High-resolution Speaker Frequency Response & Distortion Measurements and Why We Need Them

[@ovidiubarbu2057]

GR research customer base drops each time you post such a great video

[@JesusMartinez-mk6fc]

Awesome introductory masterclass on speaker measurements Amir! We hope that you'll follow-up with additional videos explaining other measurement specs for speakers.

[@AudioScienceReview]

Thank you and yes, that is planned.

[@BogdanWeiss]

Great introduction Amir 😃 Erin's Audio corner is another MUST go-to channel for honest & insightful loudspeaker reviews Klippel + subjective insights from a trained listener.

[@eddiejennings5262]

Hello Amir, I sincerely appreciate the technically mature nature of your videos; thank you. I appreciate your well-defined measurements; choices of algorithms for white-noise signals and observations and explicit specification of frequency resolution. Thank you.

[@graywyot]

Endless valuable information, and condensed knowledge. Big thanks, Amir!

[@anderse7039]

Thank you for continuously educating the hifi community! Since I am heavily into measurements and analysis right from the start, I had so many discussions with hifi friends that dismissed stats and measurements completely. And I understand why they do that: way too often the stats and graphs do not match the listening experience! Why? Because the numbers are made to look pretty - and the graphs as well. You know how to do that, we know it from you. But the average hifi enthusiast does not know that. We reached a point where manufacturers and marketing people have published so many misleading or outright manipulated data sheets that a large share of the community dismisses measurements altogether. That's a sad thing to watch.

[@davidlong1786]

What I hate are those that say "We can hear things that can't be measured." Uhhhhhh and you know that because?

[@anderse7039]

@@davidlong1786 As much as I agree with you, I think I know where this comes from: Bad measuring. Or outright forgery. There are speakers with almost matching data sheets and graphs out there, yet they sound very different. Because the data is flawed. But it's usually presented as definitive. We know that a 0° measurement alone means nothing. Yet all too often that's what people compare. Sellers taking advantage of uneducated (or ignorant) customers reinforce this vicious circle..

[@johncreech6012]

Great stuff. Thank you very much for continuing to contribute to the community. I learn something every time you post. Carry on!

[@tombarber8013]

Another very excellent, informative video by Amir. To be perfectly frank I don't think there has ever been anyone who did more for the audiophile community for so little in return. Just stating the obvious. In watching this video it becomes very apparent just how inherently difficult the task of measuring a loudspeaker's frequency response really is. To the novice who isn't deeply involved with this important aspect of loudspeaker engineering, it may seem that it is a simple matter of sweeping a tone from 20 Hz to 20 kHz and capturing readings of SPL along the way. But right off the bat there is a problem with this, because if you simply capture readings of SPL at each frequency, the reading will include the SPL contributions of the various harmonic distortion components produced by the speaker at each specific test tone frequency. You then have to ask whether the frequency response measurement should or shouldn't include this. Ultimately this is a philosophical question because there isn't any formula or equation to tell you the answer. If you include the distortion, you're measuring the speaker's total acoustic output for each frequency of stimulation, within the audio spectrum. But is this really what you want to measure? If you find that at 100 Hz there is a strong 2nd harmonic, then when the test tone is 200 Hz, should the extra 200 Hz energy emitted when the speaker is stimulated at 100 Hz be included in the response measurement for 200 Hz? Presumably not, and yet if you play white noise you will hear an emphasis at 200 Hz that won't be reflected in the measurements if you don't include, for the 200 Hz measurement, the 200 Hz acoustic energy emitted by the speaker when stimulated with frequencies other than 200 Hz. Clearly, there is nothing simple about a simple measurement of a loudspeaker's frequency response. Something that is conceptually simple is actually very complex. Amir has been personally committed to this field of knowledge for a very long while, and a major reason that he understands it better than many others is that he has an advantage that many of the other people who do videos for KZbin don't have. Amir's advantage is that in his pursuit of this knowledge, he has applied the kind of basic knowledge that, with very few exceptions, is only obtainable via formal education in high-quality schools. This is important, and it is something that certain other people who make videos for KZbin do not have. It is a bit irksome that there are people who, due to lack of knowledge and experience and just plain common sense, are disinclined to listen to Amir's advice and are more disposed to become apologists for snake oil peddlers.

