Newbie with questions over crossover

[kramma]

Hello,

Just for background its maybe worth mentioning that I am a reasonable wood worker, I am from UK but imperial units don't scare me and I can very much solder but I don't have a deep understanding of electronics.

I have bought Jack 12 plans in order to have some PA speakers for my band when we play (once/twice per year to a small crowd of sympathetic ears) and to provide a bit of a music system for small parties in my folks garden (maybe to be extended with some subs at some point). It seemed like the Jack 12 fitted the bill for a first go into making speakers and for what I may need. I have read the plans and it looks like the planned 12 inch woofer (in my case a Delta 12a) has a crossover design which needs 2 ASD1001 tweeters per cab which results in the crossover being 16 ohms. However, I need the speakers to be 8 ohms to go with my amplifiers that I already have. What are my options? Can I just go with one ASD1001 per unit? Where can I get details of the crossover for this - I am really not going to be able to design anything on my own so any help much appreciated.

Thanks for any help in advance,
All the best.


P.s. I cant buy the piezos here at the moment for a reasonable price from what I can see

[Tom Smit]

Hi kramma, and welcome to the forum!
Enjoy your build!
If you follow the plans you will end up with a fine speaker. In regards to the tweeters, it is fine that they will be wired up as 16 ohms; your amp won't care.

[Seth]

Hey kramma, good to have you here asking questions.

To add a second affirmation to Tom's response, the plans are very intentional, complete, and accurate. If you follow them blindly, you'll end up with the advertised results and a smile.

The final impedance of the completed cab will essentially be 8Ω. It would take more words than I'm willing to type to fully explain, and honestly I don't have a master level understanding of it all myself, to speak to it with bold clarity. But the nutshell version is that any speakers "rated" impedance is actually an average impedance. The instantaneous impedance is dependent on the frequency or frequencies the speaker is reproducing and will more often than not, be more than rated or less than rated impedance. In the case of this crossover and what the amp sees, the low frequencies will see an average 8Ω load and the high frequencies will see an average 16Ω load.

So, why 2 drivers wired in series at 16Ω instead of a single 8Ω driver? Bill will have to speak to that himself if he chooses, but my guess is power handling. He's always had budget in mind, so he'd absolutely have used a single driver if it was sufficient for the design, output, and response.

Like Tom said, your amp wont care and your ears will hear what they expect to hear.

Good question.

[Bill Fitzmaurice]

There are two drivers because the horn is too tall for one to work optimally or keep up with a 600w woofer. They're series wired because they have higher sensitivity than the woofer.

[kramma]

Thanks all I am blindly following and having a good time

[kramma]

Hello again,

Would someone kindly look at my purchase list for my crossover - would be great for someone to make sure I am not doing anything too mad before I press purchase. Please note I have chosen a 5.1uF cap for the tweeters as its much much cheaper than the 5uF cap that is availible. From what I can see would probably be ok (i.e. within the suggested 10%):

000-2013: 0.6mH Jantzen Iron Core Coil AWG21, 0.7mm diameter wire, Quantity 2
001-6141: 15uF 100Vdc Jantzen eLeCap 5% Electrolytic Bipolar Capacitor Quantity 2
001-0241: 3uF 400Vdc Jantzen Cross Cap Capacitor Quantity 2
000-0825: 0.9mH Jantzen Air Core Wire Coil AWG29, 0.3mm diameter wire, Quantity 2
000-1250: 1.8mH Jantzen Air Core Wire Coil AWG26, 0.4mm diameter wire, Quantity 2
001-0252: 5.1uF 400Vdc Jantzen Cross Cap Capacitor Quantity 2

Thanks again for all the help,
K

[Bruce Weldy]

Looks to me like you've got the right stuff....