Bass Reflex Mod For LaScala?

[Marvel]

Has anyone done the port mod though the top section?

Closing off the top back half and porting it with 2 4"x7 ports

and opening up the top dog house cover?

I believe Bruce a 3d drawing of this. (also gave me the idea)

Just wondering if it has been done before or just a new idea.

If it has been done what kind of results did they get?

Thanks

S. Lee

Santa,

When Dennis first came up with this, he mentioned that those who own earlier versions of the LS could do this easily, since the very top of the cabinet was removable and the access hatch was on the top end of the doghouse. The sound would be no different.

What would be different would be having to have the ports face out the back instead of the front, as can be done with the box added to the bottom.

If you are building from scratch, I would just make the top open and put strips along the back to make a removable panel (with the ports) there. Then it would look like a normal LS from the front. However, some have raised the LS up to get the mid and tweeter closer to ear level, so the box underneath isn't a bad idea anyway.

Bruce

[Rotorhead09]

Bruce,

just checking to see if anyone else has ever done this mod from scatch and

what kind of results they may have gotten. I am going to build mine with the

ports open to the back. Hopefully I will get a little deeper bass out of the LS's with this mod.

I got all my horns and drivers in today. Just need my wood and I will be ready to start.

I will practice on plywood first before I start with the Birch. I though about 45 degree cuts on my

corners. That may be to much of a challage for me but would sure look a lot nicer.

Have to see how my practice cuts turn out.

Thanks for the support!

S. Lee

[solarcarl]

I'm almost done with the mods on the La Scalas. Heres a pic of one of the speakers. Note The new Crite tweeter on top of the 511B. I still need to finish assembling the networks and then time for some listening . Carl

[solarcarl]

Let me try that again and hopefully the pic appears.

[Rotorhead09]

Carl,

Nice pic, How much bass difference with the port mod?

Did you notice any at all?

S.Lee

[D-MAN]

Got to thinking - they probably DO sound better than a stock or even a top-modified ported cabinet because the high frequency units are raised up to ear level with the port cabinet on the bottom. That would certainly promote better HF dispersion characteristics in the listening space. Speaking from a purely theoretical point of view, of course.

DM

[DizRotus]

Im planning to do this mod for the La Scalas that I got from Michael Colter and restored for the local high school bands practice room. They sit on top of instrument lockers (see attached photo) but they are now propped up in the back so that they fire down into the seating area (theyre tethered at the back so they cant fall forward).<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

Adding 10 of height at the base will only exacerbate their top heaviness. Also, with the ports on the front, they would fire down toward the 1.5 foam pads under the speakers. Im thinking about reconfiguring the mod box so that its wedge shaped (preserving the same internal volume) and locating the ports on the sides or the back. What do you think? Any thoughts about the side or rear port locations?

[Rotorhead09]

D-Man,

Well, I was going to port mine through the top. I guess this had not been

done yet. I am new to the forum so I did't know if any have tried this mod yet.

Bruce introduce the plans to me so I guess we will just see (hear) what happens.

One of my reasons for porting though the top was to maintain the stock look from

the front and lowing the bass response. I will post some pics when I get started as

I move along with the project. Just got my 4" flared ports in today. My Birch will be

here next week.

[DrWho]

Im

planning to do this mod for the La Scalas that I got from Michael

Colter and restored for the local high school bands practice room. They

sit on top of instrument lockers (see attached photo) but they are now

propped up in the back so that they fire down into the seating area

(theyre tethered at the back so they cant fall forward).

Adding 10 of height at the base will only exacerbate their top heaviness. Also, with the ports on the front, they would fire down toward the 1.5 foam pads under the speakers. Im

thinking about reconfiguring the mod box so that its wedge shaped

(preserving the same internal volume) and locating the ports on the

sides or the back. What do you think? Any thoughts about the side or rear port locations?

Ideally you'll want the ports to be close to each other, but apart from

that they can go on any side of the cabinet. For the sake of symmetry

you're probably better off putting them in the back. And since it's

more of a permanent install, you might consider putting grill cloth or

screens across the ports to try and keep the critters (or flying

debree) from getting stuck inside.

And since these speakers will be leaning forward, you might considering

fastening the port mod to the speaker (like drilling a few holes or

using a few c-clamps).

Another thing you could do would be to change the shape of the ported

cabinet such that it sits flat on top of the lockers, but the side

connecting to the lascalas is at the correct angle for aiming the

speakers.

