Author Topic: I got your power, Right Here.  (Read 13771 times)

Offline dflee

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I got your power, Right Here.
« on: July 25, 2016, 10:42:03 AM »
Am in a dilemma and would like some advice.
Things I think I've learned through reading:
1. Although a speaker has a high efficiency, if there are multiple drivers it can be pretty power hungry. Question here is does it have to be continuous or just plenty of reserve power. Can I get by with 25 or 30 watts as long as I have a K reserve (is there even such a thing)?
2. Clean, efficient low power is better than higher power crud.
Q- Is there a way to determine if a good lower power amp has enough oomph to power a multi driver speaker without clipping? An example would be the Luxman M200. It states 35 watts into 4 ohm but doesn't tell reserve or peak power. Is that enough for a multi driver speaker. The speaker manufacturer states the speaker will work with as little as 15 watts but recommends 200. Here again it isn't put in terms of peak or continuous. How does one interpret or put it together with any sense?
Any input would be appreciated even if it's just to tell me I'm fubar (cause even that is helpful to know).
"Enjoy pleasure, not because it is fleeting, but because it exists at all." Sacrament, Clive Barker.

Offline _Scotty_

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Re: I got your power, Right Here.
« Reply #1 on: July 25, 2016, 11:21:03 AM »
What does the mfgr. claim the speaker's 1watt/1meter sensitivity to be.
 If it was a 4 ohm speaker for example and had a sensitivity of 95dBwith 1 watt of power input, then even with a 4 ohm load presented to the amplifier, it won't take much power to play loudly. 10 watts in would yield 105dB at 1 meter.
 In most cases when the speaker is played in an actual room it is even louder.
Scotty

Offline dflee

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Re: I got your power, Right Here.
« Reply #2 on: July 25, 2016, 11:27:12 AM »
Speaker rating states: Sensitivity (room, dB@2.83V) is 92.
What's that mean?
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Offline HAL

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Re: I got your power, Right Here.
« Reply #3 on: July 25, 2016, 12:27:16 PM »
The spec means that if you drive the speaker with a 2.83V rms signal for a sinewave, the output at 1 meter will be 92dB SPL. 

Offline Hugh

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Re: I got your power, Right Here.
« Reply #4 on: July 25, 2016, 01:19:58 PM »
What he said. :)
Hugh Nguyen
Angel City Audio
Exclusive Melody US Distributor

Offline richidoo

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Re: I got your power, Right Here.
« Reply #5 on: July 25, 2016, 02:45:48 PM »
Legacy specs "in room" sensitivity, which is different than most companies quote anechoic sensitivity. In-room sensitivity adds in the room's reflections, to make about 1-2dB louder than anechoic sensitivity depending on type of room construction and materials and decor. Theoretical maximum room contribution is 3dB, that's probably what they add for their spec, so when comparing Legacy sensitivity to other speakers measured anechoically, subtract the 3dB.  We listen in a room, so in room is real world sensitivity, but we all have different rooms, so it's impossible to compare in room sensitivity, while anechoic sensitivity is more comparable, if nominal impedance rating is also considered.

No problem on the 35w Luxman. James Edwards has similar luxman on his Focus, works great. All big Legacys have low impedance dips with negative phase angle in the bass, and it draws a lot of power but it's is part of their successful recipe. But for moderately loud levels a very strong 35W like luxman should be enough. If you have loud dance parties or listen to loud rap with long low bass synth tones right in the highest current freqs, or if you play loud uncompressed music like symphonies then I'd go for 100W+ SS amp. But for normal loudish music listening <95dB it should be enough.

I listened to my Focus 2020 for a long time with 50w tube amp, which had less current than the 35W solid state Luxman. I loved it, very satisfying.  But it did distort and damage tweeters when I played loud dance music. Solid state can source current much better than tubes, so less of an issue, to a point.

Offline dflee

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Re: I got your power, Right Here.
« Reply #6 on: July 25, 2016, 03:47:09 PM »
So is that what they are referring to with the term reserve or peak power. Th Coda refers to itself as a high current amp. What does that mean. I always thought it meant it had a lot of reserve power. How does one determine if there is enough reserve power to properly run a speaker?
"Enjoy pleasure, not because it is fleeting, but because it exists at all." Sacrament, Clive Barker.

Offline _Scotty_

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Re: I got your power, Right Here.
« Reply #7 on: July 25, 2016, 04:35:24 PM »
You shouldn't count on "reserve or peak power" meet the speaker systems power requirements. There's really no standard for specifying what these terms actually mean.
At the end of the day they are marketing terms that may have nothing to do with the amplifiers behavior into real world speaker loads.
 The RMS measurement into a specific load resistance; 4ohms, 8ohms and perhaps 2ohms, are directly comparable between different amplifiers.
Depending upon the speakers stated impedance, and a 92dB at 2.83volts the amplifier you mentioned may be more than adequate to drive the loudspeaker.
Scotty

Offline HAL

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Re: I got your power, Right Here.
« Reply #8 on: July 25, 2016, 04:38:14 PM »
Does the amp have a spec for headroom?  Most SS amps have a 1-3dB headroom that is above the spec for rms power.  

