strangeandbouncy
Well-known member
HI,
my chum took back his LS3 5as. Even after he said I could keep them at least for comparison in development. Ho Hum.
So I am forging ahead with my unusual nearfields! For now, I am not going to mess with transmission line, but build sealed boxes. - I need something pdq! Thanks to a member here, I have a BSS FDS360 active crossover, my amps, Monacor SBH-130 5 inch drivers, and KEF T27 tweeters. tomorrow I am seeing a cabinet maker who is going to knock up some boxes to prototype. I have calculated an internal volume of @5.7 litres, pretty much the same as the original LS3 5a in fact. Another online calculator gives a smaller volume(approx 20%), citing a need to add 20% for un-damped drivers. This same site
http://www.lautsprechershop.de/english/index_tools.htm
has a calculator to re-calculate the volume as Qts varies with series resistance. - Never came across this before!. Monacor SBH130 is way more efficient than T27, (89dB for 1Watt @1m against 80dB for 1 Watt @1m). I can well afford to lose some efficiency here. It seems I can get a slightly lower system cut-off by inserting a resistor in series at the expense of a bigger box. I am assuming a recommended Qtc of 0.71. Maybe I wont need to eq the bass so much, if at all, to achieve a similar response to the LS3 5a . . . Perhaps I can extend even lower if I eq as well!
Here is a table form the caculator.
resistance Volume -3dB -8dB
0 4.7l 99Hz 63Hz
1 Ohm 6.7l 85Hz 55Hz
2 Ohm 8.9l 77Hz 49Hz
3 Ohm 11.7l 70Hz 45Hz
4 Ohm 15.4l 64Hz 41Hz
These volumes are for so-called damped drivers, and are 20% smaller than expected. I shall allow the extra 20%, and add extra wooden blocks if necessary to reduce the volume.
it looks like I can potentially achieve the same response as a LS3 5a(-3dB @ 70Hz) WITHOUT eq, by approximately doubling the volume and a bit more) and adding a 3 Ohm resistor in series. Size is not an issue here for me. I will also lose about 3dB. Again, not a problem. All bodes well! Yay!
I have also managed to score an incredibly rare BSS eq card to go in the FDS360 if I need it - for a measly sum. Those puppies are rarer than rockinghorse Sh*t!
Very excited about this. I am hoping that the Monacor will do the business. It looks good on paper, and is the flattest I could find from 100Hz to nearly 10k. Everyone is singing the praises of another Monacor 5 inch, the SPH-135AD. Looks much worse on paper, being far from flat. If this doesnt work, I am going to look at the Beyma5MP60N. It is more suited to bass-reflex, and has some nasty cone breakup like all polypropylene drivers seems to. There is also a 5inch from Coles, but I cant find any proper info yet.
Any comments would be most gratefully received!
ANdyP
my chum took back his LS3 5as. Even after he said I could keep them at least for comparison in development. Ho Hum.
So I am forging ahead with my unusual nearfields! For now, I am not going to mess with transmission line, but build sealed boxes. - I need something pdq! Thanks to a member here, I have a BSS FDS360 active crossover, my amps, Monacor SBH-130 5 inch drivers, and KEF T27 tweeters. tomorrow I am seeing a cabinet maker who is going to knock up some boxes to prototype. I have calculated an internal volume of @5.7 litres, pretty much the same as the original LS3 5a in fact. Another online calculator gives a smaller volume(approx 20%), citing a need to add 20% for un-damped drivers. This same site
http://www.lautsprechershop.de/english/index_tools.htm
has a calculator to re-calculate the volume as Qts varies with series resistance. - Never came across this before!. Monacor SBH130 is way more efficient than T27, (89dB for 1Watt @1m against 80dB for 1 Watt @1m). I can well afford to lose some efficiency here. It seems I can get a slightly lower system cut-off by inserting a resistor in series at the expense of a bigger box. I am assuming a recommended Qtc of 0.71. Maybe I wont need to eq the bass so much, if at all, to achieve a similar response to the LS3 5a . . . Perhaps I can extend even lower if I eq as well!
Here is a table form the caculator.
resistance Volume -3dB -8dB
0 4.7l 99Hz 63Hz
1 Ohm 6.7l 85Hz 55Hz
2 Ohm 8.9l 77Hz 49Hz
3 Ohm 11.7l 70Hz 45Hz
4 Ohm 15.4l 64Hz 41Hz
These volumes are for so-called damped drivers, and are 20% smaller than expected. I shall allow the extra 20%, and add extra wooden blocks if necessary to reduce the volume.
it looks like I can potentially achieve the same response as a LS3 5a(-3dB @ 70Hz) WITHOUT eq, by approximately doubling the volume and a bit more) and adding a 3 Ohm resistor in series. Size is not an issue here for me. I will also lose about 3dB. Again, not a problem. All bodes well! Yay!
I have also managed to score an incredibly rare BSS eq card to go in the FDS360 if I need it - for a measly sum. Those puppies are rarer than rockinghorse Sh*t!
Very excited about this. I am hoping that the Monacor will do the business. It looks good on paper, and is the flattest I could find from 100Hz to nearly 10k. Everyone is singing the praises of another Monacor 5 inch, the SPH-135AD. Looks much worse on paper, being far from flat. If this doesnt work, I am going to look at the Beyma5MP60N. It is more suited to bass-reflex, and has some nasty cone breakup like all polypropylene drivers seems to. There is also a 5inch from Coles, but I cant find any proper info yet.
Any comments would be most gratefully received!
ANdyP