leo Posted October 27, 2013 Posted October 27, 2013 Hi,has anyone played around with this model and worked out a filter that really helps to tame the response.I would like to try it.Thanks,anyone.Leo.
L J T Posted October 27, 2013 Posted October 27, 2013 http://www.mh-audio.nl/parallelnotchfilter.asp Have a look at the link. It might be a good start for a ballpark figure. 1
georgepapa Posted October 30, 2013 Posted October 30, 2013 (edited) These look pretty good up to about 10khz. Above that they look to roll off naturally at about 6db per octave. Could be well matched with a super tweeter over 5khz with a 2nd order crossover. Try a parallel LC filter with an inductor value at around .8 mh ( for 1000 hz : Re 6.5ohms) and just keep adding parallel resistance till you tame down that rising top end. Use high powered metal oxide resistors. Add about 1.0 ohm at a time. I wouldn't use these as full range drivers. Response above 10khz doesn't look good. So an LC filter with second order crossover to a tweeter would in my opinion be the best solution. Be aware that the LC filter will add resistance and inductance to the load and this must be factored in when designing the proceeding crossover. Cheers george Edited October 30, 2013 by georgepapa 1
henry218 Posted October 30, 2013 Posted October 30, 2013 http://www.diyaudio.com/forums/full-range/192086-now-ff165wk.html have you tried listening off axis? according to that graph, 30deg off axis is the best notch filter. depends on how wide your cabinets are, but BSC (baffle step compensation) prob needed.
henry218 Posted October 30, 2013 Posted October 30, 2013 ok i saw that you were on that thread also. dont worry about the notch filter, BSC is more important, placement and listening axis will take care of the rising response.
leo Posted October 30, 2013 Author Posted October 30, 2013 Thanks.I am thinking of trying a first order c/o at about 3.8k with the Vifa D27,offset inwards so the Fostex will not need to be angled in.Also the baffle will be about 340mm wide.Could be a simple way to go .
henry218 Posted October 30, 2013 Posted October 30, 2013 whats the dimension of your cab? and tweeter position?
leo Posted October 30, 2013 Author Posted October 30, 2013 (edited) 34cm w x47cm h x15cm d.Looking at the fronts,Fostex drivers will be on the extreme outsides and tweeters close to the extreme insides of the cabinets.Boxes will not be angled in at all. Edited October 30, 2013 by leo
henry218 Posted October 30, 2013 Posted October 30, 2013 is that sealed? you wont get any bass from sealed arrangement. have a look at the simulation for SEALED
leo Posted October 30, 2013 Author Posted October 30, 2013 You should not have to ask that question.The Qts tells the story.
henry218 Posted October 30, 2013 Posted October 30, 2013 qts 0.4 could be used in TL, ML TL, TQWT, BR or SEALED well i hope to see some photos later on
leo Posted October 30, 2013 Author Posted October 30, 2013 The Qts is 0.34 This includes all alignments you mantioned but excludes the sealed for the obvious reason.
henry218 Posted October 30, 2013 Posted October 30, 2013 well your dimension suggested a very small BR, around 12-15L, are u tuning high fb?
leo Posted October 30, 2013 Author Posted October 30, 2013 Those dimensions will give an internal vol. of 20.5 litres,very close to optimum vol.and lowest bass response for a single chamber B/R.
henry218 Posted October 30, 2013 Posted October 30, 2013 ok, i hope you include the port area and magnet area
henry218 Posted October 30, 2013 Posted October 30, 2013 so the dimension before is internal? i see. is this going to be on the wall? i notice its quite shallow
leo Posted October 30, 2013 Author Posted October 30, 2013 The shallow aspect gives the opportunity to make a wider baffle and keep the correct internal vol.Better for BSC control over mid range emphasis.
henry218 Posted October 30, 2013 Posted October 30, 2013 Leo, just before you start the cab, have a look at this Box Volume And Vent Calculator Cm Height (Outside Dim) 47 Width (Outside Dim) 34 Depth (Outside Dim) 15 Wall Thickness 1.8 Baffle Thickness 1.8 Volume - Vab (Liters) 14.81 Port Diameter 5 Port Length 12 Number of Ports 1 Tuned Port Fb 50.4 Hz cheers henry
davewantsmoore Posted October 31, 2013 Posted October 31, 2013 (6db @ 3.8khz) Cross higher and or steeper otherwise the lower end of the tweeter is going to put a large peak in your off axis response through 1-4khz I can't help thinking that a notch filter and a 2nd order cross to a dome, is really over complicating things ... and will probably upset the power response unless you use a waveguide on the tweeter and cross quite low .... and then you don't need such a lightweight driver.... but you don't need me to tell you there are 17 thousand ways to skin cats. Post #3 has it... and the filter you require will depend on your listening axis... perhaps try an electronic crossover temporarily to 'dial it in' before building.
leo Posted October 31, 2013 Author Posted October 31, 2013 I am using 12mm melamine with a broomstick verticle and horizontal brace,so it will be larger than what it seems,but i will increase the heightby 50mm.Re the point about C/O slopes,I have a second order Linkwitz/Riley at 3K ready to go if the Vifa observation should prove true and just swap the two networks over.
henry218 Posted October 31, 2013 Posted October 31, 2013 ok, looks like you are set. dont forget the photos
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