I thought I should address the comment by gtpsuper about the M60 5.25” mid-woofer breaking up at high output levels due to there being no high pass crossover used on this component. I don’t believe that gtpsuper has any first-hand experience with this, please accept my apologies if this summation is inaccurate, but rather I think he is regurgitating a comment originally made by Gene at Audioholics. Anyway, in light of this comment I ran a few measurements on the M60 5.25” mid-woofer (graphs below). As can be seen from the graphs there is no compression occurring nor is there any undue rise in harmonic distortion from this component taking the M60 all the way up to 110 dB through the frequency range in question. Going much above these levels would only start to strain the tweeter. The 5.25” mid-woofer is in its own very small enclosure inside the M60 cabinet. There is no need for a high pass crossover on this component: in fact it would be detrimental to the performance of an M60. The limiting factor to the maximum output of an M60 is not in any way related to the 5.25” mid-woofer. It is the single tweeter that will be the first component to show signs of strain as you near the maximum output of the M60. This is the case with most loudspeakers on the market: the single tweeter is the limiting factor.
For people to claim they can hear certain things based on a prior knowledge that goes against a particular theory they hold as true is not unusual: in fact, it is simply human. I don’t think that Gene was being malicious in his comment about being able to hear strain caused by the 5.25” woofer not having a high pass filter; he was just being human. This psychological phenomenon has been proven over and over again and is the reason for Double Blind Testing.
Since we are on the topic of Gene and Audioholics I would like to take a moment to discuss the bad blood that has been happening between Axiom and Audioholics as of late. Firstly, I am pretty sure I am the reason for the bad blood and for that I am regretful. Since the opening of the Audioholics store I have been a bit conflicted. On the one hand Gene and I have had a longstanding and generally fun -- ok very fun -- and respectful relationship as a magazine/manufacturer. On the other hand I was nagged by the fact that I didn’t really feel comfortable sending money and product to someone we were competing with in the marketplace. I sense that when this finally came to a head that I left Gene with the impression that the core problem was that I didn’t think he could be objective and unbiased in his dual role. This is not the case, it is not even relevant to my decision, but I do sense it ended up being the impression that was left, which raised his ire.
I learned a long time ago to never start making character judgements of people with a bag of acoustical measurements as your evidence. We must remember that no matter whether we are talking about competitors, magazine editors, or passionate consumers, that we are all trying to move forward the notion that great audio is a very fulfilling part of life. This is all good and as much as we may beat each other up from time to time over one nuance or another regarding product design or general theory regarding what we can or cannot hear, we are all in the pursuit of this passion together and we all would like to see more and more people enjoying a great sound experience. Hopefully Gene and I can find a more comfortable zone in the future. I know that I miss our chats, both the agreements and the disagreements, about audio over some good wine and good food.
At Axiom we are very focused on making amazing-sounding audio equipment and doing it without wasting our customers’ money. You could call it a ‘niche approach to the marketplace’, as CatBrat eloquently called it in his post. But it really means that our research is focused not just on what makes an improvement to our products - though that it is the main point of it - but also on what does not make an improvement, and should therefore not be included in our products. To put a finer point on this design goal, it means the “improvement” must be audible using our Double Blind Listening methodology. Lots of things are measurable but not audible; these features are put under intense review since their automatic inclusion based solely on the measurement would fall under the umbrella of wasting our customers’ money which goes against one of our most basic design goals. When it is audible but not measureable we endeavour to find out how to measure it. Then there are the measurable things that do not manifest themselves as one may initially think in the audibility domain and these can open new roads. All this continuously furthers the Axiom ethos of always producing and improving our products to have exceptionally high value, at least for those who value both their sound experience and their money.
To answer JBall while we are on the topic of the 5.25” mid-woofer in the M60: as explained above, it is not possible that this component is running out of steam as you turn up your amplifier with the M60s set to large. The more likely scenario is that your amplifier is going into clipping and therefore resetting the M60s to small is alleviating that clipping.
In case you are wondering about the sweeps getting choppy below 70 Hz (150 Hz for the lowest THD curve) it is because we are running up against the rising noise floor of the anechoic chamber below that frequency. The filters LMS utilizes when measuring THD do not allow for accurate resolution of the THD much below 1%. Since THD below 1% is not relevant for this purpose using LMS has the benefit of an easy-to-read presentation of the graphs.