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#390263 - 02/26/13 10:14 PM Re: Customizing Axiom M80's(audio jewelry) [Re: Mad_Chesser]
dakkon Online   content
connoisseur

Registered: 02/08/04
Posts: 1806
Originally Posted By: Mad_Chesser
Quote:
the impedance changed dramatically once the the crossover was separated.


So from a technical standpoint it makes a difference?



No, it doesn't.. All an amp is, is a voltage source.... The speakers are the load... If you have an amp that is designed to be a constant voltage source, then as the impedance halves the output power doubles.

If you look at the large Krells, or Mark levensons they double in power down to .5ohms.. some even lower than that..


By Bi amping, you can buy two less powerful amps than buying one large amp.. Granted this is not the most efficient way..


A prime example of this is the Bryston Model T's as they are designed to be Tri-amped.. Each different set of speakers requires a different amp. James most likely did this because he wanted to use an active cross over to have maximum control over the frequency curves. This is slightly different than the conversation in this thread, but still loosely applicable.

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#390297 - 02/27/13 11:35 AM Re: Customizing Axiom M80's(audio jewelry) [Re: Mad_Chesser]
Mikesk Offline
frequent flier

Registered: 02/14/13
Posts: 18
First off a big thankyou to all axiomites for their inputs on this bi amping principle. I am learning a lot, and have cleared up one point of inaccuracy in my thinking as a result.My hypothetical thinking in terms of trying to do a biamp on the m80 was to do with an idea surrounding any vintage type super clean amp whose distortion characteristics went postal the minute the the resistance load dropped below 8 ohms at any point on the frrequency spectrum.If the m80's impedance vs frequency sweeps with the top and bottom of the m80 separated raised the lowest impedance above the 8 ohm threshold then get an identical amp and do a biamp,giving each amp a load it can comfortably handle.

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#390300 - 02/27/13 11:50 AM Re: Customizing Axiom M80's(audio jewelry) [Re: Socketman]
Mikesk Offline
frequent flier

Registered: 02/14/13
Posts: 18
Originally Posted By: Socketman

I found a better way of displaying my graph's for anyone who is interested.






The bottom graph is Axiom's impedance curve and it is virtually identical to the impedance graph that I generated.
Once the jumpers were removed from the speakers, I measured the impedance of the tweeter/mids and the woofers. The impedance changed dramatically once the the crossover was separated.

Sunfire amps have some interesting feature's for bi-amping. They allow you to bi-amp using either current or voltage depending on speakers and configuration. Using one of their 7 channel amps you can run it 5 channel and use the extra 2 channel to bi-amp. Each amp channel has 2 inputs so you can jump one amp channel to another with a simple patch cord.

Cary Audio has some interesting insight to bi-amping as well.


And I just got done looking at these graphs my idea is a no go.The 2 woofers in paralell with the crossover setup just put the impedance too low.Thankyou rof giong to the trouble of doing this...I can't believe by brain told my fingers to type rof instead of for.Looks like there is somethng screwy going on in MY crossover.

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#390311 - 02/27/13 03:00 PM Re: Customizing Axiom M80's(audio jewelry) [Re: JohnK]
dakkon Online   content
connoisseur

Registered: 02/08/04
Posts: 1806
Originally Posted By: JohnK
Alex, the point wasn't that the impedance would be a constant 8 ohms. A previous post appeared to suggest that a 4 ohm speaker was the result of two 8 ohm drivers connected in parallel, and that separating the wires in the manner described would increase the speaker impedance substantially above 4 ohms. It's certainly recognized that impedance isn't a constant and varies widely with frequency.

The purpose of the simplified calculations was to show the effect of the crossover circuitry on the impedance. The formula used is the basic one for calculating impedances in parallel. An 8 ohm impedance(without the crossover effect)for both drivers was selected for convenience and familiarity, not because it was a fixed value. The well-known effect of the crossover circuitry to increase the "seen" impedance of the driver not playing the particular frequency by a very large amount results in the speaker impedance(at that particular test frequency)being just slightly lower, not cut in half(two 8 ohm drivers forming a 4 ohm speaker).



ah, gotya.

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#390328 - 02/27/13 07:48 PM Re: Customizing Axiom M80's(audio jewelry) [Re: dakkon]
Mad_Chesser Offline
veteran

Registered: 01/11/13
Posts: 195
Loc: B.C., Canada
So a question I have to ask...

whether it makes a difference or not...if I had the extra money to blow on putting the feature on the speakers, does it effect the integrity of the speaker in any way? I mean, stock they come without, so getting axiom to add it, is it a big deal?

