LaScala Mods

[djk]

Just some notes for both the stock and the (vented) ported LaScala.

Porting does not reduce the basic efficiency of the LS, it does however reduce the massive 140hz peak, porting also smooths out the overall response above 100hz, and reduces the dip at 200hz in the stock LS.

To get the most out of the ported LS mod you need an EQ similar to the EV Interface A box, it has 6dB of boost at 35hz. You can boost a sealed LS, but that inceases the cone motion, EQ at Fb (port tuning frequency) does not increase cone motion. Less cone motion, less distortion.

Any equalizer with a subsonic filter can be changed to do this as well, usually it's just a matter of changing two resistors per channel. I buy used Audio Control EQs from eBay when they go for cheap, the 520 is a nice 5-band piece that is designed to complement standard tone controls and be easy to use.

Foam

Both versions of the LS benefit from a 2' x 2' x 1" piece of foam behind the woofer. It really smooths out things above 100hz.

If you are using subs all the time, you can leave the stock LS sealed and reduce the back volume by about 1/3, and use the foam. This totally reduces the bottom octave, but smooths things out above 100hz. Use non-porus fill to reduce the volume.

On axis, the above modified LS will measure flat to about 800hz, and very smooth too. You may use a 650hz or so crossover point on a good horn and driver combo for a nice two-way at this point (or retain the stock Klipsch setup).

Thanks are due to Carl Huff for his extensive work and measurements.

Stock LS

http://cdn.avsforum.com/0/03/037f91bb_DIRAC_LEGACY_01.jpeg

Reduced volume stock LS with foam

http://cdn.avsforum.com/d/d6/d6ed5986_DIRAC_LEGACY_PADDED_LESSVOL_02.jpeg

Carl's measurements were done with a gated measuring system, in a garage, with the door rolled up (open). In room response will show more bass below 100hz due to room gain.

In room non-gated measurements show the ported LS to have 7dB more output in the 31hz band (1/3 oct analyzer) vs the stock LS, and 3dB more output in the 50hz band (both without EQ). Using the EQ makes the 31hz band only 3dB down from the average level above 100hz.

The contour lines of equal loudness (sounding twice as loud) in the 30hz~40hz region are only 3dB~4dB apart at a level of 90dB, so even without EQ the ported mod sounds like it has twice the deep bass. With the EQ the bass sounds very solid on music, most people would not require a sub (except tor video).

But

Using a processor like the Waves MaxBass a subwoofer for video is probably not needed either. The 'feel' of bass is mainly from high energy below about 60hz or so, above 60hz there is more of a sensation of 'tone'. The Waves unit takes the fundamental note and generates 3rd and 5th harmonics (an old trick used when playing a piece written for a 16' organ on an 8' organ). With a small speaker like a Heresy this has the sensation of 'tone' when playing those 16' notes, but not the 'feel' (as it has no real energy below 60hz).

Using the Waves unit with the ported LS can make you feel the notes as low as 10hz~12hz (when it converts them to 30hz and 50hz) because the ported LS has lots of output there. The Waves unit also has the provision (on some versions) of removing the damaging infrasonics below the Fb of the box (although the recommended EQ does this as well).

As a side note

The Waves unit makes the Heresy sound like it has bass, but without the 'feel' of the sub 60hz notes. Why would you want this? It works well for apartment dwellers, or wedding dances (those people like the sound of bass, but don't seem to like their teeth rattling).

Edited February 14, 2014 by djk

[ClaudeJ1]

it does however reduce the massive 140hz peak, porting also smooths out the overall response above 100hz, and reduces the dip at 200hz in the stock LS.

Most people refer to this as "fast bass." I just designed my own Q-Pioe bass horn that is fast and flat (no nasty peaks). It too uses foam behind the woofer.

[RRR]

The LaScala mod with the foam looks like a good option. Maybe a pair of THT's to fill in below the bass dip shown in the chart.

The THT response runs flat above 45 Hz (24" version) and can be crossed over higher than 80 Hz without sounding muddy, in fact i ran mine up to 180 Hz with good results just for some testing. Build it wider and its basically flat to 25 Hz.

I assume this chart is for the K-33 ?

[djk]

"I assume this chart is for the K-33 ?"

The graphs by Carl were made with the BEC cast frame woofer.

The chart from Pete, I'm not sure about, got lost in the forum change.

[Guest " "]

power handling of a LaScala with k-33 is only 25 watts below 40hz....I would be careful about eq'ing to boost output below 40hz.....as often staten...the LaScala box is not a sub woofer box...it's a high pass mid bass horn.

[djk]

"power handling of a LaScala with k-33 is only 25 watts below 40hz....I would be careful about eq'ing to boost output below 40hz.....as often staten...the LaScala box is not a sub woofer box...it's a high pass mid bass horn."

Correct, for a stock LS.

