I found my sub problem...

[formica]

QSC RMX are good inexpensive amps... their main drawback for pro use is their weight, but that is a less important factor in permanent in-home use. They are stable to 2ohms stereo (or 4 ohms mono) but they prefer a higher impedance load... and that explains the limited frequency response stated in "4ohm mono" use. It is less of a factor in home subwoofer since we won't push the amps to their limits hours on end...

Note that I believe the RMX amps use 24V fans... so they are a little more expensive and harder to get. I ended up using a panaflow 24V low speed unit

There is a reason they've been imitated by many manufacturers

Rob

[Scp53]

Well i just borrowed the rmx 1450 new from a shop. I'll have it hooked up in a bit and post back tonight. cheers, scp53

[Scp53]

well the amp is REALLY nice. i watched mostly ht and was impressed. now i can go by a meter on the side to see if its clipping or not. for ht it never does at all. the ONLY problem i have is with the filter on it. you can have it roll 3db down by 50hz or 3 db down by 30 or no filter at all. I found that with no filter there is really really really subsonic stuff that clips the crap out of the amp(like cd "noise"- 5hz stuff). i would hardly have my music up to 80 db and id get a load of cone movement with the clip light on steady. i set the switches so the filter is at 30hz now. that fixed the problem.

btw, i read in the manuel and it says to use a filter unless you have a filter(receiver obviously doesnt slope off much until reall really really deep stuff) before it or you are playing low level studio mixing to check for noise.

so anyways ht is very good(ill play more movies tomorrow) but for shania twain greatest hits cd i still get clipping . i think that mix is burned "hot" or something. seriously, the cd must be burned hot if i have a 30 hz filter on a 1400 watt 4 ohm amp(bridged) and i still clip it. however, this sounded much much better than when i had the 250 on it(and i know that was clipping too). in fact with slight clipping its hardly noticable on this new amp(because im not clipping it nearly as hard. ) the only thing i could think of is i switched it wrong? ill have to check it again. peace out .

scp53

[Scp53]

well the amp is REALLY nice. i watched mostly ht and was impressed. now i can go by a meter on the side to see if its clipping or not. for ht it never does at all. the ONLY problem i have is with the filter on it. you can have it roll 3db down by 50hz or 3 db down by 30 or no filter at all. I found that with no filter there is really really really subsonic stuff that clips the crap out of the amp(like cd "noise"- 5hz stuff). i would hardly have my music up to 80 db and id get a load of cone movement with the clip light on steady. i set the switches so the filter is at 30hz now. that fixed the problem.

btw, i read in the manuel and it says to use a filter unless you have a filter(receiver obviously doesnt slope off much until reall really really deep stuff) before it or you are playing low level studio mixing to check for noise.

so anyways ht is very good(ill play more movies tomorrow) but for shania twain greatest hits cd i still get clipping . i think that mix is burned "hot" or something. seriously, the cd must be burned hot if i have a 30 hz filter on a 1400 watt 4 ohm amp(bridged) and i still clip it. however, this sounded much much better than when i had the 250 on it(and i know that was clipping too). in fact with slight clipping its hardly noticable on this new amp(because im not clipping it nearly as hard. ) the only thing i could think of is i switched it wrong? ill have to check it again. peace out .

scp53

[DrWho]

ummmm, that is very wierd. For testing sake, try plugging your cd player directly into the amp and see if music makes it clip. (you can test with the dvd player too). I'm thinking there might be something wrong with your reciever or cd player. You should check cables for shorts and all that shnazz. Have you tried listening to music played through the dvd player? (do you even have seperate units?)

One other thing you can try is hook your pc audio output into the amp and see if you get clipping that way as well.

There is no reason for your amp to be clipping at such quiet volumes which leads me to believe that some unit upstream is somehow passing DC...perhaps some transistors are going bad or something like that. Anyways, do your best to isolate each piece in the signal path and determine what the culprit is. I bet once you get this sorted out that your 200 watt PE amp will start sounding good again.

