$2,000-3,000 Tower speaker comparison: Need help picking the contenders

[PENG]

At 1W, you'd hope not, although perhaps some flea watt SET models might have problems. However, a reactive load can have an impact on an amplifier. Take a quick look at the power cube result on page 35:

http://www.theaudiocritic.com/back_issues/The_Audio_Critic_29_r.pdf


Indeed; but a 90dB w/ 2.83V sensitive speaker with dips down to 2 ohms is only 84dB sensitive w/ 1 watt at those 2 ohm dips, which makes such comparisons a little more interesting. The fact that watt for watt, it is harder to drive a 2 ohm load than an 8 ohm load only adds to this.

Steve, I am well aware of that without looking at such articles, but thanks. The factor is the cosine of the phase angle, cosine 60 degree is 0.5 so if the phase angle is that large, you get a factor of 2, similar effect to halving the impedance. It is rare to have phase angle that large and when it does happen, it usually happens in a very narrow range and more likely than not to not line up with the impedance dips. So yes, if the large phase angles coincides with the impedance dips in the lower frequencies it could make that speaker power sounding not right in the hands of a weak amp but still matter much if the amp is outputting 1W. That's all I am saying.

I typically listen at 0.2 to 0.5W with occasional peaks to 1 to 2W. I have taken measurements to verify that on my Bryston and the wattmeters on my Marantz (weighs 52 lbs but rated only 2X150) tells me the same.

 

[PENG]

You know as well as I do that the difference between 100W (which AVRs regularly rate) and 400W (which would require $2000 in XPA-1 monoblocks) is 6db. 1000W (which I think starts at $10,000 unless we want to include some pro-gear) is only +10db from 100w (an AVR).

I'd think anyone here using any external amp at all would be hard pressed to say that there is no difference other than wattage.

I have my fair shares of external amps so you are right and I repeat, I don't believe they all sound the same. I just know how much more my source, example between CD, SACD, flac on USB etc., and speakers impact on sound quality, infinitely more.. okay I am exaggerating to make my point and I am comparing amps of the likes of AVR4308, Marantz MM8003, Anthem MCA20, Bryston 4B SST, and others.., that I own, none really all that powerful but enough for my needs.

Anyway, I have no intention or hope to convince you so I will sign off on this. Have fun reading that guys posts and hope you will land more power soon for your 801s to make them sound right to you. I love the sound of the 800 series, wish I had a pair of them.

 

[Steve81]

Steve, I am well aware of that without looking at such articles, but thanks. The factor is the cosine of the phase angle, cosine 60 degree is 0.5 so if the phase angle is that large, you get a factor of 2, similar effect to halving the impedance.

That's not exactly my understanding of the problem on the amplifier side, else a result like this wouldn't make much sense to me:

As you'll note, voltage output remains consistent across phase angles, even down to 1 ohm, where current limiting is obviously an issue. In the prior graph, voltage output sagged according to phase angle at the same ohm steps.

My understanding of the aforementioned equation (which could be full of BS, as I'm no electrical engineer) is that for a specified voltage output, power to the speaker will be reduced versus a load with no reactance, so you'll need to drive to a higher voltage and consequently current level to reach the same apparent power output. I'm open to ridicule if I'm full of crap.

So yes, if the large phase angles coincides with the impedance dips in the lower frequencies it could make that speaker power sounding not right in the hands of a weak amp but still matter much if the amp is outputting 1W. That's all I am saying.

I understand, and would generally agree. Just trying to point out where some failures to communicate/discrepancies between these calcs and real world listening may come into play.

 

[AcuDefTechGuy]

The 802D is 90dB/2.83V/m.

The 800D is 90.5dB/2.83V/m.

So I see the 801 being around 90dB as well.

I don't see any of the 800/801/802 needing as much power as some folks claim.

If they don't sound "right" or "great", I'm thinking it's something else like RC/EQ/DSP or placement/room, not the amp lacking power.

 

[PENG]

That's not exactly my understanding of the problem on the amplifier side, else a result like this wouldn't make much sense to me:

Sorry, not sure what you referred to. Your diagram is not clear and I wouldn't want to guess.

As you'll note, voltage output remains consistent across phase angles, even down to 1 ohm, where current limiting is obviously an issue. In the prior graph, voltage output sagged according to phase angle at the same ohm steps.

I have listed the power formula on this forum many times in the last several years, most recently in my post#57; and here it is again:

Power (in watts)= Voltage (in volts) X Current (in amps) X cos (ø)

where ø is the phase angle between the current and voltage phasors (AKA vector), and cos (ø) is AKA power factor.

One could include a distortion factor as well but for all intents and purposes, P=VI cosø is close enough.

