Amplifier Audio Characteristics

[Guest]

<font color='#000000'>Peter,

To understand the speaker/amplifier marriage, you need to consider the speakers impedance curve (different impedance levels at different frequencies), because 4 Ohm speakers can dip to 2 Ohms at certain frequencies.  Speakers are rated at nominal impedance which is essentially just an average.

You also need to consider the amplifier's current delivery capability (peak amps per channel) which means large power transformers (like &gt;1.5kVA) and large power supply filter capacitors (like &gt;80,000µF).  This means watts per channel are not the only deciding factor.  For instance, take  two amps with the same 170wpc at 8 Ohms, but the second amp (with high-current capacity) doubles it's wpc at 4 Ohms (340wpc) and then doubles again at 2 Ohms (680wpc).  This second amp is going to be able to drive the difficult speakers (4 Ohms or less) without running out of power.

You may not be able to get an amp like the second example above cheaply, but my ballpark says you need an amp with at least 45 peak amps per channel and 100,000µF of power supply filter capacitance to do 4 Ohm speakers justice, I doubt the Denon 5800 provides that, but maybe you can check the manual.</font>

 

[gene]

<font color='#000000'>Hi Bruce;

The Denon has 1.2kVA , 66kuF of power supply capacitance. &nbsp;BTW, my speakers dip down to 3.5 ohms and 90dB SPL efficiency yet the 5803 drives them quite well. &nbsp;I also have an Klipagon 3CH power amp with 2KVa , 150kuF as a reference. &nbsp;I believe your statement regarding needing at least 100kuF of capacitance is a sweeping generalization. &nbsp;Part of the reason why my Klipagon amp needs so much &nbsp;power supply capacitance is because it has an unregulated supply. &nbsp;The advantage here is it will deliver near wall current loads if taxed and doesn't lose any power in regulation since the push pull topology and enormous power supply caps does a very good job of that.

The bottom line here is it all depends on the speakers being used and listening preferences. &nbsp;I normally never listen past 100dB in an 18' x 20' room, which is pretty loud. &nbsp;The amps in the Denon receiver have no qualms with this. &nbsp;Again, the perceived need for power is often overrated. &nbsp;Many high power amps have noise floors too loud to justify for serious audiophile playback.</font>

 

[petermwilson]

<font color='#000000'>Hi Guys, and I enjoy this discussion as it teaches me things about power ratings and speaker needs that are not apparant to most laymen.

I don't think the Denon dealer was trying to sell me an amp per-se, because it was the speaker manufacturer that said that due to these 2 woofers &nbsp;which are back to back in a configuration that Linn inaugerated called isobaric that necessitates all this juice, and Totem Acoustics doesn't sell amps. (amazing for stand mounted speakers)

One of the reviews of the 5803 that I read suggested that it would go well with the Citation 7 for such applications.
I guess the saying that you can never have too-much power is true. &nbsp;so since a pair of these speakers is $6000cdn plus the cost of an amp, I will satisfy myself with the Model 1's for a while. &nbsp;Anyway the Mani-2's may have been overkill for this room 10-12'w x15' L x 8' H

thanks again
Peter m.</font>

 

[Yamahaluver]

<font color='#0000FF'>I have a MX-1 attached to my main out on the DSP-AZ1. The MX-1 can go up to 1000W at one ohms so it is a high current, high power amp but to match with the rest of the channels I have to reduce its volume to 1/3 power. At this level, my ears are already at pain threshold at -20dB volume setting. Sure, the MX-1 sounds great when played in 2 channel mode but for that I already have a dedicated 2 channel amp setup. Point is, the need for SPL and power is more market driven and never fall for the salesman's trap. The Denon's amp section is hefty enough to drive the biggest speakers and you dont really need a new amp.</font>

 

[PaulF]

<font color='#000000'>Isn't it possible that different amps will interact with the same set of speakers in different ways, making them sound different? I tend to think it's the amplifier/speaker combination that's important. While I agree with the concept that any good amplifer, (high current output, low impedance output etc.) should drive a speaker reasonably well, speakers are notoriously complex impedances that produce back EMFs that may be handled by different amps in different ways.

For instance doesn't the ouput impedance of an amplifeir change with differing levels of negative feedback? So a solid state amp could get away with less feedback than a tube amp for a given output impedance. What about the back EMF, does the feedback loop carry it back into the amp in differing degrees?

Let's say we have two amps rated at the same power output, but one uses a pair of high current output transistors, the other uses 4 parallel pairs or lower current devices (perhaps matched, perhaps not), would this change the sonics audibly?

