Spike La Scalas?

[Islander]

I'm well pleased with the sound of my La Scalas, but I wonder if putting them on cones or spikes might improve fine detail and imaging.

My previous speakers were only twelve inches from front to back, and they were a bit wobbly on the thick carpet. I put some peel-and-stick cones under them (to avoid drilling into the cabinets) and was pleased with the results, after the sticky-backed foam pads bedded in after a day or so.

They were only $3.95 each from Madisound and four of them work well on 55-pound speakers, but more might be needed on the 125-pound La Scalas.

http://www.madisound.com/cgi-bin/index.cgi?cart_id=%Êrt_id%%&pid=1603

http://www.madisound.com/cgi-bin/index.cgi?exact_match=yes&product=TT&cart_id=%25Êrt_id%25%25

The La Scalas are two feet front-to-back and aren't as wobbly on the carpet, but there is room for improvement. Does anyone have any experience with or recommendations about using cones or spikes?

Pat on the Island

[Daddy Dee]

I would think you'd be pleased with the results. It sure would make them a challenge to move on carpet, though.

There's a thread or two in the archives where HDBRBuilder extols the virtues of putting some rubber footies or skids or something on LaScala bottoms for use on a hardwood type floor. He describes an improvement with this treatment. The grabbers are available at Wal-Mart.

[JohnA]

We discussed this years ago.

It won't hurt.

It won't help. The reason for spikes is to anchor the speaker on

the floor and help it resist fore and aft motion caused by the woofer

(no kidding). Though minute, some think the woofer can move the

cabinet enough to change the tweeter's sound. Because of the La

Scala's footprint, it is stable (and heavy) enough that the woofer

can't cause cabinet motion.

[arfandbark]

I was hoping for just such an answer, John.

I knew my Cornwalls weren't moving back no matter how hard I pushed them and if that's the only reason for spikes I certainly don't need them.

They just don't move themselves.

Thank You.

[Islander]

Thanks for the answers, guys. One less job to do, one more opportunity to listen to music!

Pat on the Island

[mas]

Hi folks...

I just thought that I would toss out a couple of ideas to put things into context and hopefully to stimulate a bit of thought. I hope you will pardon any statements intended with a grin and maybe a twinge of sarcasm - its all meant in good fun.

So, given our scenario, let us look at two primary areas of interest. The first, the actual movement of the cabinet. And second, the effect of such movement on signals in the time domain.

And then, I want us to stop for a second and examine the suppositions that we are making relative to discussions of various topics that are common on the site. In this, I hope that some will see a bit of irony and just a bit of humor. And hopefully people will be stimulated to think a bit and to at least put their assumptions in line with their ideology - or, visa versa.[]

So, for discussion sake, let us assume that without tight coupling to the floor that the speaker will move. Let's also assume that the woofer is the primary 'driving ' force as it constitutes the largest moving mass in the speaker.

Now, perhaps we should ignore that fact that normal operation will result is a very rapid bi-directional movement in the cone each second - meaning, it moves in opposing directions. And let's ignore the fact that such rapid motion 'back and forth' in a linear manner will tend to offset each other in 'macro' time. So such motion would have to occur in 'micro' time. And if we assume a limited frequency response (upper limit) of the woofer, we might potentially establish a resonance, as I seriously doubt that the massive cabinet is going to be accelerated in micro time in tight accordance with the woofer. Heck, one could make the argument that cabinets like the LaScala are difficult to 'accelerate' in macro time - especially if you have ever tried to move them yourself!

The other scenario that we could posit to examine this phenomena would be a large impulse signal - say on the magnitude the Dafos drum recording. If you are not familiar with the grandaddy of all recorded LF test signals...think a Giant cannon shot. In this scenario we would not be worried about accelerating a Large cabinet mass via many small rapid offsetting cone movements per second, but rather a large discrete cone movement. (And we will conveniently ignore the 'other half' of the cone movement rather like the Roadrunner cartoons ignore certain aspects of real world physics.)

