Hi. I built a mullard 3-3 valve amp and have a cheap Visaton bg17 driver, currently sat in a hole in the lid of an empty chocolate tub. I would like to improve on my current setup!
I was looking at the arpeggio article on this site and wanted to build a sealed enclosure based on the equations in it. However, my driver has Qts=0.74 and when I account for the amp output impedence 1.2 ohms the Qts=0.83, which means the equation for volume gives a negative answer for any Qtc below 0.83. I understand a Qtc of 0.71 is desireable. To get a positive answer I need to use a larger Qtc, and quite a bit larger if I wanted to avoid a huge box. What would you advise doing in this scenario, if I dont want to get a better driver? Should I just accept a larger Qtc and push the box volume as high as my space allows (I could keep Qtc down to 1.1 by using a 25 litre box, the most my space allows). Would a Qtc of 1.2 be so bad?
Or would I be better doing something else (with the current amp and driver - I am only looking to get the most from what I have, mostly as a learning exercise!).
Thanks in advance.
I was looking at the arpeggio article on this site and wanted to build a sealed enclosure based on the equations in it. However, my driver has Qts=0.74 and when I account for the amp output impedence 1.2 ohms the Qts=0.83, which means the equation for volume gives a negative answer for any Qtc below 0.83. I understand a Qtc of 0.71 is desireable. To get a positive answer I need to use a larger Qtc, and quite a bit larger if I wanted to avoid a huge box. What would you advise doing in this scenario, if I dont want to get a better driver? Should I just accept a larger Qtc and push the box volume as high as my space allows (I could keep Qtc down to 1.1 by using a 25 litre box, the most my space allows). Would a Qtc of 1.2 be so bad?
Or would I be better doing something else (with the current amp and driver - I am only looking to get the most from what I have, mostly as a learning exercise!).
Thanks in advance.
Build a test box and make up your own mind whether a Q of 1.2 is bad or not.
You can put the driver on an open baffle, then the high Q would be a benefit.
You can staple fabric tightly across the back of the driver to reduce Q somewhat. This would be a process you would have to experiment with.
You can make a pole shifter - linkwitz transform.
You can add a series capacitor to make a 3rd order sealed box.
Add a woofer and cross the BG17 over at >200Hz and Q will make no difference at all.
You can put the driver on an open baffle, then the high Q would be a benefit.
You can staple fabric tightly across the back of the driver to reduce Q somewhat. This would be a process you would have to experiment with.
You can make a pole shifter - linkwitz transform.
You can add a series capacitor to make a 3rd order sealed box.
Add a woofer and cross the BG17 over at >200Hz and Q will make no difference at all.
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My first suggestion is just to build a negative volume box. I'll try and find the article I wrote about how to do that.
Just go ahead and build the box as big as you can and stuff the heck out of it. It will probably sound fine. What is the resonance frequency in 25 liters? In 35 liters (theoretical maximum apparent volume when totally stuffed)?
Absolutely. Your time would be far better spent cleaning out your bank account and sending me the money, to take material concerns off your mind and lower your stress level.
You can make a pole shifter - linkwitz transform.
@ Nice theory, but real world drivers don't have responses like theoretical electric filters.
You can add a series capacitor to make a 3rd order sealed box.
@ No
@ The resonance impedance turns this into a mess
@ I had to re-design one of these, and thus found out it is a joke and doesn't work.
Add a woofer and cross the BG17 over at >200Hz and Q will make no difference at all.
@ Yeah, or at least doubtful you'd notice it.
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