David McBean said:
Great info! I've been wanting to do box modeling with non-zero output Z. Different I know, still I need to learn hornresp.
Jmmlc said:
Interesting..... 55 Ohm source driving an 8 Ohm coil.
It does not seem to bother the tubes?
There are those who say that the resistive dividers used in passive crossovers actually help the compression drivers. Might be a similar effect.
Hello Panomaniac,
My 20W SE Shabda amplifier is conceived in order to operate more as a transconductance amplifier than as a voltage amplifier.
The main difference for the output tube is that it must accept larger voltage swing. But the tube I used (a rare ADZAM tetrode with 3mm graphite) can accept a lot more than I actually demand to it. BTW, this output tetrode is screen driven which is actually the most linear operation mode for tubes.
Best regards from Paris France,
Jean-Michel Le Cléac'h
My 20W SE Shabda amplifier is conceived in order to operate more as a transconductance amplifier than as a voltage amplifier.
The main difference for the output tube is that it must accept larger voltage swing. But the tube I used (a rare ADZAM tetrode with 3mm graphite) can accept a lot more than I actually demand to it. BTW, this output tetrode is screen driven which is actually the most linear operation mode for tubes.
Best regards from Paris France,
Jean-Michel Le Cléac'h
panomaniac said:
Speaking of Onkens and such, I came across an odd 15" driver I'd never seen before. A bit "old fashioned" in its specs.
•Sensitivity: 98dB (W/M)
•Impedance: 8ohm
•Re: 6.6ohm
•Le: 1.2mH
•Fs: 28Hz
•Qts: 0.23
•Qes: 0.27
•Qms: 1.46
•Vas: 463 (liters)
•Xmax: 4.4mm
Unusual to see a pro 15 these days with a Qts of 0.23 and an Fs of 28. Vas is in the medium range. Le a bit high, but power handling is better than vintage.
(I've been looking for a modern Altec 416, but have not quite found it.)
It's a mid to low price driver from MCM.
http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-55-1880-/55-1880
Cheaper in the print catalog then online.
•Sensitivity: 98dB (W/M)
•Impedance: 8ohm
•Re: 6.6ohm
•Le: 1.2mH
•Fs: 28Hz
•Qts: 0.23
•Qes: 0.27
•Qms: 1.46
•Vas: 463 (liters)
•Xmax: 4.4mm
Unusual to see a pro 15 these days with a Qts of 0.23 and an Fs of 28. Vas is in the medium range. Le a bit high, but power handling is better than vintage.
(I've been looking for a modern Altec 416, but have not quite found it.)
It's a mid to low price driver from MCM.
http://www.mcmelectronics.com/product/MCM-AUDIO-SELECT-55-1880-/55-1880
Cheaper in the print catalog then online.
Okay I know it's been a while but a mini update and I'll also need some help.
Have been listening extensively with the Behringer active x-over and I'm now happy with the following cross-over points.
Bass 1000 Hz 1st order low pass
Mid 1000 Hz 2nd order high pass
Treble - I've placed a 1 uF cap there which roughly high passes at 10.5kHz
Can anyone spot any problems and what's the best way for me to translate this into a passive cross-over?
Thanks in advance.
JJ
Have been listening extensively with the Behringer active x-over and I'm now happy with the following cross-over points.
Bass 1000 Hz 1st order low pass
Mid 1000 Hz 2nd order high pass
Treble - I've placed a 1 uF cap there which roughly high passes at 10.5kHz
Can anyone spot any problems and what's the best way for me to translate this into a passive cross-over?
Thanks in advance.
JJ
Hi Lynn,Lynn Olson said:
I've been reading this book as well and find it very informative. But do you know if there is a better description of the AX2 horn anywhere?
Right, this thread has resurfaced so I'd thought I'd post an update. Decided to go 1st order 1000Hz on mid and bass in the end. This was based on listening with the Behringer and also, deciding to keep things as simple as possible. Couldn't hear any distortions in the stop band even though the mid actually goes quite low, down to 450 Hz before the Fc of the horn kicks in.
Currently just going by trial and error with the LC values. Have got an estimate from web calculations and testing values either way.
On the mid, there is a 10dB l-pad (10R and 8R). Cap is 5.6uF.