One comment about porting a speaker....when you get below the tuning

frequency the woofer excursion is no longer controlled by the box

volume....which means you run the risk of damaing a driver by sending

LF information to the speaker. It would be tragic if someone decided to

play something with a ton of bass and then cranked up the volume on the

ported lascalas. Buried in the original posts DJK makes mention of a

peaking 2nd order high pass filter - which will help to further boost

the low end while also controlling the cone-excursion below the tuning

point. Definetly something to keep in mind...

[DizRotus]

DrWho-

All of your suggestions are what I am contemplating. Changing the configuration of the mod box to tilt the speakers forward while allowing the mod box to sit flat on the top of the lockers (see attached drawing) would necessitate putting the ports in the back or the sides. I believe you that having the ports close together in the back is better than having one on each side, but why does it make a difference? Is there any penalty for putting the ports in the back as opposed to the front?

Thanks,

P.S. Say hi to Michael C.

[djk]

Whole lot easier to slap a board across the back and put the ports there.

http://cgi.ebay.com/EV-Electro-voice-Interface-A-equilizer-eq-Sentry_W0QQitemZ5879417134QQcategoryZ14993QQrdZ1QQcmdZViewItem

[DrWho]

I believe you that having the ports close together in the back is better than having one on each side, but why does it make a difference? Is there any penalty for putting the ports in the back as opposed to the front?

Well first let me say that I don't entirely know why and I'm not an expert on the subject...but I can regurgitate what other professional speaker designers have told me... []

Apparently having the ports close to each other, or ideally having a single larger port, dramatically reduces the non-linear behavior (port compression and port noise). You also have issues with the polar response of the speaker when you start spacing sound sources apart, but at frequencies that low you aren't going to have any problems. The general rule of thumb is to have sound sources no further apart than 1/4 wavelength of the highest frequency being reproduced. At 45Hz that comes to 6 feet and 3 feet at 90Hz.

As far as rear versus front....there is no notable difference (even outside). And again it is due to the fact that the wavelengths coming from the port are much larger than the cabinet...yielding you pretty much the same omni-directional dispersion pattern. There might be 1 dB of difference here and there, but that's chalked up as inaudible (heck, it might even be 1dB in your favor...)

[DizRotus]

What is the lastest input anyone has regarding the pros and cons of this mod?

[DrWho]

You gonna start building it? I reread everything I wrote and would recommend putting the ports in the front as it'll behave better that way. And if you're gonna build something to angle the lascalas down then you might as well do the angled port bin idea.

[colterphoto1]

Hey Neil!

I'd go ahead and do it.

But anchor the daylights out of those will ya? Scares the heck out of me seeing those on top of the kids' lockers like that.

I don't see how all that metal doesn't buzz like a hive of bees!

Michael

[DizRotus]

Hi Michael,<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

I originally shared your concerns about the locations on top of the instrument lockers, but buzzing/rattling has not been a problem. The lockers are made of MDF-like material; only the doors are metal wire cages. Theyre deeper from wall than the depth of the La Scalas. The speakers sit on 1.5 dense foam and are tethered from the back to the top of the lockers to discourage toppling forward and/or theft (neither of which seems likely, but it made the instructor feel better).

Im inclined to make the basic rectangular boxes for the reflex mod with the ports facing forward. The downside is that the approximately 8 of additional height will only exacerbate the top-heaviness already present. The advantages are easier construction than any angular variation and they would be more readily transferable to other La Scalas if the director is not pleased.

Now for something completely different. As a photographer you might be interested in the article at: http://www.smithsonianmag.com/issues/2006/july/indelible.php which described the history behind the attached iconic photo of the Babe.

[colterphoto1]

Excellent story Neil. Thanks for sharing it. Sometimes in photography I get little moments like that- the 'turn around Michael' kind of thing, that the real story is not what I would naturally point my camera at.

This is a fantastic photo and a wonderful story about the man who captured that iconic moment and how he did it.

I enjoyed our chat today. Thanks for sharing with me.

Thanks

Michael

[mowntnbkr]

I am going to build these this weekend, but I was wondering if I should put any baffling in there or just leave them. I was going to order the 4" ports from partsexpress, but they want more to ship them here than the cost of 4 of them, so I will use some ABS until I move down south.

[DizRotus]

They're done . . . sort of. I finally decided to open the tops of the dog houses, seal the tops and port them out the back. See Ported La Scalas? for details.

mowntnbkr that's a good question, that I have pondered also. It's addressed in the Ported La Scalas? thread.

[mowntnbkr]

bump