A little graph i found which nicely explains a few things although for the frequencies involved it must be of a woofer
Just to show that when i waffle on about impedance of drivers and when wired in series or parallel i am talking about the nominal or rated impedance as shown on the above graph. Because music is an AC signal and the voice coil of a driver is reactive the impedance changes with frequency. Put a multimeter across a driver and all you are measuring is the DC resistance . The nominal / rated impedance of the driver is quoted as a little higher than this.
Just for Tomasz here we have a pic of the very attractive enclosure i have made for the open back full range driver i added to the out facing side of each little cab. Made from the finest black gaffer (gaffa?) tape. EDIT TO ADD - the tiny full range driver is not run full range, it is after the 1.65uf capacitor like the rest of the tweeters so is in effect a tweeter.
I managed to make it air tight and slope it away from the driver as to smooth out diffraction a little. Put some on the edges of the MS902 tweeter on the inner faces of the speaker as well.
Some quotes from elsewhere (a guitar forum) . Could be true or could be
"An amp with good damping (e.g. solid-state HiFi amp or something along those lines) is virtually immune to effects of load's resistance changing and will not portray any significant differences in parallel vs. series setups."
I would like to believe the quote above
"Since resonant frequencies or inductive properties of different kinds of speakers are hardly ever the same one can easily figure out what happens when two or more such impedances are connected together either in series or in parallel. We are effectively summing "curves" instead of fixed resistance values. So yes, a parallel wiring tends to level out differences in impedances while series wiring tends to "accentuate" them"
"Compared with and 8 ohm speaker, a 16 ohm speaker requires that the amplifier put out twice the VOLTS for a given power, because it draws half the amps. Solid state amps are limited by the volts they can output...within reason (and until a fuse pops) they can hold up this voltage regardless of the current drawn. Thus their wattage rating increases for lower impedance speakers. Tubes have high voltage capability, but can output little current, therefore tubes are usually interfaced using a step-down transformer which trades off voltage for current. This transformer has different taps (connection points) on its secondary winding so as to match different speaker impedances, so that the amp will work equally well with any impedance."
Another(about wiring a 50 ohm resistor across a tweeter)
"I have also seen commercial speakers with metal tweeters where a 50 ohm 1 watt metal film is shunted across the tweeter"
"Nope- that's not the purpose at all. When you take into account the varying impedance of the tweeter against that 50 ohm resistor, all of the measurement points across the Z plot get paralleled with the 50 ohms.
My guess for this resistor usage, as I've done it for this purpose, is to minimize the effective Fs magnitude as it should do. 50 in parallel with a 25 ohm Zmax nets a new Zmax just below 17 ohms, but 50||4 = 3.7 ohms; or a minimal change."
I have never heard so much texture to the bass, synth's, vocals and strings as i am doing now. It is a beautiful album and sounding so moving and emotional now. Multiple hair standing up moments.
More quote. Bit boring for any non technical viewers....sorry
"Inductance plays a major role in driver transient response, linearity, and bandwidth.
Cone speed and mechanical settling time play a major role in driver-to-driver integration throughout the crossover region.
Sd * BL / (Mms* Zmax) is a reasonable figure of merit, where the Zmax includes the inductance at the maximum use frequency
There are reasons to use lighter, lower-mass woofer cones and low inductance motors. Smaller or lighter woofers don’t make faster bass, but they do reproduce higher frequencies than larger or heavier woofers can reproduce, and this is an important consideration for integrate between drivers throughout their overlap region. This overlap region is critical to our perception of bass speed that there is little or no tolerance for error. The null tolerance for integration error extends to phase, amplitude, frequency, and time. Introduce even slight variations between any part of the overlap region and you get audible effects in the bass or midbass.
