is totally funky. Let's take a look at Fostex provided datasheets and compare to the measured impedance curve with the FE168NS in the FHXL horn.

    Fostex FE168NS
    Impedance Curve
    I am assuming on a simple baffle / free-air
    upload_2022-5-24_22-42-52.png
    Note resonant frequency of driver is at 55Hz. Note that datasheet specs day 60Hz. I'll haven't done a free-air measurement myself, but let's assume it's around here.


    Fostex FE168NS
    Impedance Curve
    In FHXL horn (stuffing per photo below)
    upload_2022-5-24_22-26-24.png
    [​IMG]

    So instead of one resonant frequency, we end up with two. This is actually quite similar to what we see with ported boxes. Also, it's what I kind of said before on the FH being kind of like a cross between a horn and transmission line design.

    The frequency of the box is 50Hz, lower than free-air Fs. This is also confirmed by the fact that the lower bump is not as high as the upper bump. When this happens, it is an indicator that the box resonant frequency is lower than that of the driver. Given the extent of the difference, I'm actually guess the free-air Fs of the FE168NS I have may be closer to 60Hz.
    upload_2022-5-24_22-35-3.png

    The FHXL, stuffed as is, is a good design for the FE166N driver. It extends the bass down ideally.
     
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