What are coaxial speaker systems?
Coaxial acoustics
- This is a separate type
of speaker
system in which the high and low frequency speakers are separated and located on the same axis.
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Acoustics: pop or component?
Almost every motorist comes to the point that he is no longer satisfied with the quality and volume of sound in the car. Most people solve this problem by simply upgrading their sound system, increasing the number of speakers and amplifiers. But true gourmets and lovers of experiments also pay attention to pop speakers .
Any car speakers that are of excellent quality begin to make unpleasant, hoarse sounds at maximum volume. In this regard, pop speakers will give everyone else a head start. In other words, their role, first of all, is to increase the maximum volume level without losing quality.
Among people who know a lot about car audio, there is an opinion that there are two types of pop speakers. The first is speakers designed by manufacturers specifically for car audio systems. And the second type is pop-up speakers and other components from companies that have nothing even remotely related to cars. It is believed that the former are inferior in quality to the latter. They say that car pop speakers do not have high-quality sound.
The trump card of the “stand” is its sensitivity and flexibility in tuning high, mid and low frequencies. The sensitivity of conventional car speakers is about 90 dB. Variety shows have a level of this indicator of 100 and above.
Stage speakers differ from each other in a number of technical characteristics. First of all, power . The average speaker system has a power rating of approximately 100 Watts to 400 Watts with a sensitivity of 100 dB. The frequency range of such speakers also varies - the average is from 100 to 11,000 Hz. Also, when choosing stage speakers that are installed in the side panels of the front doors, you need to take care of their size.
If you listen to the advice of professionals, then those motorists who also have high-quality music should equip their “swallows” with pop acoustics. For example, playing regular audio recordings in MP3 format with a quality of 192 kbit/s, you will not be able to appreciate the full power and quality of the “variety”.
We compared it with the sound at home, now we will very briefly compare it with the loud sound of a car a la “variety”.
- Stage acoustics are designed for listening at long distances and for covering large areas. Up close, its sound, according to the very idea of the manufacturers, should not stand out with special quality.
Let's take as an example a good concert with high-quality, loud, powerful sound. This sound is concentrated in the hall itself, while close to the speakers this sound can hardly be called pleasant. In a word, the stage works well in the far field.
Lemmy Kilmister, Motorhead. Try standing next to these speakers. There will be nothing good in terms of sound quality.
I'm not against the car stage, but I only understand the option when they listen to it on the street, using the car as a mobile concert stage. Listening to this sound inside the cabin is completely impractical. Those who want good sound in the cabin and good sound outside have two separate systems: in the front - SQ, in the rear - stage. It is impossible to combine the qualities of both in one.
But let me emphasize - precisely in the near field. In the far field, it is possible and even necessary to tune the “stage” to good sound. It is important that the system is correct. More on this below.
- In 99% of the automotive stage there is a strong failure in midbass, it simply doesn’t exist! That is, the sub plays up to 60 Hz, the midrange plays from 200-250 Hz (at best from 160 Hz), and there is an abyss between them.
But this is the most driving range, it’s all meat! This is partly why the choice of specific music to demonstrate the capabilities of the automotive stage is due to deep bass and music consisting of mid and high frequencies, then the failure is not so noticeable. But try to turn on, for example, rock music on such a system and everything will become clear.
The bass player had half of his strings torn off along with his fingers, the drummer had one of his hands cut off, and the vocalist had the part that gives his voice masculinity torn off. Well, most importantly, the punch disappears!
Those who think that 200 Hz is punch are mistaken. 80-125 Hz - that's where it is! Go to a rock concert and compare the sound with a car stage, even if not in terms of volume, but in terms of the sound and energy itself, and everything will become clear. The only way to achieve true concert sound from a car is to use fifteen-inch midbass like at a concert and place them in huge boxes that won't fit in the doors.
Therefore, I will repeat that a really cool stage is possible not in the form of a loud front, but in the form of a serious system for the entire trunk, which will occupy not only the subwoofer, but also the midbass!
Compact and loud. Very loud
Big test of “variety” coaxial acoustics
Everyone is accustomed to the fact that the “stage” front consists of separate midrange speakers with high sensitivity and separate tweeters, in most cases horn-type. Loud systems are almost never built using coaxial acoustics. And there are actually very few suitable coaxial cables. And those that exist are very different from the usual ones. I managed to collect five such models for measurements at once and study them in more detail.
“Variety” coaxial speakers are built completely differently than conventional car coaxials. There, the tweeter is small in size and is usually mounted on a leg in front of the diffuser. And here the tweeter is sort of built into the midrange speaker. Or rather, it even “pierces” him right through.
The fact is that what is used here is not an ordinary high-frequency driver, but, as expected for loud systems, a compression horn HF emitter, which consists of two main parts - the driver and the horn “pipe” itself. I already had similar designs in my measurements. For example, here or here. And soon there will be several more like this.
