Class D Subwoofer?

No such thing.  A speaker is a speaker -especially a subwoofer - and anything else is marketing hype.  "Class" refers to amplifier topology.

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Hi nouse and everyone else,

I wrote an article on this very topic a few years back, it is edit to be easy enough for anyone to understand the basics of amplifer classing.

Introduction:

Amplifier classification (A,B,AB,C,D etc.) can be misleading due to the fact that manufacturers have been known to periodically invent their own classes or, as a selling point, misapply existing classes. Additionally, the subject matter is quite technical. The premise of this article is to simplify the theory and to help you to understand and define the audio amplifier classification system, which basically describes circuitry types, as well as the advantages/disadvantages of each. I will only deal with the more popular classes, as the others are not generally utilized in our industry.

Amplifiers are divided into several classes of operation which are determined by two attributes: How inherently linear (low-distortion) they are and how effectively they convert voltage into power to drive speakers (efficiency).

Modes:

The nomenclatures of the most common amplifier classes (Class A, Class A/B and Class D) do not necessarily pertain to sonic quality like a test score, in which one is better then the other. In fact, high quality amplifiers are manufactured using all modes of operation. These modes are commonly known in the field as “linear” and “switched”. Amplifiers in classes A, B, and AB operate their output transistors in “linear” mode. Class D amplifiers operate their outputs in “switch” mode.

Class Examples:

Class A: This class is the least efficient of the categories I will cover, (about 25% efficient). One advantage of a class A amplifier is that it offers very low distortion. However, its inefficiency inherently causes it to use a large amount of current, which in turn generates a large amount of heat. With this class A “linear mode” amplifier the output transistors never actually turn off and will even consume full current with no audio signal, possibly as much as with a speaker connected to it when operating at maximum power. This means that a class A amplifier will operate hot even when playing at very low volume, as well as at high levels. Because of all the heat generated, class A amplifiers require very large heat sinks on the amp casings and usually incorporate fan cooling.

Many audiophiles claim pure class A amplifiers sound better than other classes. Although at one time this may have been true, in actuality amplifiers should not produce any “sound”. They are designed to increase power only hence any quality amplifier should perform that function well enough so that even the most critical listener will have difficulty telling one design from another by ear.

Class B: There is no reason to delve into class B amplifiers since it is not generally used for audio. In a class B amplifier, there is a small part of the waveform that will be distorted. Distortion, when describing audio equipment specifications, is any unwanted variation in a signal (compared to the original signal).

Class AB: We realize that a class A amplifier is very inefficient. In most cases this is not the best choice for a car audio amplifier. (It will use excessive power and operate hot). Class B amplifiers will have too much distortion, which is not good for any audio amplifier. The class AB amplifier was designed to be a compromise. A class AB amplifier is more efficient than a class A (about 50%-60% efficient) but without the distortion of the class B.

Some car audio amplifiers that claim to be a class A amplifier are just a “high bias” class AB design. These amplifiers are only class A at very low power output levels. This is not to say that true class A amplifiers do not exist. There are a few high quality (and expensive) mobile amplifiers that are a true class A design.

Class D: Class A amplifiers are very inefficient. Class 'AB' amplifiers are also inefficient but are more efficient than class A amplifiers. Class D, also called switch mode or digital amplifiers, is the most efficient method (up to 90%) and is the least linear, unless it employs sophisticated corrective signal processing. It is predominantly used in less critical applications where fidelity is not as much of an issue but power output is, such as with dedicated subwoofer amplifiers or “mono blocks”. However, there is a new breed of digital amplifiers that use Class D (or variations thereof) for high-end applications.

Summery:

Although I did not cover some of the more technical aspects you should now at least have a basic understanding of the differences between amplifier classes. This general information can come in very handy to promote to the customer your professionalism and product knowledge. However, keep in mind that the ear of the subjective listener is the final judge of what sounds good, not the specification sheet.

Copyright © 2003 by Ron Gold. All rights reserved including reproduction in any form, whole or in part, without expressed permission of the author.*

*any or all of this info may be shared publically or privately without recourse for educational and/or non-profit purposes only.

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Anyone here heard of CLASS T amplifiers???? This amp claims to be a class T

https://www.techronics.com/index.cfm?fuseaction=product.display&Product_ID=1110

Hey aznboi..waz up?..haven't seen ya in a while.

Yeah..a class "T" amp. The T stands for Throw your money away..

lol, jus kidding, I will look into it.

