john banks

It was a Dynamat substitue (being the cheapskate that I am) but seems to work well. Given my general DIY lack of ability I decided not to approach the dear shiny Scooby with a spray - I would probably miss and hit the steering wheel or something! I was amazed I didn't **** anything up during this install (reminds me of school when I tried to paint - would make a line with a brush and then decide it wasn't right and go over it again and again until it looked really bad!)

I am surprised with a quoted 50W that it is not so loud. Mine is loud enough to not hear anything else except the music right to the red line in 3rd gear (quite noisy then!)

I don't know what your level of understanding is about active crossovers, but mine is mainly from the aforementioned Car Stereo Cookbook from

ScoobyDoo555

John,
Agreed - 0dB is the threshold of hearing.
3dB is the LEAST amount the human ear can detect in difference (from one level to another)
Anybody who tells you different is bull-****ting you. Ask ANY sound engineer. :-)

This is the point I'm trying to make - with all the extraneous noise inside and outside the car, it's gonna be near impossible to tell the difference. Audiophiles will only be able to tell in controlled environments (acoustically treated rooms - studio control rooms etc). Cars are slightly different ;-)

Dan

john banks

Sorry, don't buy that. The gold standard reference here is an audiogram. When you perform an audiogram on a person, 3dB is EASILY detected - the machine I used allowed 1dB changes and even people with hearing loss could tell - the audiograms were mapped to the nearest dB. Granted these are pure tone and in a soundproofed room with headphones and not in a car, but are you really saying that doubling the power through a speaker is the least that can be detected? On my amp changing sensitivity from 0.4V to 0.5V is detectable. And briding it (+4 to 5dB) is barn door obvious to anyone. So experience tells you me that perhaps not all sound engineers would agree with your statement. Or maybe I'm just being argumentative But that's the way I learn.

[This message has been edited by john banks (edited 19 November 2000).]

ScoobyDoo555

Sorry John, I'm not going to get into an arguement about this coz it's petty :-)

But as a lecturer is Sound Engineering and 10 years experience as a sound engineer and producer, I teach this subject to Degree students.

There are different interpretations of sound levels, depending on whether it's analogue or digital audio. With all due respect, I think you may be confusing the two.

It is fact that the least SPL (sound pressure level)difference the human ear can detect is 3dB.

Rather than waste valuable BBS time arguing this fact, please email me off list if you'd like a copy of the paperwork that proves this.

Respectfully,

Dan

ScoobyDoo555

Further to my previous post - are you telling me that at 0db, if you add 3db, you'll hear the difference?

Furthering that, 3db to 6db?

I don't think so - unless your a robot or an audiophile ;-)

Dan

PS let's keep this lighthearted :-)

john banks

Edited above post to make it less confrontational

But I would be interested in any info you have as it does not square with experience. Whilst I accept you are obviously very skilled, the gold standard with a claim to human perception can also be answered by someone with a medical degree My experience at least just does not square up with what you are saying and the difference that can be perceived by a human ear is not something that can be debated other than in the context of empirical rather than theoretical data.

john banks

We've been posting over each other! Lighthearted is good, and I really want to learn and I don't think Webbie will mind the bandwidth.

At the threshold of hearing (which you are testing during an audiogram) a difference of 1dB can usually be perceived by the listener, so YES I do think you could tell a change from 0 to 3dB or 3 to 6dB definitely. I have seen it happen with my own eyes. In practice, especially with older equipment and to speed up the recording, it is usually recorded to nearest 5dB as that is where the gridlines are marked on the recording sheet! (It's the same with blood pressures - people have a strong terminal digit preference of 5 or 0). So it cannot be "FACT" that the human ear cannot perceive less than 3dB. At best it is an empirical assertion which is disproved with only one contrary example. I think you underestimate the finesse of the human ear if you insist it cannot perceive less than a doubling in pressure.

A thought: could it be that 1dB can be detected during an audiogram because it is such a pure setup with only about 10mm from source to eardrum and virtually no extraneous noise?

Why is digital or analogue going to make any difference since it is all analogue when you hear it? Or are you talking about the encoding of the source and bringing signal:noise into it?

ScoobyDoo555

:-)
again, keeping this light hearted ;-) the 3dB difference can apply at any level, however, usually under normal listening conditons (85dB - average HiFi levels), please increase or decrease the level by 3dB.

"Most" people can't hear the difference.

As soon as I get back to work, I will gladly source the paperwork to back up by claim, but please, try it yourself. Honestly, I certainly can't hear a 3dB level change (and I'm use to working on £20K of monitors and 0.5M worth of studio :-D)

Besides, given the choice, I'd rather hear turbo and boxer engine heh heh!!!!

