Hitachi 3D80 strange EQ settings for flat response

I have been struggling to enjoy my 3D80 purchased recently and couldn't seem to get the EQ to sound right so i decided to use some test tones and a mic to calibrate the response of the boombox to a flat response across all frequencies. The resulting settings have made the sound quality much better but the actual EQ settings are not what i would have expected. I do wonder if the graphics printed on the EQ are a clue as to this odd behaviour. Here is a pic of the flat response settings. I would have expected the sliders to have been in a row across the middle. Could someone else with one of these verify they get the same improved result with these settings. 3D mode on and Surround off. EQ as below.

Sound is subjective which means that box is going to sound different to different people so a flat-frequency response is going to be different for two different people. The only way to really tune into a flat response is with a real time analyzer which shows you the frequency response you have and you can adjust the EQ accordingly until it shows flat.

JVC Floyd said:

Sound is subjective which means that box is going to sound different to different people so a flat-frequency response is going to be different for two different people. The only way to really tune into a flat response is with a real time analyzer which shows you the frequency response you have and you can adjust the EQ accordingly until it shows flat.

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I used a calibrated microphone and frequency generator (at all of the frequencies on the EQ and across the spectrum) which gave this result as the closest to flat when the levels were measured using a sound level meter. The resulting sound was actually fairly comparable to what id expect the sound to be like. Previously using the EQ as you normally would didn't get a result that was good. In fact id say it previously was terrible. I would never have thought to set the levels in this arrangement normally, feels like its against the grain.

Well we both know those graphs on eqs are a joke and usually the sliders end up in wonky position just to get the sound where you want it
, the method you used is the old tried and true method , an RTA is mainly used to compare frequency responses and for fine tuning.

JVC Floyd said:

Well we both know those graphs on eqs are a joke and usually the sliders end up in wonky position just to get the sound where you want it
, the method you used is the old tried and true method , an RTA is mainly used to compare frequency responses and for fine tuning.

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I used Excel lol. inputted all of the data before and after and generated some graphs as i made the adjustments. The same technique i used when setting up my home cinema system and sub crossover points. I just thought it strange that there is a graphic on the EQ that basically shows the adjustments I ended up with lol

It all depends where you're using it, and how loud you're playing it. If it's outdoors, then yeah you're going to crank it and cut the bass so it doesn't distort. But when I'm indoors, I always put the EQ into a V shape, with the middle slider at 0, on all my boxes. The only exception is my Telefunken, whose bass and treble knobs are almost TOO strong, lol

Flat means no cut, no boost. If you move the sliders that are at the bottom up and it increases the level, inversely if you move the ones currently on top to the bottom and it cuts the level, then obviously where you have it set is not flat.

Just because your ears tells you that the weird settings you have it at sounds best to you still doesn't mean that is flat.

Superduper said:

Flat means no cut, no boost. If you move the sliders that are at the bottom up and it increases the level, inversely if you move the ones currently on top to the bottom and it cuts the level, then obviously where you have it set is not flat.

Just because your ears tells you that the weird settings you have it at sounds best to you still doesn't mean that is flat.

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Yes i agree. The settings look completely wrong but i used a calibrated mic and sound level meter with a frequency generator to set it up to flat. Not my ears. The fact it actually sounds much better now is as much a surprise to me as it is you. The EQ looks wrong but the sound measures right. The first slider has to be set to max otherwise you don't get bass down to 50Hz.

Who said a boombox's 5 band equaliser set to 'flat' would equal a perfectly flat frequency output curve??

Google a RIAA eq curve, thats good to read.
Other advice is something another engineer over in the states mentioned and I never actually had thought of it; Modern music isnt over suited to the older box because the cabinet and speakers can't take it. everything is bass heavy and the moment you drive it too much, its distorted.

Other option is to set the graphic to all at the lowest setting and vary settings but keep them around the middle or zero. Try that.

jimmyjimmy19702010 said:

Who said a boombox's 5 band equaliser set to 'flat' would equal a perfectly flat frequency output curve??

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Well that is the assumption that you make with an EQ that Flat would be all sliders to the centre point. However in this case its all over the place but in a strange pattern that mimics the graphics to a degree. I just thought it was strange when i got this result. try it for yourself.

john3Ddub said:

Google a RIAA eq curve, thats good to read.
Other advice is something another engineer over in the states mentioned and I never actually had thought of it; Modern music isnt over suited to the older box because the cabinet and speakers can't take it. everything is bass heavy and the moment you drive it too much, its distorted.

Other option is to set the graphic to all at the lowest setting and vary settings but keep them around the middle or zero. Try that.

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All to the lowest setting wouldn't be a flat response, as you can see from my initial post, the sliders are all over the place when its properly measured.

The Line input on my 3D80 reduces the input somehow. When I first connect my phone, it plays loud, but then only half a second later, the volume drops a bit. I don't understand how it does that. And the LED meters refuse to blink more than 2 LED's on each side, no matter how loud my phone or iPod is set. When using the tuner, I can get 4-5 LED's on each side, consistently.

Reli said:

The Line input on my 3D80 reduces the input somehow. When I first connect my phone, it plays loud, but then only half a second later, the volume drops a bit. I don't understand how it does that. And the LED meters refuse to blink more than 2 LED's on each side, no matter how loud my phone or iPod is set. When using the tuner, I can get 4-5 LED's on each side, consistently.

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sounds like you have leakage to ground. Change the phone and cable, or replace the rca connectors on PCB.

The EQ circuit board has no influence on the line input level.
However keeping the sliders clean is always a good idea.

Helmar said:

The EQ circuit board has no influence on the line input level.
However keeping the sliders clean is always a good idea.

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Just wondering did you clean the EQ as when they great dirty they give you the wrong setting?

I cleaned everything - but never had troubles with the EQ board.