• You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Great Mic Sound for your CB or Export Radio-part 2

Robb

Honorary Member Silent Key
Dec 18, 2008
11,432
3,651
323
Silicon Valley CA, Storm Lake IA
Part 1 is here:
http://www.worldwidedx.com/installa...itizens-band-radio-export-radio-part-1-a.html


When one wants to get the best broadcast audio sound possible out of their CB, it is time to understand all of the factors involved that will influence the outcome. We must also have a reference point to understand the components and why we choose them. You might already have some knowledge with mics and preamps; but if you don't we will go over what you need to know. The rest will just be a matter of making a few solder joints to hook it all up. This will involve a small amount of soldering and having a modest budget to complete and perhaps some materials you might already have lying around. The soldering will be necessary to fabricate one of the two cables. The budget can be expected to be anywhere from as little as $100 or up to $300 or more - depending if new or used items are purchased.


Let's consider the transmit bandwidth of your radio...

A local friend of mine was running an Icom radio that was using a very high quality mic (an ElectroVoice RE-27/ND - similar to the classic RE-20 - but improved) and external preamp (a Behringer UltraGain Pro 2200). The radio had a failure at one point, so he sent it in to be fixed. He then had to substitute a Galaxy/General Stonewall Jackson for his station in the mean time - he chose to use his same quality mic and external preamp to run this Galaxy radio. I was astonished that the Jackson sounded just as well as the Icom did. Wheels began to turn.

WE must understand first - that a radio's ability to transmit does so in a narrow portion of what the human ear can hear. The human ear can hear between 20 cycles per second ('low frequencies tones') and up to nearly 20,000 cycles per second ('high frequency tones'). Most CB radios can only hear and transmit from 100cps to 3000cps of audio bandwidth. So we have very little to work with as far as transmit goes. Most of what we understand of speech is contained in this narrow margin; so we can maximize what we DO have to work with here. It is possible to make this narrow bandwidth sound astonishing.

However, the midrange that exists can easily become too cluttered with an abundance of undesirable freq's that can mask its true potential. In effect, the voice will sound anything but natural. What is best to strive for, is an even or more flat response that can represent all of the available frequencies we have to work with! If one were to look at the frequency response of a stock Cobra mic, it would have a large peak in the middle and very little else being used of this 100-3000cps bandwidth spread. The result is transmitting a metallic, nasal sound that is unnatural. What does one expect from a mic that cost the mfr $.25 to produce? It works; and that is the best you can say for it. What we want to do is to make the best of this narrow zone. We can do this by maximizing our equipment used before it enters the mic plug. The radio itself has filters in place to limit this frequency width, but they can also be altered to provide and even wider bandwidth. More on that later after we get the basics down first.

You can't get quality sound out of your radio without a minimum of 3kc wide on SSB. Many CB radios will provide this much width. Although it won't compare to some Ham rigs that can go as wide as 4kc or even 6kc's on SSB! For CB, the CB radio still can be greatly improved with the 3-3.5kc's it does have. The difference can become the difference between day and night. If we can make it sound great on SSB; just consider how much better it will sound on AM - or even FM for that matter . . .


A pause for the cause . . .

If you are already using a power mic on your CB, it is a simplified form of what we are going to expand upon here. They have a mic element, preamp, battery, case, cord, and switch. These mic elements are cheap; their freq response contains all kinds of peaks and valleys that will sound anything but natural from your transmitting radio. Their preamps are also very noisy, and this subtracts from the quality we want to give it. By the time most common power mic preamps get to their best gain curve, they are infested with harmonic distortion. Maybe even as much as 10 to 20%; there were few quality controls in place when built. They weren't built to be studio grade either - to be fair; they were built to work and to be manufactured at a low cost.

Using a dedicated pro quality mic and a separate high grade preamp, the loss if valuable signal to distortion is minimized - and the advantage of a mic that more closely mimics true sound with a decent freq response nets a tremendous gain in audio transmit performance that can be realized by the CB radio enthusiast.

The transmitted sound will change from a 'cheap squeaker' - to a 'chief speaker'.
Our goal is simple to achieve and the cost and time are well spent to attain much in return.


