I'll try that yet tonight, Ray. Minimus 7 is still on the test stand while I work out the crossover installation details here.... :yes:
Minimus 7 Loudspeakers - Measurements
- Thread starter Zilch
- Start date
Hi Ray,
I had the same thought to try felt or some damping material but this was just a quick fix one weekend many months ago and my Minimus 7s are put away at this point. I have some woofers to try, and will probably see what I can do to further refine the mod.
General question, or for the mods:
I have an engineering client that has surplus woofers that will fit the Minimus 7. Is it legal to post a link here? I make no financial gain from any sales of them.
I think we can sum up zilch in two emoticons;
:scratch2:
and
:yes:
nothing wrong with that tho'
The foam's ~1/8" thick, and somewhat uncontrolled, just held on with tape.
If the tweeter plate were coated instead, there might be a better result.
Also, thicker reticulated foam on the inside of the grille might be an option worth pursuing.... :scratch2:
If the tweeter plate were coated instead, there might be a better result.
Also, thicker reticulated foam on the inside of the grille might be an option worth pursuing.... :scratch2:
Do they have foam surrounds around the tweeter?
This makes sense.
Here's the link; I measured the T&S parameters that are listed but we've not done further measurements or listened to them in a system. I measured them for my own potential use in the future:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=120337864835&ssPageName=STRK:MESE:IT
General comments:
For now I'd say that they're a low cost (shipping is a bit high ask them to combine shipping) option that might interest some who just want to get their speakers working again. Note that they are 4 ohm as compared to 8 for the originals. They'll make the system 4 ohms and there is no crossover issue with the stock design since the woofer is wired directly. Not for use with the mods under discussion here.
In system Fc for this woofer measured at 122 Hz with a Qtc of 1.5 as compared to the original 117 Hz and Qtc = .74. This woofer is going to have some peaking in the response above resonance which is similar to baffle step compensation. It is obviously not an exact replacement.
Sir.Byrd
Lunatic Member
No... fine, maybe this are second gen. the ones that have no ring around the tweeter but they have the spring clips rather than the screw terminals.
So, does this mean you could modify the stock crossovers to PZ-2.1 to obtain the best results so far, or would you have to build a totally new crossover using the stock inductors?
Not clear on this...
In addition to that inductor, all there is to the stock crossover is an additional 4.7uF NPE capacitor, which is not reused, so there is essentially nothing to modify. There's no crossover per se in the stock Minimus 7, only a two-pole highpass on the tweeter....
Sorry to be so slow on this, but then you are building crossovers but reusing the inductors, right?
Thanks Zilch
Yes, precisely.... :yes:
Thanks!!
Note here that the PB-1 mod does not have the sag from 5 to 7 kHz,
3rd figure down violet curve vs. lt. blue:
http://www.audiokarma.org/forums/showpost.php?p=2356943&postcount=88
3rd figure down violet curve vs. lt. blue:
http://www.audiokarma.org/forums/showpost.php?p=2356943&postcount=88
Indeed, you can clearly see how I pulled the peak at 3.9 kHz down differentially to optimize the overall curve via selecting different component values.
The result also changed when the grille went back on, flattening that sag.... :yes:
laserman
Ambiguous Optimist
Okay, the PZ 2.1 mod is the direction I will go in.
As far as the foam on the tweeter baffle...has anyone attempted to use something of more substance like nonsynthetic felt , i.e. wool? Would it net different results than the foam? The reason I ask is because I have seen felt used in other speaker designs as a means to control edge defraction.
Stuffing - anyone care to comment on what to stuff them with and how if in fact they need to be stuffed?
Cabinet - anyone care to comment on what to use to dampen the metal cabinet or is it a nonissue?
Thanks for everyone's input to this mini-mod.
OBTW, I have been following the Econowave project with an area friend and we may tackle that one too. I find NE Winter days go by much faster when you establish projects to accomplish.
Most appreciative,
L
As far as the foam on the tweeter baffle...has anyone attempted to use something of more substance like nonsynthetic felt , i.e. wool? Would it net different results than the foam? The reason I ask is because I have seen felt used in other speaker designs as a means to control edge defraction.
Stuffing - anyone care to comment on what to stuff them with and how if in fact they need to be stuffed?
Cabinet - anyone care to comment on what to use to dampen the metal cabinet or is it a nonissue?
Thanks for everyone's input to this mini-mod.
OBTW, I have been following the Econowave project with an area friend and we may tackle that one too. I find NE Winter days go by much faster when you establish projects to accomplish.
Most appreciative,
L
The grille only improves the 5 to 7 K sag by about 1 dB as can be seen here, and there is a loss of even more above 10 K with the grille:
http://www.audiokarma.org/forums/showpost.php?p=2374563&postcount=145
My original PB-1 mod was designed to provide flat response in the tweeter passband, ignoring the 3.8 K peak (which as I recall is less above the tweeter axis), with some lift above 10 K to compensate for the narrowing dispersion of the tweeter. There were reasons for all the choices and some who are curious may want to try both and compare especially listening slightly above the tweeter axis in real world use. 40-50 ohms across the input terminals will flatten the input impedance for those who are concerned. I did take another quick look at the electrical response of the PB-1 tweeter crossover and this reminded me of these optimizations. Anyway, just wanted to point this out.
You can see from the measurements using foam that the results are not uniform across the bandwidth, and would require re-optimization of the filter(s). I view redesigning the speakers themselves as beyond the scope here, though I may yet try a reticulated foam pad in the grille. It's apparent, as Ray observed, that there's a mess of stuff going on between the baffle and the grille.
It's polyester in the ones I have, and for the closed-box version, at least, fiberglass may be a better choice. I will try that.
Resonance certainly was an issue when I altered the balance with BSC, which likely means it's there, but less audible, all the time. There are well-known means available to treat that, but precious little room inside the box to apply them. A wood veneer on the outside like the Cantons would be a good option, in my view.
That's a worthy endeavor, as well, I would say....
It's easy enough for me to do some rudimentary polars here, Pete, and I will do that, also.... :yes: