[JoshK]

hate pop, but love trip hop.... listen to Prodigy's new one, Girls for example at 85db SPL....that'll give your speaks a work out.

Good choice Prodigy. Is on par with "Firestarter" ?

I think this is the best of the Prodiy's CDs and I have them all.

[Gordy]

Take a close look at that Decware phase plug...  Nothing more than a 3/4" nut drive available at the local hardware

[miklorsmith]

I invented a phase plug using Decware's idea (socket) and Maury James' ping-pong ball tweak.  You do have to cut out the dust screen, but not the cap.

Get a machine screw and drill it into a golf ball.  The flat head of the machine screw will magnetically attach to the pole magnet and voila!  Done deal.  You can remove it too.  I also dabbed some caulk on the inside-face of the golf ball to reduce reflections.  I also caked some blu-tack on the bolt threads to increase its diameter and faced the golf ball label out for the world to see.  

Combine this with damping the driver and you're probably close to the Decware driver.  They do treat the cone with some class of goo and you're welcome to try that too.

The downside to removing dustcap/screen is possible entry of alien elements.  The more you cut away, the more susceptible.  Decware's on-line owner's manual for the HDT speaker brings this front-and-center.  I had this in mind while devising the golf-ball plug.  

For pure sonics, you're probably better off removing the whole dustcap for a bigger inside diameter.

[Luigi]

Hey Miklorsmith/Gordy/SET Man

RE modifying the FE206E

What exactly is a 3/4 inch nut drive? Is this what we know locally as a socket? For undoing bolts?

You guys have got me fizzing re the physical changes to the driver.

Have never attempted such a thing, and frankly it scares and excites, at the same time.

Miklorsmith: Could you please post a close up pic of the golf ball in place and removed, so I can get an idea of how to go about this?

By the by (please excuse gross ignorance here) how do you post a pic on this forum? I will take a digi shot of my (unfinished) penguins and post here.

Funny thing is, apart from riding my Aprilia Falco (not that quickly, it has bad brakes which I just can't seem to sort) golf is the only sport I play (badly). So to have a set of golf balls poking out of the front of my speakers would be almost too much excitement to cope with. One night Callaway, the next Titleist yada yada. Cant image what sort of an abomination they would then be in the eyes of the better half. Heh heh.

She arrived back last night and I think I could detect a mixture of shock and horror when she saw them front and centre in the living room. However, she was too sick with some disgusting lurgy she'd picked up overseas to care. Played some stuff (Talvin Singh) she liked through them and she calmed down a bit. Perhaps when they're carpeted, I mentioned, and she rolled her eyes again.

Anyway, has anyone had much success with introducing smoothing circuits (caps and whatnot) for these drivers, or is modifying them physically the better way to go? Im all for the latter if it doesnt mess with sensitivity.

Luigi

[miklorsmith]

I'm pretty new to this single-driver thing but I read everything I could get my hands on about the Fostex whizzers.  Here are my opinions, based on what I've been able to learn:

Damping the driver is a no-brainer.  It will improve tone and image stability without downside.  I used Dynamat and felt inside the basket legs, Dynamat and caulk outside the basket legs.  I wrapped the magnet in low-pile carpet, attached with hot glue.  These measures are reversible and don't affect the operating function of the driver.

The 98-cent tweak comprises batting between the whizzer and main cone.  It has a mellowing effect on the whizzer and treble response.  Different materials can be used.  I have tried pillow batting, rolled into a fat "caterpillar", thin strips of open-cell foam, and wool yarn.  Material density and the amount applied will tune the degree of damping.  This does address potential harshness in the treble regions, but does not affect the native mid-treble rise, which is inherent.

Dammar (damar) varnish or c37 violin varnish can be applied to the driver paper itself.  It is reported to have a calming effect on the sound, though the amount applied can be touchy and if you get too much on, the driver may be rendered "dead", at which point you're screwed.  I haven't tried this.

Compensation circuits can lower the "baffle step effect" and improve bass response.  These perform their function, and reportedly well, but with a corresponding reduction in sensitivity.  How much loss will depend on the circuit used.  I'm going to start with just a 5-ohm resistor between the positive speaker cable and driver terminal.  Here's a link to a thread I posed to the loonies:

http://www.audioasylum.com/forums/hug/messages/85260.html

Phase plugs are meant to minimize cross-cancellation from one side of the driver to the other, especially the whizzer and underneath the dustcap.  The Decware guys have been playing around with different sockets and (now) large audio tubes.  The steel sockets and tube pins hold the plug in place.  These versions both require removal of the dust cap which keeps out dust and metal shavings that are common with repeated removal of the driver.

