ART Cleanbox mod thread

**brucek** · **09-13-07, 09:21 AM**

Quote:

Going back to the .22 caps in parallel

I would think the smaller tantalum would fit in there easier, but if you're having trouble, why not.

The tantalum should work just fine. Certainly it would have to be oriented towards the supply (feed the audio signal into the negative input). A cheap device like this would almost surely use a single supply, so the reference for the input of the op amps used would be a virtual ground between the +ve positive supply and real ground. This means the positive of the tantalum would be connected at the electronics side and the audio would feed the negative terminal. That's it really. I don't see any problems or reasons for extra ground reference connections.

brucek

**bobgpsr** · **09-13-07, 02:33 PM**

Quote:

brucek wrote:

I don't see any problems or reasons for extra ground reference connections.

You won't get the right voltage potential across the capacitor's electrolyte if the source is also AC coupled. Best to insure a DC path to ground for the negative end of the cap. Without a DC voltage potential, the dialectric insulating film produced by the electrolyte against the tantalum slug is not maintained (long term wise).

**IBorBox** · **02-05-08, 07:21 PM**

When checking the frequency response, was the clean box tested using the full in and out (looping thru the device) or just channel 1 or 2? Looking at the capacitor mod, it shows 2 capacitors being replaced. Does each capacitor handle both the left and right sides for each channel 1 or 2 or does each capacitor handle the right or left sides of each channel (in this case I would think you would need 4 capacitors in 4 locations to handle the full in and out (looping thru the clean box)). Just trying to figure out whether replacing the 2 capacitors fully corrects the frequency response (left/right and channels 1/2). I would like to have my BFD looped thru the box, using it as a fancy adapter with gain control to my amp (non-pro amp with RCA inputs only). Would looping double the effect of roll off? If I were looking to use only one channel of the clean box, it would be the XLR "in"/RCA "out" to allow gain control into my amp from the BFD.

Although not ideal, wouldn't EQing pretty much correct for the natural roll-off of the device? Since restoring what was originally there by EQing wouldn't load the amp any differently (then if the device was not in the signal path and attenuating the signal), I don't see this as a major problem. As long as you are aware that the roll off is inherent in the device and not the room response, you can feel comfortable in boosting the low end knowing the "problem" is in the input to the amp and not a room geometry effect. Don't know if my logic is simplistic but I appreciate your thoughts. Also, my thinking may go against popular opinion here and at one time found flat response down to 10Hz impressive (which technically it is) and desireable, I found pretty much anything below 18Hz (maybe 20Hz - sacrilege!) to be wasting my amp power - my point? - the device acts as a subsonic filter - unadvertised feature especially if you size the caps correctly! I did just order the clean box (because I can't adjust my sub out level low enough and found no suitable alternatives for a reasonable price) and will try to see if my sweeps can be corrected back to flat without the mod. I may have a whole new perspective when I get done! Thanks!

**bobgpsr** · **02-06-08, 09:47 AM**

If you only have one subwoofer, then normally you only use one channel of the Cleanbox. So you only need to modify one Cleanbox input. The input coupling cap is the only real freq rolloff issue area because of its original value into the moderate input impedance forming a voltage divider. The output coupling cap is not a limiting freq factor due to its much larger value.

If you really want a moderate high pass filter -- then yes leave the Cleanbox unmodified. But those of us who are wanting real output at 15 Hz (or even down to 10 Hz) will want to do the modification to the channel(s) of the Cleanbox being used.

**IBorBox** · **02-06-08, 10:58 AM**

Thanks Bob! So to fully use red and white on both channels 1 and 2 and get the benefits of flat frequency response I would only need to change the 2 capacitors (just trying to get it straight in my own mind about correcting the in and out since I want to loop thru the box to eliminate the need for any more adapters). Regarding the subsonic filtering, since I am using an amp that has a very mild subsonic filter, I was looking at this as a way of tailoring the extreme low end without resorting to another device in the signal path. Since I need to adjust my gain into my amp somehow (even with my sub at its minimum setting in my receiver, the sub is 6dB hot. Also my input to my BFD is barely registering on the LEDs, so I need to get that higher to avoid S/N issues) I need some sort of gain control. When I was running the sine wave sweeps I ran from 10-200 Hz and only started hearing the test tones at 20 Hz+, although the room plot indicated I was getting significant output below 20 Hz ( http://www.hometheatershack.com/foru...html#post74637 ). I did notice vibration below 20 Hz but didn't strike me as impressive.

