Bass Reflex Mod For LaScala?

[John Pearlman]

I was poking around on the net and came up with this picture. After a little more digging it turns out that it is a bass reflex modification for the LaScala. I found the forum that it was posted on but they don't have the thread anymore. So has anyone tried this? Are there dimensions for port area and cabinet size?

[John Pearlman]

[pauln]

Save the picture to your computer, then use the "File Attachment - Browse" button when you reply to upload it - so we can see it.

[Myhamish]

edit - sorry - the pdf was handbuilt Lascala cabinets by cueman - not the extended bottoms. Hamish

[John Pearlman]

I attached it

[Marvel]

John,

That was one of my drawings. djk came up with this mod. Beolow are some links to more info, but you'll have to wade through the material.

http://forums.klipsch.com/forums/259794/ShowPost.aspx

http://forums.klipsch.com/forums/3/513170/ShowPost.aspx#513170

Basically, if you want the box under the LS, it can be 10" tall. The ports are 4" pvc, available from HD, etc. and 10" long. Some have shortened the ports to about 7". This is totally removable (obviously), but if you like it, you can close in the back of the top section of the LS and put the ports on the back. Open up the top of the doghouse (use a router with a flush cut bit)

Bruce

[John Pearlman]

Hi Bruce

Thanks for the insight. The mod just hooked me because it looked simple to do and to reverse. I'm totalling restoring La Scalas from the ground up so now's the time to experiment i suppose. I'll build the base; it's much more reversible than cutting into the speaker. Thanks a lot. Nice drawing too by the way; is that Solidworks?

[Marvel]

John,

Actually using my sons old version of TrueSpace ver. 4.3. I have an

exploded view of the LS I posted some time ago, with bitmap laid over

it. Colter LOVED it. Attached a lower res version again.

The one good thing with putting the base underneath is that it will then raise the horns up more to ear level too.

Bruce

[John Pearlman]

Yeah, I saw that exploded view in another thread; its quite impressive. I always wanted to do a model of a LaScala in Solidworks than explode it and do all kinds of crazy mods. It would also be quite helpful to try out different wood veneers and such because in Solidworks you can change materials to anything from ceramic tile to hardened steel to curly maple. As for the bases, I not only like the potential for improved performance but the looks can't be beat as well. This and a subwoofer are on my project list.

[Marvel]

John,

I have rendered files of the exploded view with different wood

'applied', and different views. Mahogany, maple, walnut, white

ash. Some just don't look as good as I would have thought. Maybe if I

had played with the lighting more.

I have wanted to do the actual drivers, but haven't learned the program

well enough (Lightwave or 3D Studio would probably be better, but then

I just don't spend much time with this. The only reason I have

TrueSpace is because my son switched to Lightwave. The oldest likes 3D

Studio better). If I did this for a living it would be a piece of cake,

I'm sure.

Bruce

[middlecreekguy]

After spending a few weeks with my newly acquired La Scalas I can certainly see how this mod could benefit these speakers. Just raising them up 10 inches alone would be a plus in the bass department.

Now what if one were to build this as it's drawn up, ports and all, and then adds a 7 inch riser to the box. This would bring it up to the height of the Kornerhorn.

Would this be an improvment?

[Marvel]

After spending a few weeks with my newly

acquired La Scalas I can certainly see how this mod could benefit these

speakers. Just raising them up 10 inches alone would be a plus in the

bass department.

Now what if one were to build this as it's

drawn up, ports and all, and then adds a 7 inch riser to the box. This

would bring it up to the height of the Kornerhorn.

Would this be an improvment?

That would actually make the LS taller than the KHorn. The new KHorn is

shown at 50.75 inches. The older LS are 35.5 inches. You would just

have to try it. The good thing about raising them up is the tweeter and

midrange being more at ear level, so your situation and seating may

make a difference.

Bruce

[lar418]

Hi,

I actually built this mod for my Industrial La Scala's. It added some nice low bass and eliminated the need for a subwoofer. I'm using the K-33 woofer and my pedestal is 12" high. I made my rear volume 5.9 cu-ft to match the Cornwall volume and tuned the port to 37 hz. I also inverted the squawker and the tweeter, because with the 12" pedestal the tweeter ended up above ear level. (See attached picture.)

[lar418]

Picture wasn't attached!

[middlecreekguy]

Very nice.

So you ported yours in the back?

[intotubes]

No he ported them on front (see the slotted ports).

VERY nice job. Looks great and I bet sounds greater.

[middlecreekguy]

Geez. You're right. Now I see the front ports.

I was drinking port prior to that last post of mine[<)].

[John Pearlman]

Those are very nice bottom boxes, I'll post pics of my completed scalas with the reflex mod probably by February. I won't be done by then.

Thanks for the ideas

John

[DrWho]

Wow nice work...

