Understanding the Speaker Impedance Specification

[Art Vandelay]

On the active vs. passive speaker discussion, my problem with active speakers is that, in my experience, the amplifiers that are used in them tend to be more unreliable than separate amplifiers.

Modern class D is getting better. The problem in the past was that the class AB amplifiers inside a speaker enclosure got pretty hot due to the lack of ventilation. Class D gets around the dissipation problem, and if HQ caps are used there's no reason why it shouldn't last for 20 years minimum.

My personal preference would be a speaker with active bass and passive mid / treble but the future is probably 100% active for the bulk of the consumer market, and really not too far away. Many audiophiles will still prefer passive speakers though and the industry will oblige them with lovely speaker cables that cost almost as much as their high end speakers.

 

[Art Vandelay]

Thank you for mentioning phase angle. Of all the parameters, I place a higher importance on phase angle and the frequency at which the phase angle is at its maximum than the absolute magnitude of the impedance as it really tells us the difficulty of the load being driven. To me the nominal impedance spec is a waste of time.

Also, the direction of the phase (-ve or +ve) will give us a clue as to whether it might induce stability problems in amplifiers that employ global negative feedback.

I actually went to the trouble of designing and building my own conjugate matching network, to flatten the impedance of my B&W 800 Diamonds. With the network connected the phase angle is within +/- 15 degrees. The amp runs much cooler at high volume levels, and the bass sounds a bit tighter and more dynamic too. My next step will be to bypass the internal woofer crossovers and drive directly from a dedicated class D amp with active XO. This will reduce the woofer distortion by as much as 10dB in the vicinity of the crossover frequency.

 

[Pyrrho]

Modern class D is getting better. The problem in the past was that the class AB amplifiers inside a speaker enclosure got pretty hot due to the lack of ventilation. Class D gets around the dissipation problem, and if HQ caps are used there's no reason why it shouldn't last for 20 years minimum.

My personal preference would be a speaker with active bass and passive mid / treble but the future is probably 100% active for the bulk of the consumer market, and really not too far away. Many audiophiles will still prefer passive speakers though and the industry will oblige them with lovely speaker cables that cost almost as much as their high end speakers.

Even so, from a reliability and ease of getting the system working standpoint, having the amplifier separate is better. With a separate amplifier, one can decide whether to repair or simply replace the amplifier, whereas with a built-in amplifier, when the amplifier is tailored to the specific speaker (otherwise, there is no point, as far as performance is concerned, for it being built-in), one is faced with either repairing it or replacing both the amplifier and the speaker, which is more expensive than just replacing an amplifier (or just a speaker, in the unlikely event that it is the speaker that fails first). With both pairs of my computer speakers that had amplifier troubles, and with one of my subwoofers that had amplifier troubles, getting the right parts turned out to be impossible. Thus, they could not be properly fixed, and so I was faced with replacing everything, instead of just a faulty amplifier.

I will never buy a speaker with a built-in amplifier whenever I can get one without it that will be fine for my application. If other people wish to buy them, that is their choice, though I would advise against it due to my experience already mentioned in this thread.

It is somewhat ironic that with my unpowered SVS CS-Ultra subwoofers and separate amplifier, it would be easy to replace the amplifier if needed, but it has not been needed. But when I have had built-in amplifiers, when it is difficult to have them replaced, that is when they have frequently failed in my case.

And, again, I know absolutely that my situation is far from rare, as many manufacturers of powered subwoofers and other powered speakers have a shorter warranty on the amplifier than on the speaker, so the manufacturer knows they are selling powered speakers with unreliable amplifiers. These manufacturers are warning you that the amplifiers are unreliable, and I strongly suggest that people heed the warning and buy something else instead, without a built-in amplifier.

 

[AcuDefTechGuy]

I think it’s kind of funny how many audiophiles defend having “separates” (separate amps from preamps and processors).

Yet the same audiophiles defend having built-in amps inside speakers and subs.

 

[Pyrrho]

I think it’s kind of funny how many audiophiles defend having “separates” (separate amps from preamps and processors).

Yet the same audiophiles defend having built-in amps inside speakers and subs.

I guess people will defend or justify whatever they happen to own.

If this is aimed at me, I think the remark is misplaced. I am not claiming an audible advantage (other than when one fails and the other still works). It is purely a question of reliability. Receivers and separate power amps and preamps and tuners are all pretty close to equally reliable. But the same is not true of powered subwoofers (and other powered speakers) versus unpowered subwoofers/speakers and separate amplifiers.