Scooby Doc

Yeah guys!

But how are my perfect 10s going to sound shut away in that tin box of a boot?

Keep up the good humoured banter. We're listenting and learning.

John, definitely meet up at some point.

Martin

[This message has been edited by Scooby Doc (edited 19 November 2000).]

john banks

Exciting on line test

ScoobyDoo555

Have to give that site a try :-)
Of course, test tones are different to music though ;-).......

Soz ScoobyDoc!!!

In answer to your question, I'd imagine pretty good!!! Have you sorted it out yet? If so, it'd be nice to hear 'em at some stage....bit difficult being up North :-)

I get my system tomorrow (woo hoo!!!)
You'll probably hear the swearing from grazing my knuckles all over the UK!!

I'll try and scream at different levels eh? ;-)

Dan

john banks

LOL!

What system are you getting ScoobyDoo555?

BTW this post is turning into a chat server - I have just edited my last post to make the link work and make it even cheekier!!!

I expect the volume of screams will be inversely proportional to the 10^wire guage you try to get through that bloody aircon grommet!

LOL @ myself now. What a sad git. Enjoy

ScoobyDoo555

you ain't far from the truth with the cable!!!!

I'll let you know tomorrow when I get it....


Cheers

Dan

Scooby Doc

Dan

Is this your sub and amp combo.

What you buying, can't wait till tomorrow

Martin

Scooby Doc

John

You trying to get your 100th post tonight?

Martin

john banks

No, I've moved to chat - never tried it until now.

However, the wife is studying hard for her first MBA exam so I have been repairing gutters and generally tinkering all day hence the prolific posting!

Edited to say that I've just noted that you can create a new room - we could have an ICE room and ScoobyDoo555 could beat me up

chat.scoobynet.co.uk (they kept that quiet!)

BTW, just tinkering with my lounge amp and it has settings to adjust the rear speaker levels with a test tone. The unit is 1db with range -10 to +10dB. You can easily appreciate a +1dB increase in the white noise, but with actual music it is a bit trickier. Maybe this is where the 3dB comes in for actual real music.

[This message has been edited by john banks (edited 19 November 2000).]

Scooby Doc

John

Your wife is clearly working hard to keep you in the motoring style to which you have become accustomed!

I'm on and just got a receiving call.

Just when bedtime was approaching

Martin

Scooby Doc

John

Hmm just replied to your post but it disappeared -oops

What I said was - your wife is clearly working hard to keep you in the motoring style to which you have become accustomed.

Maybe we could have you and Dan on a live video link.

Martin

Scooby Doc

Oh it did reappear.

At least I was consistent.

ScoobyDoo555

Just been reading last night's postings!! LOL!!

I might look rather 'solid' but I hate violence!! (well, administering it anyways!!)

As u can tell it's 7.57am - haven't gone to the shop yet, but am looking at JBL components for the front, maybe backs (from what I've heard it's pointless anyway....not theory - rumour on here!!!!LOL!!)
4 ch amp (prob JBL) maybe 2ch(fronts only)
Pioneer 12" Sub (one with the metal cone)
2 ch amp for Sub.....

This place does amp install kits (all the wiring) for q. cheap

That's all folks - I'll let u know how I get on

Dan

ScoobyDoo555

One thing of interest - John, I saw your post re: the difference between Analogue and digital levels.

In terms of metering, with regards to Digital audio, 0dB is the loudest the audio can get. Anything over this will result in instant distortion (not nice analogue stuff, but horrible 'salt on a slug's back' digital distortion - bordering on white noise)

Analogue 0dB is totally different. This is the optimal recording and monitoring level. Normally you can increase this record level to +6dB, but this is only hindered by the quality of tape (i.e Normal, Cr02, Metal etc)
On professional recorders you can 'over-bias' the machine to record at between +12 & +18dB!!!!! (3m's 996 tape - not made anymore, but Ampex's 499 is pretty close)

Of course, with this, you can 'cook' the tape to get the better signal to noise ratio.

With digi, you've got to get it as close to 0dB as poss, if not, putting it simply, most digi machines (CDs, DAT, Minidisc etc) work on the principle of bits (eg, 16bit or 32 bit).
The metering represents this, so the lower you record your audio, the less bits you use, therefore, the less the quality of the sound.....as you mentioned, this also brings into play the signal to noise ratio....