Also short term transient power is what some folks call peak power.  That can be considerably higher if the signal is less than 10mSec.  

All depends on the amp and the specs.

Offline richidoo

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Re: I got your power, Right Here.
« Reply #9 on: July 26, 2016, 08:20:57 AM »
Reserve is potential energy stored in the power supply. It is stored in two ways, as magnetic flux in the transformer and as static electricity in the PS filter caps. In the case of Coda 4.3.2 amp, there is ample headroom/reserve with 1.4kVA tranny and 80mF filter bank, serving 4 channels rated 100W>8R. 4 channels can be bridged to two channels rated 400W>8R. There is no explicit 4 ohm rating, but it has handled the Legacys biamped for many years.

The problem is the amplifier output transistors are not as robust as the PS. Usually it's the other way around, and the PS sag protects the amplifier from overload. We see that sag in the Luxman with 4 ohm rating not doubling the 8 ohm rating. It will sag more into <4 ohms like legacy, or it may protect.

I'm pretty sure the Focus SE has impedance dip of 2.9 ohms on the chart I saw 5 years ago. The bass drivers and alignment hasn't changed since then, but the crossover might have changed a little. But Luxman is working fine on that, I don't know how loud or what kind of music James plays, you could ask him. It might be the same amplifier circuit used in both Luxman amps.

The Luxman M200 is rated 25W>8R stereo, 35W>4R stereo and 70W>8R bridged channels. So it has 1/4 the power rating of the Coda. It really depends on how you're going to use the speakers. You might only have 95dB SPL available at the bass impedance dip, that's pretty darn loud, but it's capable of more, so you'd be leaving some speaker performance on the table. But might be worth if you love the luxman's sound.
http://www.luxman.com/product.php?pid=16

Can you get the impedance and FR/phase charts from Legacy? I couldn't find them online.
« Last Edit: July 26, 2016, 10:30:37 AM by richidoo »

Offline dflee

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Re: I got your power, Right Here.
« Reply #10 on: July 27, 2016, 10:57:31 AM »
Hey Rich: Wasn't able to get the charts either (guess it's due to age) but was told that there is a dip at 30 hz to 3.8 ohm. Other than that it's flat at 4 nominal. Bent the techs ear with my situation and asked where would he go given the same. This led to an interesting discussion concerning amplification of today and yesteryear. The terminology of High Current was to have plenty of reserve power to not get dips or losses when energy is needed. The non-transformer type of amplifier doesn't have the staying power and so the newer types (digital I'm assuming) while may have a good deal of power is only for instantaneous or short burst and can not maintain it causing the sound to in effect chop off. It was recommended to have 200 to 250 watts for my speakers and over that could create problems for one with my age (speakers not mine). With less power, I just wouldn't be getting what the speaker was capable of delivering even if they weren't turned up to ear splitting levels. This has been an interesting journey so far and I hope to come out of it better informed. So to put it into terms I could understand the tech said as in any speaker there is a range of power that works best, try to get to the high side of that wattage and get what sounds best for what I can afford.
"Enjoy pleasure, not because it is fleeting, but because it exists at all." Sacrament, Clive Barker.

Offline richidoo

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Re: I got your power, Right Here.
« Reply #11 on: July 27, 2016, 11:48:35 AM »
That sounds like pretty good advice.

3.8ohms not bad at all! I bet the Lux would work OK for everyday listening. If you still want the ability to shake the walls when you are home alone, then you might want more. You have the Coda for that.  :thumb:

Offline _Scotty_

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Re: I got your power, Right Here.
« Reply #12 on: July 27, 2016, 01:07:44 PM »
As far as switching power supplies are concerned, if the bean counters don't decide a 200watt amp should only have a 200watt rated supply to limit the production cost, you shouldn't see a problem with sustained power demands.
 You could easily spec a 600watt supply for a 200 watt amp much the same way you spec a 750 toroidal transformer for the same application.
Another aspect of better performance relates to the impedance of switching supply. The bigger supplies have bigger switching mosfets rated for higher current throughput and they have a much lower RDS on spec, as result the amp just sounds a lot better with the bigger supply even if you can get away with running a smaller one.
Scotty

Offline dflee

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Re: I got your power, Right Here.
« Reply #13 on: July 27, 2016, 03:04:41 PM »
Was kinda thinkin the same thing. If the amp has enough power for peaks why would it need the reserve? But then you pay for the additional wattage and can lose some quality. Am I correct in stating not all watts are equal or are we getting into the aspect where most argue they are?
"Enjoy pleasure, not because it is fleeting, but because it exists at all." Sacrament, Clive Barker.

Offline _Scotty_

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Re: I got your power, Right Here.
« Reply #14 on: July 27, 2016, 03:44:52 PM »
All watts are definitely not equal. You can have an amp that will measure X amount watts at X amount of distortion on a test bench under static conditions into into a resistor. Under dynamic conditions the driver stage may suffer beta collapse and the amp falls down on the amount of power it can actually produce under real world conditions. This applies to solid state Class A as well as Class A/B designs. RMS power at a specific load is a place to start comparing apples to apples but is no indication of performance under dynamic conditions. Class D is whole different kettle of fish.
Scotty