Axiom Home Page Forums General Discussion Technical Questions Why no HP Tweeters or midrange?

I think I already know the answer, but I’d like to hear for sure. Why only HP for woofer sections?

The obvious answer is the bass sections / woofers take the most power / can handle the most power, to create low frequency sounds so a higher capacity for more input /output makes sense. So if I hypothetically choose HP and put a very high powered amplifier in use (say something huge like a one channel ADA 1500) to utilize the HP capabilities of the bigger voice coils and excursion , why do my midranges and tweeters not also “HP” to account for the higher power I’m hypothetically using? Or are they already just naturally capable? Or maybe I just understand the application of HP Woofers?

I think I’ve described that right…let’s see where this goes, maybe I can ask it a different way if needed.

Thanks,
Kodiak.

The HP woofer is more linear at higher SPL over its operating frequency range than the standard woofer. But the standard woofer has a larger operating frequency range right into the upper mid-range. It is why you see an M3 with a standard woofer and no HP option. The reason for this has to do with the higher mass of the coil that drives the HP cone. That higher mass is due to more wire. More wire, more inductance. More inductance, more impedance at higher frequencies. Hence the HP driver is limited to about 250Hz whereas the standard driver goes up to 2200 Hz.

So now you get the picture. An HP mid-woofer would not have the frequency range of the current mid-woofer. That means twin mid-woofers would be needed; one for lower mids and another for higher mids. It's not wrong but it's a higher manufacturing cost to produce two mid-woofer types. There's a sensitivity penalty as well with that design. Axiom opts to use multiple mids, of the same type, to achieve higher SPL. Ditto for the tweeter.

Using multiple drivers within the same frequency range isn't a trivial design exercise because the designer has to understand how they interfere with each other and resolve audible resonant peaks and dips. And the designer has to understand what the root causes of the resonances are - cabinet, driver or cross-over.

It's why an M2 acoustically disappears in more room positions than an M100 does. The M2 is less prone to position error because it exhibits fewer and lower intensity acoustic resonances than the M100. This is the result of fewer drivers leading to better driver integration, smaller and more inert cabinet and a simple cross-over.

The drawback is that the M2 cannot achieve the frequency range, SPL and image size of the M100. But if you use the M2 with a sub, and you're not sitting too far away, the M2 just might be more pleasing to you than the M100. In fact, the M100 might frustrate the hell out of you because it's bass might over-load your room!

The M2 is a killer product. It's a highly versatile, low cost, small footprint, hi-fi speaker. It's perfectly designed for its range. The M3 tries to be too much and as a result, it's compromised in the mids and the bass can be too bloomy in some rooms. But these aspects also make the M3 sound warm.

Thanks Mojo. I knew I could count on you for a great explanation!

So in theory , with the HP bass section compared to a regular version of the same speaker we should be able to hear the difference , say in a blind listen test? The midrange is also being asked to do more of the bandwidth too, a 1000 hz more. Obviously it can handle it but does adding that extra 1000hz change how the midrange sounds as it’s handling more ? ( less linear?)Not sure if I remember correctly, but the midrange is naturally attenuated anyway?

I think the HP sounds like a good idea for a full range speaker in terms of a single pair to do it all. No subs needed. Or are there advantages to non hp and pairing with subs for better control as you eluded to there with the m2 but I’m thinking of non HP towers with subs).

( I think at some point here I’ll just grab a pair of m2 and bloody try it out ! Too busy right now though.)

Thanks again for the education.

With regard to the blind listen test, I can't give you facts because I've never compared the same speaker with and without HP but I can give you a reasoned opinion.

Axiom didn't introduce a three-way bookshelf until the HP driver was ready. We can speculate why. Maybe all the products in the Millenia line were doing just dandy and there was no market share to capture with a 3-way. Maybe Axiom felt a 3-way would be too big, confusing prospects who couldn't identify with a speaker that was too big for a bookshelf and too small for a floor-stander. That doesn't sound like Ian though. More likely, the standard woofer just didn't have the 'nads to keep up with the mid and tweeter. This is why the M60 has dual standard woofers. Once the puny, standard woofer problem was solved with the HP, the M5 and QS10 were born.

Now we can ask which is better? The M60 or M5? I don't know. I've never listened to an M60v4. What I do know is Ian prefers the M60 to the M5 because the M60 is more sensitive and hence easier to drive. Based on the published curves, the M60 is more linear too. Does it disappear as well as the M5? I don't know but the M5 is quite inert and small enough not to get in its own way, resulting in acoustic holography. And the M5 gives the warmth the M2 is missing but you have to be careful with room and placement because the warmth can become bloat. Note the M5 has a similar bump as the M3 down low. It's like Axiom decided to blend the best of the M2 and M3.

So the last paragraph tells us that dual standard woofers can do what one HP driver does with higher sensitivity to boot. But that requires a larger cabinet which comes with its own set of acoustic resonance problems. You gotta know which peaks and dips matter and which don't. If you don't know how to deal with that, you end up with a $50,000 3-way that is made of lead and lined inside and outside with no-rez.

As for the mid having a wider bandwidth, it doesn't matter until you start to ask for more SPL. Then you just add another mid-woofer like the M80, M100 and QS10 have.

You don't need a sub with the M5 for music but it sounds so much more emotionally satisfying with a sub!