[Luigi]

This is a bit of an aside to the Phase plugs from Planet 10 discussion, but somewhat relevant.

Can anyone give some advice regarding the addition of a tweeter to the B200?

I have, like many here it would seem, the Visatons in OB design, and have some Fostex FH17H tweets lying around from an old Adire project.

Thought I might try these out with the B200s but have no idea how to cross the tweeters over or with what in terms of a simple crossover. I guess ideally they would need to cross over above about 8K or 10K?

What I need to know is cap value, and any cap recommendations.

An alternative might be to do the Planet 10 cut and tuck phase plug job. But seeing as I have a pair of the Fostex tweets on hand and they are also similar sensitivity, it would be kind of fun trying them out. I'm running the B200s as they come, no correction networks.

Another aside. I received some CSS FR125s a couple of days ago. Man these are cool wee full range drivers; gutsy, clean, sweet top end. I have them running in open baffle and they definitely have more upward extension than the B200s. They even do a good semblance of upper bass. The significant other thinks they're great cos they're almost invisible.

My open baffle is a 4in piece of dunny pipe, a foot long (cleaned before use!). Drivers are kept in place with blu-tac at present. I intend using these as my multimedia speakers, instead of the imac drive units. Amp is Trends T10.1 modded by MM. It drives the FR125s no sweat.

Cheers

Luigi

[dewar]

I've got some Neo3 tweeters on their way from GR Research to be rear mounted pointing up at 45 degree. The idea was a roughly 10k highpass. Danny Ritchie emailed me this:

I'd start with the 1uF value and then try the 2uF value, then you can add the 1uF value to the 2uF value to get a 3uF value. The 3uF value will let it play lower in range and you may or may not like it as well as the 2uF or 1uF values.
 
I asked him if he knew the roll off points these caps and he said he'd get back to me. I'll update.

I'm guessing that as they will be rear mounted and not effecting FR that there crossover point is not too critical. Front mounting at 10k proved to be a bad idea as you may have gathered from other treads - phase cancellation being seemingly impossible to mitigate.

cheers,

b.

[Luigi]

Bevan

Thanks for the info. I was planning on doing the same; ie, mounting the Fostex in behind; didn't want to ruin the frontal appearance, but also just wanted a bit more air at the top end.

Am planning on doing the phase plug thing to the Visatons; did the same with the Fostex 206Es and it seemed worthwhile.

Will order some 1uF and 2uF caps for the crossover. Any idea what power rating these have to be?

Cheers for the info.

Luigi

[FlorianO]

Front mounting at 10k proved to be a bad idea as you may have gathered from other treads - phase cancellation being seemingly impossible to mitigate.

would you care to detail that  ? wasn't aware that there are issues about front vs back mounting of (super)tweeters.

phase cancellation above 10k ?! At that freq the wavelength is 3.44 cm, any (reasonable) baffle would have a path length of several wavelengths, and drivers get unidirectional

So where does that come from ? Or is it just hearsay ?

Pointers appreciated. TIA

Florian

[dewar]

Hi Florian.

If you go back one page in the OB forums you'll see a thread about adding tweeters to the B200. In it I put this link

http://www.audiocircle.com/index.php?topic=31585.0

The graphs show the problem quite well. But what I'm wondering is, how come the Zu Druids and Bastanis Prometheus speakers seem to get around the problem?

cheers

Bevan

[JimJ]

If the tweets don't work out well for you, I think I might be able to put them to use in my FE168EZ project

[FlorianO]

If you go back one page in the OB forums you'll see a thread about adding tweeters to the B200. In it I put this link

http://www.audiocircle.com/index.php?topic=31585.0

The graphs show the problem quite well. But what I'm wondering is, how come the Zu Druids and Bastanis Prometheus speakers seem to get around the problem?

... and all others using a wide ranger with tweeter on top. The graphs do look telling but I have some questions  -- e.g. a 5 dB (!) suckout at around 3 kHz (and down!). There's quite a "remarcable" tweeter causing that kind of  cancellation at 3, almost 4, octaves down from the XO point...

I still have to dig a bit deeper into this issue, but smth is fishy.... Anyway, thanks for the link.

Come to think of it: If using a first order high-pass, why don't you simply revert the polarity of your tweeter and fire it backwards ?

Florian

P.S. Maybe the issue is as simple as alinging the ACs of the tweet and wide-ranger ?

[Luigi]

Well, I've done it.

Got some 2.2uF caps, and put the FT17Hs on the backs of the OBs (B200s on front). They therefore crossover at around about 9500Hz. Haven't had time for much of a listen as yet but there is definitely more treble energy there. And whether I'm kidding myself or not, imaging seems more precise, more corporeal. More on this over the next few days.

One thing, I should probably have a decent listen to them, and then check them out with polarity reversed, as FlorianO suggested. In terms of treble energy, there could even be too much now, so might get a pair of 1uF caps as well, just to check. They cost sod all so no harm trying.

[Luigi]

Well, no going back to B200s on their own again. Adding the rear firing tweeter was a positive move, and now I'm trying to optimise this by playing around with different tweeters. Have some Neo3 and GRT6's ordered, along with some decent Sonicaps and wire. Hopefully, the tweets should be about right in terms of matching sensitivity to the Visatons.
None of these is particularly expensive either. The FT17Hs aren't terribly special, to my ears. FWIW, the best treble I have ever heard was from speakers with Manger drivers but these were muy expensivo. And anyway they aren't OB compatible to the best of my knowledge. But they sounded soooo smooth and detailed.

Anyhoo, more on adding top end drivers to B200s when they arrive.

[Luigi]

Okay, a bit of an update, for any of you interested. I tried a couple of other tweeters, but none was sufficiently sensitive to mate simply with the Visatons. The 98db Fostex seem to do the trick well with simple first order crossover. Cap.

Just for the hell of it, I disconnected the Fostex tweeters to have a listen, because I have been troubled by a kind of phasey-ness to the presentation.

Well, it is simply astonishing how you get used to having highs that werent there before. I said before there is no going back. Absolutely convinced of this now.

But the interesting thing was, with the tweets disconnected the phasey-ness had gone. So I knew was onto something here. The tweeter(s) was (are) mounted to the back of the baffle with a single wood screw. They were kind of hard mounted there, unmoving. So I simply removed the screw and remounted them so they can kind of swing in free air.

Hooked them back up and the highs returned, naturally, but the phasey-ness had disappeared, utterly. Now Im wondering how much better things can get if I somehow mount the Visatons "in free air" as well to the baffle! Just dont quite know how to do this. Guess I can start by using some sort of rubber gasket. Currently, they are simply screwed to the front of the baffle. So vibes go straight into the baffle and no doubt ring like hell.

Strike me these are sounding good now. Visited a guy yesterday with a $50K system. This had twin subs, so we got rid of those to get a handle on the sound of the mains. Much better, much more integrated. He runs top of the range Ambience ribbons with dual 6.5inch ScanSpeak woofers, and amazing 845 amps. Supposedly State of the Art transport (MBL) and Audionote 3 DAC. Nice big presentation but so NOT lifelike. Rather too laid back for my liking too. And as soon as you hear music via cabinets you can hear them ringing and adding extraneous boxy bits.

So Im feeling pretty good about my modest system at present.

Did the Planet 10 mod to the Visatons too; well worthwhile. Opened them up a bit more, literally and sonically. Did a rough-as job on getting rid of all the glue but was keen not to knife the cones.

Might just sit back and enjoy for a while (yeah right). Buy a few new discs maybe.