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PostPosted: Wed Mar 09, 2016 12:04 pm 
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I have recently installed a pair of subs to augment my Magnepan 3.7s. Yesterday I plotted sound levels at the frequencies recorded on the Rives Audio Test CO 2. I found that I have significant sound level boosts at the following frequencies: > 50hz peaking at 63 hz <80 hz ; 250hz - 500hz ; 6.3khz - 10th. There are big volume reductions at: 125hz- 2 50hz ; and, 500hz- 1000hz. How do I find the culprits?


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PostPosted: Wed Mar 09, 2016 12:33 pm 
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How significant? 1-3 dB is pretty normal. Above 6 dB and what you'll be hearing is fairly coloured.

I would check out the crossover points on your speakers. I'm pretty sure the boost in ~50-80Hz is common all but the smallest Magnepans.

No room will play flat. But your room is the biggest culprit followed by about a hundred other small things. Still, I wouldn't sweat a few dB +/- at all. In fact most sub 500Hz frequencies take some heavy treatment to absorb. Even then you may like the sound much less.


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PostPosted: Wed Mar 09, 2016 12:52 pm 
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Can post an image of your graph for frequency response? Also, what is your room like - dimensions? Furnishings? What's on the walls? What subs did you get? Where are they placed? What is the XO frequency? Are the 3.7 running full range?

If you haven't done so already, look into bass traps in the corners of your listening space (between the wall-wall junctions, obviously, but also the ceiling-wall junctions and floor-wall junctions)

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PostPosted: Wed Mar 09, 2016 1:14 pm 
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Room is 18 x33 feet. About 60% has 10 ft ceilings rest 8 feet. Subs are 10 inch Gallo Acoustics


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PostPosted: Wed Mar 09, 2016 6:03 pm 
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Thanks for posting the photo, but it's difficult to read the frequencies on the left. The frequency response does seem "peaky" and it's probably gonna look much worse when using a 20-20kHz sweep (instead of fixed frequency tones).

As the system seems to be in a dedicated space, you're lucky that you have the freedom to add bass traps, and critically placed diffusion. Before going that route, which I believe is critical, you can experiment with moving your listening spot forward or back - maybe 6" either way smooth things out, it maybe be that one or three feet will do it.

You may need to recalibrate the subs' phase, and maybe their location though there is a nice and smooth look to the way they are set now.

You may also want to look into a digital EQ. These were once looked down upon in the audiophile world, but now many are using them as the final frontier to nirvana.

In my space I found that moving the Maggies forward/back relative to the front wall had the biggest impact on the bass response, as did the use of 6" bass absorbers on the front wall. 6' away and the bass was too lean (but the imaging was special); 2' away and the bass was strong but the stage compressed way too much. I've settled on 4' as having the smoothest response at my listening position.

Having some tall plants just beside the speaker (ribbons are out for me) helped the top end sparkle smoothly.


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PostPosted: Wed Mar 09, 2016 6:48 pm 
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I've tried a different photo in which the frequency values may be easier to see. Also wanted to note that I'm using the filter in the subs to limit sound frequencies in the Magnepans to those over about 75hz.


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PostPosted: Wed Mar 09, 2016 6:51 pm 
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Bob0398 wrote:
Room is 18 x33 feet. About 60% has 10 ft ceilings rest 8 feet. Subs are 10 inch Gallo Acoustics


Wow, that looks more like an impedance curve. Exactly how did you arrive at that measurement, ie microphone type, placements, number of samples, source, averaged, weighted etc.


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PostPosted: Wed Mar 09, 2016 6:55 pm 
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you should leave your magnapan full range and just add the sub with x over point of about 60 hz, also your 2 sub are close to the side wall. move them around.


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PostPosted: Wed Mar 09, 2016 7:17 pm 
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Have you fully assessed if your current subs (unspecified ) the actual culprit and a poor match in your system causing you to fret?

The link below and article extract is one of the best reads on the issues of introducing subs into a two-channel system.

http://ultrafi.com/why-everybody-needs- ... subwoofer/

Why Everybody Needs a Good Subwoofer……And Why a Really Good Subwoofer is so Hard to Find

Audiophiles and music lovers are missing out on one of the most dramatic improvements they can make to their audio system: Powered Subwoofers. Most audiophiles won’t even use the word “subwoofer” in public, let alone plug one in to their precious systems. There is a kind of snobbery that exists in the world of high-end audio aimed primarily at receivers, car audio, home theater and especially subwoofers.

