Advice needed: potentially underpowered amplifier

[Quezac]

Hello all,

 

 

This is my first message here. I'm a beginner looking to invest in a serious 2.1 desktop setup which hopefully will last me long.

 

 

My post is about matching an amp with speakers, even though said amp looks too feeble on the paper.

 

 

After spending hours researching the subject, I've narrowed my choice down to two potential setups, including this one: Monitor Audio Radius 90 speakers + Teac AI-301DA amplifier to drive them.

 

 

For the Radius, M.A.'s website specifies: "Recommended Amplifier Requirements: 30-100 Watts" (at 8 ohms).

For the Teac, it is presented as: "Maximum output: 30W + 30W (8 ohms, 20Hz to 20kHz, JEITA)"; "Rated output: 22W + 22W (8 ohms, 20Hz to 20kHz, THD 0.1%, JEITA)". (Cached page)

... though weirdly, on another Teac website, the effective output is rated at 20W + 20W (8 ohms, 1kHz, THD 10%, JEITA) or 15W + 15W (8 ohms, 1kHz, THD 1%, JEITA).

 

 

The specs of the amplifier and speakers somehow match if I consider the max output, but my question is: does "maximum output" here mean peak output which can't be sustained for long times?

Because I find it weird that such an amplifier wouldn't able to drive two relatively simple bookshelf speakers with ease... What do you think?

 

 

Additionally, I stumbled upon this review which said about the Radius:

Quoted sensitivity is a poor 83dB, so be aware that you’ll need a punchy solid-state amplifier, putting out at least 40W RMS per channel if you’re going to want to be able to produce realistic volume levels.

I'm not sure what the reviewer meant by "realistic" and what an underpowered amp would mean in this case.

My own reality, though, is that my tolerance to sound is much lower than average people (but I need good quality sound); so if using an underpowered amp up to, say, 55dB maximum won't cause any damage (clipping?) to speakers... then it's fine by me.

 

 

So do you folks think such a setup would work for me, that it wouldn't cause any issue in the long term for someone who will never listen to music at loud levels?

Or is this a wrong setup, and I need either a more powerful amp or less demanding speakers?

 

 

My alternative (and quite cheaper) setup is the Monitor Audio Radius 45 speakers + Teac AI-101DA amplifier.

The AI-101's rated output is 20W @ 4 ohms, so I guess at the 8 ohms required by the speakers, it would be around half of that value, so 10W... whilst the Radius 45 are rated for 15-50W amps. Eh. Same issue I guess.

 

 

Thank you for the explanations or suggestions you could provide me with!

 

 

 

 

(Background, for those wondering why I went with the above prospective setups):

 

 

I have high space constraints and don't want to gamble anymore (my Logitech kit died some time ago, as did a second-hand Creative setup before that), so I left out lauded bargains from Pioneer, Micca, JBL, etc. for the speakers and Topping, SMSL, etc. for the amps (too bad because their diminutive form factor is exactly what I wanted).

 

 

Loudness, on the other hand, is not a preoccupation. I will never listen to music at loud levels - always at relatively low ones. Bass are appreciated but not critical.

 

 

I'm looking for a small footprint amp, with power button and volume control both on the façade. DAC is optional.

[wgscott]

First: Welcome!

 

Have you considered other options like powered USB speakers? Vanatoo and Audioengine are both worth having a look at (and there are several others).

 

The advantage is that the manufacturer has taken care of the amp matching problem for you. (BTW, Little speakers tend to be fairly inefficient and therefore sometimes require more power than very large ones.) If that isn't enough of a paradox for you, in my experience, having a more powerful amp helps the most when listening at a quiet low volume.

[Quezac]

Thank you for welcoming me, Scott

 

 

Yes, I forgot to mention it: I initially looked at Audioengine's A2+, as they seemed small, neat and quite feature-packed. What turned me off was the power and volume buttons both located on the back. Since I'll be using my computer as a source, I could deal with the practical absence of volume button.

But I do prefer to have a readily access to the power button, so that I can cut the power (in addition to muting the volume) and better avoid "accidents"... sensitive hearing again.

 

The A2+ have an auto sleep mode feature but this isn't completely powering off, and AFAIK this also means auto-power-on, thus not so safe for my necessary paranoia. I'm also unsure about how long it takes to auto-power-on, I've read it's 30 seconds for the Kef X300A... too long for my taste, I'm a rather impatient one.

 

The Vanatoo Transparent One's controls are also all on the back; and a small detail: they aren't available outside of the USA.