[@edgar9651]

Thanks Amir! This video would be even better with some sample sounds. But I guess then it would be even longer. If you have the time for this then I am sure many of your interested viewers would like to hear more about this.

[@AudioScienceReview]

Good suggestion. I should have thought of that but didn't.

[@nicoras8803]

You only talk about harmonic distortion. However, one of the most likely distortions in speakers are intermodulation artefacts. Buy the way. Just as a matter of interest, the cheapest way to measure acoustics is probably in a windless open field with the driven element mounted half wavelength from the ground. Chirp is actually a radar signal generation function. Nice job Amir.

[@nicoras8803]

What pissed me off the most was Dany's claims that Amirs expensive and top-notch equipment is not relevant. He had the same attitude PS audio had when Amir tested their Power Converter. It is obvious that there is finite understanding in "hi-end" audio and most of the cost is contained in the mechanical and aesthetic presentation.

[@ThinkingBetter]

@@nicoras8803 It’s obvious that the audiophile business is driven by a combination of real science making the real audio fidelity and snake oil making the business margin. No audio system defies laws of science.

[@andysummersthxcinemaandmyc7748]

@@nicoras8803" yelp , yelp " danny meets the terminator kzbin.info/www/bejne/Y4bJhoakftyrfdk

[@davidlong1786]

@@nicoras8803 I stop listening to people's moaning about how their products are tested when they also sell snake oil cables and power cords. If you are a liar about one thing then of course you tend to come up with more lies to cover your ass in other departments.

[@frosty6845]

@@johndoh2121 Danny has no idea what he is talking about, I don't trust anything he says

[@kevincheong1516]

Again another brilliant educational piece. Danny from GR Research should learn from this video.

[@iamsometimes6712]

Danny does not seem to be in the business of learning at all. He intentionally cherry picks science points to support his business practices, but will ignore or bash science when convenient to him (like others measuring his speakers unfavorably), or will pseudo scientifically say 'measures the same but sounds different' about parts (although he NEVER properly measures them) to justify any kinds of audioquackery (burn-in, cable risers, tube connectors, ferrous nuts...). So yeah, @Lloyd Stout is spot on, it'd benefit more his audience. At least the ones who are still open minded / curious, not the ones who are too far gone down the personality cult road 😮‍💨

[@kevincheong1516]

@@iamsometimes6712 it is kind of disappointing to see unscrupulous salesman like Danny who would do almost anything just to promote their mediocre products. I am sure if he could resort to grinding dried up human foetus into powder and sprinkling them over his speakers and cables, just to promote some magical and mystical properties, he would do so without any hesitation.

[@raphofthehills4405]

​@@kevincheong1516 Good question. What would Danny do if he ran out of pixie dust 😂

[@kyron42]

I love these fundamental videos. Keep them coming. Thanks Amir.

[@johncarolan6908]

What a fantastic article. Just brilliant. Highly informative.

[@young_padawan]

I have noticed the GR research rep go from trying to put up some form of reasoning to just name calling. A nerve has been struck. This name calling by Danny, along with ASR's continued focus on only bringing attention to the engineering and facts , makes it very clear to me who/what to trust. Personal attacks is what someone does when they have nothing better to offer to the discussion. You're on a right track, good sir.

[@lurkersmith810]

Please don't apologize for a technical discussion about speakers! There are plenty of non-technical descriptions on KZbin, and some of us need more specific information besides words like "buttery" to describe speaker performance.

[@IsmaelMartinezPR]

Love it: "not all understand the intricacies on how signal process works" boom direct call out.

[@randallcollura]

Great, thanks for doing these kinds of videos!

[@Fix_It_Again_Tony]

I found the forum a couple days ago and I just realized today you have a KZbin channel. I'm an electronics engineer by training and I am so happy to see some objective discussion about audio - with measurements! I was a big fan of NWAVGuy until he fell off the face of the Earth years ago, I am sure he had his reasons. I just bought my fist "system" consisting of a Yamaha RX-V385 and a set of Emotiva TZero+ speakers. I feed it digital audio from CDs from a Sony UBP-X700. I think it have it sounding pretty good. I tried out the YPAO function of the AVR and it seems to do something, but can't quantify it. I was reading extensively about REW today and I have a UMIK-1 on the way. I figured that was probably one of the best investments I could make to improve sound quality. I am really looking forward to absorbing what I can from these videos and from the forum. My ultimate goal is to apply my knowledge of electronics to help others avoid paying way too much for good sound. Thank you so much for bringing some sanity to consumer audio. Tony

[@johnnydingo8680]

Great comeback, now to see what the response will be, if any 😊

[@teashea1]

A very good video. Intelligent, articulate and organized.

