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Old 9th September 2009, 12:27   #1
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Default Sq & Spl


Frankly, while I love listening to music, in cars and at home, I would like to know more about terms such as SQ and SPL. I have read them a number of times on this forum, but none when mentioned, explained them in detail or in particular.

In my Blaupunkt head unit, I have SQ setting of 1.0, 1.5 and 2.0. But on selecting either of them, I don't notice any appreciable difference to the sound. My current setup in the car is plain jane - Hamburg MP57 with JBL co-axials in the front and JBL 6X9 in the rear (Parcel Tray).

I would appreciate if you can let me know how these both are measured, used, implemented, procedure for enhancements of these factors (SQ & SPL) in layman terms.

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Old 9th September 2009, 13:04   #2
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Always use search before posting a query .
You can get the complete info here :

Last edited by k2max6 : 9th September 2009 at 13:05.
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Old 9th September 2009, 14:47   #3
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any setting that you have in an electronic item that implies it is after what most people term SQ i would view with a healthy dollop of suspicion

generally speaking and leaving out any settings on a headunit this is what the terms imply

SQ = sound quality

this is not measured by any number - its a subjective judgement on how good a system sounds and it is based on how smooth and linear the sound is ie most of the time equal amounts of tonal balance ie there shouldnt be a leaning toward any part of the frequency range and you should have more or less equal amounts of bass, midbass, midrange and treble - the idea is that the music should sound smooth and realistic and present to you a realistic soundstage - and by this we mean that you should be able to imagine the recording sounding like a live performance in front of you. You should also get a feeling of space between each instrument and hear the detail of each instrument within the recording

the term SPL refers to Sound pressure level

most people take this to mean when they have an excessive amount of bass added in to their sound system and it plays very loudly especially in the bass area of the frequency spectrum however to me that is an incorrect way of looking at actual SPL. I personally would term that as a pounding system rather than an out and out competitive SPL system because SPL is actually a very competitive category and the people who are successful at it have vehicles that are designed to do more than just be loud

in order to succeed with pure SPL you need to determine the resonant frequency of the vehicle - then you need to tune the subwoofer system to play at this resonant frequency to reinforce the sound output you achieve - hence you would use tuning aids when designing your subwoofer enclosure and obviously a ported enclosure is a preference since it produces around 6db more of SPL than a sealed enclosure and also you can tune by varying the port dimensions to adjust port volume or length and diameter to adjust for the frequency you want to tune toward

for me a pure SPL vehicle will not be very musical since it is tuned to peak at specific frequencies which reinforce the pressure levels at specific frequencies which is why it will be able to produce startling numbers of pressure levels but as opposed to this a "pounder" vehicle or "ground pounder" will still remain very musical when played at extremely large levels of output but you may be disappointed by the actual measured level of SPL you achieve with one of these because surely something that sounds loud to your ear will measure loud to a real time analyser or db meter ... right .... actually thats a tad bit incorrect. I have come across vehicles that play blindingly loud bass that will actually make you feel like you havent eaten breakfast and make you feel like you want to throw up which measure disappointingly low SPL numbers and the reason for this is that they were not tuned to specific frequencies hence the actual resonant frequency of the car cancelled the actual pressure buildup and yet ive listened to cars that sounded disappointing when playing music but play a frequency tone at a specific frequency and have it tuned to the resonat frequency of the actual vehicle body then these sounds actually reinforced the vehicles actual resonant frequency and achieved SPL levels above 160db while still sounding bearable with music that has lots of pounding bass (normally a kick drum at around 150db+ can actually deafen you if you play it in sudden bursts)

you will get varying definitions but most people who are into sound competitively tend to think along the lines i do so you should take my definition as being my own personal opinion

EDIT : sorry ive forgotten to add that for SQ there is no quantitative way of measuring it because it is a subjective opinion based on what you hear or sometimes what you done hear (absence of any form of distortion) - whilst SPL is based on a logarithmic scale measured in decibels db's. the higher the db's the higher your SPL and an increase of 3db's will give you a MEASURED doubling of your SPL level BUT for you to perceive any sound being around twice as loud as another it needs to be around 10db louder then only does your brain interpret what you hear as being twice as loud

BTW one more thing ive just seen that link to a discussion above - what most of the guys refer to as SPL there is actually a parameter called "sensitivity" or sometimes termed "efficiency" which is the amount of SPL a speaker produces at a specific distance (usually one metre away) given one watt of power - so that definition in that link is 100% something that id take with a huge pinch of salt

Last edited by naughty001 : 9th September 2009 at 14:56.
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Old 10th September 2009, 14:08   #4
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@rkavthekar. this is not about SQ or SPL as you have described / expected.

Perhaps you should read the manual first? Page 44 under Sound settings. What you have described is QFAC, which is the setting that controls the range of frequencies around the Center Frequency selected for the Bass or Mid equalizer to apply the Gain that you set. Imagine a bell curve: the center is Center Frequency, the width is QFAC and the height is Gain.

Of course it has an effect which is audible. Listen carefully with known music from a CD, you will be able to hear the difference. It is noticeable enough even with FM signal.

Last edited by DerAlte : 10th September 2009 at 14:10.
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