Quad Subs?

Unless your room is huge you'd probably be better off selling the Velodyne's and just use the XS15's. Integrating disparate subs is not always the easiest thing to do, so why take a chance of compromising the sound provided by your new subs?

Why not take advantage of your rare opportunity to experiment? Most people will never own a single capable subwoofer, much less four of them, at once.

Four subwoofers is the optimum number to utilize in your home theater.

Contrary to what you might think, it’s not about getting louder bass. By using multiple subwoofers, you can greatly increase the room’s modal density, largely filling in the peaks and dips, giving a smooth, articulate bass sound. This improves the overall consistency of bass response from seat to seat.

Dr. Floyd Toole has been an invaluable asset to the sound reproduction industry and has devoted a great amount of his life to understanding how sound propagates in a home environment*. Todd Welti did a lot of experimentation with subwoofer placement, numbers, and bass sound quality. The resulting whitepaper on the topic was a culmination of countless tests and acoustical models of playing with multiple subwoofers in different locations in a room to improve bass response over a much wider listening area. In the end, Dr. Toole and Todd Welti concluded that the most ideal scenario for bass reproduction is to have one subwoofer located at the midpoint of all four walls. This configuration displayed the least amount of variation in bass response from seat to seat. Alternately, four subwoofers can be used in each corner.

Do you have a way to EQ and measure? With multiple subwoofers (especially when mixing and matching differerent subwoofers) in order to get the most from them you will want to measure them and you will want to implement EQ.

I would probably grab something like this mic:
http://www.minidsp.com/products/acoustic-measurement/umik-1

And then use REW (which is free). This is pretty much all plug and play with a Windows or Mac system. This will help you measure the response in your room and your system. But you will still need EQ

Audyssey is not bad at all but if you need to EQ mutliple subs that are not of the same performance/make/model you are not going to get that with Audyssey. You would most likely want something like this:
http://www.minidsp.com/products/the-product-concept

With different performing subwoofers, you are going to have to tweak them so you are not overdriving one set to try to keep up with the other set which can have negative results. There are lots of ways of doing this but just plugging in two different sets of subwoofers that perform differently is probably not going to give you the best response. If you bought four identical subwoofers, it would be a lot easier I suspect

So just buy two more XS15's and you are all set

I'm running four budget subs in my HT setup.
Two ported and two sealed.

Ran the full eight position Audyssey MultEQ XT32 with Sub EQ HT calibration.
I was amazed at the final results.
Audyssey seamlessly blended all four subs together so well.
I never knew my four cheap subs could sound and "feel" so good together.

XT32 and Sub EQ HT are pretty slick, you still need a way to measure so you can compare both before and after Audyssey results.

I wish more receivers under $1K had these features... Very few do..

I keep reading that it's difficult to integrate different subs as opposed to the same subs. Is there any data to back this up? Has anyone run tests to verify this?

Think about it. Say you have one sub that can play clean (little distortion) to 25hz and another sub that can only play clean to 30hz before it starts distorting. Based on my own experiences with trying to integrate two different performing subs, you end up with distortion and ill effects from the lesser sub trying to keep up. Putting in something like a high pass filter on the lesser sub at 30hz via DSP/EQ would most likely help and result in clearner bass 25-30hz.

Let's be precise with the vocabulary. An "EQ Device" adjusts different frequencies to make all the frequencies equal. An SPL meter is a "Calibration Device" in that it helps set the overall level of all the speakers and subs to be the same. Calibration is different than EQ. In another thread previously I described why your technique of using an SPL meter to reset the levels after running Audyssey is flawed. You need to understand the difference between calibration and EQ to understand why your technique is flawed. Would you like me to explain it again?

Craig

The analog one is better.

 

You must have a strange dictionary if it confirms to you that a SPL meter is some form of EQ device. SPL stands for Sound Pressure Level METER. The full Oxford English Dictionary is the definitive guide to the use of the English language and it defines a meter as:

 

"Any apparatus for automatically measuring the quantity of something passing through it. In extended use: a device for automatically measuring the amount or intensity of something (as distance travelled, speed, brightness, or sound intensity), or the amount or cost of a commodity or service used."

 

The same resource defines an EQUALIZER as a device which is:

 

"Designed to modify the frequency response of a circuit (as a transmission line or an amplifier), esp. in order to compensate for frequency-dependent attenuation or phase shifts."

 

So the SPL meter measures something and the Equalizer modifies something.  Two entirely different things. I suspect you do realise this but can't now back down because your argument would be entirely destroyed ;)

The Beeman Audio Dictionary gets another entry How many times does this have to occur before you take a step back, realize you are incorrect and that audio science isn't going to alter it's terminology to fit your "beliefs".

Same thought for your utterly flawed "flawless" sub balancing technique - Craig John explained the issues in detail and yet you press on.

And to complete the trifecta, also wrong about 50 hours of break in time for sub drivers. I'd ask to see the measurements you refer to, but given your history with REW, doubt they are viable.