As a matter of fact, subwoofers are responsible for many people disliking both car audio and home theater, since it is the subwoofer in both of those situations that tends to call attention to the system and cause many of the problems.

The truth of the matter is that subwoofers have fully earned their bad reputation. They usually suck.
Most of them sound boomy, muddy and out of control with an obnoxious bass overhang that lingers so long as to blur most of the musical information up until the next bass note is struck. We have all had our fair share of bad subwoofer experiences, whether it’s from a nearby car thumping so loud that it appears to be bouncing up off the road, or a home theater with such overblown bass that it causes you to feel nauseous half-way through the movie. You would think that high-end audio manufacturers would be above all of that, but you would be wrong. In many cases, their subwoofers are almost as bad as the mass-market models because they too, are trying to capitalize on the home theater trend that is sweeping the land.

You see, it’s very difficult and expensive to build a good subwoofer. One reason is that a sub has to move a tremendous amount of air, which places big demands on the driver (or drivers). Moving lots of air requires a lot of power and that means an amp with a huge power supply, which can cost huge money. Finally, in trying to move all of this air, the driver (or drivers) which operate in an enclosure, create tremendous pressure inside of the box itself. The cabinet walls must be able to handle this pressure without flexing or resonating. Building such a box involves heavy damping and bracing which gets very expensive. When you consider these requirements, you quickly realize that it is virtually impossible to build a really good subwoofer (I mean good enough for a high-end music system) for under $1000. Yet most of the subwoofers out there sell for between $500 and $900. Manufacturers do this because their marketing research has shown them that that is what people want to spend on a sub, never mind the fact that what people want to spend and what it takes to get the job done right may be two different things. The result is that even most high-end manufacturers are putting out poorly constructed subwoofers that just don’t sound very good.

I don’t want to give you the impression that anyone who really wants to can build a good subwoofer so long as they are willing to throw enough money at the problem, because that really isn’t true either. There are some pretty expensive and well-constructed subwoofers out there that you would never want to plug into your music system because they would most certainly make the sound worse.

Why? Because of their crossovers.

A crossover is inserted into your signal path in order to remove the lowest frequencies (the deep bass) from your main speakers so that they no longer have to do all of the dirty work. The deep bass will instead be dealt with by the subwoofer. The #1 benefit of adding a high quality subwoofer to your system is not how it further extends the bass response, but how it can dramatically improve the sound of your existing power amp and main speakers from the midrange on up. That, my friends, is by far the most compelling reason to add a sub to your high-end music system. Once your main speakers are freed from the burden of making deep bass, they will sound cleaner, faster and clearer, especially in the midrange and midbass. They will also image way better because there will be far less air pressure and therefore resonance and vibration affecting their cabinet walls. And since the power required to make the deep bass is provided by the subwoofer’s built-in amplifier, your main power amp will be free from that burden and begin to sound like a much more powerful amplifier. The one big problem with all of this is that you need a crossover to roll off the deep bass in your system and achieve all of these benefits. And the crossover that comes with almost every subwoofer on the market will cause more damage to your signal than can be overcome by these benefits. That is the main reason that audiophiles refuse to consider adding subwoofers, even very expensive ones with well built cabinets.

Enter the Vandersteen 2Wq 300 watt powered subwoofer.

This is the only subwoofer that is specifically designed to be inserted into the highest of high-end music systems without doing any harm to the precious signal. So how does Vandersteen do it? Simply. In fact his crossover scheme is so ingeniously simple that it’s a wonder nobody else thought of doing it the same way. I’ll spare you an in-depth description and just say that the only thing you end up inserting into your system is a couple of high quality capacitors. That’s it, nothing more! No additional wires or gadgets enter your signal path. Hell, you don’t even have to disconnect the wire between your amp and speakers to add this subwoofer. The model 2Wq sub uses the same basic crossover scheme as the $15,000 flagship Model 5As. As a matter of fact, you can even run the specially designed Model 5A crossovers (M5-HP) with the 2Wq if you want the most transparent sound imaginable.

So what about the other reason to add a subwoofer to your system: for more powerful and extended bass? I don’t care how big your main speakers are, they’re no match for a good subwoofer in the bass.

