I thought it would be useful and interesting to many. Information taken from the Internet.
The tweeter is also a tweeter, it is also a tweeter, the smallest in your car. Typically installed in door pillars. The size is about 5 cm in diameter.
MF speaker - midrange speaker.
woofer - subwoofer (bidbass)
One of the mandatory stages of sound tuning in the car interior is the selection of the optimal frequency separation between all radiating heads: LF, LF/MF, MF (if any) and HF. There are two ways to solve this problem.
Firstly, a restructuring, and often a complete redesign of a regular passive crossover, and secondly, connecting the speakers to an amplifier operating in multi-band amplification mode, the so-called Bi-amp (two-way amplification) or Tri-amp (three-way amplification) options.
The first method requires serious knowledge of electroacoustics and electrical engineering, therefore, for independent use, it is available only to specialists and experienced amateur radio electronics engineers, but the second, although it requires a larger number of amplification channels, is also available to a less trained motorist.
Moreover, the vast majority of sold power amplifiers are initially equipped with a built-in active crossover. For many models, it is so developed that with success and sufficiently high quality it allows you to implement multi-band speaker switching with a large number of speakers. However, the absence of a developed crossover in an amplifier or head unit does not stop fans of this method of scoring the interior, since there are many external crossovers on the market that can solve these problems.
First, it should be said that we will not give you one hundred percent universal recommendations, since they do not exist. In general, acoustics is a field of technology where experiment and creativity play a big role, and in this sense, fans of audio technology are lucky. But to conduct an experiment, so that it does not work out, like that crazy professor - with explosions and smoke - certain rules must be followed. The first rule is do no harm, but others will be discussed below.
Most of all, the inclusion of midrange and (or) high-frequency components causes difficulties. And the point here is not only that it is these ranges that carry the maximum information load, being responsible for the formation of the stereo effect, the sound stage, and are also highly susceptible to intermodulation and harmonic distortion if the crossover frequency is set incorrectly, but also that this frequency directly depends and reliability of the midrange and tweeters.
Turning on the tweeter.
The choice of the lower cutoff frequency of the range of signals supplied to the HF head depends on the number of bands of the speaker system. When a two-way speaker is used, then in the most typical case, i.e. when the woofer / midrange head is located in the door, it is advisable to select the cutoff frequency as low as possible to raise the level of the sound stage. Modern high-quality tweeters with a low resonant frequency FS (800-1500 Hz) can already reproduce signals from 2000 Hz. However, most tweeters used have a resonant frequency of 2000-3000 Hz, so remember that the closer to the resonant frequency we set the crossover frequency, the more stress is placed on the tweeter.
Ideally, with a filter attenuation slope of 12 dB/oct, the separation between the crossover frequency and the resonant frequency should be greater than an octave. For example, if the resonant frequency of the head is 2000 Hz, then with a filter of this order, the crossover frequency should be set to 4000 Hz. If you really want to choose a crossover frequency of 3000 Hz, then the steepness of the filter attenuation characteristic should be higher - 18 dB / oct, and better - 24 dB / oct.
There is another issue to consider when setting the crossover frequency for a tweeter. The fact is that after matching the components over the reproducible frequency range, you still need to match them in level and phase. The latter, as always, is a stumbling block - everything seems to be done correctly, but the sound is "not the same". It is known that the first order filter will give a phase shift of 90 °, the second - 180 ° (opposite phase), etc., so during tuning, do not be too lazy to listen to speakers with different switching polarities.
The human ear is very sensitive to the frequency range of 1500-3000 Hz, and in order to transmit it as well and cleanly as possible, one should be extremely careful. It is possible to break (split) the sound range in this area, but you should think about how to properly eliminate the consequences of unpleasant sound later. From this point of view, a three-way acoustic system is more convenient and safe for tuning, and the midrange speaker used in it allows not only to effectively reproduce the range from 200 to 7000 Hz, but also to solve the problem of building a sound stage more easily. In three-way speakers, the tweeter is turned on at higher frequencies - 3500-6000 Hz, that is, obviously above the critical frequency band, and this allows you to reduce (but not eliminate) the requirements for phase matching.
Turning on the midrange head.
