Can someone translate/explain these measurements to me like I'm a child?

KMPLSV

Member
In my search to find anyone doing the old Ed Frias crossover mod for the BIC America DV62si Bookshelf Speakers, I contacted GR Research. In short, they explained to me that it wouldn't make financial sense to modify them to a degree where any improvement would be noticeable. Being very new to all of this audio stuff, the measurements that they sent me are Greek to me. Can anyone try to break any of this down to me like I'm a child? I'd appreciate it.


csd.jpg grill effect.jpg horizontal off axis.jpg IMG_7448.JPG IMG_7449.JPG impedance.jpg on axis response.jpg vertical off axis.jpg
 
Register to hide this ad
The answer that you're not looking for is to do some research and learn about loudspeakers and how they're measured. Here's one article, but there are plenty more:
https://www.soundandvision.com/content/speaker-measurements-101

I'll try to give an answer that you are looking for, very briefly.
The first picture shows the cumulative spectral decay displayed as a waterfall. Imagine you're looking into a room. The back wall of the room shows the frequency response. That's at "zero time". When the driving signal to the speaker is switched off, the speaker doesn't go silent immediately, it takes a few milliseconds to settle down. The 4 milliseconds after the signal is terminated is displayed on the graph as parallel surfaces coming forward from the back wall. Ideally, everything would quickly decay to zero (or -25dB as shown in the waterfall) but you can see in this case the initial frequency response has large peaks at about 7kHz and 18kHz, and those peaks take longer than the rest of the spectrum to fall to -25dB. The worst bit takes 2.7 milliseconds. Most of the rest of the spectrum decays in about 1.3mS.

The second picture shows a fairly straightforward frequency response plot. You can see the two large peaks in the high frequency response. I'm not sure why there are two plots. Left speaker and right speaker? MLS stands for maximum length sequence. The data at the bottom is telling you that he measurements were made in a period of 4mS.

I'll let someone else have a go at explaining the rest.
 
The 1st waterfall graph basically tells you about the "fidelity" of the speaker. A speaker that keeps moving for long after the signal was terminated is less accurate than a speaker that stops faster. Anyway we are talking about milliseconds, but that is what that graph shows.

The rest are freq response graps, the level at which each frequency is reproduced (actually the level captured by a microphone, since placing the mic at different points will result in different graphs). You have frequency on the X axis, dB on the Y axis. An Ideal speaker would reproduce all freqs at the same level, so you'd see a flat line. If you search for freq response graphs of reference studio monitors, o very well designed speakers (some designed here at AK), you'll see the response is usually very flat in all the spectrum, moving just some dB up and down (the famous "+- x dB" you read in the specs)

But, all those lines without a text telling what they are, mean basically nothing. Nothing you can read from those graphs. A graph like those needs a text reference, a text telling what thing was measured.

In the last pict, I see a graph with 2 loud peaks near 6KHz and at near 15KHz in a red line, and also a response with those peaks tamed (in green) but with a deep "valley" at 5KHz. Without a text reference, we don't know what those graphs are. Probably the original response, and the "new" response. But it could be another thing too, like measurements from different angles or different heights, or different distance.

The sixth pict is an impedance graph, it shows the impedance of a speaker at different freqs, in the vertical axis you have an "Ohm" scale.

Anyway, regarding the "mod", if a speaker has that non linear response, I'd buy a different speaker instead of investing $$ on them. Exception would be if you already listened to the modified version, and they sound that good, better than other speakers you could buy with the same money.
 
Last edited:
The 1st waterfall graph basically tells you about the "fidelity" of the speaker. A speaker that keeps moving for long after the signal was terminated is less accurate than a speaker that stops faster. Anyway we are talking about milliseconds, but that is what that graph shows.

The rest are freq response graps, the level at which each frequency is reproduced (actually the level captured by a microphone, since placing the mic at different points will result in different graphs). An Ideal speaker would reproduce all freqs at the same level, so you'd see a flat line. If you search for freq response graphs of reference studio monitors, o very well designed speakers (some designed here at AK), you'll see the response is usually very flat in all the spectrum, moving just some dB up and down (the famous "+- x dB" you read in the specs)

But, all those lines without a text telling what they are, mean basically nothing. Nothing you can read from those graphs. A graph like those needs a text reference, a text telling what thing was measured.

In the last pict, I see a graph with 2 loud peaks near 6KHz and at near 15KHz in a red line, and also a response with those peaks tamed (in green) but with a deep "valley" at 5KHz. Without a text reference, we don't know what those graphs are. Probably the original response, and the "new" response. But it could be another thing too, like measurements from different angles or different heights, or different distance.

Anyway, regarding the "mod", if a speaker has that non linear response, I'd buy a different speaker instead of investing $$ on them. Exception would be if you already listened to the modified version, and they sound that good, better than other speakers you could buy with the same money.
Good advice. But, there is always a but, if it's cheap, easy to do and easily reversed, why not try it? But that's me.
 
Talking about plot #2; I see two large peaks in the high frequency range that, IMO, really need taming.
They're clearly visible in the waterfall plot too.

