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

[mb91w126]

I got this covered.
auto-tune.

don't get them started back up with auto-EQ

 

[fourstringburn]

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?

Sorry to pick you apart but here goes...

"While your mic is outstandingly flat"

Alas! you now can see there are ribbon mics that can satisfy you, but it also just proved your shortcomings when you first assessed them as an expert on these and basically dismissed them as something not to use because of their bandwidth and frequency response. You were only right on their delicate nature and construction.

"it is not the norm."

What is the norm? there is no norm. You can research all types of the thousands of mics in each category and you can find different characteristics between many even in the same types. Your data on the RCA SK 46 proves this. If you research data on the RCA44 you will see it is very similar to my mic. Likewise if you research data on the RCA 77 you will see a difference on that one between the 44 and other mics.

When selecting a mike, one should research the data and determine if this specific mike suits their application. This is what your series is doing, however you need to make sure you are correct on your specifics since you are presenting it from an expert point of view.

"Nor was it inexpensive; was it?"

Yes! My AEA-R84 ribbon mic cost just over a grand, I think that's expensive and I think most people would agree.

"Remember, that this series was to give it a better sound and be affordable."

Yes it is and I don't have a problem with that. I did say already your posts does have a lot of good information, but I never suggested for anyone to use ribbon mics at their station.

"A fact you have overlooked and continue to overlook in your criticism."

I not really criticizing, I'm pointing out mis-information on your part and backing it up with real world info and experience on these mics only, there's a difference. Your responses show that you are slowly coming around and you seem to have a new appreciation for ribbon mics and you are even learning something new from it.

"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? "

See how you changed your opinion on these mics now, originally you thought they wouldn't work well because "We need a mic that is flat between 20 to 3.5kc." now you learned otherwise! Even the vintage RCA 44 mic has a similar curve to modern ribbon mics and that mic dates back to the 1930's. These mics like many others have different spec's from one another so that's why you can't assume all ribbon mics have the same "curve" between the vintage to the new ones.

"One's pocketbook can be harmed if you go to the extreme that you have."

"so I would recommend one today if it isn't too expensive. But that is the catch; isn't it? "

Yes your pocket book will take a hit. That is one of the main reasons I never suggested these types of mic for anybody. They are expensive even though there are some Chinese import cheaper models, but if you prefer better quality then that's the catch, yes.

"Can we give it a rest yet?"

No! not till you admit most of your initial assessments on these mics were incorrect.



Read your previous quotes below...

"Ribbon mics"

"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"

"One can use these mics; however they are used more often for female voices and instruments than for male voice characteristics"

"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"


I guess Elvis doesn't fit your assessment, yet those early Elvis recordings are still regarded as one of the best vocal sounds captured and still haven't been truly duplicated. Notice the RCA 44 mic in the pic.

Since we are talking about radio and ribbon mics...


Wouldn't that vintage RCA mic below look good at your station?

Now for the Hammies...

And here's my little radio station...

Nice collection of vintage and modern ribbon mics wouldn't you say!

 

[fourstringburn]

Since you have a more extensive knowledge of pro audio including mics of all types ( ribbons aside, ha ha ) There is a new mic by Neumann.

This is a condenser mic and is part of a new broadcaster series and the spec's look good and has a really flat response curve thru the 20hz-20khz region. This is specifically marketed towards broadcast radio.

Typically Neumann mics are expensive and this one is no different selling for around a grand. They also make a dynamic version( which is a first for Neumann) and it's a couple hundred dollars cheaper.

Any experience on this mic?


Here is a link: http://www.neumann.com/?lang=en&id=current_microphones&cid=bcm104_data

 

[Shockwave]

Hi-Fi has been an interest for me since I got my first FT-101 and plate modulated it externally with a pair of 4X150D tubes in 1985. Since then I've purchased or built compressors, limiters, 20 band EQ's, downward expanders, De-essers, Electrovoice mics, Sure mics, Kenwood radios, Yaseu's and Icoms, putting them all into Hi-Fi use.

While I still have the rack full of Hi-Fi gear directly modulating an RF stage in my Kenwood, my views on how to achieve Hi-Fi on CB have changed dramatically in the last few years. Today on 11 meters I use a Cobra 142GTL with a D-104 plugged directly into the front mic jack. The D-104 has gotten a bad rap for sounding too tinny or having too much treble without good bass response.