Lets say that on a very slippery masonry tile floor that we could get that cabinet to move. And given the force, let's say we could potentially move that cabinet 1/16 of an inch. Now, realize that this amount of movement is huge relative to the mass of the cabinet and the motion and force of the cone movement...but we are trying to make a point here so a little hyperbole is being employed.

IF we could accelerate the cabinet, this motion would result in an effect on the signal in the time domain. As moving forward (since we are ignoring the fact that the cone also moves backwards and we are assuming a perfectly damped driver (hey - I can dream can't I []), the phase of the signal will change. And as we all know, phase is simply a change in time - in this case, the time of a signal's origin affected by the position of the signal's origin. More precisely, it will result in a change of the rate of phase of the signal. As in my ideal experiment here, we assume that the cabinet will be accelerated backwards by the forward motion of the woofer in real time - in other words, there is no lag, but rather the cabinet will move with the arrival of the impulse energy. (But please be aware, in the real world the cabinet would actually be accelerated in a time frame more in keeping with the time frame some of you embody such as when your significant other asks you to stop watching the football game and to help her sort laundry. In other words, the motion would not be instantaneous.)

So you ask. what is this guy driving at. Well, let me tell you. The motion of the cabinet would cause a change in the rate of change of the phase. If any of you followed the discussion several weeks ago, this is also known as group delay. It is the micro level changes in the changes in phase - as the speaker is already moving and changing phase with the input signal - further altered by a moving cabinet housing the mounted speaker.

So, IF you could actually accelerate the large massive cabinet, you would be altering the group delay and causing it to be skewed by quite allot. Is this audible? (This should lead to research into the Haas effect and other issues that will be addressed in the L&S Room acoustics sessions in the Architectural section if anyone ever reads the material so that we can proceed! Sorry - I couldn't resist the plug...[])

Now, let's step back a minute (and this is where I must warn a few who maintain that aligning signals in the time domain is a superfluous exercise to cover their ears (eyes) or to leave the room - think: its a good time to go get a beer...). If aligning signals that may be offset by as much as several feet is not considered important (and I believe it IS), then why would motion on the scale of 1/16 of an inch matter? Conversely, if motion on the exaggerated magnitude of 1/16 of an inch matters, why in the heck would offsets of up to several feet between the acoustic origins of several drivers reproducing the total signal bandpass not matter? And if some choose to believe that such a small error in group delay is important, why in the heck have you not already employed active crossovers with delay for the much larger and more significan aspects of this issue?

But, the other position is that such minute issues as mechanically induced group delay may not be significant, but much larger time domain errors are significant. And in the world of compromise and non-ideal systems, doesn't it make sense to put your effort into addressing those issues that have the greatest return for your effort and money?

Now I have grossly over-simplified the dynamics and grossly exaggerated the effect (motion) of the cabinet to create my simple example, but I hope that you will put this issue into perspective. But please do not misinterpret my intent as one implying that you should just forget this issue and ignore it. It simply points to a much larger and more important issue - and that is the 100 ton elephant in the middle of the room - the issue of aligning signals in the time domain. And like it or not, it is an issue of significant importance.

And I haven't even touched on the debate many delight in between the camps who feel that you should decouple the instrument from the surface with fancy 'half tennis ball' feet costing , well, allot more than several tennis balls cut in half!, versus those insisting that tightly coupling an instrument with pointy feet to a stable surface provides an appeciable sonic benefit. But I dare say this debate quickly becomes even more humorous, as 'common sense' is not necessarilly your best friend here! []

OK, now that I have stirred the pot a bit, I will take my leave and go back to worrying about really important issues such as my Bombay cat (1/3 dog and 2/3 monkey) having destroyed my desk by deciding that all of my neatly arranged piles of past due work would look nicer on the floor and all just because I did not provide adequate attention to him as he sprawled across my desk staring at me upside down... oh my...where do I start?...maybe if I had only put 'tiptoes' on the piles...[]

[PrestonTom]

Well MAS may have stirred things up a bit with his interesting thought experiment.

