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Old 19th December 2012, 04:01 PM   #201
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My ttqwt is loudest pointing towards the corner, but sounds the best pointing towards the entertainment center.
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Old 20th December 2012, 12:31 PM   #202
uptime is offline uptime  United States
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Originally Posted by permo View Post
I am moving this subwoofer into my big home theater in the basement and looking at placement options. I think I already know the answer, but it is it optimal to face a horn subwoofer so the throat is pointed up (towards the ceiling) in a corner? I am thinking that would not be good.
Permo, always good to hear from you. A while back I had a number of individually controlled drivers in various boxes. Something like 16 different drivers from 6 different manufactures. Each in their own uniquely designed cases, all with their own amp and their own channel, running through three 5.1 sound cards, into a single laptop running reaper. This allowed me complete control of crossover's, delay, fir, eq, etc. Plus I had a few mic's thrown into the mix for testing.

What this allowed me to do was test all kinds of scenarios. What I found is that if you run all of them at the same time, it's really loud. ��

Just kidding. Seriously, what I personally found is that if your running a whole lot of drivers, it seems best to face them all forward including the sub. Create a very large sound wall with lows on the bottom, mids in the middle and highs above.

With fewer speakers it seems best to move more towards highs facing up, mids forward and bass down. If using only a single full range driver, the best sound in most rooms seems to be with the driver facing up and the port facing down, with the speakers at least 2-4 feet (at least a meter) from the nearest walls.

None of this is scientific, just listening and then tuning in each of the many test scenarios. What I learned is that I am crazy... No really, that I have a very patient wife because all of this was done in the family room over a period of weeks.

Seriously, what I learned is that the more drivers you have, the less control you get of the sound stage, and that the lows like to live, well low to the ground, and that the highs love to be, well, high, where they can bounce around. None of this is really that much of a revelation based on how people have been building speakers for years, except in the case of the full range and three way drivers. Bass seems to work best if out in the room and facing down or if you have a lot speakers you are trying to match, as close to the other speakers as possible, and facing forward if the speakers are close to any wall. And always two subs, one on each side as close to the mids/highs as possible. Anything else gives you a lot of reflections that are really hard to tune away or know what is actually going on.

So that would be my starting point. Down depending on where your other speakers are and how many have and out in the room, or forward if the speakers are close to walls. Because as any good engineer will tell you, the best answer is it depends. And in my case anyway, I have the two very large tubes you helped me build facing forward right next to the tall ribbons out in the room away from the walls. I would have had them facing down, but this ended up not being so spouse friendly. I did try up as well, but lost all of the bass.

Since you are so good at designing and building tubes, you should try building/designing and sharing one for us that faces down with the option of facing forward. Maybe some kind of removable panel that slides either into the front or can be repositioned to the bottom. This would allow us to use them in either position AND make them at least somewhat spouse friendly.

Let me know if my ramblings were not clear and I would be happy to answer any other questions.
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Old 20th December 2012, 01:15 PM   #203
uptime is offline uptime  United States
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Originally Posted by bjorno View Post
Hi,

Thank you for your feedback, always nice to read.
Sealed subs are always a good idea but I prefer a single T-TQWT as main sub
together with a couple of smaller ( 15-20 L) lateral placed closed box subs.

Submitting a picture of a smaller T-TQWT using a favorite driver, the Wavecor
-SW178WA01 that provides IMO,IME outstanding SQ (Music use).

b
Love it!

I would like to get your take on the down facing / forward facing option I suggested to permo. Do you think that it is possible?

Also, I went looking for the wavecor and here in the states it seems a little hard to get. Any suggestions of other similar drivers that you like that would be pretty easy for me to get?
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Old 20th December 2012, 01:24 PM   #204
uptime is offline uptime  United States
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Love it!

I would like to get your take on the down facing / forward facing option I suggested to permo. Do you think that it is possible?

Also, I went looking for the wavecor and here in the states it seems a little hard to get. Any suggestions on other similar drivers that you like that would be pretty easy for me to get?
Oh, and I would like to get your take on group delay. It seems that it is really hard to create a T-TQWT with low group delay. Something about physics getting in the way.

When designing T-TQWT's, how does everyone go about reducing group delay so that it is not noticeable on the lower end? What are the tricks?
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Old 21st December 2012, 04:07 PM   #205
tb46 is offline tb46  United States
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Hi permo and Uptime,

No time at the moment: please, revisit Post #123 in this thread: Tang Band Tang Band W8Q-1071F 8 X 12 box reccomendation
Also, bjorno has posted frequently on group delay, basically the T-TQWT does not have a problem.

