Bridged mono for sub amp? - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 20 Old 02-19-2006, 10:26 AM - Thread Starter
Senior Member
 
Star Hawk's Avatar
 
Join Date: Feb 2006
Posts: 207
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
I built a box for my 12 in. Dayton 1200 Titanic subwoofer. It is powered by my old but capable Adcom GFA 545II. It does a great job but the subwoofer can handle a lot more power than this amp can deliver. The 12 in. Titanic has a nominal impedance of 4 ohms. The Adcom can pump out about 200 watts into 4 ohms, but the sub can handle 500 watts. I learned one way of getting more power from an amp is to bridge the output by connecting both channels to output as one channel mono or bridged mono as it is called. My manual says nothing about how to do this.
How does one setup an amp for bridge mono? A link to a diagram showing how the
two channels should connected would be a great help too. Thanks for any advice, suggestions, and tips.
Star Hawk is offline  
Sponsored Links
Advertisement
 
post #2 of 20 Old 02-20-2006, 08:23 PM
AVS Special Member
 
Wayne A. Pflughaupt's Avatar
 
Join Date: Mar 2001
Location: Katy, TX USA
Posts: 2,000
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 12
Bridging is pretty simple, from what I understand. All you have to do is drive the inputs with opposite-polarity signals. In other words, one channel has the (-) signal going to the RCA’s tip, and the (+) to the sleeve. Then you connect the speaker to the two positive posts.

Basically, if an amp is designed to be bridged, it will be set up to accomplish the signal inversion with a switch, and directions in the manual or on the chassis for speaker connections. If not, proceed at your own risk and don't come looking for me if it goes up in smoke. You’ll have to make your own cable to accomplish the signal reversal for the second channel.

Frankly, I’m surprised the 545 isn’t set up for bridging. My 555 is.

Regards,
Wayne A. Pflughaupt
Wayne A. Pflughaupt is offline  
post #3 of 20 Old 02-20-2006, 08:28 PM
AVS Special Member
 
whoaru99's Avatar
 
Join Date: Dec 2004
Posts: 6,960
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 67
Another thing you may run into if the amp is bridgeable is trouble with the 4 ohm speaker.

Not many consumer grade amps like to run bridged mono into 4 ohm loads since this is like running the amp stereo with 2 ohm speakers.

Just because there is a knob doesn't mean you should turn it.
whoaru99 is offline  
post #4 of 20 Old 02-21-2006, 02:18 PM - Thread Starter
Senior Member
 
Star Hawk's Avatar
 
Join Date: Feb 2006
Posts: 207
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
Thanks Wayne and whoaru99 for your replies. I decided not to hook it up bridged mono. I agree with Wayne that it could be risky since the amp does not have a bridged mono switch on it (probably for a reason). That reason might have been hit upon by whoaru99 in his reply that this amp is probably not designed for this task sinceit would be like driving a 2 ohm stereo load with the 4 ohm speaker connected to bridge mono. Until I can find a good high end subwoofer power amp, I will continue running my Adcom from one channel. 200 watts rms into 4 ohms will be ok for most movies, except perhaps War of the Wars with it's very demanding LFE. If anyone has a suggestion for one, please let me know. It must be a separate amp not designed to be mounted on the subwoofer. Those I have seen have smallish transformers and power supply filter caps ranging 10K to 15K uF, yuck. If money were no option I would go for the Gallo sub amp but it is expensive. Pro power amps
are another option but I don't want to mess around with balanced line inputs coming from
my unbalanced subwoofer line out (I have the Pioneer VSX-1015TX). Anyway, thanks again for your help and I am open to other options in sub amps.

Star Hawk
Star Hawk is offline  
post #5 of 20 Old 02-22-2006, 10:48 AM
AVS Special Member
 
kgveteran's Avatar
 
Join Date: Apr 2004
Location: Rochester NY
Posts: 5,721
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 34 Post(s)
Liked: 39
I used to run (4) Adcom 555mkII's for my subwoofer system. They are great stereo amps and have great bass respose for mains and centers.They do have a problem with content below 25hz. Mine would clip often during bass intense scenes.

You may want to concider a pro amp (QSC).
kgveteran is offline  
post #6 of 20 Old 02-22-2006, 11:16 AM
AVS Special Member
 
PLincoln's Avatar
 
Join Date: Nov 2003
Posts: 1,862
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
the 545 cannot be bridged.
PLincoln is offline  
post #7 of 20 Old 02-22-2006, 11:21 AM
AVS Special Member
 
