Raylock
As a pending new owner of a SubMersive I am trying to identify the EQ tools which would be most helpful to me.  I am new at this hobby so one requirement is that it not be too difficult to understand and use but one which hopefully will still be useful as my knowledge grows.  The tools I have considered so far are the SMS-1 and the R-DES.
Ray

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MikeDuke
Those are probably the easiest ones to use.  I have a DSP30, but that is only because I had mark do my setup.  Other wise I probably would have gone with the velo.  I know mark thinks the velo is a bit limited because it is somewhat in accurate below 15Hz
I simply love this stuff.
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Mark_Seaton
Hi Ray,

While you didn't ask it exactly, I will first note that there isn't anything unique to a SubMersive that requires the use of EQ.  Almost any subwoofer will be subject to similar acoustic problems and can benefit from EQ.  With the added headroom and in-room extension of the SubMersive over many competitors, there will certainly be cases where there will be more room for subjective improvement with the SubMersive.

The Velodyne SMS-1 is the turnkey solution.  It is a bit more expensive than other options, but you also don't need a PC to run it.  The trade offs come in the flexibility of the EQ, the detail seen in the measurement, the ability to save settings to a file, and an internal high pass to the unit that is approximately -10dB @ 10Hz even when set to "5Hz".  In enclosed rooms, this will limit the ultimate extension of the SubMersive.  In most rooms using the SMS-1 will be much preferred over not.

Other products out there require you do perform the measurements.  I suggest looking through the Room EQ Wizard forums at http://www.hometheatershack.com for more help on what is required to run this free program.

The AV123 R-DES unit is a bit more expensive, but has a rather intuitive interface that clearly shows the combined response of the filters and 4 easily selectable presets with simple RCA in/out.

I'm generally not a big fan of Behringer products for many reasons, reliability being one of them, but their cost makes them nearly throw-away when they break.  Home users have been much more fortunate with reliability than pro-sound users for which the devices were intended.

The Feedback Destroyer series are very inexpensive, with a very cumbersome interface.  There is a midi connection that can allow control of the unit through the Room EQ Wizard software.  This makes it much easier to use.

The Behringer DCX2496 is a very useful piece and while often out of stock, they can be had for ~$250.  This offers much greater flexibility in EQ options, including shelving and high/low pass filters and even limiting or dynamic EQ.  It can be controlled via Serial cable with its own software.

The QSC DSP-30 (related to it's wall-wart module cousins) is a very reliable and flexible unit, who's cost has risen over time to around $500.  Its setup is entirely open, drag-n-drop, with 8 pre-sets available via a front panel toggle switch.  This unit also has many features including more parametric filters than you will need with shelving and high/low pass filter options.

Both of these last two units have the ability to use 2 (QSC) or 6 (DCX) outputs to drive other subwoofers or devices like shakers if you like to use them.  The ability to separately high/low pass and delay secondary subwoofers and particularly shakers can be quite useful in optimizing their performance.

More than anything else, sorting out how you will be able to measure the in-room frequency response is the first and most important hurdle.
Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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JimP
Mark,

I see that the spec on the DSP-30 shows a bottom frequency of 20hz. 

In questioning QSC, they say it goes beyond that.

In your experience, can you effectively go below 20hz and if so, any side effects?
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Mark_Seaton

JimP wrote:
Mark,

I see that the spec on the DSP-30 shows a bottom frequency of 20hz. 

In questioning QSC, they say it goes beyond that.

In your experience, can you effectively go below 20hz and if so, any side effects?


Hi JimP,

This is a fairly common trait to most of the DSP based EQ's on the market.  The main thing you have to check with some is what sort of low frequency throughput the electronics have.  In other words, when no filters are applied, how does it roll off the low end?  All DSP based products will at some low frequency.  There has been some documentation online, and Ilkka has tested quite a few units now; maybe he can chime in.  Long ago I did contact QSC and then sent me an AudioPrecision measurement of the very low frequency extension, and going by memory, it was about -1dB to -2.5dB down at 10Hz.  This is fine, especially if the device has shelving filters.

You can download the software for most and look at the interface without having the physical EQ connected.  You will find it is common that they simply limit the numerical input in the software.  There are some issues that can come in with very low frequency filters, but most companies have done a plenty good job with the design such that taking a few measurements to adjust for what is really happening vs. what you expect makes it a non-issue. 