I am reminded of the days of "Y2K compliant"..Remember that hooey? I think everything from wrist watches to coffee mugs had "Y2K compliant" stamped on the package..what a gimmick ,all in the name of capitalism..but you gotta love it. I think marketers are almost as bad as laywers...it's a close call.

Another sham..."Digital ready Speakers," I think I still see this one.  Unless you were a cyborg (perhaps way in the future) you wouldn't really get much enjoyment out of listening to digital information. It appears we mammals are designed to hear and enjoy analog information.

And how many times I hear installers say they can't work on a car because it has a "fiber optic antenna". I guess they don't understand that AM and FM is transmitted in analog, but, such is this world we live in..the "mis" information super highway.

Oh...and the amplifier the size of a matchbox crammed inside with the CD mechanism, the tuner and other circuits puts out a clean 35 watts x 4. That is not true BTW, but so many think that when I am trying to explain to them why they need an amp on thier mids/highs.

Have a good one and I will see about this class "T" amplifier and get back.

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Actually "Class T" is a true amplifier class. Manufactured (rather invented and licensed) by Tripath, out of San Jose, I do not actually know the differences between T and D, but there are significant differences. While it is a switch mode amplifier (Class D) at heart, it is diferent.

JVC licensed Class T from Tripath, and they truly did cram a REAL 35 X 4 into a head unit, and I might add, it sounds pretty damn good for a deck! If I am not mistaken, it uses the TAA4100A chip, and if you'll notice the 65W @ 2 ohms, saturated square wave specification, and if you'll remember back to our recent thread regarding low power blowing speakers, and the point made regarding "Crest Factor" in there, half of that is 32.5 wpc RMS. Yes, it can be done, I have heard it, and as I said, you'd be "wowed" by the overall sound of this deck.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

haemphyst got here before I did.

Was gonna post basically the same thing.

I have no hands on experience with a class t amplifier yet but hope to soon.

Seems to me it is a modified class D. The T has to do with the trademark "Tripath"

You can google "class t" and find a ton of info.

As far as that 35w rms crammed into a head unit and somehow not generating enough heat to melt the dash...well that is impressive. I have not used that particular JVC but I am a JVC dealer and like the product (no debates please, its just my opinion)

We do use a model of pioneer that you can hit a switch and do some programming and it ups to RMS power (so they claim, I can't really hear that much of a difference but it IS a nice sounding head unit)

When you program it for RMS you are supposed to cut a jumper acc wire and run it to the battery or a high current source (ie: heavy ga. @ ignition harness).

Amazing how much I learn everyday. Technology changes so fast I don't even think I should reply with advice anymore....nah, I will. Even if I am wrong it's still a learning experience.

But more than being "wrong" I really just find out something that I never even knew exisited.

Keep the info coming. Later all.

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Oh, another memory just came up. I think it was back when I was like 8 years old. I used to hangout at this high end shop near my house. I would sweep up and pass them tools etc. in exchange for being allowed to watch them.

I remember they were doing a system in some famous tennis players rolls royce corniche convertible. They were installing this system made by K-40. (yes, the same one that makes the radar detectors.)

It came with a small amp "module", 2 - 6 x 9 "subs", and 4 little mid/tweet pods.

The amplifier was so effiecient (so they clamed) that you did not need to connect at the battery, The little 18 ga. wire at the trunk light would suffice, as long as constant 12v was there.

The system operated at 1 ohm so this is a reason they claimed they were getting alot of power out of it.

I have not seen one of these since so can't vouch for the reliability.

I also remember our favorite company  BOSE (no highs, no lows) had a system you could buy for any car. It had a thin amp module you put in the glove box and it had slider controls for "spacial" and level etc. I think that was 1 ohm also, I don't remember much else about that.

At the time I didn't know what a pinswitch was. But that experience as a kid is what kept me interested in this field. I was close to changing careers a few times but am always drawn back.

I love the "controversy". Either that or getting to hack up all these cars?  It's all good.

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Whats up master...how've you been.

Well I haven't reran those wires yet as it is 35 degrees here in southern indiana lol..gotta wait till a warmer day

azn, you have the opposite problem as me. It is usually too hot where I live to work outside.

Luckily, at least for now, our shop has ac. This is a good time of year for us. Only 80 degrees and lower humidity, But it doesn't last long and always a threat of a hurricane, although this year it's been quiet so far.

I did a side job sunday and the guy gave me a brand new 300w, 150w rms sub he had in his trunk. He just got the car and didn't even know it was there. I went online and found some specs and ts parameters..perfect for my next "experiment".

