Axiom Home Page Forums General Discussion Technical Questions Customizing Axiom M80's(audio jewelry)

Lightweight, alloy wheels are actually a performance enhancement to a vehicle.

Both options are only good for re-sale to those who think they make a difference. Audio gear is anything but an investment unless you are buying McIntosh electronics - which are often collected.

If I had it to do over I'd have went with the dual imputs on my m80's.Beause the amp I am using is rated 340 watts into 4 ohms with dynamic power of 640 watts at the same 4 ohm impedance and 850 watts dynamic into 2 ohms, I felt I didn't need it.the dual imputs would have provided me with down the road amplification options.

The maximum needed on a brief peak is much more, of course, but the capacity of the amplifier's power supply section is the limiting factor, and feeding that same supply through two wires rather than one can't double the max available or increase it in any amount.

Biamping still doesn't double the power.

Can you even tell from the outside?

Yes I was thinking in terms of a future bi amp setup.On a dual input setup if you pull those gold straps out you should effectively be splitting the speaker into 2separate top and bottom speakers.If it doesn't then what is the point of them?It should also raise your impedance on both top and bottom to the point of allowing a couple of amps that want to start to clip the minute you drop the load below 8 ohms to drive them quite nicely.

Steve posted some photos in the LFR thread of the differences.

So, you want me to share in your misery eh????


Yeah, give me a bit of time, to see if i can find it :~)

Thanks for posting these pics. That logo cast into the frame is a nice touch.In regards to cast vs stamped baskets one of the questions I asked Brent was if they were altering any of the cap values in the crossover when they put the cast basketed drivers in the m80...His answer was no so I went with the steel.

Now if you have 2 amps each putting out 120 watts/ch it adds up to 240 going into the speaker in a bi or 2amp configuration.

Being a pedant, I must point out that in this configuration you now have 240 amp available to the speaker. You need to turn it up to 11 to draw all 240 amps.

OTOH. If you buy an amp capable of delivering 240 watts per channel and hook it up in a non-biamped configuration, you are in exactly the same position. You can deliver 240 amps when you turn it up to 11. Put your earplugs in first (unless this is outside on a dock and you are sitting 40+ feet from the speakers ).

PS: if I were a true pedant, I'd point out that 240 watts at the amp will not turn into 240 watts at the speakers, but that's a whole other conversation.

Being a pedant, I must point out that in this configuration you now have 240 amp available to the speaker. You need to turn it up to 11 to draw all 240 amps.

Any 2-way(or more)speaker has the high and low frequency sections separated at the latest when the signals enter the crossover. Using dual inputs with the connecting bar removed, the separation point is simply moved back from inside the enclosure to the output terminals of the receiver. This makes no electrical difference as to impedance or anything else of significance.

If two 120 watt amplifiers are connected to separate sections of a speaker, the maximum available to either section is 120 watts, not 240 watts.

But, what about tri-amping?

Any 2-way(or more)speaker has the high and low frequency sections separated at the latest when the signals enter the crossover. Using dual inputs with the connecting bar removed, the separation point is simply moved back from inside the enclosure to the output terminals of the receiver. This makes no electrical difference as to impedance or anything else of significance.

If two 120 watt amplifiers are connected to separate sections of a speaker, the maximum available to either section is 120 watts, not 240 watts.

Fred i dont think he wants to alter the impedence. Impedance is the sum of all connected parts. If only the tweeter's ,mids and associated crossover parts are seperated from the woofers ,the overall impedance seen by the amplifier would change.If someone was to run 2 wires from the same amp ,the impedance seen by the amp would remain unchanged. I will run some impedance sweeps on my M80's tonite and see what the difference is.



As can be seen here,takeing out the bridgeing would result in two seperate crossovers.

the impedance changed dramatically once the the crossover was separated.

So from a technical standpoint it makes a difference?

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.

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).

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)?

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.

Ive got a bit of extra money I can blow...