Helo! I have extensive experience in construction BP 4th and will give you some friendly advice. Turn the speaker the other way around to cool it down. Sealed chamber must be smaller. Make simulation for speaker as sealed box. The volume should be such that give xmax at doubled nominal power. For better result, as posible, use a birch plywood 3/4 inch. Optimal port area is 2/3 Sd (effective diameter). Never fold the port! Divide the port in half with a vertical partition (rigidity and increased self-resonance of the port). Tuning frequency must be 48Hz -3dB. Do not symetrycal or flat response in simulation, the left edge must be higher. Make a 8dB efficience at peak. Electrical polarity will be reversed. All the best!

Hey Marius, it's good to see these techy guys commenting on your channel, also good to hear you are ditching that silly plate amp. Thumbs up on the video.

Good job over all ! Keep going !

I have a old Boston Acoustics PV400 4th order bandpass home theatre subwoofer. The enclosure is in the shape of a skyscraper, 10" x10" footprint and 20" tall and uses a little 7" woofer. Completely sealed with two down firing ports (it sits on little 1" legs) . One of the most unique little subs I have ever seen and for a small sub it cracks really hard, better than some high quality 10s I've owned. It sounds far better than it should. Awesome little score. Actually have two of them.

I built a 4th order for a single 8 and never modeled it, but it's a 3:1 and it's had really good bandwidth, also on the port I rounded over the edges and cut a 45 for the curve in the port and there is absolutely no port noise, maybe I just got lucky but it seems like 4th orders or very dependent on your sealed side, even changing .1 cft changes the sound pretty drastically

The problem with bandpass is that if you want a wide flat frequency response (30-60Hz) you won’t get the SPL. In that case you’re just building a complicated, heavier ported box. Bandpass is great for a narrow loud frequency. Look at that response at 5:52 +1 db. This same driver in a ported box will challenge that same response

4:47, get a UMIK-1 and your statement here will change. I've got a number of recordings/videos and it picks up the bass just fine. Even the subsonic frequencies under 20Hz it records faithfully. It's accuracy is lower the lower you play under 20Hz but it still does a great job under 20Hz. For this subwoofer though the UMIK-1 would perfectly record any sound it puts out.

Hi there, Nice finish on the box, and very smart that you made a seperate chamber for the amplifier. Some tips on your concerns: to lower the port noise you could try to place some 45 degree pieces in the corners of the port to help guide the airflow. More importantly, roundover the edges of the port pieces, both inside and outside of the box to avoid any sharp edges that will create turbulence/noise. I also noticed that you did not continue the port length example through the baffle, which is also part of the port. For best SQ, the UM8-22 however is best used in a sealed box. Any resonant system (ported design), prefers a driver with a Qts of 0.5 or below to improve damping. The QTS of the UM8 is already above that, but in a 15L box, the QTS increases to almost 0.9. Something like the similar priced/capable RSS210HO would be better suited for this application. It has less Xmax, but with the 200W amp, that should not be an issue. I think you already mentioned this in your ported subwoofer design video, why not appply it? I also understand you dont use bracing for this small box, but a thinner MDF sheet is used for sealing the rear chamber. This rear chamber also has very high preasure levels, and this back panel has the largest span width! This is by far the weakest point of the box, which could harm Ql. (same goes for the port pieces) If you want the best matching between WINisd and your measurements, also change Qa, Ql and Qp to realistic values. You can even turn on transmission line simulation to see how the port resonances influence the frequency response.

Bandpass chassis: Magnet: mid to high power. Membrane: stiff as f*** but light as a feather. Heavy membrane let the box get small but also the impulsivity gets slow and queasy. 8:30 The longer a port gets, the higher the problems (in case you want a BP that sound good and not only is loud). This one is too long for a good sounding BP. I think this is not a good chassis for a BP. The numbers may say that you can use it but there is more than a (compiled) perfect frequency response. I have a Monacor SPH-250 CTC in a BP. The numbers say it would better fit in a horn or TL but the sound you get out of this box is awesome. It has 4 ports with 7 cm diameter, 18,5 cm long (on the other side the box is 78 litres big but therefore needs not much power for high volume)

I made one 12" ported height 1" x 12" Vent air velocity is under 17m/sec as per winisd. But still I got port noise. One reaon could be the port height too small compared to width.

Proper design for a box that has good freq response and flat enough bandwidth to minimize listening fatigue will always have a smaller ported chamber than the sealed chamber, and the subs ebp should be

I'd love to learn your perspective for a car audio subwoofer 6.5" and slimmest closed enclosure possible.

Nice build. though My first thought was wondering how you'll replace the woofer if it somehow breaks... tbh, I would be scared AF of spending the time and money building a box like this if I didn't design an access panel of some kind (Maybe making the back of the amp chamber removable) to allow the woofer to be replaced non-destructively btw, @ 0:36 you can hear the Camera smack the cone, lol

Hey man I just wanna say I’ve talked to a lot of car audio gurus who specialize in bandpass enclosures and are known to build proven boxes that hit high spl numbers, all I can tell you is the magic formula that seems to work every time is keeping the sealed chamber small and ported chamber big, much bigger. I’ve seen guys shrink from 1.5cubes sealed to 1 cube sealed and gain massively on low end response and high end response. (Single 12). For 15s you want around 1.5-1.7 cubes sealed. Don’t ask me why this works, but throw away most of the information you get from loudspeaker cookbook it’s outdated

Unrelated question, can I perform spl measurements on a tower speaker before I install the port(tuned for 40hz )( mid and tweeter are sealed) ? If yes should I measure without hole or with hole. (Port is out of stock rn. )

I cant figure out why in WinISD.. when I specify a port to 6" wide.. in a 2cuft box.. it says 120" port length. What? But then.. when I add 2 ports.. each 6" wide.. it doubles the length?? How does that make sense? I've added a 2nd 6" port.. that should dbl the port volume with 2.. so why does the length now double? Or do the calculations get screwed up somehow when ports are too much volume?

That port looks awfully small for a 4th

Hey Marius, as far as I know, you are from Romania. Do you live there now or in any other country??? Just curious to know.

Hey bro. Build a cubo box

I made a 4th order with an ultimax 8 and it slams.

Where's the "whaaaasap guys"? At its in the middle lol

Build a double reflex box, they sound so nice. I don't like bandpass subs

Damping material is a waste on subwoofers