Who did it, are you happy with it, would you do it again, etc. ... the Lascala Bass bin addition

[Marvel]

Mike,

If I actually get this done, I will happily haul one to a good room somewhere and beg/borrow something to test the mod with. It would be interesting. I'll even post the results for you.

I think th eq is a simple filter I can place between the pre and power amp. I'll even switch to a higher powered SS amp, so the anti-SET crowd won't complain. Might even try it both ways. I just have so many irons in the fire right now. The youngest heads off next weekend for his junior year at Valpo, I'm helping my GF get back to China and the oldest son gets married in two weeks....

Bruce

[DrWho]

Dang Bruce, you're busy!

I've got a measurement rig here in a suitcase ready to ship, or bring over to someone's house or whatever. I'd be willing to go 50/50 on the shipping (since I can't afford the whole thing on my college budget). It might be cheaper for someone local to try out the mod. I could totally whip one together and bring it over to anyone with lascalas for measurements. An outdoor ground plane is the way to go in order to avoid the annoying influence of a room.

The filter is very straightforward and somewhere in one of those posts Dennis provided a schenamtic (from I think a Westhost network).

I think I'll go bother Colter...he's got LSI's which apparently have a better driver for it and we're already setup to do ground planes on his driveway. 6 pieces and 2 ports for the bottom box shouldn't take more than 2 hours to have ready for testing. The network will take the longest to build, but I can probably get all of the parts and the board built for free at school.

[djk]

Some remarks (in no particular order):

"It's just that Klipsch has tried this mod before and determined it wasn't worthwhile..."

I would wager that they dismissed it out-of-hand without trying it. First, it goes against their idea of a 'pure' horn system. Second, it requires a piece of electronics be added to the customer's system, and third, it requires a lower Qts more expensive woofer (like the K43). The cost differential would have to add about $800 on the retail price of a pair (for the more expensive woofers, electronic box, and cabinet mods).

"but he never provides any screenshots of his measurements, nor provides the manner in which they were measured."

My measurements were done in a real room, as you would listen in. My spectrum analyzer is so old it does not have a way to export data other than the parallel-port printer output, and does not have a data-base library either. Its memory is what you printed out on tractor-feed paper and then filed away. I had design input on the filter/integrator part, someone else did the computer/output part (not my area of expertise).

The measurements don't tell the whole story of how it sounds anyway (which in turn just tells us we don't really know what or how to measure the things we hear). Measurements between two 4" ID by 10" ports and two 7" ports show little difference, and show little difference in simulation (most like the sound of the 7" ports). I always use the measurements and simulations to get me close, then I go the final distance with what my ear tells me.

You can measure it outdoors. What you will find is a big hole between where the horn rolls off below 100hz or so, and the port tuning frequency. In a real room, the floor-to-ceiling resonance, and the short-wall resonance fill in that hole quite nicely. Along with the room gain below 50hz or so, the overall level below 100hz starts looking much better balanced with the levels above 100hz.

One last story pertaining to measurements:

In the early 70s I had a chance to use some B&K strip chart recorders with the chain-driven oscillator, mics, cathode followers, piston callibrators, etc. I had designed a fairly unique speaker that sounded quite exceptional, and it measured good too.

It measured good in spite of a bad midrange that rubbed so much it was un-listenable.

After changing the bad driver and tweaking the crossover a bit we resumed evaluation. The owner of all the test equipment was a manufacturer that made fairly expensive two-way speakers. As a result of the measurements and listening session with my three-way speakers he decided to give another try at a three-way design himself.

[DrWho]

You can measure it outdoors. What you will find is a big hole between

where the horn rolls off below 100hz or so, and the port tuning

frequency. In a real room, the floor-to-ceiling resonance, and the

short-wall resonance fill in that hole quite nicely. Along with the

room gain below 50hz or so, the overall level below 100hz starts

looking much better balanced with the levels above 100hz.

The fundamental floor-to-ceiling resonance of an 8ft tall room is going

to correspond to ~140Hz. Short-wall resonances are going to be high Q

and reside somewhere around 60Hz for a 19ft wall (different dimensions

will shift that around). Room gain doesn't start happening until the

reflections are in phase with the direct signal. For 55Hz you're

talking a longest room dimension around 12 feet (kinda like my station

wagon). So I think it's safe to discount this behavior as contributing

to the response. And even if it did, I might argue that this behavior

would not be desireable (but you'd have to look at the time-domain to

see that...not the frequency response).

However, outdoors is a 1/2 space environment whereas indoors we're

closer to 1/8 space. This dramatically changes the loading on the horn

and is likely the reason for the dramatic changes in the behavior of

the horn. Putting the speaker into the corner of a room basically makes

it seem like the horn itself is bigger.

My philosophy with measuring is one of "If it measures good but sounds

bad, then you're measuring the wrong thing". I also believe that you

don't know when you're finished until you measure it. We should definitely be using our ears to determine how things

sound, but if you hear a problem it only makes sense to find a way to

quantify it so that you know when you no longer have the

problem.

[DizRotus]

Has anyone tried this and gone back to stock? I'm not aware of anyone doing that, but, if so, it would be interesting to know why.