One view was that coupling the the cabinet to the floor would help you "feel" the bass. Perhaps this is not really an auditory experience, but I can't imagine that this would be a very effective way of transmitting vibration given the various impedance mis-matches and other structural issues. I think this vibratory experience is part of the fascination with sub-woofers. I also remember that this type of coupling was sporadically used in movie theater set ups for special screenings (I believe "Earthquake" and some war movies etc).

Another view is that if the cabinet is rocking back and forth, the sound from the woofer and from the tweeters will suffer a form of frequency modulation (think of the Doppler effect, i.e., the change in pitch as a train or car passes by). In this case the Doppler shift would be dynamically changing. Again if you do a back of the envelope calculation the the degree of frequency modulation would be minimal (physically). I would think this amount be inaudible.

Spiking into a hardwood floor would certainly require some explaining to your spouse...

-Tom

[ricktate]

The way i understood it from HDBR..Andy...and the reason i tried the Grippers was that the speaker needs to be hooked up to the floor but also separated from it.I think spikes would transmit vibration to the floor resulting in muddy bass.I wish i had done A-B tes when i put Grippers on my Scalas awhile back but now i got my Ks in living room on Grippers to.I would guess this only works on smooth hard floors....not sure about the carpet ideas, i had carpet before.Oh well just a thought.Rick

[Islander]

The concept with spikes (or better, cones) is that they both lock the speakers to the floor so they can't move and decouple them from the floor since the sharp points provide a strong impedance mismatch, meaning the energy is not transmitted to the floor, but stays in the speakers.

As for the amount of movement, on carpet at least, the cabinets barely move at all with a push of a finger, but can be made to jiggle. Not so much with large-footprint speakers like La Scalas, of course. That jiggle might be sufficient to disrupt microdetail info like, for example, the sense of the size of the room where the music is performed, reducing the transparency of the presentation.

It's not a big difference, but the more revealing the system, the more the microdetails matter. I may try Vibrapods under my receiver. Not expensive, and there just may be something there.

Pat on the Island

[gonzp]

Last April at the AudioKarma audio fest in Detroit, Craig propped the front of his LaScallas up with some miniature shampoo bottles. About two inches, It made a very noticeable improvement. The speakers seemed to load up the room better. The perception of more bass was evident, I believe, due to the fact that the speakers were aimed more at your ears. When I got home I immediately made some risers for my LaScallas. I am quite happy! YMMV.

[DrWho]

The concept with spikes (or better, cones) is

that they both lock the speakers to the floor so they can't move and

decouple them from the floor since the sharp points provide a strong

impedance mismatch, meaning the energy is not transmitted to the floor,

but stays in the speakers.

As for the amount of movement, on carpet at least, the cabinets

barely move at all with a push of a finger, but can be made to jiggle.

Not so much with large-footprint speakers like La Scalas, of course.

That jiggle might be sufficient to disrupt microdetail info like, for

example, the sense of the size of the room where the music is

performed, reducing the transparency of the presentation.

It's not a big difference, but the more revealing the system, the

more the microdetails matter. I may try Vibrapods under my receiver.

Not expensive, and there just may be something there.

Pat on the Island

Pat on the Island,

If I may humbly comment on your point in light of what MAS was trying

to say (holy crap, mas...I was dying laughing by the first paragraph

since I knew where you were going) []

But seriously, if you are indeed worried about the "micro details" to

most faithfully reproduce the size of the room in the recording, then

might I suggest tweaking your perspective a little bit. The small

wiggle you notice on the carpet is the same thing as skewing the

signal-alignment of the system...it's just a constantly changing

misalignment. If this small 1/16" change is audible (which I feel it

is), then why not also address the 30" and 8" issues that are always an

issue with the speaker itself?

The annoying thing about everything audio is that you need to think in terms

of wavelength, which means that issues start at a single lowest

frequency and then also exist with every harmonic above it. The bigger

signal offsets of the speaker are going to cause issues at more

frequencies than the smaller issues from the cabinet vibration because

they start occuring at lower frequencies.

So by all means let's put spikes on our speakers - we might even notice

an improvement. But I would also encourage people to consider other

identical issues that have far larger effects on the sound.

