View Full Version : Comparing specs
Zaphod
03-04-2005, 05:17 PM
When comparing specs of different speakers, what should I be looking for? Just frequency response and power? Is it as simple as the broader the FR range the better?
s_tim_ulate
04-04-2005, 08:46 PM
Frequency response is pretty irrelevent nowadays. Most speakers can play almost everything, so it doesnt really hold as much significance.
Even response graphs will change totally in a car environment with bass loading and off axis response etc.
Power handling is also not a good indicator of anything really, as most people don't push their gear that hard, nor have the clean watts to get near that. It's surprising how loud even 50 w rms is.
Focus on things like sensitivity. Resonant Frequency etc. See if you can find the full range of thielle small specs these will give you greater insight into what the speaker can actually do.
Then theres the more 'emotional' aspects of the speaker/splits. Soft dome tweeter will give a much more musical feel for instance.
When listening in store, pay attention to the enclosure, the amp, the eq settings and the actual locations of the speaker. It is impossible to reproduce a car environment on a display board.
These will totally change the sound you hear
I dont pay too much attention to speaker specs. Different story with subs as these are predictable.
But generally u get what you pay for. A set of Morels rated at 100w rms will demolish a set of cheapo splits rated at 200 w rms. They are much more sensitive, generally have a very light moving mass in comparison.
Peace
Tim
Mr ©harisma
05-04-2005, 01:05 PM
Very true. Remember with subs a good rule of thumb. Ill use the standard Pioneer 800W 12inch subs and my Boston Pro 12.5lf. Both are rated at 400WRMS.
Pioneer is $200odd although you can get them boxed for $150 these days.
Boston sold for $599 but has been replaced with the super G5 woofer.
So they both are recommended in a 1cuft enclosure, 400WRMS nominal, big motor structures, they should be pretty much the same SPL and SQ? Why pay the extra for the Boston....
Well lets just say for the 2 400WRMS woofers, the pioneer is 89db efficiency where the boston is up around 97-98db. For every 3db increase you will need double the power. One way to increase the effiency is through the box, i.e vented designs ( ported / bandpass ). That means in theory, for the Pioneer to be = on SPL in a sealed box you would need around 3 times the power ( 1200WRMS :shock: ) to achieve a similar result. Dont think so.
In SQ a tonne of money have been invested in the cone / spider / magnet structure of the boston giving it a very natural sound that the American woofers usually have. The Pioneer has not had near the reaseach nor the exotic materials to match the SQ of the more superior boston woofer. This is why the Pioneer like the sony have a high Q effect.
You will get what you pay for, if your just happy with bass by all means the Pioneer / Sony woofers are ok, but if you want more detail spend a little more money and look elsewhere than Autobarn or strathfield. :D
Zaphod
05-04-2005, 06:44 PM
Thanks guys. I guess I'm trying to compare speakers without having the benefit of hearing them. <dumb question> What do SPL and SQ mean? </dumb question>
s_tim_ulate
05-04-2005, 06:52 PM
soz, SPL = Sound pressure level. Basically people that like the doof doof. This is all aiming to get something loud. Generally big subs big amps and little thought for quality.
SQ = Sound quality = Aiming to reproduce the frrequencies as the sound engineers intended. = Flat responses. Good staging etc. Can get loud as well, but thats just an added benefit.
:cool:
Here's some technical babble to confuse you even more. :) Some relevent some not so...
Theile-Small Parameters
B Magnetic flux density in gap, in Tesla-meters (TM)
BL The magnetic strength of the motor structure. "Expressed in Tesla meters, this is a measurement of the motor strength of a speaker. Think of this as how good a weightlifter the transducer is. A measured mass is applied to the cone forcing it back while the current required for the motor to force the mass back is measured. The formula is mass in grams divided by the current in amperes. A high BL figure indicates a very strong transducer that moves the cone with authority!"