Maury James came up with a great idea using a ping pong ball fastened to the driver-frame with scotch tape, just to give it a try.  If you like it, you can rig up a piece of coat hanger with a magnet on each end which would stick to the driver-attachment bolts.  A center piece attached to the hanger would allow the ball to be placed near the dust cap.

These ideas started the golf ball rolling, as they say.  I don't have any pictures, but I'll take some and come back here with them.  The installation is clean and the golf balls are definitely conversation-starters.  

With the golf ball, I find the 98-cent tweak tames the treble too much.  The plug also tends to reduce "beaming" somewhat, though there is still significant directionality.

There is another Maury James tweak that involves connecting either the positive or negative terminal of the driver to the center hole between them.  It is reportedly amp-specific which one works.  I have it rigged up with a 3-position switch mounted outside the speaker, with positive and negative "on" positions, and a third "off" position.  I've only tried the speakers with digital amps and have yet to hear benefit to this one.

These tweaks play well together.  I would start with softening the enclosure and basket.  The non-invasive ping-pong ball tweak is another great one, since it is entirely reversible.  Go from there.  I'm opposed to the circuit idea since I started this project for efficiency reasons, but if my amp will still drive the speaker and the sound is better, win, win!  You can always take it out too.

That's what I know.

[Luigi]

Miklorsmith

Thanks very much for your comments and suggestions on modifying the FE206Es. I had a bit of a gander at the whizzers up close and now recognise what the dustcap and screen are all about. In behind looks to be a ring of some kind and some foam.

What I really would appreciate is a digital shot or two of before, during and after the mod, so as I know what Im doing. Not that keen on trying with sockets (or nut drives!) as it seems too easy to jigger the cone altogether.

Anyway, took a few digi shots of my new (and unfinished) speakers so will now try to post one. See gallery, page 37, for shot of a penguin.

Luigi

[miklorsmith]

They be's in page 37 of the Gallery.  The resistor is doing great things, though it's an 8-ohm (all they had that was close at RadioShark).  I'll be ordering 4-ohm and 5-ohm selections to zero-in.

[SET Man]

Hi Luigi,
   I saw your Penguins Nice looking bird. Man!... where do find PVC pipe that big

Don't be afraid of modding the Fostex. Cutting out the dust cap is not that difficult. Fostex voice coil is quite robust.... still you should be careful

I see that your T-line seem to be shorter than the Fs of the 206. Maybe that is not a bad thing. There have been talk about making line shorter than the Fs of the driver or make them longer.

I made my TQWT longer than the Fs and they work well near the corner... but I do have some dip in the upper bass 120-200hz  But I do gain some lower bass with them near the corner. I made my Pipe dream a bit shorter than the Fs and they seem to have full upper bass but they do sound a bit boomy. Than there is a question of where should the mounth be... front, side, back, bottom or even top!. I guess there is alway a trade off..

If I have to do is again I think I would go a bit shorter than what I have now.

Anyway, that is another subjuct that need to be discuss on another post. Well, enjoy your Penguins. Keep us posted on the mod.

Buddy

[Panelhead]

I use art supply damar varnish on all my Lowther cones. It works wonders.
  I used it on a pair of old style 208 Sigma's a couple years back. This was late 90's, the drivers were purchased from Japan. The paper used then was soft and thick, looked like paper bag paper. It really soaked up the stuff. But the sonics were no better, maybe a little worse afterwards.
  Suspect the newer banana paper is closer to th Lowther cone paper. The varnish soaks in slowly with A series Lowther cones. It takes several minutes to absorb a light coating.
  But a word of caution. The varnish is permanent and may not work with the banana paper any better than the old style.
  To my ears, a single light coating does wonders for Lowthers. Many people have heard my speakers in many versions over the years and never heard the Lowther shout. Many were Lowther owners, who had honk with theirs.
 The rising impedance due to the high inductance is the major cause of honk. Transformer coupled tube amps have trouble with this rising impedance, the reflected impedance strangles the output tubes. Using a resistor across the speaker terminals can really help in flattening the impedance.
  Back wave reflection re-radiating through the cone is another. This why I have gone to TQWT with dampening material on the cabinet directly behind the driver.
  The whizzer resonating is only a part of this problem. This is the only issue addressed by cone modifications.

