I have enough parts to build 8 extra X-Over modules, so I think I'll try a 1st order of about 3.0K, and 3.2K then a 3 order of 2.8K and 2.5K. That still leaves me 4 modules if I go mono (just for test purposes) so I can still try a Time delay on the mains (MTM D'Appolito) to bring the Maelstrom subs up to speed. I must be the first to try this with any of Marchand’s crossovers as he cannot actually tell me how at this time, so he will E--Mail me later this week.
Any Ideas on the best method for testing X-over points and slopes (without using too much test equipment) I have a DIY Panasonic mic capsule on a rod and a Ratshak SPL with the Freq mods.
I'm really interested in seeing what the major overlap of a first order will do with my Adjustable MTM's. I have never tried anything but a 2nd, 3rd, and the existing 4th LR. Also I wish to try a 8th order on the Subs, but Phil said that he will have to research that for me too.
My MTM Main's
http://www.geocities.com/kingdaddykeith/Kingdaddys_SST8_Prototype.html?10166
Any Ideas on any other filter alignments will work with these mains and subs.
Tweets- Vifa XT25
Mid/Woofs Scan Speak- 8530-K00 vented at 40Hz
Woofers- Toby 12" good from about 1.5K to 38Hz
Subs- Maelstrom 18" Vented @20Hz
Now it’s a 4-way so all the drivers can be handles as one or overlapped (asymmetrical slopes), so I'm not sure what’s best or even what to try.
any ideas would be greatly appreciated, there’s far too many variables and things I don't know to do all the guessing on my own, it would be good to know from some of you who have more experience.
I have so much flexibility I don’t know where to begin.
Thanks.
KD
Any Ideas on the best method for testing X-over points and slopes (without using too much test equipment) I have a DIY Panasonic mic capsule on a rod and a Ratshak SPL with the Freq mods.
I'm really interested in seeing what the major overlap of a first order will do with my Adjustable MTM's. I have never tried anything but a 2nd, 3rd, and the existing 4th LR. Also I wish to try a 8th order on the Subs, but Phil said that he will have to research that for me too.
My MTM Main's
http://www.geocities.com/kingdaddykeith/Kingdaddys_SST8_Prototype.html?10166
Any Ideas on any other filter alignments will work with these mains and subs.
Tweets- Vifa XT25
Mid/Woofs Scan Speak- 8530-K00 vented at 40Hz
Woofers- Toby 12" good from about 1.5K to 38Hz
Subs- Maelstrom 18" Vented @20Hz
Now it’s a 4-way so all the drivers can be handles as one or overlapped (asymmetrical slopes), so I'm not sure what’s best or even what to try.
any ideas would be greatly appreciated, there’s far too many variables and things I don't know to do all the guessing on my own, it would be good to know from some of you who have more experience.
I have so much flexibility I don’t know where to begin.
Thanks.
KD
Whew! Where to start....?
Testing crossovers. OK, there are two necessary tests, the electrical one and the acoustical one. It's rare that an acoustic crossover matches an electrical one because it also includes the frequency resposne of the drivers.
Electrical is easy. I would use the FFT/MLS method, since it's really fast and the equipment requirements are pretty simple. You input the MLS or impulse to the speaker system, then measure the response at the driver terminals. The two responses are then ratioed. This can also be done slowly and tediously with a signal generator, a test amp, and a scope or AC voltmeter.
If there's no passive xover, it's all active, then measure the input to the modules, measure the output, and then ratio the input to the output. Same test setup as passive.
Now the acoustic slopes, where you will hit your great disappointment. Turn off all drivers other than the one you want to measure, then go boy go, using your frequency respose setup and your test mike. Remember to average over several positions, keeping the mike/driver distance constant (1 or 2 m)- if you use impulse methods (recommended), cut the room reflections out of the impulse response before transforming! You can also use groundplane methods, well-detailed in d'Appolito's book (which you ought to have). For frequencies below 300 Hz or so, nearfield responses can be spliced in.
You'll probably find that the acoustic slopes look nothing like first order.
Testing crossovers. OK, there are two necessary tests, the electrical one and the acoustical one. It's rare that an acoustic crossover matches an electrical one because it also includes the frequency resposne of the drivers.
Electrical is easy. I would use the FFT/MLS method, since it's really fast and the equipment requirements are pretty simple. You input the MLS or impulse to the speaker system, then measure the response at the driver terminals. The two responses are then ratioed. This can also be done slowly and tediously with a signal generator, a test amp, and a scope or AC voltmeter.
If there's no passive xover, it's all active, then measure the input to the modules, measure the output, and then ratio the input to the output. Same test setup as passive.
Now the acoustic slopes, where you will hit your great disappointment. Turn off all drivers other than the one you want to measure, then go boy go, using your frequency respose setup and your test mike. Remember to average over several positions, keeping the mike/driver distance constant (1 or 2 m)- if you use impulse methods (recommended), cut the room reflections out of the impulse response before transforming! You can also use groundplane methods, well-detailed in d'Appolito's book (which you ought to have). For frequencies below 300 Hz or so, nearfield responses can be spliced in.
You'll probably find that the acoustic slopes look nothing like first order.
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