GoodSoundClub - Romy the Cat's Audio Site - High frequency and sharp filters

04-18-2008

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mats
Chicago
Posts 85
Joined on 09-18-2005

Post #:	21
Post ID:	7248
Reply to:	7244

Split bass

Gregm wrote:

"Basically I'm worried about a Lowther playing down to 150 and, if I cut the L higher, I'm worried about the woof trying to play up to say 200."

I have often wondered why one would want to ask the driver that plays into the 100 to 400Hz range, 1st order upper bass, also perform the duties of the lowermost frequencies. In my system I have limited the upper bass driver ( a 15" in a 3 cubic foot sealed box ) to 70Hz, thus sparing it from any really large excursions, as well as certain box issues. It is a rather unstrained sound.

Mats

04-18-2008

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	22
Post ID:	7251
Reply to:	7248

Networks as power sinks and source-able LF

Believe, me, I agree wholeheartedly that running the DX4 down to 150 Hz is sub-optimal. In my case it is a compromise that has more to do with working efficiency vs. aural continuity than SPLs. I have also though of adding a 10" to handle that narrow range, but which 10"? The Lowther is so freaking fast that it tends to leave other drivers for dead, and so crossovers tend to be too obvious/discontinuous.

Mats, I also agree that no driver should be wrung out, and I regard my own 40 Hz/15" as level matching rather than an assult on LF. Although I suppose 70 Hz limit would sound better, that is not low enough for me to enjoy music, and had I gone that way I would probably have bi-amped from the start. One way or the other, that last octave is elusive via FR SET/40 W, and my experience at dividing up the nether regions is limited, at least as far as SET is concerned.

Like we discussed up this thread, another factor is one's ability to aurally pinpoint a woofer operating at higher frequencies, and I suppose this would be especially true if the woofer is quite different from the Lowther. This is not something I've tried yet, but i can say that the 150 Hz was source-able only very rarely. Ironically, it was source-able when everything was otherwise at its considerable best and LF was really cranking. I figured out that the vent was just a tiny bit too big and a piece of weatherstripping actually made the woofer disappear. However, it is that close, in my experience, at 150 Hz.

At this point, using my present compromise as a reference, I just need a little more grunt at LF x-over point, which I think I can get by massaging x-over.

But that extra LF is elusive.

Greg, I look forward to hearing about your WE experiments.

Best regards,
Paul S

04-24-2008

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Gregm
Greece
Posts 91
Joined on 02-16-2005

Post #:	23
Post ID:	7285
Reply to:	7251

Results... a few days late

and not very encouraging.
The set up was as follows: a Lowther ex4 playing from ~12k down in a big ~100Hz tratrix. A Murata up on top, and a 15" Beyma on the bottom. The Beyma is in an Onken so the results may not be fully indicative of performance in other configs...

I tried a variety of combos for Lowther to Beyma and played with the 15's range as well (experiments using a dsp as electronic xover only -- i.e. no delays -- then switched to a makeshift simple passive filter for the "best sounding" result.

To cut a long story short, the "best sounding" result in that context was: Lowther 200-220, Beyma 50-~200. All other solutions with the Lowther playing lower sounded somewhat honky.

The Lowther cut off higher made the mid-bass lumpy (the Beyma didn't have enough magnet strength? wasn't "fast" enough?).

Amps as before 300b / 2a3 / an old Audiolab. For full range duties I used the Audiolab, the 300b's 7 watts didn't get us anywhere (not even whispering).
I'll try again with a stronger SET.

04-25-2008

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Gregm
Greece
Posts 91
Joined on 02-16-2005

Post #:	25
Post ID:	7289
Reply to:	7286

Stretching it

Paul -- I used 1st order & bandpass on the Beyma. I think that 2nd on the Lowther would have been better.

I set out to try and extend one "way" from the end of a wide-range drive unit, downwards. This I found to be well nigh impossible -- perhaps I should say, improbable. While I managed to get a commercially correct sound (i.e. I could measure all the frequencies were there) with 3-way, it just didn't sound right.There were sounds but no music* -- and a sort of "lumpiness" transiting b/ween one to the other.
*When I figure how to put this into words rather than mumbo-jumbo, I'll be sure to explain coherently.

