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In Reply to: Re: Sure it's not your amp .... posted by Paul Joppa on January 3, 2007 at 15:53:13:
Hey Paul,Thanks for your review, I found it very helpful.
I'm considering the sealed system you mention, having seen a similar (or perhaps identical) system recommended on the Bottlehead site (you may be familiar with it*) for the S.E.X. amp.
I see you ran the FE166 full range despite having the subwoofer, and the Bottlehead site recommends the same thing, saying that running it full range makes for a better blend with the sub.
Could you expound on that a bit? It seems that running the FE166 with a highpass filter (at say 120Hz) would unburden the SET quite a bit, reduce IM, etc. So I'm tempted. But do you find that with the bass cut out of the fullrange there is no way to blend the sub and the fullrange well, and that this problem overshadows any gain from unburdening the SET amp?
I'm just curious what your experiences were.
Thanks for your contributions,
George
*yes, my tongue is in my cheek
Follow Ups:
Haha! Yes, I was referring to the "S.E.X.y Speaker" design which we've posted for anyone to use. We came up with that after we were unhappy with the ported box.I wanted to make this as easy as possible, thinking of customers who might have bought our cheapest amp, so I kept it simple. But I do believe an additional crossover would be an improvement. Here's the deal:
1) The original is a sealed box with fullrange drive; this makes a second order (12dB/octave) rolloff and the small box gives a Q in the range of 0.5 (Linkwitz/Riley) to 0.7 (Butterworth) depending on the amp's damping factor. This matches well with a second order (12dB/octave) powered "sub"woofer, such as the less expensive models from Parts Express. (I put "sub" in quotes because I am using them as woofers, and the smaller/cheaper ones don't go down to 20Hz... :^)
2) With an additional, external line level crossover, 12dB/octave, this same system would produce a fourth order (24dB/octave) acoustic crossover, which I expect to have significant further benefits. I've not been able to prototype this yet, but recent developments make it more practical and I expect to have something to listen to in the next few months. This becomes complicated because of the variety of subwoofers. Some are 12dB/octave and would need an external 12dB/octave filter. Some are actually 24dB/octave and need no additional filter. And some have a fixed 12dB filter (usualy in the 100Hz-200Hz range) plus another, variable 12dB filter. These are sold as "24dB/octave" but it's not easy to determine exactly how best to make them act like 24dB/octave L-R filters at a particular frequency. In some cases it's nearly impossible to determine what the device actually does in this respect. And with a 120Hz crossover, you really need to get it right - just playing with the controls is not likely to get you an optimum.
That's not to even address the idea of a separate sub crossover, used with a "normal" amp. Which I'd love to do - a handy way to use that solid-state boat anchor you gave up on when you discovered SET magic!
Just as I expected--you were gracefully referring to your S.E.X.y speaker. Nice.You're comments are just what I needed. As I chart my course into the SET dimension, I'm balancing SET-nurturing simplicity with my lust to tweak. I find your speaker idea ideal (grin), for it makes some dimensions easy and elegant (e.g. sealed box), while the active crossover allows me to play in what I hope are some relatively benign ways.
For example, my preamp needs coupling caps anyway, so all I have to do is undersize them correctly and, presto!, high pass filter for the SET. And if the sub needs additional slope to its low pass filter, I'm thinking I can add an inductor at it's input without worrying about messing up the mids and highs. (Comments invited.)
Do you think some experimentation with inductor values, checked with a Radio Shack SPL meter and some test tones would allow me to tune the crossover transition reasonably flat?
I'm also pondering the idea of putting a 4'x4' mask around the Fostex box, to eliminate the need for a BSC circuit (no WAF at the moment), but I could just bite the bullet and build the circuit.
Regardless, it seems to me your speaker idea leverages some nice synergies, and is easy and cheap too boot. (Did I mention that I like cheap?) It appears to me that the Fostex FE167E/FE166E have just about the flatest mid/high response of any Fostex speaker, and the sub/sealed-box design unburdens the Fostex, yields ample bass, and sidesteps all the cabinet building/tuning issues (though for some that pursuit is its own reward). Sweet.
Thanks again, and Peace and Prosperity to you and yours.
than FE166 for BR. Both have better Q-parameters for such usage.