[@antong3987]

Amir, 'the community' would be best served if you did a complete video on the Principals of Acoustics and how it relates to audio. That's a key component of the science of hearing ...

[@theodoro89]

You should make a series that can get as technical as you like. Maths and everything.

[@Mrch33ky]

Great video. Lots to unpack. Will have to watch multiple times. Thanks Amir!

[@mauanderuk]

This was great many thanks as always.

[@komhst]

Great educational video! CONGRATULATIONS! Go on Amir.

[@erickuehne]

Can we get you and Danny on a live debate?? I think both of you would be up for it.

[@AudioScienceReview]

I am definitely game. Just need to find a neutral party to do it. Maybe Joe 'n Tell?

[@iamsometimes6712]

Awesome idea !

[@Finite-Tuning]

My man, another home run. Cheers 🍻

[@Adam.NavyVet]

Keep on Disproving the B.S and deceptive Marketing in the Audio world. The truth is hard to discover and your Videos are scientifically enlightening to help the Consumer avoid being taken advantage of by scrupulous Manufacturers. Such a seedy industry built around lies and myths. Keep illuminating the truth with engineering and science.

[@carlosmante]

".....help the Consumer avoid being taken advantage of by scrupulous Manufacturers"????? OMG.

[@Adam.NavyVet]

Just a typo, try not to lose your mind over it. Unscrupulous was intended.

[@pennpen]

I think this is a very good video for beginners. Fantastic .

[@hugobloemers4425]

Hi Amir, that is a great video. I learned something today and that can not be a bad thing :)

[@davidfuller581]

I always thought the argument of "but we hear in 1/3 octave bands!" to be just total nonsense. We can easily discern less than that (trained musicians down to a few cents), so why wouldn't we be able to hear narrow-Q tonality changes?

[@AudioScienceReview]

Indeed. Our hearing bandwidth at worst shrink to 1/4 octave at the top of the frequency range. Below that it continues to have narrower bandwidth/discrimination.

[@I_am-an-alien]

You typically just dont hear them and these "high resolution" measurements become more academic and less about being a design tool, if fact, this amount of resolution may hinder filter optimization.

[@AudioScienceReview]

@@I_am-an-alien Not really. You just need to understand the ERB and importantly, have the ability to perform AB tests of the filters to see if they are doing what you think they are.

[@I_am-an-alien]

@@AudioScienceReview my experience is in passive filter optimization where high Q slopes may not be obtainable without much added topology and really unnecessary, this would rarely if at all create a "better" sounding speaker. If fact, I used to turn off my "high Res" mode when doing measurements, just doesn't help.

[@bbfoto7248]

@@I_am-an-alien Well, his response and reasoning for higher resolution measurements was not only WRT crossover network filters, but also cabinet/enclosure and port resonances...and non-linearities in the transducers. But WRT network filters, we can do so much more precision and effective work (and now usually with much less cost) with DSP filters, and not have to worry so much about the topology/complexity, cost, size, and weight of passive component filter networks. Been using Pro Audio digital LMS for decades now...Behringer DCX-2496 Ultra-Curve Pro, DBX Driveracks, Rane RPM-88, DEQX, etc. And more recently the miniDSP C-DSP 8x12, and other 12v car audio industry multi-channel DSP/Amplifier units from companies such as Audiotec-Fischer (Helix), Audison Virtuoso (FIR), Mosconi Aerospace 8x12, ARC Audio PS8-50, Zapco HDSP-V. They are an excellent and fast/efficient design tool to get you to a final passive network design quickly as well. It's a simple matter to instantly switch between multiple network filter & PEQ Presets for comparative listening tests.

[@parkers8245]

I wonder if you asked a speaker manufacturer for this, like Focal, B&O, KEF etc, would they ever provide it? - Fantastic insight - thanks

[@AudioScienceReview]

Only a few companies in Pro space like Genelec and Neumann provide it. Sadly even the companies that have it internally won't publish it. I have been told that their marketing department thinks it is too much and would confuse customers! Hopefully this changes over time.