 

 

Oh FFS. It is a METER and a meter MEASURES. An Equalizer ADJUSTS or MODIFIES. Give up - you're making yourself look silly.

 

 

You are giving your own meaning to "equalize". An Equalizer to everyone else is something that modifies a set of frequencies. A meter measures, an equalizer modifies. End of. You said "your use of the English dictionary" requires you to disagree - but you didn't actually use a dictionary to look up 'meter' and 'equalizer' did you?  If you had, then you would have seen the results I posted above, from the OED, for you.

 

 

 

Changing the relative levels of subs is NOT equalizing! Equalizing is changing the frequency response. Look, you made a mistake in terminology - it isn’t the end of the world. Recognise the mistake, learn from it and move on. 

 

 

 

 

It's not a question of what I think an SPL meter is - it is defined by the most authoritative reference on the use of English language that exists in the world today - the full version of the OED. I have given you those definitions of a meter and an equalizer and they are not in line with your own interpretation, opinion or belief. 

 

You edited out the part where you said I was disrupting the thread - but I don't see it that way. I am trying to help you understand what the difference is between a sound meter and an equalizer - until you do, you cannot make any meaningful contribution and you are also using flawed methods to set your system up, which others are trying to help you with so you get it right and thus improve your SQ.

OK, let's reset the discussion and start over. I can understand your logic that an SPL meter helps you to "equalize" the levels of the speakers. However, to then call it an "equalizer" is an unconventional usage of the term. The conventional use of the term "equalizer" is a device used to equalize the frequency response. These are "equalizers":





These types of devices adjust the levels of different frequencies so they are all equal. There are several types of equalizers: graphic, parametric time-domain, and they use different types of filters: "Finite Impulse Response filters, (FIR), and "Infinite Impulse Response" filters, (IIR.) These filters can be fixed frequency, (graphic), or they can be adjustable frequency, (parametric.) The width of the filter, (the "Q"), can be fixed or adjustable. In the world of audio, these devices a commonly known as "EQ's" or "equalizers." An SPL meter is a totally different animal.

Your use of an SPL meter to "balance" the levels of the speakers is known conventionally as "level calibration." This is the process of setting the broadband SPLof all the speakers and subwoofers so they are the same at the listening position or listening area. Also involved in "calibration is setting the individual delays so the siganls all arrive at the listening position at the same time. This entire process is known as "calibration." In addition, there is one more process involved in audio system setup... setting the Bass management settings, i.e., deciding which speakers need crossovers, and what the optimal crossover frequency should be. All three of these processes are performed by Audyssey during it Room Correction and Setup. It may be confusing to you, and you may be lumping them all together as "EQ", but they are, in fact, 3 separate and distinct processes.

You are welcome to define these terms any way you want. However, if you want to be *understood*, and, more importantly, if you don't want to cause others confusion, you would be better served using the terms conventionally. Here is an example of the confusion caused by your unconventional use of the term:

You misunderstood him and we all misunderstood you. If you had use the terms conventionally, everyone would have understood each other.
Using the receiver's test tones to set levels bypasses Audyssey's EQ. The Audyssey EQ adjustments are out of the circuit when the receiver's internal tst tones are played. Therefore, the impact of the frequency response adjustments are not accounted for when you use the internal test tones and your SPL meter to adjust the levels post-Audyssey. Here is an example of what can happen when you do this:

Audyssey:


No Audyssey:


The receiver's test tones are limited to 40 to 80 Hz. Look at the levels of the response from 40 to 80 Hz in the first graph and the levels from 40 to 80 Hz in the second graph. I've drawn red lines to show the average response. Note that the average response without Audyssey is about 3 dB lower than the average response with Audyssey. If you used the 40 to 80 Hz test tones and the "without Audyssey" response to set the levels, you would need to raise the response 3 dB to equal the response with Audyssey. However, when you re-engage Audyssey, it will add 3 dB on top of that, and now you'll be 3 dB too high.

This is just an example, and the results in your system will depend on what Audyssey does to the frequency response. Nonetheless, it is incorrect to use the receiver's test internal tones and an SPL meter to reset the levels post-Audyssey.
Actually, you do have the ability to adjust the delays for each channel, including the subwoofer output. In fact, this is the one parameter than can often be improved upon post-Audyssey. However, it takes measurement capability and the knowledge to interpret the graphs to know how to make the adjustments. I'm not going to go into that here, but you can find some info in this thread:
http://www.avsforum.com/t/759877/seaton-sound-submersive1/4500#post_19450333
Of course, that's only if your "intellectual travels" take you to a place where you want to actually learn something.
A frequency response graph and a waterfall graph of the time domain response are much better for visualizing the in-room acoustics than an RTA.

Here is an RTA of my system:



And here is a frequency response and time-domain waterfall.:


There is a lot more information in the second graph than the first.

Craig

Craig, just curious how you would recommend going about EQ'ing quad subs that are not identical and offer different performance characteristics?