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In Reply to: RE: Current Maggies run full range compared to high pass and subs. posted by ColinB on December 28, 2020 at 21:55:25
It's the low-pass behavior of the subs that necessitates the type of integration. This is defined (and not alterable) in many cases, so you'd probably want to try and match that.....whatever it is.
Whether the sub is dipole or sealed-box is another aspect. I think it's preferable to use dipole subs, but box subs are much more available and easier to get started with.
Thanks for the info. I see. So if your sub's own control had a 4th order LP, for example, the method of first order on the Maggies at their bass roll of point might work ok?
Would a PLLXO (single cap) be ok to use before the speaker power amp to get that 1st order HP or would you be better off using something like a minidsp?
This 1st order HP method you suggested obviously doesn't have as much filtering as if you rolled up the Maggies higher up, say at 80 Hz with a 4th order active HP. Is the former method sufficient in removing enough low frequencies in the signal to protect against excursion, and get a fair amount of higher max volume?
Appreciate dipole subs will integrate better than box ones. I tried an open baffle sub before in my system but it never worked well. Looks like you need quite a few very light drivers, and preferably a servo amp. That GR research sub setup isn't too cheap I guess..
A simple capacitor in front of your amplifier will yield the first-order slope, but that only works correctly if you're using the natural roll-off point of the Magnepan's.
If going up higher, like maybe 80Hz, then it's a different scheme and you'd need to adopt a different approach.
A low frequency first-order filter isn't going to help out too much on bandwidth-limitation relative to a 4th-order electrical filter at 80Hz. If a person is looking to play the main speakers a good bit louder than they're capable of driven full range, then the higher frequency/order crossover is preferred. But, (smaller) Magnepan's are limited in their SPL capability anyways, so you can quickly get to the point of diminishing returns.
Yeah that's what I thought. In that video I guess the 4th order active Hp he uses later on in the vid is providing a bit more max vol without distortion, but the small Maggies have limited vol anyways so probably not a huge different to using a first order at Maggies bass roll off freq as you suggest.
I was curious as to whether the distortion you can hear when he runs the Maggies full range at the start of the vid is all due to max panel excursion etc, or if the speaker amp might be clipping a bit too. Guess there is no way to know for certain without measurements.
Thanks for the first order HP tip at the Maggie bass roll off point. It might provide a touch more max vol, less congestion, a bit of driver protection, and might also make sub integration easier. I'll be trying that in the future with the bigger Maggie models. I would assume that the bass extension of the bass panel when run like that is similar or not too much less than when the speakers are run full range, which is handy. Might not need a sub so much like that with a bigger model.
Can use a Pllxo too which is cheap and sounds good.
I've read your comments with interest on this ... when you've referenced crossovers you're referring to analog not digital implementations, correct?
Yes either will work. Digital XO like a minidsp etc or an analogue active XO, or a PLLXO (passive line level XO) which in this case (as it's just a first order high pass required) is just a small line level cap in between pre and power amp. The Pllxo would be my preference as you can use a polypropylene or polystyrene film cap. Very good sound and cheap compared to an active XO that would be comparable.
I bumped into a line level Xover aficionado on high eff. a few days back
never tried them myself
Welcome. Did that guy mean the passive line level type (PLLXO)? I played with these quite a bit a few years ago. They can be very good for cheap money.
One problem I found when biamping the older Maggie MGIIIas and 3.3Rs (which require a 3rd order low pass on the bass) is that when using an HP PLLXO, you can get phase matching issues if you are using a digital crossover for the low pass as digital XOs have a delay. The high pass comes in just before the low pass, although you can phase match it up a bit better by playing with the delay on the digital XO. Although I never tried it (but want to) using a 3rd order Active XO with opamps like a Marchand for the low pass might be much better than a digital XO as there is miniscule delay I believe. You can't easily use a 3rd order low pass PLLXO to complement the high pass PLLXO as there is too much insertion loss with 3rd order.
With the current *.7 Maggies (for biamping) I would assume it would be ok to use a PLLXO for the low pass too (as the speakers use all first order slopes), and you could then adjust the level balance with a pot on the high pass.
he stressed that PLLXO was the 'clear' winner of crossovers, money no object
unless I read him wrong
all I could respond with was that I miss tone controls, which totally misses the point of course ... as it turns out some find my sparkling wit rather dull, knuckle dragging troglodyte that I am
<> ¯\_(ツ)_/¯ <>
Haha. I miss tone controls sometimes too :-)
I used to use Wima FKP1 caps (film and foil polypropylene) for the high pass PLLXO. Cost about $3 each and sounded v good. More exotic cap options would have improved things more.
I never got as good sound as a PLLXO when using an active XO or digital XO on the high pass instead.
No, either way (analog or digital) can work.
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