[floobydust]

 Okay, as some existing threads have gone somewhat off topic and over the edge recently, I decided to start a new thread. In some ways, the other threads were getting some good detail. They, unfortunately, crossed the line of civility to an extent between some posts. I don't want to get into that again. Trying to extract some of the good bits however, I think it warrants some additional discussion around the drivers and appropriate enclosure designs for them.

 Now having said this, everything that follows is my personal opinion. I'm not exactly new at this and have close to 5 decades of experience... and my Dad was heavily into audio back in the 50's and still is today even though he's pushing 80 next year. I've also had the luxury of working in a small recording studio decades ago when everything was pure analogue and have kept my hand, ears and serious $$ into this for a long time now. Live music is something I grew up with... and have played classical trumpet for a long time as well... so I'm no stranger to what live music sounds like.

 So... if I look at what I consider to be valuable input from the other threads (again, my personal opinion), it would seem logical to "assume" that smaller FR drivers are perceived by more DIYers as the preferred driver based on popular opinion. From my view, there is mainly one reason to venture into the FR driver realm.... that of coherency. I have owned two pair of Quad ESL-63 electrostatics over the past 20+ years, the most recent set (which I still have) are the US Monitor version and have recently been completely rebuilt by me with some upgrades. The Quads provide a single point source, have a single driver mechanism and no crossover. To this day, they still provide a very credible reference for "music" reproduction. As a result, I've not had any desire to own any multi-driver speakers in a long time.

 Now that I've dumped a lot of fairly useless info on everyone, let's get to a bit more meat. I have multiple drivers in my possession today... they include many Fostex drivers... the FF85K, FF125K, FE126E, FE108E-Sigma, FX120 and F120A. I'm also fortunate to own a pair of Feastrex D5NF drivers... but I acknowledge these are beyond the means of most DIYers lurking out here. When I consider the better ones from Fostex, I would narrow the list down to the F120A, FX120 and FE126E, the last being somewhat of a price performer.

 It's clear that many have used the FE126E (and no, let's NOT get into that debate again) in various designs. It's a very good all-around performer, has good sensitivity, etc. In my view, it has a tendency to "shout" at higher SPL levels. This is upper midrange response and tends to grate on my ears overall so for me, I would not listen to it at high SPLs despite it being able to crank out some 3-digit SPL levels.

 The FX120 and F120A are completely different drivers, despite coming from the same zoo. The cone material is different, the dust cover is different, the surround is different and these sport a very nice die-cast allow frame compared to a stamped steel frame. Finally they are an order of magnitude more expensive, with the F120A more than doubling the FX120 cost. In many ways, it's not a fair comparison to the very cost-effective FE126E. The main difference between these two is the magnet assembly as the FX120 has a large ceramic magnet and the F120A has an Alnico magnet assembly.

 While I won't try to technically distinguish between ceramic magnets and Alnico magnets, it has been my personal experience that Alnico provides a leap in low-level detail, clarity and an overall sense of musical realism compared to ceramic magnets. I think the best comparison for this is the FX120 versus the F120A as they share much in common sans the magnetic assembly. One other advantage is they don't exhibit the upper midrange shout noted earlier. The down side? Well, a solid 5-6 dB lower sensitivity than the FE126E and a lower power rating.

 Moving to enclosures, the FE126E is certainly easier to "fit" into various enclosure types and has a tendency to excel in multiple designs. The FX120 and F120A are more limited in what makes an effective enclosure, so your options are less but this becomes more of a flexibility trade-off than a sonic loss in my view. Either way, if I were to rank them in pure musical terms, the F120A is first, followed by the FX120 and then the FE126E. This is NOT the beginning of a flame war, only my personal view... I've listened to all three extensively using an extremely well-done 45 triode SE amplifier with no feedback. I've also put the Quads into this same environment.... albeit they play quieter, the findings are not affected in my overall ranking, and yes, the Quads still win overall.

 Now here's where we get to what I consider the Achilles' heel for small drivers, low frequency extension. There is only so much you can do with small drivers regardless of loading, enclosure design, etc. However I can manage a decent 45- to 50Hz in my listening room, which isn't too bad. The good news... you can augment the last 1-2 octaves and not create a significant crossover related problem, especially in contrast to trying to bring a tweeter and/or midrange in the critical bands where coherency suffers (again, the Quads excel here).

 So, to wrap up the first post in this thread, I prefer a smaller driver with good linearity, good accuracy and exceptional low-level detail with clean dynamic response. I'll tolerate the deficiency in the lower octaves and augment it with a good sub-woofer design rather than try a larger driver where I may need to augment the upper octaves where the phase alignment of the drivers and the phase problems introduced by the crossover do more more damage where it's more perceptible to the ear.

 Okay... let the flames begin! And of course, very sorry for such a long post.. my bad.

 Regards, KM

[jrebman]

Appreciated, Kevin.  No need to apologize for long posts, especially ones with good info.

You're really driving the Quads with the 45 SET?

-- Jim

[floobydust]

 Hi Jim,

 Yes, I have driven the Quads with 2-watts! They are also an easy load and around 86dB sensitivity... then again the F120A is only 89dB sensitivity and the FE126E is 93dB. Fortunately my listening room is dead quiet but still, low level listening is what you get. Did you get your Fonkensteens yet??

