I wind air cores from salvaged inductor bobbins. All the wire I salvage is kept for winding. I can add inductance by splicing with same size wire (insulate the splice), and of course take windings off to reduce the value.
Minimus 7 Loudspeakers - Measurements
- Thread starter Zilch
- Start date
And by the way, it is always interesting to see the reverse null to determine if the drivers
are in phase at the crossover point.
js22
Active Member
So I finished the speaker project.
Here's the inductors with some little brackets I 3-d printed.
I had some sound absorber laying around from an old project, so I lined the cabinets and glued the inductors in. I was shocked that they fit in sideways. Oops, forgot to take that pic.
Then I took the workmanship down a notch and installed the XO components with lots of hot glue.
Then I added the original fill material and installed the tweeter and....you might already see what I completely failed to notice. Jumpin up and down on that woofer wasn't gonna get it any farther in than this.
Fortunately, I'm one of those people who doesn't really "believe" in the supposed miraculous powers of glue. And I'm right. I pushed on the (epoxied-in-place-a-day-ago) inductors and was able to crack them free. Then I hot-glued them into their new position. The nifty little brackets were pretty much accomplishing nothing after this manouver...
Anyway, after these few last minute shenanigans, I ended up with a nicely buttoned-up pair of PZ-2.1 Minimus 7s.
Here's the inductors with some little brackets I 3-d printed.
I had some sound absorber laying around from an old project, so I lined the cabinets and glued the inductors in. I was shocked that they fit in sideways. Oops, forgot to take that pic.
Then I took the workmanship down a notch and installed the XO components with lots of hot glue.
Then I added the original fill material and installed the tweeter and....you might already see what I completely failed to notice. Jumpin up and down on that woofer wasn't gonna get it any farther in than this.
Fortunately, I'm one of those people who doesn't really "believe" in the supposed miraculous powers of glue. And I'm right. I pushed on the (epoxied-in-place-a-day-ago) inductors and was able to crack them free. Then I hot-glued them into their new position. The nifty little brackets were pretty much accomplishing nothing after this manouver...
Anyway, after these few last minute shenanigans, I ended up with a nicely buttoned-up pair of PZ-2.1 Minimus 7s.
js22
Active Member
Listening impressions.
I didn't come anywhere close to doing an A/B with these. My only "before" listening was in my living room with my home system (Fisher C1/M2 or is it C2/M1 ?)
At work I connected them to a Pioneer SA-7500 I recently brought back to life. Put them up on a shelf a bit higher than ear level, about 2 feet away, each 45 degrees to the side. I hooked up a cheap little DVD player with a CD of Thelonious Monk and John Coltrane. I had to fiddle with speaker A/B and Selector inputs before the sound came through so I missed the first few notes.
Holy (#2) ! For a split second I thought I was going psychotic. The sound was coming from "over there!" Like way out in front of me. The keyboard down low, the sax higher up, the soft steel brush on cymbals higher up still. The speakers themselves had completely disappeared. Now this was much closer to a set of speakers than I usually listen, and I haven't done headphones since the '80s. So I just wasn't ready for that kind of extreme imaging. It got my heart going, to say the least.
And, while they are small speakers, I didn't feel any need to apologize for them not having enough bass. Sure a nice sub would round things out on the low end, but even without it I didn't feel like the experience was lacking. This is a seriously fun pair of little speakers.
Thanks to all for supporting this project. I really feel like I learned a lot.
I didn't come anywhere close to doing an A/B with these. My only "before" listening was in my living room with my home system (Fisher C1/M2 or is it C2/M1 ?)
At work I connected them to a Pioneer SA-7500 I recently brought back to life. Put them up on a shelf a bit higher than ear level, about 2 feet away, each 45 degrees to the side. I hooked up a cheap little DVD player with a CD of Thelonious Monk and John Coltrane. I had to fiddle with speaker A/B and Selector inputs before the sound came through so I missed the first few notes.
Holy (#2) ! For a split second I thought I was going psychotic. The sound was coming from "over there!" Like way out in front of me. The keyboard down low, the sax higher up, the soft steel brush on cymbals higher up still. The speakers themselves had completely disappeared. Now this was much closer to a set of speakers than I usually listen, and I haven't done headphones since the '80s. So I just wasn't ready for that kind of extreme imaging. It got my heart going, to say the least.