I'm going to make a statement many will disagree with but, a good D-104 crystal element is a Hi-Fi mic. Look at the size of the element and relate it to good bass response. The trouble is the equipment after the mic element. Mostly the radios we use but in part the pre amp in the amplified D-104 is somewhat lacking but still very good when connected to a radio that can pass Hi-Fi.

If money is to be spent in any area to achieve Hi-Fi, it is best spent in the radio first. I'm not sure where the idea that CB radios have a response from 100 cycles to 3000 cycles came from but that's not accurate. Having swept the modulator stages of many, I can tell you very few even reach 250 cycles before hitting the 3db down point. With that roadblock in place, you will be spending too much on outboard equipment trying to flood more bass into the TX that will just produce distortion before getting down below 100 cycles.

Extensive testing has shown me that the best bandwidth to strive for on AM is between 50 cycles and 5000 cycles. Unless everyone you talk to has their receivers modified to pass more bass, anything lower than 50 cycles is wasted power. Anything more than 5000 cycles has the same effect but causes significant adjacent channel interference too.

The D-104 easily reaches 50 cycles and way over 5000 cycles which depends on the radios high frequency negative feedback loop to keep it within reasonable bandwidth limitations. The common PLL MB-8719 board has two mic amps, the 5 watt audio IC and the series pass modulator. Four stages that each need to be addressed to unlock their Hi-Fi potential. To do that requires between 10 and 15 parts being changed depending on the particular board used as there were several variations between models.

Once you do that the radio is capable of the bandwidth but still not appropriate to be directly driven by any microphone. Dealing with communication grade equipment presents it's own unique obstacles when trying to go Hi-Fi. The end result is about half of those we hear using this equipment sound very good while the other half have persistent distortion in the bass that makes them sound "muddy".

This distortion is usually centered around 250 cycles, right around the stock rolloff point on most rigs. We are attempting to boost the bass below this frequency significantly and need to do so in a way that prevents excessive gain in the 250 cycle range. The typical EQ cannot boost 150 cycles without causing an increase at 250 cycles. This is where a parametric EQ becomes handy by allowing you to target a particular frequency that is problematic.

With the parametric EQ dialed in I swept the bandwidth again. The results showed a 6 db boost between 60 and 150 cycles with a huge 20 db cut at 250 cycles. Flat response from 500 to about 2000 cycles where a small spike in gain occurs and then back to flat before rolloff at 5000 cycles. Since the D-104 already has the small peak around 2000 cycles, the wheels began to turn.

It became apparent that only three more circuits would be required to produce the frequency response that previously required large outboard equipment or a PC software program to provide. Since the D-104 has enormous extra gain those tone shaping circuits could also be passive and avoid all inside noise and RFI susceptibility.

The first two circuits were independent bass and treble controls to define the desired bandwidth and gain at each end. The third circuit was a bit more complicated. What was needed was a notch filter that provided a variable frequency control with an attenuation level that is adjustable to below -20db. Those 3 circuits all fit on a small PC board about the size of a book of matches with 4 potentiometers to adjust the ranges. It installs between the mic jack and mic gain control.

You see where I'm going with this? Suppose there was a "kit" available that came with the board, all parts required to Hi-Fi the 8719 radio board and a video showing the exact traces on the back of the PC board that you add about a dozen parts to? One must be removed from the board on the top side.

Is there a demand for such a kit if it were guaranteed to produce exceptional Hi-Fi results from nothing more than a Cobra and a D-104? Building the boards and creating a user friendly video will be a time consuming process that carries an expense but it would still fit into the suggested $300 window. Approximately half of the parts added to the main PC board provide another unexpected benefit. They open the receiver bandwidth to match the fidelity of the modified transmitter.

That brings me to a final thought. We often hear people ask why bother to go Hi-Fi since no one has a Hi-Fi receiver to notice the difference. Utter hogwash. Most people think because the specs say the receiver is good from 300 to 3000 cycles, that's it. The reality is these are the points where the human ear can just barely detect a reduction in volume at the given frequency. They still hear much lower and higher than this but not at the full gain or volume. Even when listening on the most restricted receiver, a Hi-Fi transmitter is quite noticeable.