I am going to hook it up on my bench in a vented enclosure to a 60w, 30w rms @4ohm kac322 tiny kenwood amp I had lying around forever. With a 100a power supply to the amp I am going to use a test tone cd, and take some output readings (current, voltage etc) and using that with ohms law and watching the sub response find a frequency that "moves" that sub.

I am going to let it run full volume with the gain also full and see what I find in the next morning.

If that woofer is toast those who stated "you can NEVER blow a sub with a small amp" will have a little explaining to do.

But I have a feeling it will be playing still (the power specs on the amp/sub are so far apart that the amp should not "theoretically" be able to toast it from what I gathered recently on the topic)) or the amp will take a dump first. Should be interesting.

I'll keep you posted. If the sub survives maybe I can try it again with a class "T" amp. lol

see ya later

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Can't wait to see the results...but i'm sure that it'll survive.

Could you post the make and model of that sub??

Class T amplifiers run at higher switching frequencies and higher efficiencies than a typical class D.  To be a class T it must use one of the patented Tripath chips.  Class T is typically cleaner and sounds more like a standard class A/B amplifier but has high efficiency like about 90%.  Another variation is called the Ice Power system developed by Bang and Olufsen, which runs at very high frequencies like 400KHz and at nearly 97% efficiency.

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Interesting DYohn. This is all new to me.

One of my best friends and drummer in my band works for B & O.

Perhaps he can get me some more info on this ice power. If so I will be glad to post.

Would you know if ALL amplifiers stating a class t circuitry are honest, or can there be variations or spec manipulation?

Also, as far as price points are these class t amps very expensive due to the "new" technology, and thier high efficiency w/ greater output? Basically I am interested to know if these are going to be strictly high end or is the main advantage in the longrun just going to be more power in a smaller package?

Any info appreciated, I am a sponge..

Thanks

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Class T is not new, it's been around for at least 10 years.  They tend to be more expensive than class D.  Ice Power is the trademarked name of the B&O technology, and it is fairly new.  I believe it's been around since about 2002, but amps (and powered speakers) using it have just started appearing in the last couple years.  Several companies are licensing the technology, but since it is newer and based on proprietary integrated circuit designs it costs more.  D, T and Ice are all variations on the same basic switching amplifier technology, but T and Ice differ significantly from typical Class D in the ways they handle the signal path and the ways they control the oscillator.  T and Ice have significantly less distortion and wider frequency response capability than D, in general, with Ice offereing the best performance.

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that's interesting

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Shaking The Neighborhood

Thanks again DYohn, man am I glad you're around,

I have been in the 12v industry longer then 10 years yet until only recently hearing of a class T. And this is after I actually researched and wrote about the amplifier classes. (in 2002 but the research began a little earlier). Am I right in thinking that the class T was primarily used in home audio and the technology has recently been introduced to car audio, perhaps that is why I never heard of it?

Although at the end of my article I do mention :

"Class D, also called switch mode or digital amplifiers, is the most efficient method (up to 90%) and is the least linear, unless it employs sophisticated corrective signal processing. It is predominantly used in less critical applications where fidelity is not as much of an issue but power output is, such as with dedicated subwoofer amplifiers or “mono blocks”. However, there is a new breed of digital amplifiers that use Class D (or variations thereof) for high-end applications."

With that said does a class T seem to be what the latter part of the quote is explaining? A variation of a class D, with the T having more to do with the trademark of the chips inventor, or is this class T recognized as a distinctive other class to  engineers and experts in the field of home audio? (other than marketers and salespeople)

In a nut shell I only ask this for a simple reason. Apparently class "T" is working it's way into car audio. If I end up down the road becoming a dealer of class T amplifiers, or amplifiers that state they are class T, do you believe I can use this as a selling point honestly on ANY amp that states it is a class T, or would it be more honest to say it is a class D with class T or "tripath" technology?

Thanks again for your time but I usually understand your explainations, rather then googling links all day and getting over 2,000,000 different answers.....lol

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Panasonic first used Class T amplification in its head units in the 2004 model year, IIRC, so it's been around a while in car audio.  Even though all switching amplifiers operate using the same basic technology, Class T is not simply the same as a "better controlled" Class D as there are several other differences including use of regulated power supplies, etc.  Also, the notion that Class D is not "good enough" to operate full range is no longer true.  Several full-range Class D solutions are available and they sound darn good.

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Thank you again DYohn,

Duly noted, I will update the article if used in the future. I originally wrote it in 02, so this was before that Panasonic exsited.  I was never a Panasonic dealer but have had some experience with thier head units. Personally, I am impressed with them.

