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Need Amplifier advice

S

Scrub206

Weaksauce
Joined
Aug 20, 2011
Messages
99
Ok so I'm completely new audio in general. So here is what I need and part of what I want.

So I want a 2.1 speaker set up for my PC and I want to get the Audioengine P4 passive bookshelf speakers. Now since they're passive, I need an Amplifier but I have NO idea where to even start looking into / about amplifiers. I know I need it to support the 2 bookshelf speakers and then a Sub woofer. The speakers are going to be used for mostly music, if that is helpful at all. Also I want headphone jack out the front and someway to switch between the Headphones and the speakers.

Also a side question I guess. Is it good to mix and match speakers? Like say one brand speakers and another brand Sub Woofer?

Thanks guys.
 
personally.. I wouldn't mix and match but if the different speaker is a sub.. I wouldn't worry about it as long as it's a quality unit that doesn't muddy up your AE's.

As far as amplifier.. Do you have a old receiver lying around? It would let you use your headphones up front and allow you to swap audio/video inputs easily. You can also use the spare inputs for other things like 360's, PS3's, BR player, etc.
 
You can get a nice integrated like an HK 3490 refurbed for a good price. Get an active sub, though. Passive will need DSP.

Er, I better ask your budget, first.
 
With a 2.1 system, you do not need the amp to support the subwoofer.
Some stereo amps can redirect bass to the sub, but it isnt necessary to use a sub in this way with stereo.
Many amps will have a 2nd line level RCA output which is also tied to the volume control (on a monitoring loop or similar), this is fine to feed to the subwoofer as long as it doesnt affect the output to the speakers - sometimes these connections are placed in parallel with the input which reduces sound quality, this isnt what you want, listen for any differences.

What you want to happen is for the main speakers to produce all the bass they can as deep as they go and then get the subwoofer to take over where the speakers stop, the sub producing the deepest bass.

A subwoofer with a high level input lets you connect it directly to the stereo speaker outs on your stereo amplifier.
This doesnt take power from the stereo amp, just the signal. The subwoofer converts it to a low level signal and then amplifies it with its own amplifier.
It doesnt affect the sound to your stereo speakers.

If the sub doesnt have a high level input, you can easily make one for a few $ with a "high to low level converter" from amazon, I use one of these.
This takes the high level output from the stereo amp and converts it to low level which is fed into the subwoofers RCA inputs.
This doesnt affect the sound to your stereo speakers.

Some stereo amps properly support a subwoofer.
This doesnt mean they amplify the subwoofers speaker, but they allow you to control the subwoofer from the stereo amplifier. (the subwoofer still uses its own internal amplifier)
This isnt necessary as once its set up it doesnt need adjusting, but its a nice feature if its free.

So dont worry about subwoofer support, whatever stereo amp you get, it can be set up properly.
The subwoofer should have at minimum:
Its own amplifier, a volume control, a high freq adjust control.
Useful extras are:
A high level input, a high level input volume control, phase control to match the bass timing with the speakers more accurately due to being located in different positions.

If you want very deep bass, get a subwoofer that can go down to 25Hz or lower.
They tend to cost more though for decent quality units, beware of BS specs.

Power isnt everything. +3dB sensitivity is equal to twice the power from the same rated amplifier.
So if one sub is rated at 100W RMS max power, 98dB/Wm sensitivity and another is rated at 200W RMS, 95dB/Wm, they will both be approximately the same max loudness, but the 200W amp will use twice the power.
Higher sensitivity is good as long as the sub is known good quality in other areas.
fyi
 
magnetik said:
personally.. I wouldn't mix and match but if the different speaker is a sub.. I wouldn't worry about it as long as it's a quality unit that doesn't muddy up your AE's.

As far as amplifier.. Do you have a old receiver lying around? It would let you use your headphones up front and allow you to swap audio/video inputs easily. You can also use the spare inputs for other things like 360's, PS3's, BR player, etc.
Click to expand...

No I don't have anything laying around unfortunately.

