About to begin 3-way project. advices please!! - diyAudio
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Old 20th August 2009, 11:27 PM   #1
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Default About to begin 3-way project. advices please!!

Hi!!

I started a post in the temporal forum. Sorry about opening another but I'm in a kind of a hurry because I already bought the speakers and cant wait anymore to try them.

This is what I want to do.

I will use two speakers at the beginning, and maybe later if it is necessary, I will add a super-tweeter for >15kHz.

Woofer: 10" B-10K GB-Audio http://www.gb-audio.com.ar/B-10K.html
Mid & High: Fostex FE167E

Some specs:
- The crossover point will be like 250Hz. I will try to find polypropylene caps, but I will need 4 x 39uF that will be very expensive. Maybe array of 1uF's caps, maybe good quality 40uF electrolytic cap.
- Fostex will be impedance compensated with zobel network
- woofer will not be compensated since at low frequencies the impedance variation is not appreciable.
- 12db/octave crossover filters, attenuator for the Fostex (95db vs 89db woofer)
- 3 separated cabinets. One for the woofer (85 liters), one for Fostex & tweeter (15 liters) and the rest for the crossover.
- 5mm plywood for the cabinet and maybe another 5mm layer of MDF


Click the image to open in full size.


thanks for your help and greetings to all the staff for the upgrade of the forum
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Old 20th August 2009, 11:44 PM   #2
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5mm is very thin for a speaker box, Use atleast 19mm mdf or high density particle board or grade a marine plywood.

There is a bennic 40mf electrolytic cap or a 39mf poly clarity cap, no need to use array of smaller caps, making the box stronger is more important.

I think you'll gonna need more than 6db of midrange attenuation, once you factor in the baffle step response and the positioning of the speaker in the room.

Just make the xo , so that it is easily removable for tweaking.
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Old 20th August 2009, 11:51 PM   #3
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Quote:
Originally Posted by marchel View Post
5mm is very thin for a speaker box, Use atleast 19mm mdf or high density particle board or grade a marine plywood.

There is a bennic 40mf electrolytic cap or a 39mf poly clarity cap, no need to use array of smaller caps, making the box stronger is more important.

I think you'll gonna need more than 6db of midrange attenuation, once you factor in the baffle step response and the positioning of the speaker in the room.

Just make the xo , so that it is easily removable for tweaking.
I forgot to say something, I live in Argentina. So, I can't get good caps. Thats why I though of using array of caps.

you're right about plywood, it was a mistake, what I was thinking is 10mm and then another layer of some mm's of MDF.

As the crossover will be in a separated chamber, it will be very easy to test different configurations.

do you know how much $$ is the 39uF poly cap?

thanks for your help
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Old 21st August 2009, 12:26 AM   #4
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Cant you order on www.madisound.com ?

40mf Solen poly cap = $13.95
40mf bennic bipolar cap=$1.25
39mf clarity cap px =$18.95
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Old 21st August 2009, 11:12 AM   #5
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Things I would do.
Check this woofer (simulation) in WinISD for a closed (if so) box volume. Same with the Fostex.
Check with the Edge for the right ~4dB BSC with a similar front baffle. Same with the Fostex.
Here you can make the box (vol. from WinISD) with better wood, make it 18/19mm thick. Same with the Fostex.
Choose the right inductor and frequency output for the woofer to 250Hz.
Check carefully the midrange for the right BSC ~100-1KHz.
Maybe using a 6dboct./1order (or similar) xover for a start.
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Old 21st August 2009, 11:56 AM   #6
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the other thing to worry about is the inductor for the woofer. Do some reading about bi-amping. I was originally going to go with the approach you have decided on, but in the end decided designing a 3-way crossover was going to be too hard, and although I'm not there yet (had a four year break, just getting back to it) I'm planning to do a passive two way crossover for the mid/tweeter and an active for the woofers.

Think of it like having a set of two ways with stereo subs which cross over at a higher frequency than a traditional sub. This will also make it much easier to match your speakers efficiency, rather than attenuating your mid/tweeter, you just make sure the is more gain/bigger amp driving the woofers

Tony.
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Old 21st August 2009, 12:00 PM   #7
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Audyncap plus capacitors are good to. Ive used them quite a few times and give good results. Interesting looking speaker though. Make sure you do progress reports on the build.
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Old 21st August 2009, 01:28 PM   #8
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Quote:
Originally Posted by marchel View Post
Cant you order on www.madisound.com ?

40mf Solen poly cap = $13.95
40mf bennic bipolar cap=$1.25
39mf clarity cap px =$18.95
Mmmm I think I can order from madisound. The thing is that I have to multiply by 4 the price because of the currency. Imagine that you have to pay u$s 70 for the 39uf clarity cap px.

I will think if it's worthy. thanks!!

Quote:
Originally Posted by Inductor View Post
Things I would do.
Check this woofer (simulation) in WinISD for a closed (if so) box volume. Same with the Fostex.
Check with the Edge for the right ~4dB BSC with a similar front baffle. Same with the Fostex.
Here you can make the box (vol. from WinISD) with better wood, make it 18/19mm thick. Same with the Fostex.
Choose the right inductor and frequency output for the woofer to 250Hz.
Check carefully the midrange for the right BSC ~100-1KHz.
Maybe using a 6dboct./1order (or similar) xover for a start.
Are you recommending to use a sealed box with the woofer? sorry I didn't understand at all..my english is not the best. What is "BSC"?

For now, I will use only 2 way.

Wood will be then plywood 1" thick.

Quote:
Originally Posted by wintermute View Post
the other thing to worry about is the inductor for the woofer. Do some reading about bi-amping. I was originally going to go with the approach you have decided on, but in the end decided designing a 3-way crossover was going to be too hard, and although I'm not there yet (had a four year break, just getting back to it) I'm planning to do a passive two way crossover for the mid/tweeter and an active for the woofers.

Think of it like having a set of two ways with stereo subs which cross over at a higher frequency than a traditional sub. This will also make it much easier to match your speakers efficiency, rather than attenuating your mid/tweeter, you just make sure the is more gain/bigger amp driving the woofers

Tony.
Bi-amping sound quite good, but is not the moment for me. I dont have the money for another amp. Maybe later will diy a PA100 2xLM3886 for each channel, I justo bought a Marantz amplifier and don't want to bi-amp now.
It's a pitty that I have to attenuate that much the Fostex, 95db vs 89 but it's the best woofer I can get here.

But for the future I will think in bi-amping, also the marantz is 7.1 system so I hace line-out for sub-woofer and can set the crossover point with the DSP of the marantz.
thanks!!

Quote:
Originally Posted by hasaudio.co.nz View Post
Audyncap plus capacitors are good to. Ive used them quite a few times and give good results. Interesting looking speaker though. Make sure you do progress reports on the build.
I will post every detail, dont worry

At the begining I will use cheap electrolytic caps and once I've decided the rigth values I will see where to buy decent caps.

I have lot of 1mm copper wire for make the inductors.

This week I will start with the cabinets.

greetings,
Jorge.
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Old 21st August 2009, 01:56 PM   #9
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BSC = Baffle Step Correction

Dont expect to get more than 85 dB from your woofer. You should not assume half-space acoustic loading for the woofer if you place the woofer as high as on your drawing, and also place the speaker far from walls in your room.
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Old 21st August 2009, 02:27 PM   #10
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Good to here. Looking forward to the progress pics!
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