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Head Unit vs Amplifier - how big a benefit?

Discussion in 'Motors' started by PardonTheWait, 3 Jun 2010.

  1. PardonTheWait

    Capodecina

    Joined: 26 Aug 2003

    Posts: 24,083

    S'up!

    I'm about to stick some components in the doors of my pug, just from the HU for now, and planning to do the rears later on as well. Undecided on what to do for the rear at the moment but that's another story.

    If I do end up amping them later on, am I going to see a really noticeable difference - enough to justify £100-200 on the amp itself?

    It's just that I don't know - I know that it's better but I've never really been in a position to compare with/without, if you know what I mean.

    Thoughts?

    Ta :)
     
  2. mrk

    Man of Honour

    Joined: 18 Oct 2002

    Posts: 87,702

    Location: South Coast

    A decent brand/model of HU with a good amp built in (mosfet 50w x4 for example) will give you plenty of control over sound output and give excellent sound quality too.

    Saves you £100-£200...
     
  3. Gav

    Wise Guy

    Joined: 21 Oct 2002

    Posts: 1,378

    Location: Republic of Scotland

    Headunit output is measured as PMPO unlike amplifiers which are measured at RMS.

    a 4x50w headunit will never perform to the same level as a 4x50w amplifier.

    So.. to answer the question.....

    Yes it is worth fitting an amplifier if you want to get the best from your speakers. It will be noticeable.
     
  4. malfunkshun

    Soldato

    Joined: 20 Aug 2003

    Posts: 6,685

    Location: Pembrokeshire

    Thats not true, output is measured using whatever method the manufacturer decides. Steer away from anything with PMPO on it though, it is generally used to make output appear to be higher, and has no set definition.
     
  5. Sin_Chase

    Capodecina

    Joined: 13 Jan 2004

    Posts: 20,580

    I never had any amps in my setups and it has been fine, I am not an audiophile in my car though!
     
  6. Gav

    Wise Guy

    Joined: 21 Oct 2002

    Posts: 1,378

    Location: Republic of Scotland

    Guess you don't know what PMPO stands for then..
     
  7. malfunkshun

    Soldato

    Joined: 20 Aug 2003

    Posts: 6,685

    Location: Pembrokeshire

    Peak music power output. It's tosh, and has no technical merit.
     
  8. jak731

    Soldato

    Joined: 17 Mar 2007

    Posts: 5,480

    Location: Plymouth

    Peak Maximum Power Output, he's not wrong btw. They could measure the peak power output from half a cycle of 40kHz and get a higher value than if they did the same with 1kHz, purely because the capacitors used will be more drained before reaching the peak of 1kHz. Of course they probably usually use a square wave which will give the highest PMPO possible.

    Always look for rms power.
     
  9. malfunkshun

    Soldato

    Joined: 20 Aug 2003

    Posts: 6,685

    Location: Pembrokeshire

    That more or less proves my point about PMPO being bunk, I have seen it advertised as Peak Music Power Output, Peak Momentary Power Output, Peak Max Power Output and a few others. It means nothing and is entirely unsustainable, as indicated by the 'Peak' bit.
    Anyway, back to the OP a discrete amp should be better than the built-in amp. But in all cases you generally get what you pay for. That said you put a poor signal through a good amp and you get a loud, but poor, noise.
     
  10. mrk

    Man of Honour

    Joined: 18 Oct 2002

    Posts: 87,702

    Location: South Coast

    Well you're partly wrong there. My recommendation is completely valid but the PMPO mention needed to be said, you're right there, but you're wrong about head units being measured (advertised) using the PMPO figure and that to get better sound you need to install a better amp. Well in that respect though I've certainly not come across any head units I've looked at advertising the power output using a PMPO figure.

    I proved that myself in fact by simply changing head unit and leaving the BMW amp in my car and ever since then my speakers sound like they're being driven by something a lot more high powered than a 50wx4 mosfet powered pioneer head unit.

    A good quality head unit will give better quality sound than a average HU with a good amp.

    An amp won't improve the source, it will just amplify the cruddyness of the sound coming out of the average HU.

    Since there's up to £200 to be saved here the logical solution is to get a good quality head unit and enjoy good quality sound as long as the speakers that are installed aren't made of paper.
     
