I modifying an old pair of 3-way towers I built years ago when I was 17 (am now 36). They are solidly built with loads of internal bracing, they look pretty good and have amazing bass output which is pretty flat to below 30Hz, if not lower.
Anyway, right now there's a Vifa P21WO-20 8" woofer, an old cheap JBL midrange out of an old center channel speaker I blew years ago, a Bose 2" tweeter, and a high quality Parts Express 3-way crossover. It sounds okay, but nothing great.
I'm going to ditch the midrange, tweeter and crossover and install a new top baffle to fit my FE103E on. I'm going to need to design a simple 2-way crossover between the FE103E and Vifa P21WO-20 8" driver. I have the notch filter that I slapped together a while back for the Fostex drivers which worked out great and will incorporate that into the new crossover.
I'm guessing I'll be setting the crossover point somewhat low around 100-200Hz, and want it to be a simple 1st order, but want the Fostex to cover most of the range, obviously.
The Vifa is rated at 91dB @ 1w/1m, the Fostex is 89dB @ 1w/1m.
What I need to know is what are the actual component values are going to be to get things in the ballpark. That way I can at least get them up and running, then I can tweak things from there.
Many many thanks in advance for any information and help I can get on this guys!
Anyway, right now there's a Vifa P21WO-20 8" woofer, an old cheap JBL midrange out of an old center channel speaker I blew years ago, a Bose 2" tweeter, and a high quality Parts Express 3-way crossover. It sounds okay, but nothing great.
I'm going to ditch the midrange, tweeter and crossover and install a new top baffle to fit my FE103E on. I'm going to need to design a simple 2-way crossover between the FE103E and Vifa P21WO-20 8" driver. I have the notch filter that I slapped together a while back for the Fostex drivers which worked out great and will incorporate that into the new crossover.
I'm guessing I'll be setting the crossover point somewhat low around 100-200Hz, and want it to be a simple 1st order, but want the Fostex to cover most of the range, obviously.
The Vifa is rated at 91dB @ 1w/1m, the Fostex is 89dB @ 1w/1m.
What I need to know is what are the actual component values are going to be to get things in the ballpark. That way I can at least get them up and running, then I can tweak things from there.
Many many thanks in advance for any information and help I can get on this guys!
Hey chops, haven't seen you post in a while. Good to see you back.
You might be able to get some ideas for your FAST from this thread. http://www.diyaudio.com/forums/css/176790-el166-mtm-ml-tl.html?highlight=el166+mtm
dave
You might be able to get some ideas for your FAST from this thread. http://www.diyaudio.com/forums/css/176790-el166-mtm-ml-tl.html?highlight=el166+mtm
dave
Thanks for that link. Totally forgot about it as it's been a while since I've done any DIY work.
Hi Dave. Thanks for the warm welcome back. Disappearing from here for a couple years is the result of a girlfriend! LOL She's cool though and lets me do pretty much anything when it comes to my stereo(s).
Stupid question... What does "FAST" stand for?
Also, I read that entire thread, but fail to see what that has to do with my current project at hand. It doesn't talk about the FE103E driver and barely mentions anything about crossover design.
It is broadly similar to your project & the only one i've done with an XO recently.
XO is very simple. 1 coil, 1 cap in a series configuration. If you are planning on XOing as low as you suggest you may well find a couple plate amps to be cheaper.
dave
Yeah, you're right - the inductors would still be a lot... A 6.8mH for a 200Hz first order, would be the cheap end, and that would be what... $30-35/side including the caps? Not great, but not so terrible either. 400Hz or so would drop it to around $20.. I'm not so much arguing with you as thinking out loud here, but I don't think I'd go with plate amps.
Let me think along with you.
I needed 3mH on the MTM with 4 ohm woofers XO 300-350Hz. Double that for 8 ohms and then double again for halving the frequency, that's 12 mH. If the XO is pushing down towards 100 Hz you get close to that 20 mH. An iron core choke is going to be a bad idea here, and really low you are going to get the resonance peak to really screw you up (not so bad on the high pass side, as the cap gets more effective as the impedance rises, but 103 Fs is not far from 100 Hz (a bit higher on the last ones i measured).
So if passive an XO >200 Hz. I usually try to put them near the baffle step point.
Cheapest and most elegant solution, is the thrift store or garage sale amp/reciever + a PLLXO. Over the last couple years a couple standouts i scored were a 100w Sharp for $10 and a Technics New Class A (70w) for $5.
dave
I needed 3mH on the MTM with 4 ohm woofers XO 300-350Hz. Double that for 8 ohms and then double again for halving the frequency, that's 12 mH. If the XO is pushing down towards 100 Hz you get close to that 20 mH. An iron core choke is going to be a bad idea here, and really low you are going to get the resonance peak to really screw you up (not so bad on the high pass side, as the cap gets more effective as the impedance rises, but 103 Fs is not far from 100 Hz (a bit higher on the last ones i measured).
So if passive an XO >200 Hz. I usually try to put them near the baffle step point.
Cheapest and most elegant solution, is the thrift store or garage sale amp/reciever + a PLLXO. Over the last couple years a couple standouts i scored were a 100w Sharp for $10 and a Technics New Class A (70w) for $5.
dave
I don't understand. According to the crossover calculator, for an 8 ohm driver crossed over at 200Hz, it says I need a 6.37mH inductor, not 20mH. Even at 100Hz, that's only a 12.74 mH inductor. I would probably go with a 7mH inductor for roughly 180Hz. At PE, that would be a $20 purchase per channel.
