Decibel Meter Display

I purchased one of these units for my main listening system so I could get a visual indication of how hard I'm pushing my amps.

During television viewing, it rarely lights up (which is good), but during music material, it works well and it gives the system a visual activity added to the audible entertainment. It actually makes listening more fun.

It's connected from my processor outputs to my front channel amplifiers. It also has AC receptacles that I have my rear channel amp and cooling fans plugged into.

This is the unit I got: Technical Pro DB30 1U Rack Mount dB Decibel Meter Display+8 Outlet Power Supply

Just wondered if anyone else uses something like this.

 

I can't see how this doesn't negatively affect the sound of your system. A real DB meter uses a mic for input to read the sound level (pressure), in the air.
In my opinion. This is more like a VU meter.

 

Old school buffered VU meter here, with 0 to -15dB attenuation to deal with a variety of input gains.

 

Kinda reminds me of one of those old 80s boom boxes.

 

I was thinking of Jesse's stereo in Breaking Bad.

 

I always hated digital ones like this. I don't mind having some nice oldschool analog VU meters on amps though, they're kind of nice, AS LONG as you can turn them (and their little lights) off.

I guess I'm not trying to impress people with my meters.

 

The drawback on amp meters is that virtually all are calibrated for 8 ohms. If you can find an impedance graph for your speaker, you will see how it only covers the 8 ohm impedance & how limited it is for accuracy.

 

The unit simply uses RCA inputs and outputs, which I suspect are just a one-to-one jumper while it takes the signal for lighting the LED's. I never intended to rely on it as a true and accurate decibel measurement device. Actually, it has adjustment controls for adapting it to your particular system and I just set it to where I thought it was best adjusted. It's rather sensitive to peaks as it jumps into the red zone but I'm sure what it's reacting to is actual music level peaks. Unlike a meter where it's movement is more a buffered affect, LED's are very responsive.

Yes, it's sort of like a toy in one respect but I've found that when it's reading in the green, which is the midway level input, my system sounds great. If I push it harder where the red LED's are more constantly active, I know I'm pushing my amps too hard and I can hear they're being driven too hard too.

This is being used in conjunction with Outlaw 2200 amps and Heresy 3 speakers. I'm not sure whether it's the amps that start to sound harsh or the speakers not being able to take that much power. I think it's the speakers. Either way, this system really sounds fantastic. And like someone said, I'll hear things from these speakers I never heard before. After putting them on 20" tables, he was right. I also feel that these amps sound great too. How can they not? They are new, powerful and precise.

I wouldn't mind having a nicer set of analog meters but these suffice for the time being and they do what I expected.

Are analog meters still being made for this kind of use?

 

Yes, absolutely. Sifam make great VUs but you have to build the circuitry and chassis yourself. Or buy ready made. Dorrough also make great analogue meters. JLM Audio in Australia make great VU and PPM kits too:

JLM Audio Shop »

 

Those meters are just for display. If you want to do something to improve the sound of your playback, check this out:

Radio Shack 33-2050 Sound Pressure Level (SPL) Meter »

If you combine this sound meter with a test CD that has bands of sound played at specified frequencies, you can map the actual frequency response of your system in your room. This will enable you to better adjust your system and room to produce more accurate playback. (Be prepared to see the mid-bass thump that is common to many listening rooms.)

 

Let's look at the decibel another way.

"The decibel ( dB) is used to measure sound level, but it is also widely used in electronics, signals and communication. The dB is a logarithmic way of dscribing a ratio. The ratio may be power, sound pressure, voltage or intensity or several other things."

A decibel meter like yours is designed to measure changes in power from your amplifier, it does not tell you actually how loud your amplifier or the sound coming out of it is. It uses a logarithmic scale So if you are reading 75dB on your meter and you turn up the volume of your amplifier so that the meter reads, 85dB. you amplifier is now putting out ten times the power as it was when it was when the meter was reading 75dB.

Your sound level should be about twice as loud, to your ears. This still does not tell you how loud the sound was before or afterward's.

If you turn you amp up from 75dB to 78dB (+3dB increase), your amplifier is not putting out twice the power. Your sound field will appear about 1/3rd larger.

If you are using a decibel meter, with a microphone, you are measuring the actual sound level. If you are measuring a sound level of 75dB and you raise the and you turn up your amp until you are measuring a sound level of 85dB, you have doubled the sound level (as perceived by an average individual). In order to double the sound, you have to raise the power of your amplifier by a factor of ten (ten times the power).