Microphones

The microphone is the most essential player here. We have choices and price ranges that vary. We must understand how these mics work, and choose those will work best four our purposes. Technology today has made quality audio very affordable that was impossible ten years ago. In particular, the abundance of real condenser mics that require preamps can be found easily and at a surprising low cost. Some of these inexpensive condensers rival the high end $3000 mics - and with some homebrew modifications can nearly match them in performance. Not to bad for a mic that can be bought new for $200 and even found used for about $100! So we can afford to spend a little and get a lot. Even professional-grade dynamic mics can work if chosen properly, and can cost as little as $50 used from eBay if you know what to look for.

I'm not going to go into the various polar patterns of mics - such as omni-directionals or figure 8/bi-directionals - we will instead focus on the cardioid directional type. These polar patterns of microphone pickup have little to do with operating a radio - except for the cardioid pattern mic. Cardioid pattern mics are built to be most sensitive in front of the mic, and then sensitivity then falls off sharply from side to side and none directly to the rear of the mic. If choosing either a condenser or dynamic mic; we will want a cardioid pattern type of mic.

The 'proximity effect' is the term used to describe how a mic will change its frequency response when we get very close to the mic. Most every mic will have a stronger bass output as we get closer; and even out as we move away from it by a few inches. We will want to get about 1-3 inches away from the mic that we choose. Using a wind screen will help even out this distribution of detected frequencies and balance the bass and midrange frequencies while eliminating wind blast from out mouth. More on this later.


There are three basic designs of microphones: condenser, dynamic, and ribbon . . .

The ribbon mic uses a thin ribbon suspended between two points of a magnet then picked up by an inductor coil which delivers and adequate freq response - but is very fragile. It has traditionally been used for recording brass instruments - not very friendly to the human voice range. It lacks a freq curve that is harmonious to voice; the nasal sounds of the 1930's recordings is an example. Todays ribbon mic are far more hardy and are used for their ability to reproduce hight freq's with great resolve. One can use these mics; however they are used more often for female voices and instruments than for male voice characteristics. They tend to be strongest in the upper register of the spectrum, which we cannot use anyway. We need a mic that is flat between 20 to 3.5kc.

The dynamic mic is essentially a moving voice coil and magnet - like a speaker - but is far more sensitive. Today's high-end dynamic mics incorporate rare earth metals - like neodymium - for better overall characteristics. They tend to be used most often in live performances because feedback is easier to control, have a high output, and they have a wide freq range as well. Their freq response curve is peaked at various points and will color its sound. There are many different brands with various response curves; some maximized for voice, instruments, or even both.

A condenser microphone uses a charged diaphragm/capacitor that can detect very slight changes in in freq and volume. They require +48v to operate that is supplied by one of the preamps we will choose. They have an extremely wide and flat freq response and offer little to no coloration whatsoever. They are used extensively in the commercial broadcast and recording industry because of their ability to be extremely accurate. There are two basic types of condensers - large and small elements or 'capsule'. The large element capsule mics will have the specs that we want for optimizing sound in this project.

The condenser and dynamic mic will be the mics of choice here for our purposes. For this article, I will be using and discussing both. But I will focus on the condenser, as this is the mic of choice for the most natural sounding audio available for the money spent. The cost of a high quality condenser mic is more affordable than ever, and this will work for you - the CB operator. We will discuss the options between the condenser and dynamic mic, and why one may be chosen over the other.

There are two other type of mic elements - the crystal and the ceramic - but we are going well beyond them in this study. These elements are most commonly found in many of your favorite power mics in the past. Such as the Astatic D-104 Silver Eagle with the crystal element, and the Turner +3 that has a ceramic element. These mics of the past were built and sold for convenience to the consumer utilizing a cheap mic element and a simple but noisy preamp. We like them and use them because they work much better than a stock mic; but we will be doing here with this project will prove to be so much better in every way.


Tomorrow we will cover the basics of mic preamps and then choosing a mic and preamp:
http://www.worldwidedx.com/installa...d-radio-export-radio-part-3-a.html#post237716



Pictured: Ribbon mic, Dynamic mic, Condenser mic, and the condenser element itself . . .
 

Attachments

  • 1199679274_509351721b.jpg
    1199679274_509351721b.jpg
    139.1 KB · Views: 622
  • sm58.jpg
    sm58.jpg
    20.6 KB · Views: 620
  • 00408_300.jpg
    00408_300.jpg
    10.2 KB · Views: 614
  • 32mm.jpg
    32mm.jpg
    37.7 KB · Views: 618

AM will double the width of whatever sideband width you have.

