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Get familiar with the reaction system: Introducing the Reaction System
"Pinan" - a 2-way for beginners
Coming soon... Here is a teaser:
I developed these in parallel with the MCM/Vifa 2-way I just completed. These are done, all measurements taken. I am doing a very ambitious write-up, however, and it is taking me a lot longer than I expected.
I developed these in parallel with the MCM/Vifa 2-way I just completed. These are done, all measurements taken. I am doing a very ambitious write-up, however, and it is taking me a lot longer than I expected.
I have a signature.
Comments
Chuck, should be able to squeak by, but impedance may be a bit low for sissy amps.
These are in the Denovo 0.23 knockdowns, tuned with a pair of PE 1" ports. I corner loaded the ports to try and extend the tuning down a bit more.
Both drivers are surface mounted, with the backside of the woofer cutout chamfered.
Tweeter response on baffle:
Woofer response on baffle:
Tweeter is a little rough, but offers pretty low distortion otherwise. The dip fills in off-axis, so no sense in trying to figure out a way to fill it in using a high Q crossover.
Modeled response:
Measured response:
Distortion, SPL accurate, 1M:
Areas to improve would be suppressing the top end of the woofer a little more, but I have a long game in mind here. I want to see how much of a drop-in the revised model of this woofer will be. With the addition of a shorting ring, I am guessing that will result in a drop in distortion in that area.
Measured on-axis, reverse null, and impedance:
Impedance shows the ~55Hz tuning, and phase stays within +/-40 degrees. Easy to drive for pretty much any amplifier out there - important when designing towards beginners.
Both channels overlaid:
Red/Yellow is sample one, silver/pink is sample two. I'll take this from less than $80 worth of drivers.
Horizontal response:
I'll take that, as well.
Crossover:
Five components? OK! Woofer is S1, tweeter is S2.
Baffle is easy - woofer is 3-3/4" from the bottom and the tweeter is 8-1/2" from the bottom. Cabinet dimensions are available on the PE website.
Crossover cart via PE:
I think I oopsed a 5 instead of 5.6 ohm resistor, but it is such a serious pain in the peehole to put together shopping carts on PE that I elected to use the error version I created.
Those new crossover boards from PE are pretty cool:
I used parts from my extensive collection to build these, but I do recommend the Audyn caps from PE whole heartedly. FYI, that is the assembled, soldered and glued crossover. Pretty slick results with those bakelite breadboards.
...and some driver porn:
I think anyone who has used or heard these woofers understands what a special value they are. This design is no different. They are exceptional midbasses and offer above average performance in the upper mids. I suspect the addition of the shorting ring will elevate them into serious contender for "best cheap driver ever". I love these little woofers!
The room and reflections will do more to it before getting to your ears than the dip itself anyway.
Also, yes - this tweeter is a prime example of why taking real measurements is so critical. Without knowing it fills in off-axis, one may be tempted to try and fill it in somehow. The simulators cannot properly predict off-axis behavior of a driver - IMHO that is where they fall "flat", if I may be allowed a small pun.
Nick, want them over Christmas?
I know why, too. When I was doing initial voicing, testing, and listening I was doing so with them toed in, directly on-axis.
In normal listening, however, this off-axis behavior impacts things:
A substantial loss of energy above 3K occurs (given the high crossover point, essentially the entire output of the tweeter), so to avoid the "head in a vice sweet spot", raising the top end a bit more may be needed. When I toed them in and sat her in the sweet spot, she said they "came to life".
As I generally voice towards little to no toe in, I am going to raise the tweeter level a few db. Doing so will require nothing more than paralleling a 6.8ohm resistor across the existing series resistor, preserving the option for both levels to exist.
That being said, these little woofers are blowing me away with the bass reproduction. I have always been impressed with them in that regards, but dang. I wasn't kidding about the "not needing a subwoofer" comment.
Looking at the 45 degree plot, these tweeters would work well 2nd order LR at 2K on a custom, angled baffle.
Just got over a 101 feaver and virus myself. Inly 50%, but good enough to be back at work.
Hope the fam feels better.
I agree with Nick's impressions, especially as regards the bass output. These little woofers are something special in that regards, and objectively I can help explain why (to an extent). The basket is very open, allowing a lot of air flow around the back side. Additionally, cast aluminum baskets (and I am digging deep into something I read years ago) affect the magnetic field differently than do steel baskets, and saturation is more focused (some semantic deviation in that statement maybe?). This allows the motor to be effectively stronger, and is why not a single high-end driver uses anything but cast aluminum. The strength is a secondary benefit.