So far as actually applying and using the filters, you will see in the DSP-30 software that the very small graphic display does extend to 10Hz.  All of the filters will have effects centered on the entered frequency, and will extend below 20Hz just fine.  Shelving filters will greatly affect >20Hz, and often an additional PEQ in the 20-25Hz range can shape the exact effect.  Another "trick" is that Bessel filters of 12-24dB are shallow in their initial roll off.  This can be used in combo with a low shelving filter or even PEQ to produce an effective low corner that is well below 20Hz.  One aid in setting up such filters where the display doesn't show them well down low is to scale them by a factor of 10.  So move that 20Hz filter to 200Hz, and experiment with other filters also set above 200Hz so you can better see what is going on to 10Hz or below.  Once you see a desireably shaped response, just enter the intended frequency of each filter by dividing by 10.
Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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Buzz3
I have seen RDES units in the AV123 classifieds for $200.00 to $250.00 range if this helps you any.  Drunkonjack is asking $225.00 shipped for one now.  I have to hook mine up and start playing with it now that my wife has a new laptop.  Good luck, hope this helps.  Here's the link to DOJ's classified.

http://av123forum.com/showthread.php?t=22451
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JimP
Mark,

I'm having difficulty deciding between the Behringer DCX2496 and QSC DSP-30 for a system having dual subs set at different distances.

Excluding ease of setup, does the DSP-30 give you anything in terms of features or sound quality that the Behringer doesn't have?  Cost difference of $250 ish  isn't a concern as I'd rather go for quality and get it right this time. 
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dave
JimP wrote:
Excluding ease of setup, does the DSP-30 give you anything in terms of features or sound quality that the Behringer doesn't have?


The DSP-30 gives you peace of mind.

(incendiary rant mode on)

Behringer is a company that's done an incredible amount of damage to their own reputation. They've learned how to make some decent gear on their own in the last few years, but they've been sued and sanctioned for literally stealing other company's designs in the pro world for a over a decade, and they've done it flagrantly. They copied mixer and compressor designs from Mackie and DBX so literally (while putting their own name on the front) that their name is worse than mud in a lot of pro circles. These days they're content to borrow design ideas and industrial design cues and put cheaper guts into the boxes of a lot of products.

They've also been fined as recently as 2006 by the FCC for selling untested/nonconforming products in the US.

I don't have any particular personal malice toward them, the things of theirs I've used have performed as well as I've expected them to, but as an engineer in real life, I have a big problem with their business practices, and their current...how shall I say...homages to other manufacturer's products. They've built a reputation as thieves. That just doesn't fly with me.

(rant mode off)
This is not a sig. This is a duck. Quack.
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Ilkka
Mark_Seaton wrote:
There has been some documentation online, and Ilkka has tested quite a few units now; maybe he can chime in.  Long ago I did contact QSC and then sent me an AudioPrecision measurement of the very low frequency extension, and going by memory, it was about -1dB to -2.5dB down at 10Hz.  This is fine, especially if the device has shelving filters.

I just posted this on HTS.

Frequency responses are levelled at 100 Hz except for SMS-1 and R-DES which don't have a fully by passable low pass filter. The SMS-1 had the newest v2.12 software and 5 Hz, 6 dB/oct. subsonic filter setting was used. DSP1124P is known as the older BFD (though not the oldest which is the DSP1100), and FBQ2496 is known as the newer BFD, which seems to have the least low frequency roll-off of them all. I will soon mod the Cleanbox to find out if that improves it.


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Mark_Seaton
Thanks for posting that here Ilkka.  I'll see if I can get someone at QSC to send me a measurement taken with the AudioPrecision setup they have there.

For those just realizing that all electronics are not equal in this regard, IMO EQ for my SubMersive should be less than 5dB down at 10Hz, preferrably less than 3dB down.  Filtering and the use of wider band parametric filters and shelving filters make this amount of roll off a small relative concern.  As you can see though, the SMS has a very significant roll off at 10Hz which while not a major issue in more open floor plans, in enclosed or especially sound-isolated rooms, the reduction in output can be noticable.

In spite of the above, the interface and integrated measurement system of the SMS-1 has it's advantages.  If your required sub location in-room makes for a response that looks like the rocky mountains you will usually benefit much more from using an SMS-1 to smooth the response than using nothing at all. 

On the other hand, if you can get Room EQ Wizard working you can get superior end results by using it and some of the other units mentioned above.
Mark Seaton
Seaton Sound, Inc.
sales@seatonsound.net
773-290-8436
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Stress
Thanks for the references to some eq. I guess, like the subs, there are subjective preferences as to which piece of hardware is preferred?

A couple more questions:

1. Does the lower than "High Def" (eg DTS Master Audio) sampling rate on some of the hardware affect the output to the sub? That is, if a dts master audio sound track was used, would the sub receive less than that recorded (make sense)?

This all assumes I could even tell the difference......

2. I was told by a manufacture (soon to produce a sub with DSP - eq built in) that all I would need to do to correctly setup the subs in room would be to let each one calibrate to the room independently. Is this an accurate (overly simplistic) description of how it could/should be generally done?

Thanks
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