Anyway, the best way of getting away with a 3-way spkr was using the dsp's 48dB/octave (hi & low pass) with delay. This of course, defeats the purpose of our experiment and required 3 amps (one for each "way") anyway. Unfortunately, I didn't have the components to try higher order passive filters.

The conclusion basically is, when the 15" was properly relegated to bass duties & the Lowther to pipsqueak duties, there was a midbass unit missing between the two. I.e., I couldn't integrate the two correctly, you could hear the transition from time to time UNLESS the 15" was cut off.

10-26-2008

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	26
Post ID:	8631
Reply to:	7289

To gain some efficiency & LF vs. DEBZ

Like I said, Yoshi's gift of de-whizzered Reps got me thinking of better efficiency and more "weight".

So far, I've got this:

A pair of Eminence Kappa 18" in ~ 6 cu. ft BR box to ~250 Hz; de-whizzered Lowther DX-4 PLUS de-whizzered Reps in OB to ~ 6k Hz; Selenium T-324 tweeter. If it needs more "air"/HF ambience, phase in Fountek/Audaphon JP2 > 10 k Hz.

This should be about 102 dB efficient from ~ 35 Hz. I don't know about small phenolic "bullet" tweeter, but I suspect it would ease electricity pain, and ribbon could be via an L-pad.

Paul S

11-01-2009

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	27
Post ID:	12115
Reply to:	8631

Current "Thinking"

This stuff has been stuck in my mind for some time now, working around in there against my ongoing experience, against what I am now running. The goal is a more dynamic presentation with better spectral balance, with the emphasis on LF and [more] correct harmonic development top to bottom.

At this point I am not at all sure it is possible to do FR with one SET amp, at all. Somehow, everything I model winds up seeming to need at least two amps per side, with one amp just for LF. This notion is based on my cold, objective assessments of the "LF" I now get and mental "simulations" of what it would take to get enough LF energy in my present room to effectively balance off the SPLs presented in the present power band my system provides.

In this case, I mean LF on a par with the best the rest of my system has to offer. While I presently use BR for efficiency, it would be nice to have the LF integration and solidity provided by a sealed system. And I am pretty well convinced by now that this alone makes FR SET all but impossible.

Just now I am thinking for each side: four 15" bass drivers (sealed?); one Supravox GMF 285; 1 de-whizzered Reps; 1 modified Selenium 324 tweeter; 1 Audiphon ribbon.

All of a sudden, we're looking at five channels per side!

But at least we don't have to develop each horn, too...

Paul S

06-17-2010

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	28
Post ID:	13788
Reply to:	12115

Crossing Over

This is sort of a "preliminary" post, to air some of the thoughts that will lead to my next disaster, which I will tell about once I begin to get some actual results. My thinking is still about the same as it was when I made the 11-01-09 post; but some of the ways I have been thinking about the results themselves have warped a little over time.

Basically, I have pretty much floundered when it comes to the subject of crossovers. The hellovitt is that speaker level XOs are the devil's tools. Despite what one thinks when plotting them out on paper, they are actually moving targets, in every sense of the word. Further, especially at lower frequencies, the very nature of the XOs themselves makes it almost impossible for the amp to do what the XO math says it will do.

While I was thrashing around on this subject, I may have caught a small break. I forget exactly what I was looking at a couple of days ago, but a link came up, and that led to another link, to Dick Olsher's site, where I found some ideas for much simpler XOs for speakers much like my own DEBZ; Dick gives all "updates" to anyone who's purchased any of his plans, at any point, and he sent me some more specific information to put in my XO oven. If the examples I got from Dick are not perfect for my own situation, yet they are of the right stripe, and it certainly got me to thinking about ways to try to get some of what I am after with drivers I already have, using mostly parts I also (ahem...) happen to have "on hand".

This post reminds me of those guys on TV, who yell and pump their fists before they ride a small bicycle off a roof...

Paul S

06-18-2010

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	29
Post ID:	13791
Reply to:	13788

Going Through Phases

Crossovers are so annoying, about impossible to nail down, and it's almost as though the more you study the problem, the fuzzier the "answer" gets.

