Calling Trevor - stereo advise please

[Ron Mummert]

The following statement is NOT intended to be offensive to any of the participants in this discussion of sound waves far beyond my comprehension. However, just as in any debate about hairsplitting differences regarding the merits many products, how much is simply mental masterbation? Do we too often do battle over minute differences in the SOURCE of satisfaction, be it sound, a painting, or (my favorite), wine; rather than accepting that the RECEPTORS - eyes, noses, & ears, provide the real difference? The variations are infinate.
Some folks love liverwurst, some folks would gag on it. Is it the liverwurst or the tastebuds?

Granted, this is a comment from someone still happy with 20 year old Koss headphones, "dogs playing poker" & a legendary taste for blended wines - (mix a little Chardonney with Grenache).

Your tastes may vary - Ron.

Originally posted by Trevor
[B]Porter, am I to assume that is your true name ?

Yes, my name is Jason Porter. Nice to meet you.

It was not my intention to offend you personally and I apologize and regret that you have become upset. My gripe is with manufacturers who make statements which have no scientific foundation and are simply not true.

I also have the same gripe.

However you have inferred expert knowledge as a result of your occupation and others could accept the information you have posted as gospel and this would indeed be unfortunate.

I have posted nothing as gospel. I simply made a short list of the midgrade audio cables that I was installing in my car. That is in no way a recommendation or a solicitation, and to view it as such is rather odd since this is a car forum and not an audio forum.

It would appear that you are basing your learning on advertising and manufacturers spin and this is the very point I was making.

That is an incorrect assumption. I am a great skeptic when it comes to cabling and the relative merits thereof.

It is quite impossible for any form of straight conductor, stranded, gold plated or whatever, to in any way alter an audio signal other than attenuate it. It is not hard to put a spin on words using technical jargon and suggest all manner of alleged magic but scientific facts are required not here say.

You are correct. ALL cables attenuate signal in one way or another. The LACK of attenuation is the measure of the performance of a cable. One can certainly compare them in light of that fact, and the obvious "coloration" of sound between one pair of interconnects or speaker cables and another makes that brutally clear. More than 6 dB of sound output difference across multiple frequency ranges as measured with an RTA also makes that difference quite clear. Different cables do make a very clear difference in sound, whether they are interconnects or speaker cables. The days of "lamp cord" are long over and we have an entire research industry now dedicated to the pursuit of perfect signal transfer.

Now I again apologize as I now realise that you are referring to shielded audio interconnecting leads rather speaker connectors in respect of braid. Shielding is essential in order to prevent what one could describe as induced noise. But provided a shielded audio cable is electrically correct it can not be improved on and high price can often be directly related to the cost of advertising. However no doubt shine and colour as well as high cost does provide a conversation piece.

We are talking about car audio, which is a far different environment from home audio, and filled with a myriad of noise producing devices. My expertise lies primarily in audio systems for the home, and many of the same principles apply, but the vastly increased noise floor in the auto environment calls for a different set of paradigms (pun intended!). Noise rejection/reduction is of paramount importance in a car interconnect as it is the weakest link in terms of both direct capacitive induction and toroidal impedance. Braiding, twisting, and extensive shielding all combine to reduce the transmission of chassis electrical noise into and through the cable. If you choose to deny the value of twist and braid in reducing the S/N ratio, go talk to the phone company or any telcom engineer about twist rate and braiding in phone and data cable and how it affects signal integrity in the real world.

Please do not raise the issue of gold plating and the alleged advantages in respect of audio gear. A business I owned manufactured equipment dependent on electrical contacts so that I am aware of the proper application of precious metals. This exotic has been a winner for the spin doctors to trade on.

Who said anything about gold plating? Gold is one of the poorest conductors for audio use. Silver and copper are both much better conductors, as is platinum. Gold is valuable for only one reason... its resistance to oxidation and corrosion. Gold tipped interconnects will tend to preserve signal junction more effectively over time, especially when two different types of metals are making contact, and even more especially in an environment where they are exposed changes in humidity and temperature on a regular basis.

I understand that you have your little pet peeves on these issues, but please don't bring them to me or use any statement of mine as an example in your soapbox rhetoric. You're barking up the wrong tree.

I note that you are installing infinite baffle subs in the rear deck. This would provide the ultimate set up for base reproduction and I would appreciate your advice as to how you are achieving this baffle arrangement. N. B. this is a genuine request and should not be taken as sarcasm. My home speakers are set up so as to provide virtual infinite baffle operation..

