Advantages of low impedance? |
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bassmish
Young Croc Joined: 28 October 2007 Location: MAAAANCHESTER Status: Offline Points: 1333 |
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Posted: 13 August 2008 at 7:06pm |
Hello, I was wondering whether anyone could shed any light:
Are there any advantages to running speakers at low impedances (matched to the amp of course)
for example 2 set ups of bass bins of some kind, one with the amp and speaker at 2 ohm, and the next at 4, both running the same power same music etc...?
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rich_gale
Old Croc Joined: 18 February 2008 Status: Offline Points: 2697 |
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if one amp will deliver 1000watts at 4 ohm, and one amp delivers 1000watts at 2ohm, the first amp(4ohm) is better. id rather use an amp above its impedance limit for bass. if you dont have enough power to run the amp with impedance headroom you should look for a bigger amp. 2ohm on anything less than top quality amps always has a negative effect when compared to the same amp running at 4ohm or 8ohm.
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bassmish
Young Croc Joined: 28 October 2007 Location: MAAAANCHESTER Status: Offline Points: 1333 |
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yes but why is it better to run at 4ohm, other than cable resistance, I've heard some things which have made me think that there are other factors involved resulting in audio quality.
I'm confused as to why anyone would use a big amp at low impedance to power say 4 scoops as opposed to 4 or 2 smaller amp3 at a higher impedances, just to save on weight (the potential losses involved with lower impedances seem far more influencual than carrying a few extra kilograms) so I thought there might be something else to be taking into account?
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sKs01
Old Croc Joined: 11 April 2008 Location: sheffield Status: Offline Points: 1744 |
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smaller amps tend in my experience to not be as manly on the bass end of things, especially with cheap amps, and if you can afford the £'s for good ones you end up having the much more attractive option of buying something even more powerful per £, it sometimes help to think in terms of efficiency i think for this small amps tend to be less efficient and can only draw a small amount of current so theirs a lot of potential waste of power especially when your in a situation with only a handful of outlets like i often am just my opinion and why i like big amps though.
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You're a big man, but you're in bad shape. With me it's a full time job. Now behave yourself.
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AndyWave
Registered User Joined: 30 March 2008 Location: Finland Status: Offline Points: 380 |
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Hi!
As I know, there are no advantages but drawbacks instead. You must use heavier cabling because of large currents, damping factor goes lower. Lows mostly won't sound so accurate.....Cheaper amps also tend to blow up. 2 ohms usually minimum per channel. The amps that accept 1ohm load could be used as arc welding machines.. If you have home runs from each cabinet(pair) to amp rack no special cabling is required. Special case could be the one with drive units available with different impedances 4,8 or 16 usually. Different models could have different B*L/Re for example. In Pori Jazz or similar, years ago (I've been a size of fire extinguisher back then) there were "only" Crest 10001+10001+8001 per side driving whole main pa. RL<2R per amp ch. Imagine amp failure at that situation. Think also the 2 friendly little amp racks. At least 8 wheels under them each......A advantage of using low impedance? At other end camco has released vortex 200 model little while ago. It uses +/- 200volt rails. Starts to be scary have that high voltages on speaker lines. With my mates at work we started thinking possible damages that could lead. Like arcing at slightly rubbed voicecoil and gap...... Andy |
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bassmish
Young Croc Joined: 28 October 2007 Location: MAAAANCHESTER Status: Offline Points: 1333 |
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yes, well the cable resistance is just a much bigger factor at low impedance (the cable resistance is a much more significant fraction of the total speaker impedance) and you end up using most of the power to heat up your cable, as if it were another driver in the cab. It's the same principles which explain why overhead power cables use such massive voltages to transport energy across the country. just seems that a lot of people want big amps to power multiple speakers but might as well just buy multiple 2k (smallish) amps and not waste your money on cable.
Anyone got any other ideas as to why you would wanna use big (4K+) amps and low impedance?
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rich_gale
Old Croc Joined: 18 February 2008 Status: Offline Points: 2697 |
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in the touring sector. the less weight you need to transport and set up the better. so a 4k amp running at its lowest impedance will be most cost effective. if the amp is a good one then the 2ohm impedance will still be getting some good damping factor value. personally, id use this type of amp scenario for a bank of mid-tops showing it a low impedancewhere damping factor doesnt not play such a vital role in control. and then use more of the same amps at 4ohm for the bass end. at 4ohm the amps have better control of the loudspeaker cone.
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bassmish
Young Croc Joined: 28 October 2007 Location: MAAAANCHESTER Status: Offline Points: 1333 |
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So get and amp for every bass driver and run them at 8Ohm bridge!..
I guess this weight thing is more of an issue for some.
I was looking for a reason other than that which has been repeated multiple times of the damping from cables, but I don't think there is one!
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Deadbeat
Old Croc Joined: 12 March 2008 Location: Singularity Status: Offline Points: 3167 |
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Oh wait, your amp has a shorter lifespan.
One amp per cab is very impractical. 8ohm bridge would be seen by the amp as 4ohm stereo. So one bin a side in 80hm stereo would theoretically be the best. Then any config in 8ohm bridge/4ohm stereo. then 2ohm stereo and 4ohm bridge. Andy's completely right, you could use 1ohm amps as arc welders. And believe it or not, there are some around. Edited by Deadbeat - 14 August 2008 at 3:03am |
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Away on extended leave.
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rich_gale
Old Croc Joined: 18 February 2008 Status: Offline Points: 2697 |
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I am talking about damping factor at the amplifier outputs. though this may be one of the only factors to look at in well built amps, unfortunately damping factor plays a vital role in bass quality.but there is a clear money and space saving advantage in using a amp at low impedance for mid-high applications.
but having 2u per bass driver is a ridiculous idea in any rig of size. the amp space will soon add up. for a club install id love to have a bridged macrotech running each 8ohm pd2450. the outcome would be unreal.
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