For now, I would like to more or less forget about "phase" considerations, partly in order to get this thing rolling, and partly because I believe there is no perfect solution, in any case. I expect to make final decisions with my ears; I just hope I can get close enough to the XO points and lap curves I aim for to be able to reasonably evaluate the results by listening.

While I would still like to increase overall speaker efficiency, it's tougher than it looks at first. Part of the connundrum is that although additional drivers and channels raise the efficiency on paper, in fact the amp is further compromised by the added burden of all the added networking and feedback. Not to mention the "slice and dice" issues... I don't know if this makes "expanding" a wash, but I was thinking that for the present I'll just try to shift the frequencies around some while reducing XO parts count, and I'll see how that works to accomplish +/- the same things. I'll say more about LF to close, but generally speaking, one has a much easier path to hack if one simply lets go of real FR, going in.

Regarding the mid-top spectrum, a while back Yoshi sent me some Reps drivers that he had "castrated" by cutting off their whizzers. As it happens, I have been targeting the whizzers on my Lowther DX4s for a while and I am pretty sure that I could do better for that part of the frequency range. Simply put, I plan to sub the de-whizzered Reps for the DX4s and run the Audaphon ribbon down a little. I'll keep the lower notch filter I used for the DX4s for the nonce, and I'll just let the Reps run out of HF steam on their own, hoping they will meet the ribbons 1/2 way near 6.5k Hz. Yes, this violates my own ">8k Hz Ribbon Rule", but not by much, and so what? More on the XO changes, anon.

Regarding the low-mid spectrum, I mentioned in another post that my 15" Audax woofers were short on tone over about 125 Hz. Taking a harder look at this (ie, actually looking...), it's no wonder, since they are presently burdened with a very complex 3rd order XO at 100 Hz! I will run them up and I will run the Rep's high pass XO up to a 1st order 450 Hz from the DX4's present 2nd order 150 Hz high pass.

The aim here is to add weight to balance, gain better high-SPL-upper-mid clarity and balance, and make a more direct connection with the ML2s. If I wind up with "real", "spiky" "treble", I will be stoked! This will not address LF, of course. In the context of this thread, I apologize, but I am resigned that true LF will take more amps and more boxes. Present "LF" target is -3 dB @ 40 HZ with no help from the room; ie, business as usual.

Paul S

07-03-2010

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	30
Post ID:	13913
Reply to:	13791

Coddling One's Inner Nerd

The new parts I needed to build the new crosovers arrived about a week ago, but I have been otherwise busy (for a change...), and now I've managed to get sick, so I am still only mentally toying with the project. I will try to work in some bread boarding, at least, this weekend. Anyway, here is what I actually ordered parts for: For the 15" Audax PR380M2, I decided to start with 1st order low pass at 200 Hz (for a 300 Hz XO). This will be an octave higher than it's crossed now, and I'll also be relaxing the slope from the present 3rd order XO. Again, the idea is to add weight in that range. I will also add a notch filter at this driver's 1,500 Hz resonance peak (better safe than sorry...), even though that big motor effectively stifles HF on its own. For the Reps, I will high pass it at 6 dB at 400 Hz (ie., 300 Hz XO),and I will use a 2,200 Hz notch filter for its peak. Present Lowther high pass is 200 Hz, 2nd order. The Lowther-alike Reps will be allowed to run as high as it wants, without its whizzer, and the Audaphon ribbon will come in at about 8k Hz, but 3rd order, rather than it's present 2nd order high pass near 15k Hz. Here, the idea is to sluff "HF" (and quell HF noise). Although all this should allow decent phase relationships (once I flip the ribbon's leads...), who can be sure of these things ahead of time? This ribbon does have a built-in circuit that keeps its own impedance constant, however, which is way cool compared to the wild swings of most ribbons, which make figuring XOs for them extra tough.

I'm presently hatching a plan for a straight-to-the-point "separate" ULF that some purists here are probably going to sniff at.

But, first things first...

Paul S

07-04-2010

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haralanov

Bulgaria
Posts 130
Joined on 05-20-2008

Post #:	31
Post ID:	13914
Reply to:	13913

Do not use ribbons sooo low

Paul S wrote:
For the Reps I will use a 2,200 Hz notch filter for its peak

Paul, why don’t you try to fix the problem of the Reps driver instead of notching it? There is a reason for the peak and I do not consider the problem could be solved using rejecting filters.

