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Resistors; suggestions / comments
I’ll be needing to pad down (~8.5 to 9.5 ohm) a fairly sensitive driver (Audio Nirvana, with a notch or two) with one that’s clearly not (Epique), running as a 1.5 way. Any comments on the Dayton Audio 20W (with Internal ceramic tube) and/or the Twisted Zister 25W (Meniscus), and/or other suggestions welcome.
I’m expecting to use a parallel / series combo to get the power rating up and add some stability. And, what recommendation as to the level i.e. should / do I need to cma with a 200W target? I’d like to have put a large cap on the AN to trim the low level signals upfront, but the driver isn’t having it.
Thanks
Comments
The zisters do require heatsink mounting to reach full 25W heat dissipation. They do look cool, though.
Nothing wrong with the 20W Dayton.
thx, the dayton's are what I was leaning towards and can mount just at /above the board for circulation
How much power will it see? This can be modeled in some of the crossover software.
The AN states 30w rms, the Epique states 200w rms.
I've been testing initially with just two 10w resistors upfront (of the AN) and they haven't gotten warm (?), but I haven't cranked the music too much. I am running with two parallel notches, so some additional resistors in-line as well.
I'm now thinking four 20w resistors (in a series/parallel configuration to get the AN driver to match up with the Epique) will give 80w dissipation (and hoping to keep the smoke in the fireplace this winter).
If you are working in VituixCAD, there is an option under the View menu for Power Dissipation. I did it for one of my files and it gave this:
Luckily, these are RMS values, so I would need to beef up R2 (currently a 10W part) if I wanted to run continuous 100W test tones through these - but running music signals is much less of an issue
Sehlin Sound Solutions
Flat spectrum is not very realistic of any real world use case for a speaker. In any case, power dissipation of resistors is dependent on location in circuit and value, which is why such a tool is necessary.
Switch to M-noise for a more accurate representation of power in music.
If you use M-noise on that plot, the peak that shows 60W in the other plot drops to about 0.5W. I can get it to about 5W running the full rated output of one of my 500WPC pro amps.
Sehlin Sound Solutions
Sehlin Sound Solutions
500 watts - the voice coils would be vaporized in anything I've built for home use.
M-noise is good for typical normal use with clean power and high dynamic range long term, I wouldn't use that for sizing resistors. They should be sized for short term power delivery, closer to "worst case real world". Flat full spectrum is unrealistic, I think PN above 2kHz with 6dB crest factor is a good place to start for peak power usage.
Thx for the input on VituixCad Power Dissipation (flat/pink noise/m noise)
For my application it looks like the 4 pack (series/parallel) of 20w resistors to pad the Audio Nirvana will more than do (indicates 44w max, which is almost 2x headroom at 40 volts 200 w 8ohms / 400 w 4 ohms) , with max on one of the notch resistors ~17.
Thanks
Dumb question, why not run the Epique in parallel on a 2 ohm stable amp? You reduce xover coils by half, and gain +6dB in sensitivity to better match your AN widerange.
InDIYana Event Website
Wolfy's Photobucket
Great question/ suggestion, actually. If it were only an 8+8ohm (vs 4+4), the +dB in sensitivity would clearly be the way to go.
While I expect my amp (Legacy Powerbloc4) would handle the load, I'm building this as a potential next year MAC/DIY trip event project and I don't want to put out a 2ohm load into someone else's amp... just in case.
Our regular standby has current to spare, good sir.
Remember the winning InDIYana entry last year had <2 ohm impedance across the entire sprectrum.
I still can't believe that EQ's winning entry did not trip the protection circuitry on the power amp that was used. @Wolf , was that a Crown amp? Stable into a 1 ohm load?
It's my amp. Bring it!
Sehlin Sound Solutions
Stable to 2 ohms stereo. Might be the fact that we didn't drive it with a lot of power. Remember that the current demand is the main problem in low impedances. As long as the voltage requirement does not exceed that of the power supply, to where it sags or clips, it will be fine if the current demand can be met.
It really amazes me how robust these Crown amps are.
InDIYana Event Website
Wolfy's Photobucket
I think I had the same series as you, Wolf. The XLS2000? I never pushed mine too hard in live use, seeing that they were powering stage monitors or top boxes on occasion. They never got warm, even outdoors in the Summer!
Yep, I use the 2000 for the event.
InDIYana Event Website
Wolfy's Photobucket
I have a vintage Proton 930 receiver running my computer speakers and it's rated for 2 ohm loads.
"The Proton 930 demonstrated an exceptional output-current capability. Its measured 1,000-Hz output power at clipping was 44 watts into 8 ohms, 63 watts into 4 ohms, and 66 watts into 2 ohms. Its dynamic power output was even more impressive: about 54, 78, and 130 watts into 8, 4, and 2 ohms, respectively."
Ron
I use an XLS1500 at work and have a 2500 at home. I use them because they will try to drive a dead short for about a couple seconds before going into protection. Then you just unhook the problem speaker and it's as if nothing happened. Fantastic amplifiers.