And, while they are small speakers, I didn't feel any need to apologize for them not having enough bass. Sure a nice sub would round things out on the low end, but even without it I didn't feel like the experience was lacking. This is a seriously fun pair of little speakers.
Thanks to all for supporting this project. I really feel like I learned a lot.
js22
Active Member
Is that some type of orange external vibration dampening material in the last pic?
Listening to a nice sound system is a joy in itself. Sometimes, being reminded what you paid is a whole nother layer of enjoyment, even though at $19 I didn't exactly get these on the cheap. Those tags are gonna come off when I get around to cleaning the speakers.
But as of last Friday night, I feel like I've "joined the club", as it were. I went to pick up a pile of "for parts or repair" gear from a CL ad, and the guy just threw in a pair of Optimus Pro X77's for free.
js22
Active Member
Okay, so I brought my "new" speakers home and gave them a serious listen-to in the living room, playing the same album I played before. It's an album each and every person on the planet should own and listen to frequently. That just might border on "attitude" so I'll just move on to objective audiophile facts without mentioning the album (Gillian Welch : The Harrow and the Harvest) by name.
So the speakers aren't perfect. There is a kind of "peaky" quality to the vocals where some specific notes resonate a bit too much. I lowered the volume a little to avoid this unpleasantness. But unlike my pre-mod listening, I made it through the whole album without feeling fatigued. The music sounded, as an audiophile would say, pretty good. In particular the (thankfully subtle) banjo had a clarity and precision than I haven't heard before.
One of the things I like to do with this album is play "listen for whats-his-name." Her husband/partner (what's his name ?) sings along with her, but you absolutely can't hear him without intense effort. You just assume that her voice is richer and more complex than any one person's voice has a right to be, which is what makes him (whats-his-name) a truly awesome back up vocalist. If the Grammys gave a prize for tiniest ego in the music industry, it would probably go to Gillian Welch's husband/partner. I forget his name.
Anyway, playing that game with these speakers is fun. I couldn't *actually* hear his voice (which is not humanly possible, of course) but I felt like I came closer than ever before.
Bottom line, these are not going to be my full time living room speakers. But for what they are (tiny, extremely heavy, precise speakers) they are very impressive. I think I'll end up using them in my bedroom for fall-asleep duty or in my office where I can impress people who only know POS computer speakers.
Disclaimer: Author of this review receives no material consideration from from Gillan Welch (or her husband/partner/that-dude) for sales of albums not specifically titled "The Harrow and the Harvest", which you should very seriously consider purchasing and listening to frequently. Approximately 3 aluminum beverage containers were damaged during production of this opus. And yes, of course, you are welcome.
So the speakers aren't perfect. There is a kind of "peaky" quality to the vocals where some specific notes resonate a bit too much. I lowered the volume a little to avoid this unpleasantness. But unlike my pre-mod listening, I made it through the whole album without feeling fatigued. The music sounded, as an audiophile would say, pretty good. In particular the (thankfully subtle) banjo had a clarity and precision than I haven't heard before.
One of the things I like to do with this album is play "listen for whats-his-name." Her husband/partner (what's his name ?) sings along with her, but you absolutely can't hear him without intense effort. You just assume that her voice is richer and more complex than any one person's voice has a right to be, which is what makes him (whats-his-name) a truly awesome back up vocalist. If the Grammys gave a prize for tiniest ego in the music industry, it would probably go to Gillian Welch's husband/partner. I forget his name.
Anyway, playing that game with these speakers is fun. I couldn't *actually* hear his voice (which is not humanly possible, of course) but I felt like I came closer than ever before.
Bottom line, these are not going to be my full time living room speakers. But for what they are (tiny, extremely heavy, precise speakers) they are very impressive. I think I'll end up using them in my bedroom for fall-asleep duty or in my office where I can impress people who only know POS computer speakers.
