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Old 8th November 2005, 02:17 AM   #1
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Default Yet another 'help me choose a driver' question...

I'm looking to build a high-efficiency loudspeaker. My budget is very tight for at least a year (kids in college, blah, blah...). For these reasons, and because it seems like it might be fun, I'm considering a 'full-range' system. It may not be single-driver in the long run, but it will for the short-term.

I'd like the efficiency to be around 94 dB.

In the short-term, I can more easily deal with limited bass than rolled-off high frequencies.

From what I've read, a FE108ez would be ideal, but for it's relatively low efficiency.

I'm pretty adept at woodworking and not afraid of a complex cabinet (blh, etc.).

I'm 48, so the >15k range is probably gone, but I am an imaging freak to a significant degree. Beaming is probably not a good long-term compromise.

Any suggestions or advice? I'd really appreciate it!

I guess my inclination at this point is to go with a FE166e or the FE168ez. I wonder if the 168 is really worth the extra $.

Many thanks.

Paul Ebert
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Old 8th November 2005, 07:37 AM   #2
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Ooh, lots of options here. The F108ESigma is wonderful, but, as you've already noticed, it's not particularly efficient. You can boost the efficiency at the bottom end (invariably the biggest problem) by horn loading it, but I don't think you'd get a comfortable 94db / 1w out of it. If you can live with that; here's a few options for you to consider (in no particular order):

1) The under-rated (unjustly, in my opinion) Fostex Factory horn, which you'll find here: http://www.fostexinternational.com/d...108ez_encl.pdf

2) A Swan. Personally, I think they're appallingly ugly, and anything less like a swan I've never seen, but to each their own! http://melhuish.org/audio/DIYRH8.html


3) If you have corners to load it, the Buschorn MK2, with the compression chamber blanked off; Dave (planet10) had drawn a lovely diagram of it here: http://homepage.mac.com/tlinespeaker...chhorn-Mk2.gif

4) Again, if you have corners to load it, a reduced scale version of Terry Cain's Bigger Is Better TQWT (the original article is here: http://melhuish.org/audio/DIYTQ8.html ). We've been discussing this cabinet recently, and I suspect the baby Sigma could do very well in a smaller version of this load. Probably best to read the whole thread, which you'll find here: Terry Cain's BIB -why does it work and does anyone have those Fostex Craft Handbooks? The reduced scale dimensions I came up with are near the end.

For the larger drivers; is the FE168ESigma worth the extra over the FE166E or its FE167E brothers? Yes, but quality costs -the FE168ESigma is not cheap. If you can stretch to it, it has a smoother, but more detailed mid and high end than the cheaper drivers, which are however, outright bargins at the price, and will comprehensively clobber most any commercial speaker under 1000UK. None of these drivers, by the way, will need any kind of assistance at the top end with a tweeter etc.

What options with the larger drivers? Again, in no particular order

1) The Fostex Factory horn[s] for the FE168ESigma, and the FE166E: http://www.fostexinternational.com/d...ez_enclrev.pdf and http://www.fostexinternational.com/d...6e_enclrev.pdf

2) An enlarged Bigger Is Better cabinet, with the same caveat as before -you need corners, or at the very least a rear wall to load them. See the above link for optimised dimensions using this driver.

3) For the FE167E, Martin King's wonderful Project 2 ML TQWT. I've built 3 pairs, which says it all, though it needs a bit more power due to the correction circitry reducing a bit of its efficiency. My all-time favourite design, and possibly the best budget speaker that will work well in 99.9% of all rooms in the world. We all owe Martin a great debt anyway for cracking the mysteries of the TL speaker. The BIB box mentioned is the one and only exception I make to my rule that all TLs should be initially designed and optimised in his MathCad worksheets, which gives some idea of how highly I rate Martin and the work he has done for the DIY community. Pity he's not mentioned in print, though I have had a letter published in this month's Hifi World regarding this lack of recognition, which annoys me not a little. http://www.quarter-wave.com/Project02/Project02.html

Hope some of this helps or gives ideas. What size room do you have, what sort of music do you listen to, and where will the speakers be positioned in the room? We can help more if we knew, as we could better suggest what is worth pursuing in your particular circumstances and what is best avoided.

Regards
Scott
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Old 8th November 2005, 02:43 PM   #3
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Thanks for the information, Scott!

I almost exclusively listen to classical. Within that genre, everything but opera. Large scale orchestral music is important (I need a Mahler fix every once in a while). But, I do not play too loudly. More often, I have to listen at low volume for the sake of other household members (they sleep more than I do).

My current room is 14' by 22' with an open floor plan and I cannot use the wall for loading due to a fireplace that juts into the right side. My current speakers are two feet in front of the fireplace on the right side and about 4 feet from the wall on the left. My soon-to-be remodelled basement could work better (same size, but corner / wall loading is possible). However, my wife is reluctant for me to move the stereo down there - she's afraid she'll never see me. Also, I would not sacrifice imaging for bass.

I have no problem augmenting the main speakers with a large woofer box or a woofer added to the main driver. Really, the main driver only needs to go down to 100 hz as far as I'm concerned. But bass augmentation might have to wait a while.

I have no problem with a back horn, but I'd rather it not be too wide (I'd like it to be < 21" wide, say). I like the idea of a double back horn. Are there any non-commercial double back horns for the 108ez or 168ez? How hard is it to come up with one's own design?

I share your opinion about Martin. As you can probably tell, I'm a novice at this, but he's been very helpful to me both through his worksheets and his personal sharing of his knowledge.

Oh, I don't think a swan is of interest. It is an ugly duckling (IMO).
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Old 8th November 2005, 04:33 PM   #4
sumacSK is offline sumacSK  Slovakia
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Hi,

My recommendation will be Visaton B200-on simple open baffle it will give you response at least down to 60Hz and it is considered to be in the same category (if not better) with Fostex F200A or supravox 215 sig. bic.

Good luck Martin
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Old 8th November 2005, 04:57 PM   #5
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Quote:
Originally posted by Scottmoose
For the larger drivers; is the FE168ESigma worth the extra over the FE166E or its FE167E brothers? Yes, but quality costs -the FE168ESigma is not cheap. If you can stretch to it, it has a smoother, but more detailed mid and high end than the cheaper drivers...
Is this an instance of something sounding better than it measures? Because, frankly, I was a bit put off by the frequency response graph for the 168, which seemed anything but smooth to me - at least above 2k.

I've read in several threads about how wonderful the FE108EZ is, but I'm concerned that my room and music will not work for it (say, in the factory recommended blh). My current amplifier is a 40 watt class-a SS amp, so that should be sufficient. When I replace that I hope to have SET options available or perhaps a First Watt amp, but I guess I'm most concerned about the small xmax (and not just for bass).

Thanks, Scott!

Paul
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Old 8th November 2005, 08:16 PM   #6
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Originally posted by sumacSK
My recommendation will be Visaton B200-on simple open baffle...
Thanks, Martin! That is an interesting driver. One that I had not heard of before. A full-range open baffle. Sounds very interesting.

Wouldn't the baffle have to be quite wide to go so low? I thought that an OB needed to be about a meter wide to get as low as 100 hz. That's too wide for me. I can go tall, but even two feet (61 cm) is probably not going to get past the wife.

But, I'll think about it.

Paul
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Old 8th November 2005, 10:22 PM   #7
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Your more than welcome, Paul.

Yes, the 168 does sound much better than it measures, a paradox, but there you have it. It's not so unusual in this regard, many full-range drivers like Lowthers have worryingly ragged measured responses but sound spectacular. I don't own a pair (can't afford them) but I've heard them, and rate them very highly indeed.

With a room of that size, I think we can forget the baby FE108ESigma -even in a hefty horn, it's just not going to shift enough air to go loud. Your music won't be a problem, except for the big orchestral pieces, but the room is a bit large, unless you listen in the nearfield alone -a 4" driver just isn't going to shift much air, unless mounted in a truely massive horn (think Nelson Pass' J-Lo and go up from there!) The Fostex Factory FE168ESigma horn could well be a good way forward for you; as you've no corners, and probably no wall loading, sadly, the BIB box isn't going to work, so that's out. I like these factory Sigma horns however -I've yet to hear one I haven't thought was good. Either that, or Martin's Project 2 ML TQWT with the diploar subwoofers from Linkwitz Phoenix project would be a devastating system like few others.

