Looking for some advice on building a HT subwoofer - AVS Forum
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post #1 of 66 Old 11-12-2012, 08:36 AM - Thread Starter
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I am standing on the sliippery slope of deciding on whether to build a DIY subwoofer for my home theatre or not.
I possess the carpentry skills but not the technical ones.
I am looking at what I would need to build a subwoofer that would work well for my approx. 3200 Cu Ft enclosed theatre room. The subwoofer would be out of plain sight behind the curtain to the right of the TV in the pictures. The door way would allow me to have it so the "mouth" of the enclosure would face into the room.
The specs that I would be working with would be so I can get it into place through the 23" doorway.
I would like it to be within the following measurements if possible.
78 long x 36 high x 18 wide with the "mouth" being on the 36" side near to the end.
Am I looking at a tapped horn design here? The more I have read the more confused I seem to be getting.
The enclosure fabrication is not a problem but I am looking for some design help as well as component selection and a parts list.
My budget is around the $500-600 mark.
Is this a do-able project?
Here are some pictures of the space I am looking at using. The Velodyne sub sitting there is facing the way I would like the new sub to face but the Velodyne would be replaced of course.



Here is a picture of the doorway with the curtain drawn back. This would be closed normally.



The space behind the TV, components etc.



Another shot showing the Velodyne in the doorway facing the theatre room.



Any help or suggestions would be much appreciated.

What items would I need for this project?

Driver(s)
Enclosure materials
Plate amp?
Wire
High pass filtering?
Equalization?

I am not worried about the finish per se as it will be hidden.
I am looking to match my SVS PC12-NSD or better for sound if possible.

All suggestions are welcome.

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #2 of 66 Old 11-12-2012, 11:28 AM
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I think you are horn territory with that room size and budget. The THT LP http://billfitzmaurice.info/THT.html fits those dimensions, though I'm a bit confused by your description of how you want it oriented. I'm assuming you are going to lay it behind the screen with the mouth toward the safe. You would be out around $140 for the DVC 15 driver + 140 for a 300w plate amp + $15 for plans + $100ish for wood.

That's a really pretty room you have.
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post #3 of 66 Old 11-12-2012, 11:50 AM
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Look into an F-20, THT or a THT LP to see what form factor works for you. The THT I have can be made anywhere from 18 to 36" wide...yours would be 22.5". Also you don't want it firing into the room. It is supposed to be 18" from a wall/ceiling/floor. Mine is down firing on 18" legs.

These all put out more output than most people can tolerate over 20-25 hz. Below 15-20 hz there is no/little output. You don't have to high pass the THT, but eq or Audyssey is a good idea. Budget is easily met and that includes the amp.

Current HT: HTPC-->Epson 5010 projector-->135" screen, BFM TLAHs x7 & THT
Build log: DIY rotary sub for contemporary HT in 100 year old house?
Andreas' Slow Rotary Sub build
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post #4 of 66 Old 11-12-2012, 11:57 AM
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+1 for the THT.

Here's a vid to give you an idea of what they can do.

EDIT: And another Vid

dbl

Let's all go to the lobby
....Let's all go to the lobby
........Let's all go to the lobby
............To get ourselves a treat!
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post #5 of 66 Old 11-12-2012, 11:58 AM
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nice theater workmanship there!

i did chuckle a bit when you pulled back the curtain. time to remedy that. :-)

your specs match very closely with these subs:

http://www.avsforum.com/t/1404092/wanted-big-bass-big-room-open-to-an-even-bigger-room-with-lots-of-windows/60#post_22034926

scroll up for driver and dimensions.

10cvx15 driver and a behringer amp inuke3000dsp (for both high pass and eq, it is really easy to use) like chasmain used is good. a smidgen over your budget and the end firing is just fine, just give it 1-2 feet of space to breath.

if you need to fudge the dimensions by a hair here or there it won't kill performance. the most important measurements are right around the woofer.

for the cost of another driver, you could even double up and stack the cabs, although one should be enough for most anybody.

