[jonners]

   I've searched for threads on this topic, and have generally found that people have tried bringing in e.g. a rear-firing Fostex tweeter from about 8kHz up. However, the rear output from the Visaton B200 starts falling off above 2kHz, so it seems to me that in order to extend its dipole behaviour it would seem desirable for the rear tweet to start augmenting from 2kHz. What do you think - is this a sound idea?
   I'd like to hear if anyone has tried this, and what suitable tweeters people know of. Maybe the Beyma T2030 would be a possible candidate: 95dB, 2-20kHz?
   At the moment I'm experimenting with the only tweeters I have to hand, a pair of Celestion HF1300s from the Jurassic Age I don't know what their sensitivity is, but it's less than the B200. Nevertheless, their addition is definitely beneficial: Instruments and voices sound more three-dimensional and spacious, and instruments that put out a lot of treble energy seem to have moved further back. For example, on a CD of oboe, cello and harpsichord the addition of the tweeter apparently moves the harpsichord from somewhat forward of the oboe to just behind it, back where it should be! The measured increase in treble level at the listening position using 1-20kHz pink noise is only around 0.5dB.
   Finally, my thanks to the many who have posted here. I've read hundreds of posts, and as a result am greatly enjoying my OBs.
   

[dewar]

Hi,

I'm using B&G Neo3 ribbon tweeters on the rear of my B200 baffle. They are firing up at 45 degrees with a single 2uf cap on them. I dont remember what this crosses them over at but it must be near 20K.

Adds quite a bit of 'air' and life to the sound and I really like them. Doesnt really show up on measurements though.

My B200 measure a rise from 1-10k so I'm not sure about the 2k roll off you mention. I think the Visaton website shows them flat to at least 10k. I also used to have a bsc circuit on them to tame this rise but now use DEQ.

If you were going to bring in a tweeter at 2k it might be worth trying it on the front with a crossover, but then that defeats half the attraction of the B200.

cheers

B.

[jonners]

  Hi.
 When I mentioned a roll-off above 2kHz I was referring to the output from the rear of the B200, not the front. As I understand it (mostly from reading Siegfried Linkwitz discussing his Orion++), a perfect dipole would have identical front and rear output, so you could in theory turn the speaker back to front and it would sound just the same. Hence I am proposing to augment just the rear output from 2kHz up.
If the speaker sounds too bright after balancing front and rear output in that way, I would then dial in some more equalisation using - in my case - a DEQ2496.
       John

[scorpion]

The Celestion HF 1300 is one of the best midrange-tweeters ever made, it deserves better than to be played backward. I find your approach interesting but where do you have your information of the B200's rear output ?

About the B200's response, this is the official Visaton frequencyresponse: http://www.visaton.de/bilder/frequenz/gross/b200_6_fs.gif

/Erling

[jonners]

The Celestion HF 1300 is one of the best midrange-tweeters ever made, it deserves better than to be played backward. I find your approach interesting but where do you have your information of the B200's rear output ?


/Erling

   I didn't realise the HF1300 was held in such high regard, I may try it using forwards with the B200s. Hope it hasn't gone into a sulk from my mistreatment!
   My information on the rear output comes from my own (rough) measurements using an ECM8000 mike with the Behringer RTA, and a sound-level meter. The HF output from the rear of the B200 is of course attenuated because, for a start, the magnet and basket are in the way.
        John

[jonners]

    Well, I tried mounting the HF1300 on the front of the baffle but it's no good at all like that. The sound goes flat and dull, probably because the frequency overlap between the B200 and the HF1300 leads to a lot of cancellations. Returning it to the back of the baffle (in opposite electrical phase to the B200) and suddenly there's real music, real instruments again.
    S. Linkwitz splashes out on an expensive Seas Millenium tweeter for rear-facing duties. He's obviously sure he's onto something special. http://www.linkwitzlab.com/orion++.htm
           John

[scorpion]

I just wanted to point out that the Hf1300 is one of those Vintage drivers that is highly praised. Of course you can use it on the Back and as you say Linkwitz uses a very good tweeter on the back. The Orion++ webpages are quite informative.

I measured my 'Volks-OB' from behind and there is a treshold between 5 and 6 kHz when the backward response falls about 8 dBs and then stays at that level.

/Erling

[jonners]

Hi,

I'm using B&G Neo3 ribbon tweeters on the rear of my B200 baffle. They are firing up at 45 degrees with a single 2uf cap on them. I dont remember what this crosses them over at but it must be near 20K.

Do you know of a European source for these? (I live in the U.K.)
I think it would be interesting to try bringing them in at a lower frequency (with the B200s running full-range) and then using the DEQ if necessary to reduce overall treble levels. That's my plan anyway, and I'll post the results.
      John

[JANDG]

I have done this w/ B200's & rear fire tweeters in ribbon form w/ many differant types, also domes, etc....allways seems good to great if OXed high..Front fire = NO WAY for me....