new home for my 12LTA (and family)

[JRKO]

Wakey wakey thread - where's zilla & co?

Evening chaps!! It's now time for progress with my 12LTAs!!!!!

First off some updates -

A)Crappy upstairs neighbour has moved and I'll be getting the block management to force the owner to replace laminate flooring with carpet (as per lease restrictions).

B)I'm out of work on what may be a permanent basis due to.....say it quietly....mental illness......

I'm struggling with bipolar. This also means I have to take everything real slow as I can get VERY carried away VERY quickly - just look at my previous speakers posted at beginning of thread I have to review and keep a really tight line on what I do (not like when I ran up $14k on a credit card )

C)This will probably be the last speaker project for a VERY long time

This means......drum roll please.... (diy drum roll smiley!!)

1)I can use the Beta15's!!!!!!!!!

2)Money is tight

3)I got to get it right

Sooooooooo I have a question about OB placement and then some research before I'm back.

OB is about as cheap & simple as it gets for the speaker build itself. This image is a good approximation of what I like but with 1x 12LTA, FT17H & Beta15 with its own plate amp per side.

What are the guidelines regarding room placement of an OB with regards to walls etc?

Thanks in advance everyone

 

[bigaudioscotto]

Generally speaking.
I found that 3 feet from back walls & a good 2 feet
from side walls yields best sound with OB.
and I have been thru many variations of OB.
by the way those look like Silver Iris & Augie in the picture.
I had that very setup for a while.

 

[norman bates]

I'm always amazed by a small tv and a huge speaker setup !!!!!!!!!!!!

If you like the front wall bounce (sounds excellent), I'd say 6' from the front wall.
Otherwise I recommend making a foam box to wrap the backside of the driver.

Norman

 

[JRKO]

If you mean the pic in the first post for me its not a TV. Just a monitor for a mac mini dishing out my lossless music collection. I just watch the odd film and a few programs I like. Gave up on TV 10yrs ago.

You know you've got too many channels when it takes you 3 hours to realise there is nothing on!!

Anyway a 108inch HD 3D whatever doesn't make up for the pi$$ poor content available these day. Might as well watch it on a 14inch B&W CRT

Not sure what you mean by the 'front wall bounce' or '6foot from the front wall'
Can you explain - I'm new to OB

 

[Godzilla]

I have my OBs about one foot to 18 inches from the back and side walls. I played with moving them around a bit but settled on what was both sonically and visually pleasant. I think what Norman means (but i'm not certain) about front wall bounce is how the sound from the back of the speaker bounces off the wall and back into the room (listening position)... and i think he must have meant six inches (not six feet). But I'm sure Norman will clarify. Nelson has called it wall illumination... i like that description.

While my BIBs are a few inches from side and back walls OBs need more breathing room... but i think my setup sounded very good even 10 inches from sides/back walls. The image 'grows' when you move them away from the walls. If it's too much you can always diffuse the walls with acoustic foam like this:

http://hackadaycom.files.wordpress.com/2011/10/acousticpanels1.png

 

[JRKO]

Zilla to the rescue

Thanks for that mate. What do you think of the OB's image above? I like the angled edge showing the laminations and simplicity, even for an OB.

I like the idea I can spend the difference between the wood needed for cabinets on better finishing of an OB.

I'm gonna rough up a couple of baffles to make sure I like the sound

Anything to look out for?

 

[Godzilla]

I would double up the baffle making it thicker. The pic you posted shows about the same positioning as my speakers (remember, I have H-frames). I love the look! There are some tricks on using the betas in OB you will have to search for but that should be fun actually.

 

[bombadil111]

What are the guidelines regarding room placement of an OB with regards to walls etc?

Thanks in advance everyone

Hey there. Yeah those are Hawthornes in the photo . . . I have a pair myself.

Personally, I wouldn't recommend placing OB's closer than 3 feet or so to the back wall . . . especially if you don't have anything to diffuse that back wave.

I have mine 4 feet from the back, and 3 feet to the side walls. The image is solid, with a nice 3d soundstage. Also, you'll want to experiment with toe in.

Here's a pic of my OBs. I've used some very ingenious diffusers in back

 

[Godzilla]

Bom, what happens to the sound when you move them closer to the walls?

 

[bombadil111]

Bom, what happens to the sound when you move them closer to the walls?

Godzilla,

They'll start to sound like 901's!!!

Seriously tho, no expert here, but it seems the closer you get them to the wall, the more you diminish their ability to throw up that beautiful 3D "wall of sound."

Not sure who owns those speakers pictured above, but wouldn't doubt if the owner actually pulls them out for serious listening. In a "live" room like that, close to the wall, and with no diffusers behind the speakers; they simply will not sound their best.

When I was building my ob's, I actually had them set up much the same way in my garage, for a quick listen. Close to the wall, no diffusers, etc. The result was striking, a very echoey sound, hollow, unpleasant to listen to. Of course a garage is not an ideal audio environment, but just pulling the speakers several feet into the room, mitigated much of the unpleasantness.

