Im building a small 2 way portable speaker, using Aurasound NS2-326-8AT 2'' driver and Peerless SDS-P830656 drivers. Everything is going fine with the build....however i have hit a bit of a roadblock. Its time for crossovers! My situation is that i live in Australia and the crossover that i want to buy is just too expensive by the time i pay for postage to get it here from Parts Express, and i cant source one locally. The one i have in mind is the 800 hZ Dayton audio 2nd order crossover ( https://www.parts-express.com/Dayto...peaker-Crossover-800-Hz-12-dB-Octave-260-1794 ). Seems like a good starting point for my design. So i am happy to just buy the components and just build it myself which is straight forward enough. The part that i am stuck on is the inductor, i cant get a part number of it so i dont know which one to order, i know its a 3.2mh iron core inductor which is fine and all but this is where the part that seems to be confusing me started....They list the crossover as a 8 ohm crossover which is exactly what i need and want to build but am confused as to how they rate the crossover as 8ohm??? what makes it a 8 ohm crossover?? the inductor i assume? if anyone can help to explain how crossovers are rated could you please put me out of my misery. TIA..
Im not sure i know what you mean, I need to find out how the resistance of a crossover id determined. So basically i can then find out which components i need to purchase to build a crossover that satisfies my 8 ohm driver.
In my youth I've also bought stock xovers with this and that xover frequency and this and that impedance and married them with randomly chosen drivers of this or that impedance. But now I'm quite a bit more cautious, as the xover reactances need to be calculated using the related driver's impedance at the desired xover frequency. So you need to have a close look at the impedance curves, if supplied in the datasheets, or determine the impedance by yourself.
Best regards!
Best regards!
The crossover works in conjunction with the drivers that terminate it. The values in this low pass second order 800Hz crossover expect a nominally 8Ω driver connected to it. If the driver is 6Ω or 4Ω, the crossover frequency will change. You can buy quality components in Australia from Speakerbug. https://speakerbug.com.au/index.php?route=product/product&path=18_45&product_id=747
In the case of a second order LR filter, the component values are pretty straight forward. For both the capacitor and inductor, you need values that will have twice the impedance of the driver at the desired cutoff frequency.
There are many online calculators out there that will help. The capacitor value that has an impedance of 16 ohms at 800hz is 12.44uf. Likewise, the inductor value that has an impedance of 16 ohms at 800hz is 3.18mh.
I hope that answers your question. The math needed to verify that, at 800hz, the voltage across the driver is equal to half the input voltage is complex, but interesting.
There are many online calculators out there that will help. The capacitor value that has an impedance of 16 ohms at 800hz is 12.44uf. Likewise, the inductor value that has an impedance of 16 ohms at 800hz is 3.18mh.
I hope that answers your question. The math needed to verify that, at 800hz, the voltage across the driver is equal to half the input voltage is complex, but interesting.
Wagner Australia have the same Dayton inductors, but the nearest value stocked is 3.5mH. You can unwind a few turns to get the right value, but you need to be able to measure so without an 'L' meter it's hard. The inductor I posted above is close enough, and a better quality to boot. Here's the Dayton 3.5mH one: https://www.wagneronline.com.au/ind...s/audio-speakers-pa/ic183-5-77172/1000382/pd/
3.5 mH is what I've used in a similar project ( Vifa 8" + Monacor 2" spx21m )
but I've used it in the lowpass! And not 18 gauge/1.2 mm but 1mm wire ( it depends upon the power to be expected to be used)
For HP 2nd order, the coil is usually thinner (0.8 mm)- I used 22 uF cap ( I don't remember the coil value
say you don't know it!
)
but I've used it in the lowpass! And not 18 gauge/1.2 mm but 1mm wire ( it depends upon the power to be expected to be used)
For HP 2nd order, the coil is usually thinner (0.8 mm)- I used 22 uF cap ( I don't remember the coil value
say you don't know it!)Thanks for all the help guys.. this has definitely been the hardest part of the build to get my head around...im still learning..
I have called wagner, they actually list the crossover i need but have no stock atm and its a few months wait till they get one...and you guessed it...expensive! i may think of purchasing the 12uf capacitor from them as they have it and was also thinking that if i purchase the matching dayton 3.5mH inductor and take 2 or so coils off it as i have no way of measuring its inductance...i know its a bit rough but it looks like my only option right now!
This is spot on with what dayton has specd for their xover which makes sense, its good to have found out how they achieved these figures for a 8 ohm driver. thanks. I will now have a look for the components to see if i can find them, i will have a look at the one on speakerbug as johnmath mentioned, the one you mention is listed at 25 ohms which may not work?