That is correct. I can't stand the sound of a sealed or ported box subwoofer, they all seem like one-note wonders to me. I chose to go with the infinite baffle arrangement as an experiment to see if I could disprove some of the commonly held opinions in the car audio community in my area... Since I am concerned only with sound quality and not with absolute output, it seemed like the best option. It certainly will give me a wider sonic palette and deliver a more accurate and pleasing experience.

As for the specifics... we are bonding 1/2in MDF to the bottom of the existing rear deck, enlarging the speaker openings to give good airflow, and mounting two 10" infinite baffle subs in more or less the stock 6x9 locations. The subs in question are both 8 ohm and designed specifically for this application, and will be driven at 4 ohms off a 250x1 regulated mono channel. Damping factor on that amp is in excess of 500 so it should deliver an acceptable level of control over the drivers.

The trunk will be damped with thin sound deadening insulation (Dynamat if you're curious), and the rear seat passthrough will be sealed off with a rubber grommeted MDF plate. The whole object is to prevent the back wave from interacting with the front wave, as the gross volumetric distances in the trunk are fixed and can't be easily tuned.

I note that you have a background in music, a trained ear and your requirements indicate that you are able to hear close to 25 kc which is quite remarkable. Unfortunately I can no longer hear much above 3 kc due to shooting a short barrel rifle in my younger days and playing piano is becoming difficult so that I have resorted to a Technics digital piano. At present I am involved in developing a hearing enhancement unit for use by people in the same boat who have trouble understanding the dialogue in TV programs and home theatre multi speaker systems.

Yes, I'm very lucky to be able to hear clearly up to about 19,000hz. Above the 20hz mark of course the perceived sound disappears but spatial effect is still there. The human brain responds to sound up to around 30,000hz, this is where we derive spatial acoustics and it is the science on which psychoacoustics is built.

For example... in a completely dark room, walk up to a wall. Even if you are making no sound and the room is carpeted, you can "hear" the location of the wall... that is high frequency spatial acoustics.

In reproduced sound that frequency range delivers the sensation of space in the recording environment, especially in a live recording that is properly mastered. CD audio attenuates above 22,500hz, while SACD and DVD Audio extend well above that into the 30k and 40k realm, and up in the case of SACD.

Your work in hearing enhancement must be very rewarding... it is a beautiful thing to see someone hear something again that they thought was lost to them... it is a great gift. Best of luck to you.

You must accept that inaccurate information should be challenged for the good of all and can result in interesting debate. The intent is not to teach a lesson. Have you had a look at the great site covering car audio posted by Lee ? All the answers are there in respect of analyzing manfrs. claims.

Yes, I've seen that site before. It has some great info.

This " lordly statesman from down under " tries very hard in view of his age not to post in a patronizing manner but it appears that I have not succeeded.

Well, no you didn't. But I forgive you! If I'm ever in NZ we'll have to meet for drinks... and of course you're always welcome here!


-J. Porter

[sfsvx]

Originally posted by Porter

The days of "lamp cord" are long over . . .

-J. Porter

They are? Dang!!!!!

Should I replace it with some of that #8 fencing wire?

Originally posted by Dick Young


They are? Dang!!!!!

Should I replace it with some of that #8 fencing wire?

Nope, you missed that fad also. Now they're saying to just use bare wires, but you can twist em together for neatness.

CJ

[wawazat??]

Originally posted by cjoffe


Nope, you missed that fad also. Now they're saying to just use bare wires, but you can twist em together for neatness.

CJ

Very Ron-Mummertian post of you there CJ! You should be proud of yourself!

Todd

[Ron Mummert]

Originally posted by cjoffe


Nope, you missed that fad also. Now they're saying to just use bare wires, but you can twist em together for neatness.

CJ

I'm hoping we can work duct tape into this discussion, as well.

Ron (Tacky-R-Us).

Duct tape IS manna from heaven!

Originally posted by cjoffe
Dahlquists Suck!

They didn't used to, when they used "MAGNAT" drivers.


Randy (Defending the used ta be's) ii

[Trevor]

Ron you are a wise man to sit back and enjoy the music as was my earlier advice.

Having been in this argument before which always falls back on perceived performance. I should have stayed well clear as I will do from now on. It is a bit like debating the taste of wine but gets more intense. The use of complicated language is however much the same. You know the one about old fools and I am one.

Jason, you have some Ca$h in you and I like you both. You both will mature well I am sure and I say this with good will.

