MLTL Design with Fostex FE206E Questions

[JeffG]

Hi guys.. I am planning a new project. Am thinking of using Mr. Kings ML TL Design with a slightly different twist. I have seen many that used the Fostex FE206E, and seemed to be very satisfied. As I am also using a Fostex driver, I really like them.

So whats different.. i want to use these with a lower power tube. I would like to use to of these Drivers per enclosure. Also add a tweeter - if possible. I dont want a top mounted super tweeter, so I am considering Fostex FT96H..

Questions..

1.) Possible to use two Full Range Drivers in MLTL?

2.) How would using the two drivers, affect Box size, and driver placement?

3.) I have not seen any info on bracing in the MLTL. What is the best method?

4.) Best to wire the two FE206E's series or parallel?? Also which way would give best power handling results??... in case I ever switch to one my high power amps

Any and all thoughts and suggestions welcomed and appreciated.

Jeff

[joe carrow]

Originally posted by JeffG
Hi guys.. I am planning a new project. Am thinking of using Mr. Kings ML TL Design with a slightly different twist. I have seen many that used the Fostex FE206E, and seemed to be very satisfied. As I am also using a Fostex driver, I really like them.

Good luck! I think you're in for some good times..

So whats different.. i want to use these with a lower power tube. I would like to use to of these Drivers per enclosure. Also add a tweeter - if possible. I dont want a top mounted super tweeter, so I am considering Fostex FT96H..

That's an interesting approach. I know you're supposed to get an SPL increase of 6 db with two drivers; but the impedance halves. Can your small tube amplifier deal with a low impedance load?

It should also be pointed out that the ML TL design does not increase efficiency like a horn; rather- the stuffing required to kill pipe resonances will decrease efficiency.

On the other hand- if you're willing to go for two drivers, you could put each in it's own TL, and tune each line to its own frequency such that the peaks and nulls from one compensate for those of the other. This could reduce the need for batting, and you still ought to get all the benefits of two drivers.

Questions..

1.) Possible to use two Full Range Drivers in MLTL?

2.) How would using the two drivers, affect Box size, and driver placement?

Did you have a look at this page on Martin's site? http://www.quarter-wave.com/General/Two_Drivers.pdf

This page should be applicable to your question. However, I think that it's a good idea to take a look at seperate lines for each driver, tuned to compliment each other. You'll want to search for that, and if we're lucky someone will share some knowledge of that here.

3.) I have not seen any info on bracing in the MLTL. What is the best method?

4.) Best to wire the two FE206E's series or parallel?? Also which way would give best power handling results??... in case I ever switch to one my high power amps

Any and all thoughts and suggestions welcomed and appreciated.

Jeff

The best way to wire the FE206Es? I really think that will depend on your amp. I don't know much about amplifiers, especially tubes. What it boils down to (you can read more at the link above)- is that parallel gives greater sensitivity (but lower impedance)- and series gives greater power handling (at higher impedance).

I think that you might want to take a good look at your amplifier. What it's capable of, how attached you are to it, and how loud you want to go. It could be that the unmodified FE206E design will give you plenty of sound from a couple of watts.

You may have noticed that many people feel that there's a certain synergy between the fostex fullrangers and the DIY gainclone chipamps. If you're not dead-set on a tube, you could save the trouble of reinventing the wheel using two 206Es by building a more powerful gainclone, and get all the SPL you want out of a single driver.

If you're willing to go that route, and you already had the budget for four 206Es, the next thing to think about would be an FX200 instead. I hear that they have good bass.

Much of what I have heard about full range speakers is that they sound good (mostly?) because they get rid of crossovers, and also because they are close to acting like a point source. Same deal as a coaxial driver; which some people are crazy about. That's something in favor of going for a single driver, and maybe a tweeter crossed as high as possible

The last thing i'd like to tell you about the design part- Martin is friendly, and very approachable. Drop him an email Also, I'll be watching the thread.

About construction- I would STRONGLY recommend that you consider how easy it is going to be to tweak crossovers, change wiring, etc- when you design and build these things.

Right now I wish I was already set up for bi-amping, or changing to a different crossover- that sort of thing- and I would have a hard time doing it. A small external box (until you think you've got it right) or else an access panel, or a permanently external crossover (with individual connections for each driver) will save you from a lot of hassle.

