I am designing the XO for an MTM centre, the woofers have a sensitivity of 88db whilst the tweeter is 91db the woofers are 8ohm and have an Re of 5.7ohm, the tweeter is 6ohm and has an Re of 4.6ohm.
Im using XOsim to work out the figures, because the 2 woofers in parralel will be 91db this matches the tweeter, but the impedance will be lower,
do i need to compensate for this?
Im using XOsim to work out the figures, because the 2 woofers in parralel will be 91db this matches the tweeter, but the impedance will be lower,
do i need to compensate for this?
The two woofers is paralell raise sensistivity by 6dB.
However you need to take baffle step correction into
account, this will reduce midrange sensistivity by 6dB.
So your tweeter needs to be padded by ~ 3dB.
Tried checking out XOsim, can't find it,
many crossover sim's are far too simplistic.
🙂 sreten.
However you need to take baffle step correction into
account, this will reduce midrange sensistivity by 6dB.
So your tweeter needs to be padded by ~ 3dB.
Tried checking out XOsim, can't find it,
many crossover sim's are far too simplistic.
🙂 sreten.
so how do i make a baffle step circuit?
are there any decent calculators online?
and also how to i pad the tweeter?
are there any decent calculators online?
and also how to i pad the tweeter?
michael said:
a) Is complicated by the intended positioning of the centre
speaker, but basically a first order L or L//R in series
with the drivers followed by the crossover components.
b) I can't find a freeware one as yet, I've been looking.
c) R in series and parallel with the tweeter.
🙂 sreten.
okay thats good info thanks sreten.
how do i workout what value that is of the L or L//R in the step. is there an equation to work it out, here is my XO so far.
how do i workout what value that is of the L or L//R in the step. is there an equation to work it out, here is my XO so far.
An externally hosted image should be here but it was not working when we last tested it.
Its too simplistic.
The important thing is that the crossover is properly designed
to take into account the bass units inductance, the tweeters
fundamental resonance, any frequency response quirks of the
drivers, different sensitivities of the drivers, phase response at
crossover including the drivers phase response and offset, baffle
step compensation according the baffle width, acoustic summing
of the drivers at crossover, and off-axis dispersion issues.
You also have twin drivers - which needs to be accounted for.
Why I can't find a good freeware simulator.
They don't take acoustic issues into account.
🙂 sreten.
The important thing is that the crossover is properly designed
to take into account the bass units inductance, the tweeters
fundamental resonance, any frequency response quirks of the
drivers, different sensitivities of the drivers, phase response at
crossover including the drivers phase response and offset, baffle
step compensation according the baffle width, acoustic summing
of the drivers at crossover, and off-axis dispersion issues.
You also have twin drivers - which needs to be accounted for.
Why I can't find a good freeware simulator.
They don't take acoustic issues into account.
🙂 sreten.
here is the prgram i used so far http://www.geocities.com/f4ier/newxoversim.htm
there are some functions in it that i do not know how to use
there are some functions in it that i do not know how to use
I've seen this sim before, I'll check it out some more,
but it does not seem to be able to model the MTM
configuration acoustically.
🙂 sreteen.
but it does not seem to be able to model the MTM
configuration acoustically.
🙂 sreteen.
thanks sreten once again, so if ya chek that out for me id be very happy 🙂
just email me if thats easier😀
just email me if thats easier😀
Hi,
Crossover Simulator can simultaneously handle up to 6 drivers, which means an MTM configuration should be a piece of cake. There is no limit to the size of your FRD and ZMA files (at least none that I know of) 🙂
XoverSim being incomplete (due to lack of time on my part), only the circuit simulation part is functional. In fact, that's all it is at the moment -- a general circuit simulator.
It helps a great deal if you have actual acoustical and electrical measurements of your drivers because things like propagation delays and baffle diffraction are already given (by the measurements). Otherwise ARPE, BDS, FRC and SPLTools can help post process manufacturer-supplied response graphs. These tools and more are available from the FRD Group.
For the wiring diagram you've shown, the "Series Filters" circuit input area should be the one to be used. Anything you can define in the "Parallel Filters" section you can also define in the Series Filters section in one go. I only included the 6 separate Parallel Filters input sections for convenience.
hth
Isaac
Crossover Simulator can simultaneously handle up to 6 drivers, which means an MTM configuration should be a piece of cake. There is no limit to the size of your FRD and ZMA files (at least none that I know of) 🙂
XoverSim being incomplete (due to lack of time on my part), only the circuit simulation part is functional. In fact, that's all it is at the moment -- a general circuit simulator.
It helps a great deal if you have actual acoustical and electrical measurements of your drivers because things like propagation delays and baffle diffraction are already given (by the measurements). Otherwise ARPE, BDS, FRC and SPLTools can help post process manufacturer-supplied response graphs. These tools and more are available from the FRD Group.
For the wiring diagram you've shown, the "Series Filters" circuit input area should be the one to be used. Anything you can define in the "Parallel Filters" section you can also define in the Series Filters section in one go. I only included the 6 separate Parallel Filters input sections for convenience.
hth
Isaac
Hi Isaac,
the above is from your notes.
So I concluded multiple drivers handling the same
frequency range are not acoustically modelled.
So an MTM cannot be acoustically modelled.
If it can your notes are very confusing.
🙂 sreten.
sreten,
Given only one set of measurements for a driver unit, but multiple instances of which, would not yield accurate acoustic results because the code at the moment does not allow the user to enter driver orientation on the enclosure.
This basically means that XoverSim relies on the user's measurements (or data post processing with other FRD tools) to include offsets, propagation delays etc... It really is only a circuit simulator at the moment.
Michael plans to use 2 of the same woofers per enclosure, so he would need to measure each one separately. Alternatively, he could process manufacturer's graphs to make virtual measurements.
XoverSim can handle both acoustical and electrical driver data; just make sure the supplied data is correct.
cheers 🙂
Isaac
Given only one set of measurements for a driver unit, but multiple instances of which, would not yield accurate acoustic results because the code at the moment does not allow the user to enter driver orientation on the enclosure.
This basically means that XoverSim relies on the user's measurements (or data post processing with other FRD tools) to include offsets, propagation delays etc... It really is only a circuit simulator at the moment.
Michael plans to use 2 of the same woofers per enclosure, so he would need to measure each one separately. Alternatively, he could process manufacturer's graphs to make virtual measurements.
XoverSim can handle both acoustical and electrical driver data; just make sure the supplied data is correct.
cheers 🙂
Isaac
sreten, your comments here and on other threads has been very useful. but would you be able to do me a big big favour, could you design a simple crossover for an MTM centre using the peerless 850520 (here) and the vifa D26NC tweeter found (here) , it doesnt have to be anything special, just something that i can make with reasonable priced components.🙂
I'm sorry Micheal but I can't really do that.
I hope you realise that I do not regard proper crossover design as a trivial task.
I'd need to be familiar with a commercial emulator such as Calsod or LEAP
to produce a reasonable design, and I don't have such an emulator.
Even so measurements and listening are still an important factor.
If you haven't bought the drive units I'd recommend building a good well documented and developed design.
I'll also point out my knowledge of centre speaker design regarding the effects of placement is very rudimentary.
🙂 sreten.
I hope you realise that I do not regard proper crossover design as a trivial task.
I'd need to be familiar with a commercial emulator such as Calsod or LEAP
to produce a reasonable design, and I don't have such an emulator.
Even so measurements and listening are still an important factor.
If you haven't bought the drive units I'd recommend building a good well documented and developed design.
I'll also point out my knowledge of centre speaker design regarding the effects of placement is very rudimentary.
🙂 sreten.
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