Their quality looks really impressive though, as even Noaudiophile raved about them.

 

There's also the Emotiva Airmotiv 3B, which are small and sport controls on top of the right speaker. Their price is sweet. But the power button seems to perform On and Standby only, no real Off; they're less easy to source (and return or RMA) and their design is less appealing.

 

So well... I've ruled out all these speakers as of now, but in the back of my mind I know how appealing their "plug & play" philosophy is.

 

I am also taking good note of your tips regarding using more powerful amps than required on little speakers, cheers.

[maelob]

The new Audioengine HD6 have remote control and volume on the front plus DAC and sub out.

[esldude]

I don't believe either of your choices will work well. How about thinking about one of the Teac DAC preamps feeding some powered speakers. The preamp DAC will have volume control on the front panel. In essence no different than a power amp and passive speakers. Other than appearance it would fill all of your needs.

[anwaypasible]

the radius 90's are rated at 83dB with 1 watt of power from a distance of 1 meter.

the amplifier's 1khz distortion at 1 watt is 0.01%

turn the amp up for 15 watts and you are at 1% distortion

 

they say you need double the power for a 3dB increase.

2 watts gets you 86dB

that's right at reference listening levels.

 

so lets do some math to guesstimate the harmonic distortion percentage at 2 watts.

at 2 watts you should be getting something like 0.0225% - 0.0766% distortion.

 

if the amplifier puts out what it says it can, you might of found yourself with an amplifier that is lower than like 90% of other people (at the lowest percentage).

at the highest percentage, my amplifier does 0.7% distortion at 1khz 100 watts rms.

my amplifier is also about 13 years old.

i kinda wish i knew your amps 20hz - 20khz percentage to compare with my 0.09% 100 watt rms 8 ohms.

 

now lets consider something,

i know my speakers aren't less than 83dB of sensitivity.

in fact, my midranges are a little higher as i went and looked.

they've got an rms of 60 watts.

 

i've got them on a 100 watt rms amplifier and i need to turn it up more than halfway using a digital signal that is about -6dB rms.

 

how am i supposed to recommend the setup you want without doubt?

the website says a single speaker handles 75 watts rms.

the website says the speakers as a pair handle 100 watts rms (why there's two different values, i don't know).

but either way, you aren't far off from my midranges on 100 watts.

my calibration hasn't significantly turned down my midranges.

 

there's a chance that amplifier won't let those speakers play loud at all.

the website for the speakers said at least 30 watts and here i am trying to use math on paper with 2 watts.

2 watts is 6.66% of 30 watts !

meaning you are kinda under their recommended lowest power by 93%

 

i guess the question is, do you trust they got 83dB out of the speaker using only 1 watt from a distance of 1 meter?

or

do you trust my setup that has a slightly higher dB rating using only 1 watt from a distance of 1 meter as i'm telling you the rms levels are about the same and i'm using a 100 watt amplifier at over 50% volume to get lower than the reference 85dB from 5-6ft away from the speakers?

 

my amplifier's 1 watt output is different than the teac's 1 watt output?

well my amplifier uses 265 watts from the wall.

try to be fair and split that number up for the number of speaker pairs?

okay i still get 88.3 watts , while the teac amp is only 38 watts.

 

two important things to note:

1. In terms of electromagnetism, one watt is the rate at which work is done when one ampere (A) of current flows through an electrical potential difference of one volt (V).

2. When an object's velocity is held constant at one meter per second against constant opposing force of one newton the rate at which work is done is 1 watt.

 

notice how in number 2 the words 'one meter' and '1 watt' exist.

look for the return policy & any restocking fees.

[Quezac]

Thank you all for your additional comments and calculations.

 

 

The usability issue I see with preamps is that there is no way to turn off the speakers. Although at least it'd be possible to turn off the pre-amp that feeds them sound.

The Audioengine HD6 with a remote control could be a workaround; but they seem a bit large. I've read comments on forums about upcoming HD3, however I couldn't find the source of these rumours.

 

 

Browsing review websites, I stumbled on the Temple Audio Bentam Gold (25W @ 4 ohms ; 190GBP) and the Ampstatic Mini-1 (< 20W @ 4 ohms ; 100GBP) amplifiers. With their size and design, they almost fit the bill - if not for their limited power, they'd seem very good for my intended use.

 

 

Yet, something puzzles me.

 

 

The Hifipig review of an earlier Amptastic Mini-T reads:

20wpc, the spec says, but that’s way optimistic in real world terms. I’ve heard that it measures at 10wpc into 8 ohms.