Paul S wrote:
Audaphon ribbon will come in at about 8k Hz, but 3rd order

Is that the same tweeter like this:

http://www.madisound.com/store/product_info.php?manufacturers_id=132&products_id=1557

If it is, I have to tell you I had an opportunity to make experiments with this driver. The first thing I noticed is that the driver had an absolutely horrifying tone! It doesn’t worth even $1…
The ribbon is 100% tonally blind and if the crossover point is lower than 15kHz the driver sound honky as if you speak with your nose closed, despite the big effective size of the ribbon. If you use this tweeter lower than 10kHz your system will be totally unlistenable because you cannot reproduce the proper tone of harmonics.
Think of the tweeter as a natural extension of your midrange driver – they must operate on the same principle and they must have identical materials for their moving systems. The Reps demands paper HF driver with very small voice coil and alnico magnet system - something like this:

my alnico tweeter v2.jpg

"If you can't explain it simply, you don't understand it well enough." -A.E.

07-04-2010

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	32
Post ID:	13915
Reply to:	13914

Death by Ribbon?

Haralanov, as far as I know, Madisound does not offer my ribbon. Mine is not a stock Fountek, but it is a re-worked version of the old, discontinued Fountek JP2, a very narrow "naked" ribbon (ie,. no coating), and 97+ dB efficient. I got my Audaphon JP2 from the Lautsprecher Shoppe, in Deutschland. I think it is "rated" to XO at 2K with a 3rd order curve, although I would not dream of doing this. As it happens, however, I agree that ribbons lack tone, and they also lack texture, so this will be an experiment for me to run it this low. I am counting on the Reps to parallel , of course. I had thought to try the 101 dB (phenolic) Selenium ST324 for that range, and I may yet give it a go, depending on how this re-arranging of the spectrum works out in terms of balance and dynamics. This is just the first round, after all...

Regarding the notch filters, I consider them the lesser of evils rather than a "cure". I have no serious idea how to completely "solve" the Lowther-alike problems in order to get what I like from them without penalties. Although I have, over many years, found a few drivers I've liked better in terms of tone through a fairly narrow range, I have not found other direct radiator drivers this efficient and dynamic over anywhere near this wide a range (4 1/2 octaves, in this case).

I also agree intellectually about the paper tweeter, or maybe even a silk dome. Now, find me one that is ~99 dB efficient. I haven't seen anything like this in over a decade, and I don't have the patience to wait until I find and acquire something like this, IF it exists.

From your own posts and photos, it appears that you are presently interested mostly in tone. So, you must be ever on the hunt for the great old Peerless, etc. Also, judging from the photos you have posted, you are presently settling for a more sedate presention and a narrower frequency range than I would want at this time.

This thread is titled "Speakers for a Powerful SET", and the opening idea was to try for FR with one SET. At this point, I am still struggling with the one amp limitation, even though I've let go of anything significant under 40 Hz.

If/when I add real subs, I will also try to shrink and seal the Audax boxes and run them only to 50-70 Hz, something like that. While I do not totally disregard Thiel-Small info, neither do I regard it as Gospel. One does have to listen at some point.

Best regards,
Paul S

07-04-2010

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Romy the Cat

Boston, MA
Posts 10,156
Joined on 05-28-2004

Post #:	34
Post ID:	13920
Reply to:	13914

High frequency and sharp filters

haralanov wrote:
The ribbon is 100% tonally … If you use this tweeter lower than 10kHz your system will be totally unlistenable because you cannot reproduce the proper tone of harmonics.

It is pretty much what I found as well during my experiments with Water Drop tweeter and other ribbons
I played with. Ribbons are toneless by nature and I wish people understand it. Well, they do have tone but it is extremely primitive tone and very predetermined overly hygienic tone – making all music to sound the same. I think a ribbon must not be used for anything by HF artifacts, which in my view start after 10K. High frequency and sharp filters (ribbon and first order does not exist in nature) is the only place what I think true ribbon need to be used. It all was in the older corresponding posts….