The driver in all models of today's test is “attached” to the main speaker from its rear side and literally radiates through it - through the axial hole in the core. It is a horn for him. In the front part, the exit is closed with a protective mesh and continued with a plastic “pipe”.
Ground Zero GZCF 200COAX (8 inches)
When you pick up this speaker for the first time, your first thought is that it is clearly not intended to work as a midbass. Firstly, the top suspension of the diffuser is very narrow and practically does not provide any freedom of movement. In addition, the diffuser “cone” has a curved profile, and if the coil pushes the diffuser too hard, it will not move as a single unit, but will simply bend. So this is a pure low excursion midrange driver, no options.
The tweeter and midrange are connected separately. They can be connected either per channel or to one channel. The tweeter in this case is connected through a 5.6 µF capacitor from the kit. Don’t get confused, the tweeter terminals are at the bottom, and the midrange speaker terminals are on the basket.
Ground Zero GZCF 200COAX
Red curve – midrange speaker impedance Blue curve – tweeter impedance Purple curve – tweeter impedance with a standard capacitor Green curve – impedance of the entire system assembly
- Fs (natural resonant frequency) – 152 Hz
- Vas (equivalent volume) – 5.4 l
- Qms (mechanical quality factor) – 10.34
- Qes (electrical quality factor) – 0.66
- Qts (total quality factor) – 0.62
- Mms (effective mass of the moving system) – 14.7 g
- BL (electromechanical coupling coefficient) – 8.5 T m
- Re (voice coil DC resistance) – 3.4 ohms
- dBspl (reference sensitivity, 1m, 1W) – 96.5 dB
Ground Zero GZCF 200COAX
Red curve – frequency response along the speaker axis Blue curve – frequency response at an angle of 30 degrees Green curve – frequency response at an angle of 60 degrees
Soundstream SP2.804 (8 inches)
Unlike Ground Zero, here the midrange driver is built differently - the diffuser and top suspension are completely different. This resulted in the resonant frequency being slightly lower. But this is still a mid-range driver without even the slightest hint of upper bass.
The tweeter and midrange speaker connections are also separate, although no crossover filter is included. So we either use the speaker in the channel, or we select the filter ourselves. A regular capacitor is quite suitable for this. You can use the same one as Ground Zero, but I would rather take a smaller one - 3.3 or 2.2 uF.
Soundstream SP2.804
Red curve – midrange speaker impedance Blue curve – tweeter impedance
- Fs (natural resonant frequency) – 137 Hz
- Vas (equivalent volume) – 6.2 l
- Qms (mechanical quality factor) – 11.31
- Qes (electrical quality factor) – 0.74
- Qts (total quality factor) – 0.70
- Mms (effective mass of the moving system) – 13.7 g
- BL (electromechanical coupling coefficient) – 7.4 T m
- Re (voice coil DC resistance) – 3.4 ohms
- dBspl (reference sensitivity, 1m, 1W) – 95.4 dB
Soundstream SP2.804
Red curve – frequency response along the speaker axis Blue curve – frequency response at an angle of 30 degrees Green curve – frequency response at an angle of 60 degrees
Magnum MPS 8.0-4AB (8 inches)
The speaker almost completely repeats the design of Ground Zero - a narrow upper suspension of the diffuser and a strongly curved profile of the diffuser itself. The only external difference (of course, except for the color of the “pipe” and the logo) is the single terminals for connecting the midrange speaker, like Soundstream. True, unlike the latter, there is still a capacitor in the kit - it is carefully soldered to the tweeter terminals. Its nominal value is 3.3 µF.
But inside there were a little more differences from GZ. Firstly, the resonant frequency is lower. And the reason for this is not the diffuser (the Mms parameter coincided to within hundredths), but, most likely, slightly different suspensions. And the tweeter, apparently, is also different - the resonances are not so pronounced.
Magnum MPS 8.0-4AB
Red curve – midrange speaker impedance Blue curve – tweeter impedance Purple curve – tweeter impedance with a standard capacitor Green curve – impedance of the entire system assembly
- Fs (natural resonant frequency) – 133 Hz
- Vas (equivalent volume) – 7.0 l
- Qms (mechanical quality factor) – 11.85
- Qes (electrical quality factor) – 0.62
- Qts (total quality factor) – 0.59
- Mms (effective mass of the moving system) – 14.7 g
- BL (electromechanical coupling coefficient) – 8.2 T m
- Re (voice coil DC resistance) – 3.4 ohms
- dBspl (reference sensitivity, 1m, 1W) – 96.3 dB
Magnum MPS 8.0-4AB
Red curve – frequency response along the speaker axis Blue curve – frequency response at an angle of 30 degrees Green curve – frequency response at an angle of 60 degrees
Magnum MPS 6.5-4AB (6.5 inches)
This speaker is essentially a smaller version of its 8-inch older brother. The same solutions are used here - a short-throw suspension and a strongly curved diffuser profile. Unless the horn output has a slightly different geometry, otherwise it would simply cover half of the diffuser. The coil size is 1.5 inches (larger speakers use 2 inch coils). The capacitor for connecting the tweeter has a value of 3.3 µF.