But it drives my 83dB/W MBL speakers with no problem as long as you don’t want to flex the walls, although the MBLs are quite an easy load impedance-wise.

 

 

The writer further commented:

It doesn’t always fare well with difficult speaker loads, or so I’ve found, but I’ve had reports that it works fine with most speakers.

 

 

In a later article, he said of it:

In fact, I still use it as the amplification for a second system, powering a pair of very nice Usher X-719 standmount speakers. A £60 amp powering a £1400 pair of speakers. Loopy stuff! But it works for me.

 

 

Then, about the Mini-1, its successor, the reviewer explained:

But you would likely be very surprised with what that 10wpc can do! – it certainly drives my 84dB/W 4-way speakers to all but truly insane levels on seriously challenging full-range material (...). But my MBLs, large and full-range though they are, are quite an easy load and maybe the Mini-1 would run out of puff into a more challenging speaker? (...) It is equally unconstrained on my Usher X719 speakers.

 

 

you’d require an industrial strength crowbar to part me from my MBL speakers and they work well with the Mini-1

 

 

The MBL 116F he refers to are these ones:

 

 

What gives?

 

 

I don't want to ignore the arguments you have given me earlier, but at the same time, it does seem like a lot of people are using these kinds of feeble amps to drive powerful speakers; with good results in the long term. Users reported using the Mini-1 with Wharfedale Super Diamonds and Acoustic Energy Aegis Evo 3, the Mini-T with Diapason Emeras, etc. One founder of Amptastic said a Mini-T would work fine with Q2010i or Q2020 speakers and implied what mattered most was the sensitivity of the speakers ("90db or above").

 

 

So whilst I find the rating of similar Chinese amps up to 50wpc quite dubious, it appears possible from real world usage that such diminutive amps are competent for driving bigger stuff.

 

 

This user on AV Forums reported having compared the earlier Mini-T to a much older yet much more powerful amplifier, the Quad 405-2 capable of outputting 100W @ 8 ohms, and declared that "no audible difference whatsoever was detected, provided that the 17 V(peak to peak) limit set by the Mini-T amplifier was not exceeded."

[anwaypasible]

it was said the small amplifier has a 6 v rms limit, and the other amplifier was simply set to 6 v rms too.

there shouldn't be any difference in dB when the same speaker is getting the same voltage.

 

100 watts 8 ohms is 28 volts.

 

if you are using speakers that allow higher watts, then the magnet isn't going to be super strong.

the only way low powered speakers can play loud like the big speakers is if the magnet is a magnitude stronger.

 

2 watts 8 ohms is 4 volts.

[anwaypasible]

how do you know the lowest power rating is meant for satisfying listening?

what if the speaker requires that much power to move the cone enough to hear if the speaker is blown or not?

(because sometimes the speaker is blown and no audio comes out, but sometimes the speaker plays audio with crackles before going out entirely).

 

say the power rating is for listening.

how do you know the satisfaction is for the almost 60dB noise floor that is common or a 30dB noise floor?

 

far too many hints that a low power amplifier is not the ideal choice for me.

the whole point of audio is to hear it..

i'd rather rest assured there is maybe more than i need, rather than gamble a situation where there isn't enough.

 

the speaker cone grips the air.

the more the speaker cone moves, the more details go into the air.

those details will travel further, such as another room or down the hallway, but there will also be more precise details near the speaker.

that is always true unless the speaker moves and causes a shockwave.

that is why people turn up the volume when their favorite song comes on, because more details draw out.

[DigiPete]

Active studio monitors are the professional and serious solution to your needs.

They are target at the music business and television and film business.

Active means that they have a build in amp for each speaker driver, the best way to ensure optimum fit and thus maximum clarity.

 

I'm a fan of Genelec, they have a line that offers the advantages of pro equipment but is targeted at home use.

Consider the G One's with a F One sub:

 

 

 

 

 

Genelecs come with 5 year warranty, overload protection and DIP controlled tone control to adapt monitors to how you place them:

 

 

 

Combine with a Genelec stereo volume controller, if your source has no volume control.

[Quezac]

Thank you both for your additional inputs.

 

Indeed anwaypasible, the caveat is that we don't know upon which criterion the recommended power rating was decided. So I guess if one intends to listen at low levels, using a small amplifier should work.

 

 

The main issue with the speakers you recommend DigiPete, aside from their unconventional design, is that their power button is located in their back. Their diminutive size is a good point, though.