One meter is measuring differences in power and one meter is measuring differences in levels of sound. In each case, they are both being expressed in decibel units.

 

For one thing, I can't even see what the decibel scale reads during operation. I'd have to put on reading glasses and move in close to actually see the scale. I'm just using it to gauge where my volume is at. I would really like a nice pair of analog meters that run off of the output of the amps though.

 

The output meters are usually calibrated for 8 ohms. Start looking @ impedance graphs for spkrs. Any deviation from 8 ohms cannot possibly be accurate. Ergo, output meters are by & large useless.

 

I can't find any analog meters anyway. There are a few of those old Realistic units on E-Bay , but they are cheaply made and they have RCA and screw type speaker connections. They only read up to 100 watts and it's not something I would tack onto my system., that's for sure.

 

Two things: Given that you are reading a dB scale. You usually have two options with a led digital type meter and one with an analog.

Pretend that you are looking at a sideways "S" type sine wave with a horizontal line running along the middle, dividing the top from the bottom. The top half represents the positive portion and the bottom represents the negative portion. The line itself represents time.

If we start on the left (the positive part) the AC signal begins to rise as time moves along. it will reach a peak, for a short moment and come back down to zero voltage. The peak only lasts for a brief period of time and does not represent the mean voltage (a term for mathematical average).



Take 117 VAC (Volts Alternating Current), from the wall. the 117VAC, represents the mean voltage, taking into the account of the high peak and the beginning and end part of the curve, where the voltage is starting to rise and starting to fall. If you were to measure the voltage at its peak, it would be over 140-volts. But it is only at 140-volts, for a very short time. On the graph above, it is represented as Vpk.

The dotted line, represents the mean voltage, the "real working voltage" and it is referred to as Vrms. Meaning; Volts - Root Means Square, RMS. When you measure voltage with an analog volt meter, it will be measuring RMS voltage, always.

If you use a digital volt meter, which, for our purposes can respond instantly, you can usually choose between measuring RMS and Peak Voltage.

The same will go for your digital dB meter. many people like the digital, because it can measure instantaneous changes. Meaning you can detect the ever so slightest bit of clipping and measure the Peak power. Others prefer more of an average.

You should check your manual to see how your unit reads, sometimes there is a switch to select it. Sometimes, it is just referred to slow and fast.

This type of dB meter (as opposed to the type with the microphone) is generally used for recording, live sound or broadcasting purposes.

If you are looking for the kind, with the analog meter, you probably are looking for a power meter, that measures your amp's output in watts, rather than a decibel meter. It will be giving you RMS values, which is how amplifiers are rated for their output.

Go down to an audio store and look at a McIntosh power amp with its signature "blue" power meters. It is calibrated along a logarithmic scale. The beginning part of the movement will be in .001 watts, then .01 watts. then 1 watt and so on. This is so the increase of power is shown evenly across the face of the scale.

The dB meter that you have is connected to the RCA's, while a power meter is connected to the output of the amplifier, rather than the preamp output.

Either way, you are just going to see a meter bouncing around or lights bouncing around. It is there to give you a relative meaning of the amount of power that you are using. It is hard to be more specific without seeing it.

Most analog power meters or dB meters are not that large. Unless you are up close to them, you are unlikely to see much of anything anyway.

Suggest you put on some highly compressed music, where the sound is mostly at the same level. Turn up your amp and make markings that you can see on your led display, from your chair, at different volume levels. Paint some coffee stirrers and tape them above your meters.

In your real world, that will work as well as anything else. I have an Emotiva XPA2, which is a two channel stereo amplifier, it has little LED's that I can turn on and off, they just give me an idea of how much power the amp is putting out. Most of the time, there is just one led on for each channel, unless I strt really turning the volume up.

XPR-5 Meter Demo | Emotiva Audio



The amp in the video is a 5-channel amp with vertical indicators. Mine is a stereo amp with that starts out with two LED dots in the center. One is for the left channel and one is for the right channel. As the power increases through the left channel, more dots appear on the left side and vice versa for the right. That is essentially what you are doing (I think!). (Best I can offer.)

 

That's all meters do is give you a rough guide.