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

07-05-2010

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haralanov

Bulgaria
Posts 130
Joined on 05-20-2008

Post #:	35
Post ID:	13921
Reply to:	13915

Tone and tonal integration

It’s a bit offtopic, but:

Paul S wrote:
I haven't seen anything like this in over a decade, and I don't have the patience to wait until I find and acquire something like this, IF it exists.

The problem is that it does not exist… Simply there are no customer demands on the market for such a product, not to mention it does look like shit. If it is not shiny and good looking there will be no sales, so… And the most ridicules thing is that it is unbelieveably cheap to produce!

Paul S wrote:
Also, judging from the photos you have posted, you are presently settling for a more sedate presention and a narrower frequency range than I would want at this time.

I think the picture misleads you. The cone of my HF/UHF driver is only 55mm in diameter (it is deliberately ragged around its apex) and the voice coil has almost no inductance so it has almost no limitation of frequency response and because of the very low moving mass and strong motor it has 98dB efficiency. I have listened almost all of the tweeters that industry offers with all imaginary extended frequency responses but all of them sounded “closed in”. An exception of this list is Fostex T500a Mk2. A friend of mine bought a pair, so I had an opportunity to do some experiments:

The subjective feeling it gives is the harmonics goes to forever – very open sound, but also very very sharp. It is like someone shoot you in your face with needles, no matter how high you cross it and no matter if you have good SET and good electricity. In addition to that, it does not integrates tonally if you use paper midrange - no matter what you do, so you need very specific tweeter for your Reps driver. You may not believe me, but my small paper tweeter sound even more open – it allows you to hear very subtle nuances of the original acoustic space of recordings. T500a also present this effect, but to much lesser degree – as you look through very small audio window and actually it does not transports you at the original location where the music was played.

One year ago, I also used a ribbon tweeter, the I trashed it and now I don't even want to remember that time :-))

Best Regards,
Haralanov

"If you can't explain it simply, you don't understand it well enough." -A.E.

07-10-2010

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	36
Post ID:	13967
Reply to:	13921

You Can't Always Get What You Want

Haralanov, let me know if you actually have something, otherwise I will continue with the Audaphon ribbon for the first round of the downward-pitching exercise. On the one hand, I wish I'd kept the Peerless 2" paper tweeters I had; on the other hand, they were only about 89 dB, or something like that. In fact, all those great old Peerless drivers were no more than 90 dB, as I recall. The Audaphon is actually very good for "non-present" HF; but... it is a ribbon.

Not the most useful place for this warning, I suppose, but folks should be careful what they stick parts to boards with. I made the mistake of commissioning some crossovers from Madisound a few years back, and whatever glue they used has fused with the cap wrappings, and it sticks everything together like SuperGlue! Who needs anything so serious for sticking parts down?!?

I hope to get most of the hack work done tomorrow.

Today, I hate DIY more than usual!!!

Best regards,
Paul S

07-30-2010

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	37
Post ID:	14146
Reply to:	13967

Wow! It Actually Works!

Too soon to begin in-depth descriptions, but after a good deal more work (and expense...) than I'd bargained for, it did not blow up, and there was not the all-too-usual painful silence in lieu of the first expected sounds. I admit I was as surprised as I was pleased when it started making music, right away; no problems of any kind!

Ironically, after all the changes, it is not so very different at this point. The main benefit now is better integrated upper bass and a good deal more "ease" through the midrange. The Reps is Alnico (versus the Lowther DX4's Neodynium magnet), and so far the Alnico makes for more upward-striving harmonics; nice and comfy, but upwards, like my previous Alnicos. So far, the Reps seems to be slightly "faster" than the DX4, but this might just be a certain clarity the Reps gained when Yoshi cut its whizzer off. I can't say yet.

Ironically, despite the upward stretching (so far...) harmonics, plucked and bowed basses and cellos have more deeply resonant bodies, and left hand piano is richer. Of course, this may have more to do with running the Audax up to 200 Hz (from 100) and using a 1st order filter (instead of 3rd order). Just maybe...

I'm going to let the Reps' notch filter (at ~ 2.3k Hz) settle in before I comment on dropping the ribbon down to 8k Hz. At this point, there are some minuses, but there are also some pluses with the new HF arrangement.