 

[Robb]

Apparently, you are a bit obsessed with your ribbon mic.

fourstringburn said:
"No! not till you admit most of your initial assessments on these mics were incorrect."

I wouldn't hold your breath. The small exposure to ribbons I've had was a mixed bag. Some sounded just fine, while others had a nasty out of phase tone. Back to the shop.

Ribbon mics are just too expensive for this project; what is it about that - that you don't understand?
Cost is a major factor.

However, a MXL large capsule condenser mic can be had for $100/less/new and cheaper than that if purchased used.
Flat for cheap.

If someone wants to use a ribbon mic, I'm not stopping you nor anyone else; wouldn't dream of it. Got a lot of green just burning a hole in your pocket? Then, spend it where you want. It's your money.

But be aware - that all ribbon mics are fragile; more fragile than other mics. The ribbon itself also need to be tensioned correctly so that it sounds right. They can be inconsistent. That is what you fail to understand. Not really done by the end user. Studios send them out to maintain them or else they may not work correctly. The better ribbon mics use a very thin ribbon, which is even more fragile.

If someone wants to DIY, or just need to understand what we are talking about:

 

[fourstringburn]

Apparently, you are a bit obsessed with your ribbon mic.

fourstringburn said:
"No! not till you admit most of your initial assessments on these mics were incorrect."

I wouldn't hold your breath. The small exposure to ribbons I've had was a mixed bag. Some sounded just fine, while others had a nasty out of phase tone. Back to the shop.

Ribbon mics are just too expensive for this project; what is it about that - that you don't understand?
Cost is a major facto

"Apparently, you are a bit obsessed with your ribbon mic."

Yes, because they are worth mentioning but with correct information, what part of you being wrong with your initial assessment don't you understand? I explained 3 times and you finally came to agree with your later posts if you re-read your responses.

"I wouldn't hold your breath. The small exposure to ribbons I've had was a mixed bag. Some sounded just fine, while others had a nasty out of phase tone. Back to the shop."

No I won't hold my breath when someone can't admit they were wrong. It is clear to all who bother to read this how you changed your assessments on these mics after learning that they aren't how you first described them.

Now you finally admit you had some exposure to some but you never said that in the beginning when I first mentioned it was apparent you never owned or used one, Hmm!


"Ribbon mics are just too expensive for this project; what is it about that - that you don't understand?"
"Cost is a major factor"

We covered that over and over and I never argued that point, AGAIN, it's your initial assessment of these mics that you were incorrect on. That's what I initially and still challenge you on! What part of that do you still not understand.

M0GVZ made some good points on his posts regarding your assessments on radio bandwidth and mics, why haven't you challenged him???

I'm starting to assume you have more knowledge on pro audio since you do have some vocational education in this area than you do in radio communications.

While pro audio and radio communications are related in many ways, it doesn't automatically qualify you as an expert in both fields.

 

[ExitThirteen]

My setup is real simple. I made a couple small capacitor changes in the mic audio circuit and in the actual audio circuit (TA7222AP) on my President Madison (MB8719). I run a Shure SM-58 studio mic on a boom. Just enough to open up the bandwidth a little. I get great reports with it.

No need to go crazy with trying to expand TX audio bandwidth, you'll start overlapping into the next adjacent channel. Motormouth Maul is a great example of this.

All said and done, never hurts to open it up a little, but really, a good mic is all you'd need. And since everyone's vocal coverage is different, you'll need to find the right mic that matches your voice. It really IS that simple.

Not bashing on anyone, just an observation is all.

~Cheers~

 

[Robb]

"Ribbon mics are just too expensive for this project; what is it about that - that you don't understand?"
"Cost is a major factor"

We covered that over and over and I never argued that point, AGAIN, it's your initial assessment of these mics that you were incorrect on. That's what I initially and still challenge you on! What part of that do you still not understand.

M0GVZ made some good points on his posts regarding your assessments on radio bandwidth and mics, why haven't you challenged him???

I'm starting to assume you have more knowledge on pro audio since you do have some vocational education in this area than you do in radio communications.

While pro audio and radio communications are related in many ways, it doesn't automatically qualify you as an expert in both fields.

