For this particular application:
These are HT surround speakers and will not be in a freefield space.
Todd has a Sunfire sub that will loosen your fillings. I don't think
pushing near 100dB/1m (+ boundary reinforcement and x4) at 30Hz is
going to be much of a limitation, loudness-wiseIt will be interesting
to see what the midband sensitivity is (the 92dB-SPL value might be
max value vs averaged over a more typical use band).
got bored during lunch today... v(5) and v(17) are "outputs"
R4P can be lowered to 64ohms ... has effect of changing
LF Q (small bump, to rolled off early)
RN1 can be adjusted some to play with the dip depth (compensates
for a peak in horn+driver response)... speaking of LCR networks
RLP1 and RLP2 form a 16ohm L-pad, maxed out.
Intended to work with acoustic roll off and FR of 242[5|6]J on 2470,
as well as WT10GTi with voice coils in series (~12ohms nominal),
roughly matching sensitivities.
Might want to raise the top end more (tilt, 5KHz+) if listening off axis.
Impedance roughly stays within 6-12 ohms (simulated)... RL1P is
included for simulation only.
I have no idea if this would actually work in a real-life case, but would be
entertaining to build up with existing/inexpensive parts and compare (to improve
model/assumptions).
WT10GTi and 2425 on 2470
Vin 1 0 AC
L1 1 2 2.8mH
RL1 2 3 .3
RL1P 1 3 10MEG
C1 3 0 21uF
L2 3 4 1.0mH
RL2 4 5 .2
Cz 5 6 11uF
Rz 6 0 12
Le 5 7 1.6mH
R4 7 0 12
R4P 5 0 64MEG
CH1 1 12 14.0uF
RH1 12 0 15
LH1 12 202 1.2mH
RLH1 202 0 .2
RH2 12 13 20
RH3 13 14 20
CN1 13 15 10uF
LN1 15 16 .8mH
RN1 16 0 20
RLP1 14 17 .1
RLP2 17 0 72
RHP 17 0 20
RHF 17 0 16
Guess I need to see the schematic to understand the part placement, circuit nuances, and their implications.Originally Posted by grumpy
2nd and 3rd columns are network "node" numbers.
Parts connect the nodes. Node 1 is the voltage input, Node 0 is ground.
(Inductor DCR's are included in the sim)
OK, that makes sense now and I can visualize it looking at a typical network. Guess I need to draw it out to fully understand it. (I've never expressed a schematic that way nor seen it done that I can recall.)
You're proposing 10 and 60 MEG resistors in a crossover network?
Also, how many watts would the various value resistors need to be rated for a 200 WRMS crossover?
BTW, All Electronics has a good price on nonpolarized caps that could be used for experimental purposes.
http://www.allelectronics.com/cgi-bi...Non-Polar.html
old SPICE netlist format... free versions abound. Requires a fair bit of
background knowledge to be useful and understand limitations. I haven't
fooled with it much for many, many, years but it's familiar ... so, for me,
it's fast.
I'm sure most crossover design tools that folks discuss here are much more
suited to the task, in terms of practical topologies and the ability to
import/export data to/from measurement programs.
I don't think soYou're proposing 10 and 60 MEG resistors in a crossover network?
"R4P can be lowered to 64ohms ... has effect of changing
LF Q (small bump, to rolled off early)"
"RL1P is included for simulation only."
I left R4P in as a placeholder... putting RL1P in allowed SPICE
to converge on a simpler representation of the circuit.
If I have time, I'll do this more rigorously.... guesses for now:Also, how many watts would the various value resistors need to be rated for a 200 WRMS crossover?
As the 12 ohm resistor in the LPF leg doesn't see too much under 1KHz, I'd think 20-40W, depending on
use would be OK.
In the HPF leg, 10W for the 20ohm resistors would probably be fine. The 15 ohm unit on the input should be
larger ... 40W...
Most home use environments won't run anywhere near full-steam for very long, so specifying 100% sine-wave
capability would be a waste. Also a 200W/8ohm amp will usually run out of gas at ~130W/12 ohms, ~100W, 16ohms
(power supply voltage limited).
Using a tunable sine-wave input: for full "200W" input, you'd be pushing a bit
over 100W into the 15 ohm resistor above 1KHz... while the driver would be seeing
about 3W (roughly 113dB @ 1m). I'll presume that most listening isn't done at 3dB
below clipping, (now down to ~50W) and that most of the energy is below 1KHz
(so make it smaller). In hindsight, I probably would weigh individual resistor
power dissipation more heavily in the design considerations.
The 20ohm resistors on either side of the LCR notch are dissipating about
30W at full sine-wave power (over fairly small bandwidths), resistor in LCR is less.
In the low-pass leg, making the 12 ohm resistor 30W, would be overkill... even
at "full power" (peak dissipation frequencies in this leg are ~550 and 890Hz,
less than that everywhere else)... but then resistors that would work for this duty
are cheap (three 33ohm 10 watters in parallel).
So, for now, I'll stand by my guesses for real-world use
One could certainly design this differently to keep the HF impedance higher and
not waste so much heat. Keep in mind this was just an exercise and I am not
even close to being an experienced crossover designer. -grumpy
I was asking myself that very question just yesterday. At 12 Ohms, any amp is gonna start clipping at a lower SPL, no, 'cause it's outta voltage headroom?
I'll measure the actual impedance with the voice coils in parallel. While there are amps spec'd below 4 Ohms, these are likely to smoke most conventional amps at 3 Ohms if cranked, wouldn't we think?
Running passive two-way, which sounds great, BTW, the HF is attenuated ~20 dB to balance with the woof voice coils series connected.
unless you have an outputAt 12 Ohms, any amp is gonna start clipping at a lower SPL, no, 'cause it's outta voltage headroom?
transformer, or rail switcher, or ... but generally, yes.
mostly, yeah... I'd think you'd want...wouldn't we think?
to think twice about hooking a potentially sub-3ohm load to (-two- channels here)
a typical HT receiver, for example.
BTW, the HF is attenuated ~20 dB to balance with the woof voice coils series connected.Yep. If you look at the FR plot, in the legend you'll
note I added 17dB to the HF portion for visualization... I figure you can dial back the rest
with the L-Pad.
-grumpy
So what crossover circuit are you using and do you have a FR plot (yet)?Running passive two-way, which sounds great, BTW, the HF is attenuated ~20 dB to balance with the woof voice coils series connected.
BMS 4552 with P-Audio PH-35 throat adapter on $10 90° x 50° PT waveguide.
3120A Mid = Min, HF boost = Med. Outboard L-Pad on HF driver.
HF is black curve in second image, post #50, +/- 1.5 dB, approx.
I haven't "fixed" the 3120A LP filter to match the W10 driver. AutoEQ's still doing that, FR-wise.
I'll take the impedance measurements, then I'm done with it 'til I want to build some L100 killers....
WT2 impedance curves.
Series connected voice coils, in vented L40 cab, Zmin = 14.46 Ohms @ 137 Hz. Z @ 1 Hz = 13.18 Ohms.
Parallel connected, free air, Zmin = 3.66 Ohms @136 Hz. Z @ 1Hz = 3.34 Ohms.
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