Baffle layout

[4313B]

"But say, Widget - what do YOU look like, huh?"

We already know what you look like Bo

http://www.audioheritage.org/vbullet...=1025#post1025

I look a lot like this guy:

[boputnam]

I WONDERED if you'd remember!

Yup, that's me. Then, and even more, now...

[Mr. Widget]

Giskard, I hope you have better hygiene.

I'd prefer to think you resembled the bearer of the sword.

I almost scanned and posted a photo of Mr. Widget, but I really need to get back to the shop. I have some walnut calling.

I will post some photos tomorrow of some of my work.

[4313B]

What does "hygiene" mean?

"I'd prefer to think you resembled the bearer of the sword."

She does look pretty clean...

[DavidF]

Say Bo, my first thought on the diagram is that there are a lot of holes in the baffle with the three drivers, the port, and the crossover panel. All this missing mass may cause some resonance issues on the front panel. This was my thinking on placing the port on the backside on my 3-way floor standing boxes. But, you may have to keep the port on the front if the required length requires a bend in the port. Installing on the back panel will probably run the tube into the woofer in some way. If you need to keep the port up front, a good stout back-side-front brace just above the woofer could be a benefit.

Regards,
David F

[boputnam]

Hey, DavidF...

I'm following some old JBL plans, here, where a 3-ft3 cabinet for the LE14A calls for a 4" diam 3" duct. Looks kinda short to me, but the models I've run sez it's OK. That 4" diameter takes alot away from the needs of length. I'm willing and able to modify the port, if needed.

Here's relevant portion from the vintage plan:

[Ian Mackenzie]

Regards the port pozzy,

Front baffle space reasons can be a benefit for certain layouts.

There are also noise (chuffing, organ pipe resonance and midrange output ) considerations. Port openings in the rear would have to be quieter, but the better way is to use bigger a port area to reduce air velocity and avoid the so called sonic boom effect according to some notable designers.

Although this in turn becomes even more impractical as larger ports demand even longer ports in boxes of limited size.

I read somewhere rear ports can also assist with modifying the bass output more effectively by moving the box in and out from the rear wall, presumable this is due to greater room gain from rear mounting if the port.

I recall rear ported bookshelf boxes have rather pronounced bass.

Some manufacturers are now offering adjustabe ports for modifying bass tunings to suit various rooms and locations.

Ian

[4313B]

JBL Enclosure Information Manual.

http://www.lansingheritage.org/html/...979-manual.htm

[4313B]

Loudspeaker Enclosures Their Design and Use.

http://www.lansingheritage.org/html/...enc-manual.htm

[4313B]

Originally posted by boputnam
Hey, DavidF...

I'm following some old JBL plans, here, where a 3-ft3 cabinet for the LE14A calls for a 4" diam 3" duct. Looks kinda short to me, but the models I've run sez it's OK. That 4" diameter takes alot away from the needs of length. I'm willing and able to modify the port, if needed.

Here's relevant portion from the vintage plan:

Hey Bo, I actually built a pair of these enclosures when I got my first pair of LE14A's!

I can't get all the actual plan sheets to scan. I was thinking of taking them to Kinko's. Anyway, I've attached the booklet that came with the plans above, as well as one for Altec.

[boputnam]

Extraordinary effort, Giskard! And I think I have carpel tunnel syndrome!

I've had b/w copies of many, but now they're all compiled and buttoned-up within Acrobat, and look like they should! Ready for colour printing!

Very, very cool.

What kinda mood you in!!?? A real Labor Day, my friend...

[boputnam]

"Hey Bo, I actually built a pair of these when I got my first pair of LE14A's!"

Nice! I'll post some pics of the ending product. Only differences is I'm adding the LE5, and either the 075 or 2405, with the N65 network but that's all just for fun!

and

"I can't get all the actual plan sheets to scan. I was thinking of taking them to Kinko's."

No need. I've already done them, and will try and follow your lead, here...

[boputnam]

This evolved into a quite interesting, and archival thread!

*****

In-between posts/steals yesterday, I redesigned the planned baffle that started this Thread, just a bit.

Reviewing all the literature and plans here and elsewhere, I came way with the (possibly unfounded...) impression that Bafflers tended to position the port near the LF. Not in corners or away from the LF, but near to it. I couldn't find anything actually written about this - and this is different then the front/rear argument (whoops! ). Ha!

So, I elected to move the port closer to the LE14A - Option B, below. Any of our gang got experience with either - is there any preferred location for the port relative to the LF (staying on the front, for now... )

I have taken the advice and offset the LE14A from any symmetry with the baffle edges, too.

And, please, I already took the obligatory abuse for the poor image quality - I assure you the original is quite a different matter!

[4313B]

"is there any preferred location for the port relative to the LF"

Generally you want the end of the duct that is inside the enclosure as far away from other internal surfaces as it practical. Option B in that respect would be preferred to Option A. Option A would be fine for a port such as that found in the 4313 or L96.

"I have taken the advice and offset the LE14A from any symmetry with the baffle edges, too."

Symmetry sure looks nice but it generally isn't a great idea in loudspeaker design.

[4313B]

My attempt to scan in the 1977 and 1980 versions of this publication failed. I may take them to Kinko's in the future.