 Regards, KM

[jrebman]

Kevin,

No on the Fonkensteens yet, and as much as I'd like to be hearing them, I'm also respectful of Bud's time and appreciate all the extra work that's gone into making them as good as they can possibly be -- and that includes all the work by Chris and Dave as well.

It's been a really great project and I think we've all had a lot of fun with it so far, so we'll just let it take it's natural course so nothing gets rushed.

Take care,

Jim

[JohnR]

Nice post

The FX120 and F120A are more limited in what makes an effective enclosure, so your options are less but this becomes more of a flexibility trade-off than a sonic loss in my view.

So, out of curiosity, what enclosure type have you found to work well with these drivers?

[planet10]

e F120A is only 89dB sensitivity and the FE126E is 93dB.

Actual measured is a bit less, 87-88 & 92 dB respectively

dave

[planet10]

So, out of curiosity, what enclosure type have you found to work well with these drivers?

Highish Q tends to point to sealed, aperiodic (including classic TLs), maybe ML-Vs, and with the success of the Fonken-steen, large high-resisitance vent BR.

dave

[floobydust]

 Thanks Dave,

 I didn't do actual measurements on the various sets. I did take some relative measurements and found the FX120 pair to be off by 1dB between them. The F120A pair were spot on between them. I would also note that the bulk of Fostex drivers are currently made in China. The F120A is still made in Japan and the rear label states "Laboratory Series" on them. The same applies to the T90A super-tweeters I have. I was going to cut them in at around 13- to 15KHz but never did as the F120A doesn't need the added support.

 John,

 For the testing and listening I did, I built a simple 10-liter ported box similar to Fostex recommendations. I used 3/4-inch plywood for the sides, top/bottom and 3/4-inch MDF for the front and rear. The sides, top/bottom were lined with BlackHole pad and the rear was lined with BlackHole pad 5. The front had a 1/4-inch thick cork sheet added to the front and trimmed for the driver frame. This resulted in the driver being flush with cork pad. Granted, not the most creative enclosure but it works well for what it is.

 Regards, KM

[Ed Schilling]

Dave,
Not to argue the point and it may be insignificant but I averaged the last 60 126E I have measured. Using the "added mass" method and measuring the mass to .01 gram......WT3 spits out 93.4 dB.............none above 94.8......none below.....93.0.
These are new and untreated....running them in did not change this significantly. Are your numbers for your modded drivers? Maybe that could account for the db or so difference?

Some units ,   Bandor and Jordan (I think some models) for instance, actually use the air in a small sealed box as part of the suspension. Putting them in too large box or other loadings actually hurts power handling significantly. These will NOT work well in anything but a small sealed box. But I am sure that will not stop many from doing something else and probably liking it.

Many other drivers will benefit from this but will never be tried that way......just too easy I guess!

Bandor are the best I have ever heard for SQ......they have limitations, but near field in a small room they are heaven, in a tiny, tiny box. Subwoofer required.

http://www.bandor.com/products_frame.htm

Ed
* from Jordan******The low frequency response of the JXr-6HD has been extended to a remarkably low limit to enable its in-box performance to be directly matched to appropriate, high quality sub-woofers. To achieve this, the conventional rear suspension has been omitted and the system resonant frequency and 'Q' values are set primarily by the acoustic suspension provided by the volume of air enclosed within a small box. This technique also provides a significant reduction in low frequency distortion.

edit**** I realized I forgot to "bold" the important parts.

[planet10]

Not to argue the point and it may be insignificant but I averaged the last 60 126E I have measured. Using the "added mass" method and measuring the mass to .01 gram......WT3 spits out 93.4 dB.............none above 94.8......none below.....93.0.
These are new and untreated....running them in did not change this significantly. Are your numbers for your modded drivers? Maybe that could account for the db or so difference?

Indeed i was misremembering.... Stock drivers with ~150 hrs on the bench playing radio... average of the last 80 units

80 FE126 Stock average values                                 

Name     Fs        Re       Qms       Qes       Qts       Vas      Mms      Sd        dB      comp         BL

Average   94.62   7.11    5.28      0.44       0.41       6.26     2.72     65.04    92.89   1.05E-06    5.11

Spread    13.2%   4.2%   29.0%   26.3%   23.8%   37.4%   20.1%   0.0%     1.8%     37.4%     16.0%

Max       100.26    7.20    6.22     0.52      0.47       7.53     2.96      65.04     93.71   1.26E-06    5.46

Min         87.78     6.90    4.69     0.40      0.37       5.19    2.41       65.04     92.02   8.67E-07   4.65

Modding the drivers i loose about a 1/2 dB

dave

[Graham Maynard]

http://www.susan-parker.co.uk/susan-speaker-sphere.htm

Neat eh ! 
Cabinet life expectancy - 1,000 years !  Make a good heirloom.

Cheers ...... Graham.

[strider]

http://www.susan-parker.co.uk/susan-speaker-sphere.htm

Neat eh ! 
Cabinet life expectancy - 1,000 years !  Make a good heirloom.

Cheers ...... Graham.

I like the caveat the best "drivers may need refurbishing before this..."