Today, for the first test, I used the ML2s' 8 Ohm taps. I will of course try the 16 Ohm taps again once I establish an aural reference.

Summing: At least as much Music, from less hi-fi.

Paul S

08-01-2010

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	38
Post ID:	14154
Reply to:	14146

Now the Real Work Begins

OK, maybe I got too zealous with the notch filter for the Reps. I aimed to bring it down 6 dB at ~2.2k Hz, using .47 mH and 10 uF against 10 Ohms for the notch, with the Reps itself at 7 Ohms. Right now, drums are too backed off, there is no "hair" to speak of on bowed strings, and I am still waiting for "spiky" treble. I am debating whether to put some kind of clips on the notch filter so I can play with parallel resistors until I get a better sense of what's going on there. Needless to say, of all the parts I do have, I don't seem to have any small-value, 12 Watt Mills resistors...

Not to divide this up like a "reviewer", but HF sounds a little bit "detached" now. It may well be OK, once the upper-mids/lower treble are balanced out; hard to say against an apparent trough. Just now, I suspect that, if anything, I might have to raise the HF x/o a little; it sounds like a slight peak at the HF x/o, exagerated by the trough below.

Midrange soundfield is very clean, calm, relaxed and "extended". It easily "swallows" the LF, and it seems like just the clear, empty soundfield for the "spiky treble" to emerge from, once the "spikes" are there to be had.

Upper bass is indeed much better; I am pleased with the tone that the harder-working Audax is developing; however, BR is still BR. Of course, I would have to double the woofers to go with sealed...

A possible generic point of interest: The extended-range Audax is still not "source-able", at all. In fact, bass imaging is now by far the best I've ever had. Upright bass is now totally detached from the speakers, and it stands alone in the soundfield.

I'm trying to keep in mind that I've used many new parts for this experiment, including the long-unused Reps, and I've added new duties for the Audax and the Audaphon, so I don't want to get too hung-up on any of this too soon. Not to mention that I have to "break myself in" to the new sound, also.

I don't know why for sure, but what I hate worst about tuning is the emperical work (sweeps, etc.). Still, it must be done at some point -- unless I just luck into "success"(!)...

Paul S

08-02-2010

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Paul S
San Diego, California, USA
Posts 2,657
Joined on 10-12-2006

Post #:	39
Post ID:	14157
Reply to:	14154

In Place of My Bowler, a Dunce Cap, or...

...It's about the Curve, Dummy!

This morning I disconnected the notch filter and listened as long as I could stand it. Not long!

Then, I went over my math and remembered that I went the way I did largely because I "already had the parts".

After an extra cup of coffee, I got a good deal more serious with the numbers and I realized right away that although I had centered the filter well enough, it was rather a broad swath compared to the VERY SHARP resonance I want to damp, and my half-assed filter had made troughs on both sides of a softly rounded rise.

So, it's back to Parts Frenzy for the stuff I don't have (...how can there still be anything I don't already have?).

Hard to believe anyone can actually just sit and listen to these things without a filter! I will either temp up the old notch or do something other than hi-fi until I get a filter on that spike.

On the Plus Side, the Reps are imaging significantly better than the DX4s did (and the DX4s are pretty good...).

Off the cuff, to Stock Lowther Lovers and DIY Guys: I guess I just don't get the Big Attraction!

Paul S

08-03-2010

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haralanov

Bulgaria
Posts 130
Joined on 05-20-2008

Post #:	40
Post ID:	14164
Reply to:	14157

Notch filters remedy - the the ultimate illusion

Paul S wrote:
... VERY SHARP resonance I want to damp

Paul, this sharp resonance peak is indication of time domain problem (it could be seen on a CSD plot), and it cannot be damped just by using electrical circuits with the driver, because they only lower the amplitude of the musical signal at that frequency, but the resonance and the processes that form that resonance are still there. Generally speaking, you try to cure one evil with another evil - do you think it is the proper solution? Why don't you try to find out what cause the driver's anomaly and to fix the problem the way it must be fixed?

"If you can't explain it simply, you don't understand it well enough." -A.E.

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