A really good subwoofer can run rings around the best floorstanding speakers when it comes to bass extension, power and control because it is designed to be good at that and nothing but that, whereas main speakers have to be good at higher frequencies as well. Ideally, you want two subwoofers so that you have true stereo separation down deep into the bass.

Stereo subs can also help to lessen room interaction problems by providing two discrete sources of bass information. Remember, if you can’t afford to buy two subwoofers at once, you can always add the second one later. Adding a pair of 300 watt powered subwoofers is exactly like adding a pair of 300 watt monoblock amplifiers to your system and upgrading to a pair of better main speakers at the same time. The beauty is that you don’t have to replace your main power amp or speakers to do it.

But there is a problem here as well. Everything comes at a price, and the price you pay with most subwoofers is that when you add them and their built-in amplifiers to your system, they don’t tend to blend or integrate well with the sound of your power amp and speakers.

This is especially true if you own a tube amp, because the character of your amp is nothing like the character of the big solid-state amp that is built into most subwoofers. The result is that your system sounds split in half. You can hear where one part of the system leaves off (namely your amp and speakers) and where the other part takes over (the sub and its amp). This is a HUGE problem for audiophiles who aren’t willing to destroy their system’s coherence for additional power and bass extension.

Fortunately, Vandersteen has the perfect solution for this problem that is, again, so simple, I wonder why nobody else thought of it first. His solution is to build a very powerful 300 watt amplifier that strictly provides the huge current needed to drive the subwoofer. You can think of this amplifier as only half of an amplifier; or just the power portion of an amplifier. The release of this power is controlled by the signal that is provided by your power amp. Vandersteen’s amplifier needs a voltage to modulate its current output, and what better place to get that voltage than from your main power amp? This way, your power amplifier is directly responsible for the sonic character of the deep bass coming from the subwoofer because it provides the necessary voltage signal. This voltage signal contains the unique and characteristic sound of your main power amplifier and insures that that character is maintained in the sound of the subwoofer itself. The beauty of it is that your amplifier is only providing a voltage reference and no actual current, so it is not taxed with the burden of “driving” the subwoofer in any way. As a matter of fact, your amplifier doesn’t even know that the sub is connected to it. The 2Wq’s potential is almost unlimited given that it will ratchet up its performance as you improve your power amp. Remember that you always want your subwoofer to sound just like your power amp. No better, no worse. NO DIFFERENT!

After having spent time with the amazing Vandersteen Model 5A loudspeakers with their 400-watt powered, metal cone subwoofers, we were reminded of the sound we had with the awesome Audio Research Reference 600 mono power amps. With the Ref 600s there was a sense of effortlessness, openness and unrestricted dynamic freedom that we have only otherwise heard with live unamplified music. Listening to those monstrously powerful amps made us realize that all other systems sound compressed by comparison. Only when we heard the new Vandersteen Model 5As with their hugely powerful built-in subwoofers, did we again have a strikingly similar sonic experience. The reason is that the Model 5As provide a total of 800 high-quality watts, to which you have to remember to add the power of the amp we were using, the ARC VT-100, at 200 watts. This means we were listening to about 1000 total watts of amplifier power – not far from the 1200 total watts provided by the Ref 600s. With the Vandersteen subwoofer crossover and amplifier, you are able to get those hundreds of subwoofer watts to blend seamlessly and even take on the character of the ARC VT-100. It’s amazing! What’s even better is that the price of the system with the Model 5As and the VT-100 is under half the cost of the Ref 600s alone! Since this discovery, we have achieved the same kind of unbelievable dynamics and seamless blending with ProAc loudspeakers and twin Vandersteen 2Wq 300 watt powered subs. So, if you want the sound of Ref 600s but cannot afford them, buy a pair of Model 5As or your favorite pair of ProAcs plus a couple of 2Wq subwoofers and mate them with a VT100 and you’ll get surprisingly close. You can cut the cost even further by running a pair of Vandersteen 2Wq 300-watt subwoofers with your existing speakers. Or mate a pair of 2Wqs with your favorite ProAc. In any case, it is the magic of SUBWOOFERS that allows this to happen. It is for all of the above reasons that there is only one subwoofer in existence capable of integrating seamlessly into a high-end music system, allowing you to reap all of the benefits of having a subwoofer, with none of the drawbacks. And the Vandersteen 2Wq is the one. And just in case you think I am a biased source, our correspondent Blaine Peck (who, for all you know is also a biased source) recently wrote the following, with no discussion between us about the topic prior to his sending us his comments. Whether reproducing the plucked string of an acoustic bass or the sound of an analog synthesizer, the Vandersteen 2Wq subwoofer is a seamless extension of any system. Nothing else need be added! With its internal 300-watt power amplifier, it is the perfect compliment to any sound system. Designed to take on the characteristics of your main stereo amplifier, the amp in the 2Wq will not sound foreign in your system. Also, through an extension of the Vandersteen design philosophy, a unique gradually sloping crossover system is implemented so you simply do not know where your main speakers stop and the 2Wq begins.