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post #6 of 66 Old 11-12-2012, 12:12 PM
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dbldare, your subs are completely overloading your camera's microphone causing all kinds of distortion in the videos.

Listen. It's All Good.
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post #7 of 66 Old 11-12-2012, 01:37 PM - Thread Starter
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Quote:
Originally Posted by nograveconcern View Post

I think you are horn territory with that room size and budget. The THT LP http://billfitzmaurice.info/THT.html fits those dimensions, though I'm a bit confused by your description of how you want it oriented. I'm assuming you are going to lay it behind the screen with the mouth toward the safe. You would be out around $140 for the DVC 15 driver + 140 for a 300w plate amp + $15 for plans + $100ish for wood.
That's a really pretty room you have.
Thanks for the reply. OK. So I was thinking of orienting the opening to fire into the room but that isn't a good idea? Won't that end up distorting the sound back behind the TV? Firing it towards the safe is fine then? That would work for the budget for sure.

Quote:
Originally Posted by AndreasMergner View Post

Look into an F-20, THT or a THT LP to see what form factor works for you. The THT I have can be made anywhere from 18 to 36" wide...yours would be 22.5". Also you don't want it firing into the room. It is supposed to be 18" from a wall/ceiling/floor. Mine is down firing on 18" legs.
These all put out more output than most people can tolerate over 20-25 hz. Below 15-20 hz there is no/little output. You don't have to high pass the THT, but eq or Audyssey is a good idea. Budget is easily met and that includes the amp.
I will have to check out the F-20 but I am a little confused. The THT LP is the low profile of the THT correct? What is the F-20 compared to the THT?
Quote:
Originally Posted by LTD02 View Post

nice theater workmanship there!
i did chuckle a bit when you pulled back the curtain. time to remedy that. :-)
your specs match very closely with these subs:
http://www.avsforum.com/t/1404092/wanted-big-bass-big-room-open-to-an-even-bigger-room-with-lots-of-windows/60#post_22034926
scroll up for driver and dimensions.
10cvx15 driver and a behringer amp inuke3000dsp (for both high pass and eq, it is really easy to use) like chasmain used is good. a smidgen over your budget and the end firing is just fine, just give it 1-2 feet of space to breath.
if you need to fudge the dimensions by a hair here or there it won't kill performance. the most important measurements are right around the woofer.
for the cost of another driver, you could even double up and stack the cabs, although one should be enough for most anybody.
So it would be alright to build just the one of these? I saw this thread but thought he built a pair because one wouldn't be enough. I would like the new sub to compliment my SVS sub or vice versa. My head is starting to spin again....wink.gif
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Originally Posted by dbldare View Post

+1 for the THT.
Here's a vid to give you an idea of what they can do.
EDIT: And another Vid
dbl
Thanks for the links. I will give them a look.

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #8 of 66 Old 11-12-2012, 01:50 PM
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The F-20 is a different design than the THT or the THT-LP. Both are horns, but Bill Fitzmaurice designed the THT's and our own LilMike designed the F-20. I have to say, both are very capable, and the directions to build on both are easily available (F-20 just search the build thread here, and BFM designs for the THT). I had a pair of F-20's and the midbass on them is prodigious. Truly remarkable for a first sub if you are willing to give up the space. Bill's THT is right up there with it as well smile.gif

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post #9 of 66 Old 11-12-2012, 01:50 PM - Thread Starter
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Quote:
Originally Posted by dbldare View Post

+1 for the THT.
Here's a vid to give you an idea of what they can do.
EDIT: And another Vid
dbl

OMG!!! eek.gif I just watched your videos. Your dog must need anti-anxiety meds now.

