- Dec 18, 2000
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- greenboy designs: fEARful, bassic, dually, crazy88 etc
You can find midrange cups on eBay too - but I'd caution going with anything less than internal .09 cf or so.
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Adding Midrange Speaker/Crossover to 2x15 Cab
- Thread starter bluebledthesea
- Start date
You can find midrange cups on eBay too - but I'd caution going with anything less than internal .09 cf or so.
billfitzmaurice
Commercial User
- Sep 15, 2004
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It will suck.
Why use top quality drivers and then screw up the works by going cheap with the crossover? :scowl:
- Dec 18, 2000
- 13,201
- 340
- Disclosures
- greenboy designs: fEARful, bassic, dually, crazy88 etc
With a great midrange like the 18 Sound you don't need any more content up there, but I would consider it in spite of the less precise smeary imaging, with some of the other less sensitive midranges.
exactlyIt will suck.
- Dec 18, 2000
- 13,201
- 340
- Disclosures
- greenboy designs: fEARful, bassic, dually, crazy88 etc
Because it doesn't sound as good. If you have a good midrange driver why smear the response? You certainly don't need more dB.
Anyway, I am bi-amping, using an asymmetrical crossover choice that sums better in the case of the drivers I'm using.
Passinwind
I know nothing.
- Dec 3, 2003
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- Designer/Toaster Tech @ Passinwind Electronics
I do run that way in one of my modified commercial 2-way cabs, after having tried many other solutions. But that cab uses a 12 and a 1" compression driver, which make for a different ballgame.
I just use first order Butterworth low pass (a single inductor for rolloff) pretty often for both woofers and midrange drivers. I've found that to sound great with the 3015LF, personally. YMMV, of course. I also have a couple of cabs with 1st order high passes to the mids (single cap, 800Hz crossover, B&C 6MD38 drivers), and contrary to popular wisdom nothing has sounded distressed at all so far.
The power handling on that Beyma mid is lower than the 6.5" drivers I'm doing this with though, plus achieving max volume is not typically one of my most important design goals. Balancing that driver to two robust 15s is a pretty different animal than what I'm doing.
Like Greenboy, I prefer biamping in general. The Rane speaker management system I use for that is the bomb, really.
That did cross my mind, but I was concerned that the overall impedance of the cab would get screwed up. I was under the impression that the two way crossover would compensate for the fact that the woofers in parallel are at 4 ohms and the midrange is at 8 ohms. Maybe not so? I envisioned the three speakers in parallel and it coming out to like, 2.66 ohms. This probably isn't right, but it didn't seem like the correct thing to do regardless.
I imagine since no one else mentioned it the high pass filter takes care of the ohms so it's not dangerous, but it ends up sounding crappy anyway.
Passinwind
I know nothing.
- Dec 3, 2003
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How it sounds depends on how cannily you pick your drivers and crossover point. I'll say again: I've built numerous iterations of passive crossovers, and in some cases the simplest solution also ends up sounding the best to me. But sometimes my approach amounts to throwing money down a mine shaft, which I am willing to live with, and you may not be.
Be sure to take a look at the impedance curve for the 3015LF at your chosen crossover frequency, BTW. It's not an 8 ohm driver per se at that frequency, dig?
How it sounds depends on how cannily you pick your drivers and crossover point. I'll say again: I've built numerous iterations of passive crossovers, and in some cases the simplest solution also ends up sounding the best to me. But sometimes my approach amounts to throwing money down a mine shaft, which I am willing to live with, and you may not be.
Be sure to take a look at the impedance curve for the 3015LF at your chosen crossover frequency, BTW. It's not an 8 ohm driver per se at that frequency, dig?
Thanks Passinwind, all the support and suggestions I've received are more than helpful. I'll have to look at that impedance curve to better understand.
I know I'll have to review it some more, but this is my tentative shopping list. I am using 2 3015LFs and greenboy's suggested 6ND410. Calculations are from http://www.lalena.com/Audio/FAQ/XOver/
2 Way Crossover Board
L-Pad Plate and Control Knob
Solder
Wiring
Crossover (8 ohm mid, 4 ohm woofers, 800hz crossover, 2nd order Butterworth)
Capacitors - 17.58uF & 35.16 uF
Inductors - 2.25mH & 1.13 mH
L-Pad (8 ohm Z, 4 db attenuation)
Resistors - 2.95 Ohms & 13.68 Ohms
Series Notch Filter (5.9 ohms Re, 120 Hz fs, .27 Qes, 2.2 Qms)
Capacitor - 832.81 uF (??? This seems wrong to me as I can't find any parts close to that)
Inductor - 2.11 mH
Resistor - 6.6241 Ohms
I also understand that I am going to have to use high quality components, and/or better understand this page: http://www.lalena.com/Audio/Electronics/RCL/
I find this a little strange. The amp sees the entire network as a single impedance. If you had the inductance of the speakers you could work out the total impedance system.
No, it doesn't. The impedance is a function of frequency.
Actually, you can't, because a speaker is an electromechanical system. The impedance of a speaker is not simply R + L.
Asad
I can look this up, if I knew what I was looking for... I know it's measured in mH, would that be the same as Le, Coil Inductance? The 6ND410 is .67 mH and each 3015LF is .92 mH.
The network can be reduced to a single impedance without involving frequency.
The total impedance will have a positive or negative phase angle which will determine if the load is inductive or capacitive. Then you can bring in the frequency and determine what the total impedance is at a certain frequency and this is what the amp actually "sees"
billfitzmaurice
Commercial User
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That goes way beyond the capabilities of a newbie. He can use the driver impedance vs frequency chart on the Eminence driver data sheet. That will not show the effect of the enclosure on impedance, but at 800 Hz the enclosure is pretty much out of the loop anyway.
The mechanical aspect has absolutely no bearing on the system impedance apart from maybe physical loading of the driver
Kiddin'...billfitzmaurice
Commercial User
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As a matter of fact, it does. Not so much in a direct radiator alignment, though.
It most definitely cannot. Even if a speaker WERE just a simple inductor (which it's not, see my post above), the impedance of an inductor IS frequency-dependent -- i*omega*L. Period. No argument.
Take the simplest possible circuit you can think of: a resistor and inductor in series. The impedance is Z = R + i*w*L. How do you reduce that to a frequency independent number? Unless you know some math that I don't (and, statistically speaking, that's unlikely), you can't.
Asad
