Hello. Hoping you more-educated &/or experienced folks can help me out with figuring out what inductor value are in these Totem Hawks. They're not marked, so I disconnected them & took a reading with an LCR tester (see pic), but the reading doesn't make sense. The woofer is supposed to be 6 ohms, the crossover frequency is supposed to be 2500Hz, but these numbers just aren't adding up. I'm sure I'm missing something & could use some guidance. Measurement shown. Please & thank you in advance.
It's possible you come up with different values between a theoractely filter and the practical filter which contains the drivers , enclosure etc .
The reading makes perfect sense. Appears to be 1.5mH, 5% tolerance.
Initial assumption of the formula design is insufficient. Neither is impedance as low as 6 ohms,
nor does the formula incorporate free space loudspeaker cabinet placement.
Is this Hawk filter a simple 1st order design? One inductor for LP, one capacitor for HP and some resistors?
Initial assumption of the formula design is insufficient. Neither is impedance as low as 6 ohms,
nor does the formula incorporate free space loudspeaker cabinet placement.
Is this Hawk filter a simple 1st order design? One inductor for LP, one capacitor for HP and some resistors?
Did you measure the woofer? Looking at the sensitivity spec for the speaker, it might be 4 ohms nom.
jeff
Correct - simple 1st order plus resistors on the tweeter circuit. The MB is confirmed to be 6 ohms (see picture).
Yessir, measured 6 ohms. Keep in mind: these were not off the shelf drivers, these were custom engineered per Totem's specs. It's my understanding these had more x-max.
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ALL: Sorry for the delay in getting back & THANK YOU for assisting. The woofer has been disconnected from the circuit and confirmed to be 6 ohms. I've also measured the 2nd speaker's inductor, and it measured 1.53mH. The only thing I presented which may be off is the supposed crossover point of 2500Hz, which I read direct from Totem's site, but I also understand there were different tweeters and crossover components used throughout the years, so I'm good with throwing the theoretical 2.5k crossover point out the door, and focusing on readings only:
If we have a 6.0 ohm woofer and a 1.5-ish mH inductor, the theoretical crossover point is around 620-ish Hz, and there's no way this titanium dome tweeter crossing that low. So.. what gives?
If we have a 6.0 ohm woofer and a 1.5-ish mH inductor, the theoretical crossover point is around 620-ish Hz, and there's no way this titanium dome tweeter crossing that low. So.. what gives?
Woofers with a nominal 8 ohm IMPEDANCE (which varies with freq) typically measure around 6 ohms resistance.
You also need to know or measure the freq response of any woofer. If is nowhere near flat, especially up near 2-5kHz.
You also need to know or measure the freq response of any woofer. If is nowhere near flat, especially up near 2-5kHz.
'MB is confirmed to be 6 ohms' - that's DC resistance, what's its impedance at the crossover frequency?
Has baffle step been addressed in the xover?
Has baffle step been addressed in the xover?
Yes, 6 ohms is a DCR measurement. I don't have the hardware & software combination to do an impedance sweep, and Totem is a fairly reputable company, so it's highly unlikely they're crossing the custom Scan Revelator 5.5 way up in the breakup area, where the impedance would be way out of whack. Here's the closest 15W/8530K-00 (8 ohm version) sweep.
Let's (for entertaining your critique's sake) presume the impedance graph plots close to this one, minus a couple ohms across the board. Even then, at 2500 Hz we would have a ballpark of 7 to 8 ohms impedance. Even at 8 ohms, the coil's reading would have the woofer crossed at 850 Hz, so it doesn't make sense. Which brings us back to square one: what gives?
Let's (for entertaining your critique's sake) presume the impedance graph plots close to this one, minus a couple ohms across the board. Even then, at 2500 Hz we would have a ballpark of 7 to 8 ohms impedance. Even at 8 ohms, the coil's reading would have the woofer crossed at 850 Hz, so it doesn't make sense. Which brings us back to square one: what gives?
I don’t get this. It’s a paper cone driver, but of course they cross it in the breakup area. The impedance shows minor bumps around 1k, nothing that will disturb a good crossover. And the coil will, as almost always be bigger to correct for baffle step correction.
Perfectly normal behavior for a coil. It’s a log scale on the frequency axis. Change it to linear and the line becomes a straight one. I really don’t understand your point though, a series coil will also show this kind of impedance curve.
Friendly advice, do not attemp to reduce DCR without having a full schematic and simulation. Series inductors less important than parallel
This might be of interest https://www.diyaudio.com/community/...sign-why-tweeter-polarity-is-reversed.412576/
btw, what's the problem? Without having true impedance measurements and frequency response of this woofer in the cabinet, everything's just waffle.
I guess something you could do is crib the tweeter capacitor value and see what weirdness is going on there, too.
Coming back on this, I started with a sine generator, an amp, a more or less true RMS multimeter, a resistor of about 100Ω and a variable resistor from an L-pad. You might have most of the stuff and a sine generator can be found in every smartphone or computer these days.
RE the link: Yes! I remember reading this thread sometime ago, thanks for the reminder. I think comment 14 might explain: mechanical/speaker natural roll off + the electrical/inductor to tame the woofer's not-so flat response beyond 1k would make sense.
RE cap value: I considered that. Weirdness is right. Same circuit as his thread's diagram, with the 3 parallel resistors and a single resistor in series, and the capacitor value is 2.55uF with a tiny bypass/coupling cap. The tweeter, most claim to be MB Quart 95-6773, is roughly 5.5-6 Ohms.