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Old 14th April 2006, 06:41 AM   #1
theseum is offline theseum  United States
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Default Fostex w/ Bass Reflex?

I was trying to find prices for Fostex drivers and I came across the following website: http://www.commonsenseaudio.com/fostextech.html who strongly criticize horn-based enclosure designs. (The site only sells bass reflex designed drivers but their criticisms seemed general.) Since all the other diy sites seem very pro-horn, I was curious: what's up with that? Are they wrong, and if so, why?

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Old 14th April 2006, 09:39 AM   #2
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Well personally, I disagree with them. Not because I'm biased toward horns -most horns aren't very well designed. But IMO, nor are their BR boxes. I remember trying to plug their approximate dimensions into MJK's MathCad sheets and coming away decidedly unimpressed with the response. You can get superior performance out of those units in a smaller MLTL enclosure. See www.quarter-wave.com for more -look in the projects section. Those cabinet designs are free too, and believe me, they work.
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Old 14th April 2006, 12:12 PM   #3
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My opinion of Common Sense Audio is less than favorable. There is no science here and the conclusions simply make no sense.Given that the discussion applies only to full-range Fostex drivers:

1. Properly designed horn cabinets DO work. Most horn cabinets are not well designed, but that is another issue. Horns will play louder than BR's or quarter-wave cabinets (MLTL's) and therefore are more "dynamic". Horns are larger and more intricate than BR's or quarter-wave cabinets for the same driver. Horns tend to be picky about design specs and are not tolerant to construction errors. As with everything else in audio, horns require compromises. One must take the good with the bad.

2. Quarter-wave cabinets are physically smaller than horns and bigger than BR's for the same driver. Well, that's not actually true, since you you really don't want to use the same driver in horns as you do in a quarter-wave cabinet. Use the FExx6 series for horns and the FExx7 series for quarter-wave and and BR's. (You can force an FExx6 into a BR, but IMO, the results are better if you use FExx7's) I have done quarter-wave cabinets for the FE167E and the FE207E with good results. I get bass well below 40 Hz and the great mid's than one expects with single driver speakers. As long as you don't require great SPL, quarter-wave cabinets give a great sound. They are best for small group music, jazz, voice, pre-Wagner classical.

3. BR's give you a mixed bag of compromises. They are the smallest cabinets, the BR's being stand mounted while the quarter-wave cabinets are floor standers. An FE167E BR is not truly full-range, since the F3 of a 24 liter cabinet is around 60 Hz. However, if you use a subwoofer and high pass the FE167E BR at 80-100 Hz, things change dramatically. With the bass load removed from the FE167E, dynamic range is increased dramatially and intermodulation distortion reduced significantly. This is the setup I use for HT -- four FE167E BR's around and a sub. Makes a lot of noise! An FE207E BR of 36 liters IS full-range. F3 is ~43 Hz and F10 ~35, numbers only slightly higher than a quarter-wave cabinet. Modest dynamic range, though. The general conclusion that all BR's have boomy and woolly bass is totally wrong. If the cabinet is designed correctly, a BR can have very listenable bass.

4. NEVER consider using two identical full-range drivers on the front baffle playing the same frequency range. You can use two drivers in a bipole or dipole layout, but never on the same side of the cabinet. The comb filtering between the two drivers will give you fits.

In conclusion, there are no flys on any one of the three cabinets discussed here. It is up to your musical requirements, your construction capabilities, and the size of cabinet you can stand.

Bob
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Old 14th April 2006, 12:25 PM   #4
Fuling is offline Fuling  Sweden
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Quote:
if you use a subwoofer and high pass the FE167E BR at 80-100 Hz, things change dramatically. With the bass load removed from the FE167E, dynamic range is increased dramitially and dramatically distortion reduced significantly.
Thats exactly what Ive observed too.
I run my FE167Es in 22 L BR cabinets and they sound quite nice on their own, but after some experiments Ive decided to XO at 80Hz (24dB active) to a pair of Scanspeak 8545 in 30L BR boxes.
I finished the subs yesterday and will probably get time to finish the active crossover tonight.
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Old 14th April 2006, 01:27 PM   #5
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I can just about cope with their semi-omni types with a forward and an upward firing driver. Pass re the cabinet design though -I haven't looked at those. Yet. But personally, I'd avoid their cabinets like the plague and build my own. At least that way I know for certain it's properly designed.

I don't buy some of their other comments too. Low powered tube amps do not only work well with full-range units. I've got a pair of borrowed Revolver RW45s downstairs which sing with EL84s putting out 3wpc. 10wpc would take your head off. As do the Castle Conway 3s belonging to my parents. And Monitor Audio B4s. And...

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Old 14th April 2006, 04:30 PM   #6
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My 1st venture into single driver was building the Commonsense MKII enclosures for FE206E`s, and I`m glad I discovered the single driver approach to speaker building. Since I`ve built the Fostex recommended horns for the 206`s and the are IMHO better. I also put Fe207`s in the BR boxes and they worked much better than the FE206`s in a BR. Eventually I`ll sell the Commonsense MKII boxes and build the Fostex double BR boxes for the FE207`s. I have built the double BR boxes for the FE127e`s and was happy with the sound, but if you`re going to take the time, build horns, maybe like the one`s Ron has designed. Everything I`ve heard abut them is positive and I would bet they are better than the Fostex horns, though a little more involved to construct.
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Old 14th April 2006, 04:49 PM   #7
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Bob is being much more polite about "Common Sense" audio than I would be.

Incidentally, I use FE207E in bass reflex cabinets. This is a reasonable implementation for apartment life, but certainly not "high fidelity" in terms of being able to produce realistic SPL across the bandwidth.

But the weird idea of slapping a whole range of drivers into bass reflex cabs without severe frequency compensation . . . has no basis in reality.
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Old 14th April 2006, 05:16 PM   #8
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And in addition to what Dumbass sais it can also have no bass in reality.....
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Old 15th April 2006, 06:04 AM   #9
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Quote:
Originally posted by Bob Brines

4. NEVER consider using two identical full-range drivers on the front baffle playing the same frequency range. You can use two drivers in a bipole or dipole layout, but never on the same side of the cabinet. The comb filtering between the two drivers will give you fits.
I thought some fullrange driver can be used so such as the Jordan JX6 and earlier the JX53.
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Old 15th April 2006, 01:34 PM   #10
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http://www.zillaspeak.com/FostexReflexCabsFE.asp

http://www.zillaspeak.com/FostexReflexCabsFX.asp

Peace,
Godzilla
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