john banks

SOUND CHECK 2 Maplin Code KS80B https://catalogue.maplin.co.uk/mainframe.asp

Quoted from Maplin catalogue:

"Sound check has become the international reference standard for sound designers, musicians and producers.Sound Check 2 contains all the original Sound Check tracks for audio assessment, with the addition of some new tracks, which really make sound check 2 the most valuable tool for anyone involved in the audio and music industry. These new tracks include extra dry vocal recordings from the spoken word, rock vocal, soprano and a unique live recording of Luciano Pavarotti. As well as extra tones, sound check 2 contains additional music tracks both classical and rock including "Luv 4 Luv" the ultimate test for bass loudspeaker and their amplifiers. Also incorporated in the sound check 2 analyser are complete instructions for instant frequency response measurement and graph paper for permanent records. The double CD case has a built-in microphone and sound level meter calibrated from -15dB to +12dB to form an instant system response analysis. Sound check 2 - Similar to Sound Check 1 but with 99 tracks instead of the original 92." £29.99

The microphone and sound level meter sound interesting - anyone used anything like this for setting up their system - or do you use your ears?

RTA for cheapskates like me?

Also thought about knocking out a .wav file with a sine & square wave at different frequencies to make my own test disc and try and estimate the volume differences and adjust levels appropriately. Anyone done similar, or have an mp3 of a test disc?

I'm going to do a search on the .wav format and probably knock up a quick QBASIC program to do the job and then burn it onto CDR. It's a few years since I wrote a BASIC program to open a file, write a load of numbers in sequence and then close it. I am assuming the .wav file has a header specifying bit rate and sample frequency - I presume I then just "PUT" the respective numbers for amplitude sequentially to a file and close it when finished - maybe 10secs of each on a different track on the CD. If the peak of each wave at different frequencies is the same then I presume the volume would be the same. Any ideas let me know. I'll post further if this hairbrained scheme works out. My wife will really think I've lost it now!

Edited to say I've found some things on Napster - "1,3 octave" finds 1/3rd octave increments which should do the trick.

Even though I have no equalizer - I can adjust levels of bass/treble, tweeter -3db, bassboost +6dB @45Hz and adjust level of sub and crossover of sub and fronts so it will be useful to get those right.

[This message has been edited by john banks (edited 17 December 2000).]

ScoobyDoo555

Hi John,
I wouldn't expect too much for £29.99!!!

The professional reference / test CDs cost in the region of £350+......

However, putting it into context, it should do the trick to get a 'rough' idea of what's going on inside the car (for bass traps, enhancements etc.)

Let me know how you get on.

Dan

john banks

Made myself a disc with 320kbit/sec MP3s of 20Hz upwards 1/3 octave. Nothing much from the sub until 50Hz and then a lot better from 63Hz up. May assist with some basic adjustments - need longer to play with it.

Might even end up with a sealed sub at some stage which I'm sure will perform a lot better for LF extension, but I'm sure I'll need to get some serious amps and 4AWG cable transplant to get the volume I'm used to! I will do a search on the spare wheel sub boxes folk have built and have a think.

kryten

The Sound Check discs have been around for years and are pretty good, quality wise.

I've not used the 'built in mic' version, but in theory it should work fine, assuming they give you a calibration chart for the mic.

I've used Sheffield Labs 'My Disc' before with a Tandy sound level meter and got OKish results.

I've also used the same meter rigged up to my laptop with various software RTA packages and got some very good results.

Don't know about the MP3 - after all its a 'lossy' compression technique designed for music so it may not work well with sine wave sweeps (or it may work perfectly!)

Don't estimate the relative levels manually and expect to get an accurate result (ball park, maybe). Everyones ears are different, but more importantly, the human ear 'hears' different frequencies at different levels, even if they were the same level originally!

john banks

Thanks Kryten. I think you've hit the nail on the head there about perceiving different frequencies at different volumes - certainly, trying it on a few systems it sounds like the midrange in particularly seems "loud" - I would have thought that the bass above 50Hz would seem loud because of all the air movement, but 1KHz seems much louder. So I need a calibrated mic to do it even slightly objectively then. Interesting to see that although my sub is very loud, 50Hz for example is not reproduced particularly well, and it a LOT lower than I thought it would be (frequency wise I mean). I'm just wondering how low most music goes - I know it will depend on the type, but anyone know the ballpark - what LF extension do I need to reproduce it? I am guessing that 30Hz would be overkill, but decent response down to 40Hz could be quite useful. Would a 10 or 12" sub do this in a sealed box?

One thing I have learnt to be skeptical about is manufacturer's quotes on the bottom end of frequency response - they rarely give you a curve until you buy the product, and they rarely quote how many dB below reference they are at the bottom of their "range". Maybe I'll have to go and read about Theil-Small (sic?) parameters?