Hopefully you can see where I was coming from :-)

Dan

chiark

Guys,

Excellent stuff - most interesting and good to see a debate on here!

The idea of a meet appeals. What do you think? Where are most people based?

Bandwidth, I have been assured, is no longer a problem with Scoobynet at all. Webby's swimming in it, apparently...

Cheers!

john banks

ScoobyDoo555, yeah I always wondered why with a TDK MA90 you could kick *** with the recording level (+6dB), and I suppose distortion would set in gradually. Can see what you're saying about digi cording as it's a brick wall when you're at level 65535 on a CD recording (and would then sound like my crappy ondigital box does every minute or so). Must be a tricky job to stop the really hard hits touching the top without having a really low gain - do you allow any at all in most CD recordings? Or do you do a bit of subtle compression? I suppose even though s:n would go down by putting the level lower it would not matter with digital as there would be no noise, but you would start to increase quantisation error?

You'll laugh at this, but when I was 14 I took an old 8 bit sound sampling cartridge from an old Atari and "wired" it to the parallel port on my Amiga. I didn't get enough pocket money to buy connectors and soldering iron (sob sob look at me now!) so I nabbed a load of dressmaking pins from mother's sewing case. Wrap some wire round the end and in they go to the parallel port :O As I remember there were 11 - 8 bits signal, 5V, 0V, and strobe. Then used selotape to attach the wires to the edge connector on the sampler. It then worked as a rather nifty sound sampler or data acquisition tool to attach to my lego(!!!) My mother was bemused and said, "I hope you don't break that nice new computer of yours" (which I had been saving for for 3 YEARS!). No wonder I didn't get out much and liked maths and physics. What I learnt from this is that if (when) one or more of the wires comes out you get some lovely digital distortion which is the most exquisitely annoying noise on the planet. I wondered if I could use my soundblaster compatible through a resistor network to detect clipping on my amp to set the levels, but it's a long distance for cable and I run it on max gain anyway. When the volume goes really high it is difficult to detect frank distortion, but it just starts to sound less pleasant. I don't know if this is ear limited or amp/speaker limited hence the thought about checking clipping.

I sometimes wish I'd gone and done a technical career but I would probably have blown a few things up by now, so all they let me do is be a Doctor!

Meet would be great - I'm in Fife though. And I'm a crap driver and my stereo will not sound a patch on your lots. But I'd enjoy it anyway!

PS How's the install going? Did you get the JBL components? GT6.0c or other? What do you think?

[This message has been edited by john banks (edited 20 November 2000).]

john banks

Replying to my own posts again (slightly nearer to the original topic):

I am thinking of removing the factory rear speakers that are currently supplied off the headunit. If I disconnect the rears and put the seats down, the imaging and bass seem to improve.

Might try it sometime...

Alternatively, I am still tempted to LPF some 6x9s for my rear shelf to reinforce my midbass and help the fronts a bit. I'm thinking a passive 6dB/oct job at about 150Hz - what do you guys think?

Certainly with the HPF for fronts at 80Hz and LPF for sub at 80Hz it sounds as though the bass is coming from the front. Not the case if HPF at 90Hz or 100Hz (can hear the sub distinctly). However, the system doesn't tolerate really high volumes with the HPF set lower, hence my thought about midbass reinforcement.

I could put the 6x9 in parallel with the fronts and run the amp a 2 ohm. Then I would have to think about the levels - I suppose I could use a resistor network of some kind (e.g one series, one parallel with the speaker) or set up some kind of potential divider. Wouldn't want to sap too much power though. Or what about running the rears mono to avoid dragging the image back?

Anyone done this or anything like it? What do you think 6x9s in mono with a LPF and a small level drop sound like?

ScoobyDoo555

Install was going great.....
Called up the Subaru dealer to confirm speaker sizes (6"fronts 5.25" rears)... got by brand new JBL GTOs home, prised open the rears....they were 6".Bugger.
Not to disheartened, I thought "I'll wait to pick the wife up and pop back top the shop - in the meantime I'll put the Kenwoods in the front" After playing a battle of wills with the door trim (I'd be ****e at the Crystal Maze!!), installed them.
Wow.
Absolutely fuggin' magic :-)))))))
I thought, "can't wait to hear the JBLs too"

Attempted to install the JBLs in the rear - wouldn't fit - too high!!!

Had to go back through the process of uninstalling the Kennys (I'd soldered them on - proper Oxygen free cable etc..)

Meanwhile it's getting dark. And cold. My mood has somewhat deteriorated, as has my excitement for the project.