Before discussing the choice of the frequency of separation of the midrange and bass ranges, let's turn to the design features of the midrange speakers. Recently, midrange speakers with a dome diaphragm have been very popular with installers. Compared to cone midrange drivers, they provide a wider radiation pattern and are easier to install because they do not require additional acoustic design. Their main drawback is the high resonant frequency, which lies in the range of 450-800 Hz.
The problem is that the higher the lower cutoff frequency of the band of signals fed to the midrange speaker, the smaller the distance between the midrange and bass heads should be, and the more critical it is where exactly the woofer stands and where it is oriented. Practice shows that dome midrange speakers can be turned on with a crossover frequency of 500-600 Hz without any problems with matching. As you can see, for most of the items sold, this is a fairly critical range, so if you decide on such a division, the order of the separation filter should be quite high - for example, 4th.
It should be added that dome speakers with a resonant frequency of 300-350 Hz have recently begun to appear. They can be used starting from a frequency of 400 Hz, but so far the cost of such instances is quite high.
The resonant frequency of midrange speakers with a cone cone is in the range of 100-300 Hz, which allows them to be used starting from a frequency of 200 Hz (in practice, 300-400 Hz is more often used) and with a low-order filter, while the woofer / midrange speaker is completely freed from the need to work in the midrange. Reproduction without separation between the speakers of signals with frequencies from 300-400 Hz to 5000-6000 Hz makes it possible to achieve a pleasant, high-quality sound.
Turning on the woofer/midrange speaker.
Gradually we got to the low-frequency range. Modern mid/bass speakers allow you to work effectively in the frequency band from 40 to 5000 Hz. The upper limit of its operating frequency range is determined by where the tweeter (in a 2-way speaker) or midrange driver (in a 3-way speaker) starts to work.
Many are concerned about the question: is it worth limiting its frequency range from below? Well, let's see. The resonant frequency of modern woofer/midrange speakers with a size of 16 cm lies in the range of 50-80 Hz, and due to the high mobility of the voice coil, these speakers are not so critical to work at frequencies below the resonant one. Nevertheless, the reproduction of frequencies below the resonant one requires certain efforts from it, which leads to a decrease in the return in the range of 90-200 Hz, and in two-way systems, the quality of the transmission of the midrange range. Since the main energy of the bass drum strikes falls on the frequency range from 100 to 150 Hz, the first thing you lose is a clearly defined punch (punch - hit). By limiting the range of signals reproduced by the low-frequency head to 60-80 Hz from below with the help of a high-pass filter, you will not only allow it to work much cleaner, but also get a louder sound, in other words, a better return.
Subwoofer.
It is better to entrust the reproduction of signals with frequencies below 60-80 Hz to a separate speaker - a subwoofer. But remember that the sound range below 60 Hz is not localized in the car, which means that the installation location of the subwoofer is not so important. If you have fulfilled this condition, and the sound of the subwoofer is still localized, then first of all it is necessary to increase the order of the low-pass filter. You should also not neglect the infra-low frequency suppression filter (Subsonic, or Finch). Remember that the subwoofer also has its own resonant frequency, and by cutting off frequencies below it, you achieve comfortable sounding and reliable operation of the subwoofer. As practice shows, the pursuit of deep bass significantly increases the cost of a subwoofer. Believe me, if the sound system you have assembled with good quality reproduces the sound range from 50 to 16,000 Hz, this is quite enough to comfortably listen to music in the car.
Head pairing methods.
Quite often the question arises: should I have the same order of low-pass and high-pass filters? It is not necessary at all, and it is not even necessary at all. For example, if you installed a two-way front speaker with a large speaker separation, then in order to compensate for the dips in the frequency response at the crossover frequency, the bass / midrange head is often included with a filter of a lower order. Moreover, it is not even necessary that the cutoff frequencies of the high-pass filter and low-pass filter coincide.
For example, to compensate for excess brightness at the separation point, the woofer / midrange head can operate up to 2000 Hz, and the tweeter - starting from 3000 Hz. It is important to remember that when using a first-order filter, the difference between the cutoff frequencies of the high-pass filter and the low-pass filter should be no more than an octave and decrease with increasing order. The same technique is used when pairing a subwoofer and midwoofer to attenuate standing waves (bass booming). For example, when setting the cutoff frequency of the low-pass filter of the subwoofer to 50-60 Hz, and the high-pass filter of the LF / MF head to 90-100 Hz, according to experts, unpleasant overtones due to the natural rise in the frequency response in this frequency region due to the acoustic properties of the cabin are completely eliminated .
