07/17/2018

AudioMixer

Sound in the car: we pick up an amplifier – powerful, but accurate – part 1

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OEM car audio systems are a real headache for those who are used to quality sound. I have already told about possible ways to upgrade them, today I will focus on one of the elements – car amplifiers. Their specifics are sometimes very different from home.

What’s wrong with a regular amp?

I guess it would be wrong to skip that question. There are several reasons to change a regular amplifier.

First, output power. In this case, it is not needed at all for the volume, or, strictly speaking, not only for her. OEM systems most often use very simple amplifiers and speakers with low impedance. If we are going to build a new system, it’s not a fact that the new speakers from the regular amplifier will sound good. They may have, for example, higher impedance, lower sensitivity, and with them we’re very likely to get the hell out of it. The exceptions are the acoustics, which are initially positioned by the manufacturers to upgrade “trousers”, but we seem to have swung for more serious improvements, and this option has already left behind.

Secondly, because the systems are designed for sufficiently stringent requirements – both price and constructive. If you openly announce what, suppose, audio components for Honda are made by Pioneer and Alpine, it could hit the reputation of these brands.

Third, equipment. The regular amplifier is designed for one single system variant and has zero tens of pins as far as additional settings are concerned. What if we need to switch on FMF in the front or rear channels? What if you need to tune the LFL in the subwoofer channels to dock it to the speakers? What if there are more serious intentions?

So, it all turns out that when you upgrade your system, the simple replacement of the speakers does not always roll, and the new amplifier becomes in the discharge.

Where do I start to find the right amplifier? As always, the choice should be based on need. In other words, first we design the composition of the system, and on it you can already see what the amplifier should be. The easiest thing to do is to take a piece of paper and draw where you want the speakers installed.

Determine the type of loudspeaker connection – through passive crossovers or channels with active strip division. Both options have their advantages and disadvantages, but this is the subject of a separate conversation. For now, I will only note that the first option is simpler, and the second one has more options for setting up and “taking note” of the stripes. Depending on the selected option, we will select amplifiers with the required number of channels and functionality.

Already at this stage, evaluate what will be the source in the system. If the head unit has conventional line outputs, there are no problems. If you’re dealing with a regular “head”, you almost always have to look for detour maneuvers. I have already covered this topic in more detail in the article “Sound in the car: how to make the OEM sound better”, now I will only note that as far as connecting amplifiers is concerned.

So, there are several options. The easiest way is to connect directly to the outputs of a standard amplifier. To do this, the new amplifier must have high level inputs in addition to the normal inputs. If they do not exist, so-called “high level to linear converters” can be used.

This option is simple, but not always applicable. More often than not, an on-board amplifier produces a corrected signal at best, and at worst, it has to deal with multi-band amplification at all. In this case, only a specialized processor can “collect” the original signal and then connect the amplifier to it. Also included are the versions of standard systems with MOST bus, from which a special adapter can “pull out” the SPDIF or analog signal.

As more and more such complex systems become available, it is not surprising that amplifiers with an already integrated processor have started to appear on the market. But about the equipment a little further.

How do car amps differ from home amps?

In fact, the amplifying part itself is nothing. Except that the power supply here is not powered by domestic 220 volts, but by the on-board 12 volt network. There are, in my opinion, two principal differences.

Firstly, most car amplifiers are universal in terms of connection: they provide both a normal load connection and a bridge to a pair of channels. This feature allows you to use conventional wideband amplifiers not only for connecting speakers, but also for connecting subwoofers. The latter are still more “voracious” in terms of power. The simplest version, which can rightfully be called a classic one, is a 4-channel amplifier, the two channels of which operate on the front speaker, and the two remaining channels are connected by a bridge to the subwoofer.

The second fundamental difference between car amplifiers and home amplifiers is their equipment. Homemakers are mostly clean “tiptoes.” In a car, at least you have to use filters.

For example, it’s still the same simple four-channel circuit with the front speaker and subwoofer connected to it. In most cases the acoustic design for the front woofer/midrange driver is implemented in the doors. Let’s face it, it’s not the best, which means it’s desirable to weaken the bass, and these channels need FWH. The subwoofer, on the other hand, shouldn’t be singing in a voice, which means that these channels need a VHS. The optimal frequency of a speaker/subwoofer connection is usually between 50 Hz and 100 Hz – just below what is commonly shared in home systems. Passive division won’t work here, roll coils the size of a spare wheel – no, fire me. But the active division is the same. Historically, therefore, the minimum equipment for an amplifier has been the active bass and treble filters. Mostly adjustable, but are also found with a fixed frequency setting.

And then there’s more. For example, if an active fission loudspeaker is assumed to be channeled, the amplifier should have filters with wider adjustment limits. Some old-school models even have steep filter cutoff switches. Let’s say JL Audio used to do this kind of thing in his day. And so on ascending, up to equipping the amplifier with an integrated processor and turning it into a real “sound combine”.

A song about harvesters, or Amplifier plus Processor

Now this class of amplifiers with built-in processors (or processors with built-in amplifiers that are closer to them) can be considered the most promising for a number of reasons.

First of all, if in your home system you can get comfortable at the best point for listening, in the car you always deal with the disgusting acoustic conditions of the interior and the hell knows how the speakers are spread over it. “Gathering” sounds from all this mess is oh, how hard. And no matter how disdainful the audiophile snobs and connoisseurs of pure passive may be, it can only be done with the help of a sound processor. If you approach the matter wisely, the result may surprise even the most spoilt “home sound” audiophiles. Checked repeatedly.

Secondly, in most cases only with the CPU you can build a system based on an in-house head unit. There are a lot of cars where you can’t get the original signal out of the standard “head” by any means – it’s either corrected or cut into frequency bands at all.

As a visual example – Italian concern Elettromedia which for a long time and successfully enough develops a theme of construction of new systems from regular head units. The essence of processors produced under the Audison brand is as follows. You turn off the OEM speakers and start the signal from the OEM amplifier to the processor inputs. This is how you set up. Switch on the drive included and start the CPU setup mode. The processor “listens” to the inputs, automatically “stacks” the signals cut into frequency bands (including phase shifts), performs de-ecalization, and you get a “restored”, like tomato juice from paste, sound signal. The algorithm of such addition is the pride of the developers.

Snobs will probably swear, saying what kind of audiophile is this if we’re not dealing with the original signal, but with the assembled, excuse me, “from d… and sticks”? I agree, nobody’s talking about the High End here. But first of all, the system will still end up playing two heads better than a regular balalaika. And secondly, and this is the most important thing – in this case the processor is needed to correctly fit into the system an additional high-quality source, fully preserving the functionality of the original head unit.

However, there are not so many serious sources designed exclusively for automotive applications at the moment. Except for the Sony GS-9, which reads everything up to DSD format, and Audison bit Play, which Italians are still driving crazy. It is true that the craftsmen use home players in cars (including your submissive), but it can not be taken into account. Nevertheless, as the character said from an old anecdote, “the trend, however,” – the course for Hi Res in the car has already been taken. And processors (including those with built-in amplifiers) are the key link here.

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