On the bass, there is a Zobel (15uF, 15R). Inductor will be in between 2.5 - 3.0 mH. Trying different value DCR resistances as well.
Not using the tweeter at the moment but it'll be easy to slot in later...
Sound is actually not bad. For those earlier on thinking about building a 414 in Onken enclosure, I would happily recommend. As people have said, it's a quick sounding bass with a wonderful sounding mid section that easily goes up to 3kHz. The trick I found was getting the damping right. I initially used too much, ie 1.5cm lambswool. Now I've got it around 0.5cm and it is less muffled.
The Onken mid driver is very satisfying. It has a very clear character. Very transparent and conveys subtleties very well. Music comes across like fine, crystal clear water in a stream.
So almost there, and just need to do the final cross-overs. I've done RTA measurements along the way but as they are not professional, I have not posted.
JJ
Currently just going by trial and error with the LC values. Have got an estimate from web calculations and testing values either way.
On the mid, there is a 10dB l-pad (10R and 8R). Cap is 5.6uF.
On the bass, there is a Zobel (15uF, 15R). Inductor will be in between 2.5 - 3.0 mH. Trying different value DCR resistances as well.
Not using the tweeter at the moment but it'll be easy to slot in later...
Sound is actually not bad. For those earlier on thinking about building a 414 in Onken enclosure, I would happily recommend. As people have said, it's a quick sounding bass with a wonderful sounding mid section that easily goes up to 3kHz. The trick I found was getting the damping right. I initially used too much, ie 1.5cm lambswool. Now I've got it around 0.5cm and it is less muffled.
The Onken mid driver is very satisfying. It has a very clear character. Very transparent and conveys subtleties very well. Music comes across like fine, crystal clear water in a stream.
So almost there, and just need to do the final cross-overs. I've done RTA measurements along the way but as they are not professional, I have not posted.
JJ
I tried plugging in published T/S parameters for the Altec 414-16C into the Debien spreadsheet and I get some pretty absurd results that are nowhere near the Petite Onken.
Has anyone tried a 414 in a box designed using this spreadsheet? It makes me wonder if any of this Onken stuff is meaningful at all.
John
Has anyone tried a 414 in a box designed using this spreadsheet? It makes me wonder if any of this Onken stuff is meaningful at all.
An externally hosted image should be here but it was not working when we last tested it.
John
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No, not the 414 but I have tried a variety of other Altec drivers like the 515 and designed and built a good performing set of Onkens using Iconic 165-8 drivers using this spreadsheet. (The Iconic is similar to a 515-8G)
The spread sheet was designed for the standard Onken, and I am not sure how the Petite differs. Note it does take quite a lot of finessing with the numbers to get it right, and Rg should not be zero.. (or even close to it)
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But varying Rg doesn't alter any of the dimensions, it only changes the predicted performance. Slightly altering a parameter like the radiating area of the cone (which is not that easy to determine correctly) changes the dimensions of the slots significantly.
John
John
This is true.. Takes a lot of tweaking. Changing Rg does affect the Q which may allow you to alter other box parameters to bring things in line with the spreadsheet criteria. I think the spreadsheet is rather finicky, the box design in practice seems much less so. I'm quite happy with mine and I've had a lot of opportunity to listen to different bass boxes both here and at friends homes - they are well damped and produce pretty clean sounding bass. Obviously there are issues with port combing and it has been alleged that they generate more distortion than some other box designs. Whilst not perfect I would not trade them for anything else I have heard in recent times, and boy are they efficient..
I played around with the spreadsheet and got some acceptable results for my project (2 x 414-16c). The total area of the vent is just under 80% of the radiating area of the two cones but I believe this is acceptable. Or am I wrong?
John
John
I could never get the spreadsheet to make sense. Even working backward from known or published 416-A specs, I never arrived at the Onken boxes I've seen and heard.
Should be greater than >85% of SD. I'm right around that number..
With dual drivers some parameters are multiplied or divided and I never remember which off the top of my head, you might want to make sure you've got it right. (I'd probably screw it up.. 😀)
The alignment you choose makes a big difference to the results you get.. (That N number thing.. )
Mine are based on results calculated from that spreadsheet so it is possible to realize a good Onken box using the calculator.
Send me a PM with your email addy and I can send you my debien based spreadsheet. It has some additional explanations and some units are translated from SI units to ones we understand here.. 😀
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