The NRC tests show linearity problems in the tweeters but this could be due to a few different causes - thermal or mechanical issues in the driver as well as crossover issues (wrong slopes / filter points, inductor saturation, resistor temps). It's tough to draw conclusions just by looking at the front of a ribbon or AMT except for noting the dimensions of the element yields a good clue to the dispersion capability of the driver.
AMT's seem to be more prone to quality control issues which given the inherent design makes sense. I tend to prefer ribbons because of the wider dispersion in the top octaves.
AMT's seem to be more prone to quality control issues which given the inherent design makes sense. I tend to prefer ribbons because of the wider dispersion in the top octaves.
I've written to the NRC and asked for the details of their linearity test protocol, but they have not responded. It's something different from what most are doing. A browse thru my copy of Toole's book: "Sound Reproduction" didn't turn up any reference to that test; which leads me to suspect it was developed after Toole left NRC for Harman.
Here is a quote from THE speaker design guru over at PETT regarding his opinion on tweeters...
"The interesting part is that I find the RAAL to be the single most realistic sounding ribbon I have heard. I find most planars and ribbons to sound fizzy, and clearly a couple of steps behind a really good dome tweeter. This applies to a lot of the AMT's I've used too, but not all of them or all planars. Tonight I switched back and forth between the Testarossas and the Spiritwinds with their Revelator tweeters trying to see how the RAAL might be described as dull or unrealistic while playing some of my favorite jazz. I couldn't get there from here. In fact, I was enjoying it so much I contemplated that I should quit designing new speakers and just live with these two pair for the rest of my life. You and Craig are invited to try it yourselves if you like. I can throw Continuums or Kairos on for good measure, or you can bring your own."
FWIW
"The interesting part is that I find the RAAL to be the single most realistic sounding ribbon I have heard. I find most planars and ribbons to sound fizzy, and clearly a couple of steps behind a really good dome tweeter. This applies to a lot of the AMT's I've used too, but not all of them or all planars. Tonight I switched back and forth between the Testarossas and the Spiritwinds with their Revelator tweeters trying to see how the RAAL might be described as dull or unrealistic while playing some of my favorite jazz. I couldn't get there from here. In fact, I was enjoying it so much I contemplated that I should quit designing new speakers and just live with these two pair for the rest of my life. You and Craig are invited to try it yourselves if you like. I can throw Continuums or Kairos on for good measure, or you can bring your own."
FWIW
He was using mediocre amplification.
(..at least with most ribbons, unless they were just broken - which is possible.) I've heard this effect several times with different types of ribbons and planars.The worst I've heard in that regard was a demo of a Klipsch Heresy (compression driver + horn) - with a moderately-priced integrated from Kenwood in the '90s. It literally compelled me to run from the room.
Latter heard the Heresy with some "less" expensive Acoustic Research gear (..which had a much larger power supply and an output transformer), and it was a completely different experience (..better, much better). And it certainly wasn't because the lower treble was increased due to the rising Impedance.
(..same dealer, same speakers.)My guess is that Rick's Anniversario sounds amazing with a good 211 or 845 output amp (SET or Push-Pull), despite not having the impedance compensated (in the lower treble).
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Looks like a very nice speaker!
http://www.mundorf.com/PDF/Mundorf_MA30_Catalog.pdf
On the crossover it reads:
"The crossover layout is purely serial,
thus there are no parallel components
in the entire crossover. Also, the layout is
done for bi-wiring resp. bi-amping. Crossover
frequency is 3450Hz. High-pass
and low-pass are 1st. order/6dB filters,
designed as a Notch-Filter in both highpass
and low-pass filters. A Notch-Filter
is basically a band-pass filter in series
wiring, which, amongst others, helps to
eliminate peaks in the frequency response
of a loudspeaker, hence, it is for
linearization purpose. Please note: A
Notch-Filter is no response-time correction,
thus, the vertical mounting difference of
exactly 18mm (0.71“) between tweeter
and woofer must be retained with any
cabinet design"
Looks interesting, I wonder what this topology is like? here is the layout of the pcb
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRxqFQoTCKit-Ob4isgCFY6ViAodPIoMKw&url=http%3A%2F%2Fwww.diybuy.net%2Fthread-1038036-1-1.html&psig=AFQjCNFkAdNXixEwmUVJY-h6N_YL4M8Rbw&ust=1443021674003453
http://www.mundorf.com/PDF/Mundorf_MA30_Catalog.pdf
On the crossover it reads:
"The crossover layout is purely serial,
thus there are no parallel components
in the entire crossover. Also, the layout is
done for bi-wiring resp. bi-amping. Crossover
frequency is 3450Hz. High-pass
and low-pass are 1st. order/6dB filters,
designed as a Notch-Filter in both highpass
and low-pass filters. A Notch-Filter
is basically a band-pass filter in series
wiring, which, amongst others, helps to
eliminate peaks in the frequency response
of a loudspeaker, hence, it is for
linearization purpose. Please note: A
Notch-Filter is no response-time correction,
thus, the vertical mounting difference of
exactly 18mm (0.71“) between tweeter
and woofer must be retained with any
cabinet design"
Looks interesting, I wonder what this topology is like? here is the layout of the pcb
https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRxqFQoTCKit-Ob4isgCFY6ViAodPIoMKw&url=http%3A%2F%2Fwww.diybuy.net%2Fthread-1038036-1-1.html&psig=AFQjCNFkAdNXixEwmUVJY-h6N_YL4M8Rbw&ust=1443021674003453
Do a search here on 'series crossover'. There are a number of threads on the subject. Here is one example...http://www.diyaudio.com/forums/multi-way/27969-series-crossover.html
Building a new MA30 yesterday showed that although only one external set of binding posts is present, the internal crossover sections for woofer and tweeter are separate, each with dedicated wiring to the posts. Drilling an extra pair of holes into the circular rear plate and adding a pair of binding posts would allow the speaker to be bi-wired/bi-amped.
Tracing Mundorf's crossover pcb (no schematic was at hand) revealed it to be a series design, completely devoid of shunt elements other than the two drivers.
hth, jonathan
Thank you Jonathan. Being one with hands on experience with this speaker project, I accept your statements on the XO design vs those who simply speculate from afar.
If you look at the PCB you can see that WF-, TW- and IN- are all connected (i.e. all connected to common ground). This would imply a traditional parallel topology and not a serial one.
I agree on no shunt elements in cross over all components are on path from IN+ to WF+ respectively TW+.
This also explains why bi-amping/bi-wiring would indeed be possible seen from the terminals.
cph2000 said:
Not on the MA-30 crossover PCBs that I handled. WF-In and WF-Out are connected, likewise with TW-In and TW-Out. WF- and TW- are not connected on the PCB; combining the WF and TW wiring harnesses at the binding posts is what accomplishes this.
Otherwise, the passage that you quoted earlier from the Mundorf pdf appears to generally agree with the crossover PCB that I bolted into an MA-30 two days ago (haven't attempted to calculate the frequencies or simulate anything).
sreten said:
Ah. I'd forgotten how convoluted the English language can be
. Have built a few two-ways with this type of series crossover, and agree that it is incompatible with biwiring / biamping.
Coil in series with tweeter?Judging by the partially shown filter schematic and with little
imagination, I have come up with this.
The MA 30 brochure is written too optimistically. Higher sensitivity
for SE tube amps.
That uber expensive Accuton driver sure needs a lot of EQ'ing, & for all that money?