Some time ago I discussed with Michael Colter building a test box and then sending it to him in Indy (I believe it's in one of the threads linked in one of my posts above). For many reasons I ultimately decided to close the tops and port out the back, with good results.

It would not be difficult, expensive or time consuming to build a test box to sit under a La Scala. You wouldn't even need to attach it; the weight of the cabinet with some foam insulation between would suffice. Then you could test and measure without the mod (A) and with the mod (, with varying port tube sizes and configurations, network changes, etc.

While it would have been great to have had the opportunity to measure and quantify the before and after performance of the speakers I modified, the bottom line is that my ears (reasonably sensitive measuring devices) preferred the modified versions. Irrespective of what the measurements might have indicated, I would have relied on my ears. It would have been silly to say, "I like the sound of B, but A measures better so I'll go with A."

On the other hand, if A and B sound the same and A measures better, then certainly I would go with A. That is especially true with respect to this mod as it would be pointless go to the effort and expense if there is not a perceived improvement. Because these were beater speakers (looks and potential re-sale were not important) that were being used by a high school band, it was not intimidating to cut into the dog house to port through the top. Nevertheless, had they not sounded better ported, they would have been quickly and easily returned to stock (with the exception of new BEC sourced GE caps in the networks and the bass bin braces).

If it sounds better, then, "[Measurements]? We don't need no stinking [measurements]." And, yes, I know that the original line from The Teasure of the Sierra Madre regarding badges was different, but Mel Brooks, in Blazing Saddles, and Click and Clack, on Car Talk, have made the "Badges? We don't need no sinking badges" version the parody standard.

[DrWho]

It would have been silly to say, "I like the sound of B, but A measures better so I'll go with A."

That would absolutely not be silly to say! That would simply mean the

listener needs more ear training, or needs to be using better source

material, or better amplification or whatever. How many times to people

argue that revealing speakers need better source material and

amplication? Don't you think a more revealing speaker will need even

better sources?

One problem with relying solely on ears is that they can be easily

tricked. I have done all sorts of AB comparisons with golden ears that

subconciously wanted A or B to sound better, and they would defend

adamently that they could hear a difference, only to be dismayed when I

reveal the fact that A and B were the exact same thing (so really an AA

comparison or BB comparison). Heck, you can go a step further and trick

them into preferring A when they spend their whole life defending B.

It's just how psychoacoustics work and everyone is suceptible to it

(including myself).

[DizRotus]

It would be silly to disagree with Dr. Who.[]

[Rotorhead09]

Rotorhead, you have been living with those for some time now. Do you still like them, and can you give a comparison to the stock LaScala?

Bruce

Hello Bruce,

Good to hear from you! Yes, i like them alot... I recently purchase a set of real LS and was listening to the two together and I do like the way mine sound over the real LS. I do have to pump up the volume a little to get the deep bass response that I was wanting. I sometimes kick in a sub woofer to listen to them low.

My friends who see the two think the real LS are the ones I built! The home builds look so much better than the unfinished LS that I purchased. When I show them the photo's,. that's when they believe...

Sorry, guys I am not as technical as you all. I have no way of measuring sound except with my ears... I just know what I like to hear.

Santa Lee

[Marvel]

Santa,

The ported version is a little lower in efficiency compared to the stock LS. Very cool that you still like them, especially after all the work you put into them.

Bruce

[djk]

"It would be silly to disagree with Dr. Who."

He makes mistakes now and then, as we all do.

"The fundamental floor-to-ceiling resonance of an 8ft tall room is going to correspond to ~140Hz. "

Hmmm, I measure it as being the half-wavelength, or about 71hz for an 8' ceiling. Short walls are on the order of 12'~14" in most houses, so 40hz~47hz here.

"(but you'd have to look at the time-domain to see that...not the frequency response)."

A given, and 'tube traps' don't particularly work well either (even if you fill up the room with them and break the bank). And of course, equalizers are of no real help either.

"I also believe that you don't know when you're finished until you measure it. "

After 50+ years we still don't know how to determine 'good sound' with just a measurerment. Me thinks many budding engineer types suffer from Beranek's Law (revised).

Beranek's Law (revised)

It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, and his own loudspeaker measures better than does anyone else's loudspeaker (then) In this case, the sound of the loudspeaker seems to play only a minor part in forming a person's opinion.

[DrWho]

He makes mistakes now and then, as we all do.

"The fundamental floor-to-ceiling resonance of an 8ft tall room is going to correspond to ~140Hz. "

Hmmm, I measure it as being the half-wavelength, or about 71hz for

an 8' ceiling. Short walls are on the order of 12'~14" in most houses,

so 40hz~47hz here.

Oops! [:$]

But still, you're talking high Q resonances...

"I also believe that you don't know when you're finished until you measure it. "

After 50+ years we still don't know how to determine 'good sound'

with just a measurerment. Me thinks many budding engineer types suffer

from Beranek's Law (revised).

That

quote came from PWK

actually...seems my reference got lost in one of my edits. Anyways, I

always took it to mean that he would listen to a system, hear some

problems and then go to measurements to quantify them. He would then

engineer a solution to those problems knowing he was done when it measured right. Of course the trick is not sacrificing any

other performance in the process. Since that is too idealistic, you

have to choose a system of least compromises, but I don't know of any

other way to

prioritize various performance goals without actually using our ears.

