February 3, 2022 at 3:58 am #22733jrandParticipant
I am very new to DIY speakers and would like to make a pair of floor standing speakers.
My “inspiration” was Toids’ collab with Kirby meets audio (https://toidsdiyaudio.com/2021/02/23/diyspeaker/), I find the build appealing, simple and it seems to be within my budget (although where I live, those parts will cost way past their price in the US).
So, my first thoughts were to try to replicate what Toids had done and I have a few doubts about Toids’ build and also about design of the speakers in general.
So, my first problem is dissecting Toids’ design. He mentions that he uses the RS180S-8 driver, however, in the video when showing for example the vented F3 off of parts express, he shows RS180-4, the non-shielded 4 Ohm version, which has different specs. At first I assumed there was a mistake and he had indeed used the RS180-4, but I cannot be sure.
The reason why at first I thought its the RS180-4 is because in winISD* I can get a nicer looking curve getting down to an F3 at 35Hz, while the RS180S-8 I can only manage to get to about 38Hz with a “bumpier” curve. But now I am more inclined to think that indeed the used driver was the RS180S-8. The enclosures I am simulating have volumes around 50~55L (1.76~1.94 ft³).
Now, while trying to replicate Toids’ design I used information from Toids’ videos on winISD and other sources to manage xmax at my rated power, and for that one needs to use highpass filters. My question is: where will I set these filters in the end, when driving the actual speakers?? I guess that these will be an integral part of driving the speakers the way they should, but is this done in the amplifier, in a DSP, an equalizer, or does anyone actually also build these in passively in the crossover? Because I need to take that into account in the end, when then shopping for the driving amplifier/electronics.
Another point that I would like to understand is the choice of drivers. The RS180S-8 is an 86.9 dB W/m while the RST28F-4 is rated for 93.5 dB W/m. However, in the end crossover design the two curves lie around 86 dB W/m, I can see that there is a resistor in series with the RST28F-4 which, should of course take power from that line and effectively reduce the output of that driver. Is this the correct way of thinking about this? Is the resistor there only to make a better impedance match? Should this also be taken into account when choosing drivers in a two-way, when pairing an 8ohm woofer with a 4 ohm tweeter? (I am sorry if this question sounds too ignorant, I didn’t delve into crossover design yet).
The reason why I ask is that I am now thinking instead of stepping up the speakers and go for the RS225-8 woofer, to try to get it to work down to 32 Hz paired with tang band 25-1719 (Note: as I am writing this I finally saw that actually this driver is rated for 8W RMS, which is too low, so scrape that. Its just that when I saw the RST28F it said 80 W and nothing else, and as the tang band 25-1719 says 8W RMS, 80 W max, I assumed that the RST28F also meant that its rated for 80W max, not RMS, but that seems to not be the case.) Oh well, this is bad news, because I wanted to crossover around 1.2 kHz, max 1.5 kHz but it seems that for that I would need to go for a 3-way design if sticking to the RS225. Its just that the step up in performance from RS180 to RS225 makes sense where I live as the price step is quite small.
Either way, all my other points remain. I will keep looking for something that would pair with the RS225 and would be within my budget. And I am forgetting one point that I also wanted to ask, but I guess I will just add it to the discussion if I remember again what I wanted to ask.
*About winISD, I am having troubles with the software, first, it just skips the installation of the driver database, I have been adding them manually and secondly, it becomes broken if I close it. When starting again changing the units doesn’t work, it actually just adds zeros to the values of the input box and the program seems buggy, with the graphs sometimes not displaying. I have to uninstall and re-install to be able to use it. Anyone had similar problems and was able to solve them?
I thank you for reading and for your insights
EDIT: I remember now my other question. It is about port tuning in regards of its 1st resonance and being above the crossover frequency. Is there a guideline to where to place this first frequency? I mean, I did not try it yet, but I guess that one can go back and forth between the tuning of the crossover design and winISD to tune the port to be sure that the first resonance is completely attenuated. What I found in the particular case of trying to replicate Toids build is that the air velocity is basically at the 20 m/s level for a slotted port which has a first resonance around 1.96kHz.
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