 Advice on Samson amp/monitors |
arqtic
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After producing music with crappy pc-speakers and headphones for a while now, I want to get something better. I've already searched this site for some info.
I saw this second hand Samson Servo 500 power amplifier for ¤200. Now would it be a good idea to buy this one (or something like this one) together with some cheap hifi speakers untill I got enough money (which will take a while) to buy some decent monitors and then use the same amp?
Samson amp specs
All advice is welcome, you can also say what stuff you are using...
Thanks a lot!
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03-08-2004 17:35 |
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Soi 
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Same here, saw some second-hand/overstock active Samson speakers, but pitty that in the shop and on the Samson-site, they're quite silent on the the technical specs. I can't find any frequency-indication and stuff.
My guess is that it's a budget sort of speakers, but since i can't allow some a1-quality meat-speakers, i'm interested in buying these Samsons.
Someone some info for the bedroom-producer-league?
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03-08-2004 19:56 |
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Surya
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Don't know about the Samsons, but if you're on a tight buget, then the Alesis Monitor One Mk2 is a good choice (well, I kinda like them). If you're lucky you can find those for around ¤350
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03-08-2004 20:10 |
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thechronic
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You're better off with a decent hifi amp instead of a cheap pro amp. Samson is not known for making good equipment BTW, it's a budget brand like Behringer.
IMO you can better buy a hifi amp for ¤200 from a well-known brand (Panasonic, Sony, Pioneer, ...) It will have less watts than the Samson but it's very likely that it will sound much better.
There is one thing you have to keep in mind though, when you buy a new amp and speakers it's probably going to take several years before you are going to upgrade, so it's vital you buy the best you can afford at the moment. Do yourself a big favour and buy cheap studio speakers instead of cheap hifi speakers. For example get the Tannoy Reveals (less than ¤210 for a pair). If this is above your budget then save up for them instead of being stuck for years with hifi speakers that have accented highs and lows. The Reveals look very nice too so when you upgrade to better speakers later on you can still put them in your living room 
Anyway whatever you might buy and whatever your budget is, it's always going to be an improvement over monitoring on PC speakers, that's for sure 
I would just advice you not to rush it, every ¤100 more you spend the better the quality will be!!
Some general advice on reading the specs when buying an amp:
Watts (power)
If you buy an amp don't take any sales waffle about the amount of watts it delivers, because that's the least important thing in an amp and it's a measure that can very easily be tampered with. Remember seeing tiny little PC speakers boasting to have 250W, or car stereos that have 4x100W. A load of bull
You need to know the impedance in ohms and the THD (distortion percentage) before you can compare the Watt specs of two different amps. Also the specs have to be measured for the full 20Hz-20kHz bandwidth using pink noise.
The impedance is the 'resistance' of the speakers that are used. How lower this is, how higher the amount of watts the amp can deliver (because there is less resistance, duh). A typical speaker has an impedance of 8 ohms, but if you wire two speakers together in parallel they will have an impedance of 4 ohms (remember your physics lessons
).
One and the same amp can eg deliver 300W into 8 ohm (0.05% THD, 20Hz-20kHz) and 500W into 4 ohm (0.05% THD, 20Hz-20kHz). Usually the amps are rated in 4 ohms because this looks more impressive on the front panel. It might seem like a great idea to hook up two speakers on every output of the amp to get increased power and it works perfectly, but you get some drawbacks like increased heat dissipation and slightly increased distortion.
Note: specs of 2 ohms impedance are often supplied but can be ignored, running an amp in 2 ohms will make it overheat and will increase the THD to unacceptable levels. It's even illegal in some countries such as the USA to run amps in 2 ohms because of fire risks
The THD (Third Harmonic Distortion) is a measure for the amount of distortion an amp generates for a certain amount of power. Remember those supposed 250W PC speakers? They will undoubtly be able to deliver 250W but then at a distortion level of 50% and only for a very short time before they blow up
Any good amp can deliver much more power than it is rated at, but when you increase the power, you will also increase the THD. So it is necessary to know the amount of THD that is generated if you want to have a reliable idea of the power the amp can deliver. The manufacturers measure this by playing test tones through the amp and increasing the power until they reach a certain THD level. This way they can find out that a certain amp can eg deliver 500W at 0.05% THD.
