FR Graph of BOTH Speakers vs. Ave Speaker and What to Do About It

[mike w]

Hi AV NIRVANA: I should have asked this question before I bought a DSP but better never than late.

The protocol is to measure each speaker individually and then to average for an complete response. John M explained that there would be a boost in SPL when measuring both speakers as compared to measuring a single speaker. You can see this effect in the attached graph. Here is the question: Why is there a SPL boost from 100 Hz on up and not from 100 Hz on down? This matters because when I look at the average (fat line), I see a falling slope with too much bass but for the BOTH line it’s relatively flat (although lumpy). I eq’d the average line, attenuating those peaks by 5 & 6 dB and got closer to a typical room curve. I expected the sound to be leaner but it seemed too much was subtracted in the foundation of the music to me. If I evaluated only the BOTH speaker graph, I would not have taken eq action. Which graph should I focus on (besides the waterfall one)?

Mike

 

[Matthew J Poes]

Above the Schroeder frequency we are primarily measuring the direct signal and classical concepts around doubling sources and power give fairly classical increases in output. The room isn't impacting things very much or at all.

At low frequencies the room is dominant. You aren't measuring the speaker but the room after it's been energized by the speaker. The sound is in a steady state meaning it's already multiple periods and has bounced off numerous wall surfaces before reaching the mic. These measurements will always show evidence of the room modes. As such you won't see classical increases anymore. You start to see something that is very room and frequency dependent.

There are other possible causes as well such as bass management redirecting bass to both speakers. A subwoofer producing all the bass, etc. None the less what you show is consistent with my first mentioned concept.

See this article on multiple subwoofers. It would apply to any low frequency source.

http://data-bass.com/data?page=content&id=80

 

[Matthew J Poes]

Oh and as for measurements you should measure tust one speaker at a time and take multiples in different locations around your seating area. Average all of those and EQ. For the most part you want to apply the same EQ to each speaker. Anywhere below 200hz I would definitely apply the same EQ to each speaker based on that averaged measurement. I usually then go back and retake the same measusements after EQ. I interpret them individually and as an average. The average should be smooth and the individuals shouldn't look any worse.

You shouldn't be using measurements of both speakers at the same time for assessing the room or making corrections. John was telling you the same thing.

 

[Matthew J Poes]

Oh one last thing, an ideal EQ curve for a response is not flat. It's smooth but you want a boost of 2-3dbs or more at the lowest end and about 3db down at the highest. A lot of speakers might struggle with too much boost but 3 db should be ok as long as you don't boost below the speakers lower limit.

 

[mike w]

Thanks MJ for your quick and thorough response. My focus is now on modest room treatments (mixed use room). I sold the DSP. My Classe’ Audio preamp output voltage is over the recommended input limit for the miniDSP. (Something I should have checked before I bought it.) The miniDSP developers said it could lead to saturation although I didn’t notice that. In the end, I didn’t want that nagging spec mismatch in the back of my mind nor did I want to mod my preamp or get a new one.

I have read about the benefits of multiple subwoofers but I'm not sure about that solution. It would be different but I don't know how much better. KISS is still the over arching engineering principle. I know people use subwoofers with Sonus Faber Cremona Auditor M's speakers but I like simple.

 

[Matthew J Poes]

Thanks MJ for your quick and thorough response. My focus is now on modest room treatments (mixed use room). I sold the DSP. My Classe’ Audio preamp output voltage is over the recommended input limit for the miniDSP. (Something I should have checked before I bought it.) The miniDSP developers said it could lead to saturation although I didn’t notice that. In the end, I didn’t want that nagging spec mismatch in the back of my mind nor did I want to mod my preamp or get a new one.

I have read about the benefits of multiple subwoofers but I'm not sure about that solution. It would be different but I don't know how much better. KISS is still the over arching engineering principle. I know people use subwoofers with Sonus Faber Cremona Auditor M's speakers but I like simple.

SUBWOOFERS ARE AUDIOPHILE!

