Sreten: Thanks for the input(?). It's my turd, and the turd is going to be active. (Maybe even painted and polished. High Gloss...) Not because active is going to be cheaper, but because I need/want active. I do believe it will be cheaper and better because it is active. Yes, it is far more more complicated than the passive alternative, but then again, maybe it just me that do not have the talents to do these filters passive (4.order 120Hz?)
As for the wasted effort: all the electronics are good enough to be used in far better active designs. Feel free to do so 🙂
Kind regards
As for the wasted effort: all the electronics are good enough to be used in far better active designs. Feel free to do so 🙂
Kind regards
No need for impedance correction when active and think of the cap as dual purpose: Flattens the horns FR and is a safety device as a DC blocker.
Well, the impedance-correction is needed because the horn-impedance is inductive. More inductive than most tweeters, - I'm guessing that the airload on the "cone" is bigger with a compression-driver and therefore it looks more inductive than a dome? Anyways, - a single cap in line with horn do not make a very pretty 1.order filter. It works, but not the same FR as with the pre-amp filter.
Raw, and corrected, horn-impedance (if I measured correctly.)
Removing the resonance-peak would also be good, but that requires even more components.
Raw, and corrected, horn-impedance (if I measured correctly.)
Removing the resonance-peak would also be good, but that requires even more components.
An externally hosted image should be here but it was not working when we last tested it.
Power-handling and peak voltage Vs sub/sat crossover-freg?
Here is a modern pop-song as seen by Audacity: (Mary J Blige: family affair from Youtube)
Clearly the highest voltage-peaks are in the bass.
Level is -21dB at 66hz and -27 at 205Hz. So a HP at 150Hz would lower peak-voltage to the sat-speaker by 6dB.
This is true for a sat-speaker with no baffle-step-compensation. Full baffle-step for this small cabinet would mean that the 200Hz component is raised 6dB and then the sub/sat crossover-freq becomes irrelevant as far as peak-voltage goes.
Here is a quick estimate with a simple 6dB BSC centered around 500Hz and a 4.order HP at 150Hz done in Audacity (what a tool! - only just starting to discover it now)
As predicted the 200Hz component is now around -21dB
Does this look correct to you guys? Any else looked into these things?
Kind regards
Here is a modern pop-song as seen by Audacity: (Mary J Blige: family affair from Youtube)
An externally hosted image should be here but it was not working when we last tested it.
Clearly the highest voltage-peaks are in the bass.
Level is -21dB at 66hz and -27 at 205Hz. So a HP at 150Hz would lower peak-voltage to the sat-speaker by 6dB.
This is true for a sat-speaker with no baffle-step-compensation. Full baffle-step for this small cabinet would mean that the 200Hz component is raised 6dB and then the sub/sat crossover-freq becomes irrelevant as far as peak-voltage goes.
Here is a quick estimate with a simple 6dB BSC centered around 500Hz and a 4.order HP at 150Hz done in Audacity (what a tool! - only just starting to discover it now)
An externally hosted image should be here but it was not working when we last tested it.
As predicted the 200Hz component is now around -21dB
Does this look correct to you guys? Any else looked into these things?
Kind regards
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A bit disappointed by the analysis in the last post I did the same with another song.
Its a bit of "trance". Very melodic, well produced. Not the "lets-destroy-car-woofers-test-track".
The VU-meter in Audacity showed the same overall level as the other song (about -9dB), but look at the levels in the bass: -12dB at 50Hz.
After the same filtering as above (BSC and HP 150Hz) this is the outcome:
Now the highest peaks are around -21dB.
So it actually seams to lower the required peak-voltage to the satellite (at some frequencies) when implementing a BSC and a 4.order 150Hz HP. - with some songs at least.
I realize that this simple test is a bit misleading in that its the total signal-amplitude that sets the limit for the system and not he amplitude for a single frequency. A real-life test is coming up as most electronics are ready.
Its a bit of "trance". Very melodic, well produced. Not the "lets-destroy-car-woofers-test-track".
The VU-meter in Audacity showed the same overall level as the other song (about -9dB), but look at the levels in the bass: -12dB at 50Hz.
An externally hosted image should be here but it was not working when we last tested it.
After the same filtering as above (BSC and HP 150Hz) this is the outcome:
An externally hosted image should be here but it was not working when we last tested it.
Now the highest peaks are around -21dB.
So it actually seams to lower the required peak-voltage to the satellite (at some frequencies) when implementing a BSC and a 4.order 150Hz HP. - with some songs at least.
I realize that this simple test is a bit misleading in that its the total signal-amplitude that sets the limit for the system and not he amplitude for a single frequency. A real-life test is coming up as most electronics are ready.