Typical THD figures are 0.05% and 0.02%. Any figures above 0.05% should be taken with a big grain of salt.
The 20Hz-20kHz indication is important too. It indicates the frequency range for which the specs are valid. Cheap amps typically quote only one frequency (eg 1kHz) at which the amp performs best. So if you get a spec of "200W @ 4 ohms, 0.05% THD - 1kHz" you know the amp generates 0.05% distortion at 1kHz, but how much distortion in other frequencies? Maybe the bass or high end is awfully distorted?
So look out for the frequency range indication. BTW very good amps quote this for much larger ranges, such as 5Hz - 200kHz, this is ofcourse a better measurement
A sample correct Watt spec looks like this: 750W in 8 ohms with 0.05% THD (20Hz-20kHz)
Damping factor
This indicates how well the amp can control the exact movement of the speaker cones. You can look at it as the amount of 'grip' the amp has on the speakers. This is a very good indication of the sound quality of the amp.
Good amps should have a damping factor of over 500, while very good (and expensive 
) amps can have a damping factor of 2000 or higher.
Frequency response
This is the linearity of the amp across the frequency spectrum. It indicates if the amp can give the same output in the low end, the mid and the highs. This is usually not a problem in modern amps except for really cheap ones. It is measured in +/- dB across a certain spectrum.
Example: 20Hz-20kHz +/- 0.3 dB - this means that for every frequency from 20Hz up to 20kHz there is a deviation of max +0.3 dB upwards and -0.3dB downwards. So the maximum difference in response between the highest and lowest peak is 0.6dB.
On better amps this is usually quoted as +0dB/-0.3dB, which means that there are no peaks across the frequency spectrum, only a tail-off at the low and high end of -0.3dB.
If values higher than +/- 0.3dB are shown it is a bad amp. Good amps have +/- 0.2dB deviation or lower.
Very good amps can have a frequency response of eg 2Hz-150kHz +/- 0.1dB.
Slew rate
This is also a good indication of the sound quality of the amp. It indicates how quick the amp can make the waveform rise and fall which is very important for the clarity of the sound. It is indicated in Volts/millisecond. Good amps have higher figures here (they can make a change of more volts in one millisecond) but unfortunately this is usually not listed in the specs, except for really expensive amps.
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03-08-2004 21:17 |
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Surya
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Why don't you post the text in this message on a html or php page on the main site, this is something that should be clearly available to everybody visitng the site! If you want, I can fix this for you very quicly (incl forms to add new articles and such, php+mysql)
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03-08-2004 23:12 |
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thechronic
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Hmm yeah maybe I could turn this into a buying amps how to
Thanks for the offer but that's not necessary, thanks
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04-08-2004 01:43 |
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Surya
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| quote: |
Originally posted by thechronic
Hmm yeah maybe I could turn this into a buying amps how to
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Exactly...
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"In dnb you should make people jump not swim"
- Pieter Frenssen 2004
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04-08-2004 10:18 |
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arqtic
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now that's some feedback! 
Thanks a lot!
Gonna do some more research and think about it...
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04-08-2004 11:15 |
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djfreemc
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Have a few minor additions to thechronic's info.
A little example of how to temper with watts specs:
suppose a 2000 watt home surround system (just got it out of a folderke)
there are 6 speakers, all counted together
that makes 333 watts per speaker, still not bad one would think.
Then it's put in peak music power, the worst invention in the history of speaker systems. Peak power, while normally we speak in RMS so /2 = 150W but just peak doesn't do the trick, so we use peak to peak power here. /2 = 75 Watt then we all know there are positive and negative voltages in a normal audio signal, but these manufacturers don't /2 =37 watt. And just to make it all a little worse they offcourse use 4 or even 2 ohm impedance instead of the regular 8 ohms so we end up with only 18 or 9 watts per speaker 
My advice: look at the dBspl (dB Sound Pressure Level aka loudness) your system can produce, that's an objective mesurement that is hard to temper with. If u can't find this spec, look @ watts RMS @ 8 ohm +freq range. If the spec doesn't explicitly mention RMS, don't trust it.
The slew rate is indeed important to get good sound but not as critical as in some other systems because in a normal soundsignal u will never go from one extreme to another within for example a few nanoseconds.