LeninGHOLA said:
You can get a nice integrated like an HK 3490 refurbed for a good price. Get an active sub, though. Passive will need DSP.

Er, I better ask your budget, first.
Click to expand...

I'm probably looking at spending roughly 200 on the amp give or take a few bucks. Tho that HK 3490 looks beautiful. I would probably put out a few extra bucks if the price was right for that. (aesthetically speaking).

@Nenu (not quoting it all just a few question)

So I'm looking for a woofer with a high level input? I'm assuming that's going to be a little more expensive then normal woofers. Also when looking at the the Speakers and amps and the speaker says "10-125W per channel" would I be looking for an amp that supports the MAX of that? like a 125watt amp? Also, you said most woofers have amps in them, would I not need to worry about if the "Main amp" can support that? Or would I need to split the difference in wattage?

Thanks.
 
Ideally yes, get a sub with a high level input and a connector/lead to use it.
If not, buy a high to low converter from amazon and plug it into the normal RCA input on the sub.
Many subs come with high level inputs, but its so cheap to add your own, it doesnt really matter.

I recommend having enough power to the main speakers so that you wont need to push the amplifier into clipping.
ie so you dont have to push the amp so hard that the sine waves heads get chopped off, starting to create square waves which can damage the amp and speakers (and your hearing).
Even an amp rated at much less than the speakers can damage the speakers when over driven hard.

To this end, my speakers are 200W RMS/ch and my amps are 300W RMS/ch (which also gives extra dynamic headroom), but I have power meters to see when I am pushing the amps hard.
Always choose amps and speakers based on "RMS" Watts, NO OTHER Watts.
If they dont have an RMS Watts rating, walk away, they are most likely trying to con you about their real power.
So yes, on low to mid power speakers, you should get an amp that can drive them fully if you intend to push them hard.

If you know that you are going to push a 125W speaker to its maximum, perhaps you should be looking at a 200W+ speaker?
Double the power RMS equates to approx double the sound pressure level.
If you have access to a system that allows you to monitor the volume level in dB, this is the same as adding +3dB.
If your budget doesnt allow, just get as good quality/high power kit as you can afford and upgrade later. Go easy on the volume level if you hear any distortion.

You will need to get a 3 channel (not stereo amp) if you want it to power the subwoofer from it as well.
You can get them, I use one for my mid and rear surround speakers, but its unnecessary and restricts your choice if you make this a design goal.
Get a sub with its own amp, its much harder to find one without its own amp anyway.
You can build your own sub and this isnt a bad option. But even then, I would still recommend putting a separate amp inside it.

fyi
If you can place a subwoofer close to a corner, you can get up to 2x the bass output compared to having it against 1 flat wall.
This is due to reflections from the wall(s) creating/building up standing waves between the sub and wall(s).
The same thing applies to normal speakers, bass is boosted a bit the higher the number of walls it is close to.
How close it is to each wall will vary which frequencies of bass are boosted.
Close to a wall, higher bass, further away from a wall, lower bass.
So you can tune the bass from the sub (and speakers) to some degree with their placement in the room.
 
Just wanted to say Nenu makes some good points but doubling the power only yields a 3db increase. You have to have a 10db increase to sound twice as loud.

And power is dynamic so a 300rms amplifier will not be putting out 300rms all the time only during loud peaks or very long sine waves. A 125rms speaker can only handle 125rms for a extended period of time without it burning out, because a speakers rating is its thermal load handling capability. but typically can handle higher wattages for short times. Also the ohm ratings are nominal and fluctuate depending on the frequency being played and is more often than not much higher than the ohm load stated, I.E its getting less than what the amplifier puts out and after warming up a speaker you get ohm rise.
 
I must say, I've bit off a little more than I can chew haha. Some of this is kinda confusing. (I've been reading the posts over and over). I have no idea how many watts I'm going to push or not sure what dB things will be at.