[@guycord]

This is exactly how B&O do their in-room calibration on BL90, 50, 28 and Theatre. Via DSP, highs and lows in the listening position are flattened out. Additionally, the BL90 do this on non-planar speakers (side and rear) to effectively cancel side and time-delayed reflections making resulting in minimal non-axis response. Result is ultra sharp 3D soundstage and image at the listening position

[@nicksundby]

Excellent video. Could you use a little bit thicker lines on the charts, they are quite difficult to see thanks.

[@AudioScienceReview]

Thanks. Yes, I need to do that. In video they are even harder to see.

[@xinxie24]

Thank you! I learnt so much!

[@vintageaudioreview]

Well done once again. Your 2nd career as a University Professor awaits...

[@AudioScienceReview]

Thanks. Truth to be told, for a decade I thought Unit Operating System internals at University of California (Santa Cruz). So I have a passion for conveying difficult topics to people with little experience in that field.

[@noridzwannordin6416]

@@AudioScienceReview "taught Unix" surely?

[@VegasVaron]

Informative video, thanks Amir.

[@dinsy512]

Nice! Thanks Amir! Very helpful!

[@andysummersthxcinemaandmyc7748]

another yet highly educational indispensable learning . next i guess compare movie dialogue for distortion and try and mimic the actor voice and spoken dialogue using test gear to see if distortion is detected ? wear earplugs use electric-shaver and report back what you hear ? 12:11 i know 100% , i do happen to have 165 IQ score . the pink noise that on some pro-logic that cycles around bit faster i have few that do , yamaha dsr70pro (hold on got do my Cats cat litter) 🐈i don't use that dsr70pro in the system rack anymore it's placed on rack shelf now . but when the pink noise cycled and with one channel reversed polarity , lower raised level by +- 1dB it stood out from rest of the channels , when measured tested into an audio mixer with just one output channel as all the channels was getting "summed up" . it was really a good test that i doubt most , top home theatres not even aware of ? the pink noise on these rubbish AVP AVP today us rubbish narrow band pink noise that a common CB radio outputs slope noise high around 1KHz and slopes off downwards to around 50Hz and slopes downwards to 9KHz . it's okay , okay for modulation speech not hi-fi . 6:23 i think that gr danny speaker (in the background) is affecting you're judgement i see you still have it as a paper weight . lol

[@CptMark]

Didn't know about the Sine Chirp, very interesting. Regarding THD measurements, we have relatively high tolerance level for THDs. Next step should be to investigate intermodulation of many signals in the transducers.

[@AudioScienceReview]

As I have noted elsewhere, intermodulation is very hard to measure. With one tone, I can set two speakers to have the same amplitude. With two tones, that is not possible if frequency response is different which is always the case with speakers. Change the ratio of those two tones and even if the distortion is the same, IMD will be different. There is also the challenge of which two tones to pick. Due to crossover frequencies varying, you can't be assured that the upper tone lands in the same driver.

[@Azzy_Mazzy]

Great video and explanation.

[@katalysis]

Many home theater receivers that have room EQ features (i.e. audyssey) play chirp tones through each speaker to do its EQ.

[@AudioScienceReview]

They do indeed. Long time ago though, they would either play white noise or MLS.

[@I_am-an-alien]

Amir, I agree that measurements are a very useful tool but please explain how speakers that measure similarly can sound very different and loudspeakers that measures very well can sound very advarage or bad. What measurement are we missing that would explain this ?

[@kyron42]

I am sure Amir will correct me if I'm wrong but if two speakers have a very similar frequency response on axis and off axis and have similar dispersion characteristics and have similar distortion characteristics and similar Impulse characteristics and have similar placement in the same room they should sound very similar. Do you have an example where two speaker sound different when they shouldn't.

[@I_am-an-alien]

@@kyron42 30+ years of loudspeaker design, yes, all the time. A great example is using better quality passive components, sometimes the results are huge, no measurement difference. I also think that cone material plays a very large part, I do not know how one would measure the differences, especially at the system level.

[@I_am-an-alien]

@@kyron42 forgot to mention, series verses parallel crossovers, I have made identical transfer functions yet the sound stage presentation is very different, yes, the amp sees a different input impedance but when measured, no difference, what are we missing?

[@kyron42]

@@I_am-an-alien I always use air core inductors. I've never AB high quality capacitors vs low quality.

