Just bought two 16mh coils to add a passive xover. The drivers are 15ohm wharfedale W15 RS models. The Mids are 15ohm Goodmans. The DIY xover calculator gave me a value of 15.9mh for a 1st order Butterworth @ 150 hz. I normally use an active xover and have kept that in place thinking that I would dial up to higher xover points and see if the inductors hold the xover frequency at 150 hz as designed. They don't. In fact I can hear well into the vocal range.
I have no way to measure the coils so assuming they are correct, what else might not be working?
Thanks Jason
I have no way to measure the coils so assuming they are correct, what else might not be working?
Thanks Jason
Hi,
The x/o calculator assumes 15R loads, which is not the case.
Driver inductance means you may get a droop, but the effect
will level off to to give an attenuator related to the the ratio
of the coil and the driver inductance, i.e. no treble roll-off.
Zobelling the driver might work, thereagain that is just
a variation of converting it to a 2nd order lowpass and
that will work with non Zobel values for R and C.
rgds, sreten.
The x/o calculator assumes 15R loads, which is not the case.
Driver inductance means you may get a droop, but the effect
will level off to to give an attenuator related to the the ratio
of the coil and the driver inductance, i.e. no treble roll-off.
Zobelling the driver might work, thereagain that is just
a variation of converting it to a 2nd order lowpass and
that will work with non Zobel values for R and C.
rgds, sreten.
Wow, I thought this would be easy. A 2nd order calls for a 22mH coil! Any gains I could possibly garner from lowering the impedance my chip amp will see by running these two drivers in parallel is easily lost in the huge amount of resistance I am gaining with a signal path that will grow by some 200 linear feet or more. Even with 14awg, this can't be good.
As for the Zobell, I would not know where to begin. This all started because I thought my chip amps would be happier seeing 8ohms instead of 15.
As for the Zobell, I would not know where to begin. This all started because I thought my chip amps would be happier seeing 8ohms instead of 15.
Can you give a rough schematic of how many mids and woofers you have, and how they're wired with the inductor?
If you have two woofers wiring on parallel with a singke inductor in series you should be able to add a bypass cap no problem... what do you mean by increasing signal path by 200 linear feet????
If you have two woofers wiring on parallel with a singke inductor in series you should be able to add a bypass cap no problem... what do you mean by increasing signal path by 200 linear feet????
I can't draw a schematic but to clarify, I am currently running open baffles triamped with tripath based amps with an active crossover. I want to lower the impedance on the mid and low freq. drivers from 15ohms to 8ohms by wiring them in parallel to improve distortion in this range and cut back to a 2way rather than 3 way setup. I thought I would simply wire in an inductor coil in line with the LF driver to cross it @ 150 hz. The 16 mH coil had little to no effect. To test it, I wired it while still using the active crossover which I dialed up to xover points north of 150hz. Voices and higher freq. information was easily heard.i hope this helps. Thanks for your input. Jason
Pete, these drivers are all from the 50's and 60's not sure I can get impedance plots but that seems like a good place to start. Can't make my own as I lack the skill and equipment.
Since they are all fairly sensitive drivers (plenty loud even with these low watt chip amps) is the distortion issue a waste of time and now money? $80 dollars for two coils, ouch!
Since they are all fairly sensitive drivers (plenty loud even with these low watt chip amps) is the distortion issue a waste of time and now money? $80 dollars for two coils, ouch!
Hi Rockaway,
I'm not sure if you realize it or not, but an open baffle loudspeaker requires a significant amount of low frequency equalization in order to obtain a flat frequency response.
The un-EQ'd response has a positive slope that rises up from low frequencies. By using a single inductor, you will introduce a negative slope that at best will only serve to flatten the response!
Here is a link that may help with the design of open baffle systems(Dipoles).
A, B, C, Dipole
Scroll down the page till you get to the first frequency response graph and you should see what it looks like. I have no experience of dipole crossover design, but maybe some other DIYAUDIO member can help.
Peter
I'm not sure if you realize it or not, but an open baffle loudspeaker requires a significant amount of low frequency equalization in order to obtain a flat frequency response.
The un-EQ'd response has a positive slope that rises up from low frequencies. By using a single inductor, you will introduce a negative slope that at best will only serve to flatten the response!
Here is a link that may help with the design of open baffle systems(Dipoles).
A, B, C, Dipole
Scroll down the page till you get to the first frequency response graph and you should see what it looks like. I have no experience of dipole crossover design, but maybe some other DIYAUDIO member can help.
Peter
You can't draw a schematic, but you can design a speaker? Weird? 
Generally a second order is used with 15" bass. This is not something you rely on online calculators for. The particular W15RS bass is used in the Airedale with 8mH and 15uF:
http://www.diyaudio.com/forums/multi-way/255182-wharfdale-airedale-cross-over.html
You will find Troels Gravesen a useful resource too: DIY-Loudspeakers
Generally a second order is used with 15" bass. This is not something you rely on online calculators for. The particular W15RS bass is used in the Airedale with 8mH and 15uF:
http://www.diyaudio.com/forums/multi-way/255182-wharfdale-airedale-cross-over.html
You will find Troels Gravesen a useful resource too: DIY-Loudspeakers
Steve, thanks for the link. Good stuff there. Have been reading Troels for years but more for his " take" on various approaches to speaker design. I have used a Sony TA 4300f active crossover to avoid the predicament I now find myself in. Remember the woofer is really a helper coming in much lower than its intended use in the Airdale. They were cheap
$60 us for the pair, Alnico, cast frame etc. My tweeter btw is a wharf. Super3 circa 1956.
I cross that high around 5khz. These drivers ( with the Goodmans 12") blend rather easily given similar design objectives. Point taken however.
$60 us for the pair, Alnico, cast frame etc. My tweeter btw is a wharf. Super3 circa 1956.
I cross that high around 5khz. These drivers ( with the Goodmans 12") blend rather easily given similar design objectives. Point taken however.
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