Ported they will handle a 400W/4Ω amplifier on program material above the Fb of the system. I have seen (and heard) the K43 driven 10dB into clipping on a 300W/4Ω amplifier, ported to 28hz with an EV Sentry III EQ in the system.

[mustang guy]

"power handling of a LaScala with k-33 is only 25 watts below 40hz....I would be careful about eq'ing to boost output below 40hz.....as often staten...the LaScala box is not a sub woofer box...it's a high pass mid bass horn."

Correct, for a stock LS.

Ported they will handle a 400W/4Ω amplifier on program material above the Fb of the system. I have seen (and heard) the K43 driven 10dB into clipping on a 300W/4Ω amplifier, ported to 28hz with an EV Sentry III EQ in the system.

Would a minimum of a Crites cast or K-43 be recommended for the port upgrades and EQ'ing? If so, and if I made these upgrades, I would have six K-33's for sale.

[ClaudeJ1]

Would a minimum of a Crites cast or K-43 be recommended for the port upgrades and EQ'ing? If so, and if I made these upgrades, I would have six K-33's for sale.

Since you have great sub woofage in your THT's, I would opt for the K43, since it's higher BL product tips up the performance more towards a MUCH clearer midrange performance. In the unmodded LaScalas, it thins the bass a bit, but your have Tubas to handle that part anyhow. I've had a phone conversation with a member who swapped out his square magnet K33's even up for K43's per something I wrote years ago and he agrees that the midrange definition (where more of the music lies) is superior.

If I were to do the port mod with K43's, I would add to the bottom, since it's reversible to stock if you ever need to sell them when upgrading to Q-Pie horns. LOL!!

[Jujubee]

DJK......thank you for the additional information.  After several years, I am getting around to modifying my Lascala's to the ported version.  I found your additional information just at the right time.  Thanks again. 

[mwiener]

djk,

 

Can you comment on the physical positioning of the foam behind the woofer.  I tried a piece shoved into the V of the LaScala dog house directly behind the woofer and I measuring almost no change.  My ears tell me the same thing.  Maybe I should have folded it in half and wedged between V and magnet?

 

Thanks,

 

Mike.

[spezjag]

^ +1

More detail on this would be greatly appreciated. Type of foam, exact positioning, etc.

Thanks in advance!

[Bacek]

I guess it's reference for the thread

 

http://www.avsforum.com/forum/155-diy-speakers-subs/1458686-la-seos-4.html

 

Just reading it. Will be useful because yesterday I came back home with old but new to me La Scalas.I

[mwiener]

Thanks for posting the original link.  That is very interesting for a couple of reasons.  I don't have the referred to notch at 200hz.  What I have is a drop at 350hz that I was trying to smooth out.  I also noticed he is using a different 15" driver.  I am using the stock K33, and he is using Bob Crites CW1526.  Making me wonder if it is actually the driver he is using plus the foam that provided the results he has.  Since the drop off is just below the mid cross over point, I might be able to fix it with a CW1526.

 

Mike.

[Bacek]

I guess you will newer find it if you will not measure it by yourself. Some said that use of Eminence Kappa 15C smooths out upper region but I will not bet on it without actual measurement. You can also try to put at least partial (radius) reflectors inside La Scalas internal corners as described by Bruce Edgar for example in The Monolith Horn article.

It can be done even temporarily by inserting long, triangle cross sectioned "bar".

 

Edited July 28, 2015 by Bacek

[Full Range]

You folks know that I have modified La Scalas

No drivers are original

Custom Crossovers

Bass extension bin

But the reason for my post is due to the reference of foam behind the bass driver

I had experimented with this not knowing others have done it

On my system foam did not work well, so I had to find an alternative

Also found that large bubble cells worked better that foam

After a lot of experimentation, what eventually worked best for me was a styrofoam cone adhered to the magnet of the driver ( see photo )

Edited July 28, 2015 by Full Range

[spezjag]

Thanks for the info and pics!  I like the idea that you experimented with the large-cell bubble-wrap - innovative!

 

Where did you source the foam cones from?

[Marvel]

Looks like Christmas tree parts from an art/crafts store.

Bruce

[Stevenarrow]

Bracing drivers has always been a decent upgrade as long as it doesn't take up too much enclosure volume. I can't image that the foam trees stay stiff enough to real do much long term... just my 2 cents.

 

Perhaps wedging a hard wood piece would be more beneficial...

[spezjag]

Bracing drivers has always been a decent upgrade as long as it doesn't take up too much enclosure volume. I can't image that the foam trees stay stiff enough to real do much long term... just my 2 cents.

 

Perhaps wedging a hard wood piece would be more beneficial...

Or maybe placing a metal rod or wood dowel through the styrofoam cone - this would solidly brace the driver's magnet against the cabinet, while providing the volume and the "give" of the styrofoam.

Edited July 28, 2015 by spezjag

[Marvel]

I thought the closed cell foam was to placed to take up volume, not brace...