Designing Tang Band 881si Enclosures

[guangui]

Originally Posted by xrk971

Stuff polyfill in triangle and line behind driver and top. Then add polyfill stuffing behind driver if needed to reduce hf from leaking out terminus. Looking good!

Well, after talking it over with a good friend; who introduced me to DIY. I have decided to completely line with wool and use poly-fill in +/- the last third of the closed area. I will probably have to do them over, as by lining I have taken away about 3/8" from all sides. Since my main goal was to learn, I'm definitely learning of what might be errors. This is totally different from following someone else's design, which I'm used to. Will finish them, hear them and take measurements. The redesign or rebuild accordingly. Maybe I don't have to do anything, or maybe I have to increase volume, we'll see. If needed, I can take the driver out and fill more through the driver cutout.

BTW, thanks for advising about making a mic and HOLMImpulse software. I have ordered the parts to make the mic. Instead of using Panasonic's WM-61A, I will use PUI's POM-3535L-3-R. Their specs are basically the same, but the freq. range is slightly different. Panasonic's is 20 to 16k Hz, while PUI's is 0 to 20k Hz. Most probably I will never have to measure less than 20 Hz, but for $0.50 extra why not have the capacity to measure under 20 Hz for window rattling subs.

[guangui]

Here is one of the enclosures semi-finished, waiting on drivers, also need to fill some areas and paint.

[gychang]

Originally Posted by guangui

Here is one of the enclosures semi-finished, waiting on drivers, also need to fill some areas and paint.

is there a vent on the bottom, not clear on the pics.

[guangui]

Originally Posted by gychang

is there a vent on the bottom, not clear on the pics.

Yes, on the middle pic at the bottom you can see a white area, that's the port. It is equivalent in size to the calculated port tube.

[xrk971]

That's a really small vent for a Weems's pipe - the calculator you used actually had a round tube as outlet vent? What is the cross sectional area from the calculation? It should be at least as big as the driver Sd or else you will be getting a MLTL. My guess is that with all the felt you have and how small the vent is, the bass output will be really reduced. But it could be that you were going for lower freq extension hence the vent is small to get MLTL.

[guangui]

Originally Posted by xrk971

That's a really small vent for a Weems's pipe - the calculator you used actually had a round tube as outlet vent? What is the cross sectional area from the calculation? It should be at least as big as the driver Sd or else you will be getting a MLTL. My guess is that with all the felt you have and how small the vent is, the bass output will be really reduced. But it could be that you were going for lower freq extension hence the vent is small to get MLTL.

So much felt was an error on my part, forgot to add the decreased volume, due to the 3/8" felt, to the overall dims of the enclosure. The round port is 1.26 sq.in., mine is 1.2575 sq.in. Length is equal for the calc rounded port and my rect port. If not satisfied with the end result I will recalculate and redo.

Yes, lower freq. ext. was part of the plan.

[guangui]

So, I finished them, they are not the prettiest, as my plan is to once finished, if they work to go ahead and make using plywood. They are not your typical sound, and I don't mean that in a bad way, though jury is still out regarding vocals. Imaging and soundstage are very good, larger than the uFonken with the same W3-881SI driver. The uFonken sounds more balanced, more rounded.

These design improves on imaging, soundstage, and more detailed highs. Bass was less than on the uFonken, and the sound was more forward. The uFonken was warmer. Toeing-in the speakers so they crossed in front of my seating position, instead of being directed at me, improved the sound, the speaker became more behaved. dB's increased dramatically, much louder enclosure than the uFonken.

What really is baffling me is the vocals, they are very detailed, but "s" is more pronounced than with the uFonken, in part a good thing as it gave vocals more dynamism, but too much of a good thing is bad. Vocals also sound sort of "hollow".

There is room for improvement, and I think that my mistake was as to not take the wool liner thickness in consideration, I needed to add about 3/4" to width and depth, not so much to height. I might be able to correct somewhat by adding more poly-fill. Overall, I'm happy with my very first design, and back to the drawing board to correct dimensions. Also, ordering foam core cutters for bevels, straight lines, and circles; it will make life much easier.

Not going to change the drivers back to the uFonkens for the time being, I want them to break-in, as they only have about 2 hours playtime, to see if the sound gets better.

[cogitech]

Take it with a grain of salt, because others seem to baby these drivers, but I found that my pair benefitted from "almost abusive" breakin-in. I pushed the driver excursion to the point just before they started to sound like crap and then I let them rock like that for a while. I purposely enhanced the bass in the signal to force the cones to comply or die. I was not "stupid" about it, but I was not gentle.

[guangui]

Originally Posted by cogitech

Take it with a grain of salt, because others seem to baby these drivers, but I found that my pair benefitted from "almost abusive" breakin-in. I pushed the driver excursion to the point just before they started to sound like crap and then I let them rock like that for a while. I purposely enhanced the bass in the signal to force the cones to comply or die. I was not "stupid" about it, but I was not gentle.

Played them loud for about 1/2 hour, and they were sounding crappy, but after that time I got "scared" of hurting them, and turned down the volume. At no time I went past their RMS limit, as I was using a DTA-1 T-Amp (8-10 WPC @ 8 Ohms). But, afraid they would over excursion.

[cogitech]

Just short of sounding crappy is where you want them. Big cone movement but without any garble.