For the caps, now that's a different story as it calls for a 110.42uF cap. Luckily, I already have two 51uF Solen caps from an old speaker project that I can use. So I just need to get a couple more to add up the difference.
For the caps, now that's a different story as it calls for a 110.42uF cap. Luckily, I already have two 51uF Solen caps from an old speaker project that I can use. So I just need to get a couple more to add up the difference.
We look the crossover frequency 6dB down, not 3 dB. The second thing is the driver has a rising impedance or the case of the fostex an impedance peak at 100Hz. The third thing is baffle step ... We think it is not easy to have a crossover point at 100Hz.
Why don't you use your 2x51uF cap on the 2xfostex ?
A crossover frequency 500Hz is a good point. I add if you want a good phase response, you must make a second order crossover. You need big coils 4.7mH and big capas 50uF.
If you use 4.7/5mH and 47/51uF for Low Pass/High Pass(HP) you will have 400Hz crossover frequency. The fostex will need attenuation, a 0 to 10 ohms resistor before the HP filter and also needs to be reverse. The Vifa and the fostex must be on the same front plate.
Hope this helps.
Why don't you use your 2x51uF cap on the 2xfostex ?
A crossover frequency 500Hz is a good point. I add if you want a good phase response, you must make a second order crossover. You need big coils 4.7mH and big capas 50uF.
If you use 4.7/5mH and 47/51uF for Low Pass/High Pass(HP) you will have 400Hz crossover frequency. The fostex will need attenuation, a 0 to 10 ohms resistor before the HP filter and also needs to be reverse. The Vifa and the fostex must be on the same front plate.
Hope this helps.
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Any other thoughts/ideas? Dave?
I would like to keep the crossover frequency below the critical midrange area and if at all possible, use these huge Solen 51uF caps. I want to be able to work a baffle step into the circuit as well as my existing notch filter for the Fostex.
Just for giggles, I will be combining these two together, mounting a new baffle over where the current midrange/tweeter is and placing the FE103E where the midrange sits.
I would like to keep the crossover frequency below the critical midrange area and if at all possible, use these huge Solen 51uF caps. I want to be able to work a baffle step into the circuit as well as my existing notch filter for the Fostex.
Just for giggles, I will be combining these two together, mounting a new baffle over where the current midrange/tweeter is and placing the FE103E where the midrange sits.
Box looks like it is gonna baffle step arounf 400 Hz. Issue with passive is swaping components around till it is right. 51 uF should get the FE103 close enuff to the 200 Hz ballpark. I would strongly recommend series XO here. They seem to be more tolerant of not quite perfect size parts. I had to play alot with the choke (3-6mH was tried).
dave
dave
Any examples of series vs parallel?
If you were to use these particular drivers in a 2-way setup as I am, what would YOU do? Crossover points, etc, etc...
Any other thoughts/ideas?
1. I think it will more simple to add a subwoofer to the fostex monitor. Crossover frequency 100Hz. Dave has already submitted this idea.
2. You can simply improve the crossover of your tower ? If you give details : what are the drivers ? the crossover schematic with the values. We can try to wake it up
Take a closer look... those are Chops' high performance cardboard boxes. The driver in them is FE126eN -- is that the driver you gonna use, or have you FE103 now?
dave
1. I think it will more simple to add a subwoofer to the fostex monitor. Crossover frequency 100Hz. Dave has already submitted this idea.
2. You can simply improve the crossover of your tower ? If you give details : what are the drivers ? the crossover schematic with the values. We can try to wake it up
Both decent ideas but neither of which I want to do.
The Vifa P21WO-20 is a very good driver and performs very well in this enclosure. The lower part of the enclosure (from the floor up to just under the midrange sub-enclosure), measures in at 2.34cf and it's tuned to 39.5Hz via a simple 3"x3" schedule 40 PVC coupler. I'm going to see if I can extend that some with a straight piece of pipe. If I get the overall port length up to 8", the tuning frequency will drop down to the desired 28Hz as per what WinISD Pro suggests. As it sits now, there's a bass peak centered around 50Hz with max group delay around 40Hz. Tuning lower will smooth out that peak completely and will also lower the group delay considerably and put it down around 25Hz. All of that should clean up the bass.
The midrange sub-enclosure is sealed and is packed to the gills with acoustic stuffing. It is roughly 0.43cf, a bit large for the FE103E, but will work.
Just as a side note, the enclosure is 10"W x 16"D x 40"H, external dimensions, constructed with 0.75" Birch plywood and 0.75" MDF. Also, three 0.75" MDF cross braces as well as 1"x1" corner braces in every corner in full length.
Hey, don't make fun of my "high performance cardboard boxes"! Both the FE103E's and the FE126eN's sounded darn good in those cheap test boxes. They were good enough to prove to me that these little Fostex drivers are very worthy and deserve further usage.
Yes Dave, those are the FE126eN's in that picture. If you remember, I sold them a while ago on here. I wish I still had them, but I think I'll be just as happy with my little FE103E's (I had these several months before getting the FE126eN's from you). They have plenty of "break-in" on them already, upwards of a 1000 hours, though they have been sitting for over two years now...
Get two plate amps and use the high level ins. That way you can make use of the XO on the high level outs for the Fostex and you have control over the woofers ie: no concerns with baffle step and an ability to tailor the sound to your liking.
It costs a little more but I can safely say you'll not regret the choice. I've done it with 3 systems so far.
Okay. I should have rephrased that question of mine, making it clear that I don't want to use plate amps and active crossovers. I want to just build a simple 2-way passive crossover with the baffle step in mind and the notch filter that I already built for the FE103E's.
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