Fast, fun, Inexpensive OB project

@Ozrocket and those who search for 20mH big Inductor :
Why don't you build them by a transformer builder ?
In my town (Lyon, France) I still have this little company who build transformer. And believe me the town has become an industrial desert.
And it is craftsmanship to wind transformer.
It is an idea, you can contact a company and see if they can build your custom coil in Adelaide or somewhere in Australia ?
Not sure it is expensive than an industrial made.

Yes as Pano said you can use 2x10mH, no problem, not ideal and not practical. A coil with 1.56 ohm lower the sensitivity, you have to adjust the mid range level and it rises the qts, lower bass response, in conclusion I don't think it is critical on this design.
 
I'm late to this discussion so it's not clear if this has been discussed.

USCoil, the company that was started after Erse closed, has a 20mh iron core inductor. https://uscoils.us/product/ussq55-16-20000/

Not sure if they ship to Europe or Australia nor what it might cost. But there's an email on their website to ask: sales@uscoils.us

Edit: Skip Pack mentioned the same thing a few pages back. Haven't run across a post that says they either do or don't ship overseas.
 
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. https://uscoils.us/product/ussq55-16-20000/

and 20$ for shipping standard ground in US?! what the heck are these crazy shipping prices we see today?

that brings the inductor to almost 60$

If someone was ambitious they could wind their own.

Last time I wound some ribbon transformers I used these guys for cores... I suspect the inexpensive silicon iron "C core" would work well for winding up your own 20mH inductor

https://www.bridgeportmagnetics.com/

they were great to work with and I often bought small quantities for development work but that was a few years ago
 
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Curiosity got the better of me. Pulled out the Manzi paperwork from 2007. Total cost of the build, not including wood and paint, was $350. Adjusted for inflation it'd be $531 today.

John said you could build a pair for $250. He must have gotten better pricing than the rest of us.

In my 2007 Manzi build the 12mh iron core inductor cost $21.75 from Madisound. No shipping charges as the order must have been high enough for free shipping. The inflation calculator puts that at $32.99 today.

It's fair to note that the price of coils really shot up after 2007, too, as copper prices went up. The price would have been higher in 2010.

Today USCoils has 12mh iron core inductors from an 18 gauge for $15.66 to a 16 gauge for $22.27. Cheaper than the inflation adjusted price but no free shipping.

Yeah, the gotcha is shipping. USCoils is a small company and can't throw in free shipping like the big retailers. But you also don't have the additional markup that the retailer would charge over the direct-from-manufacturer price.

Given the rise in the price of copper and the usual inflation over 15 years the prices seem decent. Given they have them available helps, too. It's not an easy part to find right now.

And a few months ago I had to pay $12 to ship an item that was, maybe, 2 ounces. Paying $20 for something as heavy and bulky as a coil seems almost OK in comparison. But only in comparison.
 
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BTW ALL
I bought the Goldwood 15 inch woofer because spec showed a healthy 10db rise at FS (see attached). This to use on open baffle
I measured and it does not have the rise claimed, Its more like 4-5db max.
 

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  • 15 inch Goldwood Fs rise 5db.jpg
    15 inch Goldwood Fs rise 5db.jpg
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Barry thanks for the cost history and reality check. I had conviently forgotten that the crossover started out with a 12mH inductor on the woofer. That's because we were crossing over the Peerless woofer at a higher point to meet the tweeter.

I do remember the price of inductors ju!ping up a long time ago mostly because of the cost of copper. FWIW, John did get the parts cheaper than retail, so maybe that skewed his cost estimate.
 
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I bought the Goldwood 15 inch woofer
You should be OK with the Goldwood. John Busch see the 18" version, 2 per side in one of his builds. As Barry will tell you, that double GW 18 version was prodigious. :)

With the Goldwood you will likely have to adjust the crossover to fit that woofer. You'll probably start be adjusting the series resistor on the tweeter to get it to match the level of the Goldwood. You might also need a different trap on the woofer according to where it's breakup peak is.
 
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A friend of mine heard my Manzanitas and got so besotted with them that he went home and built a set himself. Fine...? No, great disappointment - he says they sound like canned music. I suggested that he be patient and let the drivers "burn in". Anybody else who has hadthe same experience? (Mine sounded just fine right away, but I seem to remember that I put in used Peerles drivers.)
 
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Appropriate placement in the room is imperative. They should be away from walls if they aren’t already. The sound can change from not great to amazing depending on placement and listening position. What else is in the room is also a factor. That’s true for all OBs.
 
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As @von Ah writes, placement is (almost) everything. My Manzies were in about 1-1,1 m distance from the wall in the final placement, and one also must play with the angle.
But to some extent the build quality is also important, especially the cutout for the "FR-tweeter". Not enough place or sharp edges around and it will sound bad.
However - "canned music" tells me, that there must be some issues... maybe wrong phase of the FR?
 
Thanks Stuey.
I emailed harbuch and got the following reply, which may be of interest to others here:
I have also emailed several other transformer winding companies here in Australia, and will post replies here when I get them.


Hi Mal

I'm happy to wind things but don't have a lot of experience designing them.

Air cored ones are a lot easier to design because you don't have to
worry about the iron core saturating under high currents.


These pages may help you design an air cored one. Make sure any
calculator you use allows for multiple layers - some are only for single
layer coils.

https://www.diyaudioandvideo.com/Calculator/AirCoreInductorDesigner/

https://www.circuits.dk/calculator_multi_layer_aircore.htm

https://k7mem.com/Ind_MultiLayer.html

Generally the inductance goes up as the height goes down (for a given
diameter) and the diameter goes down (for a given height).

I'd start with a 25mm ID / 25mm high and see how you go. The copper is
around $40/kg. If you want to have a go at winding it yourself we can
sell you the wire. I think we have 1.3mm, 1.4mm and 1.5mm wire in stock
(perhaps 1.45 as well).

regards

peter


Peter McConaghy
Harbuch Electronics
1/2-8 Campbell St, Artarmon NSW 2064, Sydney, Australia
Phone: +61-2-9476-5854 Fax: +61-2-9476-3231
Email: sales@harbuch.com.au
 
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Anyone ever try the Fountek FE85 for this project (I saw that Lingwendil asked about them in post #3424 but I didn't see a response after a quick check of later posts)? I have 2 on hand in a long-ago mediocre project but if they were able to work in this project, I might try them. They seem pretty similar except for the Qts and excursion, both of which are lower in the Fountek. The Qts is particularly worrisome for an OB, but I admittedly don't know much about this, particularly where higher frequencies are concerned (e.g. how important the Qts is for tweeters?). If so, any pointers on how to adjust the crossover? I will dig into that at some point if folks think it's worth pursuing, but any pointers are always welcome.
 
Further to my last post....this just received from Incore tranformers here in Melbourne Australia (way too expensive!)

Good Morning, Mal,

Further to your email enquiry regarding 20mH inductors for speaker crossovers dated 18/12/23.

Can you please advise if AWG is the same size as B&S, viz

16 B&S = 0.0508" = 1.29mm diameter and

15 B&S = 0.0571" = 1.45mm diameter

If so, 20 mH would require an 80VA core, and the cost (per inductor) would be $300.00 plus freight, plus GST.

Please note, Ironcore Transformers is CLOSED for the Christmas Holidays from the 21st of December, 2023 until the 17th of January, 2024.

We thank you for your enquiry.

Regards,
Allan Grigg
Senior Design Engineer
 
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