I literally was just thinking about that as a topic. It's a huge misconception that simpler is better when it comes to bass. We may argue all day long about the benefits of one amp over another. 33% placement vs golden ratio. There is likely no right answer to such arguments. What we can't argue about is good bass because that's one of those topics for which a very objective notion explains all of the subjective (well unless we start making stuff up). That is, bass sound quality is 100% a function of the LF source and room interaction. There are a lot of concepts in this hobby I'm willing to be open minded about, but this is one where the science and subjective experience is so overwhelming that I take a hard stance.

If we start with the premise that bass sound quality comes from accuracy, meaning a flat or at least smooth response and low distortion, then there is no way to argue that using the mains as the only Lf source is the most audiophile approach. That's because the mains should be placed out into the room, often a meter or more from a wall. That causes SBIR, interference in the bass from reflections off the front wall, ceiling, side walls, and floor. That's bad for bass and can't easily be fixed. You couldn't provide enough absorption to totally fix that nor would you want to.

All bass that you hear has already traveled the world (your room) and back again before reaching your ears. What I mean is that the bass has bounced around your room walls many times before you ever hear it. Very little is direct from the sub. The room has imparted it's fingerprint on the sound dramatically. All subs in a small will be essentially omnidirectional and relatively flat in response. It's the room the causes all that horrific distortion.

The primary differences between subwoofers or speakers in terms of LF reproduction is extension and peak output. This is another area were subs can be optimized in ways that mains can't so that they have more extension and output at lower distortion. That means better sounding bass.

Multiple subs allows you to more evenly excite the room modes in a way that makes for smoother bass over a larger area. It adds dynamic range, reduces coloration, and reduces distortion.

Multiple subwoofers is a far more audiphile approach than any other because there is simply no other way that can provide the same level of improvement in bass quality. It IS KISS, because there simply isn't a simpler way to achieve the same results.

So as you can see I take a pretty hard stance on this. You want the best sounding bass, you must use subwoofers and you must use more than one, really more like 3 or 4.

Now that doesn't mean I think everyone can or should do this. I get it, we all have our own tastes and opinions. It's your system so do what you are happiest with. In addition because it is a complicated approach that requires knowledge and tools to setup right you certainly can do more harm than good. But...if you want the best bass possible, subwoofers are a must.

I know what I've written is my opinion but it's an opinion based on a lot of research by a lot of different people, so it is not an opinion I came by lightly.

 

[mike w]

I'm not going to dispute your view that multiple subwoofers can do a good job managing room modes. I'd be on the losing side of that argument. I've read a few papers by Toole and Welti in addition to on-line advocates like Audioholics.

Two or three good subs is almost the cost of an aftermarket power cord ($5K) ;-) which is not trivial for me. You did notice that I said I listen in a mixed use room which is code for needing my wife's approval for several big boxes ;-) Lastly, integrating those units is not trivial. I have a room mode at 96Hz yet if I do a cross over that high, I will likely be able to identify the subwoofer as a sound source. Not good.

I am a big fan of Franco Serblin, the designer of my speakers. His view is quoted below from a Stereophile interview. He found the search for perfect bass futile. "When you want more bass, you miss it; when you have it, it disturbs you."

Having said that, I may yet try two 10" subs to see if this is indeed Av Nirvana.

 

[Matthew J Poes]

I'm not going to dispute your view that multiple subwoofers can do a good job managing room modes. I'd be on the losing side of that argument. I've read a few papers by Toole and Welti in addition to on-line advocates like Audioholics.

Two or three good subs is almost the cost of an aftermarket power cord ($5K) ;-) which is not trivial for me. You did notice that I said I listen in a mixed use room which is code for needing my wife's approval for several big boxes ;-) Lastly, integrating those units is not trivial. I have a room mode at 96Hz yet if I do a cross over that high, I will likely be able to identify the subwoofer as a sound source. Not good.

I am a big fan of Franco Serblin, the designer of my speakers. His view is quoted below from a Stereophile interview. He found the search for perfect bass futile. "When you want more bass, you miss it; when you have it, it disturbs you."