Regards,
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Old 22nd December 2012, 03:27 PM   #206
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Default Bjorno

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Originally Posted by tb46 View Post
Hi bjorno,
You put so much work into these designs, and help so many builders, you deserve a little help every now and then. :-)
I would like to echo what TB said here. Bjorno you are one of the most helpful individuals on diyAudio and your efforts deserve recognition and appreciation.

Thank you, You're a bad ***!

-Matt
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Old 23rd December 2012, 12:03 AM   #207
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+1!
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Old 2nd January 2013, 04:39 AM   #208
uptime is offline uptime  United States
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Originally Posted by tb46 View Post
Hi permo and Uptime,

No time at the moment: please, revisit Post #123 in this thread: Tang Band Tang Band W8Q-1071F 8 X 12 box reccomendation
Also, bjorno has posted frequently on group delay, basically the T-TQWT does not have a problem.

Regards,
Thanks so much Oliver. I understand it better now. Am I right in saying that group delay isn't really a problem because at the length of the quarter wave tube the signal is 90 degrees out of phase and so it reduces/cancels out the potential group delay?
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Old 10th January 2013, 01:56 AM   #209
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by uptime View Post
Oh, and I would like to get your take on group delay. It seems that it is really hard to create a T-TQWT with low group delay. Something about physics getting in the way.

When designing T-TQWT's, how does everyone go about reducing group delay so that it is not noticeable on the lower end? What are the tricks?
Hi uptime,All

Been busy over the New Year..
At onset:I think Gldy is easy to handle for quarter-wave-boxes as long as the (sub) passband phase is smooth and stays within ~1/f and don't cause ripple when integrating with the main speakers.

In common rooms: Up to ~3 dB narrow-band dips can be tolerated below~150 Hz(more when (sub) LF Pitch actually is heard,i.e. when needing more than 3 cycles to be audible RT30(RT 60) typically> 200 mS(treated monitoring room) but watch out for peaks of similar size that are much audible when interacting with the onset of the Mains. Off-band ripple must (IMO) be suppressed at the origin of occurrence by using damping material or clever introduced bends....

Here are some of my Notes concerning( or closely connected) to this matter..

Here: An easy reading of introduction to Psychoacoustics:

http://kurser.iha.dk/eit/eaku/litt/Psychoacoustics.pdf

b
Attached Images
File Type: jpg Gldy-extrapolation_Vertical Localisation-of-Woofers.JPG (493.8 KB, 146 views)
File Type: jpg Bech_delay-ripple_gldy-sub1-9254.JPG (671.8 KB, 142 views)
File Type: jpg Transient_Pitch.JPG (902.7 KB, 139 views)
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Old 15th January 2013, 03:48 PM   #210
uptime is offline uptime  United States
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Quote:
Originally Posted by bjorno View Post
Hi uptime,All

Been busy over the New Year..
At onset:I think Gldy is easy to handle for quarter-wave-boxes as long as the (sub) passband phase is smooth and stays within ~1/f and don't cause ripple when integrating with the main speakers.

In common rooms: Up to ~3 dB narrow-band dips can be tolerated below~150 Hz(more when (sub) LF Pitch actually is heard,i.e. when needing more than 3 cycles to be audible RT30(RT 60) typically> 200 mS(treated monitoring room) but watch out for peaks of similar size that are much audible when interacting with the onset of the Mains. Off-band ripple must (IMO) be suppressed at the origin of occurrence by using damping material or clever introduced bends....

Here are some of my Notes concerning( or closely connected) to this matter..

Here: An easy reading of introduction to Psychoacoustics:

http://kurser.iha.dk/eit/eaku/litt/Psychoacoustics.pdf

b
Wow. Thank you so much!

It is a very interesting read indeed. Some of the publications you reference I have read before, but most of it was new for me. I also completely read and re-read a few of the other related content and notes you have in there as well. I have not completely digested all of it yet, but I am beginning to understand our ears just a little better, and why I continue to be so fascinated about reproducing the low end properly. I of course love all properly produced content across the entire spectrum, but with good source material, proper delays and synchronization of content it does seem possible to create a completely new and immersive experience.

I would love to communicate with you one on one some time (email, private messages, etc.) It might just change the world and get us out of the dark ages of audio we are currently in.
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