Now that your main speaker/amplifier combination need not concern themselves with those power demanding low frequencies, they are freed up to work in a more comfortable range. Yes, now what is coming from your main speakers will sound better than ever.

The 2Wq is not just another subwoofer. It consists of three 8″ floor-facing drivers, each with a massive motor. So why not a more typical single 12″ or 15″ design? Well frankly, the mass of a larger driver will not allow it to respond as quickly as the Vandersteen 8″ drivers to today’s demanding recordings. The 2Wq’s 8″ drivers are designed to handle the content but be “fleet of foot” at the same time. Concerned about where to put them? You need not worry. With the control of both its respective level and the “q” (how loose or tight the low end is) you have the flexibility to place them in a location that fits your living environment and not sacrifice performance. The simple beauty of this product will soon become an addition to your room.

So whether on orchestral music, hard rock or something in between, the Vandersteen 2Wq will exceed your expectations.


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PostPosted: Wed Mar 09, 2016 8:09 pm 
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The subs have been placed where, when I was exploring where to site them, they sounded best, most often, to me with the two or three pieces of music I was using at the time.

Can zon001 tell me why I should use the Mags full range?

Gunner suggests that an article I've already read will reduce my fretting. Perhaps a second read will do something but given that I don't feel fretful, it's not likely to have much of an impact at all. What I'd like to know has little to do with frets and much to do with my practical search for suggestions of what I might try in my room to smooth out some of the peaks and valleys in the curve, using the best information I have, that describes the sound levels now being produced at a variety of frequencies.

I'm open to exploring easiest, cheapest options first.


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PostPosted: Wed Mar 09, 2016 9:27 pm 
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Few things I don't understand:

Why are there 2 curves on each graph?

Why haven't you optimized (measured) the speakers in the room without the subs, before complicating things by adding the subs?

Why would you have the subs on stands?


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PostPosted: Thu Mar 10, 2016 3:02 am 
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Gotta love the short wall.

Gunner, great link.

Marc mc


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PostPosted: Thu Mar 10, 2016 3:23 am 
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Bob, run your measurements again WITHOUT the subs connected, and have the Maggies full range to see what they can do. The measurements shown indicate that the subs don't really seem to be having much impact - below 60hz is quite below reference.

Although Magnepan doesn't provide TS parameters for their drivers I suspect the Q of the bass drivers is about 0.2, maybe even lower. Not many subwoofers are going to have a response quick enough to keep up with them at frequencies above 80hz. The LOWER the frequency at which you can bring in the sub the better since sub-bass is actually quite low, right?

Do you know what types of filter is built into your Gallos? You've selected 75h as the XO point but what are the slopes like? I would suggest to try the XO at the lowest setting and then tune from there but not before measuring the Mags full range response.

It will be more efficient to download the REW (Room EQ Wizard) software instead of what you're using now. Not that there's much wrong with what you're using, but REW is simpler and faster to use, and graphs are generated automatically. A 20-20K sweep can take only 10 seconds (but use a slower rate and take multiple sweeps for each measurement).

-- 10 Mar 2016 06:24 --

Oh, and show us a curve for the stereo response.

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PostPosted: Thu Mar 10, 2016 3:57 am 
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Bob0398 wrote:
I'm using the filter in the subs to limit sound frequencies in the Magnepans to those over about 75hz.


That seems really high to me.

I set my XSP-1's crossover to 50hz, everything below goes to the paradigm active servo 15", and everything above to the main speakers.

I experimented with different settings but this worked best. It tamed a bass boom problem with the mains.


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PostPosted: Thu Mar 10, 2016 4:32 am 
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The curve that starts more to the left plots the sound with both subs and maggies operating. The one that starts two frequency intervals to the right is of the Maggies alone. This afternoon I will try to get a better picture of the graph.


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