So if the quantity-to-quality rule works in car audio, it only holds true in terms of the cost of individual components and man-years, which determine the experience and skill of the installer, who will force the system to reveal its sonic potential.
Do you want to get more targeted traffic with, but promotion for high-frequency queries seems problematic? Try it differently. Use promotion on low-frequency queries, and low-frequency traffic will greatly surprise you: it will come faster, it will be higher, and the competition is lower. But "how is it so?" and "what's the catch?" - I'll tell you more now.
High frequency and low frequency requests
Imagine a huge apple tree with overgrown apples growing at the top (HF requests), and at the bottom everything is strewn with fallen smaller apples (LF requests). At the top, apples are big, beautiful, not always tasty, but they are in great demand. Many people climb to the top of the tree for the biggest apple, fight for it. At the same time, not the largest, but ripe and tasty apples grow at the foot in huge quantities, and no one fights for them. Your task: to get as much apple mass (whole SEO traffic) as possible.
What will you choose?
- Collect a full bag of smaller apples.
- Join the battle for the biggest apple.
The most curious thing is that choosing the first item does not mean at all that you have given up and are not going to fight for the top of the tree and the biggest apples. You just take the time to prepare for the battle with competitors, and the more low-frequency queries you collect, the easier it will be for you to get a place in the TOP.
What queries are considered low frequency
Low-frequency queries most often describe a specific need. Here examples of low-frequency queries:
- buy car toyota rav4 2011 in moscow
- children's center moscow vdnh wool felting
- kate upton carls junior commercial
Therefore, unlike high-frequency queries, low-frequency queries can convert better, since a page tailored for a low-frequency query is more likely to give the visitor a usable result.
Promotion for low-frequency queries
Low frequency requests are unpretentious: they do not need to be fertilized with external links, you need to simply and informatively give an answer to the exact low-frequency search query. If the answer is useful, the site page dedicated to this low-frequency query will quickly appear in other search engines, receive it, and it can be transferred to other pages of the site that are more difficult to promote, for example, for mid-frequency queries.
There are practically no problems with how to promote low-frequency queries. Low-frequency queries promote themselves and help promote the entire site as a whole, laying the foundation as a solid foundation and the basis of the site's semantics. Low-frequency requests allow you to reach widely and thereby attract more traffic for a larger number. Large keyword reach- an important one that can affect the promotion of all pages of the site in the search by saturating the topic with keywords.
Selection of low-frequency queries
How to choose low-frequency queries? Fully! All LF queries you can find, up to 1 impression per month. Why? Because the Internet is actively developing, and if now an LF query is searched 10 times a month, then in six months they can start searching 100 times a month. Although the point is not even in impressions for low-frequency key queries, but in semantics, as I wrote above. And also that each key request is a question and if YOU do not answer the question, then YOUR COMPETITOR will answer.
Low-frequency requests - how much? The more requests you collect, the better. The more requests are reflected on the site, the more low-frequency traffic will be and the faster the promotion of mid-range and high-frequency requests will go.
Advantages of website promotion for low-frequency queries
Since the coverage of LF key queries is gradual, it is possible to clearly assess and plan costs and results. Moreover, the result of promotion for low-frequency queries is the most stable among all promotion methods. These sites are the hardest to compete with.
In order to promote the site for low-frequency queries, it is enough to regularly and methodically describe low-frequency queries on the site. How? Create, answer questions from the audience. In parallel with creating content, plan. Even a beginner can engage in site promotion with low-frequency queries, this is the easiest way to understand how search engines work in “combat conditions”, without going broke and not losing what has already been gained.
The promotion of low-frequency queries is also the biggest plus of such promotion - the absence of regression. YES! Content is not purchased links, it will not dissolve after you stop paying. It will stay with you and continue to drive traffic. In fact, low-frequency promotion is a win-win option if the specifics of your work and subject matter allow you to work with low-frequency requests.