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #10 of 66 Old 11-12-2012, 02:00 PM - Thread Starter
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Quote:
Originally Posted by beastaudio View Post

The F-20 is a different design than the THT or the THT-LP. Both are horns, but Bill Fitzmaurice designed the THT's and our own LilMike designed the F-20. I have to say, both are very capable, and the directions to build on both are easily available (F-20 just search the build thread here, and BFM designs for the THT). I had a pair of F-20's and the midbass on them is prodigious. Truly remarkable for a first sub if you are willing to give up the space. Bill's THT is right up there with it as well smile.gif

I now see the difference between the THT and the F-20. I think the F-20 is too big for the space I have behind the curtain. I still need to access the safe as well so perhaps the THT LP is looking like the way to go.
Should I be looking at a plate amp or stand alone as previously suggested? Does it matter which style I use? Asthetics doesn't matter.

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #11 of 66 Old 11-12-2012, 02:18 PM
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"So it would be alright to build just the one of these? I saw this thread but thought he built a pair because one wouldn't be enough. I would like the new sub to compliment my SVS sub..."

yes. one horn will blow the svs away. at best, the svs may be used for a second source in the room in order to help minimize nulls.

everybody ends up doubling down, he just did it right from the start. :-)

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post #12 of 66 Old 11-12-2012, 02:24 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post

nice theater workmanship there!
i did chuckle a bit when you pulled back the curtain. time to remedy that. :-)
your specs match very closely with these subs:
http://www.avsforum.com/t/1404092/wanted-big-bass-big-room-open-to-an-even-bigger-room-with-lots-of-windows/60#post_22034926
scroll up for driver and dimensions.
10cvx15 driver and a behringer amp inuke3000dsp (for both high pass and eq, it is really easy to use) like chasmain used is good. a smidgen over your budget and the end firing is just fine, just give it 1-2 feet of space to breath.
if you need to fudge the dimensions by a hair here or there it won't kill performance. the most important measurements are right around the woofer.
for the cost of another driver, you could even double up and stack the cabs, although one should be enough for most anybody.

I priced out the amp and driver and they are " a smidgen over my budget" for sure. With materials etc. it would be double my budget. What other driver and amp would work in a similar cabinet at about 1/2 the cost?
Would http://www.parts-express.com/pe/showdetl.cfm?partnumber=295-466 workfor the driver?

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #13 of 66 Old 11-12-2012, 02:55 PM
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Quote:
Originally Posted by LTD02 View Post

"So it would be alright to build just the one of these? I saw this thread but thought he built a pair because one wouldn't be enough. I would like the new sub to compliment my SVS sub..."
yes. one horn will blow the svs away. at best, the svs may be used for a second source in the room in order to help minimize nulls.
everybody ends up doubling down, he just did it right from the start. :-)

Haha, no not right from the start, I made it a week, Lol.

The f-20 is a little bigger but for the budget, it is close to impossible to beat if you have the space. having to move it out of the way isn't fun but doable, I am younger and didnt have much problem at all really, it is a good workout though smile.gif

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post #14 of 66 Old 11-12-2012, 03:04 PM
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oh, i thought you were at $600 for driver and amp. i suggested a $650 rig with massive performance, eq, and upgrabability.

if that missed the target, i'm sure that there is something else.

horns and drivers work together, they can't just be interchanged at random.

sounds like a tht lp might be what you are looking for. most plate amps have a high pass filter built in around 20hz, so even though folks will say that you don't need a high pass on it, that is because it is already built in.

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post #15 of 66 Old 11-12-2012, 03:22 PM - Thread Starter
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OK. Now I have a bunch of questions. I do like the ability for upgrading etc but I found that the amp and driver you mentioned came to about $850 not including shipping and taxes etc.
If I understand it correctly the Tapped Horns work well with lower wattage amps ,no? Something like a 300W BASH amp suitable for this application or should I be looking at something that is seperate?
Where do I start with the design of this? Do I find a driver and work from there or do I start with the dimension contraints and find a driver to work within those? I think I got the above mentioned driver from the THT LP design page. I don't know where to begin this project.....

