T-amp with FE207E in MLTL, BR or DBR? - diyAudio
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Old 7th June 2006, 01:31 PM   #1
irss is offline irss  Lithuania
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Default T-amp with FE207E in MLTL, BR or DBR?

Dear FR experts,

Presently I am using modded SI T-amp. I am thinking whether to build ML TL enclosure with Fostex FE207E, or DBR or BR enclosure with the same driver. ML TL seems to be too simple to be very good
Furthermore, I have read few comments that DBR or BR enclosure work very well with FE207E and T-amp...especially for bass freaks. My listening levels are from low to moderate (not loud).

Should I consider those types (DBR/BR) of enclosures, specifically having in mind that I like bass, and I have no possibility to put the speakers in the corner (the room is 20 m), or should I go with ML TL project...?

I would greatly appreciate your help.
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Old 7th June 2006, 02:11 PM   #2
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I don't think you can lose with any of those options. It's a matter of degree... sort of like red wine or white... sake or beer.

It's all good and will make a fine sounding system.
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Old 7th June 2006, 02:20 PM   #3
irss is offline irss  Lithuania
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Thank you, Godzilla, for your encouragement. I suppose choosing the easiest project (MLTL) would be the wisest alternative
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Old 7th June 2006, 06:03 PM   #4
Dumbass is offline Dumbass  British Antarctic Territory
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I have FE207E in 45 liter vented cabinets. I have 2 to 3 ohms (can't remember exactly) series resistance because of the large cabinet size.

If I were starting from scratch I would build something like Martin's project 5 MLTL:
http://www.quarter-wave.com/Project05/Project05.html

If you want something a little more "daring" in looks you could build a tapered version like project 6:
http://www.quarter-wave.com/Project06/Project06.html

I have spent close to a couple of years with these drivers; here are my suggestions based on personal experience:

1. Phase plug
I simply use the Decware mod, i.e. a wrench socket. Smooths out highs quite nicely:
Click the image to open in full size.

2. Wall placement
My conjecture is that because of the inevitable beaming effect, full-rangers are happier with boundary placement than, say, the typical dome-tweeter "monitor" type speaker. With wall placement, you all but maximize the speaker's efficiency and you don't have to use baffle step compensation. Just keep clutter to a minimum between the speakers -- a soft piece of furniture like couch might work nicely, though.

3. Overtoeing
Even with the phase plug, the driver sounds best slightly off-axis. The best solution is the toe in the speakers so their axes cross in front of the listener. In a typical listening situation of the listener and the two speakers making an equilateral triangle, this means the speakers are toed in about 45 deg. This makes for a really nice, wide, stable stereo image.

4. Zobel
With the t-amp, you might want to experiment with a Zobel across the speaker leads; I'm certainly no expert, but the t-amp might be happier driving a zobelized load. I don't think the effect would be dramatic.

Have fun with the drivers. I think you'll be happy.
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Old 12th June 2006, 03:12 PM   #5
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Interesting words Dumbass,
I have been playing around with these drivers in Martin's MLTL and, as you say, it seems that corner placement negates the need for a BSC. I have recently taken out all the stuffing too and found that there is an improvement at low listening levels (I never have them above moderate levels)...think I'll put some felt on the walls later though.

I also found that dramatic over-toeing works wonders when you are trying to get the widest sweet spot....mine are crossing well in front of the listening position and the best spot is about 15' away where you get the reflections off the side walls of the room, especially for the base response.

I have Planet10's phase plugs and would always recomend that mod before anything else...what a difference!

Currently there is no series resistance or zobel between them and my Amp6 but there is further experimentation to come.....when I get the oportunity and time of course.

Lee
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Old 19th June 2006, 07:25 PM   #6
irss is offline irss  Lithuania
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Presently I'm ordering fe207e drivers from madisound to go in the ML TL enclosure, and I thought to order capacitors for BSC circuit. Do I really need to go for exotic and fancy caps such as mundorf/hovland 3uF, or solen caps will be more than enough? As I have read, polypropylene film caps are preferred over metallized polypropylene caps...

...in Lithuania we have a bit of troubles with quality caps, therefore I would appreciate your advise whether I should go for an expensive caps or 'regulars' would be fine for BSC circuit.
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Old 19th June 2006, 09:14 PM   #7
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Quote:
Originally posted by irss
Presently I'm ordering fe207e drivers from madisound to go in the ML TL enclosure, and I thought to order capacitors for BSC circuit. Do I really need to go for exotic and fancy caps such as mundorf/hovland 3uF, or solen caps will be more than enough? As I have read, polypropylene film caps are preferred over metallized polypropylene caps...

...in Lithuania we have a bit of troubles with quality caps, therefore I would appreciate your advise whether I should go for an expensive caps or 'regulars' would be fine for BSC circuit.
Hi chaps, just to update, currently I have no stuffing except for some felt to deaden the box. I also added 3 ohms of series resistance on each channel using about 1 metre of 1mm nichrome wire.
No BSC or Zobel, removing them seemed to give clarity to the highs at such low levels (louder levels seemed better with the BSC)
This seems to be the best setup at low listening levels (so as not to waken the little 'uns).
The sweet spot is a good 6 metres away with generous toe-in. This is the best position to appreciate the base in my room which is long and narrow.
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Old 20th June 2006, 12:22 AM   #8
Dumbass is offline Dumbass  British Antarctic Territory
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Quote:
Originally posted by irss
Do I really need to go for exotic and fancy caps such as mundorf/hovland 3uF, or solen caps will be more than enough? As I have read, polypropylene film caps are preferred over metallized polypropylene caps...
For moderate values like 3uF, you can often find NOS military spec paper-in-oil caps for reasonable prices on eBay. (Perhaps shipping would be a problem in your case.)

For me, this is a good way to sidestep the audiophile capacitor wars.
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Old 22nd June 2006, 01:57 PM   #9
irss is offline irss  Lithuania
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Thanks mates for your help.

Few Fostex experts (who have been doing enclosures for some time) asked me why wouldn't I go for fostex recommended Double Bass Reflex enclosure. Their arguments are simple:

1. Why to do something different, when the producer of drivers recommends the best option for driver, specifically taking into consideration the fact that the Fostex has done extensive research before recommending it? If Fostex considered ML TL to be the best choice, it would have recomended it.

2. Why would one go for enclosure (ML TL) which requires the correction circuit, when one can have a real fullrange driver system (that is Fostex recommended DBR) without any filters?

Well, and here I am...lost again

I shall flip the coin.
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Old 22nd June 2006, 03:27 PM   #10
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Who says that the recommended DBR for the FE207E doesn't need a filter? Look at the response graph on the plans. It shows the classic baffle step response. It needs a BSC filter just like almost all other tall thin cabinets, unless, of course, you push the speakers up against a wall. I don't understand the concept that a thin sounding speaker with ear-bleed upper mids is preferable to a balanced speaker with a firm bottom end just to avoid a simple BSC filter.

Seriously, consider the 35 liter BR. Anything from 35-40 liters will work. I have a pair of these running right now that work pretty well without a sub, so long as you don't have to have THX levels.

Fostex does not recommend a MLTL because Fostex designers aren't into MLTL's. Look at their product line. They are into quasi-back horns, or as GM calls them, big mouth TL's. I've put 207's in MLTL's and they work just fine.

Bob
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