What is the result
- Low competition for targeted queries.
- High conversion to .
- Ease of advancement even for a beginner.
- Large coverage of key queries and target audience.
- Stability of growth of positions and traffic.
- Accurate planning of promotion costs.
- High frequency of site indexing due to development.
Do you promote the site for low-frequency requests?
In today's article, we will talk about search queries. And, as you may have guessed from the title ;-), there are 4 types - long tail, low-frequency, mid-frequency and high-frequency.
You will also learn what are the advantages and disadvantages of these queries, and what keywords are best to rank for.
Types of search queries:
A long tail is a search query that is very rarely requested by the user (1-10 times a month). In another way, a long tail is also called a Long tail query. Here is an example of such requests:
- buy a laptop in an online store inexpensively on credit;
- how to create a website yourself for free step by step instructions video;
- buy Chinese phones wholesale in Odessa;
- buy samsung tv 22 inches in moscow;
- how to make money online without a website.
I checked each of these queries on wordstat.yandex.ru. It turns out that Yandex shows them to visitors no more than 10 times a month. 
Despite such a low number of impressions, I believe that it is a must to use them when selecting keywords.
Firstly, if a visitor gets to the site on a request, for example, "buy Chinese phones wholesale in Odessa", then he will buy Chinese phones in bulk, and in Odessa: smile :. For such keywords, the most targeted visitors come, who, in most cases, become buyers.
Secondly, there is practically no competition for long tail queries, and it is very easy to reach the TOP. To do this, it is enough to enter such a request once into the article and put several internal links with such a .
Well, and, thirdly, 60-90% of all visitors come to the site for such requests. Yes, yes, you may be surprised and disagree with me, these dummies, as many people call them, provide more than half of the search traffic.
I'm not saying that you need to create a special page to get to the top. You don't need to do this. But such a tail can be added to the main request. For example, you are advancing on the request of how to make money on the Internet. So why not write once in an article how to make money on the Internet without a website. This is very easy to do, and there will be a lot of sense from it. I also advise you to read the article: "?" In this article, you will learn where to look for such queries and how to correctly enter them into the text. 
Low frequency requests (LF)- These are requests that have low competition and are rarely requested by users. For example, here are a few low-frequency queries:
- buy a Chinese tablet online store;
- plastic windows in Moscow cheap;
- buy oil for a chainsaw Stihl;
- repair in the apartment with your own hands where to start.
Do not confuse low-frequency requests and a long tail. Low frequencies differ from the long tail in that they have more impressions per month. In most cases, it is very easy to get to the top for such queries. To do this, you need to create a special page and write a large article tailored to this request. Then you can also put down a few links from other internal pages, or buy a few links on other thematic sites.
But there are also situations when low-frequency requests are highly competitive. This sometimes happens in highly competitive commercial niches. Therefore, you should always analyze each request and look at the sites that are in the top for it.
The advantage of these requests is that the visitors go to the target site and in most cases become buyers when it comes to commercial niches. The main disadvantage is that very few people come to them and bring the site only for low-frequency queries, it is very difficult to get high traffic from search engines. 
Mid-Frequency Requests (MF) are requests that are requested by visitors approximately 1,000 to 10,000 times a month. For each niche, this number will be different. Here are some examples of mid-range queries:
- how to make money online without investment;
- kitchen knives;
- buy plastic windows;
- what is music;
Many people think that mid-frequency requests are necessarily medium-competitive. In most cases it is, but not always. Here, for example, take two queries: “what is music” and “buy plastic windows”. Although these requests are mid-frequency, but still, it is much more difficult to move to the top in the second one than in the first one. This is due to the fact that the first request is informative, and the second is commercial. And since commercial requests bring money, then the competition for them is great. This once again suggests that, first of all, you need to take into account the competition, and only then the number of impressions.
Mid-frequency requests are like a golden mean and you need to move along them. They will bring a lot of visitors, and it is also quite possible to reach the top. 
High frequency requests (HF)- These are the queries that are requested by users the most times. As usual, I will give an example of such requests:
- a laptop
- music
- plastic windows
- Yandex
The main advantage of these queries is that they are able to bring the largest number of visitors to the site from . But here is their disadvantage - they are very competitive, and in order to reach the top of them, you need to spend a lot of time and money.