I'd agree too that open baffle with sub-augmentation is a good way forward, providing you can stand the cost. Once tried, few go back.

One of the (natural) mistakes many people make is the assumption that an open baffle needs to be wide to produce bass. Well, it does in itself, because of the progressive acoustic cancellation front to back, but that can be negated through active equalisation, so the baffle does not necessarily have to be particularly wide. It does mean, however, that you need separate power-amps for each channel -gain some, loose some, the usual way of the world. Have a look at Siegfried Linkwitz' site if you haven't already: www.linkwitzlab.com for more -much, much more. You won't get through this little lot in a hurry, but it's staggering stuff, and as stunning a site as Martin's, albeit covering rather different areas (and as a massive supporter of Martin and his work, you can imagine that I don't say that lightly). This project using a couple of Diatone drivers (haven't seen any debate about them for a while) is worth a glance too: http://melhuish.org/audio/DIYBF1.html

Last wild card to think about: a line array using some inexpensive full-range drivers. That's another debate entirely though -let us know if the thought appeals, and we can discuss it some more.

Cheers for now
Scott
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Old 9th November 2005, 12:26 PM   #8
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Originally posted by Scottmoose
Last wild card to think about: a line array using some inexpensive full-range drivers. That's another debate entirely though -let us know if the thought appeals, and we can discuss it some more.
It seems to me that there would be considerable problems with comb filtering with a line array of full-range drivers, unless they were quite small.

With regards to a blh, I've played around with Martin's blh worksheet and find the impulse response alarming. I understand why it happens (delay of the backwave going through the horn). Is this sonically detectable?

Regarding an OB design, I've wondered if one could simplify the needed equalization by selecting a woofer with greater efficiency than the full-range driver. For example, if I used a FE108EZ down to 150 hz, say, and a woofer rated at ~102 db (or more), the extra 12 dB efficiency of the woofer could be used to provide baffle compensation. The equalization then becomes a matter of sloping the woofer response down to match the FE108EZ at 150 hz. The cancellation is first-order, isn't it?

Thanks!

Paul
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Old 9th November 2005, 02:53 PM   #9
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Yes indeed, that's one of the downsides to using full-rangers in a line array. Normally, I'd reckon on a 6 1/2" drive unit being the maximum practical for a 2 way array. With full-rangers, I wouldn't go above 4 inches (3" better), and make sure they were very close together. And power-tapered. With a couple of dipolar subs in support, this could work well.

Horns are funny old things. The impuse response can look decidedly unpleasent, I agree. However, is the delay itself audible? Not really, no, at least not in my experience. More of a problem is that most BLHs are actually transmission lines at low frequencies (if they weren't, they'd produce no bass at all, unless they had a mouth the size of your living room. Literally.), and it's the transition between TL and horn loading that causes the most problems; I suspect this is one of the causes of the horn colouration some people speak of. As a rule, people tend to either love horns or outright loath them; I'm in two minds -I've heard some that are great, others... well, not so good.

Regarding your idea for open baffle woofers and using greater sensitivity to aid matching -you could be onto something there, I'm no expert on OB designs, TLs are more my thing, but it might be worth following up. Best person in the world to ask is Siegfried Linkwitz himself; his email is at the bottom of his site's home page, and I'm sure he'd advise where possible. As I say, I'm no expert, and it would be wrong of me to pass comment either way, other than observing that I have an ominous feeling it's not as easy as that.

Best
Scott
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Old 9th November 2005, 03:11 PM   #10
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'd agree too that open baffle with sub-augmentation is a good way forward, providing you can stand the cost. Once tried, few go back.
Thats what I am working on right now and hopefully by the end of this coming weekend I will be able to listen to them.
Visaton B200 open baffle playing full range but with a ~90 hz 3db filter on the amp that powers them and a pair of Rythmik Audio servo subwoofers, sealed, one in each speaker.

Andrew
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