Has anyone ever tried using a 2ohm amplifier on the factory Bose speakers to upgrade the stereo system? Just wondering. I've been intrigued by the idea of putting the Seicane head unit in my car. I was preparing to face the music in changing all the speakers and amplification system in doing this. Well, going through some stuff the other day in the spare room I came across my old Directed Audio 350 watt A/B class amplifier. It's an audiophile type of piece I used to run in my Pontiac. Looking at the specs, it is a 5 channel 2 ohm amp!! It'll do 50 watts into the fronts and rears and 150 to the sub at 2 ohms. This is class A/B wattage also, which is way cleaner than class D watts of today. This amp could run the whole thing by just changing the fiber optics cables to regular ole speaker wire. Just a thought.. I may try this soon.

 

There are man amps that support 2ohm loads now. The main problem seems to be that the Bose amp also does some digital signal processing to tune the sounds to match there speakers in that car's environment. Most people who remove the Bose DSP function have reported being very unhappy with the results. Most will say that replacing the speakers helped.

 

Yeah, but I wonder if it being a class A or A/B vs a class D amp matters? All class D amps use a pulse modulated wave form so where A and A/B class amps are pure analog making a lot more and cleaner sound out of much less power. I could see how overpowering speakers made for a low power A or A/B class analog amp would sound like crap using a higher powered D class amp. Just have to try it out and post results I suppose.

I have a 120 watt A/B class amp in my boat powering 2 Pioneer three-way 6x9’s. People are blown away that it’s only two speakers with no subwoofer.

 

I believe you can quickly disabuse yourself of any notion that a class-D amplifier sounds different from the classes you mention with a simple test.

MP3 players and cell phones all have class-D amplification. The headphone output of any home audio component is surely either class A or AB.

Use the best-sounding headphones you have available to compare the sound of a CD-based MP3 on a home component to the same MP3 on a phone or MP3 player. I'm confident you will discern no difference. In the case that you think you do, repeat the test with the aid of someone who switches for you the signal source without telling you which you are listening to. Such a "blind test" will eliminate the influence of preconceived notions you may have.

I presume anyone who discards a working Bose amplifier is a lay person who does not understand audio technology. The point Rodney makes in his post can not be overstated, in my opinion.

Doubtless the Bose speakers benefit from being part of a custom design. I presume Bose knew precisely the enclosure in which each speaker would be mounted, and this afforded them the luxury of designing the mechanical and electrical properties of each speaker to match. I can't imagine any aftermarket speaker improving upon the Bose unless it is exotic in some way.

Further, as I may have written in a recent post, perception of audio sound quality is extraordinarily subjective.

Years ago a friend and I compared the sound of our '80s-vintage speaker systems. My Infinity RS-I system was regarded by one critic as the 2nd best speaker he had ever heard being exceeded only by Infinity's top-of-the-line model, the Infinity Reference System (IRS) costing $50,000. My friend thought his Bose 601s sounded much, much better, though I believe the audio high end back in the day regarded them as a "mid-fi" product that no serious audiophile would consider.

As an aside, RS-Is come along on eBay every so often and sell for about $2500. The Infinity IRS is essentially impossible to find, though an incarnation of it can be bought new for c. $175,000.

 

I was waiting on Bobterry to chime in - he offers good advice about the quality of sound. Since my hearing has gone to crap, nothings sounds that great to me. I probably couldn't tell the difference between a cheap Walmart radio and a $50,000 professional sound system. But, I have always found the sound quality of the Bose and H-K systems in my MBZ vehicles to be just fine. The challenge for me is in getting modern features that I want, like hands-free calling, streaming, Sirius, updated maps, etc.