PLincoln's Avatar
 
Join Date: Nov 2003
Posts: 1,862
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by Star Hawk
Thanks Wayne and whoaru99 for your replies. I decided not to hook it up bridged mono. I agree with Wayne that it could be risky since the amp does not have a bridged mono switch on it (probably for a reason). That reason might have been hit upon by whoaru99 in his reply that this amp is probably not designed for this task sinceit would be like driving a 2 ohm stereo load with the 4 ohm speaker connected to bridge mono. Until I can find a good high end subwoofer power amp, I will continue running my Adcom from one channel. 200 watts rms into 4 ohms will be ok for most movies, except perhaps War of the Wars with it's very demanding LFE. If anyone has a suggestion for one, please let me know. It must be a separate amp not designed to be mounted on the subwoofer. Those I have seen have smallish transformers and power supply filter caps ranging 10K to 15K uF, yuck. If money were no option I would go for the Gallo sub amp but it is expensive. Pro power amps
are another option but I don't want to mess around with balanced line inputs coming from
my unbalanced subwoofer line out (I have the Pioneer VSX-1015TX). Anyway, thanks again for your help and I am open to other options in sub amps.

Star Hawk
i am running the 545 as well driving one 15" atlas on each channel in IB config. I've never had it clip at my normal listening volume

http://www.cyberfrogs.net/photo/inde...diaroom&page=3

even with WOTW at -10 from reference, you dont mention if the box is sealed or ported?
PLincoln is offline  
post #8 of 20 Old 02-22-2006, 12:34 PM
AVS Special Member
 
kgveteran's Avatar
 
Join Date: Apr 2004
Location: Rochester NY
Posts: 5,721
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 34 Post(s)
Liked: 39
Great point! I run a sealed system.Not only is it sealed but I use a Marchand BASSIS to extend the low frequency response. I need pro amp juice.

An IB or ported may not have the demands that I put on them.

I could run one QSC 1450 for all four Tumults in an IB config.Even that would be over kill.
kgveteran is offline  
post #9 of 20 Old 02-22-2006, 01:46 PM - Thread Starter
Senior Member
 
Star Hawk's Avatar
 
Join Date: Feb 2006
Posts: 207
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
Quote:
Originally Posted by need4speed
i am running the 545 as well driving one 15" atlas on each channel in IB config. I've never had it clip
even with WOTW at reference, you dont mention if the box is sealed or ported?
The subwoofer enclosure is 3.2 cu ft and sealed. I did not measure the f3 due to lack of equipment, but according to the specs and plans for the enclosure for this small internal volume, partially filled with fiberfil stuffing, it should be ~25 HZ. The 545 is a good amp and even drives a 4 ohm nominal Z driver like the 12" Titanic without clipping. But I have not tested it yet with the recent War of the Worlds release. If I do view the movie I will probably use my Pio amp -10 db subwoofer out attenuator just to be on the safe side.
Star Hawk is offline  
post #10 of 20 Old 02-22-2006, 01:58 PM - Thread Starter
Senior Member
 
Star Hawk's Avatar
 
Join Date: Feb 2006
Posts: 207
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
Quote:
Originally Posted by kgveteran
I used to run (4) Adcom 555mkII's for my subwoofer system. They are great stereo amps and have great bass respose for mains and centers.They do have a problem with content below 25hz. Mine would clip often during bass intense scenes.

You may want to concider a pro amp (QSC).
Thanks for the suggestion. Others have mentioned the QSCs too. Sounds like it will be worth taking a look at them.
Star Hawk is offline  
post #11 of 20 Old 02-22-2006, 02:30 PM - Thread Starter
Senior Member
 
Star Hawk's Avatar
 
Join Date: Feb 2006
Posts: 207
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
Quote:
Originally Posted by kgveteran
Great point! I run a sealed system.Not only is it sealed but I use a Marchand BASSIS to extend the low frequency response. I need pro amp juice.

An IB or ported may not have the demands that I put on them.

I could run one QSC 1450 for all four Tumults in an IB config.Even that would be over kill.
What interconnects did you use to go from your HT receiver (or discrete HT preamp) to your QSC 1450. The specs I just reviewed only listed balanced line inputs:
"Barrier strip, XLR and 1/4" balanced inputs plus Speakon and binding post outputs provide easy connections." Unless your HT receiver has a balanced subwoofer line out, did you make or buy special interconnects? What about impedance matching?
I wanted to avoid this, unless there is an easy way around it.
Star Hawk is offline  
post #12 of 20 Old 02-22-2006, 02:38 PM
 
Targus's Avatar
 
Join Date: Jan 2006
Posts: 2,617
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
To feed a balanced input with an unbalancedsource, connect the hot to XLR pin 2, and the sheild(ground) to XLR pin 1.
There is no need to worry about impedance matching. The input impedance on that amp is 20K...it bridges the source.
Targus is offline  
post #13 of 20 Old 02-22-2006, 03:02 PM - Thread Starter
Senior Member
 