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The "TURD" (truly Ugly Radiating Discospeaker?) i getting closer to a finished state. Now the first version of the alu-backplate is cut and the PCB's are mounted for a test. (Cutting 3mm alu plate on the tablesaw is easy with the correct blade) The grounding-scheme is OK so far as hum is very low. There is more hiss than I like and I havnt found the source. Its not the ClassD module, maybe some of the Ebay-cheapo-opamps?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
The turd is going outdoors ( for a test-session).
Nice calm weather so time for a test outdoors. Approx 180cm above ground. 1m and 2m distance from speaker to mic:
different angles up to 45 deg off axis
Ignore all data below 200Hz.
Not the definition of "flat response", but probably good enough for me, for now.
A couple of things have been giving me headache: Driver-polarity and hiss from the horn.
My measurements indoors did not provide any good indications as to which polarity was "correct".
But the outdoors measurements showed a clear difference and one polarity showed a clearly better response around cross-over.
The horn has a sensitivity around 95-98dB at 2-3Khz. This makes all the hiss from the electronics and the cheap class-D way to loud.
I tried different passive cross-overs to remove some of the hiss after the amp instead of filtering active before the amp. This proved to be pretty difficult due to the very non-linear impedance of the horn. I ended up with 15Ohm in series with 2.2uF. I haven't fully analyzed this, but as shown it works pretty good and it does lower the hiss to barely acceptable.
Nice calm weather so time for a test outdoors. Approx 180cm above ground. 1m and 2m distance from speaker to mic:
An externally hosted image should be here but it was not working when we last tested it.
different angles up to 45 deg off axis
An externally hosted image should be here but it was not working when we last tested it.
Ignore all data below 200Hz.
Not the definition of "flat response", but probably good enough for me, for now.
A couple of things have been giving me headache: Driver-polarity and hiss from the horn.
My measurements indoors did not provide any good indications as to which polarity was "correct".
But the outdoors measurements showed a clear difference and one polarity showed a clearly better response around cross-over.
The horn has a sensitivity around 95-98dB at 2-3Khz. This makes all the hiss from the electronics and the cheap class-D way to loud.
I tried different passive cross-overs to remove some of the hiss after the amp instead of filtering active before the amp. This proved to be pretty difficult due to the very non-linear impedance of the horn. I ended up with 15Ohm in series with 2.2uF. I haven't fully analyzed this, but as shown it works pretty good and it does lower the hiss to barely acceptable.
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Been measuring the output of the amps and the result are a bit odd.
Made a dedicated thread for that:
http://www.diyaudio.com/forums/class-d/276187-tda7498-ebay-strange-output-levels.html
Made a dedicated thread for that:
http://www.diyaudio.com/forums/class-d/276187-tda7498-ebay-strange-output-levels.html
Hi there - great project. I've been thinking of a similar project, but using the ol LM3886's in a similar fashion used in the Linkwitz Pluto. That amp arrangement would provide 100W or so for the bottom end and 60W for the top (and they're cheap as). Maybe use drivers that are easier to tame, but still relatively inexpensive. I have a DBX drive rack that could be used to design a crossover that would work with the drivers, then implement a dedicated active network?
Is this a good idea? And if so - what would be good choices for drive units that would provide a decent spl?
Is this a good idea? And if so - what would be good choices for drive units that would provide a decent spl?
Hi
As for using the 3886's: That should be a safe and solid option. A lot of commercial products do that. Behringers monitors for example. You just have to consider heat and max voltage for the amps.
I dont know the DBX, but any tool to simulate/emulate the cross-overs should be great.
I cant really decide if its a good idea. I should work, but you will need some sort of measurement setup like ARTA. I would have been totally lost without it.
I have no idea what other drivers might perform like. If I did this again from scratch I might used two of the Dy166 in one box to up the sensitivity and the power-handling.
The first test's on my boxes indicate that they are NOT as loud as I had hoped, but 6" drivers, extension to 50Hz and 50W do set some very real limitations. If you could limit low extension to 150Hz there are some more sensitive 6" mid-bass/mid drivers out there, but I havnt tried them.
Kind regards
As for using the 3886's: That should be a safe and solid option. A lot of commercial products do that. Behringers monitors for example. You just have to consider heat and max voltage for the amps.
I dont know the DBX, but any tool to simulate/emulate the cross-overs should be great.
I cant really decide if its a good idea. I should work, but you will need some sort of measurement setup like ARTA. I would have been totally lost without it.
I have no idea what other drivers might perform like. If I did this again from scratch I might used two of the Dy166 in one box to up the sensitivity and the power-handling.