                           George

[SET Man]

Hi Panelhead,

Yes! the Dammar works for me too. I have the newer Fostex FE176E. The banana cone thingy Took weeks for them to dry. But I like the way thier sound now. I think this helped somewhat to control the cone resonant/break up mode. I coated both front and back lightly.

I see that you have TQWT. I think is the best way to go with Fostex. Just wondering... Where do you position the mounth? And is the line set at Fs or shorter or longer? Do you have picture of your TQWT?

Buddy

[Panelhead]

Hi Panelhead,


I see that you have TQWT. I think is the best way to go with Fostex. Just wondering... Where do you position the mounth? And is the line set at Fs or shorter or longer? Do you have picture of your TQWT?

Buddy

  My last three pair have been folded TQWT with the mouth rear firing. The last two had the tuning set real close to the driver resonance. One before had the box tuning about 15 Hz. higher.
  I do not know how to post pics of my latest speakers on this forum. Some pics of of an older pair were on Bert's website a few years back. They were abount the same, internal differences.
  I derived my own formula to calculate tuning for the TQWT, or any other linear taper tube.

    Tuning Frequency =  4733.3/Lenght of horn in inches

  This has worked for every one built and measured. If you plug in the one shown on the Lowther Club of Norway plans you get about 80 Hz, which is about what most seem to get in real life.
  My current ones are 5' tall, 12" wide, 17" deep. The wood is two sheets of 12 mm, 9 ply baltic birch gorilla glued together. The fronts have a 1" radius routered in, the drivers countersunk a 1/4' and all is wrapped in cherry veneer. They weight 120 lbs each.
  The countersinking was easy, glued a cutout front of 1/4" luan to smooth this. Internally, the top corners have three sections installed to smooth the bend. This helps maintain the taper through the 180 degree bend. The angles are 22 1/2 degree. The bottom has a deflector also.
  The results are well worth the effort. But from building several of these, the cabinets are very forgiving. Losing the taper through the top does not hurt the response much. Driver mounting is also not critical, 35% from the top seems to work well. Stay away from 50%.

                        George

[Luigi]

Hi Guys

I just wrote a message, and lost the damned thing, so now have to repeat it all.

So to go short: I am intending not to wait a year for the drivers to run in, and instead will modify the driver non-invasively. As the quacks say, "above all, do no harm". Not that that ever stops them!

So will try this trick here:

http://home.hetnet.nl/~geenius/Solo206.html

One can only surmise this guy had a bright idea which involved having a bright idea. (see bottom of the Solo206 web page)

So I will have a shot with the grounding leads, and will also try the trick with the scotch tape and ping pong ball. But not with the wire - I know how much I can and can't get away with. And really, must speakers wear glasses? I think that the idea of hanging a tube in there and letting the socket pins be held in place by the magnet is ironic and perfect. Puts a whole new twist on tube rolling

If I get really adventurous, and the ping pong ball pays off, perhaps I might go down the Miklorsmith route with the golf ball. Tell me MS, I saw your pics on p37 of the gallery - did you simply remove the dustcap screen to do this mod? Or have you gone inside and performed a little keyhole surgery?

And how exactly is the resistor attached to the FE206E, and have you tried other types of resistors? What effect does this have?

Luigi

[miklorsmith]

Resistor is soldered between positive terminal lead and speaker wire.  I hot-glued the resistor body to the magnet (Dynamat, actually).  The one pictured is an 8-ohm, non-inductive unit.  It fills out the sound nicely and is a BIG improvement.  The AA guy who brought it up said he uses 5 ohms and I've seen another comment that 4 ohms works great.  I've ordered both from Parts Express and will try them both.  I think they'll be even better.  Even the 8-ohm creates no problems whatsoever for my 6-watt amp.  There are more complicated circuits that can do this job, but I think this will be sufficient while keeping things simple.  It tames the agressive mid/high response and brings the bass forward a bit.  Good stuff.  Generally, I would think the smallest value that works for you would be optimal.

