ART Cleanbox frequency response

Since the ART Cleanbox is often recommended to those having low signal level problems with their pro amps, I thought to try it out. For my disappointment, it turned out to be less than adequate for my needs.

Here's its frequency response (measuring system is flat).

As you can see, its FR starts to roll off already at ~200 Hz. Here are some numbers:

Frequency / "Down" at that frequency
100 Hz / -0.4 dB
50 Hz / -1.5 dB
20 Hz / -5.4 dB
10 Hz / -10.3 dB
5 Hz / -15.9 dB
2 Hz / -22.6 dB

So unless your system definitely needs some extra protection down low, or you have too much "room gain", I wouldn't recommend using it. It's like adding an extra ~1st order high pass filter at ~30 Hz.

I also found out that it adds some noise (low S/N ratio) into the system.

My ART Cleanbox is for sale. Anyone?

This doesn't sound good at all for Mr. ART...

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Sonnie



Cedar Creek Cinema

The Behemoth

Another one bites the dust and another valuable piece of real world info from Ilkka. Now imagine if someone was using a Velo SMS with an Art Cleanbox in the chain coming from a HK receiver......wow, instant HTIB subwoofer

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My System
LLT Explained

What's the fix, I have been debating on the ep 2500 or the carvin hd1800. I have read there were no problems with the preout voltage on the Carvin but have heard of problems on the ep 2500. If the real world watts on the ep2500 is about 2000 what is the real world watts of the carvin?

The input sensitivity of the EP2500 is +4dBu. That's a standard output level of retail equipment. I can't imagine that there would be a level problem...

brucek

Wow!

I have no problems and no one else does that I know of with the EP2500, but I suppose the receiver could make a difference.

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Sonnie



Cedar Creek Cinema

The Behemoth

I am running my Naim stereo preamp straight into my sub's EP2500.

I don't even have the Behringer's control knobs set at full on. Currently 28 out of 34 full scale.

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My IB on frappr

My IB Subwoofer blog

I knew I had some major loss somewhere below 15Hz, but I never checked there. It never even crossed my mind. I just gave up. I feel the tweaking urge again. I don't know if I should thank you, or punch you.

Now I know why I can run my RS Sonos at 0dB all day, without killing them. Everything below my tuning is "well" dampened.

I suspect there are quite a few people using this piece of equipment that have no idea what it is doing to their signal.

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Sonnie



Cedar Creek Cinema

The Behemoth

I didn't know that. Thanks!

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Jim
Houston, TX
My Subwoofer Build Page

Yeah, that's not too good a response.

The line driver I use is a Paradigm X-30. It offers about +13dB variable voltage gain along with two subwoofer outputs, one with full phase control. It also allows mono or stereo input and mixes the signals together. It even has three high pass outputs if you need them.

It's only fault I find is that there isn't a bypass switch to defeat the crossover when it's not required, although you can dial it fully clockwise and it takes it past the bass management that most people would use.

I use this device when my processor is in bypass, because the subwoofer signal is a full range analog mix of the left and right channel and requires bass management. When I'm in HT mode I dial the crossover fully clockwise.

Here's a response curve (since we're posting them). The crossover was set at full.

x-30 response.jpg

brucek

I’ll add one more thanks, Ilkka. I’ve seen this recommended several times – it never crossed my mind that it might affect the frequency response of the sub.

Perhaps a dumb question, but if you already have some type of PEQ in the chain, could you just apply a reverse filter to correct the signal loss from the Cleanbox?

Gain filters reduce dynamic range and S/N ratio. In addition the lowest filter the BFD can use is 20Hz....

brucek

This means I should really eliminate my CX2310 active crossover for unwanted (unknown) bass roll-off.

Would somebody please share the simplest method of measuring an active crossover using REW?

It would also be fun to see the variable frequency curves graphed if possible.

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My IB on frappr

My IB Subwoofer blog

Ensure soundcard.cal file is loaded.

Ensure C-weight unchecked.

Ensure meter calibration file cleared.

Loop cable from line-out to line-in and ensure flat response is achieved.

Include the device under test in the looped cable and set up REW levels and measure....

The graph will be the response of the device....

Also see this thread on measuring the response of processors. Substitute your crossover for the processor.. You can measure any line level device as long as you can control its gain to 1:1 (unity)..

brucek

It's really easy. Make sure your measuring system is calibrated flat i.e. perform a sound card calibration. Unload mic cal file and uncheck C-weighting. Then put the device to be measured in the path between the line output and input. Take a sweep and there's your FR. Move the line so that the "flat" part reads 0.0 dB. That way it's more easier to read it.

And yes, every piece of device adds its own FR, whether it's flat or not, into the chain.

That's interesting. Maybe I will test it some day.

Interesting, and disturbing. I'm not one of those who cares deeply about performance below 20 or maybe 16 Hz (don't listen to that much organ music) but these measurements make a compelling case for not using one of these things if you don't have to. (In my current HT, I do 'have to' right now, but perhaps not in the future...)

As an aside, nobody ever would have to chain one of these with an SMS-1. It provides the same function, as it can accept either type of input and output either RCA or XLR regardless of input type.