Voxel - a mini-sub+

[warllo]

barrymossel Hi, The setup has been working great with the parts I listed in my original post. I think it's plenty loud and I think it pushed the woofer to excursion. I also made my Voxel Passive and active so I that I would have more amp choices I didn't use the crossover however. The crossover you posted looks very similar to the one that PE sells which needs modification to work correctly so be careful with that. If you go to the reviews for the PE part a very nice forum member by the name of Millstonemike posted a guide on how to modify it so it works as advertised. I have not tested it but it seems like a very thorough write up. Hope this helps and enjoy your Voxel. It's a fantastic little beast.

[Millstonemike]

The PE power description for your 2 x15W + 30W amp is just one possible power spec. TI spec.'s the TPA3110 to drive 4 ohm loads. The TPA3118 is a great chip. However, the PCB design of any available, finished amp module is key (turn on/off thump, FR response etc.).

The 30W limitation is a thermal limitation. Nominally, you will reach 30W into 4 ohms for a sine wave with ~16V power supply. However, music is rarely as dense as a sine wave. I'd guess that music is 1/2 to 1/3 as dense from some measurements I've noticed. And any "heavy" passages can be "absorbed" by the chip/heat sink thermal inertia. So running at 24V should not be an issue for the amp (the TB sub is also limited). Just insure you have good airflow around the chip's heat sink. One trick for an active implementation is to position the PCB where the port's internal opening (air movement) flows over the heat sink.

[Sydney]

(1) With no port and only a 2.5" hole in the box,...2) With only 1 portion of the port installed, I heard no flapping...3) Re-installing the combined port, making sure to carefully align the port tubes, I again heard the flapping. ...4) Sealing this up, immediately minimized the flapping noise. It could still be heard, ...

Step 2 lowered the tuning, Step 3 lowered further Sealed removed the Resonator and raised the tuning and changed the rolloff.

[barrymossel]

I thought I would share what I found to power the Voxel Subwoofer. I have assembled the amp and power supply and it works great. Here is a photo of the components laid out after a dry fit test was completed.

https://www.amazon.com/dp/B00RUUSKS2/ref=twister_B01HCSR0O6?_encoding=UTF8&psc=1

https://www.amazon.com/TPA3118-Digit...s=60w+mono+amp

I was thinking of using the same amp, together with a filter pre-amp board. What's your experience with the TPA3118 on 24V for the Voxel?

I want to make my Voxel variant both active and passive btw.

[Chenevert]

Many thanks for the replies. I took apart the port and decided to take things one step at a time.

1) With no port and only a 2.5" hole in the box, I heard no flapping whatsoever even when driving the sub hard. That tells me I wasn't over-driving the sub.
2) With only 1 portion of the port installed, I heard no flapping whatsoever even when driving the sub hard.
3) Re-installing the combined port, making sure to carefully align the port tubes, I again heard the flapping. However, this time, since I was only experimenting, I hadn't sealed up the port/enclosure mating surface and it quickly became evident that air was leaking around that seal.
4) Sealing this up, immediately minimized the flapping noise. It could still be heard, but to a much lesser extent and only when pushing the sub hard.
5) I then placed a handful of poly fill near the port opening. The idea was to slow the air down a bit before entering the port. At this point, the flapping was again minimized to a very acceptable level.

Appreciate the guidance!

Separately, I am very pleased with the little 30W amp board. I originally bought it just to have something to test the voxel out with, however, it has exceeded my expectations. First, absolutely no "thump" when turning on/off. Seems to be extremely clean for such a cheap device. While the specs don't mention which amp is being used, I'm fairly confident from my experience with class D amp boards that it is using the TI 3110D2. I've used this on other projects so the specs seemed familiar. This little guy puts out a real 30W at 1% THD when using an 18V power supply (Currently using an old laptop supply). I have to turn the gain down to blend them with the OS mains that I am currently using.

[Sydney]

...With barely any gain, I start getting excessive port flapping (not sure if that is the technical term or not). Best way to describe it is when a car pulls up alongside you at a traffic light and all you can hear is the resonance. That's essentially what I hear coming out of the port.

If I seal up the port, the flapping disappears entirely. At low gain, I don't hear it either, but don't get much output from the sub either. ...

From this description, it acts like the effects of loss of cone control below tuning.
Have you tried playing a low frequency sweep?
Based upon this description - I would also try a HP filter that reduces the level of low frequency content below port tuning to reduce cone excursion.

[Chenevert]

Thank you for the reply. So it sounds like what I am hearing is indeed typical port noise? I was worried there was something else wrong. At least this points me in the right direction.

I'll pull the port out and make sure its sealed up properly. I hot glued the perimeter of the joint and then taped it with gorilla tape. When I stuff the port with fabric, I feel and hear no air coming out of the cabinet end. Seems that it seals up nicely.