**ccdoggy** · **02-06-08, 12:41 PM**

Some people like subsonics some people dont. its all personal preference.

I am a fan as it brings movies like War of the Worlds to life, but it is true it takes allot of power and output to make it worth while.

technically you only need to change one of them as the signal will only be passing through one side of the channel. but for sameness do both.

You say "loop through" the box. do you mean go from the rca input to the xlr output to the xlr input to the rca output and then to the sub? if so the frequency rolloff will be steeper then just one. not sure why you would do it (if you are that is)

So you are planning on using the ART to Lower the voltage, not raise the voltage? What amp are you using?

**IBorBox** · **02-06-08, 07:02 PM**

Ccdoggy yes, I have to lower the gain going to my amp. I have my subwoofer "out" on my receiver set to the minimum setting (-20). I'm getting a low signal into my BFD (at most 2/3 LEDs lighting up for input levels while watching at a normally loud "movie" volume). Even with this, my IB sub is 6dB hot (measured roughly flat +/- 3dB from 15 Hz - equalized thru the BFD). I need to control the gain into the amp from the BFD. By looping I mean as you have described it. I need at a minimum the XLR "in"/RCA "out" channel to feed the amp a reduced signal. The looping part is purely for convenience. I currently use the 1/4" to RCA Parts Express cheepy adapters to go from my receiver (Sony DA-4ES) to the BFD and from the BFD into my NAD 2200 (I have had it since 1986 and works great, but has no gain control) bridged into mono driving 4 Tempest-Xs wired for a total of 4 ohms in a manifold Infinite Baffle. In a nutshell, I need to boost the level going into the BFD to get more LEDs lit up to minimize S/N and I need to lower the gain out of the BFD so my sub volume can be matched to my mains. If I can eliminate the adapters by looping thru the clean box, that would be great but not absolutely necessary. Do the 2 capacitors take care of both channels? or just the left and right sides of the RCA "in"/XLR "out"? Do I have to worry about doing anything if I only use the XLR "in"/RCA "out" side as mentioned above and as follows "The input coupling cap is the only real freq rolloff issue area because of its original value into the moderate input impedance forming a voltage divider. The output coupling cap is not a limiting freq factor due to its much larger value." I need to have the cleanbox act like the gain knob on a normal sub plate amp. In my scenario, my gain knob has to turn counterclocwise where most others turn their's clockwise

**ccdoggy** · **02-07-08, 12:12 PM**

I see now, it makes a bit more sense now that its explained.

as far as replacing the other side of caps I think you need to but dont quote me on it. im not so great with stuff like that. I am sure someone here can help and say yes or no to them.

**oraclation** · **02-26-08, 10:06 AM**

I did the mod on only one channel (c7). I tested each channel separately and the right channel seems to have more output, but I'm not convinced it is the modded channel. I would have expected c7 to be the left channel as it is on the left side of c8. Apparently this is not the case.

Can anyone confirm that c7 is actually the right channel even though it is on the left side of c8?

Since I have an IB with six 15" TCSounds subs, I already have far more output between 12-25Hz than I do above 25Hz and the high pass actually helped flatten the response. But since it's mostly tactile below 20Hz, I've found that I don't mind an upward curve on the low end, and this is my reasoning for doing the mod. And I may pick up some sub 10Hz waves. I still have plently of headroom above 100dB, so should be okay.

Thanks

**oraclation** · **02-26-08, 09:00 PM**

Quote:

oraclation wrote:

I did the mod on only one channel (c7). I tested each channel separately and the right channel seems to have more output, but I'm not convinced it is the modded channel. I would have expected c7 to be the left channel as it is on the left side of c8. Apparently this is not the case.

Can anyone confirm that c7 is actually the right channel even though it is on the left side of c8?

Since I have an IB with six 15" TCSounds subs, I already have far more output between 12-25Hz than I do above 25Hz and the high pass actually helped flatten the response. But since it's mostly tactile below 20Hz, I've found that I don't mind an upward curve on the low end, and this is my reasoning for doing the mod. And I may pick up some sub 10Hz waves. I still have plently of headroom above 100dB, so should be okay.