My Vintage style Home Theatre Build thread:
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post #16 of 66 Old 11-12-2012, 03:29 PM
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The THT has max excursion at 23hz or something like that, so low freqs don't have to be filtered out. The caveat is that you can go to a higher voltage if you high pass at 25 hz. Still, there is plenty of output even at the lower voltage.

LTD is right on with recommendations so definitely heed his advice!

Current HT: HTPC-->Epson 5010 projector-->135" screen, BFM TLAHs x7 & THT
Build log: DIY rotary sub for contemporary HT in 100 year old house?
Andreas' Slow Rotary Sub build
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post #17 of 66 Old 11-12-2012, 03:32 PM
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If you want to go the THT route you have to buy the plans. There is more detail there, but you can also check out build threads here or on the BFM forum.

Current HT: HTPC-->Epson 5010 projector-->135" screen, BFM TLAHs x7 & THT
Build log: DIY rotary sub for contemporary HT in 100 year old house?
Andreas' Slow Rotary Sub build
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post #18 of 66 Old 11-12-2012, 03:49 PM - Thread Starter
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Quote:
Originally Posted by AndreasMergner View Post

The THT has max excursion at 23hz or something like that, so low freqs don't have to be filtered out. The caveat is that you can go to a higher voltage if you high pass at 25 hz. Still, there is plenty of output even at the lower voltage.
LTD is right on with recommendations so definitely heed his advice!
Do you mean that a higher wattage amp will "over drive" the speaker at the lower frequencies if it isn't high pass filtered at 25 Hz? Sorry for the noob questions but I don't understand some of this stuff, to put it mildly.
I see that the plans are available for purchase for a low cost on the website but do they include driver suggestions as far as you know?

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #19 of 66 Old 11-12-2012, 04:21 PM
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"OK. Now I have a bunch of questions. I do like the ability for upgrading etc but I found that the amp and driver you mentioned came to about $850 not including shipping and taxes etc."

ah, the price differential may be because you are in canada. i didn't catch that the first time around.

"If I understand it correctly the Tapped Horns work well with lower wattage amps ,no?"

tapped horns are more efficient at reproducing the lower notes, so in some sense that is right. however, the amount of power that a driver can use is limited by its thermal properties and its excursion properties.

"Something like a 300W BASH amp suitable for this application or should I be looking at something that is seperate?"

something like that could work, you'd just be losing out on a little headroom, upgradability, and eq.

"Where do I start with the design of this? Do I find a driver and work from there or do I start with the dimension contraints and find a driver to work within those? I think I got the above mentioned driver from the THT LP design page. I don't know where to begin this project....."

the way that it is done is to download a program like hornresp, enter the driver parameters, calculate the horn size, design a fold in the enclosure, go back and forth 50-100 times until something settles out that meets the spl target and the size requirement. that is typically too much for somebody who doesn't care to learn about design, which is why i suggested a proven design that fits in your space.

if the components that i suggested are too expensive up there, the tht lp is a reasonable alternative.

"Do you mean that a higher wattage amp will "over drive" the speaker at the lower frequencies if it isn't high pass filtered at 25 Hz? Sorry for the noob questions but I don't understand some of this stuff, to put it mildly.
I see that the plans are available for purchase for a low cost on the website but do they include driver suggestions as far as you know?"

as i mentioned most plate amps come with a built in high pass filter around 20hz. the tht plans include the suggested driver. i'm not completely sure, but i think the driver is the hf variant of the driver that you linked to in post #12.

---

"LTD is right on with recommendations so definitely heed his advice!"

you and nog suggested the tht lp, which is looking like the best option. ;-)

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post #20 of 66 Old 11-12-2012, 05:17 PM - Thread Starter
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Thanks for all the info so far. I know I will have more questions for you......