Disclaimer: Author of this review receives no material consideration from from Gillan Welch (or her husband/partner/that-dude) for sales of albums not specifically titled "The Harrow and the Harvest", which you should very seriously consider purchasing and listening to frequently. Approximately 3 aluminum beverage containers were damaged during production of this opus. And yes, of course, you are welcome.
lolwtfbbq
New Member
I've got 4 pairs of Minimus speakers I'm looking to upgrade. Since this is a budget speaker, and the PZ-2.1 is a budget crossover, I'd like to keep it as such.
PE is currently sold out of their brand ferrite core: https://www.parts-express.com/dayton-audio-10mh-18-awg-i-core-inductor-crossover-coil--257-550
Which is too bad because the only other option looks to be twice the price. So I have a couple of questions.
First, how important is it for the DCR to be .19ohm or lower? How much wiggle room do you think we have there?
Also, does anyone have a cheaper US based source for caps and resistors or parts in general? I don't mind buying in bulk and having leftovers. I'll eventually find a use for them, even if it's only to build a bunch of extra crossovers.
I looked at the PZ 2.2 but that won't save me any money either.
I'm looking at $120 in parts, which isn't terrible, but it's not great either. At least I'll get free shipping.
PE is currently sold out of their brand ferrite core: https://www.parts-express.com/dayton-audio-10mh-18-awg-i-core-inductor-crossover-coil--257-550
Which is too bad because the only other option looks to be twice the price. So I have a couple of questions.
First, how important is it for the DCR to be .19ohm or lower? How much wiggle room do you think we have there?
Also, does anyone have a cheaper US based source for caps and resistors or parts in general? I don't mind buying in bulk and having leftovers. I'll eventually find a use for them, even if it's only to build a bunch of extra crossovers.
I looked at the PZ 2.2 but that won't save me any money either.
I'm looking at $120 in parts, which isn't terrible, but it's not great either. At least I'll get free shipping.
https://meniscusaudio.com/product/1-00mh-18sl/
Do you think you might upgrade the woofers down the line?
Do you think you might upgrade the woofers down the line?
RTally
Speaker addict
I've got 4 pairs of Minimus speakers I'm looking to upgrade. Since this is a budget speaker, and the PZ-2.1 is a budget crossover, I'd like to keep it as such.
PE is currently sold out of their brand ferrite core: https://www.parts-express.com/dayton-audio-10mh-18-awg-i-core-inductor-crossover-coil--257-550
Which is too bad because the only other option looks to be twice the price. So I have a couple of questions.
First, how important is it for the DCR to be .19ohm or lower? How much wiggle room do you think we have there?
Also, does anyone have a cheaper US based source for caps and resistors or parts in general? I don't mind buying in bulk and having leftovers. I'll eventually find a use for them, even if it's only to build a bunch of extra crossovers.
I looked at the PZ 2.2 but that won't save me any money either.
I'm looking at $120 in parts, which isn't terrible, but it's not great either. At least I'll get free shipping.
The cost is high because you are doing 4 pairs and the inductor is about 1/2 the cost of the crossover. Your total is about $30 per speaker pair, which is less than I spent a year ago. The inductors are often out of stock with PE. I just checked, and PE shows them in stock.
lolwtfbbq
New Member
Thanks!
Doubtful that I'll upgrade drivers. I'll probably focus on building a proper set of powered studio monitors before I consider getting that deep into these.
If I were going to go that far, I'd probably skip the passive crossover altogether and use a miniDSP nano digi as an active crossover. However there's only so much you can get out of these little enclosures and I don't think it's worth chasing waterfalls. They are really neat little speakers, and I love the metal enclosures, but I spent $5-10 per pair on these and I don't really think they're worth adding 10x that in upgrades.
I only have plans to use a pair of Minimus 7's at work and a pair of Minimus 77's in my daughter's room. That leaves me with an extra pair of each. The Minimus 11's get used on camping trips and in the garage sometimes, but I don't really have any desire to crack those open until something breaks.
You sure you're looking at the same inductors I linked? The $7.50 ERSE ones are showing as in stock, but not Dayton's brand.
I'm aware that the inductors are the majority of the cost of the project, that's why I specifically asked about a cheaper substitute / one with not quite so low DCR.