On the golf ball, the screen was removed and that's it.  The surface of the pole magnet is ready to roll.  I had to flatten and shape the screw head a bit to fit smoothly through the hole.  If you remove the screen, make sure you get all the little "hairs" out.  I used tweezers, as the utility knife I used for the primary operation is too big and mean.  The pole magnet holds the whole operation like a champ, but not so much that it tears the ball out of your hand or prevents removal.

If you do this, it is not non-invasive.  Once the operation is complete and you're working on the speakers afterward, it's not a bad idea to cover the hole with a piece of masking tape.  Works great and ensures nothing creeps in.  

[Luigi]

Thanks for the update Miklorsmith.

Have you tried the earthing trick mentioned in the Solo206 article?

I believe some have said that removal of the dustcap entirely really liberates the treble. So what exactly does the golf ball mod do? Is this to improve the dispersion or merely to tame the lower treble response?

Regarding the resistor, this would appear to be a good place to start, as most of the other "correction circuits" seem to involve a resistor, coil and cap, IIRC, which would appear to strangle the driver, and reduce its sensitivity. And make it more like any other "two way".

Is there any downside to introducing the resistor? I have a whopping 35wpc to play with, so am not at all worried about the ability of the amp-speaker combo to produce enough SPLs.

Again, thanks for your suggestions. I can see you have already done an awful lot of the spadework for me, and I appreciate it.

Luigi

[miklorsmith]

I'm not an expert.  What I have gathered indicates the phase plug primarily reduces cross-cancellation from one side of the driver to the other.  Looking at the whizzer, it is easy to imagine how this could be a problem.  Maury James thinks cancellation would also be beneficial underneath the dust cap, as there are opposing, moving walls there as well.  He didn't want to wreck his drivers and hadn't tried it though

I would guess that sonically, the bigger the diameter of the plug the better.  Thus, I assume my solution is sonically inferior to the "socket" or vacuum tube idea.  Increasing diameter is the reason for the blu-tack covering the bolt-threads in the picture.  These speakers are designed for garage use and transport, thus I wanted to keep the incursion-hole as small as possible.

It seems there is some dispersion benefit, but I would call it secondary.  The ping pong ball test will certainly show you whether you think it's worth a more permanent solution.  Man, that light bulb contraption is Ugly.  Attack of the giant spiders. . .

As an aside, I read that somebody stacked two big sockets on top of each other.  He said it was the best plug he'd heard, but that his wife couldn't stand it.  

On the grounding question - you can see the red, green, and black wires soldered to the terminals and basket in the "mods" picture.  They are soldered into the switch shown in the "rearjunk" picture.  The switch is a three-position affair, with one position "On" to the positive terminal, one position "On" to the negative terminal, and a null "Off" position.

The negative ground tweak has been amended to the switch idea, because depending on the amplifier, one or the other may work.  Maury James also came up with this one.  Many people say this one's fantastic, cheap, and easy though I have yet to notice a difference.  Maybe my digital amplifier doesn't allow this one to work.

There are no downsides to either of these.  They're both reversible and cheap, so the worst case is that you don't hear them or take them out.

You're entirely welcome for doing legwork.  I just sold my Gallo Ref. 3's because after hearing these speakers I literally couldn't stand them anymore (though I loved them previously).  The fact that this level of fidelity is available at such absurd prices in incredible.  Small amps, efficient speakers - the revolution is brewing. . .

[Lensman]

Luigi,

Soldering a resistor across the speaker (or amp output) terminals can potentially subject your amp to a very low impedance load. With a 5 Ohm resistor alone, you could be looking at less than a 3 Ohm load as seen by your amp. Especially with a tube amp, a better solution for taming rising impedance (and the over-emphasized  high frequencies) with your Fostex is to use a capacitor AND a resistor together (Zobel Network).  A resistor alone can drive impedance down, but cannot flatten out the impedance curve the way a Zobel can.  I have the Fostex FE-167E drivers and I use  a 6.8uF capacitor with a 9 Ohm resistor.  Capacitor and resistor wired in series, then the combo parallelled across the speaker or amp output terminals.  The higher the resistor value, the brighter the sound.  The capacitor-plus-resistor approach swings the rising impedance curve down more effectively and more safely than a resistor alone.

Lensman