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This post has been edited 1 time(s), it was last edited by djfreemc: 04-08-2004 19:25.
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04-08-2004 19:22 |
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Surya
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Yeah, and these days you see more and more PMPO (peak power) values on speakers. Really sucks!
Also look @ how many dB's you get for 1 watt @ 1 meter. The higher this is, the less power you need for higher volumes. Mine for instance are 88db @ 1 watt @ 1 meter, which is quite average I guess.
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04-08-2004 19:30 |
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thechronic
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| quote: |
Originally posted by djfreemc
Have a few minor additions to thechronic's info.
A little example of how to temper with watts specs:
suppose a 2000 watt home surround system (just got it out of a folderke)
there are 6 speakers, all counted together
that makes 333 watts per speaker, still not bad one would think.
Then it's put in peak music power, the worst invention in the history of speaker systems. |
You have a very good point here in mentioning PMPO
If you see PMPO in the specs then the advice is simple: don't buy it!
PMPO means Peak Momentary Performance Output, so it's the maximum power that the amp can deliver for a brief period. I mentioned this in my post for the so called 250W PC speakers, these would be rated in PMPO.
It's clear that this is a very unwanted spec, you want to know how much power the amp can deliver continuously, not for a couple of milliseconds
Manufacturers that are serious about their amps will never mention the PMPO rating, so if you see this, don't buy it
Another warning: sometimes the specs don't even say it when they used PMPO, but you can recognise this by looking at the THD. A PMPO rating will have a very large THD, way above 0.05%! So if the THD is not stated or has a high value it is probably measured in PMPO.
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05-08-2004 12:07 |
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thechronic
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| quote: |
Originally posted by djfreemc
Then it's put in peak music power, the worst invention in the history of speaker systems. Peak power, while normally we speak in RMS so /2 = 150W but just peak doesn't do the trick, so we use peak to peak power here. /2 = 75 Watt then we all know there are positive and negative voltages in a normal audio signal, but these manufacturers don't /2 =37 watt. |
You're confusing two things here: PMPO power vs RMS power and peak-to-peak power vs RMS power.
The PMPO is not mathematically related to the RMS power since PMPO is measured for a very brief time period and RMS is measured of a long period of time. One 3W RMS amp can have 100W PMPO while another 3W RMS amp can have 250W PMPO, just depending on how it is measured.
The RMS rating is calculated differently than you mentioned, the RMS rating = 0.707 * the peak-to-peak rating. 0.707 is the square root of 2. That's what the name RMS comes from, Root Mean Square
| quote: |
Originally posted by djfreemc
If the spec doesn't explicitly mention RMS, don't trust it. |
A serious company will always state the power in RMS, even if they don't explicitly mention it.
If you follow my advice above you'll know when they use PMPO, so you can recognise the bad ones.
For peak-to-peak ratings: probably there are a few cases where the peak-to-peak power is stated in the specs instead of the RMS power, but I have never seen or suspected it, so you can safely assume that it is always in RMS. There is only 1.25dB of difference between peak-to-peak and RMS anyway, so it's negligible.
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05-08-2004 12:33 |
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thechronic
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| quote: |
Originally posted by djfreemc
My advice: look at the dBspl (dB Sound Pressure Level aka loudness) your system can produce, that's an objective mesurement that is hard to temper with. |
This gives a much better indication of the loudness of the system (amp + speaker) indeed. Unfortunately it doesn't apply to amplifiers alone.
Every speaker has a different 'efficiency', depending on how it is built. Bass reflex speakers will i.e. give much more loudness than closed baffle speakers at the same power of e.g. 100W.
This is different for active and passive systems:
Active (amp + speaker):
Here the actual maximum loudness is given that the system can deliver. It is very easy to read, eg 108dBSPL @ 1 meter. If you stick your head at 1 meter from the active speaker and crank it up completely you will be hit with 108dBSPL
Passive (only a speaker, no amp):
In this case the manufacturers can't truthfully tell how loud the speaker will play, since they don't know which amp you're going to use.
They have found a very simple solution (like Surya mentioned), they measure it using 1W of power, also at a distance of 1 meter.
So if you have two speakers and one says it has 88dBSPL / 1W @ 1m and the other has 96dBSPL / 1W @ 1m you will know which one will go the loudest.