C Propagation velocity of sound at STP, approx. 342 m/s
Cas Acoustical equivalent of Cms
Cmes The electrical capacitive equivalent of Mms, in farads
Cms The driver's mechanical compliance (reciprocal of stiffness), in m/N
D Effective diameter of driver, in meters
F3 -3 dB cutoff frequency, in Hz
Fb Enclosure resonance (usually for bass reflex systems), in Hz
Fc System resonance (usually for sealed box systems), in Hz
Fs Driver free air resonance, in Hz. This is the point at which driver impedance is maximum. "This parameter is the free-air resonant frequency of a speaker. Simply stated, it is the point at which the weight of the moving parts of the speaker becomes balanced with the force of the speaker suspension when in motion. If you've ever seen a piece of string start humming uncontrollably in the wind, you have seen the effect of reaching a resonant frequency. It is important to know this information so that you can prevent your enclosure from 'ringing'. With a loudspeaker, the mass of the moving parts, and the stiffness of the suspension (surround and spider) are the key elements that affect the resonant frequency. As a general rule of thumb, a lower Fs indicates a woofer that would be better for low-frequency reproduction than a woofer with a higher Fs. This is not always the case though, because other parameters affect the ultimate performance as well."
L Length of wire immersed in magnetic field, in meters
Lces The electrical inductive equivalent of Cms, in henries
Le "This is the voice coil inductance measured in millihenries (mH). The industry standard is to measure inductance at 1,000 Hz. As frequencies get higher there will be a rise in impedance above Re. This is because the voice coil is acting as an inductor. Consequently, the impedance of a speaker is not a fixed resistance, but can be represented as a curve that changes as the input frequency changes. Maximum impedance (Zmax) occurs at Fs. "
Ms The total moving mass of the loudspeaker cone.
Mmd Diaphram mass, in grams
Mms The driver's effective mechanical mass (including air load), in kg. "This parameter is the combination of the weight of the cone assembly plus the ‘driver radiation mass load’. The weight of the cone assembly is easy: it’s just the sum of the weight of the cone assembly components. The driver radiation mass load is the confusing part. In simple terminology, it is the weight of the air (the amount calculated in Vd) that the cone will have to push."
n0 The reference efficiency of the system (eta sub 0) dimensionless, usually expressed as %
p (rho) Density of air at STP 1.18 kg/m^3
Pa Acoustical power
Pe Electrical power
Q The relative damping of a loudspeaker
Q Parameters "Qms, Qes, and Qts are measurements related to the control of a transducer's suspension when it reaches the resonant frequency (Fs). The suspension must prevent any lateral motion that might allow the voice coil and pole to touch (this would destroy the loudspeaker). The suspension must also act like a shock absorber. Qms is a measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs. Qes is a measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock. Qts is called the 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same.
As a general guideline, Qts of 0.4 or below indicates a transducer well suited to a vented enclosure. Qts between 0.4 and 0.7 indicates suitability for a sealed enclosure. Qts of 0.7 or above indicates suitability for free-air or infinite baffle applications. However, there are exceptions! The Eminence Kilomax 18 has a Qts of 0.56. This suggests a sealed enclosure, but in reality it works extremely well in a ported enclosure. Please consider all the parameters when selecting loudspeakers. If you are in any doubt, contact your Eminence representative for technical assistance."
Qa The system's Q at Fb, due to absorption losses; dimensionless
Qec The system's Q at resonance (Fc), due to electrical losses; dimensionless
Qes The driver's Q at resonance (Fs), due to electrical losses; dimensionless. "A measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock."
Ql The system's Q at Fb, due to leakage losses; dimensionless
Qmc The system's Q at resonance (Fc), due to mechanical losses; dimensionless
Qms The driver's Q at resonance (Fs), due to mechanical losses; dimensionless. "A measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs."
Qp The system's Q at Fb, due to port losses (turbulence, viscousity, etc.); dimensionless
Qtc The system's Q at resonance (Fc), due to all losses; dimensionless
Qts The driver's Q at resonance (Fs), due to all losses; dimensionless. "The 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same."