Paul</font>

 

[Khellandros66]

<font color='#000000'>Hi,

This is a really good debate, and very informative. &nbsp;As for me, I plan on buying an amp in the next year, making my Yamaha RX-V1300 a preamp. &nbsp;I plan on buying an ATI AT1802, then adding five more modules as the time goes by. &nbsp;I was wondering what peoples take on ATI is.

~

Bob</font>

 

[Audioholics]

<font color='#000080'>This is ridiculous. I can't keep deleting posts - I have better things to do.

No more baiting and no more name-calling. If this keeps up, we will restrict your (plural) posts to the Steam Vent only, or ban you for a week til you (plural) cool down.

I don't want emails about the &quot;inside scoop&quot; or who's been following who around what forums. Last warning. These forums aren't about &quot;you&quot;.</font>

 

[petermwilson]

<font color='#000000'>Hi guys,
I use 5 4ohm Totem Model1 speakers with 87db.
It is not a large room 10 to 12 ft x 15 max.

My upgraded 5800 at -19 volume is plenty for the most booming dvd's. If I bring the sound to reference level 00, it's deafeningly clear as a bell.

Peter m.</font>

 

[Guest]

<font color='#000000'>Paul,

<table border="0" align="center" width="95%" cellpadding="0" cellspacing="0"><tr><td>Quote </td></tr><tr><td id="QUOTE"> While I agree with the concept that any good amplifer, (high current output, low impedance output etc.) </td></tr></table>
This is a BIG part of the answer, IMO, most receivers just don't have the power supply capacity to provide high-current output i.e. their voltage delivery sags when they are asked to produce more than they are capable of.  This typically asserts itself as clipping and or distortion: the speaker output starts to sound strained to your ears.

But you are correct, it depends on both the speaker's frequency dependant impedance curve (i.e. not the nominal or average impedance) and the size of the room.</font>

 

[Guest]

<font color='#000000'>Peter,

That is a pretty small room by acoustical standards (12 x 15 x 8) = 1440 ft3. and I expect many things would work pretty good in that room.

How far is the listening position from the LRC speakers (left-right-center)?  It almost sounds like you are close to a near-field listening environment.</font>

 

[petermwilson]

<font color='#000000'>Well Bruce,
I was even being generous on the 12' because that is at the back of the 15' depth most of it is actually 10' and I have a huge tosh 65h80 which is 27&quot; deep up front,

So I'm 10' from the center speaker (on top of the tv) I sit in the right corner of the room eye to screen is 11'.

There is one pair of stand mounted Totem speakers &nbsp;7' and 10' from the listening position. &nbsp;I have surround &quot;A&quot; wall mounted dipole Axiom qs4's 4' and 8' away. &nbsp;Surround &quot;B&quot; is adjacent to the listening poition where the room opens to the 12' mark and are the other pair of Totem which I'm centered to about 4.5' either way.

there is also a pair of Monitor Bronze 4si's effects on the shelf of a double sliding door closet(doors remooved) 3' above my head and directly behind me.

I generally describe my HT as being in a very large car. It's the master bedroom.

My tv is totally ISF'd including the removal of the reflective screen and I use a scaler that brings everything to 1080i so if I want to center myself i can move the couch up tobe 8.5' eye to screen with no visible artifacts.

I'm pretty big into HIREZ music (140 discs) and depending on the music I use different recomended speaker allocations found at the &quot;SECRETS&quot; SITE. I also use a 7disc dvd-a and 5disc sacd players

Anyway thats it. Pretty cosy (small) huh!!

Peter m.</font>

 

[PaulF]

<font color='#000000'>Bruce,

As you say, the hard part is trying to figure out how an amp will respond to transients. If the amp can supply all the juice (current) in the world, then no transient or load impedance should be able to drop the signal voltage and cause distortion. Even with the best power supplies though at higher output levels things like the slew rate of the output stage come into play.

But as far as power supplies go I just think the current transformer/mass capacitor storage method has reached its limits and don't understand why manufacturers don't turn to switchmode power supplies more often. Ive even seen an amp with nearly half a farad of storage, you look inside these monsters and they have massive copper bus bars running across huge banks of capacitors. All that metal and weight, arghhh, it reminds me of the battery rooms inside a telephone exchange. &nbsp;Most receivers don't use toroids which makes their transformers even larger for a given level of performance..

A linear power supply tops up the filter capacitors every 8.3ms while a switchmode (running well outside the audible band) can top up the filter caps in microseconds. Thus even during a sharp musical transient the power supply would have time to refresh the capacitors many times.


Paul</font>