ROBB -

Yes there are two sidebands on AM. However, the lower sideband is a "mirror image" of the upper sideband, and they each contain exactly the same audio information. So there will actually be no difference in audio content between AM and SSB, and the available bandwidth for audio will be the same for both modes...approx 3.5khz. Since human voice frequency range is from 300 to 3000 hz, this is all that is really required from a stock mike. Using a replacement mike, like the ones you pictured, sounds better for two reasons:

1. The microphone's response curve is linear, so the voice reproduction is much more accurate than with a stock mike.

2. The wide frequency response allows the mike to pick up the harmonics of the speaker's voice. Even though they are attenuated by the 3.5khz bandwidth of the transceiver, there is still enough there to make the audio signal richer and more natural-sounding.


- 399
 
In years past I used a Berigher(sp) Tube Pre-Amp one was intended for guitar use and the other for vocal use. Both have similar design but the one for use with electronic instruments had more gain and compression options then the vocal unit.

I still have one that I used to use with my trumpets and harmonicas.

I am into home audiophile hobby and used to be big into car audio. If one is selecting the mic carefully and is selecting the tubes they use in the pre-amp I would not think an elaborate eq setup would be needed for a CB radio or your run of the mill export fake 10 meter radio!!!

Most modern amateur radios have audio compression rf-clipping and some form of user adjustable eq function built in and it is all digital.

Short of direct injection and some seriously expensive and elaborate NPC-RC equipment isn't this over kill?

The more I learn about modern day amateur radio operators the less I want to get my ticket. I used to love to rag chew a long time ago but I need to make new friends as most of the ones I used to talk too are no dead. Dx'ing is not about fantastic audio just getting heard. When did it turn into the pursuit of commercial broadcast sound quality? Is this the norm today? I know it is not the norm in the CB world.

I am should just be glad that we do not need HD broadcast quality sound on our cell phones! I can just see it now a rack of electronics in a Pelican case with wheels on it with a tiny coax going from out smart phone to the case. Hude ground plane antenna coming out of the Pelican case on wheels.....LOL

I am all for nice clean broad sound and I am not against NPC or Compression I guess it is just the extreme that some go too. LOL Especial in the CB world what good is all of that if 99.9% of CB's can not use the extra data you are transmitting?

P.S. Love reading about this stuff though so do not think I am being critical because I do not mean it that way at all.
 
What is best to strive for, is an even or more flat response that can represent all of the available frequencies we have to work with!



WRONG. What is best to strive for is articulation and that is done by boosting 2.4kHz and rolling off the bottom end as described in the extensive research done by Bell Labs research into voice communication and the human ear.


You can't get quality sound out of your radio without a minimum of 3kc wide on SSB.

Rubbish. For radio communications we want communications grade audio, audio that allows us to be clearly understood through all the noise and interference on HF. That can be done quite easily in 2.7kHz. If you want to sound like a broadcast station then set one up.
 
The more I learn about modern day amateur radio operators the less I want to get my ticket. I used to love to rag chew a long time ago but I need to make new friends as most of the ones I used to talk too are no dead. Dx'ing is not about fantastic audio just getting heard. When did it turn into the pursuit of commercial broadcast sound quality? Is this the norm today? I know it is not the norm in the CB world.

It isn't the norm in amateur radio either. There are a few bell ends who are into ESSB who see nothing wrong with transmitting 6kHz wide splattering crap in limited bandwidth but they're mostly looked down upon by everyone else. Robb appears to be one of these into ESSB. He certainly knows nothing about setting up communications grade audio.
 
The whole point to this series of articles, is that you can better audio out of the spectrum available if you play your cards right and use the right gear. Perfectly legal to boot. Some simple mods to CB radios can yield even better response. Just because a radio comes with a marginal mic, there is no real reason that one cannot do a whole lot better than stock. Many more CB enthusiasts have been doing just that over the last few years; just a fact of life.
 
Last edited:
One can use these mics; however they are used more often for female voices and instruments than for male voice characteristics. They tend to be strongest in the upper register of the spectrum, which we cannot use anyway. We need a mic that is flat between 20 to 3.5kc.