Btw, the impedance plot (6th image) shows the speaker's impedance across the frequency spectrum. It shows the port is tuned to 70Hz.
I'm sure this will all mean very little to the OP and doesn't really help him with a crossover mod. If someone can find the circuit diagram for the mod he was looking for, that would be a big help and it would be fairly simple to make a new crossover on that design (though maybe not so simple for the OP).
Having said that, another thread suggested the crossover mod wasn't very good anyway. :dunno:
 
Good advice. But, there is always a but, if it's cheap, easy to do and easily reversed, why not try it? But that's me.
I think the point is exactly the cost of that "mod". The OP mentioned that he asked some place to do the work and they said the mod would be more expensive than the speaker.

It's a different matter if you DIY those tweaks. I've spend days and days tweaking crossovers, time not charged to a customer. Even when I do a mod for a customer, I usually do it when I find it interesting, investing much more time than estimated.
 
Last edited:
Sure you can make the speakers flatter with crossover mods, but once they get put into a room, that frequency response is going to look different anyway, sometimes drastically, and differing yet again based on where you are sitting.

Cheapest and best is to get a minidsp and calibration mic, put it in the tape loop, and that way if you move the system around, you can always retune and get it back to flat. It can knock down those two 9db humps without too much effort.

Otherwise, I side with the GR research people. Without knowing your room response, If I were them, I could not, and would not guarantee any improvement whatsoever over how the speakers sound right now.
 
Sure you can make the speakers flatter with crossover mods, but once they get put into a room, that frequency response is going to look different anyway, sometimes drastically, and differing yet again based on where you are sitting.
The room has most impact at the bass end of the spectrum. The obvious fault with these speakers are the two peaks at about 7kHz and 15kHz, which would suggest the crossover is at fault, relatively unaffected by the room.
 
The room has most impact at the bass end of the spectrum.
Agreed
The obvious fault with these speakers are the two peaks at about 7kHz and 15kHz, which would suggest the crossover is at fault, relatively unaffected by the room.
That speaker is a 2-way with a 6½" mid woofer and a ¾" dome tweeter. It's inexpensive at $118 per pair. I found no info about the crossover frequency, but I'd guess it's in the 2.5-3 kHz range. Those two large treble peaks are far above that crossover range. No modification to the crossover itself could fix that, although an LCR trap might suppress those peaks. I think the tweeter itself is the problem. Its difficult to tell from those graphs, but it might be going into break up as low as 5 or 6 kHz. No tweeter should do that.

So, GR Research was being polite and diplomatic in their response. To improve those speakers would require a pair of different tweeters plus new crossovers designed to allow them to work with the existing mid woofers. That might cost more than the original price of those speakers.
 
I found no info about the crossover frequency, but I'd guess it's in the 2.5-3 kHz range. Those two large treble peaks are far above that crossover range. No modification to the crossover itself could fix that, although an LCR trap might suppress those peaks. I think the tweeter itself is the problem...
To improve those speakers would require a pair of different tweeters plus new crossovers...
You might well be right, but the OP bought the speakers because he'd heard glowing reports about a crossover mod which would make them fantastic. I think he was asking for an explanation of the graphs in the hope that an obvious crossover mod would be revealed.
Personally, I suspect the original glowing reports about the benefits of the crossover mod were exaggerated.
 
With those speakers, that frequency response, and the op being a novice, I would just recommend turning down the treble via tone controls to where it becomes listenable. If that doesn't work, look for different speakers either new or used.
 
With those speakers, that frequency response, and the op being a novice, I would just recommend turning down the treble via tone controls to where it becomes listenable. If that doesn't work, look for different speakers either new or used.
I don't think the OP has ever mentioned what they sound like. I'm not even sure he's used them. The quote below is from a different thread by the same OP.

I have a pair of BIC America DV62si Bookshelf Speakers at the moment. Unfortunately, I haven't been able to find anyone around who still does the crossover modification for these speakers that Ed Frias used to do years ago either. This is extremely disappointing because the added quality of his mod I was hearing so much about is the main reason I purchased the speakers in the first place. I heard it really made them come alive...
 
Agreed
That speaker is a 2-way with a 6½" mid woofer and a ¾" dome tweeter. It's inexpensive at $118 per pair. I found no info about the crossover frequency, but I'd guess it's in the 2.5-3 kHz range. Those two large treble peaks are far above that crossover range. No modification to the crossover itself could fix that, although an LCR trap might suppress those peaks. I think the tweeter itself is the problem. Its difficult to tell from those graphs, but it might be going into break up as low as 5 or 6 kHz. No tweeter should do that.

So, GR Research was being polite and diplomatic in their response. To improve those speakers would require a pair of different tweeters plus new crossovers designed to allow them to work with the existing mid woofers. That might cost more than the original price of those speakers.
It's more likely a woofer breakup at that frequency. Just because there's a crossover frequency of 3000 doesn't mean a huge peak a single octave higher isn't possible, especially if there's only a coil on the woofer.
 
Back
Top Bottom