It's ironic that a thread about this mod comes up when just last night

I was dreaming about it. The whole concept behind a port relies on the

volume displaced by the driver, which is a function of surface area and

excursion. The lascala bass bin is hornloaded which means the woofer

excursion is reduced for the same SPL...this means the woofer isn't

moving as much compared to a bass reflex design (aka the cornwall). The

end result is the SPL coming out of the port should be 5dB quieter than

the sound coming out of the horn.

So would anyone happen to know if the port works like a bass-shelf

design where the speaker is -3dB from 40-50Hz? Or is it tuned to keep

the response as flat as possible (which I can only see extending the

response down to maybe 47Hz...hardly worthwhile). Does anyone happen to

have any measurements of the beast (or the capability to measure it)?

[Marvel]

Dr. Who,

You are obviously not reading the posted links. Below is very old copy

from Dennis that I have posted before. I believe we are talking good

repsonse down to about 31Hz.

================

The taper rate of a LaScala is 100hz,The mouth area is good for 125hz.

Below this it is a big woofer in a small sealed box.If we plug the T/S

parameters for the K33E into a box program we will see that the

Qtc=.85, the Fc=82.5hz, and the F3=70.9hz. If we close in the back of

the high frequency cabinet and open the woofer rear chamber up into

this volume and fill with fiberglass we now have Qtc=.577, Fc=58.2hz,

F3=73.6hz .

Bessel=Qtc.577=D2 gives the best transient response and the least group

delay of all the sealed boxes.At 30hz the Qtc=.577 has 4.5dB more

output than the Qtc=.85 . Compared with sealed enclosures,the

transient performance of the best vented enclosure is worse than the

best sealed box enclosure.Since we have made great gains in performance

some may elect to stop here.But please read on.The next step is to port

it. The K33E is not the optimum woofer for this but it works

pretty good. With the box size optimized for a D2 we can port the

stock woofer to an SC4.The transient response of an SC4 while not as

good as an SBB4(more on this later)is better than the more common

QB3. Unequalized the F3=49hz and has 3dB more output at 30hz than

the D2. The response curves are parallel with the D2 the only

difference being the Fc being a half octave lower with the SC4 and the

output being 3dB higher from 30~70hz. The output of the SC4 does

not drop lower than the D2 until you go below 17hz. Again this

may be a stopping point for some.

But by adding a simple two pole high pass filter ahead of the power amp

we can now have a C6 with a -3dB point of 31hz. Since this is the

Fb of the system there is no increase in cone excursion or

distortion. The filter consists of a cap, an inductor and a

pot. The pot allows adjustment at Fb of +/- 3dB. This is

similar to being able to change the Qtc of a sealed box from

.5~1.0. If you think about it we have the choice between a

D2,SC4,and a C6 in the same box by plugging the port and/or bypassing

the eq. If you have a SET amp or simply want to get the most out

of the LaScala you will want to upgrade the woofer to something with a

lower Qts. The Klipsch K43E does the trick, as do the EV DL15W

and the JBL 2205. The EV and JBL drivers require some minor network

changes. The lower Qts drivers allow for an SBB4 alignment which has

the best transient response of the vented alignments. With no eq

they have 3dB more output at 30hz than the stock woofer. With eq we

have a maximally flat B6 and the F3 of the system is 27~28hz. If using

a solid state amp with the low Qts woofers a small resistor must be

added in series with the driver to have the same Rg as the SET does.

This mod can be backed out of a stock LaScala with no externally

visible changes if you don't like it. No one has ever gone back to

stock after hearing this mod. Paul Klipsch was violently opposed to the

venting of horn speakers bassed on his experience with venting the

K-horn. In retrospect it is easy to see why. The 12" Jensen field coil

woofer he was using had an Fs of 60hz and a quick calculation of the

vent area vs the Vb based on the photographs of this experiment looks

like an Fb of ~80hz. I am sure this sounded horrible. Paul Wilbur

Klipsch is a giant in audio.If I appear to see farther than PWK it is

only because I am standing on his shoulders.

None of the stock Eminence Delta, Kappa ,etc series drivers will work.

The K43Es that I have measured has Fs=31hz and Qts=.25,the TS

parameters that Klipsch hands out are bogus. The EV DL15W has an Fs=30

and Qts=.23 and the JBL 2205 has an Fs=30 and Qts=.21. After taking

into consideration the dc resistance of the woofer inductor and the

output impedance of the amplifier the optimum Qts for the vented

LaScala would be .312 with a Vas of 10.5 cu ft and an Fs of 30hz.

I'm looking for a total net volume of about 4.8 cu ft. I figure the

stock back volume is about 2.25 cu ft. Call it an internal height of

about 9" (22.5 X 22.5 X 8.70 = 4404 cu in = 2.55 cu ft). Two 4" ID by

10" long ports displace about .15 cu ft so 10" outside is close enough.