Your OPINION on ribbon mics has some flaws. What I posted here refers to SSB audio in regards to a natural clear audio which should be the goal when transmitting on SSB.

Ribbon mics of good quality can be the most natural sounding mics available. Ribbon mics were used during the "Golden age of Broadcast Radio" and Pro Audio studios and are still used today in the Professional recording industry and not just for "female voices". The vintage ribbon mics are still in high demand and carry a hefty price tag , just look on Ebay for a RCA 44 mic and you"ll see. The vintage RCA mics were known for a pronounced bass response because that was the requirements needed back then. I wouldn't recommend that particular mike for radio unless that's what you want.

Ribbon mics of good quality are expensive and fragile so most people don't want to invest in a mic that costs more than their radio. There are amateur radio operators like myself that know the quality of ribbon mics and we know these mics don't need to rely on heavy outboard processing to achieve a great natural sound.

ja1bbp_aea_r84.JPG


Here is some real world data;

The average spoken male voice frequency range is around 85 to 155 hz and the female voice is around 160 to 250 hz. If you look up the Lab tested data sheet on a good ribbon mic such as the one I use, ( AEA R-84 web link: http://www.wesdooley.com/sites/default/files/pdf/R84_Technical_Onesheet_v2.4_web.pdf ) you will see a strong wide frequency response curve peaking around between 100hz to 400hz and not start to really drop 3db until after 10kz, well within the pass band of any good radio and within the natural speaking voice of anybody. This makes it strongest in the lower and middle range of the spectrum which is what you want because the excess will start to fall out of the pass band anyhow.

Sorry to say, This data above discredits your assessment of ribbon mics that you posted.

Good Ribbon mics unlike many mics out there, truly have a 20Hz-20Khz frequency response, not even the popular Ham's favorites EV-RE20 or Heil PR series mics (which are both excellent mics) have that. A lot of mics frequency response curves cut off anywhere from 80 hz to 40 hz on the low and cut the highs anywhere from 15 kz to 18 kz. Generally ribbon mics don't require a preamp or phantom power ( when used for radio service) unless it's an active version.

My ribbon mic has a 270 ohm impedance which is not a problem for my radio's 600 ohm mic input gain stage. ( the reverse isn't true, You can have a lower impedance mic for your radio, but you don't want a mic with a higher impedance than your radio's mic input, It doesn't have to match. Think of it like a 3 inch water hose hooking into a 1 inch valve inlet, too much resistance forcing the water in a smaller opening, now reverse it and no resistance, get it?) I do use a variable impedance mic activator specially designed for ribbon mics which can load the mic up to 15 kilo-ohms which can really open the mic sound even more which is something EQ can't do. This is something you wouldn't or shouldn't do with a dynamic or condenser mic. Normally I leave the mic activator set at 1.5 kilo-ohms due to an over-emphasized bass response at higher settings.(clarification, this is impedance input loading at the mic which ribbon mics can handle and is recommended, this is not impedance loading the output to the radio).

One thing I generally don't care for is people who broadcast over the airwaves with a heavily processed sound. The more EQ and processing done to a signal, the more you get away from the truth. EQ and other processing sounds better when used as a corrective measure rather than trying to boost something that isn't there due to a mic or radio's shortcomings.

Your posting has a lot of good information, but I suspect you don't or have ever owned a quality ribbon mic, the cheap Chinese versions don't count.

This entire post is my opinion, but based off facts and personal experience.

73
 
Last edited:
Ribbon mics are fine, you are right.
But they are more delicate and easier to damage than a dynamic. Even condensers are a bit more hardy. I thought that was made clear. It is true that they have toughened up somewhat; but still the easiest to become a casualty if one doesn't treat them with kid gloves. If you treat your gear as well as I do, then it should be just fine - barring the unseen accident.

The problem that I have with your point, is that having ANY peak from a mic is a bad thing. Why? Because getting the response as flat as possible before tweaking means that less EQ change is necessary to find that sweet spot. In addition, the sound is far more natural when starting from a neutral point of reference. Keep in mind that you only have ~5khz of audio in which to get the most detail that you can at best; don't waste it on color. Just pointing out a factor that one should be wary about - is all.