Important warning: higher values here do not mean that the speaker is better, only that it goes louder. The sound quality is completely independent from this!!!
When you buy speakers for your home studio, the quality is much more important than the loudness, believe me
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05-08-2004 13:05 |
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thechronic
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OK I have to give you one last piece of advice here on buying amps. I have mentioned before that the amount of watts is the least important thing to consider when buying an amp, and I'm going to prove it here for the disbelievers
Ofcourse I got carried away and have written way too much about the watts, but you really have to look at things like the damping factor when you buy an amp, not at the watts!!
Why watts are not important
The human hearing works in a logarithmic way, while speaker output works in a linear manner.
The difference in perceived loudness between two signals is measured in decibels (dB). An increase of 10dB means that it sounds twice as loud. So a 110dBspl sound is twice as loud as a 100dBspl sound. If an amp has to deliver twice the perceived loudness, it has to generate 10x the amount of power! So for every doubling in loudness you need and amp that is 10 times as heavy. This means that a 1000W amp is only 4 times as loud as a 10W amp!! 
The formula for this is:
loudness difference = 10 * log ( power1 / power2 )
So if you want to know the difference between a 1000W amp and a 250W amp you calculate:
10 * log (1000 / 250) = 6.02dB which is not very much
A couple more examples:
1000W vs 750W: 1.2 dB louder (no perceivable difference for the human ear!)
2000W vs 1000W: 3dB louder (barely perceivable)
So if you would chose a 2000W amp over a 1000W amp just because it seems to give you 1000W more you're completely on the wrong track!
For home studio use a 100W amp is more than sufficient, it will give you around 110dBspl @ 1 m using average speakers which is more than loud enough, it will make your walls shake
Just take my advice, if the sales guys start ranting on about the watts just ignore him and bluntly ask for the damping factor and frequency response graphs. You will instantly earn his respect, get a better deal, and go home with a better amp
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05-08-2004 13:31 |
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djfreemc
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| quote: |
Originally posted by thechronic
PMPO means Peak Momentary Performance Output |
I was told it meant peak music power output or something, but your explanation sounds more logical indeed
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| quote: |
Originally posted by thechronic
You're confusing two things here: PMPO power vs RMS power and peak-to-peak power vs RMS power.
The PMPO is not mathematically related to the RMS power since PMPO is measured for a very brief time period and RMS is measured of a long period of time. One 3W RMS amp can have 100W PMPO while another 3W RMS amp can have 250W PMPO, just depending on how it is measured.
The RMS rating is calculated differently than you mentioned, the RMS rating = 0.707 * the peak-to-peak rating. 0.707 is the square root of 2. That's what the name RMS comes from, Root Mean Square |
I knew that about the sqaure root of 2
Just explained it wrong
. The way I calculated was based on the peak voltage, so in power u will end up with X2 anyway. (for a sine wave that is)
About ptp & pmpo, I was told they were identical but u have a good point, if u shorten the peak time in wich u measure, the rating will go up like a rocket.
Anyway, not gonna fill up this thread with tech discussions any further. Just keep ya eyes open!
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05-08-2004 19:50 |
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Surya
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I was always told that a 3db gain was twice as loud, you say a 10db gain is needed for that 
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05-08-2004 20:13 |
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djfreemc
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| quote: |
Originally posted by Surya
I was always told that a 3db gain was twice as loud, you say a 10db gain is needed for that
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A 3dB gain is Twice the power (as in the example with the 1000 and 2000 watt amplifier), not what ur ears will experience as twice as loud.
In dB loudness u are right, this is dB power.
Just for the record, dB itsself is not a unit. It is a way to express the ratio between 2 values of a same unit, with 1 reference value. That's why u should actually always mention what kind of dB's u are talking about. A few examples: dBm, dBV, dBmV, dBµV, dBspl, .... dBspl is used for loudness, dBm for example is with 1mW as reference.
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The mysteries of the distorted snare...
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This post has been edited 2 time(s), it was last edited by djfreemc: 05-08-2004 20:53.
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05-08-2004 20:42 |
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Surya
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Ah, yes, ofcourse, stupid me 
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"In dnb you should make people jump not swim"
- Pieter Frenssen 2004
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05-08-2004 20:48 |
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