[JohnCZ]

Erling/Lin,
I finally believe I've got my B200/Alpha15 sounding good - However! I still need a little help or advise. I've tried a number of configurations to tame the B200 and control the Alpha and have settled on the 10 ohm resistor/.8 inductor/6.8 cap on the B200 on the +input of the driver.

For the Alpha I am using the T-Bass circuit designed by Graham Maynard here:
http://www.diyaudio.com/forums/full-range/130679-t-bass-drive-ob-lf-drivers.html
This circuit made the bass sound faster and more controlled and in step with the B200.

Here is my observation and question:
On louder passages of music with more bass I notice the B200 working hard - a lot of movement in the cone.  Also, I can hear midrange through the Alpha - not much, but some.

I am considering removing the T-bass and replacing it with an amp from Parts Express that has a low pass filter.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-812

At the moment I am driving the speaker with a 20w receiver but plan to find a 8-10 watt tube amp to replace it.

[-Richard-]

It is no secret that I am technically underdeveloped... however I really do not like the idea of overly "controlling" drivers to remove frequency anomalies... preferring to either live with them or find simple solutions.

For example I also found the Alpha's sounding a bit slow compared to the B200's... I was intrigued by an article on 6moons that mentioned a cheapy outdoor electrical cord called Yard Master, Jeff Day said they sounded very "fast"... I bought it and used it to hook up the Alpha's and that did the trick: http://www.6moons.com/audioreviews/whitelightning/moonshine.html

Dr. Dan Mason (the fire carrier who started this particular fire on this chat room) hated all of that fussy controlling caps, resistors and l-pads and pointed out that they rob the drivers of that ineffable uncanny sound-space dimension that they are capable of when left alone (well at least with the minimum of stuff... I can see using a simple copper coil to cut off the higher frequencies on the Alpha's, which I use).

As our ears get smarter... more sensitive to what we think we hear... they also get more demanding... and more critical... and here is precisely the danger. We can spend the rest of our lives thinking we hear sound anomalies which will only kill our love of listening to music.

When we begin to listen to music again, and stop being overly critical about what we think we hear, everything changes and we can relax again back into the surreal dimension of music's magical spaces.

I agree that a tube amp could do a lot for warming and enriching the tone of the B200, Alpha combination.

With Warmest Regards ~ Richard

[gvimhoof]

Greetings!

I seem to remember you having very shallow wings on your OB.  Is that still the way your speakers are configured?  if you are looking for an actual pic of the MJK cross-over referenced earlier...


later,
G

[opnly bafld]

Hi JohnCZ,

Sorry I didn't see your post earlier. 
Perhaps a PLLXO to high pass the Visaton will work.
The Dayton amp you are looking at has an 18dB/oct crossover which should help tame the rising response of the Alpha.

Lin

[Viridian]

Dr. Dan Mason (the fire carrier who started this particular fire on this chat room) hated all of that fussy controlling caps, resistors and l-pads and pointed out that they rob the drivers of that ineffable uncanny sound-space dimension that they are capable of when left alone (well at least with the minimum of stuff... I can see using a simple copper coil to cut off the higher frequencies on the Alpha's, which I use).


With Warmest Regards ~ Richard

Hey Richard,
You should see what the good Doctor is listening to now. If there were anything less to get in the way there would be no way.

I really shouldn't speak for him, though.

Cryptically,
Erik

[painkiller]

One cannot design a passive crossover for the Alpha 15A's without response and impedance measurements combined with simulations. The theoretical results you get from a crossover calculator will not reflect the real life performace of the filter in any way.

A 2nd order crossover with this driver will give a very steep rolloff at 500 Hz, regardless of the theoretical crossover point. A first order crossover is practically useless, as you'll still get plenty of output up to 2 kHz. MJK's suggested filter is ok, but the 9 mH coil will reduce overall output quite a lot. You might as well go for 2 mH + 100 uF. This will increase overall output and reduce the output above 500 Hz even more.

[canzld]

I like your suggestion Vix, of using Nelson's B5 "active" cross-over component... it sounds perfect (thanks for the link).

Hi Richard

I don't know if you went back to the solid state/tube mix to run your OB - but in the line of active crossovers, you might want to consider miniDSP

http://www.minidsp.com/

I am now running my B200/alpha OB with this and an tube/SS combo. The miniDSP is (currently) $125 + 10 for the software, all you need is a computer to configure it. It's pretty idiot friendly, as even I can use it. It lets you very easily enter all sorts of crossover points and slopes (6 to 48dB, LR or BW) and quickly assess them. I have only been playing with it for a little while, but I think it is a very good product, pretty transparent to my ears.

All the best