[@kyron42]

@@I_am-an-alien I have no idea what affects soundstage. I suspect that the better matched left and right channel are the better soundstage you get.

[@JosephCrowesDIYSpeakerBuilding]

I would like to understand why sometimes low harmonic distortion does not always correlate to better sound. There are some outstandingly good speakers that actually have quite high H2 and H3 (around -45dB @ 90dB SPL). This needs to be investigated more. Purifi mentions the difference between Km(x) and BL(x) induced H2 and how they subjectively differ. Perhaps sprinkling a little of the “good” H2 into the recipe makes for a great sound.

[@kyron42]

What type of window do you prefer for FFT?

[@AudioScienceReview]

On Audio Precision I use Equip-ripple which is proprietary to them. Sometimes I use flat top if I am interested in exact amplitude but that is rare.

[@peter3728]

great stuff! sorry this may be a newbie question but what is the state of the art for in room stereo measurements from the listening position? Can these systems capture frequency response in high resolution along with very accurate time arrival/domain for specified frequencies.? could such a system measure music in real time to compare gear/wire etc in frequency response and time arrival?

[@FOH3663]

There's several... these days we're fortunate, it's easy to capture near state of the art acoustic measurements with little effort or expense. Most any measurement mic, software and device is fine. Even modest $100 mics capture what we need. REW (Room EQ Wizard) is state of the art free software. Simple all in one systems like OmniMic are great, so very simple... around $300. I have/use both of the above. Smaart is the measuring system often used in live pro audio.

[@Texacate]

I was wondering if the wave-transmission properties of air changes significantly with frequency or amplitude (over the audio band of course)? I don't know that it does, but IF it did then air itself will introduce "distortions" between your speakers and your ears, no matter how good the speaker is... Just a thought...

[@AudioScienceReview]

It is a significant factor for measuring large speakers outdoors. Changes in humidity and temperature cause phase shifts that corrupt phase measurements. Fortunately the near-field measurement system I use solves that problem. But it does plague traditional measurement schemes. The impact on our ear though is not significant although having tone controls is always useful and mandatory.

[@wedangstudio6354]

thank you

[@Luke-qs2cg]

This is all part of standard harman speaker philosophy. Considering how many people today take their understanding of speakers from their work, I would have expected more people to have understood this.

[@davidlong1786]

You sure have more faith in humanity than I do after having read so many forums over the years. 🤣🤣🤣

[@nicoras8803]

@@davidlong1786 A lot of this came from Philips in Eindhoven long ago but probably only few millennials seen their handbooks on speaker development and measurement. I have been fortunate to see their anechoic and measurement facilities in the mid seventies. I saw the first active (I think the first) speaker development there called Servo Sound and they used the facility to develop an analogue actively corrected ASP (as opposed to DSP :)) small loudspeaker system that would probably compete with any current active system.

[@cbts0029]

interresting, it shows how accurate the hearingtests are, not to hear the distortion between 2k and 10k

[@hoobsgroove]

down to earth very incisive 👍

[@jeankazamer9166]

i so wanna watch it right now. keeping this for bath time tonight haha thanks again for educational content!! much appreciated 👍😍

[@andrewwebb4635]

Thank you for a top video. I fully understand about the distortion and I half understand about frequency response. Both yourself and G R Research place flat frequency response as the Holy Grail. But is it really? We’re talking about human hearing. Is flat response that important and does a little variation of up a couple of dB or down a couple of dB here and there really matter to us humans?

[@AudioScienceReview]

It depends on how wide the variations are. If they span a large region, even 0.5 dB makes a difference per research by Dr. Floyd Toole and Olive. If it is a small region, yes, you can ignore it.

[@nicksundby]

Keep exposing those charlatans and hucksters lol

[@les5309]

Congrats Amir for an excellent presentation. I did find two other spelling errors, though. The word "tedius" should be "tedious" and the word "psuedo" should be "pseudo". Keep up the great work, nonetheless...lol.

[@kyron42]

The graph is very difficult to see on the phone. It's a pity you can't make it larger.

[@hi-techfilmmaker5682]

get on a computer

[@kyron42]

@@hi-techfilmmaker5682 I've got a computer but it's too big and heavy to drag all over the house.

[@hi-techfilmmaker5682]

@@kyron42 So just walk over to it or get rid of it by selling it.

[@kyron42]

@@hi-techfilmmaker5682 that's very inefficient. You can't be highly productive if you have inefficient processes.

