Silent EQ Device

[TNTTNT]

I am hoping your expereinces or thinking may help in finding a solution to a problem.

I have a stereo pre-amp feeding a Behringer DEQ2496. I use RCA to XLR cable.

The DEQ2496 feeds the power amp in an active sub (BK Monolith), using 10m XLR to RCA cable.

When I turn the DEQ off I get a decent signal out of the sub. When I turn it on, the signal is virtually silent.

What is more wierd is I can selectively turn off each EQ function. When switch them all off individually - no sound. When I hit the [bypass all] button, I get my sound back.

I can't figure out what would cause this, but it must be something in the DEQ.

Any ideas guys?

[brucek]

but it must be something in the DEQ.

Yep, just go through and disable everything and find out what filtering is on that is killing the sub...

brucek

[TNTTNT]

Bruce, it is not often when I can supply both question and answer.

I bought some made to order XLR/RCA cables from a guy on a UK forum. He sounded quite authoratitive.

I opened the connections and one XLR end pin 3 in not connected to anything. I don't mean not bridged, I mean not connection.

On the other XLR/RCA cable, pins 1 and 2 are bridged, not 1 and 3.

I am really shocked.

[TNTTNT]

It is 2am in here in the UK and I think I have finally nailed all the problems I have met on the road to here.

I bought some unbalanced RCA/XLR from a guy on a forum who had a good reputation for making XLR cables. I bought one std XLR cable, and this was really neatly made.

I think anything off script and he is clueless. I ordered 4 unbalance RCA/XLR cable. He didn't connect any wires to pin 3 on some cables. On the others he bridged pins 2 to 3 (It should be 1 to 3).

I haven't soldered for about 25 years, so I had to fix. It works now, although the solder joints I did look like a plaster cast on a broken arm. It wasn't easy because the guy used one conductor Van Damme instrument cable, so I had to do a tiny bridge on the pins.

Apart from a +7db 42.5hz node, I have EQ'd the room to +- 2db (20hz to 90hz). It looks really flat, and I have really got to grips with parametric EQ - Great thing. I'll submit a plot when I have played with more.

I bought a Behringer ECM8000, and the DEQ2496 is magnificent SPL meter with this mic.

Quick question. Given my soldering it really clumsy and I use loads of it, will this affect sound quality noticeably? Also, I didn't have any decent wire for the bridge, so I used some wire from an electrical cable. Is this ok? It is only 1/2 inch long, and to be honest there is more solder then wire.

[Wayne A. Pflughaupt]

No, less-than-beautiful soldering won't affect SQ, as long as you don't have a cold joint. There's a link to a DIY guide to soldering cables in my signature that you might want to check out.

BTW, Depending on the cable you're using, you don't have to jump between pins 1 and 3. If you're using two-conductor mic cable, see #17 below.

Regards,
Wayne

[TNTTNT]

Great, I'll check out the link. The cable was single conductor cable, which left me amazed how this guy who made them could leave pin3 with no wire attached.

Does anyone know how to apply shelf filters in a DEQ2496? It is the only feature I haven't figured out yet. I can see any way to set them.

[Wayne A. Pflughaupt]

Great, I'll check out the link.

Sorry, forgot to drop in the image - here it is (see #17).

As for the shelving filter, I don't think the DEQ has a specifically designated one. However, you can more-or-less create one by using a broad filter centered above the subwoofer frequencies, like this (picture courtesy of brucek):

Regards,
Wayne

[cixelsid]

Page #3 of the owner's manual tells how to set the built-in 6dB & 12dB shelving filters.

[TNTTNT]

Thanks guys,

Oh boy this DEQ is awesome. I have to confess I did not fully grasp what was meant by these filters. I realise now they are like high and low pass, with more options. I have used this to sharpen the cut off from my sub. I can't run SPL tests because the kids are playing in the room.

I have found that as I get near the 100hz cut off, turning the sub off increases SPL. I am sure this is phase related, but am leaving phase at zero, because changing this affects all the regions below 100hz adversely. I'll use these shelf filters to effectively turn off the sub at 100hz.

I am gutting large parts of the range by -15db, which shouldn't be a problem. I am boosting some parts by 15db, and remember people saying this isn't good. Will this cause problems?

[DragonArt]

+15 db's is a huge amount of gain. Monolith can't handle that much gain even at medium volumes. If you exceed the subs limits, you may and eventually will:
1. Clip the amp, possibly causing thermal damage if run at high level(this will happen at both high and low frequencies)
2. Bottom the driver, possibly misaligning the voice coil, causing mechanical damage(mostly below tuning frequency (sub-20's), because the Monolith has no HP-filter)

A better way to get rid of nulls is to move the sub around a bit. I once experimented with my sub and found out that even even a few inches can make a huge difference. Where is your sub located now? Corner-placement will in most cases make nulls and peaks worse. Also by cutting down the subs level to match the nulls you are effectively boosting the null frequency. So, in short: EQ is for cutting down peaks in your FR, if you have nulls, move the sub around.

Oh, and sorry for the rant

[Wayne A. Pflughaupt]

Depends on whether or not you have the headroom. Any equalization (both boosts and cuts) exacts a headroom penalty from the amplifier and drivers; naturally, the more drastic the equalization, the more the penalty.

The bigger issue in your situation, if you have a 30 dB swing between your peaks and depressions, I characterize that as "unequalizable" response. A 15 dB swing would be much more managable, and even that's pushing it. If your situation allows, experiment with different positions to get a better starting baseline.

For your edification, shelving filters are different than high and low pass. Here are a couple of pictures that show the difference.

Shelving Filters



Linkwitz/Riley High/Low Pass Filters

Regards,
Wayne

[TNTTNT]

Again, many thanks for these tips. I'll use the the EQ to cut problems, but try to move the sub for drop outs.

I have come a fair way thanks to the wisdom and kindness of this community. Since wondering whether I should get a sub I have got into: -

Room measurements
Room node calculations
EQ
Making (Ok correcting) my own cables.

I still have a lot to learn. Last night I though I had EQ'd my room to quite a flat line. I went back today and raised the ave line to 75db and this was enough to excite every mode under 60hz. Without the sub I get +10db at 43hz. I'll try to move the sub, and may even think about treatment. Sub 100hz the thickness of panels needed may be impractical.

It doesn't have the convenience of REW, but the RTA and SPL meters on the DEQ2496 is almost addictive. It is really easy to use. I get a digital readout of SPL to 1 decimal place. I don't have experience of other, but I can't recommend the DEQ2496 enough.

for the last few months I sometimes comment on a hi-fi forum in the UK. I have been giving a commentary on my learning curve with EQ. They don't seem very impressed. I am guessing that for some reason they think that equalisation is too 1980s. It's wierd to me because instead of worrying about an interconnect made of copper, silver and Yak's hair; I would be more worried if my room was adding +10db to my listening.

[DragonArt]

You should always make your measurements at high enough levels for the mic to pick up the signal properly. That usually means about 80 to 95 db's for me. Be careful though, the Monolith has no HP filter so you can bottom it out very easily at subsonic frequencies.