This is what I've experienced in my room with my system. But I suspect these attributes are inherent in all dipole type speakers. Give them room to "breath."

 

[norman bates]

yup, 6' from front wall.

That gives you a echo about 12mS delayed and a bit knocked down in level (my opinion).

That's why I prefer a foam box around the full range driver's backside (I don't have that much space anymore), eventhough my wife prefers un boxed driver (more echo-y).

Norman

 

[GM]

Yeah, I've similar results WRT to females preferring OB and even the lone false wall IB I tried. Initially, I just had some 3/4" thick felt carpet underlayment lining the back and one one each of the parallel walls of the IB and subjectively felt it needed more damping, so being unable to add much more and not wanting to spend the $$$/effort required to add a bunch of thick fiberglass insulation I just added a hanging 'blanket' of some behind the driver. This made it just right for me, but not my wife, so we compromised by only using the added damping to one each of the pair/channel.

For OB, I prefer near corner loading with some insulation loosely covering the rear of the driver to get what I consider the best compromise of both. Otherwise fairly near a wall and toe'd in as required in a ~live end/dead end [LEDE] room since I can't afford the opera house size/acoustics required for OB to be 'all it can be', though an OB in a near-field [< 1 m] app about 2/5th out into a room can give one a 'taste'.

GM

 

[JRKO]

mmm foam box thing and rug on wall wont pass muster with Mrs JRKO

Is the sound totally ruined if completely open backed and 2ft from rear wall?

 

[bombadil111]

mmm foam box thing and rug on wall wont pass muster with Mrs JRKO

Is the sound totally ruined if completely open backed and 2ft from rear wall?

Totally? Don't think so. But that close, I would strongly consider these behind the speakers:

GIK GridFusor. GIK Acoustics. Acoustic Panels and Bass Traps.

They're not cheap. That's why I moved mine out a bit, and used Palm plants.

Of course some folks use book cases, and the like, to achieve similar results. There's alot of techniques to try; but I would concentrate on diffusing rather than absorbing the back wave. Of course this depends on how close to the corners the speakers will be placed as well. Some absorption may be called for here.

Dipoles are like a double edged sword: They integrate well in most rooms (bass wise), but may need special placement/room treatments to achieve optimal midrange/treble performance.

 

[Godzilla]

>>> Is the sound totally ruined if completely open backed and 2ft from rear wall?

No, but the sound is different than a box speaker so i would suggest, since you are concerned, to build a quick and dirty open baffle out of something cheap and give it a listen. Get a couple of 2 x 4 particle board sheets and cut holes for the 12lta and tweeters. You will get sound down to about 150hz so keep one of your boxed woofers to provide bass. Listen to see if you like the dispersed OB sound. If instruments and vocals pop into your room like ghosts and it turns you on build the finished product.

Bom, those GridFusor's look great!

 

[JRKO]

ok - I'll mock up an OB from some scrap MDF i have lurking and report back.

There is only 1 way to layout our lounge with the speakers in free air so WAF is going to be important this time round - Goodness only knows why she let me build the MASSIVE ones in the first place

They sure shook the $hi+ out of our little village hall on the back of a T2 amp from hifimediy

BTW with a 50k Alps pot that I only get a few degrees of travel before I'm shaking the room - would a different pot give me more control?

 

[JRKO]

ok what gives?

i got a subscribed thread 'new message' email last night saying Norman had posted. I deleted the message and went to this thread but its not showing on my iPhone or my iMac - even if I follow the link from the email

Mods, can you help?

 

[JRKO]

just asked Planet10 over after I saw this post

http://www.diyaudio.com/forums/full...-audio-nirvana-15-good-start.html#post2794119

An Onken for the 12LTA - interesting

OB test this weekend will keep you posted but I'm keeping my options open

 

[Godzilla]

>>> An Onken for the 12LTA - interesting

I bet that would be amazing!

I would love a corner loaded Onken for the 12lta + a tweeter. If it didn't require a sub it would be like the linked vintage speaker.

http://www.hifido.co.jp/photo/08/387/38708/a.jpg

Zilla

--

http://www.diyaudio.com/forums/multi-way/88104-bbbib-bigger-badder-bib-speaker-26.html#post1569902

12lta BIB!

 

[JimW]

If you are thinking of using a baffle similar to the sizes in your early post, you might give consideration to a box of the size used by hammer dynamics or Thorsten Loesh's "afterburner" project as it wouldn't take up much more real estate. I have had a set of 12lta in my office for several years that live in a 20" wide by 14" deep by 44" high boxes tuned to 45hz. I am using the notch filter suggested by Thorsten (makes big difference) and a ft-17 fostex for treble augmentation. I treated the cones with dammar varnish, used modeling clay on the basket (rings like a bell, I could hear it once I treated one of the units), and had planet 10 make phase plugs (long time ago, they were his first big plugs). These speakers give a LOT of bang for the buck. I am driving them with a 750mw per channel Darling amp, and even with this limited power will easily fill my office. Most visitors are amazed at the dynamics and full bass, particularly at low (usual in office) volume settings.