And say I have dual inputs but never use it, is there any loss of quality or performance(putting my trust in making sure there is tight connection on the jumper bars)?
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2 Axiom M80s v3
1 Axiom VP160 v3
2 Paradigm ADP-150
Pioneer SC-61
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#390335 - 02/27/13 08:45 PM Re: Customizing Axiom M80's(audio jewelry) [Re: Mad_Chesser]
Socketman Offline
connoisseur

Registered: 07/12/09
Posts: 1004
Loc: Whitehorse YT
If you didn't know it was there you would never have known that it was there. Get it for the what if scenario. I doesn't hurt anything by having it.
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DOG is GOD spelled backwards.

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#390338 - 02/27/13 09:11 PM Re: Customizing Axiom M80's(audio jewelry) [Re: Mad_Chesser]
dakkon Online   content
connoisseur

Registered: 02/08/04
Posts: 1806
Originally Posted By: Mad_Chesser
So a question I have to ask...

whether it makes a difference or not...if I had the extra money to blow on putting the feature on the speakers, does it effect the integrity of the speaker in any way? I mean, stock they come without, so getting axiom to add it, is it a big deal?

And say I have dual inputs but never use it, is there any loss of quality or performance(putting my trust in making sure there is tight connection on the jumper bars)?


the answer to both questions is, it wont make any difference... both from a materials point of view, as well as an electrical point of view. You will never hear the difference for any of the options you have asked about... Now, if you want them because you do.. Well, that is a different question, which isn't really a question...

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#390341 - 02/27/13 09:30 PM Re: Customizing Axiom M80's(audio jewelry) [Re: dakkon]
Mad_Chesser Offline
veteran

Registered: 01/11/13
Posts: 195
Loc: B.C., Canada
Thanks for all the great responses axiomites! smile

Ive got a bit of extra money I can blow...since it wont effect the integrity or performance having dual inputs...im goimg to order the feauture just because I can :p
_________________________
2 Axiom M80s v3
1 Axiom VP160 v3
2 Paradigm ADP-150
Pioneer SC-61
Rotel RMB-1095
51" Samsung Plasma

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#390343 - 02/27/13 09:50 PM Re: Customizing Axiom M80's(audio jewelry) [Re: Mad_Chesser]
MarkSJohnson Offline
shareholder in the making

Registered: 09/27/04
Posts: 10670
Loc: Central NH
Remember, too, that you don't even see the feature unless the back of your speakers are visible.
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::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::

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#390350 - 02/27/13 10:55 PM Re: Customizing Axiom M80's(audio jewelry) [Re: Mikesk]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10305
Mike, you appear to have a concern about lower speaker impedance that isn't justified by either principles of audio technology or real world experience. There's no brick wall that amplifiers run into when speaker impedance drops below some critical number. As Alex(dakkon)pointed out, amplifiers output voltage. When the voltage meets an impedance in the speaker, a certain current results(following Ohm's Law)and the product of the voltage and current is power in watts used. As the impedance gets lower with a given voltage output from the amplifier, the current gets higher and the heating effect on the amplifier increases. If this heating effect was high enough and continued long enough, the protective circuits in the amplifier would shut it down until it cooled. This just doesn't happen with typical quality receivers in the 100-150 watt range and they have no problem with M80s(as many of our members have reported)or similar speakers operating at safe(to your hearing)sound levels. As an extreme example for your information and/or amusement, I'll cite Mojo's heroic surgery done on the 2 watt amplifier in his wife's Sony boombox and resulting M80 blind listening results here .

You also seem to have partially misinterpreted Richard's(Socketman)measurement results. There's no increase in M80 impedance with the top and bottom inputs separated by removing the connecting links. As I noted previously, the high and low frequency sections of the crossover always have to be separate for there to be a crossover. The graphs in Richard's fine measurements simply are showing the different driver combinations which are being measured through the separated top and bottom terminals, with the big impedance increase a little over 2KHz reflecting the tweeter crossover(the Axiom spec is 2.3KHz) and the impedance hike above 100Hz reflecting the woofer crossover(160Hz Axiom spec). This is the way the M80 crossover works and removing the connecting links can't change it. The graphs would be the same with the links still on if the measurements were made inside the enclosure at the beginning of the crossover circuitry where the wiring normally splits for the separate crossover sections.
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