>yawn<
No; ribbon mics are too fragile and just not worth the expense, a lot like your arguments.

 

[Shockwave]

That MB8719 board is one of the best and most capable boards I've seen. It's too bad we have to go back 20 years to find quality worth investing time into. Most newer radios are not using discrete transistors for the mic pre amp stages today. They have gone the short cut of using an 8 pin op amp IC as a pre amp. Even when that IC circuit is modified, it doesn't sound as clean as the two transistor pre amp stage found on the 8719 board. It probably would improve if the op amp were switched out with a quality low noise FET op amp.

I've also had good results with the SM-58. The only part that surprises me is that you don't mention using an EQ. I've found it was very difficult to clean up the 250 cycle range without some reduction in gain at this frequency. That could be anything from reducing the mic gain to the notch filter I mention. There is more than one way to skin the Hi-Fi cat.

 

[ExitThirteen]

Shockwave,

I do have a Behringer 31 band active/passive EQ that I've experimented with, but in all honesty, it's overkill and unnecessary. I'm not trying to re-invent the wheel or anything, but just trying to optimize what I have. I'm not trying to go crazy with it, just open it up a little so it sounds pleasant out there on the band. While there is still some gain loss in the 250hz area, the mods I have implemented with the Shure mic showed noticeable improvement when I swept it. I figured it was plenty good for me. So far, between my asymmetrical modulation mod on AM and the audio tweaks, people tell me I sounds really nice on the air. I'm happy with what I have.

~Cheers~

 

[Robb]

I like the SM-58. The SM-57 is also a fine, inexpensive mic. It uses the same element as the 58; the difference being the spherical pop filter in front on the 58. Vocalists like the SM-58 and asked for them when doing live sound. I liked subbing the EV ND-757 mic in its place, as it was just an all-around better mic. Hypercardiod, high output, less feedback, and a better overall freq response. Cuts right through in the mix.

EQing the 58 cheaply is another cost problem. But a parametric is best to keep phase anomalies to a minimum. Another is to make/use an impedance box (very inexpensive), which can shift the freq response to your liking. Better off with the parametric; but a 31 band will work for radio - IMO . . .

 

[ExitThirteen]

Reason I think the EQ is overkill is because of the fact that I'm still using the radio's mic/audio circuits. If I were to direct inject my audio, then things change dramatically. By using the radio's audio circuitry, you're still going to be limiting how much audio bandwidth you pass. You can only polish the turd so much... but it's still gonna be a turd when you're done!

That's why I'm happy with just the SM-58 mic. It seems to match my voice well, and bring up the lower end without sounding too flat. Besides, I'm stupid, so the KISS principle works good for me.

~Cheers~

 

[Robb]

Even if you open up the mic circuit to get the widest response, the filter will still determine the overall width. Goes for direct injecting too. Thing is, that filter is not a brick wall, as it rolls off. I've seen my 148 with a wider 455khz filter roll of close to 100hz on the low end to 4khz on the high end with the caps mod done to the andio circuit (about 10 caps) with the SINAD real-time audio analyzer. Same is true for my Uniden Grant, and either radio gets glowing reports. That isn't enough to bleed over into another channel, unless there is negative clipping anyway.

Personally never done direct injection into a 148 or a Grant; but did it with the Kenwood TS-2000. But the direct injection is far easier than changing out all of those little caps timewise. And you ain't no dummy, Exit, you do solid work!

 

[Shockwave]

We must remember that CB radios are high level modulated in the driver and final RF stages. Long after the IF strip where crystal and ceramic filters are used. Therefore these filters have no impact on the TX bandwidth like they do in a low level IF modulated HF rig. The filters would only be affecting the upper end of the bandwidth anyhow with no effect on the AM bass. All of the TX bandwidth is determined by the value of capacitors used in four AF stages on the 8719 board..

 

[Robb]

We must remember that CB radios are high level modulated in the driver and final RF stages. Long after the IF strip where crystal and ceramic filters are used. Therefore these filters have no impact on the TX bandwidth like they do in a low level IF modulated HF rig. The filters would only be affecting the upper end of the bandwidth anyhow with no effect on the AM bass. All of the TX bandwidth is determined by the value of capacitors used in four AF stages on the 8719 board..

Thanks!
Good to know.