In point of fact, I have mentioned potential performance advantages to having it all built together, instead of being separate, as I prefer. But if a thing is unreliable, I don't care how much better its performance might be. I want my equipment to actually work when I turn it on, and continue to work for many years, without causing me any trouble. Although some of the powered speakers I have had have been trouble-free, the percentage of them that have been reliable has been relatively low when compared with unpowered speakers and separate amplifiers that I have owned. And this fits with the way many manufacturers put warranties on their powered speakers, with a longer warranty on the speaker than on the amplifier. You know that they do that for a reason, don't you? It is because they know that their built-in amplifiers have a high failure rate over time and they don't want to be stuck with paying for it when it fails.

 

[AcuDefTechGuy]

If this is aimed at me, I think the remark is misplaced. I am not claiming an audible advantage (other than when one fails and the other still works). It is purely a question of reliability. Receivers and separate power amps and preamps and tuners are all pretty close to equally reliable. But the same is not true of powered subwoofers (and other powered speakers) versus unpowered subwoofers/speakers and separate amplifiers.

In point of fact, I have mentioned potential performance advantages to having it all built together, instead of being separate, as I prefer. But if a thing is unreliable, I don't care how much better its performance might be. I want my equipment to actually work when I turn it on, and continue to work for many years, without causing me any trouble. Although some of the powered speakers I have had have been trouble-free, the percentage of them that have been reliable has been relatively low when compared with unpowered speakers and separate amplifiers that I have owned. And this fits with the way many manufacturers put warranties on their powered speakers, with a longer warranty on the speaker than on the amplifier. You know that they do that for a reason, don't you? It is because they know that their built-in amplifiers have a high failure rate over time and they don't want to be stuck with paying for it when it fails.

You are preaching to the choir.

No, my statement was not aimed at you at all. If it were, it would be aimed right back at me because I feel exactly the same as you.

I unequivocally think that high quality external dedicated amplifiers are a lot more reliable than amps inside speakers and subs.

I don’t see how anyone can argue with that.

I have never had a speaker malfunction, but I have had internal sub amps malfunction. So there is no way I would ever want to put any amps inside my speakers and subs.

I do think that high quality dedicated external amps are more reliable than pre-pros and AVRs. I have never had a high quality external amp malfunction.

There is a darn good reason why companies like Bryston give amps 20 YR warranty, but only give pre-pros 3 YR warranty.

There is a good reason why some companies like Aperion give subwoofers 10 YR warranty, but give the internal sub amp only 2 YR warranty.

There is a good reason why companies like Legacy Audio warranty their speakers for 7 YR, but warranty the internal amps and DSP for only 3 YR.

 

[MrBoat]

Active speakers as a standard just seems to indicate one more brick in the wall of disposable electronics. Something that would be more expensive to repair than to replace.

 

[AcuDefTechGuy]

Besides the reliability issue of complex electronics inside speakers, there are other issues.

If some people don’t like the sound of the loudspeaker, they won’t know whether to blame the speaker or the internal amp.

I mean since all amps sound differently and all.

And skinny little plate amps are just not as sexy or interesting as big bad cool solid external amps.

 

[Art Vandelay]

With a separate amplifier, one can decide whether to repair or simply replace the amplifier, whereas with a built-in amplifier, when the amplifier is tailored to the specific speaker (otherwise, there is no point, as far as performance is concerned, for it being built-in), one is faced with either repairing it or replacing both the amplifier and the speaker, which is more expensive than just replacing an amplifier.

My experience with active speakers is limited, but I know of at least one hi-fi brand that allows removal of the amplifier module for repair or replacement. For anyone wanting to buy active speakers it would be a very good move to check out the serviceability & repairs conditions offered by the manufacturer and /or distributor.

Fwiw, In the pro world, there has been a rapid trend towards active speakers in recent years.

 

[3db]

If this is aimed at me, I think the remark is misplaced. I am not claiming an audible advantage (other than when one fails and the other still works). It is purely a question of reliability. Receivers and separate power amps and preamps and tuners are all pretty close to equally reliable. But the same is not true of powered subwoofers (and other powered speakers) versus unpowered subwoofers/speakers and separate amplifiers.

It would be interesting to conduct a poll of the reliability of the electronics behind powered subs. Its not been my experience of electronic failure of powered subs. I have an old PSB Subsonic 5 sub that is still cranking today without issue.

 

[Jim84]

Actually a good speaker crossover should include a Zobel network to flatten the impedance for the woofer so
you don't see the peaks you display in your article. An impedance plot of a well designed speaker with a
Zobel network, a well designed second order or higher crossover network and a ribbon or AMT tweeter
will be nearly flat with frequency.