So I'm going to just start off with the Amp/Receiver and the Audioengine P4's. Now they're 10-120watt per channel speakers, which means i can use basically any amp that has at least 10 watts per channel? I'm going to look for something a little less expensive than the HK 3490.

Sorry I'm bad at this >.<


So im looking at this receiver: http://www.parts-express.com/pe/showdetl.cfm?partnumber=252-228
 
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I like that Denon better. I am going to want the speakers to fill the room (12'x16' or something). Also can that support a potential woofer?
 
Scrub206 said:
I like that Denon better. I am going to want the speakers to fill the room (12'x16' or something). Also can that support a potential woofer?
Click to expand...

Yes, click on the picture showing the back. You'll see the sub hookup. I'd definitely go with the denon over the Sherwood.
 
Emotiva XRM 6.1 speakers will SPANK the A4s for a bit more money. You should always buy the best speakers you can afford and go from there.

http://shop.emotiva.com/collections/speakers/products/xrm61

The denon receiver is ok if you want to keep the price down. I would personally try for something better used on audiogon or craigslist. It will do just fine. You can always upgrade over time. The great thing is that the emotiva speakers will continue to improve as you upgrade the rest of the electronics and you will not really miss having a subwoofer bc they hit pretty hard by themselves. This way, you can take your time saving up for a decent sub to get true bass.
 
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Those Emotiva XRM 6.1 speakers do look really nice but they wont fit where I'm going to be putting them :( I mean I guess I could put them on their side. also theyre 120 more than what I'm going to be paying for the P4's.
 
If you get those Emotiva speakers, make sure the amplifier you get can handle 4 ohms well.
Many amplifiers are rated for 4 ohms but dont sound so good as they are not designed to handle 4 ohm speakers well.

They are rated at 86dB sensitivity which is a little on the low side so you may want a bit more amp power to compensate.
For example, they will need 2x the power to sound as loud as an 89dB sensitivity speaker and 4x the power to sound as loud as a 92dB speaker.

There is no specified maximum amplifier power so you can be sure the crossover will handle very high power transients, as long as the speaker cones dont travel too far there will be no damage using a high power amp.
So if pushing for loud levels, observe how far the cones are moving on a loud bassy section to decide on the max level.

There appears to be an error in the specs, in the pdf manual, they are rated from 63Hz to 22KHz, on the linked webpage, they are rated from 53Hz to 22KHz, I dont know which is correct.
Regardless, they should be partnered with a subwoofer to get the deepest bass.

However, Emotiva make great sounding hifi for comparatively little money, you can be sure they will sound awesome.
But you will only get the best from them if you get a good amplifier that can handle 4 ohms well and supply a bit of power.

To this end, its worth considering an Emotiva amplifier as well, they have a LOT of clout for the money and they do not lie about the power handling, they exceed the the specs.
ie http://shop.emotiva.com/collections/amplifiers/products/upa200
This amp is only $300 and will give you true 200W RMS per channel into 4 ohms (125W RMS/ch into 8 ohms).
It has no volume control, so you will use your PCs volume controls or get a pre-amp later.
This is how you start to build a high quality hifi.

I use 2 Emotiva amps, well worth the money and I had to import them to the UK!
 
The best option for 2.1 is always to use active crossovers. This means getting an amplifier that can has a dedicated subwoofer out and adjustments.

It's necessary to filter low frequencies away from the small main speakers to reduce phase problems and loading on the main boxes. Any compromise with passive connections (so called high level connections) will be less than optimal. I personally run active monitors and an active subwoofer and the whole bunch is controlled by a pre-amp and an active crossover. When the extended bass frequencies are filtered from the monitors the system can produce an unbelievable loud sound.

The high level connections are a quick, cheap and dirty way to set up the 2.1.

Oh and regarding to the sensitivity: When looking at bass speaker sensitivity, the more sensitive a speaker is for its size, the less bass it will produce. This means that if you compare two drivers of let's say 10" size, odds are that the one with the lower sensitivity is going to extend much lower in the audio range. Meaning it will give deeper bass and ask for a lot of amp to do it.
 
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