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #21 of 66 Old 11-13-2012, 04:55 AM
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Quote:
Originally Posted by dcg58 View Post

Thanks for the reply. OK. So I was thinking of orienting the opening to fire into the room but that isn't a good idea? Won't that end up distorting the sound back behind the TV? Firing it towards the safe is fine then? That would work for the budget for sure.
I will have to check out the F-20 but I am a little confused. The THT LP is the low profile of the THT correct? What is the F-20 compared to the THT?
So it would be alright to build just the one of these? I saw this thread but thought he built a pair because one wouldn't be enough. I would like the new sub to compliment my SVS sub or vice versa. My head is starting to spin again....wink.gif
Thanks for the links. I will give them a look.


Horns should fire into the corner with about 18" of space to breathe. That would give you access to the safe. Orienting the mouth through the door opening would not leave access to the safe as you would have several hundred pounds of sub in the way. wink.gif

I suggested the THT because everything you need to know is in the plans including driver recommendations (Parts Express Dayton RSS390 HF4). I think the F20 has been built with the DVC 15 so I was backwards on that. Anyway, I've built one of Bill's other plans and the directions are very detailed. The F-20 looks like a great design too but I have no experience with it...yet.

You should be fine with a 300w bash or yung plate amp if you have to stay within budget. You can always upgrade to a pro-amp and DSP later.
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post #22 of 66 Old 11-13-2012, 06:57 AM
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I dont see how the F-20 is out of your price range of $600? You can run that off a 300 watt Yung plate amp which is like $150 or so and the Dayton DVC driver is about the same or less. I am personally using the Yung 300 watt amp in my setup and I absolutely love it. As far as the THT versus F-20 goes, I prefer the F-20 as it is easier to build and fits into my space better.
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post #23 of 66 Old 11-13-2012, 07:53 AM - Thread Starter
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Thanks for the suggestions nograveconcern and Marty. Hmmm. Is there any performance benefit of one design over the other? Are both designs amenable to tweaking the size or does that cause problems? Does anyone know the outer dimensions of the THT LP?

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #24 of 66 Old 11-13-2012, 08:32 AM
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The performances are similar. Both will knock your socks off. Choose the one that fits in your space better since that seems to be your limiting factor. Tht LP - 72 x 18 x (18 to 36)

Current HT: HTPC-->Epson 5010 projector-->135" screen, BFM TLAHs x7 & THT
Build log: DIY rotary sub for contemporary HT in 100 year old house?
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post #25 of 66 Old 11-13-2012, 09:33 AM
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Quote:
Originally Posted by LTD02 View Post

nice theater workmanship there!
i did chuckle a bit when you pulled back the curtain. time to remedy that. :-)
your specs match very closely with these subs:
http://www.avsforum.com/t/1404092/wanted-big-bass-big-room-open-to-an-even-bigger-room-with-lots-of-windows/60#post_22034926
scroll up for driver and dimensions....for the cost of another driver, you could even double up and stack the cabs, although one should be enough for most anybody.

While I think a lot of us shared a chuckle, I see one big caveat here...

Look at the room in the link, then look at yours... See all those windows? That's half of what makes chasmain's room work so well is appropriate acoustic treatment for the bass drivers added to it. Glass windows are very effective bass traps, even if not optimized as such, due to their large area.

You've done a gorgeous job on the theater, so I'm guessing it's sound isolated, at least, possibly built below grade with cinderblock walls? Both of these will exacerbate room mode issues resulting in highly non-uniform low bass. I would suggest analyzing the room for anticipated modes, and factoring that into your placement decision. To be honest, subwoofage and associated acoustic treatment are at the core of HT design, so expect some degree of perfomance loss due to the retrofit into a finished theater...

Have fun,
Frank
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post #26 of 66 Old 11-13-2012, 09:43 AM - Thread Starter
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Quote:
Originally Posted by AndreasMergner View Post

The performances are similar. Both will knock your socks off. Choose the one that fits in your space better since that seems to be your limiting factor. Tht LP - 72 x 18 x (18 to 36)
Perfect. Thanks for the info. I am definitely leaning towards the THT LP now.