I guess I see measurements as a way to identify "bad sound", but that

which defines "bad" can only be determined by listening. If ever there

is a case where something measures bad, but sounds good, then you have

incorrectly correlated the measurement. Kinda like everyone that

tries to get their frequency response to measure flat in a room...even

a perfect speaker in a perfect room won't measure flat. So obviously

that which defines "bad frequency response" needs to be corrected.

[mas]

You guys scare me. [:-)]

The fundamental axial mode frequencies for 8, 12, & 14 feet are 69.78, 46.52, 39.87 Hz respectively.

The fundamental tangential mode frequencies for 8 foot high ceiling and a 12 foot and 14 feet wall are 14'/8': 80.36Hz; 12'/8': 83.86Hz; 12'/14': 61.27Hz.

...In your perfectly rectangular space. [:-)]

And while we can take the quote regarding measurements out of context and use it to champion subjectivity as so many are want to do. Rather it refers to using measurements by engineers without a thorough understanding of the principles to which they correspond.

And remember that these comments were made before time based measurements, where intelligibility is directly able to be interpreted by measurements.

You folks really need to read more than just his quotes and learn of the larger context and concerns in which he discussed issues among his contemporaries. And remember that not only did folks like Don Keele and Don Davis work with him, Dick Heyser and many more were friends.

[Rotorhead09]

Santa,

The ported version is a little lower in efficiency compared to the stock LS. Very cool that you still like them, especially after all the work you put into them.

Bruce

Bruce,

Did you ever get started on your project?? (ported LS) Last time we spoke you were going to try and build a set yourself. I really have enjoyed mine and since it was a diy project it makes me like them more...I have to admit I could not have built them without your help and the help of this site.

[Marvel]

I broke down and bought a real pair. I plan on making the box first, to see if I like them, then perhaps do the real mod on the cabs. I bought a set of SETs, my 2A3 Moondog amps and a BBX preamp. Have spent more money that I should have, being self indulgent. With a son getting married next weekend, the youngest heading back for his junior year tomorrow morning and a trip to China in Oct., I don't really need anything else to do... I really want to get things finished up with my gf, (reason for my trip to China), as she leaves Monday from the Philippines to go back to her teaching job in Nanchang. Man... that has to be confusing for everyone reading this. The short story would be... things will settle down and I'll build the ported boxes, to see if I like it (and do tests for Mike).

The credit for your LS clones shouldn't go to me. I just passed along info from others. [:$]

Bruce

[djk]

"You guys scare me. [:-)]"

Yet you're the one using 1116.48 ft per second (which corresponds to 59°F).

My value is based on about 75°F at 20% RH, about where my room sits with the AC on.

The speed of sound can also change with frequency, altitude, etc. I always use 1130 ft/sec, just to be consistent.

[IndyKlipschFan]

Mas said it earlier...

Rather than change your La Scalas.......

get a real bottom end....

I have converted a lot of people to this, too, but the Klipsch THX system bottom end of the KSW 120 speakers (2) with the KA 1000 Amp just ROCKS with la scalas..

If you were close by, I would say come over n hear for yourself.. it is THAT amazing..

[Marvel]

Roger, you are talking a significant price differential by adding a sub. And taking up more space as well.

Bruce

[Audio Flynn]

I would not mess with the folded horn and potentially lose the speed of attack and detail.

NOS Valves has tilted his LS back with a 1-2 inches that is a cheap method to improve lower bass perception. I think it worked real well for so little time and money.

[DizRotus]

I would not mess with the folded horn and potentially lose the speed of attack and detail.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

In my experience this did not happen. To the best of my knowledge, no one who has tried the mod has rejected it to return to stock. Those are opinions based on experience; all other opinions are based on speculation.

It would be interesting to hear from someone who actually tried it but didnt like it, and to learn why they didnt like it, If such a person exists.

[Rotorhead09]

I broke down and bought a real pair. I plan on making the box first, to see if I like them, then perhaps do the real mod on the cabs. I bought a set of SETs, my 2A3 Moondog amps and a BBX preamp. Have spent more money that I should have, being self indulgent. With a son getting married next weekend, the youngest heading back for his junior year tomorrow morning and a trip to China in Oct., I don't really need anything else to do... I really want to get things finished up with my gf, (reason for my trip to China), as she leaves Monday from the Philippines to go back to her teaching job in Nanchang. Man... that has to be confusing for everyone reading this. The short story would be... things will settle down and I'll build the ported boxes, to see if I like it (and do tests for Mike).

The credit for your LS clones shouldn't go to me. I just passed along info from others. [:$]

Bruce

I think you will like the mod if you ever get a chance to build your boxes...if not, it will be easy for you to go back stock.

Good luck on your trip to China...and say hello to all my kin folks!!!

I don't give you all the credit, but you deserve a lot of it because you answered all those hundreds of private emails that I sent you!

This is a great forum with lots of very knowledgeable people. I could not have done the project without it.

Santa