Granted, the FX120 is somewhat max SPL/dynamics limited with it's
modest 89 dB sensitivity and 10W rating, but look at it's response
curve, x-max, etc. Allegedly a sweet little driver. Im about 90%
finished constructing a pair in BR enclosues (will use padded-down
T-90 supertweets) and will give full report when I get a few days
use on them.About the FE167: well, the Q-parameters look much better than
the 166's for BR usage, but still the smallish x-max which,
as I agree with Paul, is surely a major limiting factor in high
SPL play quality. I do notice, however Bob Brines seems be pretty
happy with the FE167 in small BR, and indeed offers such a unit
for sale. I think Paul is right on the money about the FE166 requiring
excursion limiting which a horn or small sealed enclosure affords
to play clean at higher levels, thats for certain. Personally,
I'm not a big fan of whizzer cones, though I understand that
many seem to like the FE166/167. I have a pair of unused FE206's
new in box which I simply don't like, and will probably end up
selling for a pittance --Just care for them. Was tempted to cut
off the whizzers to see if the glare would abate --but frankly lost
interest.-T.M.
Personally, I would be waiting a couple of days for the release of the Hemp Acoustics drivers... there should be a FR6.5 released. From what I have learned thus far, these should provide a significant alternative (in the way they present music) to Fostex, if a little a more expensive (I am guessing).Importantly for me, the development and manufacturing of the Hemp Acoustics drivers appears not to EXPLOIT that which is euphemistically termed "globalisim".
Not associated w/ Hemp Acoustics in any way.
Kind regards
Raymond
Ultra-consumers: Spending money they do not have to buy things they do not need to impress people they do not like.
I love the Asylum, you can't get away with anything - too many smart people are paying attention!Actually, I think the ported box did use an FE-167E. I agree it's better suited, even with some source impedance (SET damping factor). The cones and voice coil appear to be the same, and they sound extremely similar to me - so the main differences are the Q and efficiency.
Hey Tom,Thanks for the info! I think you know this, but just to clarify, Paul and I were talking about sealed boxes to limit low frequency excursion, so your BR comments wouldn't apply there.
I certainly agree the FX120 has a gorgeous frequency response, perhaps the best I've seen, just a little dip at 20K, nice with your tweeter. Unfortunately the 89dB sensitivity is a deal breaker for me--what are you going to use to drive yours?
I'm no fan of whizzer cones either, and was torn over the FF225K, which has high efficiency, smooth response, and a nice rolloff at 11K that just begs for a tweeter. But I finally decided against it because of the upward tilt to its response.
So I'm leaning towards the FE166E as the best mid-through-high spectral balance in a 94dB (or better) efficient speaker, whizzer be d***ed. And it'll be in a sealed box and used with a sub, so low end is not an issue. Thanks for your insights--and any others.
Yes, the FX120 is obviously dynamics limited unit. I intend to
use mine almost as studio monitors: closer listening distance in
smallish room at modest SPL. I'm hoping they will be nice and
well rounded sonically with good imaging in the little BR boxes.
I'm not looking for/expecting anything under 70hZ or 100dBWm
performance from them. They will be used mostly with a 4 watt
P-P triode conn EL84 amp, and an 8 Watt triode conn KT88 SET.I am also presently in the process of assembling a pair of
Madisound BK-16 horns with the FF165K. I'm hoping for a more
punchy and dynamic presentation with these. naturally I
expect them to be much more colored and to image less well
than the FX120 monitors, but they should provide some more
drama and zing with the 5dB greater SPL and power handling.I will give a full comparison/report here when I get it all
lashed together and a few days of listening. I really don't
expect either set of speakers to do much of anything below
about 70Hz. I may very well end-up not really liking either
much. I have some reservations about what how the aluminum
dust caps may sound. We'll see...Good luck with your FE166's. Sounds like the sealed cabs and
subwoofer augmentation might be a good route.-T.M.
Hey Tom,You make sense to me. I hope you share your review of your FX120 system--it could be ideal for me as a personal/nearfield system.
I'm pondering on Paul Joppa's insights on acoustic (sealed box) versus electronic (crossover) high pass filters.
I'm going to look into using my FE166E in a BR box, instead of sealed. Then I could use them fullrange sans crossover for low level/power listening, and with an electronic crossover and subs for high level / big bass listening. Might offer the best of both worlds... hmmm...
Thanks, and have fun,
George
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