Star Hawk's Avatar
 
Join Date: Feb 2006
Posts: 207
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
Quote:
Originally Posted by Targus
To feed a balanced input with an unbalancedsource, connect the hot to XLR pin 2, and the sheild(ground) to XLR pin 1.
There is no need to worry about impedance matching. The input impedance on that amp is 20K...it bridges the source.
It sounds simple enough. Another question for you. Would it be better to buy a balanced line cable and cut off the XLR connector at one end and solder an RCA plug hot lead to the corresponding pin 2 wire and the shield to the corresponding pin 1 wire? Or take a length of unbalance cable, cut off the RCA plug at one end and solder an XLR connector (male, right?) pin 2 to the hot lead and the pin 1 to the shield. Does it make any difference which way?
Star Hawk is offline  
post #14 of 20 Old 02-22-2006, 05:24 PM
 
Targus's Avatar
 
Join Date: Jan 2006
Posts: 2,617
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Quote:
Does it make any difference which way?
Go with whatever is cheaper, it won't matter either way.
Targus is offline  
post #15 of 20 Old 02-22-2006, 06:50 PM
Senior Member
 
bonedoc2be's Avatar
 
Join Date: Oct 2002
Posts: 321
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 11
I have a 15" titanic sealed (~3.5cuft) and I run it off a QSC 850 bridged mono=830Watts. I bought the amp at Guitar Center and they had a cheap (8 bucks) cable for converting the XLR to plain old rca. Works great. I just use a home made coaxial cable with rca's on both ends (canare cable and connectors) and use the adapter cable (about 8 inches long) to connect to the rca at one end and plug the XLR into the amp input. On my qsc there is a switch on the back for bridging and you use the gain for channel one but it uses the power from both. No soldering involved and the sub is seriously impressive.
bonedoc2be is offline  
post #16 of 20 Old 02-23-2006, 01:06 PM - Thread Starter
Senior Member
 
Star Hawk's Avatar
 
Join Date: Feb 2006
Posts: 207
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
Quote:
Originally Posted by Targus
Go with whatever is cheaper, it won't matter either way.
Great! Now I need to decide which QSC to buy. Thanks.
Star Hawk is offline  
post #17 of 20 Old 02-23-2006, 01:42 PM - Thread Starter
Senior Member
 
Star Hawk's Avatar
 
Join Date: Feb 2006
Posts: 207
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 12
Quote:
Originally Posted by bonedoc2be
I have a 15" titanic sealed (~3.5cuft) and I run it off a QSC 850 bridged mono=830Watts. I bought the amp at Guitar Center and they had a cheap (8 bucks) cable for converting the XLR to plain old rca. Works great. I just use a home made coaxial cable with rca's on both ends (canare cable and connectors) and use the adapter cable (about 8 inches long) to connect to the rca at one end and plug the XLR into the amp input. On my qsc there is a switch on the back for bridging and you use the gain for channel one but it uses the power from both. No soldering involved and the sub is seriously impressive.
I am definitely going to order a QSC. I was looking at the RMX1450 but for $100
less I can still get all the power I'll need from the model you have, the RMX850. And I am back full circle 'cause I bought my 12" Titanic at Parts Express. I was not impressed by their subwoofer amps and so I had the idea of trying my old Adcom 545 amp which works ok but may wimp out on real powerful deep bass LFE. So all the time the amp I really need is right under my nose. I will check out PE's pro cables at the same time to see if they have something like yours. Thanks for your very helpful suggestions. :cool:
Star Hawk is offline  
post #18 of 20 Old 02-23-2006, 06:03 PM
AVS Special Member
 
whoaru99's Avatar
 
Join Date: Dec 2004
Posts: 6,960
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 67
There seem to be quite a few guys running cheaper pro amps such as Behringer (sp?) Samson, Blue Ice, and others. I can't vouch for any of these, but quite a few people claim success for sub duty at a lower price than Crown, QSC, etc.

Just because there is a knob doesn't mean you should turn it.
whoaru99 is offline  
post #19 of 20 Old 02-23-2006, 08:20 PM
Member
 
fraDcat's Avatar
 
Join Date: Apr 2001
Posts: 153
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Id say go with as much power as you can. If you can swing the extra 100 for a QSC 1450 I'd go that route just incase you decide you want to upgrade in the future. Or maybe a Behringer EP2500, it's around the same price as a QSC RMX 850.

As far as the quality of any I can't say as I use a Kiega 1000w plate amp with my Tumult. If I could do it all over again I'd go with a pro amp with ATLEAST 1400-1500 watts. The only issue is all but the Crown K1 or K2 use fans so you may have some noise from it. It bothers some folks.
fraDcat is offline  
post #20 of 20 Old 02-26-2006, 01:52 PM
AVS Special Member
 
kgveteran's Avatar
 
Join Date: Apr 2004
Location: Rochester NY
Posts: 5,721
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 34 Post(s)
Liked: 39
Fan noise stinks! I did a fan mod which helped, but nothing beats no fans at all.

They all may be going in the basement soon! :D
kgveteran is offline  
Closed Thread DIY Speakers and Subs

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off