 

I'm sure at headphone wattage there will be no discernible difference. What I'm saying is that Bose makes really great sound with very low wattage. Pulse width modulated amplification uses more power to get the same quality sound reproduction. Not saying class D amplification is bad, It's a differnt animal and I just don't think that is what Bose uses, which is why people have bad luck getting the stock speakers to sound good. To get great sound at low power levels, class A and A/B amplifiers do a better job,

As for why someone would pull a perfectly good working Bose amp?? That's easy. You can't run the factory amp/speaker setup with an updated head unit in the fiber optic cars, period. If you want navigation, bluetooth connectivity with a touch screen DVD player, the Bose amp has to go. Most people swap speakers also. I'm gonna try my little A/B class 2ohm amp on the factory speakers and see what happens.Second pic, it's fully tunable

 

On a side note, I was in Fry's Electronics today and they had the latest and greatest in the Bose home theater 5.1 setup on display and man did it sound AWESOME!

 

If ever you are in the Atlanta area I invite you to bring some of your favorite music and listen to it on a quality home audio system. I think you will find that properly reproduced music can take you away to another place where you imagine you are hearing live musicians and not listening to electronics.

I really wonder how you could believe this, since the exact opposite is true.

In school I studied amplifier and loudspeaker design under the legendary Dr. W. M. Leach. I have hands-on experience designing and building simple amplifiers. So, much of what you write on this thread is counter-intuitive to me.

I've presumed you are a lay person who knows not of what he writes. If I am mistaken, then I sincerely apologize, and I need to take you seriously and learn from you.

As an aside, I wonder how people reading this have any idea what a "class-D" amp even is. Curiously, I didn't know what one was when long ago I walked in the doors of Infinity Systems for a job interview in Los Angeles, and yet it was help designing their first class-D car amplifier that they had specifically called me for.

 

Here's all I know. All amplifiers convert energy into either heat or sound, one of the two. Class A amps keep the circutry loaded at all time, so a 200 watt amp is converting 200 watts of energy to heat when no sound is being produced. At it's highest level, a class A amp convert all energy to sound with little to no waste. Class A/B amps reduce power when no sound is being, but circuits stay loaded using say 10% of power at all times, give or take. So a 200 watt amp is still pulling 20 watts when it's silent creating less heat, but the circuits are staying loaded. During sound reproduction, energy is increased and coverted to sound with again, close to 100 percent of consumed power going to sound reproduction at it's highest level with little to no waste. A class D amp switches off when not in use producing no heat. The incoming signal is converted to digital (using energy), turned into a pulse and modulated by the pulse width. The pulse width get wider as volume increases and narrower as it decreases. Those pulses that happen at 100k to 200k times per second. The up and down transitions of these pulses are energy creating noise in the signal that must be eliminated with a low pass filter thus raising impedence and consuming more energy in the process. It's a complicated process but there's nothing wrong with it using the correct sound producing components. I just think Bose avoided all this. I have seen zero specs on the Bose amp in the 2003 and 2004 R230's other than 50 watts for 4 channels, the 5th channel (subwoofer) is a mystery. I think for that low of a power output to sound so great with the volume it produces at 2ohms of impedence, an A or A/B is the best way to do it and that's just my amateur opinion. You'll need more power at a higher impedence to get that quality and volume with an amp containing digital circuitry. Sure a 200 watt class D amp can get as loud with low watt speakers, but it'll sound like doo doo in comparison to the Bose. And yes, Bose has signal wave length and sound reflection down to a science which helps even further. How else do you get a 6" x 8" subwoofer to thump the way as SL500 does? I could be wrong, but I believe the Bose p

I'll be ordering my Seicane head unit on the 15th with a roll of speaker wire. I'll post results. Worst thing that will happen? I doesn't work and I swap speakers. I have feeling I may be pleanantly surprised. The science says maybe.. LOL You are correct sir, I am no sound expert, but I do enjoy that science of anything. This is just a science experiment with a real world application that wil result in our SL500 having Bluetooth connectivity and GPS.

Work calls... I gotta run. Have a great weekend everyone!

 

The music/electrical voltage signal to a loudspeaker is AC -- that is, the voltage alternates between positive and negative with respect to the chassis ground. In most modern amplifiers one set of transistors conducts current during the positive phase of the music signal, and another set conducts current during the negative. The on/off state of the transistors not supplying current to the speakers specifies the class of operation in which the amplifier is operating.

