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More power needed for Tempests?


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133 replies to this topic

#1 of 134 David Giesbrecht

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Posted August 17 2003 - 09:31 PM

As some of you know I have received an RMX1450 to power my two Tempest sealed subs (230L). I guess what I want to know is how much power is required for them to reach their potential? because 450 watts doesnt seem to cut it. I've tested them with some real bass heavy material (LOTR,JP3 etc.) and seem to be able to clip the amp quite easily with that material and the subs arn't even breaking a sweat! My first thought was that I had one of the low frequency filters on but i've doubled checked many times and all filters are off. I've been thinking about getting a second RMX1450 and bridging one amp into each sub. I know it sounds crazy but I think the subs could probably handle it, not continuesly of course but for short transients I think they could, and theirs nothing wrong with having a little extra headroom! I don't even want to venture a guess at how much power would be required to drive a Tumult full out!

#2 of 134 Pete Mazz

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Posted August 18 2003 - 09:47 AM

It should take ~170W to reach max excursion at 20Hz, according to WinISD.

Pete

#3 of 134 TimForman

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Posted August 18 2003 - 10:37 AM

Since the Tempest is rated at 750W max with both VCs wired I can see the amp giving out before the drivers. It takes a lot of power down low in a sealed enclosure to hit the levels you seem to be looking for. Another amp will get you closer. I've used a 1000W amp on my sealed Tempest and could only get the gain up about 3/4 on LOTR. (That was loud enough thank you).

#4 of 134 David Giesbrecht

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Posted August 18 2003 - 03:19 PM

Quote:
It should take ~170W to reach max excursion at 20Hz, according to WinISD.


That is true, but a program source usually contains alot more than one frequency at a time so you would need alot more than 170 watts to push them to their max unless you enjoy listening to test tones Posted Image

#5 of 134 Jack Gilvey

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Posted August 18 2003 - 10:54 PM

Quote:
That is true, but a program source usually contains alot more than one frequency at a time so you would need alot more than 170 watts to push them to their max unless you enjoy listening to test tones

Not sure what you mean by this.
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#6 of 134 David Giesbrecht

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Posted August 19 2003 - 03:11 AM

Quote:
Not sure what you mean by this.

Right now I do have 450 watts to push each one of my Tempests but if I wanted to pull 450 watts at 20 hz without clipping the amp the only way to do it would be with a pure sinewave. If I wanted to produce 2 sinewaves at the same time with the amp at the same gain it would require 900 watts to do this and 1350 for three sine waves etc, etc...
Program material contains multiple sine waves all at the same time and each one takes a little amplifier power away with it. If it takes 170 watts for a Tempest to reach XMAX at 20 hz thats almost half my power gone already.

#7 of 134 Brian Bunge

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Posted August 19 2003 - 03:59 AM

450W is more than enough power. You're getting caught up in analysis paralysis.
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#8 of 134 Hank Frankenberg

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Posted August 19 2003 - 04:40 AM

Brian, "analysis paralysis" came up in Six Sigma statistical analysis training last week. It's a common pitfall. Good catchPosted Image

#9 of 134 TimForman

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Posted August 19 2003 - 06:20 AM

Now that I've educated myself on the model 1450 these guys are correct. 450W per sub should be plenty. Are you sure there isn't a problem with the room? Perhaps you're sitting at a null spot during the movies.

#10 of 134 David Giesbrecht

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Posted August 19 2003 - 09:25 AM

Quote:
Perhaps you're sitting at a null spot during the movies.

I have measured the frequency response of the subs and trust me there is no null spot in any of the listening positions.

Heres what I got at the listening position.

10 hz 80.4 db
15 hz 84.5 db
20 hz 89.3 db
25 hz 89.6
30 hz 90.4 db
40 hz 90.7 db
50 hz 89.5 db
60 hz 89 db
70 hz 88.9 db
80 hz 88 db
90 hz 89.1 db
100 hz 89.1 db

That looks pretty good to me and when I sit in any other spot during the movie the bass sounds just as good infact it sounds exactly the same.

Quote:
450W is more than enough power.