Magnum MPS 6.5-4AB
Red curve – midrange speaker impedance Blue curve – tweeter impedance Purple curve – tweeter impedance with a standard capacitor Green curve – impedance of the entire system assembly
- Fs (natural resonant frequency) – 161 Hz
- Vas (equivalent volume) – 3.6 l
- Qms (mechanical quality factor) – 10.80
- Qes (electrical quality factor) – 0.60
- Qts (total quality factor) – 0.57
- Mms (effective mass of the moving system) – 7.2 g
- BL (electromechanical coupling coefficient) – 6.2 T m
- Re (voice coil DC resistance) – 3.4 ohms
- dBspl (reference sensitivity, 1m, 1W) – 95.9 dB
Magnum MPS 6.5-4AB
Red curve – frequency response along the speaker axis Blue curve – frequency response at an angle of 30 degrees Green curve – frequency response at an angle of 60 degrees
Edge EDPRO65F-E4
This speaker has exactly the same concept as the others, but its design is noticeably different. A different basket is used here. The diffuser and fabric suspension here are not so extravagant, but more traditional. The protective mesh is non-removable, glued well, and did not give in to attempts to remove it. Since I took the speaker with a return, I didn’t really insist.
The coil here is also 1.5-inch, cooled through large windows under the centering washer. Despite the fact that the resonant frequency turned out to be the lowest of all, below 100 Hz, I wouldn’t call it a midbass speaker either - the length of the voice coil here is short. So this is a midrange driver. To connect the tweeter, the kit includes a 2.2 µF capacitor.
Edge EDPRO65F-E4
Red curve – midrange speaker impedance Blue curve – tweeter impedance Purple curve – tweeter impedance with a standard capacitor Green curve – impedance of the entire system assembly
- Fs (natural resonant frequency) – 93 Hz
- Vas (equivalent volume) – 7.4 l
- Qms (mechanical quality factor) – 9.20
- Qes (electrical quality factor) – 0.52
- Qts (total quality factor) – 0.49
- Mms (effective mass of the moving system) – 9.7 g
- BL (electromechanical coupling coefficient) – 6.3 T m
- Re (voice coil DC resistance) – 3.6 ohms
- dBspl (reference sensitivity, 1m, 1W) – 92.7 dB
Edge EDPRO65F-E4
Red curve – frequency response along the speaker axis Blue curve – frequency response at an angle of 30 degrees Green curve – frequency response at an angle of 60 degrees
conclusions
All speakers are pure mid/high frequencies with hellish sensitivity. There is no question of using them as midbass; the diffuser stroke is very small. Therefore, you need to cut them from below by at least 500 Hz, and preferably higher. Otherwise, distortions will be unavoidable.
The speakers can work comfortably in tight spaces. This is a useful property, because it’s impossible to install midbass and midrange in one volume; you need to isolate them from each other. 6.5-inch ones will work already in two or three liters, 8-inch ones can allocate from 4-5 liters to each speaker. Fine.
The design of all is such that the horn inevitably covers part of the diffuser. This caused a rather curved frequency response for some speakers. But considering that these are still not audiophile models, and first of all they require high volume, you can’t really find fault with this. And to be honest, most systems with “separated” midrange and high frequency frequencies have no better frequency response.
The midrange speaker and tweeter can be switched on per channel. This definitely won’t make things any worse – it will be possible to play with the frequencies and orders of filters at their junction. If you hang them on one channel, then you can get by with one capacitor per tweeter as a filter. Moreover, everyone except Soundstram already has one in their kit. True, Ground Zero's rating is too large - 5.6 µF; I would replace it with at least 3.3 µF.
In general, in short, the main advantage of such speakers over separate midrange and high frequencies is their compactness. Here we have everything in one dynamic, and even with the ability to work in small volumes. So for many “stage” systems working in open space, they may turn out to be a completely rational choice. The main thing is not to forget that there should still be midbass between them and the subwoofer.
Variety acoustics: sound issues
Installing a good music system in a car has long been commonplace among motorists. Many of them come to the conclusion that the music in the car does not sound loud enough, clear enough, in general, not the way they want. Most solve the problem by “upgrading” car acoustics, increasing the number of amplifiers and speakers. But pop acoustics are the lot of real gourmets. It improves sound clarity at high volumes. Of course, it won’t be able to sound stadiums, but you will be able to hear your favorite tunes in a new way. When buying such equipment, remember that you are not at a concert, but on the road, and you need to look at it carefully so that nothing distracts you.