 

If it's not considered to be hijacking the topic, could someone please explain what the use of the db power meters are on power amps? I've seen them on McIntosh's and other amps, and the majority of power amps don't have them. Do they have any useful function, or are they just decorative lights which would be equally as useful as a Christmas tree?

 

They are Christmas tree lights.

 

I can appreciate peak-to-peak and RMS voltage readings. I also realize how my LED array is only capturing the line-level output of my processor to the main amps. I really only wanted something in my system for a level reference rather than a true representation of what's leaving the amps. It would be nicer to have wattage meters, but as said, they're still only rounding the reading off minus, what would likely be, clipping signals.

My SAE has decibel LED's that are also scaled for wattage. An old Sansui 8080 I had used analog meters. I damaged a lot of tweeters with that receiver. They should have called it the Little Clipper.

I just updated my Dyanaco ST-400 and I wish it was the model with meters. Still, I doubt that amp even clips it's so ballsy. Same for the SAE 2400. Both of those amps have huge power supplies. As for my Outlaws, which I use the topic LED array lights on, they seem to get a little grainy sounding when they're pushed too hard. But with the LED's I can see where the peaks are going so I know when to back things off some.

But yes, they are like Christmas tree lights but they look pretty cool when music is playing and they do give me an indication where my levels are. I like seeing them bouncing around when I'm just sitting and listening to music.

 

Absolutely, back in the day, there were VU meters on all kinds of gear, then the trend was to remove them. One trend that I don't like about McIntosh is their glass fronts, to me, there is no point and my experience with glass is that it breaks. I like power meters, but with the glass only over the window of the meter.

On the 2-Channel Emotiva, the LED meter display being on one line, is not distracting as most of the time, there is just only one dot being displayed for each channel, when I do turn up the amp, I like to see the relative power being displayed. I am fine with that. The last three LED's on the far right and far left, are red, so you can clearly see when the amp clips and how far into clipping you are.

I have a three channel color organ with three Chinese lanterns run by a small Lepi amp, so I can adjust their overall sensitivity. I have a strip of LED light running along the top of the windows behind them. The lighting effects are soft and not disco like.

I would like the output meter one step further. I would like to see an external box that you can connect in parallel to the speakers terminals, that takes the signal and feeds it into a spectrum analyzer, that I could output to the processor and into the TV display.

I had an app on my smartphone for it a few years back, but a larger higher definition version would be nice. The app was in color. I like to be able to have it on the 60" TV screen. It's nice to be able to see the sonic content being displayed as the music is playing. When I hear a note, it would be nice to see what frequency that note is along with its harmonic content.

The Emotiva gives you the option to switch off the LED display, which is nice. Except for testing purposes, I wouldn't want to see a five channel display of LED's bouncing around, like in the video.

 

Back in the early 70's, when Quadrophenia came out, I hooked up my dad's Eico oscilloscope to the line outs of my stereo and we would watch the waveform as we partied. The first track of the rain was especially cool. Those were the days.

 

Touche'

 

Great little meter, got mine over a decade ago. Would never do any kind of shootout (AB, ABC, etc.) without. Any shootout that is not matched in SPL is worthless. I also use it to regularly remind me what 80 dB SPL sounds like so I am not blasting myself into deafness.

 

Yes! We had some great times w/ an oscilloscope back in the 70's- listening to and watching the music! My 1st "electric" experience was partially spent "watching" Yes' Tales from Topographic Oceans (which I hadn't been able to get into before, but have loved ever since), followed by "watching" some Firesign Theater, resulting in headaches from so much intense laughter.

Maybe we had a simpler scope- or just didn't know what we were doing (unlikely given the scope's owner was an electrician), but we saw no line inputs and had to use a speaker level input and could only hook up 1 channel- still gave great results though. Those were some wild waves in those Topographic Oceans! It often got so busy, though, even w/ just 1 channel. I always preferred the nice round bass waves to those spiky trebles that just flew by too fast.

Those experiences left me pining for something similar after the 70's. Some of the visualizations for Windows Media Player were pretty cool, but I've longed for something to use in my main system- love to be able watch the music on the big-screen. I don't know why no one has come up w/ a simple oscilloscope app for dvd or BR players to use for visuals.

 

MilkDrop for Winamp with the Shpeck wrapper for FB2K works a treat. There are some basic (and not so basic) scope presets for that.