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Originally Posted by fbov View Post

While I think a lot of us shared a chuckle, I see one big caveat here...
Look at the room in the link, then look at yours... See all those windows? That's half of what makes chasmain's room work so well is appropriate acoustic treatment for the bass drivers added to it. Glass windows are very effective bass traps, even if not optimized as such, due to their large area.
You've done a gorgeous job on the theater, so I'm guessing it's sound isolated, at least, possibly built below grade with cinderblock walls? Both of these will exacerbate room mode issues resulting in highly non-uniform low bass. I would suggest analyzing the room for anticipated modes, and factoring that into your placement decision. To be honest, subwoofage and associated acoustic treatment are at the core of HT design, so expect some degree of perfomance loss due to the retrofit into a finished theater...
Have fun,
Frank
I know that sub is good for a chuckle. It was my second sub for a much smaller room years ago. The main one isn't pictured and is a bit better.(SVS PC12-NSD)
Good guess on the construction. It is mostly below grade as it is a basement walkout and has concrete walls on three sides. It is sound isolated to a degree and had a "dead" sound even before the carpet was added. How would I go about analyzing the room? Are we talking SPL meter here or something more involved.
I have a feeling you are going to say something WAY more involved. eek.gif

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #27 of 66 Old 11-13-2012, 03:23 PM
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You're right...

As it sits, I'll bet you have a fairly dead room at high frequencies, and a fairly live one at low frequencies. It's the nature of building materials and wall coverings, as well as many acoustic treatments. The issue is that as you add bass capability, it will resonate causing large response variations. Drives some folks nuts (others start out that way), while a few people can't hear the difference. Fortunately, there are some simple tools, software and a meter.
http://www.hometheatershack.com/roomeq/
http://www.tnt-audio.com/clinica/spl-meter_e.html

I'd have preferred a Radio Shack product page, but they've changed product lines so I can't say for sure if the new one has the key feature - an RCA jack on the side. The idea is to use the SPL meter as your mic, and your PC running REW as the display, with a patch cord inbetween. The meter's not terribly accurate, but it's OK in the bass range, and REW has some nice DSP-programming features for those who have the capability. The key bit is it allows you to measure what your room does, which varies with both subwoofer and listener position.

My final link is the master reference,
http://andrealbino.wikispaces.com/file/view/Master+Handbook+of+Acoustics+-+5th+Edition+-+F.+Alton+Everest,+Ken+C.+Pohlmann.pdf

He has a chapter on room modes, but there's far more here, from measurement to device construction. My approach is to find the worst of the room modes, and address them with both placement (within reason) and treatment. You get to build a sub, and something to absorb it's sound...
- meaure at several locations
- look for major room mode effects
- address them acoustically, then fine tune with EQ and placement.

HAve fun,
Frank
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post #28 of 66 Old 11-13-2012, 06:11 PM - Thread Starter
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Thanks for the links. I am a bit confused though. Am I measuring the room response for the subwoofer only? If so, doesn't Audyssey EQ XT compensate for the differences in the room? What am I missing here? Be gentle...

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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post #29 of 66 Old 11-13-2012, 09:11 PM
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eq doesn't really fix a room per se, it fixes a room at a position or an average of a few positions in the room.

multiple bass sources, bass traps, lossy walls, absorptive furniture, even people in the room help stabalize the frequency response around the room.

Listen. It's All Good.
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post #30 of 66 Old 11-14-2012, 05:54 AM - Thread Starter
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Right. So I will pick up a meter and see where my starting point is, acoustically speaking and then adjust for that or add the new sub and adjust at that point?

My Vintage style Home Theatre Build thread:
http://www.avsforum.com/t/1400234/vintage-look-diy-theatre-build
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