The first test's on my boxes indicate that they are NOT as loud as I had hoped, but 6" drivers, extension to 50Hz and 50W do set some very real limitations. If you could limit low extension to 150Hz there are some more sensitive 6" mid-bass/mid drivers out there, but I havnt tried them.
Kind regards
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Thanks for the advice. I must get some software, but i have a mac and it seems most of the speaker building and RTA software is windows based.
I should probably start with something a little less ambitious…….Cheers
I should probably start with something a little less ambitious…….Cheers
Considering a change from class-D to good-old-lm3886.
The class-D boards I got from Ebay have some odd "error". The output voltage from one part of the bridge is approx 75% lower than the other. Thus total power gets somewhat smaller. I', guessing that the drivers could handle some more power (if limiting is implemented) correctly.
Thinking that a single 3886 for tweeter and 4pcs in bridge-par config would be ok for the bass. The insulated version is cheap on ebay and with 8Ohm load and +/-25V Im guessing it would work.
The PCB should not be a huge challenge.
Any ideas?
TroelsM
The class-D boards I got from Ebay have some odd "error". The output voltage from one part of the bridge is approx 75% lower than the other. Thus total power gets somewhat smaller. I', guessing that the drivers could handle some more power (if limiting is implemented) correctly.
Thinking that a single 3886 for tweeter and 4pcs in bridge-par config would be ok for the bass. The insulated version is cheap on ebay and with 8Ohm load and +/-25V Im guessing it would work.
The PCB should not be a huge challenge.
Any ideas?
TroelsM
I've built several amps using the LM3886 and they're really quite stunning, but I think they lack "punch" for want of a better word. I think they'd be ideal for mid range and tweeter work as they're very clean, but I'm not sure if they're an ideal choice for the low end. I believe they don't like 4 ohm loads either - especially when bridged.
I haven't tried other chip amps or used SMPS's with them - I guess there are many options……??
I haven't tried other chip amps or used SMPS's with them - I guess there are many options……??
After a long break from this project I've invested in some new drivers. Got a pair of brand new Monacor/stageLine SPH165 for really cheap. The data-sheet sensitivity says 89dB, but it simulates a LOT better/higher than the DY166.
The SPH165 also retail for approx 5-10times the price for a Dy166 so some difference was to be expected.
Hornresp says something like this for 14Liter closed box:
The "peaky" line is the DY166.
I'm considering adding a small port to get some more low-end from the SPH165 when its used without a sub. For LOUD-use I would block the port and cross over at 180-200Hz. - that simulates to power-handling around 100W/8Ohm within linear motion.
TroelsM
The SPH165 also retail for approx 5-10times the price for a Dy166 so some difference was to be expected.
Hornresp says something like this for 14Liter closed box:
The "peaky" line is the DY166.
I'm considering adding a small port to get some more low-end from the SPH165 when its used without a sub. For LOUD-use I would block the port and cross over at 180-200Hz. - that simulates to power-handling around 100W/8Ohm within linear motion.
TroelsM
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Comparison:
DY166. BL-factor around 4:
SPH165. BL-factor around 10:
DY166. BL-factor around 4:
An externally hosted image should be here but it was not working when we last tested it.
SPH165. BL-factor around 10:
An externally hosted image should be here but it was not working when we last tested it.
First "real" test for the system this weekend. Full throttle for 6hours. A ESP/Rod Elliot inspired LDR-limiter kept the amps from clipping, but the limiter was working actively most of the time, so working more like a compressor. 35v to the amp from an EBAY boost converter. Sub/sat crossover is 180Hz-4th order. A bit high, but OK as sub is directly under the sat.
Speakers and amps worked perfect all night and still sounding a lot better than one would expect from these cheapo components.
Speakers and amps worked perfect all night and still sounding a lot better than one would expect from these cheapo components.
An externally hosted image should be here but it was not working when we last tested it.
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Don´t think that I ever posted a link to the sub:
http://www.diyaudio.com/forums/subwoofers/291515-jbl-smallish-pa-sub-car-woofer.html
http://www.diyaudio.com/forums/subwoofers/291515-jbl-smallish-pa-sub-car-woofer.html
Fuzzmeasure is useful. Even the free version.
FuzzMeasure
And I run ARTA with WineBottler. Should work with a lot of other software too.
WineBottler | Run Windows-based Programs on a Mac
Working on a new balanced input-output-module with muting for ON/OFF. First PCB with tonertransfer silkscreen. Looks like a great technique.
A few error on the PCB due to an odd printer-glitch that "adds" stuff on the graphics!
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
A few error on the PCB due to an odd printer-glitch that "adds" stuff on the graphics!
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