4" portable subwoofer
Hello,
I have two speakers (one 3" and one 4") and I would like to use one of them to make a very compact subwoofer for complementing a boombox I made a while ago.
The speakers I have available are these two:
I calculated the enclosure with THIS online calculator and apparently the most compact result I would get using a sealed box with the volume of ~3.2L and ~4L respectively.
For a filter I am using THIS and for the amplifier THIS. I added some extra decoupling to the amplifier and I am running it at 16V.
I made the boxes in OnShape and cut them to size but the result is not great.
The 3inch one seems very week and the 4inch one sounds a little better but not great. I found it difficult to describe the sound but it's not "crisp" or "punchy" if that makes any sense.
What should I do to significantly improve the sound and still maintain a compact size?
Hello,
I have two speakers (one 3" and one 4") and I would like to use one of them to make a very compact subwoofer for complementing a boombox I made a while ago.
The speakers I have available are these two:
I calculated the enclosure with THIS online calculator and apparently the most compact result I would get using a sealed box with the volume of ~3.2L and ~4L respectively.
For a filter I am using THIS and for the amplifier THIS. I added some extra decoupling to the amplifier and I am running it at 16V.
I made the boxes in OnShape and cut them to size but the result is not great.
The 3inch one seems very week and the 4inch one sounds a little better but not great. I found it difficult to describe the sound but it's not "crisp" or "punchy" if that makes any sense.
What should I do to significantly improve the sound and still maintain a compact size?
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Measure the real TSP as those provided by Monacor are not always accurate.
A ported (or 6th order bandpass if you are ambitious) enclosure has the potential to be louder than a sealed one. Tune it for maximum output in the range from 50...70 Hz to about 100 Hz. Add a highpass filter at the lower cutoff to protect the drivers and to prevent wasting amplifier output at low frequencies, at which the speaker is not efficient. Move the low pass filter down to 150 Hz.
A ported (or 6th order bandpass if you are ambitious) enclosure has the potential to be louder than a sealed one. Tune it for maximum output in the range from 50...70 Hz to about 100 Hz. Add a highpass filter at the lower cutoff to protect the drivers and to prevent wasting amplifier output at low frequencies, at which the speaker is not efficient. Move the low pass filter down to 150 Hz.
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@TBTL I know how to measure the resonant frequency (Fs) but I could try to learn how to do the others also. It is disappointing that these might not be accurate because since I am just learning how to do this, my measurements might also not be very accurate so who would I trust ?! 🙂
Normally, I am looking at Vas, Fs and Qts. Which of these are not to be trusted? What is considered an acceptable error margin?
I choose a sealed enclosure because it is more forgiving if I make calculation mistakes and in the same time is easier to build. Nevertheless, THIS 6th order design seems easy enough to build and I would be happy to do that if the volume would be OK. How would I actually compute the box in this case?
Makes perfect sense to have low pass filter at 150 Hz max. The filter I am using is adjustable up to 300 Hz and I identified a sweet spot at ~200Hz but maybe going even lower would be better. It makes perfect sense to get a high pass filter. Perhaps I could use the computer as a DSP to detect the ideal filtering in this case.
Normally, I am looking at Vas, Fs and Qts. Which of these are not to be trusted? What is considered an acceptable error margin?
I choose a sealed enclosure because it is more forgiving if I make calculation mistakes and in the same time is easier to build. Nevertheless, THIS 6th order design seems easy enough to build and I would be happy to do that if the volume would be OK. How would I actually compute the box in this case?
Makes perfect sense to have low pass filter at 150 Hz max. The filter I am using is adjustable up to 300 Hz and I identified a sweet spot at ~200Hz but maybe going even lower would be better. It makes perfect sense to get a high pass filter. Perhaps I could use the computer as a DSP to detect the ideal filtering in this case.
hey rbt.
I can see how you need to make a portable subwoofer, but there are two things causing that you´re failing.
1) 3-4l box with 3"-4" speaker will not make ANY usable subwoofer for home or open air usage. You need to go larger. Larger cone area, and more box volume. It really starts to work at about 10-12l and up, while still weak in eyes of most builders. Also expectations can get very high, but physics is physics...
2) Drivers
Those are quite weak. Look at tech specs and TS parameters. 0,75mm of Xmax is a joke for both vented and sealed boxes, and maximum sound pressure level. It´s next to nothing. No bass, at all.
You need to pass 5mm mark. 10mm is better, more is awesome.
This one in 10-12l bassreflex box tuned at 35Hz will do miracles for ya:
https://www.parts-express.com/tang-band-w6-1139sif-6-1-2-paper-cone-subwoofer-speaker--264-919
And I would greatly recommend going 8" or 10" in 20+l, as these are still quite compact (can take it with you in some larger bag).
I can see how you need to make a portable subwoofer, but there are two things causing that you´re failing.
1) 3-4l box with 3"-4" speaker will not make ANY usable subwoofer for home or open air usage. You need to go larger. Larger cone area, and more box volume. It really starts to work at about 10-12l and up, while still weak in eyes of most builders. Also expectations can get very high, but physics is physics...
2) Drivers
Those are quite weak. Look at tech specs and TS parameters. 0,75mm of Xmax is a joke for both vented and sealed boxes, and maximum sound pressure level. It´s next to nothing. No bass, at all.
You need to pass 5mm mark. 10mm is better, more is awesome.
This one in 10-12l bassreflex box tuned at 35Hz will do miracles for ya:
https://www.parts-express.com/tang-band-w6-1139sif-6-1-2-paper-cone-subwoofer-speaker--264-919
And I would greatly recommend going 8" or 10" in 20+l, as these are still quite compact (can take it with you in some larger bag).
I agree with Crashpc that other woofers will work better. It must however be possible to at least get some bass out of the SPH-100C.
You can do it! For example, follow this guide: http://www.artalabs.hr/AppNotes/LIMP_Tutorial_Version_2_4_English.pdf
All of them will be off when for example the suspension is stiffer than mentioned in the datasheet. It's difficult to state an acceptable error margin, but it will be in the range of +- 10%.
It's true that sealed boxes are more forgiving. Especially 6th order bandpass is critical about the accuracy of the parameters, which in practice means that you have to measure them yourself. You cannot calculate a 6th order bandpass box, but you can simulate it in WinISD. Plug in some values (volumes, tuning frequencies), play with them and see what happens. Note that increased complexity does not guarantee better results: it might be that a vented box outperforms a 6th order bandpass box, while vented is easier to design and more forgiving to errors.
That's a good idea! 150 Hz is a rough starting point for small speakers, in your case 200 Hz indeed might be better.
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