Our perception of bass speed is mainly a function of how ideally the midrange and woofer are integrated. Bass linearity is greatly involved also; you may see a flat frequency-response curve, but the speaker can still sound like it has lumpy bass response because of less-than-ideal phase relationships between the midrange driver and woofer. Phase can often change with frequency. The woofer and midrange drivers can actually veer off in different directions, phase-wise. Large dynamic drivers operating at the top of their range and medium-sized dynamic drivers operating at the bottom of their range can often diverge significantly in their phase response. When phase or other transient errors happen, you get comb-filtering effects. This comb filtering results in the complex response of the loudspeaker to music being quite different than the response of the speaker when the input is something simple like the sine-wave sweep used to measure "frequency response."
To avoid comb-filtering effects that cause beating reinforcement and cancellation effects in the sound, it is imperative for the phase, time domain, amplitude and frequency performance of the woofer and midrange driver to be aligned. Get the midrange or woofer a little ahead of or behind the other driver, and comb filtering starts. Even small errors show up as speed problems in the bass or midbass. Bass detail is also mainly driver integration and not the quality of the woofer itself. Bass detail comes from the midrange driver, but your ear/brain is so completely fooled by this complex interaction of midrange and bass sound that you believe that it is strictly bass-related."
"Loudspeakers are one of the nastiest, reactive loads you can place on an amplifier. And nearly every amplifier made today has global feedback right on its output ... so all the load caused foibles are introduced back into the amplifier ... which is my opinion, functions as an active distortion generator as a result. I'm convinced that this is the major cause of active distortion in music playback today. Lowering source impedance, and fancy speaker wires do not correct phase shifts and other problems in the loudspeaker."
And the reply
"wrong - no one with actual engineering understanding of audio power amps, feedback theory, global feedback is going to talk about the issues this way
this is straight out of the 1970's-80's - repeated "theories" put forth to build egotistical Audio Guru's names, then analysis, peer reviewed replies, with hardware tests, real measurements showing the "theory" is vapor - effects in the noise with "conventional engineering" practice
you can search the AES eLibray for “interface distortion” or interface IMD as a directly relevant example of buzzword invention, self promotion, over issues covered by engineering textbooks for decades preceding"
"This somewhat of a side-topic, but I've been wondering lately if there was any way to "trick" an infinite baffle subwoofer driver (like this one from PE... http://www.parts-express.com/pe/psho...55&ctab=1#Tabs) to think that it was in a very large enclosure by building a smaller, yet very leaky, well damped, enclosure? I guess the biggest issue is that if it is too leaky that lowest bass notes may "escape" and cancel with the direct sound from the driver like a dipole design. This is just a thought that I haven't looked into thoroughly and it seems like there have to be a lot of issues that would make it less optimal than using the driver in an actual extra-large sealed enclosure (or IB application) that it was designed for."
Later in thread ....
"I did some quick research regarding my post of using a smaller, leaky enclosure with an IB subwoofer driver. It seems that by making the cabinet more "leaky" you really don't get the types of gains that I was hoping. For a high Q design, all that making the cabinet more leaky does is reduce the output near the high Q peak but doesn't change the overall Q of the design like using a larger cabinet would (which would lower the f3 and extend the bass with a shallower rolloff slope for part of the response)."
"It should be noted that Dynaudio woofers of that era (e.g., 30W54) were perfect candidates for isobaric loading- high Vas, low fs, moderate Qts. Dynaudio did some very cool tricks which I haven't seen anyone else duplicate. First, the isobaric was asymmetrical- the inner woofer was different than the outer. Second, they rolled off the inner woofer acoustically by having it fire through a Variovent. Third, they had a moderate volume and distance between the two drivers. Super, super clean bass, the best I've ever heard to this day."
i found which nicely explains a few things although for the frequencies involved it must be of a woofer
driver i added to the out facing side of each little cab. Made from the finest black gaffer (gaffa?) tape. EDIT TO ADD - the tiny full range driver is not run full range, it is after the 1.65uf capacitor like the rest of the tweeters so is in effect a tweeter.
Multiple hair standing up moments.