Good luck, I hope this helped.

[JeffG]

Thanks Joe. I really appreciate the insights. I am not sure I fully understand when you say place the additional drivers in another tl. Would this create four enlcosures instead of just two?

I have looked at Martins Worksheet regarding two driver enclosures. That particular worksheet seems to deal with an enclosure other than a MLTL. I will investigate it further. I really dont understand how he comes up with cross-section dimensions though.

Anyway. I really dont know, if I NEED two drivers. BUT I really want two drivers. Also I think I can xo the tweeter high enough, that it should blend nicely. I am using a T90A super tweeter with another Fostex Driver (FF165K), and that worked out real nice. I have just heard so many good things about the FE206E.. I just gotta get some!

I will do some more research on the two driver enclosure idea though. Been trying different search criteria here, but no joy so far.

Anyway thanks.. Any more ideas or thoughts always appreciated.

Jeff

[joe carrow]

Originally posted by JeffG
Thanks Joe. I really appreciate the insights. I am not sure I fully understand when you say place the additional drivers in another tl. Would this create four enlcosures instead of just two?

No, it would not have to create four enclosures; you can have two seperate transmission lines in one enclosure; they would be kept seperate by an internal baffle. It would be a very large box, though- but if you want to put two 8" drivers into this thing, it's already going to be larger than breadbox

I can see why you weren't able to immediately find an example of what I was talking about- I saw your message and looked for an example, and I coudn't find one either! I promise I didn't just pull that one out of thin air- I just don't know where I saw it.

Regardless- they way the general idea goes is that a ML TL will tend to have peaks at intervals related to the tuning frequency. I believe that using two lines would work is- you tune them half an octave apart, and the peaks of one correspond with the nulls of the other. I wish I could have found a website with a better explanation.

At this point I think it's a good idea to seek expert advice; Planet10 is a moderator here, and his website is t-linespeakers.com If anyone has seen this contraption, I'd guess that he has.

I have looked at Martins Worksheet regarding two driver enclosures. That particular worksheet seems to deal with an enclosure other than a MLTL. I will investigate it further. I really dont understand how he comes up with cross-section dimensions though.

He comes up with the cross section dimensions based on the driver's Sd (surface area). Have a look at his Projects page, and I think you'll see what he's done, and his thoughts on the matter.

Anyway. I really dont know, if I NEED two drivers. BUT I really want two drivers. Also I think I can xo the tweeter high enough, that it should blend nicely. I am using a T90A super tweeter with another Fostex Driver (FF165K), and that worked out real nice. I have just heard so many good things about the FE206E.. I just gotta get some!

Well, you don't know if you need two drivers... so let's try to figure that part out.

1) What's the amp? How few watts are we talking about?
2) What application? Are you going to be listening very loud?
3) If you ever use these for home theater, will you get a stronger amp?

One concern I would raise with using two drivers- i have heard that you need to keep the center-to-center distance less than the wavelength at the crossover frequency. I think that's generally just a rule of thumb. That might be more applicable to line arrays; but it makes me cautious about recommending two 8" full range speakers per cabinet; especially in a normally sized listening room.

Bottom line: you're going to have to prove you need two drivers

They're rated to 96 db/w-m- but you'll want to use the baffle step correction circuit to even out the frequency response. That'll take about 3 db from you, call it 6 to be safe (or mean!)

That means if you have a 1 watt, you can hit 90 db. A doubling of power provides +3 db, so 93 db from 2 watts, 96 db from 4w, 99db from 8w, 103db from 16w- you see how it goes. I don't know exactly how loud I listen to music; but I think that 100db is fairly loud, unless you're having a party or doing home theater.

Prove you need two drivers? Well the criteria would be-

1) you absolutely need 6db increase from two drivers
2) amp can handle 4 ohms (correction circuit will raise impedance, but rob SPL... if you like bass, this is necessary)
3) can scoot your chair back at least a good 10-15 feet (should help imaging)
4)don't mind a cabinet that will be about twice the volume of the one for the single 206E.

I will do some more research on the two driver enclosure idea though. Been trying different search criteria here, but no joy so far.

Anyway thanks.. Any more ideas or thoughts always appreciated.

Jeff

You also might try the full range driver forum; there's a some concentrated interest in this kind of thing over there.

Again, good luck!

Joe