Thanks

After testing w/ REW, I answered my own question: c7 = right channel

I only modded one channel and after testing the frequency response, I decided to use the non-modded channel. Why? Well, if you saw my FR graph, you would probably do the same (i.e. I already have 25dB higher levels at 12Hz (120dB) than at 80Hz (95dB)). The modded channel is even less flat in my situation.

It was a fun experience though!

**ccdoggy** · **02-27-08, 08:18 PM**

whoa, thats a lot of room gain.

**Mike Cason** · **03-09-08, 03:37 PM**

thylantyr, (or others)

I've seen many of your posts over the years.

I've just completed my second SoundSplinter dual RLP-15/4 passive radiator subwoofer and my tuning frequency comes out to 23 hz but I'm enjoying extremely rich bass, especially corner loaded and I have a substantial room gain.

I've just found and gone through this thread about the Arts Clean Box and just happen to have one coming in from Parts Express tomorrow. I'm surprised to just find out that this box may be killing the low end. Is it really hurting the low end? I'm running a top of the line Rotel receiver/amp and am powering each subwoofer with a QSC 1450 bridged to mono. I've soldered terminals to the RCA outs from the Rotel and am hooked up to the terminal strips on the amps. The subs are wired to present an 8 ohm load to the amp and they sound so good right now and I thought the Arts Clean Box would be a benefit.

Should I change out the two (green) caps noted in the forum? I'm seeing mixed results from the different posters. I have my Rotel crossed at 60 hz to the subwoofer.

What is your suggestion so I don't loose any more low end. My tuning is high so I can't afford to lose the low end. I've built my own crossovers for my mains and center speaker, so to modify the Arts box should be easy for me. Which caps would suit my needs the best, or do I use the Clean Box as a paperweight? I'll be using both channels as I'm running dual amps.

Thanks,
Mike

**bobgpsr** · **03-10-08, 12:27 PM**

Simple mylar or polystyrene caps are best. Do not use electroytic or tantalum.

With a tuning freq of 23 Hz perhaps you need a bit of a high pass filter anyway to prevent your drivers from unloading (exceeding Xmax or worse yet Xmech) below the tuning point. Have you modeled your build using something like Unibox?

**Mike Cason** · **03-10-08, 02:48 PM**

Bob,

It's been modeled on WinIsd at 23.5. I've seen the post to replace the caps on C7 & C8 with a
1uf cap from rat shack and picked a couple of them up today. They are rated at 250wDC and

I've also picked up a .47uf 650v and two .22uf 650v(I'll have to double them). from Frys (low inventory). I'll need to modify both channels as I'm running two QSC 1450 amps. They have subsonic filters and I've activated them. My main unit is the Rotel 1065 receiver/amp with good crossover capabilities.

Which caps do I use?

Thylantyr has recommended the 1uf radio shack caps to another poster, and I have two of them sitting here just waiting to be put in. I just want to do it right the first time.

Thanks,
Mike

**Mike Cason** · **03-10-08, 03:43 PM**

Bob,

I'm going to install the 1uf Radio Shack caps. After re-reading two threads, I think I'll be happier with them. I like my bass low at low volumes, so I don't want to loose the low end that I think the Arts box would take away.

Thanks,
Mike

**Mike Cason** · **03-10-08, 06:59 PM**

I installed the 1uf caps in C7 & C8 and rushed into the house to put Arts box in the system.

I'm sure glad I had both of the amps and the gain on the Clean Box turned down. When I started to increase the gains on the amps, the subs were quiet. I had them at about 1/4 way turned up.

Next I approached the Arts box and started turning up the gain. I had Eric Clapton's Crossroads with Joe Walsh's performance on disc two playing, and it almost blew the drivers clear out of the cabinets with only 1/3 of the gain on the Arts box turned up. It was muddy, loud, and distorted.

It was like putting in two jet engines in a volkswagon. All I can say is WoW!

I took out the Arts box and rewired my amps back to where I had them. The QSC has a barrier strip for matching up home audio impedance outputs to the pro input.

My Rotel must have a great sub pre-out signal because the Arts box was way too much and the QSC's are now producing the nice clean deep bass they were before.

Gunna have to find a home for this new gadget....