[Scp53]

whats weird? the clipping with out the filter or with it? it makes perfect sense to me why it does it with out it. It says even the manuel there will be problems with out a roll off on the low end. it says with out a filter the roll off is at 5hz. I found i had a few switches wrong and now i got them fixed. as for clipping because of other equipment, i dunno? i have two different dvd players(both toshiba- sd4900 cheapo and a sd2715 which is a decent player for its time). both of those give me the same result. and i have had two different receivers used with the 250watt sub amp on the subs. a pioneer tube and the yamaha. i connected both with speaker level input and also the yamaha has been connected via lfe out. all connections yield the same result- amp clipping. oh yea, i have hooked it up to the pc too and i again get the same result(though havent done it with the mod yet).

however, this clipping is not near as much any more because i have modded the amp to be "flat"(not sure if you knew that).

btw, I need a amp anyways to drive my other sub. so i need to get one for sure . i was considering the 500watt plate amp from pe but thought i want something more long lasting and more useful(ie- drive mains or another sub). so to do that a pro receiver is pretty much the cheapest choice. and since im doing this ONCE, im getting a better make, so thats why i went with qsc over behringer and others. for sub use any decent pa amp would have done but i wanted to drive other things later on. ok, enough of my rambling on here.sorry it got so long. just tell me what ya all think of this. thanks

scp53

[DrWho]

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i would hardly have my music up to 80 db and id get a load of cone movement with the clip light on steady. i set the switches so the filter is at 30hz now. that fixed the problem.

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That is the wierd part. There is no reason that everything but dvds are clipping your amp. Throwing in a filter at 30Hz is like sucking the life outta the subs (they're supposed to play that low and even lower). I wonder if maybe your speaker wire has a half short somewhere in the middle or something, causing the amp to run into clipping ...that still doesn't explain why it doesn't happen for movies though.

Does anybody else find this wierd?

[formica]

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On 6/5/2005 12:29:02 AM DrWho wrote:

Does anybody else find this wierd?

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I agree it's very unusual we are talking about driving 1400W into a single Atlas 15 without bottoming the driver but clipping the amp?

This is well beyond the woofers power handling capabilities as well as being more than enough power to go past the woofers maximum excursion in any enclosure.

Scp53, either something is wrong... or you aren't explaining something clearly enough to us to understand what is wrong.... or it's very LOUD in you room but you want more?

I remember you mentioning that your subwoofer performed much better outdoors (or am I confusing people?) which means you have some pretty serious room effects. Is it possible you are driving you sub to incredible limits... but not hearing the frequencies you are expecting cause you are sitting in a room null?

I'm baffled.

Rob

[Scp53]

ok, first off i NEVER played a movie with the filter off. that was ONLY for a few songs.

i read the manuel and it says quote,

"Input filter-

WHAT IT IS

The low-frequency (LF) filter rolls off

signals below either 30 Hz or 50 Hz.

This improves bass performance by

limiting sub-audio cone motion,

making more power available for the

speakers' rated frequency range.

The filter settings for each channel are

controlled individually through the DIP

switch settings shown. When the filter

is turned off, a 5 Hz roll off protects

against DC or deep sub-audio inputs.

WHEN TO USE IT (OR NOT)

As a rule, your speakers will sound

better with proper filtering. Unless

you already have filtering in a

preceding device, match the setting

to the low frequency rating of your

speakers. Vented (bass reflex,

ported, etc.) speakers are especially

sensitive to cone over-excursion at

frequencies below their rated limit.

The 50 Hz filter works well with

most compact full-range speakers,

and has a slight boost at 100 Hz for

greater fullness. The 30 Hz filter is

intended for subwoofers and large

full-range cabinets. The "off"

position should be used only for

applications such as studio playback

monitoring, where you need to know

if there are unwanted sub-audio

signals present in your mix."

does that explain it at all? basically this amp has NO rolloff on the low end(no rumble filter). NONE. my 250wt plate amp has an f3 at 19hz with no boost or any eq. so you can see that the roll off between these two amps is pretty different. this is why it was clipping. btw, my wires are fine. i have checked them.

so, does this make any more sense? if i had a eq before the amp other than the receiver it would work. i would need to roll it at around 15-20hz i think. let me know what you think. thanks

scp53

[DrWho]

Ok, the RMX series of amps are a "cheap" pro line, which means "newbie" users are most likely using the amps, which are intended for PA use. The manuals were basically written to explain the features to newbie PA mixers. When doing a live show, you will rarely find a subwoofer that goes lower than 40 or 50Hz just because it takes so much cone area to produce any useful SPL. 135dB at 40Hz is one thing, but 135dB at 20Hz is over 8x the excursion (or is it 4x? i forget). The reason they provide those filters for live shows is because a low enough signal will easily put the speaker into very high distortion levels. Though a live kick drum is basically a signal around 80Hz with the snap at 1kHz...you get a lot of wind movement which could translate to a let's say 10Hz note. When that signal gets out to the speaker the kick is going to sound like crap because it's all distorted due to the overloading occuring at the lower inaudible frequencies. Throwing in a High pass filter cuts out these low notes and you don't have this problem. But as you move up the ranks into better and better PA systems, you start to find subwoofers capable of 30Hz (usually not much lower) and you won't need these silly high pass filters to protect subwoofers not designed to go very low.