I am constantly bombarded with new technology, it seems impossible for anyone to keep up. This forum is proving quite invaluable to me in that respect as well.

I was aware that full range Class D's are available, but I state they are "predominantly used in less critical applications where fidelity is not as much of an issue but power output is, such as with dedicated subwoofer amplifiers or “mono blocks” because in my industry (12v automotive) I see them used for mono subwoofer applications on a daily basis, and Class AB for everything else. I did not intend to imply that was thier sole purpose.

I appreciate your help.

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master5 wrote:

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I am constantly bombarded with new technology, it seems impossible for anyone to keep up. This forum is proving quite invaluable to me in that respect as well.

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I understand.  I've been working in and around audio, video and film since 1973.  I find keeping up with the changes to be one of the few things that keeps me interested in car audio!  :)

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Will do nouse, I am still new here and usually don't know what to do until someone tells me.

I think I was the one to bring up amplifier classing. Only because it was stated and most likely the case that the class D subwoofer you read about was a marketing ploy.

This is done with as well on occasion with amplifiers and a host of other electronic components.  Just wanted to clear up some confusion before it began.

Glad I did because I learned something new from it myself so I figure the more we debate, discuss and share info, the more we learn.

Ok, going to delete those old PM's

TTYL

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THIS is what came to mind when i read this post.

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Clarion DXZ665mp,Lanzar 2000D,2 Powerbase Extreme 12",Pioneer 5.25" - TS-C503
JL Audio e4300,Fosgate Power 6x9,5 Farad Cap,2 Optima Yellow,205 Amp Alt

I went there hellbass,

Marketing ploy no doubt. But I bet it will still sell.

Using thier logic I guess if I "design" a sub that can't quite handle as much heat, I should be able to market it as "The FIRST true Class AB SUB !" Digital ready AND Y2K compliant.

Hey..that really might work..lol

Thanks

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^^^ (hellbass post)  That's good, they give you a porn star in a red dress, too!

(...sorry if that's someone's sister...)   

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

I like the way she says "rugged"

Hmmmm....

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stevdart wrote:

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^^^ (hellbass post)  That's good, they give you a porn star in a red dress, too!

(...sorry if that's someone's sister...)   

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Ah, I see you've met my sister... 

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So do I call you dad or brother in law?

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Top Secret, I can tell you but then my wife will kill me.

Hey nouse,

Can you get a hold of a litlte venture capitol? I was thinking we could use chrome and bright red on the sub and market it as the first true class T sub. And a line of true class AB speakers to compliment them. Or maybe just make our own class? Class X..I like that. lol... Imagine that..speakers designed specifically to operate with an amplifier...genius !

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forbidden wrote:

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So do I call you dad or brother in law?

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Just don't call me late for dinner. 

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Alpine actually had a 5 channel "T" class amplifier up and running in a Volvo wagon at the 1999 CES show. My former install manager was in charge of Alpine's booth in the late 90's. Well on the first day amp #1 went up in a large plume of smoke. Great idea for a display, the smellof burning electronics! Amp #2 smoked the following morning. Amp #3 ( the last prototype ) met it's maker that afternoon. The car was ushered out of the booth that night. Surprisingly my former employee had a working production model that ran flawlessly for years. If I remember it was rated at 75RMS X 4, and 250 RMS X 1.  Model MRD- F752.

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There is no such thing as free installation!

An Instructor at the school I ran used to work for Alpine building thier demo vehicles. I wonder if he was at that booth during the "smoke show".

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Was that Steve Brown or Chris Yato?

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There is no such thing as free installation!

I don't want to mention names but he was Hawiian, very talented.

I was with the school from 96 to 02 . He started teaching there around 99-00 if I remember correctly. So there is a chance he was still with Alpine around the time of that show, but I can't be positive. I would think he would have told me about that, it's quite a funny story.

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master5 wrote:

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I don't want to mention names but he was Hawiian, very talented.

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I don't think either of the guys Bob mentioned is Hawaiian, so maybe you should mention a name...

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I think the video (sound off) is a more successful marketing tool than trying to call their subs "Class D".

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The Flakman
I feel strange. I have deja vu and amnesia at the same time.

John | Manteca, CA

No, it is neither of those guys Bob mentioned. I generally don't like to drop names on a public forum but, what the hay. Sean Hew-Len. I believe his job title was Installation Specialist/Product Training @ Alpine Electronics of America.

Anyone else know him?

Perhaps he is lurking somewhere around here? Sean...you there?  Still alive?? lol

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