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Minimus 7 Loudspeakers - Measurements

Pete B said:
Don't like the dip to 6 ohms with the 30 ohm resistor, I'd probably make it 50 ohms or so, allowing the max to go as high as 16 ohms, then adjust the 1.5 ohm to maintain the correct tweeter level.
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Thanks, Pete. I'll try 40 Ohms parallel and 2 Ohms series; that's the max available resistance in PE's inexpensive non-inductive wirewounds. :thmbsp:

Stock, they drop to 7 Ohms at 250 Hz, and 5 Ohms between 5 kHz and 10 kHz.... :yes:

Edit: PZ-2.1

Zmax = 16.01 Ohms at Fc = 119.53 Hz
Zminlo = 6.32 Ohms at 285.59 Hz
Zminhi = 7.58 Ohms at 12.210 kHz

Note: L1 DCR = 0.17 Ohms.

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Wow, 7 mods to choose from. Since I don't know enough to interpret the impedance graph in post #114, I presume PZ-2.1 is the "preferred alternative" at this juncture. The FR graph in that same post looks to be the flattest overall.
 
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Robie said:
Wow, 7 mods to choose from. I presume PZ-2.1 is the "preferred alternative" at this juncture.
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Yes, PZ-2.1 is the "best result" thus far.

It becomes a matter of statistics at this point, i.e., mod a bunch, measure the results, and see if the circuit is optimum for all of them.... :dunno:
 
Pete B said:
Am I reading that right as 5 ohms for R2 in PB-1?
I stated here 2-4 ohms, but not 5, depending on taste:
http://www.audiokarma.org/forums/showpost.php?p=2355102&postcount=75

We should also probably note that they are all wired with the drivers in phase.
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Thanks for pointing that out, Pete. The values in the schematics reflect those actually used to generate the posted measurement results.

The summary curves at #114 are all remeasures with the grille in place.

Disclaimer: Where appropriate, attenuation was adjusted to produce the flattest response and/or the overall balance most pleasing to the experimenter.... ;)
 
After seeing what you and Pete came up with, I move that you take mine out of there. It's bringing down the average.

Without a speaker to play with I had no idea how much driver interaction there was around the XO so I've got that hump in the midrange. I'll bet a Celine Dion or Barbara Streisand tune could part your hair with that. Seeing what it looks like with both drivers playing I'd probably pull the LPF down a whole bunch.

Ray
 
RayW said:
After seeing what you and Pete came up with, I move that you take mine out of there. It's bringing down the average.
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Not gonna happen, Ray. Your work was the baseline for the achievable HF response, and substantial inspiration to pursue it further:

"The thrill is BACK," I observed at the time.... :thmbsp:
 
Zilch-- In the PZ-2.1 ,who sells the L2 inductors, did not see that value and DCR in the PE catalog??
 
It reuses the inductor in the stock Minimus.

Otherwise, use the 20 Ga. aircore, PE# 255-032, or smaller from another source, if desired.
 
Tour de force

Zilch said:
Yes, PZ-2.1 is the "best result" thus far.

It becomes a matter of statistics at this point, i.e., mod a bunch, measure the results, and see if the circuit is optimum for all of them.... :dunno:
Click to expand...

Beautiful job, Zilch. I will try this mod.
:thmbsp:
 
Zilch,

Excellent job and thank you for posting your measurements and the new PZ 2.1 schematic. Is the L2 .4 mH stock inductor ok or should one spend a little more $$ and go for the PE Jantzens you mentioned?

PeteB mentioned something about stuffing them...any thoughts on that?

As I posted in the other Minimus thread, the NY, NY 90's moder used some clay material to deaden the cabinets and doped the woofers...any thoughts on that?

Thank you again for your assistance,
L

fourwheel0,

Those RCA speakers are just rebadged RS speakers. This happened when RCA and RS got into bed with one another and signed all sorts of licensing and collaboration agreements. From your pictures, the ones you have have the Lineaum Tweeters. Nice ones!

L
 
The inductor in the Minimus 7 is rather a nice air core, actually; too bad they glued that little guy in there, as it almost necessitates working with the stock input terminal assembly. I'd like to start from scratch with the installation detail, but the additional expense associated with doing that may not be justifiable to some owners, so I'm working with using what's there for now.... :yes:
 
Zilch said:
Thanks for pointing that out, Pete. The values in the schematics reflect those actually used to generate the posted measurement results.

The summary curves at #114 are all remeasures with the grille in place.

Disclaimer: Where appropriate, attenuation was adjusted to produce the flattest response and/or the overall balance most pleasing to the experimenter.... ;)
Click to expand...

OK, well we'll probably come up with something better than the PB-1 but if anyone wants to build what I actually tested I suggest starting with 3 ohms and adjusting from there if at all.
 
Pondering the 3.8 K peak in the tweeter response. Was going to mention that it is probably cabinet edge diffraction since it is well above the fundamental resonance yet low enough to most likely not be a dome resonance. There is no chamber or vent tube to cause it.

The high Qts indicates that there should be a large peak at Fs, but Fs is well into the stop band and there seems to be enough attenuation so that it does not show up.

It would take more measurements to come to some firm conclusions.
 
I received the tweeter mount plate from member Oldskl today, and the Tang Band 25-1166S (PE# 264-834) seems to fit, mechanically, at least, on first look.

I have little desire to get into redesigning the Minimus 7, though. The purpose here is to document and evaluate the available crossover options, and maybe come up with something more optimal.

We're in the $30 range with the crossover upgrade, and while it may be worthwhile to also investigate a replacement driver or two, I don't think there's much enthusiasm to be generated for an additional $40 (per pair) in tweeter upgrade costs.
 
Pete B said:
Pondering the 3.8 K peak in the tweeter response.
Click to expand...

That'd be about right for the tweeter-to-edge distance (doing rough calcs in my head). Have you tried putting felt or something similar around the tweeter to eat up the waves travelling along the baffle? Might help smooth that out.

Ray
 
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