So you can understand if ø is 60 degree, since cosø = 0.5, power in watts would be halved for the same voltage and impedance (hence current), or if you want to maintain the same watts, the current has to increase by a factor of 2 (what I said in my previous post). Also, note that impedance is not in the equation, but it's effect is represented in the formula none the less since V=IZ (Z is impedance, that includes resistance R, inductive reactance 2лfL and capacitive reactance 1/2лfC).

My understanding of the aforementioned equation (which could be full of BS, as I'm no electrical engineer)

I am, and the power formula is well know enough you don't need to be an EE to know anyway, very googleable as well as you know.

is that for a specified voltage output, power to the speaker will be reduced versus a load with no reactance, so you'll need to drive to a higher voltage and consequently current level to reach the same apparent power output. I'm open to ridicule if I'm full of crap.

Correct, more or less what I said just in different words.

I understand, and would generally agree. Just trying to point out where some failures to communicate/discrepancies between these calcs and real world listening may come into play.

Agree, but not in the case where people claim even at 1 watt there are differences between amps. Well as you know I do question that kind of claims (not saying they are always false), but unless the amps in question are not well designed/entry level ones etc., defective, or there are something else at play, including Placebo, they shouldn't have trouble outputting 1W clean and relatively at very low distortion. At higher SPL and power requirements, yes some speakers, though relatively rare, could be problematic and I have never disputed such claims.

 

[Steve81]

Sorry, not sure what you referred to. Your diagram is not clear and I wouldn't want to guess.

Just that some amplifiers can't maintain voltage output into loads of varying reactance. The amplifier's results I posted there clearly can handle a reactive load without a sag in voltage. The prior amplifier did sag in voltage output when the reactance went up. This shouldn't simply be a matter of current capability, given that the latter amplifier is getting limited into a one ohm load, but still maintains voltage across all phase angles.

very googleable as well as you know.

Googling and gaining a strong understanding don't always equate unfortunately. I've read a little bit on the topic, but not enough to claim a huge amount of understanding; just enough to be dangerous

So you can understand if ø is 60 degree, and cosø = 0.5, power in watts would be halved, or if you want to maintain the same watts, the current has to increase by a factor of 2 (what I said in my previous post).
...
Correct, more or less what I said just in different words.

I guess this is one spot where I'm getting hung up. It doesn't seem like current has to increase by a factor of two, but the root of two, since you'll have to up voltage accordingly to get double the apparent power; ie if you're running 100wpc into 4 ohms, that's 20V and 5A; to compensate for the apparent power factor: 200wpc into 4 ohms is ~28V and ~7A.

Appreciate the thoughts. PS: don't know if you want to switch to PM, since this isn't exactly on topic

 

[PENG]

I guess this is one spot where I'm getting hung up. It doesn't seem like current has to increase by a factor of two, but the root of two, since you'll have to up voltage accordingly to get double the apparent power; ie if you're running 100wpc into 4 ohms, that's 20V and 5A; to compensate for the apparent power factor: 200wpc into 4 ohms is ~28V and ~7A.

Yes, you are right about the root 2 factor, not 2 if impedance remains the same. My point was mainly on power in watts being halved if the phase angle is 60 degree. The rest of it was just meant to be a math illustration, that if V is held constant, current has to doube in that formula, remember I noted that impedance was not in that equation, but its effect was represented by V=IZ relationship. Current can double if impedance drops to half, without V increases again all just a math illustration, not intended to mean anything physical. To be honest, I do not know much about speakers so I am not clear what it really mean physically anyway.

If I stated the power forumla as Power=I² X Z X cos ø then yes I would have used the scenario you used, i.e. current would need to increase by a factor of square root 2 while Z would be held constant. I can definitely see why you got hung up on that point.

 

[PENG]

Steve, I agree the topic is not about math and electrical circuit theory. So I switched to PM.

 

[PENG]

The 802D is 90dB/2.83V/m.

The 800D is 90.5dB/2.83V/m.

So I see the 801 being around 90dB as well.

I don't see any of the 800/801/802 needing as much power as some folks claim.

If they don't sound "right" or "great", I'm thinking it's something else like RC/EQ/DSP or placement/room, not the amp lacking power.

One problem is that we (me included) sometimes use terms like "well designed amp......" but what the definition of "well" is not definitive. For sure amps can color the sound differently in audible ways if that includes every amps out there on the market, especially when you add low impedance and highly reactive loads into the mix.

 

[JerryLove]

Does anyone want to comment that, with the Focals in the linked thread we have actual measured in-room differences between two reasonably powerful amps (on extremely demanding speakers).

I've been looking at this no-longer-made parasound: and I can't help but notice that they didn't just list wattage and move on.