I have called wagner, they actually list the crossover i need but have no stock atm and its a few months wait till they get one...and you guessed it...expensive! i may think of purchasing the 12uf capacitor from them as they have it and was also thinking that if i purchase the matching dayton 3.5mH inductor and take 2 or so coils off it as i have no way of measuring its inductance...i know its a bit rough but it looks like my only option right now!
just had a look at the inductor listed at wagner, seems its no good also as its 39 ohms! i need 16 ohms.
https://www.wagneronline.com.au/cro...ectronic-components/ic183-5-77172/1000382/pd/
https://www.wagneronline.com.au/cro...ectronic-components/ic183-5-77172/1000382/pd/
3.5mH is ~9% above the specified value of 3.2mH, but the difference is actually not very significant. That's why the 'normal' values have big steps up, e.g. from 2.7 to 3.3 to 3.9, and values like 3.2 and 3.5 are non standard. For a simple crossover it's normally ok to select the nearest close value. As the crossover gets more complicated with more components, precision becomes more important.
yes that seems ok then, however what do you think of the 39ohm rating? will that be ok at 800Hz? or do i need to look for another inductor?
or would this one be better suited at 25ohms?
https://speakerbug.com.au/index.php?route=product/product&path=18_45&product_id=747
or would this one be better suited at 25ohms?
https://speakerbug.com.au/index.php?route=product/product&path=18_45&product_id=747
Or you can have fun with math! A 3.5mh inductor is 16 ohms at 728hz. The capacitor value that is 16 ohms at 728hz is 13.66uf.
If you are okay with a 728hz LR crossover, two 6.8uf capacitors in parallel and a 3.5mh inductor works out nicely!
Raise the crossover frequency so the inductor is not so large.
3.5mH is a expensive coil.
For 2 way a 5" speaker should have response well up to 2 or 3k
so you can use Soft Dome.
In this case with a 2" fullrange for high frequency you can raise crossover
significantly higher. And use small coil.
Its not a 100 watt or 200 watt speaker.
So you dont need ridiculous oversized coils.
And definitely don't need iron core.
Should be a 4 dollar coil, not a 35 dollar coil.
many classic speaker just run woofer fullrange.
just need single capacitor for tweeter
3.5mH is a expensive coil.
For 2 way a 5" speaker should have response well up to 2 or 3k
so you can use Soft Dome.
In this case with a 2" fullrange for high frequency you can raise crossover
significantly higher. And use small coil.
Its not a 100 watt or 200 watt speaker.
So you dont need ridiculous oversized coils.
And definitely don't need iron core.
Should be a 4 dollar coil, not a 35 dollar coil.
many classic speaker just run woofer fullrange.
just need single capacitor for tweeter
so i had a look at some other air core coils and just cant seem to find the correct resistance to match for my 8Ω drivers. and on speakerbug they are still expensive.
http://www.linkwitzlab.com/Pluto/Pluto-2.1.htm
what would you suggest? im going off other peoples recommendations for the 800Hz. I have noticed that they have also been crossed over at 1kHz so i dont mind going a bit higher if it will help me source components. they have been crossed at 1 kHz in the pluto speakers listed in the below link
http://www.linkwitzlab.com/Pluto/Pluto-2.1.htm
I just played with a crossover @ around 2 kHz seems to work fine 1st order with 2" inverted
total highend is just all the 2" has
total highend is just all the 2" has
ohhh wow...thanks for all the effort...so what you are saying is i dont even need to have a inductor in my x-over for the NSW2 driver? just a cap and a resistor?
i wasnt going to have any crossover components for the peerless driver, i was just going to drive that directly from my mini amp. So should i ultimately go with your above design and incorporate components for BOTH my drivers or just build the high pass section for the NSW2 drivers. Would your above design be a better listening experience if i were to build the whole thing?
i wasnt going to have any crossover components for the peerless driver, i was just going to drive that directly from my mini amp. So should i ultimately go with your above design and incorporate components for BOTH my drivers or just build the high pass section for the NSW2 drivers. Would your above design be a better listening experience if i were to build the whole thing?
The rating is the series DC resistance of the inductor. A perfect inductor would have zero DC series resistance, but it would have to be made of a superconducting wire and kept at -273ºC!
The actual values are of the Wagner and Speakerbug inductors mentioned above are 0.39Ω (or 390mΩ) and 0.25Ω (or 250mΩ) respectively. As a rule of thumb it's normal to aim for these to be < 1/10 of the DC resistance of the driver' voice coil. The SDS-P830656 has a nominal 8Ω coil with a DC resistance of 6.1Ω, so either coil is fine. As the coil resistance gets higher it reduces the ability of the amplifier to control (damp) the behaviour of the bass driver, an issue which is more significant as drivers get larger and more massive.
I didnt plan on building anything for the main mid/bass SDS-P830656 drivers. I was just going to trim them from the bass and treble adjustments on my mini amp, i was only looking at building a crossover for the Aurasound drivers. So would these still be ok for building a x-over for them?