I look at the amp and wiring kit, and think "Sod it- it can wait till the weekend"

As a result, I was in a hurry (I commute over 60 miles - spend the week at my parents) to leave, and yes, all my bass has disappeared in a "swishy/wispy" annoying phase...... Guess who's sorting out phase problems at the weekend, as I now have an ICE install that sounds better silent :-(

Regards the Sub, I've bought an Eminence 12" and JBL LCA752 2ch amp.
The problem is that "Santa's got to wrap it"

Still, on the bright side, on Christmas day, after dinner, don't have to waste, oops I mean spend time with the In-Laws!!

chiark

John, I was obviously rich as a kid as I splashed out on the trilogic sampler at 25 quid for my A500.. It was the first one that was less than 100 quid, IIRC... Wonderful bit of kit, kids of today don't know they're born, command line prompts, understanding what every file in the OS does, $dff180, copper, bitblt, D0-D7,A1-A7,...

Back to the sound relevance, I'd try not to run your rears in parallel at 2ohm, as it will increase the distortion and possibly drag the soundstage back. How about an l-pad to balance the signals?

If you ever bought a tabby for your Amiga, or bought anything from First Computer Centre, I was involved. I wrote the drivers for the Tabby, and worked at First whilst I was a student. I also wrote for CU Amiga and Amiga Computing... Them were the days...

Richard Gledhill

Man I loved my Amy too... A500, then A4000/030... I had the Mastersound - remember "Is it real, or is it Mastersound?" Brilliant 8-bit sampler, had loads of fun. And.. the A4000 still sits downstairs, wired up to about £5k worth of widescreen telly and surround set-up, to play Speedball2, Sensible Golf + Soccer, etc!! My brother's got the Tabby btw, and we remember First Computer Centre (Leeds?) well! Aahhh... them's were the days...

Anyway. I go away for a couple of days and find dozens of posts in my absence! How am I supposed to contribute to these debates if you have them when I'm not around?

Great stuff guys. Firstly, here's a cat for the pigeons... 0dB is only <B>relative</B>. So saying "0dB is the threshold of human hearing" is actually the <B>definition</B> of 0dB in the real world (analogue domain). 0dB in the digital domain (CDs etc) actually refers to 2^16 -1 (16-bit recording). 0dB as applied to speakers is, in a way, meaningless, unless you're referring it to a fixed reference point, such as 1W/m.

Ok, next. The 3dB doubling thing.

1B = 1 Bel = log (P_chng)

where P_chng = change in power.

Therefore,

1dB = 1 deciBel = 10 log (P_inc)

and so going from 1W to 10W of power = 10x increase, and so:

dB = 10 log (10) = 10dB

So 10dB increase is the same as 10x the power output from the speaker (we'll come back to the amp side in a moment!! )

Similarly, for double the power from the speaker:

dB = 10 log (2) = 3.0103dB (roughly )

Righto, got that sorted. Next thing is the amp power. For a perfectly efficient amplifier, the best it can manage is to get the same power output from the speaker as it dissapates internally. Most amps are 50-75% efficient, and will work best at a particular impedance - normally 4ohm. At other impedances, the efficiency will vary, and your actual power output will therefore vary too. [Interestingly, this proves that some amps cannot possibly provide the ratings they claim, as their fuses would blow at double what they claim ]


Anyway, hope it sounds good when you've got the phasing sorted out! Stick with it - it takes a lot of time and effort but the joy of hearing new bits in music you thought you knew is worth every penny.

Richard


Chiark - we could almost write a tech faq from this!

ScoobyDoo555

Yeh Richard - where were you??? ;-)

I found the same info today from a working colleague (Dr Richard Lowe @ Hereford Tech).......
John's right. So am I. As is Richard! I think we're all on the same lines, generally however, "coz I is a sound engineer - I be talkin' in a different labguage" (Hereford accent BTW)

The wife called me up tonight and said, "Guess what I'm holding right now?" (oo, er)
My sub & amp.

Life's sooooooo cruel.

Dan

Scooby Doc

Nick

A meet sounds good. Trouble is John and I are north of the border. You guys are very welcome to pop up for a wee taste of our winding roads.

However the distance may make this a little impractical. A suggestion - anybody interested in meeting up on neutral ground - say Le Mans in June next year?

Martin

chiark

Coming north of the border appeals to me, as long as it's not John o'groats. Inverness was the furthest north I got last time, which wasn't too bad...

Tech faq: not a bad idea! I'm playing with the faq at the moment, as you've probably noticed, to make it data driven. Should finish something today.

Someone who had a tabby! **pride**

Cheers!