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Hi all,
I just picked up a pair of 1.7i's and I'm planning on modding them for an external crossover. Does anyone have a wiring diagram and/or crossover points and slopes?
Thanks!
Follow Ups:
Well got them in the frames and wired conventionally. I'm playing some of my least-well mastered albums while cleaning up to break them in a bit - bass feels pretty weak right now but I think that'll come with time. And with a ALLXO!!
http://www.indiespinzone.com/mag/mag1.7.html
Dave.
Peter Gunn the writer of this article remodels Maggies. He has his point of view. He may be right but the .7 models are ruinous to his business. There is no comparison between the stock 1.7 vs the 1.6,. Bi-amping and crossover mods are great as a hobby and were necessary for the .6 series. I love 1.7 as they are and found room placement and wall modification can create magic. But here is Peter Gunn anyways lest we discover his secret source of cross overs. His work is first rate, if not a tax on first rate speakers. Davy would know more about it tahn Peter Gunn.
do you understand it?
Andy
I believe we had this discussion a couple of years ago when PG first published his version of the schematic. PG was (is) not into electronics and he would be the first to admit it. I believe the schematic below is correct but there are some assumptions that I made about the resistor and the impedance of the drivers. Perhaps those that have the 1.7 can verify the impedances.
Awesome! If I'm bi-amping I' think I'd need:
LPF freq and slope
HPF freq and slope
And the freq/slope between the tweeter/mid to wire in passively.
Looking at your schematic the HPF looks very flat - perhaps that's what Wendall meant when he said it can't be bi-amped.
Let us know how it goes. My guess is that the conductive tape is lighter, which should have some speed benefits, but has higher resistance and therefore lower current flow to the woofer. This could explain them having less bass (if that's true). If that were true, then I would expect bi-amping to bring less benefit than it does to older models.
I do not think the flat wire is lighter than the round one. In case of the 3.7, the flat wire has a larger cross section than the round wire of the 3.6 but there are other changes...
Ok, then my hypothesis would be wrong.
on prior models?
Yes, it is true that in most cases the flat and round wires have the same mass/cross section. This is not true for the mid of the 3.7 but for the rest I think it is. Fitting thinner wires will resultat in a drop of SPL.
I have been working on a model for biamping. The model will have the mid-tweeter and supertweeter still in a series configuration but paralleled to the woofer. If you can get me those impedances, I believe I can get a pretty good simulation which can then be converted to a AXLLO.
Impedance of the drivers? I'm sure I'll need more than my multimeter. Can you point me in right direction?Edit - unless you're looking for straight resistive values - that's easy enough.
Also I get 116.8 for the cap bank, but I also have 1.7i.
Edits: 07/10/15
Yes, the drivers have almost no reactance so the simple resistance is all that's needed. You may have to disconnect the connections at the drivers to get the correct values.
FWIW, the 1 mfd difference (115.8 v 116.8) is immaterial as the caps have a 5-10% tolerance and it is likely that the two sides (left and right) differ by more than 1 mfd anyway.
I independantly came up with my own schematic with my 1.7i. I can't verify Mr. Gunn's is 100% the same but tracing from each driver works the same as mine. Only difference is I had 116.8 for my cap bank and he had 115.8.
Try tracing from the drivers back. It makes more sense that way
Pretty sure this is correct but looks like a short across the mid - not sure how it's driven at all?
I am using ALLXO and two channels/speaker
Should be simple to remove the woofer from the circuit, connect directly to low channel. Takes care of that end.
For the high channel, I foresee issues. I can't simple set the ALLXO and leave the circuit intact, because I'll be stacking HPFs onto the mid - not good. But I don't quite honestly understand how the mid XO is working to avoid that... sigh...
Edits: 07/09/15
.
You hadn't seen that schematic on the Magnestand webpage before this?? :)
The older version of LspCAD has trouble with series network, but the newer version is much better. However, the inherent issue with this particular schematic can't be sorted with either LspCAD version.
Dave.
Yes, I had seen that schematic before.
My version of lspCAD has no problems with series XOs - just not that one!
Regards,
Andy
Hmmmm. The new version allows to create schematics in free-form configuration, so I wouldn't expect a problem. Are you saying that Magnestand schematic is incorrect in some way? How could that possibly be? :)
Dave.
Or I don't know how to create schematics in free-form configuration?
I'm not sweating, though! ;-))
Andy
Do you know what software will successfully work with the schematic?
No, it's not correct because, as you say, the midrange driver is shorted. (It certainly won't work like that.)
Remember, this is a series crossover. :)
Keep at it.
Dave.
No it's definitely right. The only errors are of omission. I spoke with Wendell over the phone today and he assured me they cannot be bi-amped. I understand that is not strictly true, I could physically undo everything and amp it how I please, but I understand his message.
Unfortunately he didn't seem to understand biamping is less about the speaker and more about the amplifier...
Not sure what I'm going to do. I'm sure the dealer won't want them back in the condition I have one in. I think I will install them in my frames sans bi-amping for the time being, and try and work through the schematic. At some fundamental level, there is a signal present to the tweeter/mid combo and it can be recreated prior to the amp instead of after the amp.
Perhaps in this case the solution for the amp doing mids and highs is to have it do midbass as well and lighten its load with a pair of powered subwoofers at 80-100hz or so. That way you get the well integrated drivers on one moderately stretched amp while taking out the heavy lifting required for low bass.
Your translation of the Magnestand schematic into ALLXO might be correct, but that doesn't mean it will work. :)
Clearly the midrange would not be producing any sound in your ALLXO example. (That should be obvious.)
Wendell obviously doesn't want to advertise the possibility these speakers could be bi/tri-amped, but of course they can. Any speaker with individual drivers can be successfully biamped.
Dave.
That was almost useful!
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