Edit: I also meant to ask if Mylar caps in lieu of Polypropelene would be a reasonable compromise in this design. I mean it's already using an iron core inductor, the drivers are kinda cheap and the enclosure isn't really the right size for them anyway so I doubt there would be much audible difference.
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RTally
Speaker addict
Oops. I was looking at the Erse. Order the Dayton inductors and wait two months. PE is pretty good at shipping stuff as soon as they are available. Or order some of each and by the time you are ready to do the other pairs, you may the the less expensive ones in hand. A 10% or even 20% difference in DCR for the inductor will not have much impact on the crossover. A much lower DCR will have minimal impact on the circuit.
As for lower cost caps and resistors that you asked about, there may be less expensive ones available. But you are looking at pennies difference. Chasing pennies is not worth it to me considering the search time and the cost of shipping for a second order.
lolwtfbbq
New Member
I don't disagree that it's not worth the time searching. That's one of the things I love most about PE; their search function and site layout is so good. I was really just looking if I could put together a more affordable parts list for the benefit of the thread. I think I'm just going to do one pair now with what PE has available and take some time to see if I can source alternative parts for the next 3 (or more) upgrades.
http://www.audiokarma.org/forums/in...-2-0-mh-21-ga-laminated-core-inductor.863598/
Buyout inductor is more expensive than PE house brand but has far less copper, perhaps call
them and suggest that the price is too high.
Buyout inductor is more expensive than PE house brand but has far less copper, perhaps call
them and suggest that the price is too high.
Hey there,
those will be my very first speakers bought if I take aside my boombox journey. How can I know the year of those minimus-7? Mine are black metal, Realistic, 40-2030C, made in Japan for Radioshack. A Tandy Corporation division. And on the sticker I can read: No. 7540.
Thanks for help!
those will be my very first speakers bought if I take aside my boombox journey. How can I know the year of those minimus-7? Mine are black metal, Realistic, 40-2030C, made in Japan for Radioshack. A Tandy Corporation division. And on the sticker I can read: No. 7540.
Thanks for help!
lolwtfbbq
New Member
Got a package from PE today.
I'm mocking up how everything will fit inside the Optimus Pro x44's. There is considerably less space in this box than the Minimus 7's for a few reasons:
They have a big ol' stud with a tapped hole on the back of the enclosure. Presumably for a mount. It takes up a lot of space and makes orienting everything difficult.
There's a port tube behind the tweeter that's not in the most convenient place. Mounting anything up there is out of the question.
The driver is shielded and leaves only about 1-1/4" space from the back of the enclosure to mount stuff. Luckily that's exactly the height of the ERSE standoffs on the coil, so I know that if I can manage to keep everything below the height of the coil then I'm golden.
https://i.imgur.com/y0w9VAr.jpg
I'm mocking up how everything will fit inside the Optimus Pro x44's. There is considerably less space in this box than the Minimus 7's for a few reasons:
They have a big ol' stud with a tapped hole on the back of the enclosure. Presumably for a mount. It takes up a lot of space and makes orienting everything difficult.
There's a port tube behind the tweeter that's not in the most convenient place. Mounting anything up there is out of the question.
The driver is shielded and leaves only about 1-1/4" space from the back of the enclosure to mount stuff. Luckily that's exactly the height of the ERSE standoffs on the coil, so I know that if I can manage to keep everything below the height of the coil then I'm golden.
https://i.imgur.com/y0w9VAr.jpg
lolwtfbbq
New Member
I mocked up the circuit. I think this is right but if someone could spot check my work I would greatly appreciate it.
Of course the layout will look nothing like this in the box, I just want to make sure I'm hooking everything up correctly.
Edit: I also plan to re-use the spring plate. I'm going to remove the spring clips, fill the holes with epoxy, drill new holes and mount proper banana jack posts in the recessed area.
Of course the layout will look nothing like this in the box, I just want to make sure I'm hooking everything up correctly.
Edit: I also plan to re-use the spring plate. I'm going to remove the spring clips, fill the holes with epoxy, drill new holes and mount proper banana jack posts in the recessed area.