The amp board simply takes a 3.5mm input. I am using a 2 RCA (L/R) to 3.5mm adapter coming out of the AVR. The amp board is just for testing as it was cheap and had variable gain.

I was thinking about putting some polyfill in near the port end to slow down the air a bit. yea/nay? Alternatively, I was thinking of modeling a larger diameter port with a U-shaped length?

[KEtheredge87]

I kept it a passive design, using an external 30W amplifier board.

Also... I dug into that amplifier's PE page a bit more. This amp says it's good for 30W into 8 ohms. That Tang Bang W5-1138SMF woofer is a 4 ohm load. You may not be running into issues with the amp overheating or drawing too much power yet, but you might in the future. Something to look out for.

[KEtheredge87]

Hey all (first post here). I am new to speaker building. So far built the OS kit (love them) and a modified design of the Zaph B3S currently being used as rear surrounds. In reading about the Voxel, I couldn't believe such a small box could hit 35Hz.... so of course I just had to build one.

I finished up my build yesterday. It's built to spec. I kept it a passive design, using an external 30W amplifier board. I have an issue that hopefully this forum can provide some assistance with. With barely any gain, I start getting excessive port flapping (not sure if that is the technical term or not). Best way to describe it is when a car pulls up alongside you at a traffic light and all you can hear is the resonance. That's essentially what I hear coming out of the port.

If I seal up the port, the flapping disappears entirely. At low gain, I don't hear it either, but don't get much output from the sub either. The 30W amp is being fed off of the Sub output of the HT receiver. Active crossover set to 100Hz.

What did I do wrong?

Hi Chenevert, Welcome to the forum! I built a Voxel sub that was Not to spec (used Dayton SA70 plate amp and did my own PVC port). I also had to deal with port noise, and my issue was largely to do with the port geometry itself. Paul's original design calls for two of the press in place ports arranged back to back so that you've got a flared port on the inside of the cabinet as well. How confident are you that the seal between the two tubes and the seal between the tube and the cabinet is good? If you've got any pictures of the setup you've made that may help as well. Port noise can be a tricky thing to deal with.

How are you getting from your AVR to your amplifier? Did you have to rig up some kind of RCA connector to + / - bare wire for that amp board? I know nothing about that amp board, but it sure seems like a tiny package to power a subwoofer, even one as small as the voxel. I say that because of the original design using a somewhat larger (physically) amplifier. I may be mistakenly equating physical size with space for larger capacitors and better amplifier components.

Hang in there, and good luck!

[Chenevert]

Hey all (first post here). I am new to speaker building. So far built the OS kit (love them) and a modified design of the Zaph B3S currently being used as rear surrounds. In reading about the Voxel, I couldn't believe such a small box could hit 35Hz.... so of course I just had to build one.

I finished up my build yesterday. It's built to spec. I kept it a passive design, using an external 30W amplifier board. I have an issue that hopefully this forum can provide some assistance with. With barely any gain, I start getting excessive port flapping (not sure if that is the technical term or not). Best way to describe it is when a car pulls up alongside you at a traffic light and all you can hear is the resonance. That's essentially what I hear coming out of the port.

If I seal up the port, the flapping disappears entirely. At low gain, I don't hear it either, but don't get much output from the sub either. The 30W amp is being fed off of the Sub output of the HT receiver. Active crossover set to 100Hz.

What did I do wrong?

[ScenesFromAHat]

I'm always surprised at how tiny the chip amps are

[Wolf]

The driver consumes very little volume depending on the driver. If you must subtract it, I would measure the magnet assembly, and subtract that from the volume of the box.

Later,
Wolf

[skatz]

Does somebody know how to calculate the volume of the speaker. I now have a 7.5 liter enclosure but i think the speaker volume and the bass pipe volume also counts so i have to add the volume by the speaker enclosure.

Example--> calculated box enclosure = 7.5 liter
Speaker = 600ml
Bass pipe = 400ml

So my total volume of the enclosure must be 8.5 liters!

But how do i know the speaker volume?

If I understand your question, the volume of the driver itself and the port tube normally subtract from the volume of the enclosure to give the net volume.

[warllo]

I thought I would share what I found to power the Voxel Subwoofer. I have assembled the amp and power supply and it works great. Here is a photo of the components laid out after a dry fit test was completed.

https://www.amazon.com/dp/B00RUUSKS2/ref=twister_B01HCSR0O6?_encoding=UTF8&psc=1

https://www.amazon.com/TPA3118-Digital-Amplifier-Board-1X60W/dp/B01M4MP2X1/ref=sr_1_7?s=industrial&ie=UTF8&qid=1490115273&sr=1-7&keywords=60w+mono+amp

[Chris Roemer]

yup