Well I finally sprung for some premium drivers after tinkering for 18 years and picked up some lightly used Visaton B200's. These drivers are pretty good, the upper extension is really amazing considering the cone size but there is no getting around that 6db drop in efficiency from ~ 600hz down. I know some guys are running these without addressing the problem but I noticed it as soon as I fired them up, I even though there was something wrong with my recently modded CD player. I have them mounted in OB's much like the Omega's and was thinking about adding a second 8" driver set up to drop off at 6db per octave as the B200 begins to pick up steam at 6db per octave around 6oohz. Has anybody tried this yet? It seems a .5 helper woofer rated for about 93db of efficiency should do the trick. I am currently using a sub to take over from about 100hz down.
Hi,
you could use either the recommended filter for this drop or maybe add 2 visaton BG20.
http://www.visaton.de/bilder/weichen/gross/solo20_w.gif
(Will still require a Sub)
-Micha
you could use either the recommended filter for this drop or maybe add 2 visaton BG20.
http://www.visaton.de/bilder/weichen/gross/solo20_w.gif
(Will still require a Sub)
-Micha
I'm trying to stay away from filters even the line level ones. I hate the idea of throwing the B200's great efficiency away. The BG20 isn't a bad idea,I was thinking of finding an 8" driver with similar characteristics (except the price!) to the B200 as a helper. Also a second woofer would help limit the excursion the B200 sees. I think the hardest part is going t be rolling the .5 driver off smoothly with minimum phase shift then killing its output once it gets to about 1200 hz.
Oh, well i thought about it again..
first: Without filter the B200 is not listenable to me (Had him in 3 enclosures, including open baffle)
second: if you still dont want any filters, you could use one Bg20 reverse on baffle so the filtering is mechanical by magnet etc, if looks arent that important. Benefit will be some more highs at the back of the baffle. Even then you gain just 3dB where you want more, since the difference from 600 to 10.000Hz is about more than 10db (!)
third: Just listen more off axis, the response will probably even out (to some extent) on 15 degrees or more.
-Micha
first: Without filter the B200 is not listenable to me (Had him in 3 enclosures, including open baffle)
second: if you still dont want any filters, you could use one Bg20 reverse on baffle so the filtering is mechanical by magnet etc, if looks arent that important. Benefit will be some more highs at the back of the baffle. Even then you gain just 3dB where you want more, since the difference from 600 to 10.000Hz is about more than 10db (!)
third: Just listen more off axis, the response will probably even out (to some extent) on 15 degrees or more.
-Micha
Piek said:
Wont work like that
Only significant difference will be lots of diffractions
If this Bg20 is that good, you could use a pair in paralel
Filter you need anyway
Though you could experiment with such pair of Bg20, mounted in a "ripole-like" arrangement...heavily stuffed = acoustic filter
Back of Bg20 could be either "boxed" or "ripole-style"
Attachments
but just a small inductor will do, I guess 
Piek said:
Omce i got phase pugs in B200 i had no real issues with them (1.2 x 1.1 m OB, pic attached currently sans B200). Before that they were either hot (on axis) or you were wondering what tweeter (off axis).
The efficiency of these is not as high as the number would indicate.
dave
PS: when we had these on a 16' wide baffle (ie plywood used to fill in between and to extend the baffles attached), bass was quite extended. With a Q of 0.7 it is a case of the bigger the baffle the better.
Tea-Bag said:
oops...
16' wide baffles? Do you listen in a air craft hanger?
This happened at one of the annual VI diyFESTs... the OB "room" is outside on the apron of the "double garage" with listeners sitting out in the driveway. There may be pictures buried in one of the diyFEST threads.
dave
Attachments
Looks like fun
But doesnt look like 16 feet to me...one ´(dot) is feet, and two ´´(dots) is inches, as far as I know
Man, why cant you guys just use "mm, cm, M, km", like the rest of us...miles ? thats either jazz or surfing on water
In the old days a shipbuilder should handle "danish feet", "norwegian feet", "english feet" and "american feet"...all different from each other
But doesnt look like 16 feet to me...one ´(dot) is feet, and two ´´(dots) is inches, as far as I know
Man, why cant you guys just use "mm, cm, M, km", like the rest of us...miles ? thats either jazz or surfing on water
In the old days a shipbuilder should handle "danish feet", "norwegian feet", "english feet" and "american feet"...all different from each other
Cal Weldon said:
Thanx Cal... that is the baffle picture. those drivers are the rare Korean Sound of Music alnico 6.5", but we did have another couple drivers in the same baffles at varous points (note the hi-tech green masking tape, driver sub-baffle fixing method).
You'll also see where Steve Deckert got the idea of using a tube as a phase plug (i have proper wooden ones now)
dave
I already have Dave's phase plugs, though I can not comment on the "before" sound I find the current sound quality to be quite good for a full range driver. I actually have no real qualms with these drivers...except the striking lack of lower midrange. I know there is more than just 6db separating the lowest and highest output of the B200 FR but I'm just going to focus on the lower midrange since that is what bothers me the most. I have a huge 15" woofer I used in another OB project but I never felt the integration was very good going from a light weight 8" driver to a massive 15" woofer. I have these Visatons mounted in a 13"x45" baffle with 14" wings. I find the low end to be completely lacking though. I still have an 8" Silver Flute mounted in an OB so Maybe I'll do some experiments with it along side the B200's.
planet10 said:
Hi Dave,
while I respect your listening impressions and effort, I expect slight changes with a small Phaseplug at about two octaves from my experience with other drivers, did the plug affect the "problems" earlier (say 1KHz and up) too, any measurements available? Visaton engineers said they experiemented with and without dustcap and said you better not touch it.
-Micha
Piek said:
In my room and on my baffles i didn't have issue with the rising response shown in the graphs and that a some claim (with or without plugs). The top was laserlike thou. Too hot on the top on axis (could be interperated as not enuff bass), and fell off very rapidly as you moved off axis. The phase plugs made a very significant difference in the top end, dramatically increasing the sweet spot... changing the top end from laser like to fairly wide dispersion will flatten the on-axis response.
BTW measured efficiency of the B200s i had (n=8) was 91.5 dB 1w/1m. This is totally consistent with thepower we needed to get them to the levels we used (before efficiency was confirmed by measure)
The Visaton engineers can bring a set by anytime and i'll demonstrate.
dave
maybe this link should have been mentioned and/or acknowledged earlier
http://www.iol.ie/~waltonaudio/ob.html
Ed
http://www.iol.ie/~waltonaudio/ob.html
Ed
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