I am tempted to quote and dissect your reply as you have done mine relying purely on scientifically proven fact. But as I do agree with you in regard to many points you make and I respect and admire your enthusiasm I will not do so. I do not accept the tone of sarcasm which remains.

At this point I make a note for other readers i.e. this type of argument does not normally result in violence and you will note that we could someday meet for drinks and are meantime having fun.

Jason I will stand alongside you and shout with you in respect of the defects relating ported enclosures.

It is impossible to produce an infinite baffle as the animal does not exist but on a practical basis one can get close to it. However from what you describe you are creating what is no more than the largest possible enclosure which I agree is the very best approach in view of the mechanical limitations involved but as you confirm you are still involved with a Ò tuned Ò enclosure.

Consider the possibility of an unrestricted vent to outside the car. In effect the car becomes a very large enclosure and you are within it. The effects are the same with regard to sound wave separation but reversed. I have done this and be sure your local audio community will sit up and take notice. You will have to provide an opening in the trunk floor which can be in the form of a louvered panel. However you can first experiment by leaving the lid ajar and no pain in this.

I will now leave you to your psychacoustics as the supreme authority on audio here on the net, free to answer all future queries without decent.

P.S. N.B. Ron wins on the basis of IQ.

-T. R. Sheffield

Originally posted by svxeno


They didn't used to, when they used "MAGNAT" drivers.


Randy (Defending the used ta be's) ii

Actually I was just tweaking. I know nothing of current Dahlquists, but only their stellar reputation. I currently have Maggies and aspire to Martin-Logans or Soundlabs someday.

CJ

[lee]

Originally posted by Porter
Duct tape IS manna from heaven!

On National Public Radio (NPR) news the other day they had a story about a medical journal article wherein it was asserted that duct tape did a better job of wart removal that the chemical normally applied, and had even better long term results than a doctor freezing the little buggers off.

just cut a little patch and put it on for a week and presto, duct tape has done it again.

Some years ago I used to assert all one needed was a BFH to get a job done - and now I have to admit my error in correct thinking - it should have been a BF roll of duct tape.



Thank you all for your suggestions and opinions - it's how I learn.

[Ron Mummert]

P.S. N.B. Ron wins on the basis of IQ.

-T. R. Sheffield [/B][/QUOTE]



Trevor, my dear friend; do not confuse IQ with laziness.
All of you possess far more talent with the technical aspects of audio, & many other subjects than I. If it weren't for folks like you, even my ancient Koss headset wouldn't exist.
Thanks to the ants.

Ron - the grasshopper.

My Dahlquists have MAGNATs... they're DQM-909s.



Trevor... your points are well taken and duly noted. Certainly you are correct in your points, though you look at things in a rather unusual way, at least from an American point of view.

I understand why you feel that I have some qualities in common with Ca$h... we both refuse to allow ourselves to be steamrolled by the status quo, and we take it as a personal affront when we are mocked in a public forum in tones of condescension. Beyond that I'm not sure where the similarities lie.

The problem on the audio issue is something like that of the philosopher talking to the astrophysicist... the philosopher thinks of the Earth orbiting around the sun and rotating in its orbit and all other space being "outside", while the astrophysicist thinks of Sol and several associated rocks (with atmospheres) that vibrate around it erratically on its long course into deep space.

I think in practical terms and try to speak in pragmatic language... you think in terms of scientific absolutes and attempt to communicate in the same way.

It doesn't mean either of us are necessarily right, it's simply two vastly different ways of looking at the world.

So, c'est la vie. Let's have a beer and not worry about it.



P.S. - Absolutely right on "infinite baffle" being impossible in a closed space... the two concepts are by definition contradictory... my use of "infinite baffle" refers the COMMON USAGE of the term, which would indicate any sub mounted in a "free-air" fashion, with no specific tuned box enclosure and a motor structure designed for non-pressurized voice coil control. By pure definition, an infinite baffle sub arrangement in the location which I suggest would involve removing the entire back of the car in order to eliminate sonic reflection. This is of course absurd so I assumed incorrectly that you would understand my usage of the term.

I beg of you to please let me hear your system when you're done, Porter. I've never heard of an infinite baffle except as one of those buzzwords talking about home audio stuff when in the end it sounded worse than similar priced tried and true designs. I grew to just ignore it and never payed it any attention in your post until you two started to go at it.

Sure, man! Drop me an email, we need to hang out anyway and have a Sube meet in Greenville sometime in early December.

-Porter

asphaltsurfer@charter.net