Recorded music on the other hand doesn't suffer from these things so there's really no need to worry about it. As long as your cone movement is controlled from 30Hz and down (which it is if you went with the recommended design), then you don't want your amp doing any EQ and getting rid of any low bass information.

There is no way (even with crazy acoustics) that your sub is only putting out 80dB with 1400 watts. If that were the case, then something in your signal chain is soaking up about 1399.5 watts (if your impedance really is 4 ohms)...there's gotta be a short somewhere, it's the only explanation.

[Scp53]

well first off, i took the amp back. i decided its too much for me right now.

so you dont think that there could be real deep stuff(unwanted noise) on a cd or dvd? is that manuel full of crap? i think im gonna try the 500 from pe. that has a steeper x over(24db vs my 12db on the 250watt), soft clip, obviously more power, and parametric eq. what do you think? (or should i check for a short? btw, the wire i was running for the pro amp is the same i use for my mains and they work just fine.)

thanks, scp53

[DrWho]

Well the manual isn't full of crap, but it was written for a different application. There are many factors involved with live sound such that certain situations benefit from cutting out the deep bass. It's always better to have a sub that sounds punchy with very little deep bass than it is to have a sub playing rumbly low notes making everything muddy sounding. We don't have these issues at home so there's no need to worry about it. (things like feedback - the #1 issue here, stage noise, crowd noise, vibrations everywhere, etc etc).

Technically I suppose it's possible that a recording could be made for this to happen, but good music is never going to leave the studio sounding that way. It's just a totally different beast.

Before you go running around buying new amps, I would try to find the problem. Have you always gone through your reciever when conducting tests? Try sending a full range signal direct from the player or pc and try to determine whether or not the amp is clipping. I suppose your reciever could be the culprit.

[colterphoto1]

"It's always better to have a sub that sounds punchy with very little deep bass than it is to have a sub playing rumbly low notes making everything muddy sounding. "

EXACTLY Dr Who. Lets keep it real- or musical. Too much muddy, boxy bass out there.

Michael

[Scp53]

i talked to chad today(didnt order a amp yet btw. i might wait?) and he said the only thing better then my amp would be the 500 from pe. he said i could wire it in series(has one big and one smaller coil fyi) and that would raise the motor bl from 12 to 15. we said he can here a sq difference with the stronger motor. he also said this would give me the most spl. any comments?

btw, no one has really told me how to test the system for a short or anything like that(although from what ive tested, there are none). thanks,

scp53

[formica]

It would be easier if we could hear and see your sub first hand.

The Atlas 15 is rated for 300W... for which it would make it excursion limited below 16Hz (ie: it'll bottom out with less than 300W below 16Hz) and thermally limited above.

If you figure that Ascendant conservatively rated their power handling... and therefore use 500W. This would mean it's excursion limited below 17Hz, and thermally limited above.

These would produce about 118db at 80Hz but they would roll of to 108db (111db) with a 300W (500W) amp.

Not sure what you are listening to, on them... but a pure sinewave tone would be pretty loud

Rob

[Scp53]

as far as power rating, Chad told me some time ago that there higher than whats in the specs(i think 600 or so. about what you guessed). so, does the amp clipping from cd noise make ANY sense? seriously, that must have been whats happening. in terms of the spl you said, ya thats about what it does. btw, i never said(now that the amps modded) that this thing cant put out with 250 watts. i would say at 2m i can hit 110 clean and a lot of content. thats with the sub semi corner loaded(is there such a thing) and me near the opposite wall. and as for sine waves, i plan to run none. id rather no take the chance of heating the **** out of the coil. so what would YOU suggest i do? a new amp? do you think that new amps steeper x over will help clean things up? to me, that could be taking away a sizable amount of power. pe offers 45 day money back satisfaction. your help is greatly appreciate. scp53