[This message has been edited by john banks (edited 18 December 2000).]

kryten

John, the Tandy SPL meter and test disc will help - if you make adjustments: I don't know your system, but amp gains need to be matched from sub to other speakers, phasing being correct etc etc.

As for LF extension, most recorded music will have little below 20Hz, though some classical pieces (1812 overture comes to mind) have around 12Hz (canon!) and I think that the lowest pipes on a full pipe organ are 12-16Hz!! What music do you listen to?

Most people think of 'bass' being the 60-80Hz region because that's what is in a lot of the 'pop' stuff.

An 8" sub in a properly designed box of any type plus an amplifier will be able to hit 20Hz: if you use a 10/12" sub you will be able to get more output, though to do this the box will need to be larger.

The _most_ important thing is that the sub and box are matched, and the box is built of solid wood (normally MDF of at least 3/4") and totally sealed. Throwing a sub into one of the 'pre-made' boxes without matching the T/S parameters is a recipe for awful bass...

For a sub, the speaker's response characteristics need to be considered with the box type as well. You can use a ported box to get a bit of extra output at the low end - though these are very easy to mess up!!

Personally I prefer sealed boxes but you generally need a more powerful amp for the same output as a ported design. The sealed box will normally be smaller, too.

Try:

Adam M

Bachs Toccata uses a pipe organ which goes to below 20Hz, amazing to listen to on a real system, such as an inhouse setup. Agree with kryten entirely except for the suggestion of JL audio subwoofers. Their W6 range are a bit past it now, and many oter outfits these days seemed to have moved on technology wise. (not that there has been a lareg development sub wise in recent years). In my experience of the budget alternative to rtaing, they actually do work very well for the money but really are no substitute for the real thing. I would be v interested to give the rta programs a go on the pc, never heard of those before. I think an expensive mic with a linear response is a must though.

Perhaps rather than buying a cheap rta alternative, you should put the money towards going to see bob hobson and asking him to perform an rta for you. The only downside being that he can only tailor the car to his taste and the final adjustment is entirely subjective and therefore requires your input.

Bob Hobson is the don of car audio, his abilities with an rta are almost unparallelled in the incar field. I believe he may still work for prestige in rayners lane.

kryten

Didn't mean to sound like I was endorsing JL woofers, despite the fact the I like my 12W6 . There are many alternatives - I was trying to make the point that buying an expensive sub and chucking it into 'any old box' will probably sound worse than a cheap sub in a box designed specifically for it.

I just feel that the JL site is very informative on the whole subject of subs.

As for the PC based RTAs there are several factors to accuracy.

The soundcard (most are good enough nowadays) though if you use a PC plugged into the mains the 50Hz reading will be WAY off. A battery powered laptop is a must for sub bass readings.

The Mic: as long as you have a calibration chart, it doesn't matter if the Mic is linear as you can correct for its frequency inaccuracies.

The software: varies with accuracy and type of processing used. I did some work on a DOS based program a couple of years back that was OK but there were a couple of windows based alternatives. Can't remember the names now, but I'll see if I can find them...

The problem is, unless you get a _proper_ RTA done, back to back with your own and then you might as well have saved your time/money and got the RTA done by someone who knows what they are doing.

Finding someone who knows what they are doing, as Adam suggests, isn't all that easy as lots of places have an RTA knocking about and charge £25 a time for a setup....

john banks

Thanks for the replies guys. I think I might go RTAing to someone with a proper setup once I've "finished" my system. At the moment I have a dual ported bandpass Pioneer sub box which has a few +/- points:

1. It is really loud even with little amplifier power - I need to bridge my four channel amp to 150WRMSx2 to keep up with it only receiving 100W!

2. It's great for attaching amps to.

3. SQ and LF extension are not out of this world.

Hence I am thinking about a **really** hard hitting American amp PG/RF/Genesis etc and a sealed box to replace it. I reckon I might need about 500WRMS to match the sorts of hit this box gives when it comes "alive". And the wife's Fiesta may inherit some of the "old" kit as I've been intending to do an ICE job on that too, but lower budget.

Music I like - "all types" - i.e Jazz, Classic, Rock, Pop - in other words all the settings on your average cheapo "hi-fi" equaliser!

Will have another read of that JL tutorial.

rockin'Ru

Hi John.Looking for a good sub amp? Check out the MTX 500d. It's capable of over 700 watts. The 1000d will push near 2000.
They're smaller in size than a regular class a/b amp of the same wattage and are more efficient with input power.
Only real drawback is you can't use them for anything else but subs.
There are many brands of class d out there,the MTX is a very good bang-forthe-buck amp.