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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: Alan Gibson on October 11, 2019, 11:25:46 am

Title: Low volume on QSC KW 153?
Post by: Alan Gibson on October 11, 2019, 11:25:46 am
I just bought my first pieces of sound gear, a QSC KW set of 2x 153s and 1x 181, all gently used. Two out of three pieces sound great, but one of the 153s showed up missing a foot(!), and with the gain B turned all the way up to +10dB. I connected this speaker to line in B through XLR cable to the 181, and did the same for the other on the A side. Speaker B sounds ok when left at +10dB, but is noticably quieter than speaker A when both are turned to +0.

What could be causing this? I'm not expert, but is there something I can do, or will I have to take this monster in for repairs?
Title: Re: Low volume on QSC KW 153?
Post by: Taylor Hall on October 11, 2019, 11:43:10 am
You'll need to update your profile name to be your real name before we can help you.
Title: Re: Low volume on QSC KW 153?
Post by: Alan Gibson on October 11, 2019, 12:11:40 pm
You'll need to update your profile name to be your real name before we can help you.

There we go, sorry about that.

A little additional info, I was missing an XLR so I grabbed one from my roommate's microphone, and that's the cable I used for B speaker. Seems unlikely, but could that be the culprit?
Title: Re: Low volume on QSC KW 153?
Post by: David Winners on October 11, 2019, 12:20:52 pm
Switch the cables and see if the problem goes with the switch
Title: Re: Low volume on QSC KW 153?
Post by: Chris Hindle on October 11, 2019, 12:26:43 pm
There we go, sorry about that.

A little additional info, I was missing an XLR so I grabbed one from my roommate's microphone, and that's the cable I used for B speaker. Seems unlikely, but could that be the culprit?
Probably pin 2 or 3 is disconnected or shorted to pin 1 in the XLR, at one end or the other.
Swap cables and see if the problem follows the cable.
Chris.
Title: Re: Low volume on QSC KW 153?
Post by: Taylor Hall on October 11, 2019, 12:28:43 pm
It could be a bad cable, you could swap it with the one you used on the other speaker and see if that changes anything.

Barring that, I'd start by removing the sub from the signal chain and see if that makes a difference. You mention using input B on the bad 153, is it also quieter when you have it in input A? Be careful when doing this as input A can accept either line level or mic inputs and has an attenuator knob that must be turned down. 

I'd also try swapping sub outputs going to the questionable KW153 (try using output A instead of B) just to be sure there's nothing amiss there.
Title: Re: Low volume on QSC KW 153?
Post by: Alan Gibson on October 11, 2019, 12:29:09 pm
Swapped cables, and the problem persists on the same speaker. It sounds like the bass response is greater than the mid/high testing speakers B on its own then listening to A.

Also tried Taylor's suggestion about swapping inputs to the sub. Problem stays with the speaker. My xlrs aren't long enough to remove the sub from the chain, but I'm now sadly confident that something is up with the mid/high of speaker B.
Title: Re: Low volume on QSC KW 153?
Post by: Scott Holtzman on October 11, 2019, 01:10:17 pm
Swapped cables, and the problem persists on the same speaker. It sounds like the bass response is greater than the mid/high testing speakers B on its own then listening to A.

Also tried Taylor's suggestion about swapping inputs to the sub. Problem stays with the speaker. My xlrs aren't long enough to remove the sub from the chain, but I'm now sadly confident that something is up with the mid/high of speaker B.

I think you will also find one KW181 insufficient.  The recommendation for 153's is 4. We stack them on two a side and it's a great system.

Title: Re: Low volume on QSC KW 153?
Post by: Alan Gibson on October 11, 2019, 03:09:16 pm
I think you will also find one KW181 insufficient.  The recommendation for 153's is 4. We stack them on two a side and it's a great system.

You mean 4 subs per top?
Title: Re: Low volume on QSC KW 153?
Post by: Tim McCulloch on October 11, 2019, 03:33:41 pm
Swapped cables, and the problem persists on the same speaker. It sounds like the bass response is greater than the mid/high testing speakers B on its own then listening to A.

Also tried Taylor's suggestion about swapping inputs to the sub. Problem stays with the speaker. My xlrs aren't long enough to remove the sub from the chain, but I'm now sadly confident that something is up with the mid/high of speaker B.

It's only a mic cable, borrow one from a microphone for testing or put the top box on the floor.  This ain't rocket surgery.

A significant difference in signal level, accompanied by a lack of lows, typically indicates a "one-legged" signal as @Chris Hindle mentions.  Most often it's a user-supplied XLR cable that is faulty but it could be cracked or bad solder on the amplifier's input jack.

Take the sub(s) out of the loop.  Set the controls of both A and B speakers identically - every button push, every rotary control - make them the same.  Power them up and connect the output of your mixer to speaker A, then B.  USE THE SAME INPUT on each speaker.  If they don't sound the same you need to take the sketchy speaker for service.
Title: Re: Low volume on QSC KW 153?
Post by: Don T. Williams on October 11, 2019, 03:39:55 pm
I agree with Scott that 2 KW181's per Kw153 is the right ratio for most events.  At one time I had 3 Kw153's per side and 12 KW181's.  As expected, the KW153's didn't couple perfectly, but I only used that many when I needed 180+ degree coverage, and two per side carefully splayed weren't too bad.  I still have some KW181's from that era in my rental stock that I use as drum subs.  The QSC stuff really holds up well and sounds decent.  One caution with KW181's - be careful when "flipping" them from their casters onto the floor.  My only problem ever came from customers (or stage hands) breaking the 18"s magnet loose doing just that.
Title: Re: Low volume on QSC KW 153?
Post by: Scott Holtzman on October 14, 2019, 09:29:19 pm
I agree with Scott that 2 KW181's per Kw153 is the right ratio for most events.  At one time I had 3 Kw153's per side and 12 KW181's.  As expected, the KW153's didn't couple perfectly, but I only used that many when I needed 180+ degree coverage, and two per side carefully splayed weren't too bad.  I still have some KW181's from that era in my rental stock that I use as drum subs.  The QSC stuff really holds up well and sounds decent.  One caution with KW181's - be careful when "flipping" them from their casters onto the floor.  My only problem ever came from customers (or stage hands) breaking the 18"s magnet loose doing just that.