If it was than my amp wouldn't clip at my normal listening level. I don't know if I'm listening at reference level or not, all I know is that it is loud and thats the way I like it! Posted Image

#11 of 134 Jack Gilvey

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Posted August 19 2003 - 10:14 AM

Quote:
Right now I do have 450 watts to push each one of my Tempests but if I wanted to pull 450 watts at 20 hz without clipping the amp the only way to do it would be with a pure sinewave. If I wanted to produce 2 sinewaves at the same time with the amp at the same gain it would require 900 watts to do this and 1350 for three sine waves etc, etc...
Program material contains multiple sine waves all at the same time and each one takes a little amplifier power away with it. If it takes 170 watts for a Tempest to reach XMAX at 20 hz thats almost half my power gone already.

Do you have a reference you could point me to for this analysis? Never heard anything like this.
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#12 of 134 David Giesbrecht

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Posted August 19 2003 - 10:33 AM

Quote:
Do you have a reference you could point me to for this analysis? Never heard anything like this.

Actually I don't I used common sense.
Can you honestly tell me I'm wrong though?

#13 of 134 Jack Gilvey

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Posted August 19 2003 - 10:47 AM

Quote:
Actually I don't I used common sense.

Ahh, ok.

Quote:
Can you honestly tell me I'm wrong though?

It doesn't make sense to me (lots of anecdotal evidence to the contrary to those with experience), but since it's your claim, the burden of proof is on you.
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#14 of 134 David Giesbrecht

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Posted August 19 2003 - 11:15 AM

Try running a pink noise test through your system, shut off your mains and try to bottom out your subs. I couldn't do it with 450 watts not even close the amp clipped long before the subs reached their xmax.

The 450 watts I have is divided up between all the sine waves contained in the material.

#15 of 134 Chad Kuypers

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Posted August 19 2003 - 11:24 AM

I can think of one thing that would definitely be the cause of your problems. I used to own a Crown CE-1000 that put out nearly the same amount of power that your QSC amplifier puts out. It put out 450 watts into each channel at 4 ohms.

HOWEVER, this only seemed to work when I ran each channel seperately to each subwoofer. I can't explain why, but when I bridged the amplifier (yes the wiring was correct) it would run out of steam and clip very often. I could even get it to shut down if I pushed it really hard. When running each channel seperately, I never had this problem and never saw the clip lights. With each channel of the amplifier hooked independantly to each subwoofer driver, I could make mince-meat out of the subwoofer drivers and the amplifier wouldn't even blink.

That being said, if I run 400+ watts to a Dayton DVC 15" etc. in a larger sealed enclosure, I can bottom it out pretty easily. I can't imagine that 475 watts x 2 would not be more than enough for your two sealed Tempests. If you have the amplifier bridged, try "seperating" the amplifier channels and running one each to a subwoofer. I hope that this helps.

#16 of 134 David Giesbrecht

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Posted August 19 2003 - 11:41 AM

I currently have the amp connected in stereo and I have tried bridge and it didn't seem to make much difference, even if I did run it in bridged mode the amp is not recomended for 2 ohm operation in bridged mode.

#17 of 134 Jack Gilvey

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Posted August 19 2003 - 12:02 PM

Quote:
The 450 watts I have is divided up between all the sine waves contained in the material.

Ahh, I see. And do some of the waves takes more of the watts, or are they pretty much divided equally?
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#18 of 134 David Giesbrecht

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Posted August 19 2003 - 12:28 PM

That of course depends on the material and how its recorded.
LOTR must have a fairly complex mix of sounds because my amp clips quite easily during the moria battle scenes with the belrog and the subs arn't hitten their bottoms thats for sure.

#19 of 134 Brian Bunge

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Posted August 19 2003 - 02:14 PM

Chad,

Is it possible that when running both channels at once your amp's current demands are greater than what it can actually supply?

Jack,

Posted Image
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#20 of 134 Pete Mazz

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Posted August 19 2003 - 03:05 PM

Do you have the Tempest wired in parallel (+ to +, - to -) for a 4 ohm load?

Pete


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