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8th May 2011, 02:42 PM  #11 
diyAudio Member
Join Date: May 2007

All of the above designs are wrong. This as Rg of the 300B or 2A3 amps should be added. Something that I forgot.
So instead of adding 0,2ohm you should add in the ballpark of 2ohms. Far to long vents and a boxvolume of over 300dm3. 
8th May 2011, 08:15 PM  #12  
diyAudio Member
Join Date: Nov 2004
Location: Vancouver

Quote:
Do you mean this driver is not suitable for the Onken ?? Albert 

8th May 2011, 08:37 PM  #13 
diyAudio Member
Join Date: May 2007

Hello Albert,
Probably. Could be hard to make the very long port to behave. But you try and decide. Another thing, about your amps, do you have 4ohm outputs on them? If so, Rg might be somewhat lower. 
8th May 2011, 11:41 PM  #14 
diyAudio Member
Join Date: Nov 2004
Location: Vancouver

All my amps are 8 ohm.
I thought I'd put them up for the other project. Thanks Albert 
9th May 2011, 12:02 AM  #15 
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Join Date: May 2005
Location: Melbourne

Sorry about that albertli but I have no experience at all with valve amps so was not aware of what has just been posted.
jamikl 
9th May 2011, 01:13 AM  #16  
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Join Date: Nov 2004
Location: Vancouver

Quote:
BR Albert 

9th May 2011, 02:35 AM  #17  
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Join Date: Jun 2003
Location: Chamblee, Ga.

Quote:
Quote:
You mentioned this before, but don't know what you're referring to. For sure, this isn't based on any calculation I've posted. I'm not good at math either, but fortunately one doesn't need to know any math more complex than addition, subtraction, division to use CMB's spreadsheet [SS] calculator. Unfortunately for most folks who come to these forums though is that it requires you have a basic understanding of what you're inputting when using a calculator that requires more than the basic T/S specs ['Fs', 'Vas', 'Qts'] and in the case where multiple drivers are desired, how to change the specs to get an accurate calculation. For the math challenged, he further complicated it by using scientific notation and m^2 for 'Sd' instead of the more common cm^2, which is where you messed up, so one must have a conversion chart or program such as 'Convert' to help folks like us. To convert cm^2 to m^2 requires dividing it by 10,000, so would be inputted as 0.03501 which the SS will display as 3.501E02. With this change, 'Vas' will shrink by a factor of 10,000 which will then allow the SS to calculate a more reasonably sized box with vents that can actually be built in accordance with the physical laws of our universe. Note that I get a ~5.15% smaller cab using CMD's designer compared to mine for a N=6.34 alignment due to the difference in Vas, so there's some minor discrepancies in the 2510's other published specs and of course measured specs may make either off by a higher percentage. Finally, you only simmed one driver, not two, which requires a bit more simple math to combine their specs: http://www.quarterwave.com/General/Two_Drivers.pdf The easy way to design a two driver cab is to just design for one driver and double 'Vb', 'Vb total' and the vent's height or whatever you prefer to do to double the vent area. You list Rg = 0.3 ohms which might not even account for all of any XO resistance if a passive is used and tube amps, especially SETs, can have a very high output impedance that will dramatically increase the cab's size due to it raising Qts. Also, to maximize wide BW efficiency with these types of amps it's common to series wire drivers to sum inductance ['Le'] and raise 'Re' which also minimizes any added series resistance impact on Qts. Regardless, like most modern drivers, this one has specs designed to work well in a relatively small cab to meet the performance needs of a prosound application [app] with the design tradeoff being lower efficiency, so isn't suitable for a 'pure' Onken loading. Of course you can either reduce the vent area to as little as 70% of Sd to get them as short as practical and/or accept the stronger pipe harmonics of longer vents which can be damped empirically if they audibly 'color' [distort] the mids too much. GM
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9th May 2011, 02:54 AM  #18 
diyAudio Member
Join Date: May 2005
Location: Melbourne

I was hoping you would drop in on this one GM. I think I used your sheet for the attachment I did but did not realise that the valve amp had much higher output impedance.
What is CMD's designer you refer too? jamikl 
9th May 2011, 02:56 AM  #19 
diyAudio Member
Join Date: May 2005
Location: Melbourne

Ignore the question. CMD is the one I have but I thought you made it available.
jamikl 
9th May 2011, 04:07 AM  #20 
diyAudio Member
Join Date: Nov 2004
Location: Vancouver

GM
Thanks for your guidance and I'd try to do the math more carefully. Jamikl, Thanks and do give any suggestion you could think of. Albert 
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