Also, in light of the lascala I would recommend damping the side walls

of the bass bin - like what Klipsch did with the new Lascala II. I

would worry more about them super flexing walls than some minor cabinet

wiggle.

[Islander]

Thanks for the tips, Dr. Who and gonzp. I agree that the bass horn sidewalls are pretty flexy and I've seen that a few people have put triangular braces in the horn to stiffen them.

A few questions: do the braces make an audible difference? Also, while it appears easy to screw the outer edge of the brace to the enclosure (from the outside), attaching the inner edge to the horn vee looks less simple. So is it worth doing, and how is it done?

Another approach would be to attach a sheet of plywood to the left and right sides of the enclosure, the same size as the side panels. It would stiffen the whole assembly and add visual weight to the bass bin, which looks a little spindly to my eyes, unlike the La Scala II bass bin.

The stiffener sheets would have to be stained to match the enclosures and would make them an inch-and-a-half wider (with 3/4" plywood) as well as adding some damping weight. Does this sound like a good idea?

Since I'm using a subwoofer to fill in the bottom end, would cabinet mods really be worthwhile?

As for tipping up the speakers, I just put some plastic pads under them this afternoon, raising the bottom fronts of the speakers 2" off the floor. The bass seems unchanged, even when checked with an SPL meter, but the speakers seem brighter to the point of edginess. I'll try it for a day or two to be sure, but the initial impression is that they're harsh sounding, even with mellow CDs.

Pat on the Island

[DrWho]

Another frustrating aspect with bracing on the inside is that the V is

never perfectly aligned in the middle [] (I didn't believe it until

Trey pulled out a ruler and showed us). It has no large affect on the

sound of the speaker due to the wavelengths in question, but it makes

internal bracing most annoying. So in light of that, I would be more

inclined to add panels to the outter walls - like with the Lascala II

(which also happens to be a verified approach). Mark from Klipsch

mentioned that the vocing is so different that they had to overhaul the

crossover to retrieve tonal balance.

As far as the extra edge you notice by tipping up your speakers...it

makes sense that the bass doesn't change (again because of the size of

the wavelengths). The brightness is probably the result of putting your

ears more on-axis with the squaker/tweeter - which as a byproduct of

their exponential expansion rate have a beamy response. The higher

passband of the squaker and tweeter reduces in output as you move

off-axis...so you can think of tilting the speaker up as adding EQ

around 4500Hz and ~16kHz. You are probably also making more audible the

9kHz spike from the squaker which is the result of the phasing plugs

being used. Steeper slope crossovers apparently reduce this

significantly. And just to go the extra mile, you are also changing the

reflection patterns in the room by aiming the speakers in different

directions...a speaker that is more on-axis should generally appear to

be "brighter" as compared to a speaker firing away from you - which can

additionally add to the extra edge that you're percieving.

So all that said - there's a lot of crap that can be going on. One

approach would be to pull out some measurement toys to try and quantify

where your major issues are and then address those issues. Another

approach would be to replace and rebuild everything and hope shooting

in the dark gets you a bit closer to the target. In the end, trust your

ears and enjoy the hobby. Sounds like you're in a prime position for a

lot of tinkering []

[Islander]

Thanks for the info, Dr. Who. You're a knowledgeable fellow. These speakers do seem to be more tinkerable than any others I've ever heard of. Even replacing the zip-cord (16 gauge?) lead-in wire from the back of the enclosures to the crossovers (my '74s have the crossovers mounted beside the squawker horns, not behind them) with 12 gauge speaker lead seemed to improve the bass response slightly, so that I was able to turn down the sub slightly.

As I mentioned to some of my motorcycling friends, the La Scalas are sort of like bikes, in that you can see the parts, they're not intimidating to work on, they have many dedicated fans, and people actually make aftermarket parts for them.

Finally, due to their sensitivity and ability to play really loud, the speakers are like a big sport bike: you don't back off the power because the machine is straining or making odd noises, you back it off because it's too damned windy!

Pat on the Island