More power for LMS Ultra 5400s? - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 21 Old 04-26-15, 08:16 PM Thread Starter
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More power for LMS Ultra 5400s?

I have a couple of LMS Ultra 5400s in 7 ft. ported enclosures. Currently I am using a Behringer EP 2500 amp for each one.

The room where these are located is too large in cubic volume, being about 13 feet high, 33 feet long and 20 feet wide. To get any volume out of these, the Behringer's yellow light is frequently lit, which to me says they are in clipping range. I had to add a butt kicker under the floor to get some sensation of impact, because these subs are not really slamming the way I would like them to ? not that I know that is possible anyway.

I'm trying to figure out a choice of amps to drive these to higher levels. My first question is whether or not that is a good idea? Is the Behringer EP 2500 already putting out enough juice to fully take advantage of the dynamic range of the LMS 5400? Or is there a lot of unused headroom?

If it is reasonable to add more power, my first (un) educated guess would be to get another pair of Behringers and bridge them, so I would have two amps for each speaker, using one bridged amp for each side of the woofers for a total of 4 amps. Not sure how that would work out, but it would be the most economical.

Another thought would be to get one of those knock off Chinese amps, but I am not at all certain that's a good idea.

Any reasonably priced amp suggestions that can outperform the Behringers would be welcome.

Of note, the rest of the set up is a Lexicon MC 8 pre-pro going to an Audyssey sub woofer equalizer. I have not put on a Samson S-Convert, but since I'm clipping already and I am not out of adjustment range for the Lexicon when setting the speaker dB eq, I'm not sure what good it would do? Any advice in that regard would also be appreciated.

Thanks very much!
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post #2 of 21 Old 04-26-15, 08:44 PM
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Re: More power for LMS Ultra 5400s?

Assuming you're running the EP2500 in bridged mono it's got the potential to output around 2500 watts, which is above the nominal for the LMS 5400. The driver can handle a lot more, but it's not as though you're starving them. Since it sounds like you're quite dissatisfied I'm not sure upping the wattage will provide the improvement you seek; some, perhaps, but significant? I'm not so sure of that. Frankly it sounds to me like you need more subwoofer, not more amp.

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post #3 of 21 Old 04-27-15, 06:55 AM Thread Starter
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Appreciate the reply. I'm out of room for more subs so may have to take what I've got. I wonder if I don't understand the amps fully, though.... If the clip light is yellow, is that actually clipping, or does it have two modes, yellow and then red? If that's the case I may have more to go....
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post #4 of 21 Old 04-27-15, 08:28 AM Thread Starter
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Another point is that the amps are not being run in bridged mono. They are run as two channels to each sub, with each channel driving one side of the motor. So each sub has two channels of input. That's what makes me think I could use two bridged amps for each sub, with one amp for each channel.
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post #5 of 21 Old 04-27-15, 10:02 PM Thread Starter
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Re: More power for LMS Ultra 5400s?

OK, in my first post I wrote this: "To get any volume out of these, the Behringer's yellow light is frequently lit, which to me says they are in clipping range."

This is obviously totally wrong -- that's the signal light -- so not only are the amps not clipping, they are probably really under fed and the amps have plenty of power. So could I change the question a bit?

The setup, as noted above, is a Lex MC8 going to an Audyssey, which then splits into two TRS connectors, one for each EP2500. I calibrated the SPL as usual, but the subs don't put out as much as I'd like, even though the dB seems to be correctly calibrated. I have the subs crossed over at 40 Hz.

How do folks set up subs to get the most out of them? The gains are cranked up all the way, so I guess the first step is a bump box? I understand the Samson is NLA and assume the Cleanbox is the one?

How do you all set the room bass level? It seems like calibrating it to the dB meter doesn't produce adequate bass?

Any advice would be much appreciated.
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post #6 of 21 Old 04-28-15, 05:34 AM
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Re: More power for LMS Ultra 5400s?

I may have missed it, but whats feeding the Behringer EP 2500?
It may be the input voltage isn't high enough. But without more info my guesses are
1. MLP relative to subs,
2. Sub placement in room
3. Try running bridged mono
4. interconnects
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post #7 of 21 Old 04-28-15, 05:56 AM
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I'm thinking you just might not have enough sub for that space. My room is similar in size to yours (8000 cu ft) and for me to get the output I wanted I went with 2 FTW-21's. I'm running an iNuke6000DSP amp which is putting out 2200 watts at 4 ohm's to each driver. They are each in roughly 8 cu ft sealed boxes and I have roughly 120db @ 12hz at the listening position 13 feet away (average distance for both) from the subs.
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post #8 of 21 Old 04-28-15, 09:26 AM
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Re: More power for LMS Ultra 5400s?

Quote:
ham wrote: View Post
The setup, as noted above, is a Lex MC8 going to an Audyssey, which then splits into two TRS connectors, one for each EP2500.
Where did you find an RCA to TRS splitter? As far as I know there is no such thing. No reason for it as a 1/4" TS plug will work for any TRS input.

And if really is RCA to TRS, who knows how it is wired internally? If it is sending the signal (-) to the tip of one of the TRS plugs that has the same effect as flopping the polarity of one of the speakers. Besides, a splitter, even the right one, unnecessary. You can set the amp for parallel mode and run both channels from a single input – see p. 7 of the manual.


Quote:
The gains are cranked up all the way, so I guess the first step is a bump box? I understand the Samson is NLA and assume the Cleanbox is the one?
Can’t say for the Audyssey specifically, but a problem with some bass processors is that they only apply cutting filters, which serves to reduce the signal level on the back end of the processor. A good test might be to take the sub EQ out of the signal chain and see what that does to your overall sub level.

Also, have you tried pushing the MC8-s sub output higher? You do have the EP2500's low cut filters turned off, right?

Regards,
Wayne



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post #9 of 21 Old 04-28-15, 10:10 PM Thread Starter
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Re: More power for LMS Ultra 5400s?

***********************
I may have missed it, but whats feeding the Behringer EP 2500?
It may be the input voltage isn't high enough. But without more info my guesses are
1. MLP relative to subs,
2. Sub placement in room
3. Try running bridged mono
4. interconnects
***********************


The pre/pro is a Lexicon MC-8 with unbalanced outputs. It goes into an SVS Audyssey sub eq, which uses 8+ microphone positions throughtout the room to balance the output of the subs -- purpose is to remove interference for flat response from multiple subs. Now that I look, it seems to be out of production.
http://www.svsound.com/aseq_1_operat...1_1_lowres.pdf

Not sure what MLP is.

Placement is in the front of the room, about 2 ft from each wall.

I'll try bridged mono once I exhaust all other options

Interconnects are RCA to 1/4" TS to each Behringer in Input 1 -- Not TRS as I stated above -- memories of TRS-80, I imagine....

I attached a pic (sideways!) of the DIP switches. It looks like it is set up for parallel mode, no low pass filter, and clip protection.

Wayne, I thought about pushing the output on the pre/pro higher, but maybe it is worth getting a bump box? The subs come up to 70 dB pink noise easily when the Lex is going through calibration for each speaker, which is what made me think there was too little power.
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post #10 of 21 Old 04-29-15, 07:17 AM
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Re: More power for LMS Ultra 5400s?

Quote:
ham wrote: View Post
Not sure what MLP is.
Main Listening Position. Basically, the primary seating location.

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