That is why I use a condenser mic, and prefer it. Mic audio 'color' is something to be avoided. Becaue if your voice falls within that color range, it will be hard to make it sound as natural, since there is an abundance of that color already in that mic. Otherwise, one might as well just go ahead and use an Astatic D-104, which already has too much color of its own and has really very little chance to become neutral before EQing it. Not saying that your ribbon sounds like a D-104, just making the point that detail in a narrow bandwidth situation can be tricky and hard to optimize if the basic rules aren't observed.

EQing a neutral/flat response mic makes a difference. The mic is not about making the audio loud; it is about rendeing the sound of a person as if they were standing next to you with only minor enhancements to EQ, as you know. If loudness is one's only reason; then don't bother. You have missed the boat altogether, just get a D-104. EQing with the EQ that a mixer provides is also useless. You can never find the best sound that way. Never happen. The best way is with a parametric EQ; in a far second place the 31 band is next. Your spending for your project has also exceeded the budget that I proposed, and that is only too easy to do.

For those readers who are just reading about all of this - loudness is after the mic is made to ones tastes, so long as distortion is kept out of the picture. Always best to check it with a scope - to be certain. The real problem is getting the radio to allow a bit more bandwidth to milk more detail. We are talking about minutiae here, and the point is to get the concepts right before we start accumulating the equipment.

Your mic will be fine; not saying that it won't. But some detail was lost in order to boost; not such a big deal nor a deal breaker. Not a major problem unless you are recording. I'm sure you are happy with it. There are a number of people that use them and I think they have done a very fine job with them. Remember, this is all still much better than a stock mic, or a radio that is splattering across twenty channels due to over-modulation. No comparison.

Had to clarify some of your points for the readers; so don't think I was referring it all to you. I wasn't


BTW - MXL has also included a new lineup of broadcast mics. Both dynamic and condenser models. I thought that their version of the RE20 was all right for a dynamic; but I preferred the condenser as usual:

 
Last edited:
You are contradicting yourself, you want a flat response you say so you can EQ it,
"EQing a neutral/flat response mic makes the real difference"

But then you say "not having any peak is bad"? Not having a peak is a flat response.

But you have a problem with my point?

My point is partially based on the fact your info on ribbon mics isn't based on experience or true knowledge, just what you may have read or heard, Yet you are giving an expert opinion on this type of microphone and dismissed it's not just because of the fragile nature, but of it's audio performance being not want somebody would want for radio usage.

All I'm doing here was given out correct information on a specific mic that your first post failed to do.

Give people the correct information especially if you are being specific on something, then let them decide for themselves. That's what a forum is all about. This thread is heading towards a"my way is the only way" to do things.

Good luck!

73
 
Actually, I have gone to school for recording arts and had access to all of the top gear. Had a small but well appointed 16 track analog recording studio for awhile. Ran my own sound reinforcement company for mid-sized venues and worked with some major artists after that. Chose every stick of gear that was used and paid for it myself; was considered top notch, and my system was often copied but never duplicated by my competitors. Pink Floyd would have enjoyed it in its day. So, to say that I know my way around a mixing board and outboard gear is fair enough . . .

Ribbon mics are used in the studio. But not the first choice for a number of reasons. Unless there are some brass or some woodwinds to be recorded, or a female voice that is less than traditional, or if David Bowie should show up. It fills a niche at the discretion of the engineer or producer; but does not get the lion's share of the workload. Condensers and dynamics cover that still.

The fact that you don't grasp what I said might be my fault for not explaining in a way that was understood. So, let's try it again. OK?

All pro engineers are very picky about mic choice and EQ; it is their bread and butter. Amateur radios and CB's aren't nearly as unforgiving as the process that puts things down that commercial production requires. The bandwidth is narrower and the equipment is third rate in most cases. Which is still acceptable enough, so long as we keep important principles in play. But there must be a model as to what you want to accomplish. IOW; what is it that you expect? How do you get there? What are the problems that arise to that end? Having said that, a choice for eSSB or AM maul must be chosen first.

To keep it all in focus, those eSSB/maul choices are also beyond the scope and cost this series. Doesn't mean that experimenters won't come away with a far better solution that what the CB world has already provided. If done right, there should be a vast difference for the money and time spent.

