I quickly cobbled together crossover for speaker project consisting of Altec 803a (new cone old spider and VC ) a 12 ohm nominal impedance in ~ 4 Cu Ft closed box , JBl 2441 trurextent dia 16 Om in 270 HZ (estimate) Tractrix horn (Sierra , Brooks) and tad Et 703 super tweeter (8 Ohm) Crossover is all 1 st order: 3mH on woofer , 20 uF on mid plus LPAD and 0.1 uF on a supertweeter .
I hooked up DAT's V2 to that bundle and the impedance plot is ruler flat at around d 15 Ohm from 100 Hz to 20 kHz . There is impedance peak at 75 Hz (aroud 80 Ohm) where F3 of the sealed cab is. I must be doing something wrong. It shouldn't be so good should it??
I hooked up DAT's V2 to that bundle and the impedance plot is ruler flat at around d 15 Ohm from 100 Hz to 20 kHz . There is impedance peak at 75 Hz (aroud 80 Ohm) where F3 of the sealed cab is. I must be doing something wrong. It shouldn't be so good should it??
Looks like it behaves as it should today
I don't start messing with "projects "without half a bottle of bourbon in the system so it might have influenced the V2 gizmo 😀
Now, I need to dust off that USB microphone rig. I haven't touched that stuff for years and was going to put it on the curb and clean the shed but it sounded so good last night that I finished the bottle and slept on the chair.
I don't start messing with "projects "without half a bottle of bourbon in the system so it might have influenced the V2 gizmo 😀
Now, I need to dust off that USB microphone rig. I haven't touched that stuff for years and was going to put it on the curb and clean the shed but it sounded so good last night that I finished the bottle and slept on the chair.
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That does seem suspiciously flat. And were are the twin BR peaks, the horn squiggles, the rise or fall in impedance caused by the filter factors?
There are no BR peaks because the cab is closed box. 8 x scan speak 10" (also in closed boxes in the corners) does bass duty up to 100 Hz. After I changed the cone in Altec 803A (spider and coil left intact) I felt that the driver lost its HF. I just put 3mH there (should be around 5 mH for 500 Hz but I forgot where I put those coils) but I could leave it open without a filter and it wouldn't make a difference in the mid. It's kind of a puzzle. I checked with a mic years ago when I put that box together and the output was there it just didn't sound like it was there. Maybe it is a good situation since mid coming out of midbass takes a lot effort. Midhorn is just crossed with single 20uF cap and attenuated with old wirewound L PAD (probably causing some HF loss due to its inductance ) and TAD ET 703 is just attenuated with a small 0.1uF cap . I use the setup with Belcanto SET40 ( 37W 845 SEt) and bass towers with 2 x 40W SS. Belcanto on Living Voice Avatar supposedly 94 dB speakers was slow like molases but on the horns it's faster than Naim. Everything is so damn snappy and fast that I think on ways to slow it down. I use an old 20uF V-Cap OIM on mids and russian 0.1 teflon on ET-703 .
I have a pair of JBL 2440 with JBL titanium diaphragms. When I compared Berylium truextent on 2441 to 2240/ti some years ago I liked old TI better in the lower mid , they sounded fuller and went lower than beryllium. I was planning to support it with TAD td2002 which you can see on the upper mid 1000 HZ Le Cleach horns but never actually ran the setup and with truextent 2441 I didn't feel the need. Now my hearing is going into shambles and it's the last chance I can mess with it and it's been fun.
I want to buy another set of walnut Altec Santana cabs to match the ones I have Scan- Speak woofers in and move the midbass 15" there. I will measure them again and pester experts here on the best way to employ them in given enclosure.
I'm listening to Classical on FM radio right now and it PRAT's like Metallica. Need to find a way to slow it a bit 🙂
I took impedance sweep of just a midbass in the cab without filter to make sure the rig measures semi correctly .
I have a pair of JBL 2440 with JBL titanium diaphragms. When I compared Berylium truextent on 2441 to 2240/ti some years ago I liked old TI better in the lower mid , they sounded fuller and went lower than beryllium. I was planning to support it with TAD td2002 which you can see on the upper mid 1000 HZ Le Cleach horns but never actually ran the setup and with truextent 2441 I didn't feel the need. Now my hearing is going into shambles and it's the last chance I can mess with it and it's been fun.
I want to buy another set of walnut Altec Santana cabs to match the ones I have Scan- Speak woofers in and move the midbass 15" there. I will measure them again and pester experts here on the best way to employ them in given enclosure.
I'm listening to Classical on FM radio right now and it PRAT's like Metallica. Need to find a way to slow it a bit 🙂
I took impedance sweep of just a midbass in the cab without filter to make sure the rig measures semi correctly .
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I suspect it is: try adjusting your scale to something more 'realistic', since at the moment you've got DATS displaying impedance in logarithmic mode with a vertical range of 0.1 ohms to 10k ohms. Fine (possibly) for measuring a variety of resistors, not so good for a loudspeaker. 😉 Change the starting point to 0 ohms, and drop the maximum to about 70 or 100 ohms rather than 10,000 and you'll find your graph looks more as you'd expect. I suggest you also shift it to linear scaling while you're at it.
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Scott is right of course, the scale is way too course. I haven't used DATS, but the WT3 would auto-range.
Thought the cabinet was ported, because it looks like a port above the woofer. Is that a horn cutout? A single peak is correct for sealed, and yours seems kinda high circa 75Hz.
Thought the cabinet was ported, because it looks like a port above the woofer. Is that a horn cutout? A single peak is correct for sealed, and yours seems kinda high circa 75Hz.
I don't see much that changed
The resonance peak is at 68 Hz which is kind of expected with woofer of Fs~45 Hz in too small of a closed box. Those woofers are 100 dB. I may have to use Zobel to flatten the peak (58 Ohms ) or it may not be needed. Once I pull the drivers from the cabinet (after I acquire those matching Santana boxes). I will measure the drivers again and maybe there will be a way to implement them better.
I have four of them (803A made by Altec for Heathkit) Two with original cones sit in Klipschorns bins and they produce the best midbass I ever heard . I had to change cones on the other two and they kind of became duller for whatever reason. The repro cones were advertised as very close to originals.
Ps. I repurposed some DIY cabs which looked decent enough and were the biggest size acceptable to just get started. Using sealed Box was the easiest approach
The resonance peak is at 68 Hz which is kind of expected with woofer of Fs~45 Hz in too small of a closed box. Those woofers are 100 dB. I may have to use Zobel to flatten the peak (58 Ohms ) or it may not be needed. Once I pull the drivers from the cabinet (after I acquire those matching Santana boxes). I will measure the drivers again and maybe there will be a way to implement them better.
I have four of them (803A made by Altec for Heathkit) Two with original cones sit in Klipschorns bins and they produce the best midbass I ever heard . I had to change cones on the other two and they kind of became duller for whatever reason. The repro cones were advertised as very close to originals.
Ps. I repurposed some DIY cabs which looked decent enough and were the biggest size acceptable to just get started. Using sealed Box was the easiest approach
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As a sanity check, measure impedance of the bare drivers without box/horn and without crossover. Compare to mfg datasheets, if they are close enough then you can also trust a measure in box with crossover. But I highly suspect that there is something wrong.
Ralf
Ralf
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