Current Capacity
50 amperes continuous
90 amperes peak
Slew Rate
>135 V/µsecond

Are these two things completely irrelevant to the amp? An amp with the same wattage but 1/10th those values (or 10x those values) would perform identically (or would that necessarily change wattage? At all ohms or only some?)?

Is there any reason (other than melting) that some amps *don't* double wattage every time you halve ohms? Any reason (other than melting) that they aren't all rated for 1ohm?

 

[fuzz092888]

Does anyone want to comment that, with the Focals in the linked thread we have actual measured in-room differences between two reasonably powerful amps (on extremely demanding speakers).

I've been looking at this no-longer-made parasound: and I can't help but notice that they didn't just list wattage and move on.

Current Capacity
50 amperes continuous
90 amperes peak
Slew Rate
>135 V/µsecond

Are these two things completely irrelevant to the amp? An amp with the same wattage but 1/10th those values (or 10x those values) would perform identically (or would that necessarily change wattage? At all ohms or only some?)?

Is there any reason (other than melting) that some amps *don't* double wattage every time you halve ohms? Any reason (other than melting) that they aren't all rated for 1ohm?

Here's a post recently that kind of answers that last question.
http://forums.audioholics.com/forums/912598-post4.html

 

[GranteedEV]

Does anyone want to comment that, with the Focals in the linked thread we have actual measured in-room differences between two reasonably powerful amps (on extremely demanding speakers).

Which amps are those exactly, and what kind of output design do they have?

 

[JerryLove]

Which amps are those exactly, and what kind of output design do they have?

I'd defer to the link. I believe one was an emotiva , and the other higher end (Krell, ML, etc). Both class AB.

 

[GranteedEV]

I'd defer to the link. I believe one was an emotiva , and the other higher end (Krell, ML, etc). Both class AB.

I would confirm it. The effects being shown suggest the use of an output transformer or something along those lines.

 

[PENG]

I would say continuous, peak current and slew rate are very relevant. The first one can be deduced from the continuous avg power rating if specified for given impedances.

Regarding 1 ohm rating, I suppose for example EMO could rate the XPA-2 50w into 1 ohm? Given that very few speakers on the market has such low impedance dips, manufacturers won't be making much money making high power amps with gigantic power supplies and power transistors. So that leaves a handful of them to cater for the few 1 ohm speaker owners.

Again, if you don't need a lot of power, even a XPA-1 can drive 1 ohm, just put a hard stop on the volume control or use a step down transformer. That's just for argument sake not to be taken seriously.

 

[JerryLove]

So we can compute peak current given RMS numbers?

Parasound 2250 (2-channel amp)
• 250 watts rms per channel into 8 Ω, all channels driven
• 400 watts rms per channel into 4 Ω, all channels driven
• 385 watts rms per channel into 2 Ω, all channels driven
• 700 watts rms bridged into 8 Ω or 4 Ω mono
• 45 amps peak current per channel

Parasound 2200ii (2-channel amp)
Continuous Power Output - Stereo
250 watts RMS x 2, 20 Hz-20 kHz, 8 Ω
385 watts RMS x 2, 20 Hz-20 kHz, 4 Ω
385 watts RMS x 2, 20 Hz-20 kHz, 2 Ω
Current Capacity
50 amperes continuous
90 amperes peak

Peak current in the 2200ii is double what it is in the 2250.

 

[Steve81]

Parasound 2200ii (2-channel amp)
Continuous Power Output - Stereo
250 watts RMS x 2, 20 Hz-20 kHz, 8 Ω
385 watts RMS x 2, 20 Hz-20 kHz, 4 Ω
385 watts RMS x 2, 20 Hz-20 kHz, 2 Ω
Current Capacity
50 amperes continuous
90 amperes peak

Peak current in the 2200ii is double what it is in the 2250.

I suppose I'm a little confused as to how they're arriving at 50 amperes continuous. 385 watts into 2 ohms equates to ~13.9 amps per channel. Even 25 amperes (50 amps divided into two channels) into a 2 ohm load is 1250 watts.

Some additional light reading:
http://www.audioholics.com/education/amplifier-technology/the-high-instantaneous-current-spec

 

[PENG]

So we can compute peak current given RMS numbers?

Again, given rated continuous average power into 8,4,2 ohms you can deduce the continuous rated current but not peak. I don't use the term r.m.s. for power as it is sort of a misnomer so I stick with "average power" in general.

 

[Steve81]

Slew Rate
>135 V/µsecond

Are these two things completely irrelevant to the amp?

A bit on slew rate and various other things you may find interesting.

Amplifier Sound - What Are The Influences?

 

[JerryLove]

Again, given rated continuous average power into 8,4,2 ohms you can deduce the continuous rated current but not peak. I don't use the term r.m.s. for power as it is sort of a misnomer so I stick with "average power" in general.

Why is peak current in the 2200ii double what it is in the 2250.