    Last edited: 3 Jun 2010
  11. Gav

    Wise Guy

    Joined: 21 Oct 2002

    Posts: 1,378

    Location: Republic of Scotland

    The "peak" part is exactly why manufacturers use it. It gives their headunits the illusion of being powerful when they are simply not.. Just because the boxes don't show it doesnt mean they aren't using it.

    4x50watts from a 10-15 amp supply.... I think not.
     
  12. Gav

    Wise Guy

    Joined: 21 Oct 2002

    Posts: 1,378

    Location: Republic of Scotland

    Probably because the voltage of the outputs from the new headunit is far higher than the voltage supplied from the BMW unit. Your BMW amp has no gain control so you cannot match the systems. This generally results in a faster deterioration in quality at high volume and can also lead to premature failure of the speakers
     
  13. james.miller

    Capodecina

    Joined: 17 Aug 2003

    Posts: 19,504

    Location: Woburn Sand Dunes

    Massive difference, no matter what the head unit is. i picked up a cheap vibe a4 for about £130 and even that and the real entry end of the market made a huge difference over my kenwood bt8044u. Discounting the obvious difference in power delivery (the a4 is a 4 channel amp supposedly capable of 2x500w RMS / 1x 500w & 2x250w RMS / 4x 250w RMS in to 4 omhs and i dont doubt it for a second when it packs 3x 35amp fuses) it tightened up the sound no end on the front speakers.

    he isnt wrong, try and find a headunit that quotes RMS power 20hz-20khz. Alpine dont quote RMS at all anywhere in their literature for any of the headunits ive had a quick look at, just for example, and i know damn well kenwood doesnt :p
     
    Last edited: 3 Jun 2010
  14. Stormster

    Mobster

    Joined: 18 Oct 2002

    Posts: 4,672

    Location: Stoke-on-Trent

    Pioneer quote RMS figures @ 4x22w RMS for most of their onboard MOSFET amps but can't remember distortion figures and at what freq it's measured at.
     
  15. PardonTheWait

    Capodecina

    Joined: 26 Aug 2003

    Posts: 24,083

    Still none the wiser then :D

    HU is an Alpine CDE-111RM, the components I bought are Alpine SPG-17CS. Once the comps are in I'll see how happy I am with them, I'll probably be happy enough tbh and will likely only replace the rears as well.

    Thanks :)
     
  16. Liquidfox

    Mobster

    Joined: 26 Sep 2007

    Posts: 4,119

    Location: Newcastle

    To be honest, replacing the rears is a waste of money, if you want better sound, get a small sub, something like an 8" or 10" would do fine and give you much crisper bass without sounding like you're part of the local McDonalds crew :)
     
  17. PardonTheWait

    Capodecina

    Joined: 26 Aug 2003

    Posts: 24,083

    I haven't decided what to do with the back yet - I think you might be right though. The 306 has got a cavernous boot so a little sub shouldn't take up too much room.

    Ta :)
     
  18. mrk

    Man of Honour

    Joined: 18 Oct 2002

    Posts: 87,702

    Location: South Coast

    Actually yes you're quite right they do quote it as "maximum power output) alongside continuous power output in the manual so my apologies for that. FWIW my manual shows:

    [​IMG]

    Still, I wouldn't put all your efforts into getting high wattage figures either way, you'll still get excellent sound loudness and quality even from a seemingly low continuous output figure Good amps don't need high watts to go loud and be crisp. Just look at home amps NAD, Rotel, Marantz etc, they're 25/35/50w rms yet kick out high quality sounds :)
     
  19. eatcustard

    Mobster

    Joined: 20 Feb 2010

    Posts: 4,504

    Location: Darkest Worcestershire

    To get the best out of components, amp them.

    and sound proof your doors for better sound quality
     
  20. james.miller

    Capodecina

    Joined: 17 Aug 2003

    Posts: 19,504

    Location: Woburn Sand Dunes

    yeah, 50hz-15khz.....5% distortion ;) you are realistically looking at half that if you keep the distortion below 1%.

    you shouldnt need a lot of power for anything, assuming your car is well sound proofed and your speakers are efficiant :)


    with a few notable differences - much much lower amounts of distortion, power quoted across the full audio spectrum, vastly better handling with low impedance drivers / difficult loads ect. The NAD c326bee for example, 50w RMS output at 0.009% distortion.
     
    Last edited: 4 Jun 2010