[@kyron42]

@@hi-techfilmmaker5682 how many films do you make every year?

[@jdavis417]

The LGK is pretty. If you painted it Hot-Rod Red, it would test better. Logics, see?😄

[@sonatturkoglu33]

Hi Amir :) can you test wireworld Powercords ? if posible for you. İ am living in Turkey if we close i can send you easly but you are so far..

[@AudioScienceReview]

Sure I will be on the look out for them.

[@anaxa4883]

This is ridiculous! We need less objective data and and independent review. Trust manufacturers. They want to help you!

[@AudioScienceReview]

:)

[@thomashoffmann9646]

As a driver manufacturing company I know about the response bullshit.

[@musicxxa6678]

More headphone measurements pls

[@AudioScienceReview]

You mean in video? In text I recently measured the Mark Levinson 5909: www.audiosciencereview.com/forum/index.php?threads/mark-levinson-no-5909-headphone-review.35292/

[@hyper0505]

@@AudioScienceReview hello, i have a question, is 1.1 output impedance of a DAC could colour the sound of a music ??? I'm planning to buy the Hidizs S8 DAC but the output impedance is a little bit bigger than Apple Dongle like 0.9 ohm vs 1.1 ohm (based from your measurement data) . Is there any big differencr between both of them? Thank you 🙏🏻

[@AudioScienceReview]

@@hyper0505 If it is really 1.1 ohm, then no, that is very low and as close to zero. It also won't impact planar magnetic headphones that have constant impedance.

[@hyper0505]

@@AudioScienceReview ah okay, thanks for the explanation 🙏🏻🙏🏻

[@nicoras8803]

@@AudioScienceReview I don't think anything has a constant impedance over frequency, that is why the call it impedance, it is complex. The problem in audio is that everyone tries to simplify stuff that is actually not simple. If you have an impedance match maximum signal transfer takes place at minimum distortion. You will always have a rising impedance at resonance. Audio designers for some reason always design input circuitry of high impedance so it is easier to ignore the necessity of impedance matching.

[@nonchalantd]

♥

[@paulpaulzadeh6172]

interesting comparation Amir , or irony 20K $ with 300$ DIY speaker , why not measure some high end speaker , and compare it .

[@AudioScienceReview]

That comparison had a specific purpose. The company behind the $300 speaker said that is basically room noise. So I just grabbed another speaker which had far less distortion to show that was not the case.

[@iamsometimes6712]

r/woooooooosh

[@thomashoffmann9646]

All this AP bullshit was made in a race of measurement companies. They are able to analyze something a human can not notice. In my opinion an old NEUTRIK AUDIOGRAPH is enough in terms of freq.response & distortion.

[@ClassifiedBrief]

So you can hear 2.5% thd but can't between caps & cables? Lol your so full of bias it's hilarious

[@davidlong1786]

Have you ever tested caps and cables to see just what the THD is or are you claiming calibrated ears? 🤣 Show evidence instead of "say -so".

[@ClassifiedBrief]

@@davidlong1786 I could care less. I use my ears. To think thd matters but not caps or cables is just a silly thought

[@AudioScienceReview]

I can easily hear the difference between cables. I have reported this in a number of reviews. The problem is, like you, I can only do that when I know I am changing cables. Remove that knowledge and the difference vanishes. So I suggest you trust your ears and ears only. If you do, then you will see that there is no audible difference.

[@ClassifiedBrief]

@@AudioScienceReview not true because I have sat down on my system I know very well, full gr research nx otica dual triple servo subs, and I have recognized it doesn't sound right when I never changed anything! I then find out I forgot to change some minor up sampling setting or I had a cheap cable plugged in I forgot about. I was trying to enjoy music but my EARS told me something wasn't right when I didn't even realize it wasn't the right gear or settings hooked up. This has happened to me multiple times over the years. Maybe your ears really aren't that good?

[@davidlong1786]

@@ClassifiedBrief It's "couldn't " care less. Without doing a DBT on caps or cables or others components it's just hearsay with zero proof. I'm sure you can fool yourself daily by thinking you hear a difference but then again you waste money on things that don't make a difference so your monetary investment is clouding your judgement also.

[@johnwet6969]

You are a miracle Amir! Thank you very much for all what you’re doing for us! Especially in these marketing/religion times.