Hi
Thanks for your two emails. I too have been spending my time before deciding what to do. Many have told me to dump the B139s and buy something more modern. But I keep coming back to them. I considered a transmission line but as the B139s are not that efficient (90 dB w/m) and the xmax and power handling are both limited, it seems that a tapped horn is the way to go, if I use the B139s.
At somewhere around 200 litres the box would be large but not too large. Like you I am interested in using the space under the TV (or a tall unit in the corner). Our house in Derby is of moderate size so my belief is the 139s will be sufficient - so I have decided to give it a go!
The design with a low frequency of around 17.5 Hz seems to me to be the one to decide on. I will have a look but I fear that trying to go lower may be achievable but will need a significantly bigger box and the drop in efficiency may bring down total output to a too low level. Over Easter I will try a few changes and see what comes out.
I have a concern about the low pass filter (if necessary) and proper integration with the mid/bass unit. Like you I will have active amps and may use Brutefir for FIR filter deployment but would like to use Brutefir to design the filters and then make some active filters which would be analogue. My standalones at the moment are Meridian M60s and I am very pleased with them apart from the low bass. I intend to use the units and amps etc to design the system from the sub up.
I will let you know if I can modify the designs suggested so far but bow to the most definite better experience of your helpers to-date.
Kind regards
Martin
PS Just seen the good advice to invert one driver. Absolutely, if there is room
Thanks for your two emails. I too have been spending my time before deciding what to do. Many have told me to dump the B139s and buy something more modern. But I keep coming back to them. I considered a transmission line but as the B139s are not that efficient (90 dB w/m) and the xmax and power handling are both limited, it seems that a tapped horn is the way to go, if I use the B139s.
At somewhere around 200 litres the box would be large but not too large. Like you I am interested in using the space under the TV (or a tall unit in the corner). Our house in Derby is of moderate size so my belief is the 139s will be sufficient - so I have decided to give it a go!
The design with a low frequency of around 17.5 Hz seems to me to be the one to decide on. I will have a look but I fear that trying to go lower may be achievable but will need a significantly bigger box and the drop in efficiency may bring down total output to a too low level. Over Easter I will try a few changes and see what comes out.
I have a concern about the low pass filter (if necessary) and proper integration with the mid/bass unit. Like you I will have active amps and may use Brutefir for FIR filter deployment but would like to use Brutefir to design the filters and then make some active filters which would be analogue. My standalones at the moment are Meridian M60s and I am very pleased with them apart from the low bass. I intend to use the units and amps etc to design the system from the sub up.
I will let you know if I can modify the designs suggested so far but bow to the most definite better experience of your helpers to-date.
Kind regards
Martin
PS Just seen the good advice to invert one driver. Absolutely, if there is room
Yes, that is part of the plan-with the original design Bjorno submitted it looked to be possible-hopefully with an increase in achievable horn volume it will be easier to implement and I can eek down a few more Hz in the register.
Thanks Martin.
The original design put forward by Bjorno was F3 18Hz and flat to 60Hz(IIRC) so a very good design for the space, it's T-TQWT (Tapped, Tapered, Quarter-Wave tube) which I'd not come across before but models very well. At just over 180litres, 90db @ 2.83v with the drivers in parallel does it fit within your criteria?
Alas, my crossovers won't be as sophisticated - to start with anyway!
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