The point is, just how much can one accomplish with a 5khz bandwidth? Given that a Cobra 148GTL has been modified to do 5khz, then one must be extra careful to use it wisely and still be on a budget. Compromises must be made; so what can be optimized, and what cannot be compromised?

Microphones that has less than a flat response are not bad in themselves. They often have places in which they are preferred. But that is for full bandwidth recordings; not for a narrow band. Fitting detail in a small space that sounds as natural as possible with just the right color can be interfered with if the EQ, compressor, or the mic gobbles too much of that available space. Kind of a delicate balance to attain; and to keep.

A mic that has a large peak, or even many such peaks, affects the sound product because to tends to pull adjacent frequencies to those peaks out of phase. This creates a dilemma to a real sound - as opposed to an accurate rendition. To correct it takes more EQ resources to correct than to have a mic which does not have the same problem. A D-104 will sound like a D-104 and a EQ can correct some of it; but not all of it. Leaks like a sieve. But a mic chosen that is flat, within a given budget, will allow the user to tailor it without wasting detail and correcting too many glaring peaks.

Nothing wrong with using a dynamic, condenser, or a ribbon. But to say that a ribbon is the best mic for a given situation - read 'cost' - it is not. Many low cost condenser and dynamic mics will work but will add color. All mics do - to some degree or another. But to have the best results, we really want to make the mic as neutral as possible - as cost will allow - so that we can color the finished product as we want to hear and not to be limited by any one factor.

That is all I've been saying, and I hope it is clear enough now . . .

 
Last edited:
One can use these mics; however they are used more often for female voices and instruments than for male voice characteristics. They tend to be strongest in the upper register of the spectrum, which we cannot use anyway. We need a mic that is flat between 20 to 3.5kc.



This is what you are wrong on. This is what I pointed out. I gave real world spec's, real world usage , and my own experience using this type of mic, and my opinions on EQ's and processing audio in radio service along with what I use. I'm not trying to persuade anyone into using or not using one at their station. The only thing you were and still are correct on is the delicate nature of these types of mics.

"They tend to be strongest in the upper register of the spectrum"

That is wrong! They are strongest from the lower spectrum thru the mids before starting to drop 5db above 1okz. which is in the range of the spoken and singing voice.

"We need a mic that is flat between 20 to 3.5kc"
I pointed this out that ribbon mics cover this frequency range with a broad flat response curve already. Below is the frequency response curve of my AEA R84 Ribbon mic showing a full range 20hz to 20khz. No mic is going to be completely flat like you suggest "We need".

0429.png



Below is spec's for a EV-RE20 mic for comparison. The frequency response for this mic is 40hz to 20khz. Notice how the low frequency response sharply drops below about 70hz at 0 degrees and even more at 180 degrees off -axis mic placement.

ev_re20_freq.JPG


"used more often for female voices and instruments than for male voice"

Says who, you? what legitimate source can you back up that statement...All the information given suggests it will and does work as well for male voices.

Ribbon mics are fine, you are right.
But they are more delicate and easier to damage than a dynamic



"Ribbon mics are fine"
That's a condescending assessment to a style of microphone you have been wrong about.

Again all my first reply post was to point out your incorrect and lack of information on a specific mic that you come off as being an expert on, yet you obviously never owned or used one, specifically in radio service.

Don't take it personally, just consider this important info on this specific type of mic that you left out as a contribution article to your thread, not an argument.

73
 
freq.gif


This is a graphic of another ribbon mic, not exacly flat is it? While your mic is outstandingly flat, it is not the norm. Nor was it inexpensive; was it? Remember, that this series was to give it a better sound and be affordable. A fact you have overlooked and continue to overlook in your criticism. One's pocketbook can be harmed if you go to the extreme that you have. Can we give it a rest yet?

I will admit that many new ribbon mics have a far better curve than they did some 20 years ago when I was in the biz, so I would recommend one today if it isn't too expensive. But that is the catch; isn't it?
 
Last edited:
  • Like
Reactions: dave457

dxChat
Help Users
  • No one is chatting at the moment.
  • dxBot:
    Tucker442 has left the room.
  • @ BJ radionut:
    LIVE 10:00 AM EST :cool:
  • @ Charles Edwards:
    I'm looking for factory settings 1 through 59 for a AT 5555 n2 or AT500 M2 I only wrote down half the values feel like a idiot I need help will be appreciated