**bobgpsr** · **03-11-08, 12:06 PM**

Yeh, I had the gains all the way up (max clockwise) on my Mackie M1400 pro amp -- and could not get enough drive out of an old Panasonic HE70 AVR's sub line output. That is enough drive to calibrate the sub level to the right SPL as compared to the other channels using a SPL meter with an Avia or THX optimizer DVD. So for me the ART Cleanbox consumer level to pro level conversion gain was required. Depends on your AVR if your pro amp does not have a consumer line level (-10 dBV) input option.

**Mike Cason** · **03-11-08, 02:09 PM**

Quote:

thylantyr wrote:

What events lead you to believe that you needed more boost to
the signal? If you never had QSC gains up, no reason for a booster.

First off it was free because Parts Express sent me a couple of broken passive radiators I fixed here at the shop to save the shipping, and second, I thought it might just give me a little more low end at low volumes.

When the wife is gone, I do crank up the gains now that I have an 8 ohm load to the QSCs and I like my music DVDs to sound like I'm there at the concert, kinda sorta wide open.....as the drivers are rated at 1000 watts, and driving them at the low freqs I'm only hitting them with about 800 watts. It varies with the quality of DVDs I watch and how they are recorded. I wanted to stay out of that clipping range with the gains too. I've got the clip limiters turned on with the QSC's.

Before I built the second subwoofer, I had one QSC per driver. Bridged at 4 ohms, that's too much power for them.

That's what this DIY is.....playing with older kids toys....

**happyhourhemi** · **04-14-08, 06:07 AM**

Quote:

bobgpsr wrote:

Yeh, I had the gains all the way up (max clockwise) on my Mackie M1400 pro amp -- and could not get enough drive out of an old Panasonic HE70 AVR's sub line output. That is enough drive to calibrate the sub level to the right SPL as compared to the other channels using a SPL meter with an Avia or THX optimizer DVD. So for me the ART Cleanbox consumer level to pro level conversion gain was required. Depends on your AVR.

Glad I just read your post bob! I have an he70 and was wondering if I was going to have to deal with this, looks like I am. I will be going into a ep2500. Haven't started my build yet but just trying to get all my ducks in a row, so when I hook it all up I won't be disapointed. Now I just need to find someone to design some boxes for me for 2 ED 13Ov.2's.

Great forum! Thanks to all the guys out there for testing this.

**Mike Cason** · **04-14-08, 06:59 AM**

Quote:

happyhourhemi wrote:

Glad I just read your post bob! I have an he70 and was wondering if I was going to have to deal with this, looks like I am. I will be going into a ep2500. Haven't started my build yet but just trying to get all my ducks in a row, so when I hook it all up I won't be disapointed. Now I just need to find someone to design some boxes for me for 2 ED 13Ov.2's.

Great forum! Thanks to all the guys that put there nuts out there to test this.

If you have already purchased the Arts Clean Box, start the gains at -0- and then work them up gradually. I installed one and found the box to be very sloppy with my system and after a couple of minutes, I yanked it out to keep from blowing my drivers. I have a high end receiver, so maybe the Arts Box was designed for a lower end receiver with less sub output. I even made the modification to the Arts Box to improve the bass by changing out a couple of capacitors.

I immediately purchased the Reckhorn B-1 sub eq with subsonic frequency protection and have integrated my system beautifully with my subs and QSC pro amps. This is a finely crafted and machined German made product, and IMHO, it severly outperforms the Arts Box for just a couple of bucks more.

It is available through CSS out of Canada. They ship from Washington state in about 5 business days. http://www.creativesound.ca/

Bass control has never been better for me. The musical quality is unbelievable!

Mike

**bobgpsr** · **04-14-08, 07:47 AM**

Quote:

happyhourhemi wrote:

Glad I just read your post bob! I have an he70 and was wondering if I was going to have to deal with this, looks like I am. I will be going into a ep2500.

If I recall correctly the Behringer EP2500 may have a consumer level (-10 dBV) input option. You may want to be sure to set up and try out that input before you get a Cleanbox. You might not need it with your amp.

**tundraSQ** · **04-16-08, 05:44 PM**

I'm just curious as to if anyone has done this mod on the Rolls Promatch MB15? I bought one hoping to avoid the Cleanbox mod, but from what I have read they are "twins". The two caps needing replacement say "47n J100" on them.I plan on modding only one channel, if anyone knows whihc is left and which is right. I have c16 and c15...with c15 in the front.

I can snap a pic if anyone is interested.http://www.hometheatershack.com/foru...ilies/nerd.gif

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