Also, I don't like to rank for high volume keywords because they have very low conversion rates. For example, a visitor enters the word "laptop" into a search engine. I don't understand what he is looking for. He wants to buy a laptop, or look at prices. And can read the information or see photos of laptops: smile :. Thus, the page can be one thing, and the visitor is looking for something completely different. Also, which is in the top for a high-frequency query will be larger than, for example, a page that is in the top for a low-frequency query. 
What are the best keywords to rank for
In short, it is best to move on all requests at once, and it does not matter if the site is one day old or 10 years old. I will now explain why I think so. See, for example, we have 4 requests.
- Long tail - how to create a website yourself for free without registration; (6 impressions)
- Low-frequency request - how to create a website yourself for free; (370 impressions)
- Mid-frequency request - how to create a website yourself; (2022 impressions)
- High-frequency request - site. (15,859 impressions)
It makes no sense to create a page for the long tail, since we will receive very few visitors. Our site Yandex will show only 6 times a month, believe me, this is very little: smile :.
It is also not worth promoting on the request “website”. Firstly, there is a lot of competition, and secondly, this is not a targeted request and we will get a high bounce rate. It remains to choose a low-frequency or high-frequency request. Both of these options are good, but it's best to move through all of these queries at once. 
To do this, we can simply combine all these requests into one phrase - “how to create a website yourself for free without registration”, and write this phrase in the headlines, several times in the article and in the link url. For a complete set, you can also add some subtitle to the ALT tag. You can put down internal links with the anchor of this key phrase.
After a while, the long tail and low-frequency query will be in the top if you write a good article. Mid-frequency query can be forgotten in the top external links. As for the tweeter, you need to look at what position it is. If it is at least in the top 30, then you can also promote it with the help of external links. Only such links will need much more: smile :.
If you use this keyword selection scheme, you will get much more visitors to your site from search engines. Many may ask: “What if it doesn’t work out to combine all the queries?” If it doesn’t work out, then you can combine at least mid-frequency and high-frequency or low-frequency and long tail queries, etc. Sometimes I manage to combine 6 queries into one phrase that can be easily entered into an article. The main thing is to spend more time on the selection of keywords and it is better to select words for a separate article, and not for the whole site at once, because if you select for a site, you can get confused :smile:.
That's all for me. I thought to briefly describe the types of search queries - long tail, low-frequency, mid-frequency and high-frequency, but it turned out, as always, much more ;-).
To compose a semantic core (SN) and do it absolutely free, you need to: use a wonderful, and most importantly - free, service from the Yandex search engine, which is called Yandex Wordstat. This service is available at wordstat.yandex.ru. In addition to the specified service, we will also use a free program looch.
How to use Yandex.Wordstat?
In a special input field, we write phrases or individual words, the frequency of which we want to check and select similar ones. Then we press the button "Pick up".
After the selection, we will see the statistics of queries in the specified search engine, which will include the phrase or word we specified. In addition, there we will see other queries that were indicated by people using the words we specified. Phrases and words will be in the column on the left, and other queries on the right.
Some numbers will be displayed next to each request. They give some preliminary forecast of the number of impressions per month. And, perhaps, we will receive this number of impressions when specifying this query as keywords or a word. Let's say a certain number next to the word "laptop" will indicate the number of impressions with the word "laptop" for all queries, such as: "compare laptop", "buy a laptop", "laptop broke" and so on..
You can also specify "All regions" and then the selection of words and phrases will come from "the whole world". Or you can specify a specific region or regions and the selection will match queries only from the specified region.
Why are we not going to select words with the Slovoeb program?
The thing is that this program has recently often been somewhat disappointing and issues 50 requests at once. Also, the requirement to enter captcha appears very often.
What is the program klooch ?
With the help of this free program, you can easily determine, so to speak, the freebie of a particular request. More on this will be discussed below.
How to determine the frequency of the request?
There is no absolutely definite indication to determine the frequency of a request! For example, for non-commercial requests, this level is higher than for commercial requests.
Without insisting on anything, it can be defined as follows:
Micro-low-frequency (mLF) — from 0 to 200 requests within a month;
Low-frequency (LF) - from 200 to 1200;
Medium frequency (MF) - from 1500 to 5000;
High frequency (HF) - from 5000 and almost to no limit.
You can also highlight Mega frequency (mHF), but you should not delve into this.
How to determine the competitiveness of the request?
The competitiveness of requests can be determined by formulas, or you can do it “by eye”. For example, you can see the number of documents that appear in the search results for a specific query:
1) Results from a million or more - highly competitive (VC);
2) From 100,000 to 1 million - medium competitive (SC);
3) Up to 100,000 - low competitive.
This sorting will never tell you exactly, so we will not take it into account. Competition can also be identified by direct entry into the title of the article - the more entries, the worse for us; by the total number of optimized articles - the fewer such articles, the better; by the number of main pages in the issue - the fewer muzzles, the better; according to the trust of the site from the issuance - a smaller trust is better.
There are many such divisions, we have indicated the main ones. First, we need to define the topic of the request. For example, the topic of our site is games. So, you do not need to take the request "how to train cats", since this request does not fit with our topic. And for search engines, all this is not very good.
For example, let's take the same theme of "games". We enter a general query into Yandex.Wordstat, such as "play ....", ".... finish the game":
After that, we select a rarer request, such as "play racing".
We see the following:
Now we select low frequency request. But, there are also a lot of generalized queries. Therefore, we need to go to the second page and select the query "play racing against zombies." Number of requests per month - 516:
We analyze:
According to the Klooch program, there are no matches in the Title in Yandex. Therefore, you can easily reach the TOP10 or even TOP3. How to determine the freeness of the request now ?!
Let's say there are five matches in the Title - then you can easily reach the top 6. That is, the fewer matches in the Title, the better for us. The situation is similar for the main pages.
Further, we copy all found requests in Excel. But! The frequency of 500 requests per month does not interest us. You need to find the average frequency queries. Let's take a closer look at the example of the request "race to play online makvin".
We analyze:
This is a medium frequency query with a long tail. This request is low competitive. There are few pages in the search results for this query. It can also be included in the semantic core.
Now it's time to find a free high-frequency request, for example, "cars play races."
Website promotion queries are keywords or phrases that Internet users use to search for information about specific goods, services, etc. All search queries are divided into three types: low-frequency, mid-frequency and high-frequency. In addition, an additional category of "long tail" is distinguished.
Low frequency requests
These are keywords for which Internet users search for information no more than 1,000 times a month. The search takes place with the help of special search engines, the most famous of them are Yandex and Google.Examples of low-frequency queries are “buy cheap spare parts in Moscow” and “Lenta Style dress model 1068”.
By creating a page for low-frequency keywords, you will attract your first audience to the site. And in two months (or maybe less) your site will get into the TOP-10 search engines for the queries you promote.
Mid-Frequency Queries
Queries that are most popular. In search engines, they are entered from 1,000 to 10,000 times a month.An example of mid-frequency queries is "asus monitors".
Promotion for keywords in this category must begin when you have already taken at least some positions in the search for low-frequency words.
To advance on mid-range queries, it is necessary to carry out internal linking between the pages of the site, as well as purchase external links on third-party Internet resources. At the same time, it is important that third-party sites have a good reputation and trust, and links do not look like outright spam.
High frequency requests
Keywords in this category are the most popular among Internet users. This group includes queries that appear on search pages more than 10,000 times a month.An example RF request is "Apple".
To be in the top for this type of words, you need patience, attention and hard work. The term of getting into the top ten sites for high-frequency requests can take from six months or more.
Before you take on the promotion of high-frequency queries, you must firmly gain a foothold in mid-frequency and low-frequency words. Internal linking should be in perfect condition, and external link mass on verified sites should increase steadily. In addition, you will have to familiarize yourself with concepts such as "behavioral factors" and "promotion through articles."
A long tail
Requests for which users are looking for information even less frequently than for low-frequency ones.An example of a long tail is Alcatel one touch phone reviews.The promotion of such keywords often happens by itself. And if not, then they should be given attention. After all, if a user goes to the site on such a request, the probability of buying a product or service is 99%.