In class-A operation, no output transistor ever switches off. To realize this, typically the current the amplifier would deliver under full power must also flow as a "bias" or idle current when there is no music signal present at all.

This is only partially true. Suppose your hypothetical amplifier is rated 200 watts into an 8-ohm load. By Ohm's Law and the implications of class-A operation, the bias current needs to be at least 5 amps, and the voltage of the amplifier power supply rails must be +40 VDC and -40 VDC. (When delivering 200 watts to an 8-ohm load, the voltage at the speaker is 40 volts and the current is 5 amps). By Ohm's Law the hypothetical amplifier must dissipate internally at least 400 watts of power in its output transistors. I believe if you google "class-A efficiency" you will find the theoretical maximum is 50%, and that comports with the example just given (200/400).

This would only be true if the amplifier were somehow delivering direct current to the speaker and not amplifying music. As we saw above, class A is very inefficient.

Your characterization of the low-pass filter is completely inaccurate.

It's common for all classes of transistor amplifiers to have a low-pass filter on their outputs. At audio frequencies which are to be passed to the loudspeakers the filter has negligible impedance. At high frequencies the filter components do have significant impedance which can be high, and they do indeed dissipate power. But it is reactive power -- not real power. That is a critical distinction which I won't elaborate upon here other than to say reactive power consumes no energy and generates no heat.
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This post is long enough. I'll continue later.

 

OK, send me your address! I have my Mille Vanilla cassettes packed and I should be there in a couple of hours! Seriously, My daughter was living in Kennessaw last year so I was over there all the time. Next time I head that way, I'll ping you - I'd to buy you your favorite beverage (coffee, beer, whisky, whatever) as say thanks for your contributions int he forums. And hearing your sounds system would be a treat, too, even with my crappy hearing.

 

Fundamentally, before you plan to replace the Bose you really ought to know how many audio power channels exist. There are seven, not five: The rear pair of speakers share a channel, and the other six speakers each have a dedicated channel. Also, critically, you must realize there are no external crossover networks -- distributing the audio frequency range to the speakers is done in the Bose amplifier. If you don't add a high-pass filter or otherwise limit frequencies to the door tweeters your replacement amp may ruin them.

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Quote:

Originally Posted by Blazeracer

...Bose has signal wave length and sound reflection down to a science which helps even further. How else do you get a 6" x 8" subwoofer to thump the way as SL500 does?

I've never even seen the subwoofer in my car, but I have a guess at how it works so well.

A woofer radiates sound pressure waves to both its front and rear. If these waves were to meet they would tend to cancel each other. Consequently, woofers are typically mounted in an enclosure which allows only the front sound wave to propagate through the air. But it's my guess Bose designed an enclosure which somehow permits the rear wave to propagate and do so more or less in phase with the front. Since the front wave is reinforced by the rear, efficiency is enhanced.

If you are able to overcome the technical challenges necessary to make your new audio system simply work, you will most likely be delighted with the results. You'll report back here that there is an improvement in sound, though the truth may be that you have significantly degraded the sound without even realizing it. It's psychoacuostics. An explanation will follow in a later reply.

 

When it comes to auditioning different music systems, time elapsing between those auditions and psychoacoustics cause humans to be notoriously bad at making accurate comparisons unless differences are major. A description of two thought experiments illustrates.

Suppose we play your favorite song on an audio system. Then as an experiment for the next 30 days we play that song again on the system with the understanding that on half the days the quality of the sound will secretly be degraded in some small, material way. Asked to identify the "better" days from the "lesser", you simply won't be able to do so accurately because the brain can not adequately remember how the system sounds from day to day.

Now imagine we play your song on a system powered by a class-D amplifier. I immediately substitute a similar amplifier which I tell you is class A; however, I am lying, and this 2nd amp is in fact a class-D amp identical to the first. We play your song again, and asked to compare, you most assuredly will state the "class A" amplifier sounded better, though of course the sound did not change. That would be a consequence of psychoacoustics and your preconceived notion of a class A amplifier sounding better than a class D.