R Ripple, in dB
Re "This is the DC resistance of the driver measured with an ohm meter and it is often referred to as the 'DCR'. This measurement will almost always be less than the driver's nominal impedance. Consumers sometimes get concerned the Re is less than the published impedance and fear that amplifiers will be overloaded. Due to the fact that the inductance of a speaker rises with a rise in frequency, it is unlikely that the amplifier will often see the DC resistance as its load."
Ras Acoustical equivalent of Rms
Res The electrical resistive equivalent of Rms, in ohms
Rms "This parameter represents the mechanical resistance of a driver’s suspension losses. It is a measurement of the absorption qualities of the speaker suspension and is stated in N*sec/m."
Revc DC voice coil resistance, in ohms
Rg Amplifier source resistance (includes leads, crossover, etc.), in ohms
Rms The driver's mechanical losses, in kg/s
Sd Effective piston radiating area of driver, in square centimeters. "This is the actual surface area of the cone, normally given in square cm."
SPLo Sound Pressure Level, usually measured at 1 watt, at 1 meter in front of the loudspeaker
Vas/Cms "Equivalent volume of compliance", this is a volume of air whose compliance is the same as a driver's acoustical compliance Cms (q.v.), in cubic meters. "Vas represents the volume of air that when compressed to one cubic meter exerts the same force as the compliance (Cms) of the suspension in a particular speaker. Vas is one of the trickiest parameters to measure because air pressure changes relative to humidity and temperature — a precisely controlled lab environment is essential. Cms is measured in meters per Newton. Cms is the force exerted by the mechanical suspension of the speaker. It is simply a measurement of its stiffness. Considering stiffness (Cms), in conjunction with the Q parameters gives rise to the kind of subjective decisions made by car manufacturers when tuning cars between comfort to carry the president and precision to go racing. Think of the peaks and valleys of audio signals like a road surface then consider that the ideal speaker suspension is like car suspension that can traverse the rockiest terrain with race-car precision and sensitivity at the speed of a fighter plane. It’s quite a challenge because focusing on any one discipline tends to have a detrimental effect on the others. "
Vd Maximum linear volume of displacement of the driver (product of Sd times Xmax), in cubic meters. "This parameter is the Peak Diaphragm Displacement Volume — in other words the volume of air the cone will move. It is calculated by multipying Xmax (Voice Coil Overhang of the driver) by Sd (Surface area of the cone). Vd is noted in cc. The highest Vd figure is desirable for a sub-bass transducer."
Too long??? Pffft...
s_tim_ulate
05-04-2005, 06:52 PM
here's some more :)
Xmax/Xmech Maximum peak linear excursion of driver, in meters. "Short for Maximum Linear Excursion. Speaker output becomes non-linear when the voice coil begins to leave the magnetic gap. Although suspensions can create non-linearity in output, the point at which the number of turns in the gap (see BL) begins to decrease is when distortion starts to increase. Eminence has historically been very conservative with this measurement and indicated only the voice coil overhang (Xmax: Voice coil height minus top plate thickness, divided by 2). Xmech is expressed by Eminence as the lowest of four potential failure condition measurements times 2: Spider crashing on top plate; Voice coil bottoming on back plate; Voice coil coming out of gap above core; Physical limitation of cone. Take the lowest of these measurements then multiply it by two. This gives a distance that describes the maximum mechanical movement of the cone."
Zmax "This parameter represents the speaker’s impedance at resonance."
Zaphod
05-04-2005, 07:15 PM
Holy crap, thanks for that :) I'd guessed SQ = Sound Quality but thought maybe it was too obvious. I guess you could say SQ is *much* more important to me than SPL. :)
Or there is what we like to call SQL - Beautiful sound that can be turned up when needed. :D
That is what we specialise in. :)
s_tim_ulate
06-04-2005, 11:07 AM
This is what I gots :) smooth all the way till ur ears start to bleed... Then it all gets a little hazy...
:cool:
Zaphod
06-04-2005, 01:31 PM
This is what I gots :) smooth all the way till ur ears start to bleed... Then it all gets a little hazy...
:cool:
oooh, I want, I want!
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