The suspension is also a key contributor. The surround is the effective excursion limiter - meaning it will arrest cone motion before it hammers the voice coil into the back plate. Looking at the Dayton Ultimax 8", the stopping point on that driver is actually the edge of the cone, which will strike the basket - ugh. Most drivers, when pressing hard on the cone, you will find you are able to bottom it out against the backplate. While doing so, look at how the surround behaves - a lot of drivers will exhibit deformation of the surround when doing this, so you are introducing progressively worse non-linear distortion as you approach Xmax - this is what Klippel is all about, exposing those non-linearities based on excursion. This driver, or at least all of the samples I have tested (14 to date) exhibit high linearity up to the point of the surround acting as a progressive shock absorber. Every sample I tested, the surround stayed linear through the entire mechanical movement of the cone. I recently tested a similarly priced HiVi F5 that has, at best, 1mm of throw before the surround begins to deform. Witnesses to the now legendary "Barbie Girl" demo will attest to the civilized manner in which this driver hits its limits. This is largely thanks to the high-end behavior of the soft parts. To my knowledge, the entire Dayton RS line, for example, is capable of jumping the gap and damaging the cone. It is my opinion that you will fry the voice coil on these long before you can mechanically damage them - but again, excellent driver design intervenes and the (relatively) high sensitivity of this driver allows it to play very loud on a (relatively) low input voltage. A full BSC bookshelf such as Pinan still has over 82db of actual sensitivity. While that may not seem like a lot, a typical hi-fi 5" bookshelf that will play to 50Hz or lower will average maybe 77 when implementing full BSC. That is the difference between a Lepai and an APA150 for similar drive levels. That cannot be dismissed lightly; this is a high output 5" 2-way that offers real, quality bass into the 50Hz and below region.
Thanks to the well-designed moving parts, extremely strong motor, and (getting to this next) the nearly perfectly designed cone - this driver never exhibits the "uglies" as it approaches excursion limits. Period. It does not go into fart mode, it does not slap the backplate, it simply compresses in a progressive manner and recovers remarkably fast. The extensive cooling around the voice coil (the former is vented, extensive venting under the spider, a massive motor, and even a cute little back plate vent) means thermal compression and noise related to cone excursion is simply a non-issue. It plays loud, and compression occurs of course, but it is graceful as compared to the DSA175, for example. That driver plays loud for awhile, but due to the lack of adequate venting, it gets hot and goes into shit mode until you cool it down. It will also hammer the backplate quite alarmingly. When Nick and I were torture testing my DSA design one afternoon, we got the cones pretty hot.
The cone on the MCM is nearly perfect. Curvilinear in shape, and very stiff. Most importantly - a treated fabric dustcap. Is the cone to everyone's liking? No - although I think the pearlescent nature of the anodizing is quite beautiful, even I think the fabric dustcap is kind of... cheap and moderately ugly. However, it does a tremendous job of damping the cone breakup and I suspect it transfers heat really well. Back in the day, before driver manufactures figured out this whole "under spider and out the back plate" thing, a breathable dustcap was a very common cooling feature. I doubt this is fully functional in that regards, but it would not surprise me if, under compression, it becomes breathable.
Essentially, what we have is a sub-$20 driver that behaves like a $100 driver in most aspects. It is not the cleanest in the upper mids, but otherwise it is an unbelievable performer. Here is where things are going to get real - MCM has had a slight redesign on this bad boy and the next generation will have a black anodized cone, and a copper cap on the pole piece. The black will address some of the common aesthetic complaints, and the copper will help drive the distortion in the upper mids into that -50db territory, or better. The prelimary data sheet I have seen indicate it is otherwise going to be a drop in for existing designs. This is an exciting development, to say the least.
I said I would keep my subjective opinions on this design to a minimum, but I really think this design is one of a handful of under-$200 bookshelves that sets a standard. It plays louder and louder and handles it all with excellent transients, clarity and - dare I say? Excitement. Yes, I said it - this is a design that will have the end user reaching for the volume knob just to see how it will do on a variety of genres. When the revised drivers hit the shelves, I am going to buy them right away and do some testing on their suitability as drop-in replacements.
So anyways, the MCM 55-2669 is a world-class midbass and with the next iteration sporting a shorting ring, I suspect it will also be very competitive as a dedicated midrange. Who doesn't like the thought of a 89db, 8 ohm 5" midrange with build quality like this?
This isnt the other place. Subjective reviews based on observations that make sense, and are real key contributors to a drivers performance are greatly appriciated.
I found that woven fiber MCM 6.5" I fell in love with to exhibit the same type of cone behavior being surround-limited. The basket was stamped, but thick, and the pole had a hole.
I fell out of love with the Dayton RS after seeing multiple units bend the cone and seperate from the coil in a bloody mess. I have also seen them burn up easily. They simply do not shead heat.
They appeal to the "world is flat" group and measure good enough, but they will not handle programme.
The RS subs are good if you can get a couple that have passed QC.
Many of the very reasons you have stated is why I turn to Scan or Seas in my higher end woofer applications. Even some high end mfgs (some I will never understand the populus affinity for) cannot seem to understand these fundementals at times.
Thanks for the details. I have something with the old round-frame 2669 in process. Ill get details when done....Been a long time coming. Started it about 4 years ago and shelved it out of distraction and frustration on the cabinet finish, they will make a nice gift though so I want to finish them up.
Mike, would you elaborate on some of the other high end mfg and specific drivers models?. I understand, not all the drivers in a mfgs basket are bad, but some definitely are...
Sadly, as often as it is proven otherwise, pricetag is still the number one most trusted criteria for the impression people have about any given product, followed closely by popularity. I see this across manufacturing - quite discouraging when you know there are better, more powerful PLC's at better prices but the industry defaults to Brand AB because of proliferation.
Wine, speakers, cars - you name it, there are confirmation biases abounding. American cars are no less reliable than their German/Japanese counterparts these days - but tell that to someone who paid a lot of money for a used Honda "because a used American car is going to let me down".
So hopefully, giving people some basic tools to help visually determine some of the features that can point you in the right direction for selecting the right driver will help deter some of the price tag emphasis.