I can also tell you the magnet breaks lose when you let one roll of the back of the truck too!  With the cover on there was no external cosmetic damage!

I can also tell you to set the brakes on your road cases carefully.  Had a load staged in front of the bay door in the parking lot.  It has a good pitch.  Went inside and a trunk had gotten free, rolled into a ladies car in the parking lot as she was backing out.  I came out of the office and this lady is hanging out her window trying to push the trunk off her car.  She was not amused. 
Title: Re: Low volume on QSC KW 153?
Post by: Mark Norgren on October 15, 2019, 07:35:39 am
One more thought, are you daisy chaining the speakers or using a L-R inputs? 
Title: Re: Low volume on QSC KW 153?
Post by: Alan Gibson on October 15, 2019, 12:51:30 pm
One more thought, are you daisy chaining the speakers or using a L-R inputs?

Daisy chained through the subwoofer. I'm Actually wondering how I can chain up all the speakers to the subs if I go ahead and add 3 extra subs to the setup..

At any rate, I've taken the speaker to the shop. It kicks back on and off, so it's obviously something fiddly with it's insides. Thanks everyone for your input!
Title: Re: Low volume on QSC KW 153?
Post by: Mal Brown on October 15, 2019, 01:45:39 pm
I run 1 181 under 1 153 but throttle the 153 back a bit on lower volume gigs.  1 153 over 2 181's per side is a nice healthy rig.
Title: Re: Low volume on QSC KW 153?
Post by: Rich Grisier on October 16, 2019, 11:54:52 am
I agree with Scott that 2 KW181's per Kw153 is the right ratio for most events.  At one time I had 3 Kw153's per side and 12 KW181's.  As expected, the KW153's didn't couple perfectly, but I only used that many when I needed 180+ degree coverage, and two per side carefully splayed weren't too bad.  I still have some KW181's from that era in my rental stock that I use as drum subs.  The QSC stuff really holds up well and sounds decent.  One caution with KW181's - be careful when "flipping" them from their casters onto the floor.  My only problem ever came from customers (or stage hands) breaking the 18"s magnet loose doing just that.

Hmmm... very interesting! I have 2 KW153's and 4 KW181's. I've had a couple magnets break free. I replaced them with Celestion FTR18-4080FD and haven't had any problems with those. It seems the adhesive used on original speakers eventually got brittle and let loose. I was wondering why this was happening. What do you do with the speakers once the magnets break free? Do you rebuild them?
Title: Re: Low volume on QSC KW 153?
Post by: Chris Grimshaw on October 17, 2019, 10:25:16 am
I suspect that the KW181 magnet problem can be fixed. Here's my quick-and-easy way to do it:

- M6 threaded rod, 1" shorter than the gap between magnet and cabinet wall
- 2x T-nuts hammered into...
- 2x Wood discs, drilled centre for the T-nuts. I'd use 18mm ply.
- 2x M6 nuts

Make a miniature dumbbell: disc, T-nut, M6 nut, M6 nut, T-nut, disc.

You'll have it so that rotating the wooden disc separates or contracts them. Set the gap so it'll fit between the magnet and the cabinet, and rotate one of them until the assembly is firmly wedged in place.
Grab a spanner, tighten up the M6 nuts so the wooden discs can't rotate any more.

Job done.

Bonus points for gluing one side to the cabinet, and a bit of foam between wood and magnet.

Chris
Title: Re: Low volume on QSC KW 153?
Post by: David Morison on October 17, 2019, 11:55:36 am
I suspect that the KW181 magnet problem can be fixed. Here's my quick-and-easy way to do it:

- M6 threaded rod, 1" shorter than the gap between magnet and cabinet wall
- 2x T-nuts hammered into...
- 2x Wood discs, drilled centre for the T-nuts. I'd use 18mm ply.
- 2x M6 nuts

Make a miniature dumbbell: disc, T-nut, M6 nut, M6 nut, T-nut, disc.

You'll have it so that rotating the wooden disc separates or contracts them. Set the gap so it'll fit between the magnet and the cabinet, and rotate one of them until the assembly is firmly wedged in place.
Grab a spanner, tighten up the M6 nuts so the wooden discs can't rotate any more.

Job done.

Bonus points for gluing one side to the cabinet, and a bit of foam between wood and magnet.

Chris

Remember to drill/rout out the front wooden disc to preserve any voice coil venting on the back of the driver..... this may affect t-nut placement.
Title: Re: Low volume on QSC KW 153?
Post by: Scott Holtzman on October 17, 2019, 01:08:27 pm
Remember to drill/rout out the front wooden disc to preserve any voice coil venting on the back of the driver..... this may affect t-nut placement.

I had always thought about a strip of plywood width of magnet with high density foam.  Never did anything about it as we have only had two magnet disasters in as many years as I have been on the forums (I think 7)

Title: Re: Low volume on QSC KW 153?
Post by: Don T. Williams on October 17, 2019, 07:58:37 pm
Speakers can be reconed, but when the magnet shifts or breaks loose, they have to degauss the speaker to get thing apart, and then re-energize the magnet.  Very few reconer's can do this, and with modern adhesives taking things apart gets really difficult.  I just buy new drivers.