I'd like to try a coaxial configuration with the 8" Visaton bg20 fullrange and 2" tw6 tweeter in an open baffle for listening near field.
Would a simple 1st order crossover on the tweeter work in this case? Attached are the frequency response of both drivers.
The bg20 seems to have good output to 10 kHz, so I was thinking to cross that tw6 could be crossed at that frequency or a bit lower?
I know there are more complex crossover for these two drivers when used in a bass reflex enclosure, but I was wondering if I can get away with the simplest crossover.
I mention open baffle because I've listened to those in the past and I enjoyed the sound openness.
Would a simple 1st order crossover on the tweeter work in this case? Attached are the frequency response of both drivers.
The bg20 seems to have good output to 10 kHz, so I was thinking to cross that tw6 could be crossed at that frequency or a bit lower?
I know there are more complex crossover for these two drivers when used in a bass reflex enclosure, but I was wondering if I can get away with the simplest crossover.
I mention open baffle because I've listened to those in the past and I enjoyed the sound openness.
Attachments
Any opinion on this?
I'm just wondering if the sensitivity/impedance curves of the tweeter match the ones for the fullrange? or should be tweeter be more sensitive?
Also the first order crossover means 6 db/octave at the crossover frequency. Anywhere in the 7 to 10 khz range should be fine?
I appreciate any comments.
I'm just wondering if the sensitivity/impedance curves of the tweeter match the ones for the fullrange? or should be tweeter be more sensitive?
Also the first order crossover means 6 db/octave at the crossover frequency. Anywhere in the 7 to 10 khz range should be fine?
I appreciate any comments.
just try it, a single cap or two is cheap. FWIW, the 'extended highs' of the BG20 look like cone breakup to me, so I'd crossover lower & with a more complex xover, but that's just me....
I would cross the tweeter over two octaves above its fundamantal resonance, i.e. around 6000Hz, using a 3.3uF capacitor.
There may be no problem with the sensitivity, but there's only one way to find out!
There may be no problem with the sensitivity, but there's only one way to find out!
What will you do with the peak near 1400Hz? With a first order rolloff that region will continue to rise. You might be able to get creative with a second order filter, however your better option would be to work with the impedance near the resonance.
That means an RLC series bandpass placed across the driver, in addition to your first order and resistor.
That means an RLC series bandpass placed across the driver, in addition to your first order and resistor.
if it's a coaxial arrangement your going for i would think that the mount and resulting distance between the two is going to affect or perhaps dictate what you do for a crossover,no?
and why use a BG 20 for a coax? it's got a whizzer cone that will be obviated by the tweeter,no?
and why use a BG 20 for a coax? it's got a whizzer cone that will be obviated by the tweeter,no?
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its worth a try as coax - - go in 0.5uF increments. - 1- 1.5uF is often enough for a helper tweeter. BG20 needs help on the top. CT230 deletes the whizzer (making it more like B200 response-wise).
crossover for CT230
http://www.audiofil.hr/data/upload/20081225_221436_ct230lq.jpg
crossover for CT230
http://www.audiofil.hr/data/upload/20081225_221436_ct230lq.jpg
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Thanks everyone for their comments/suggestions.
I don't have any experience with crossovers, so it will be a learning curve for me.
The coaxial arrangement on ct273 is very similar to what I plan to do, but have the tweeter centred.
I'm hoping that I can avoid complex crossovers and just accept the bumpy response of bg20 above 1200 hz.
Do you think it's necessary to remove the whizzer cone on bg20? or it can be left in place and have the tweeter help above 6000 hz?
I'm also thinking if it's ok to let bg20 run fullrange (similar to what was done in vintage coaxial speakers)? or perhaps use the appropriate inductor at the crossover frequency?
I don't have any experience with crossovers, so it will be a learning curve for me.
The coaxial arrangement on ct273 is very similar to what I plan to do, but have the tweeter centred.
I'm hoping that I can avoid complex crossovers and just accept the bumpy response of bg20 above 1200 hz.
Do you think it's necessary to remove the whizzer cone on bg20? or it can be left in place and have the tweeter help above 6000 hz?
I'm also thinking if it's ok to let bg20 run fullrange (similar to what was done in vintage coaxial speakers)? or perhaps use the appropriate inductor at the crossover frequency?
Hmm, that's a shot in the dark but I'd have to say that full range drivers are made to breakup gracefully. If you start changing the mass and the strength of parts of the cone you won't know what to expect.
Ideally you would measure before and after and have a spare driver to maybe destroy in the process.
Hmm, thought I responded last night; regardless, inexpensive vintage coax were often just 2.2 uF pio caps [~9-11 kHz depending on impedance, so in theory will be a good place to start with the BG20 based on its factory response] with tweeter upgrades normally being just an Lpad, though of course the [pre]amp had bass/treble tone controls and listened off axis to 'taste'.
GM
I assume so IME.
Yes, run 'full range'.
No! Not if you want to preserve its vintage presentation/mids 'presence'; better to do the Lowther $0.98 tweak: Modifications
You also may want to experiment with little rubber cement 'dots' [or more as required] on the dust cap [DC] to deal with any spurious HF 'ringing'.
GM
another vote for the 98 cent tweak, removing the whizzer cone will affect the low end resonant frequency and efficiency
I only linked CT230's crossover as a reference to that system.
Start with a 1uF cap (could be a smaller value with a stronger tweeter or higher Z peak) for TW6NG to augment the top which rolls on-axis, right above 10KHz.
If 1uF isn't enough, go 1.5uF - 2uF. Some finicky folks move in 0.22uF steps.
BetsyK has a similar response but IIRC some peak at ~10K which gives it a bit more definition.
BG20 is a nice driver. I hope SB Acoustic's fullrange 8 hits the states.
Start with a 1uF cap (could be a smaller value with a stronger tweeter or higher Z peak) for TW6NG to augment the top which rolls on-axis, right above 10KHz.
If 1uF isn't enough, go 1.5uF - 2uF. Some finicky folks move in 0.22uF steps.
BetsyK has a similar response but IIRC some peak at ~10K which gives it a bit more definition.
BG20 is a nice driver. I hope SB Acoustic's fullrange 8 hits the states.
I said 3.3uF earlier, but on second thoughts, 2.2uF or smaller would be more appropriate.
2.2uF will roll off the treble gradually below 9,000Hz when used with your 8 ohm tweeter in accord with GM's suggestion above.
Capacitor values 1.5uF and 1uF may also be tried for increasingly higher frequency roll offs, and this is in accord with freddi's suggestion above.
All three of the above values are normally associated with super tweeters. Buy all three and find which one sounds best in your application.
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