Having said that, I may yet try two 10" subs to see if this is indeed Av Nirvana.

You are right, the integration isn't trivial at all. I've seen a lot of people who had bad luck and totally wrote it off. I'm ok with not doing it, but I do get a little bothered when people dispute its validity based on their experience. You have to acknowledge the possibility you did it wrong before dismissing it. The science behind the notion is so sound that its just can't be disputed with a bad experience.

My hope is that in time room setup devices which include correction like Dirac are able to automatically provide integration and optimization for more than 2 subwoofers. JBL had such a device at one point but it didn't last. I never saw it in action. What is needed is a setup software that you input your room design and it gives you suggested subwoofer locations for smoothest bass. Then takes measurements and creates appropriate delay, level, and EQ. This is what I have to do manually and what is so difficult for most people to get right. Doing it takes a ton of time. I can easily spend 6-8 hours doing this. That isn't reasonable for most people. The first time I did it and got it right, I honestly thought I was doing something wrong. I sent an email to Dr. Geddes asking if this was right and he told me it takes him that long as well.

That's why my view is, you want audiophile bass, as is perfect reproduction of low frequencies, you need a well designed and treated room, optimally placed subwoofers, and EQ. You want something that can still sound very good with a lot less complexity, well then certainly there are other options.

I have heard the argument of reducing bass to avoid bass problems before. I get it, it's works, you can get used to listening that way. I still like bass and feel its worth having a full range system to spend the time to integrate the subs.

Ok now as for the subs, I'm not saying having multiple good subs is a bad thing, but bass reproduction is very different from frequencies above the room's Schroeder frequency. I don't want this to be mis-interpreted, but...basically the sub can be a lot lower quality and still provide excellent bass. The primary difference between a cheap 12" sub and a high end 12" sub is extension and peak output, and for a 12" sub, the differences would be small. What that means is that a handful of inexpensive 10" or12" subs can be fine for providing excellent bass. Most subs will be very linear within their range. A lot of people react negatively to that view because we have all experienced that terrible subwoofer that sounded boomy or distorted easily. Which is true, subs that are poorly designed or exceeding their linear range will sound bad. However, if the sub has a flat response (the vast majority of them do), has low distortion within their linear range (nearly all do), then you just need 3 subwoofers that you won't overload during music and movies. Movies typically need more subwoofer than music, so if you mostly or only listen to music, you can get away with lesser subs. A handful of $200-$300 subs can do wonders with even a $10,000 speaker. It sounds like you might have Sonus Faber Speakers? If so, many of the mid to smaller range speakers from them would be somewhat bass limited and output limited allowing you to get away with some smaller good subs. Unfortunately small, good, and cheap don't go all that well together.

Are there any dealers in your area that let you do in home trials? Maybe you could see about getting a demo with a handful of subs?

 

[tesseract]

I'm not going to dispute your view that multiple subwoofers can do a good job managing room modes. I'd be on the losing side of that argument. I've read a few papers by Toole and Welti in addition to on-line advocates like Audioholics.

Two or three good subs is almost the cost of an aftermarket power cord ($5K) ;-) which is not trivial for me. You did notice that I said I listen in a mixed use room which is code for needing my wife's approval for several big boxes ;-) Lastly, integrating those units is not trivial. I have a room mode at 96Hz yet if I do a cross over that high, I will likely be able to identify the subwoofer as a sound source. Not good.

I am a big fan of Franco Serblin, the designer of my speakers. His view is quoted below from a Stereophile interview. He found the search for perfect bass futile. "When you want more bass, you miss it; when you have it, it disturbs you."

Having said that, I may yet try two 10" subs to see if this is indeed Av Nirvana.

There is absolutely no downside to including a properly integrated subwoofer or more to an audio system. Only gains!

Multiple subs need not cost the price of a $5k power cord. Subs will certainly make an audible difference several orders of magnitude over a power cord, though.

Two capable 10" subs would enhance the experience greatly, and adding contemporary DSP correction, like the Dirac Live Matthew mentioned, can help tie in the system, room and listening position.