[DigiPete]

The main issue with the speakers you recommend DigiPete, aside from their unconventional design, is that their power button is located in their back. Their diminutive size is a good point, though.

 

 

Intelligent Signal Sensing (ISS™) for power consumption reduction in stand-by mode gives the G and F models the ability to switch on and off automatically depending if there is any input. Read about ISS™ here.

 

The unconventional design should be standard on all decent speakers and monitors.

Hard corners are enemies of good sound as they break up the sound wave and cause refraction.

Ie. sharp corners work as secondary sound emitters mudding up the sound.

[esldude]

http://www.sengpielaudio.com/Mathew-AudioPrecisionSpecifications.pdf

 

Read the above if you want to learn about some of the foibles of specifications.

 

If it is in your budget, the Genelec's suggested by Digitpete are an excellent choice.

 

I am not sure I understand the importance you place on having the power buttons on the front. Many new powered speakers use class D amps which draw very little power when not actively in use. So if it is a matter of accidentally sending loud sounds thru the system a pre-amp gives you as good a device to stop that. Further you could connect the power cords of powered speakers to a good power strip at the edge or on the floor beside your desktop. One switch can instantly kill the speakers or be used to turn them on or off.

 

If it is a serious desktop system, one place you don't want to compromise for is power. Powered speakers take that out of your hands to match up. If you go with a separate amp, don't skimp on the power available just for size. Using a small footprint DAC pre-amp and placing a power amp out of sight would be a better idea.

[bluesman]

There's also the Emotiva Airmotiv 3B, which are small and sport controls on top of the right speaker. Their price is sweet. But the power button seems to perform On and Standby only, no real Off; they're less easy to source (and return or RMA) and their design is less appealing.

The Airmotivs sound great and offer tremendous value. Emotiva is a wonderful company in my experience (4 pieces of electronics purchased, one returned without a hassle, plus rack mounts and other accessories) - I couldn't have asked for better customer service. I don't understand your reservation about the power switch - what difference does it make whether they call the position in which no sound is emitted "off" or "standby"?

[Ajax]

QUOTE "I'm a beginner looking to invest in a serious 2.1 desktop setup which hopefully will last me long time (sic)".

 

Based on your aim I feel the advice given above to invest in active (or powered speakers) is putting you on the right track, particularly for a desktop system where space is a premium and you want to be as minimalist as possible. It also eliminates the problem of amp matching that has so consumed and confused your decision making.

 

The Adam range of active study monitors have a volume control, and on off switch, on the front of each speaker which alleviates that issue for you. I have had a pair of Adam A7 speakers for 5 years and have been very happy with them, you will find them for under $1k on eBay (used). They have been upgraded to the 7X, which are about $1,400. You will not need a sub in a room less than 10' x 20'. Depends on you budget but you did say "serious" sound was important so you may need to pay for it.

 

If this is outside your budget you could minimise your overall cost by running a simple $200 USB DAC into them like the Audioquest Dragonfly v1.2, Explorer 2 or iFi Nano initially and then upgrade the DAC later when you can afford it.

 

Depending on base requirements you could also check out their little brothers the Adam A5X, which can be had new for around $1k, just add a sub, but only after you have them in place at home, as it may not be required.

 

Also read up on the advantages of active vs powered speakers, active means individual amps per speaker (tweeter and woofer) AFTER the across over and IMO produce a much higher quality sound over all frequencies. From Wikipedia "Active speakers may have greater fidelity, less intermodulation distortion (IMD), higher dynamic range and greater output sound pressure level (SPL) with fewer blown drivers".

 

There are many alternatives in active speakers and at the end of the day you need to go and listen, only so much you can tell from measurements, but IMO the active monitor is the way to go for a desktop.

 

All the best,

 

 

Ajax

 

 

 

Check out there range at Homepage | ADAM Audio GmbH

[Quezac]

Thank you all for your further comments and recommendations.

 

 

Looking at the scarce availability of really diminutive bookshelves, and stumbling upon the Adam Artist 6 after Ajax pointed to this brand, I figured I might also consider small & thing floorstanding speakers which I'd put right next to my desk.

 

 

I'll have to scan the market again, but for the moment I've spotted the Adam Artist 6 (amplified and the smallest), the System Audio Saxo 30 and XP30, the Monitor Audio Radius 270.

I would have to deal with the lack of front power button, which wouldn't easily be accessible anyway given they're floorstandings. Instead I'd have to resort using a pre-amp as a "soft power off" button, as was suggested earlier.