 

[Jim84]

A good speaker crossover will have a Zobel network to flatten the impedance curve of the woofer. The impedance curve of
a really well designed speaker will be nearly flat with frequency, especially if one uses a second order or higher crossover
and a tweeter such as AMT or ribbon with a flat impedance curve.

 

[Bucknekked]

Active speakers as a standard just seems to indicate one more brick in the wall of disposable electronics. Something that would be more expensive to repair than to replace.

I'm with you and with @AcuDefTechGuy , I think powered speakers in general would be a step down in reliability. I have had precious few failures with my stuff over the years. But, the amp in the powered sub woofer is one place where I've had 2 failures. In neither case could I make the business case to fix it work. Getting the amp from the manufacturer was either impractical or just plain too expensive to make it worthwhile.

Putting amps in speakers seems to be a thing these days. I suppose there may be reasons why its a good idea, but, to me, I'm going to stick with my passive ones as long as I can.

 

[Beave]

Actually a good speaker crossover should include a Zobel network to flatten the impedance for the woofer so
you don't see the peaks you display in your article. An impedance plot of a well designed speaker with a
Zobel network, a well designed second order or higher crossover network and a ribbon or AMT tweeter
will be nearly flat with frequency.

Please elaborate on why this is necessary and what tradeoffs are involved (benefits of adding the Zobel network versus the drawbacks of doing so).

 

[Dennis Murphy]

Please elaborate on why this is necessary and what tradeoffs are involved (benefits of adding the Zobel network versus the drawbacks of doing so).

Whether or not you opt for impedance compensation in a crossover depends on the woofer. It usually isn't necessary--computer optimization programs can compensate for rising woofer impedance by adjusting the inductor and capacitor values. However, some woofers (like the one I use in my Affordable Accuracy monitor) have such a steep increase in impedance that you're much better off adding a zobel and avoiding a very high and expensive inductor value. Either way, the final system impedance won't be thrown off by the woofer's rising impedance.

 

[Beave]

Now that makes sense to me. You might have to add a couple of components, but in doing so you avoid having to use a different, more expensive component.

But that's very different from what Jim84 wrote.

 

[AcuDefTechGuy]

I'm with you and with @AcuDefTechGuy , I think powered speakers in general would be a step down in reliability. I have had precious few failures with my stuff over the years. But, the amp in the powered sub woofer is one place where I've had 2 failures. In neither case could I make the business case to fix it work. Getting the amp from the manufacturer was either impractical or just plain too expensive to make it worthwhile.

Putting amps in speakers seems to be a thing these days. I suppose there may be reasons why its a good idea, but, to me, I'm going to stick with my passive ones as long as I can.

Yeah, MrBoat, you, and I are on the same page.

1. I don’t understand why the same people who are so against putting amps in AVRs are advocating putting amps inside speakers.

2. Increasing component parts (Amps, DSP, EQ) inside anything would only increase the risk of failure. It’s like Entropy - the Second Law of Thermodynamics.

Just common sense.

 

[PENG]

Yeah, MrBoat, you, and I are on the same page.

1. I don’t understand why the same people who are so against putting amps in AVRs are advocating putting amps inside speakers.

2. Increasing component parts (Amps, DSP, EQ) inside anything would only increase the risk of failure. It’s like Entropy - the Second Law of Thermodynamics.

Just common sense.

There is one advantage, it allows the manufacturer to minimize the BS you get on audio forums about power, voltage, current requirements such that one can no longer blame the amps instead of the speakers, source player, music source etc. No more talks of night and day improvement just by adding a $500 120 W rated amp to a mid range AVR.

 

[killdozzer]

There is one advantage, it allows the manufacturer to minimize the BS you get on audio forums about power, voltage, current requirements such that one can no longer blame the amps instead of the speakers, source player, music source etc. No more talks of night and day improvement just by adding a $500 120 W rated amp to a mid range AVR.

I only wish it was that easy. I see them “improving” on purchased products all the time. Crossovers are first to go. People on various forums always think that a company went cheap on them and that they can easily improve just with a better or “better” crossover. Even LS50 got such a treatment. Then, there’s a fool with money removing the copper wire on a capacitor to put silver. The damping material is one of the usual targets, they change that if the bass is boomy. Wire bindings (I would even change this, but only because it receives bare wire only).

I was impressed by this video, I think it’s effective:

 

[AcuDefTechGuy]

There is one advantage, it allows the manufacturer to minimize the BS you get on audio forums about power, voltage, current requirements such that one can no longer blame the amps instead of the speakers, source player, music source etc. No more talks of night and day improvement just by adding a $500 120 W rated amp to a mid range AVR.

They’ll find something else to BS.