[hddummy]

If you saw my other thread on this topic (link) you would know that I'm trying to help my parents install a 5.1 system since they are renovating their house. I was having trouble with sub design/placement options because they are very picky customers. I was inspired by joorge's post in my thread about the parts express "boogieman" sub. I came up with something that I think will work decently well. It won't shake the house down by any stretch, but they are not audiophiles and they have hardly given much to work with.

We settled on a small space in a wall that is centrally located in the large open room. This space is about 10" wide, 11" deep and 36" tall. I plan to build a ported box to take advantage of every cubic inch they will give me. The whole thing will be flushed in the wall and finished with a cloth grill. This is not a large space, so my choices are very limited. I have selected a tang band 8" (link) from PE. I'll use two of them and a 30" folded slot port to give me a box tune of about 29Hz. This driver has great power handling, Xmax and a small VAS, which was key to this design. I'll top it off with a 500 watt BASH plate amp, but it will be running only 250W because the drivers will be wired in series for an 8ohm load.

Look for box design pictures later today.

 

[hddummy]

 

[hddummy]

The two horizontal members are just braces. I didn't bother to draw in hidden lines for open area.

I believe the net volume is 1.15 cu ft.

port is 8.5x1.5x30.5

i will also use 1" sonic barrier on all up or down facing surfaces to combat any resonance due to the long height dimension. This is also why i compacted the port into the top...to reduce the inside height.

 

[hddummy]

Modeled FR

 

[hddummy]

Yes, price is an issue. There is also the obvious quality and materials upgrade on the Rl-i to consider. However, I did model the RL-i 8" and the response models nearly identically to the TB W8 at the same power levels in the same box. That being said, the RL-i 8 would handle more power and allow the amp to deliver more power due to a better impedance configuration. My models still show the TB W8 as producing plenty of SPL, so I don't think the RL-i 8 is a justifiable cost upgrade. Thanks for the suggestion though!!!:T

 

[hddummy]

I also considered the CSS trio8. It is also a nice quality driver. I was thinking two in parallel, but it has twice the VAS of the TB W8 and I would be limited to one driver in the box size I have. It could produce the same SPLs as a single, but would be reaching excursion limits. With a pair of TB W8 drivers, I would be running much lower excursions. The plus side to the CSS is it is more efficient at the low end and can produce the same SPL as two TB W8s with half the power in the 20-80Hz region. So, the trade here is amplifier cost vs driver excursion/linearity.

 

[hddummy]

The TB's will output 105 db at 30 hz and drop off below that, not bad a a pair of 8's in 1 cu.ft.

That's what I'm saying. Also, a good value at $400 all said and done for custom built-in sub.

I am open to any suggestions for other 8" drivers. I'll be building the box soon, but I can hold off on cutting the hole for the driver until the end.

 

[hddummy]

Good advice...thanks!! I can add port length easy enough. I does drop my volume to 1.1 cu.ft. but that shouldn't make too much difference.

 

[hddummy]

I don't have a good number becuase the area is part of a large open floor plan. If I had to guess, I would put it at about 720 sq ft and consisting of a living room, breakfast area, kitchen and foyer. If you look in this thread, the sub will go in the wall directly below the right surround speaker. I know it is not ideal, but it will have to do.

 

[hddummy]

I did some modeling of the TB 8, you can get an extra 7 db at 20 hz if you lower the tuning to 27 hz and modify the HPF to 24.3 hz with 2 db of boost from 31 - 35 hz. Pink is with the default HPF and boost the amp comes with.

Although of built a few, I'm still learning the art of subwoofer design, so could you please explain how you decided on that particular boost level and freq. range. There are a lot of options to choose from with those boost tables, so why did you choose what you did and why not something different? Thanks for your help and time....I really appreciate it.

 

[hddummy]

so you didn't have a real reason behind the values you chose other than it was one notch lower in the boost tables.

 

[hddummy]

Gotcha. Anything lower and you driver it past Xmax at these power levels. By the way, what subwoofer design software is that?

 

[hddummy]

Small problem. If I extend the port the additional length to get 27Hz tune, the end gets too close to the center brace. I would have to keep 29, which isn't bad or extend the port to about 39 inches total length so that it ends at the brace. That is getting too long and port resonance could come into play. I could also reduce the port cross section, which would reduce the length requirement for a given tune. The question is, what are the dimensional limits on a slotted port. It is currently 8.5 x 1.5, if I go down to 1.25, my port length goes down to 31.25" and my port air speed is about 13m/s. I think I'd be good and I get the added benefit of some extra effective volume. I just don't know if that is too thin for the slot. Any help?

 

[hddummy]

I'm using Unibox right now, but I'll download WinISD and double check. I'm modeling with two drivers at 250W total input power. This is what I get. Of course this doesn't account for frequency response of the amp itself.

 

[hddummy]

yeah...the amp is 500....until you wire two 4ohm drivers in series, which of course drops it to 250, giving 125 to each driver.

 

[hddummy]

so, what do you show for port air speed at 250w? I guess that means the excursions you were showing was based on 500W as well...i can probably boost the low end a little more.

 

[hddummy]

I've been messing around with WinISD and several different combinations of Port Tune and Amp Boost/HPF settings. I think I have settled on a good solution. Thanks for your help and encouragement.

 

[hddummy]

I guess nothing is settled until it's built....right? In an effort to reduce port air speed, I've tweaked it more. Box volume 31l, tune to 28Hz, port dims: 1.375 x 8.5. Response changes marginally, port is a few inches longer, air speed drops to 20.5m/s.

 

[hddummy]

You bet! I hope to start making dust next week.

 

[hddummy]

OK..... I've made some progress, so here are some pics.

All the parts cut out:

The eventual home:

Dry fit check:

Port up close: