Confused how I bottomed my sub

[tuxedocivic]

Hey all,

 

I figured the experts are here, despite the low traffic.

 

I have 4 Creative Sound Solutions Trio 12s. Two are in a dual opposed. Two in single cabs for spreading. Each driver gets about 75L and is heavily stuffed with insulation. Last night I switched some things around and wired the dual opposed to have it's own stereo amp. It's a really old small Pioneer amp that I literally can't find any info on the web about. I have no idea what kind of power it makes. But it's old, and it's small. Weighs a lot though. I figure it can't make more than 100 watts. The other two subs I wired to some other amp I had. I did this to try and get more amp power because before I was just using the pioneer. Well, it worked, the subs were all getting more power. I have some gain adjustments to make, but all in all, there was definetely more output there.

 

So I was watching star trek, knowing fine and well there's ULF output. Keep in mind I haven't done any eq. So no boost to the low end. The subs were going crazy and at one point I bottomed them out (the dual opposed cab with the Pioneer amp). I don't understand how that's possible. Even in a cab 4 times the size they shouldn't be overdriven with my amp, assuming I'm right that it doesn't put out much power.

 

Is it possible my Pioneer amp is putting out more than I would think?

Is it possible the Trio 12 has less xmax that spec'ed (20mm)?

What should I measure to figure out what's going on?

 

Thanks for any help.

[Infrasonic]

Are you sure you actually 'bottomed' the drivers mechanically? You may just be clipping the Pioneer amp which can sound pretty awful.

[tuxedocivic]

Ya I suppose that's very likely considering the amp's assumed whimpyness. But it didn't sound like clipping afaik. It was an audible "bonk" sound and it was during ULF. Twice, quite close together. Only a second apart. And only once during the whole movie. But I could tell the subs sounded on edge during the whole movie.

 

What would clipping sound like in a sub?

[maxmercy]

It sounds like a lot of non-LF noise (higher in freq).  Due to ELC, it sounds much louder and unpleasant.  It is very likely that the ULF the signal 'asked for' was clipped by the amp or sub (prob amp).  Only way to find out if you were hitting physical limits on the driver is to run a toneburst through the amp/sub combo in question and listen for metallic 'clanging' noises (pushing to xmech) vs the distortion of higher harmonics being produced by amp clipping vs coil leaving the gap (but still within xmech).

 

REW now has these tonebursts, IIRC.....and I am creating some ULF ones for the Test Disc (still in process).

 

If you know someone with an oscilloscope (or make a voltage divider and possibly sacrifice your soundcard), you can test the amp.  

 

 

JSS

[tuxedocivic]

Ok screw it. I'm just gonna buy a better amp and stop screwing around with my garbage amps laying around here. Makes sense that I clipped the thing and it squaked back. It was kind of squaking at me the whole movie, but the sound I heard must have been a hard clip or something.

 

Thanks guys.

 

Ryan

[Infrasonic]

Good thinking.

[tuxedocivic]

Anyone wanna recommend a better amp? The Peavey IPR1600 with or without dsp is tempting. I'm thinking $300, must not have a high pass like the crowns, and I don't care if it has a fan. My problem is that it sounds like a lot of amps have a high pass. Like the Crown XLS and the more powerful Peavey IPRs. Are the iNukes ok to ULF?

[maxmercy]

Damn, 

 

Haven't tested my iNUKE to ULF, Haven't made the voltage divider and bought the dummy load.....since it will be a 'backyard sub' amp anyway, doesn't have to do much below 30Hz.....

 

You can always go tried and true EP4000....every now and again Wally World carries them:

 

http://www.walmart.com/ip/Behringer-Stereo-Power-Amplifier/17656014?wmlspartner=je6NUbpObpQ&sourceid=04833837121735781766&affillinktype=10&veh=aff

 

 

JSS

[lilmike]

Define ULF.... 

 

My iNuke 3000 seems to deliver the goods to a bit below 10 Hz, though I run out of sub passband at 18 or so. It measured pretty flat though, basically as flat as my soundcard is. 

 

 

My Berry 2500 seems to be a bit better for the deep stuff, but it takes two hands to carry it...and a dedicated circuit to plug it into.

 

The iNuke 3000 is playing nicely with the rest of the system on a shared 20 A circuit. I was blowing candles out with the sub too, so it is not like I wasn't pushing things. I've got it bridged into an 8-ohm cabinet, and I see clip lights on occasion. 

[nube]

I'd be wary of getting the iNuke series for the bottom octaves.  There was a post linking to testing of it, and here's the graph I pulled off that link with my analysis of it:

 

http://www.avsforum.com/t/1435795/first-diy-project-for-a-guy-looking-to-upgrade-multiple-sealed-18s/900#post_23080227

 

Looks to me like it has significant roll off starting at 10hz.  The link to the testing is just a few posts before mine in the same thread.  I'd say, for the money, go with the EP4000, as it doesn't (afaik) exhibit this behavior down low.

[lilmike]

Seriously - it all comes down to where you want to get off the train. 

 

20 Hz? Easy, lots of choices. Chuck's testing at AVS shows which ones to avoid. 

15 Hz? Well, the pack is getting thinner, but any of the usual suspects should do fine.

10 Hz? This is where choices really get thinned down, but the EP is still a good option, and the iNuke is just starting to roll off.

5 Hz?  Can't help, cause I can't measure things that low accurately enough to hang my hat on the results.

 

I'll be honest - I got off the train at the 15 Hz stop, so I don't have a lot to add regarding ULF, other than my quick measurement of my amp that I posted above. I'd personally have no concern using the iNuke to 10 Hz if I needed that amount of extension. My measurements show that the amp is just starting to roll off at that point, and is down 3 dB at 5 Hz, but as Bosso points out, everything else in the chain is starting to roll off there too, as is my measurement gear. Everything rolls off at some point, DC is a fundamental limit.

 

With my system currently, the iNuke is not the weak link, and neither is my sub. The DSP options have value, even if adjustment is limited to above 20 Hz. Don't think I am blindly "standing by my amp" here. The OP asked about the iNuke, I am offering my first-hand experiences with and measurements of mine. I too was considering the Peavey IPR 1600, but was able to grab the iNuke 3000 DSP for less. I own several EP2500s, as well as an older QSC. The iNuke was purchased primarily as a testing amp, cause it is silly-easy to carry around and the DSP keeps me from hurting things. As it turns out - it is also a fine sub amp for my current situation. Some day I will fire up the EPs again....I've got a house to build first.

[DS-21]

Ya I suppose that's very likely considering the amp's assumed whimpyness. But it didn't sound like clipping afaik. It was an audible "bonk" sound and it was during ULF. Twice, quite close together. Only a second apart. And only once during the whole movie. But I could tell the subs sounded on edge during the whole movie.

 

What would clipping sound like in a sub?

 

IME, an audible "bonk" sound.

 

Here's a good thread on PETT with different drive-units and amps, but the same problem. Switching from those horrid old PE 240W plate amps to a very good multichannel amp (Boston Acoustics rebadge of the Sherwood A-965) fixed it for Brandon, even though on paper the A-965 is 1.5dBW less powerful.

 

Anyone wanna recommend a better amp? The Peavey IPR1600 with or without dsp is tempting. I'm thinking $300, must not have a high pass like the crowns, and I don't care if it has a fan. My problem is that it sounds like a lot of amps have a high pass. Like the Crown XLS and the more powerful Peavey IPRs. Are the iNukes ok to ULF?

 

It's a smidge over $300 but I'd recommend the Crest ProLite 2.0, which is finally a real shipping product. (It was vaporware for quite a while.) It's basically Peavey's "adult" version of the IPR1600. Same basic amp, but (per its designer) a little more capacitance, and IMO more importantly the ProLite delete-options the IPR's hideous blue lasershow. I recently picked one up (eBay seller "audiosavings" regularly has them at $310-325 shipped) for my sister's forthcoming basement theater, and found it to feel considerably more solid than the IPR3000 I had for a time (steel vs. aluminum case), look an awful lot nicer, and is also quieter even with the stock fan. 

 

I think there's a DSP version too, but I've not played with it or looked into it at all. I'd rather use a miniDSP anyway.

[tuxedocivic]

Thanks all and thanks for the tip on the crest DS21

 

Thanks for the measurement lilmike. I'd like flat to dc, but ya know, not easy. 5hz would make me happy. I take it the Dayton Sa1000 isn't a contender considering it has 1 PEQ and a 12V trigger, it's attractive. Things I don't need, but attractive.

 

The ipr1600 is slowly high passed at 8hz. Not bad. Ep4000 is a little pricy but will consider it. Living in Canada makes some of your guys' excellent suggestions less excellent. I can wait until I'm in the states visiting family to buy though. For now ill just rewire the amps I have to a higher impedance and give up a few db for cleaner output.

[Bossobass Dave]

Seriously - it all comes down to where you want to get off the train. 

 

20 Hz? Easy, lots of choices. Chuck's testing at AVS shows which ones to avoid. 

15 Hz? Well, the pack is getting thinner, but any of the usual suspects should do fine.

10 Hz? This is where choices really get thinned down, but the EP is still a good option, and the iNuke is just starting to roll off.

5 Hz?  Can't help, cause I can't measure things that low accurately enough to hang my hat on the results.

 

I'll be honest - I got off the train at the 15 Hz stop, so I don't have a lot to add regarding ULF, other than my quick measurement of my amp that I posted above. I'd personally have no concern using the iNuke to 10 Hz if I needed that amount of extension. My measurements show that the amp is just starting to roll off at that point, and is down 3 dB at 5 Hz, but as Bosso points out, everything else in the chain is starting to roll off there too, as is my measurement gear. Everything rolls off at some point, DC is a fundamental limit.

 

With my system currently, the iNuke is not the weak link, and neither is my sub. The DSP options have value, even if adjustment is limited to above 20 Hz. Don't think I am blindly "standing by my amp" here. The OP asked about the iNuke, I am offering my first-hand experiences with and measurements of mine. I too was considering the Peavey IPR 1600, but was able to grab the iNuke 3000 DSP for less. I own several EP2500s, as well as an older QSC. The iNuke was purchased primarily as a testing amp, cause it is silly-easy to carry around and the DSP keeps me from hurting things. As it turns out - it is also a fine sub amp for my current situation. Some day I will fire up the EPs again....I've got a house to build first.

The thing is, it doesn't matter what your sub can do, the content is there regardless. Knowing the signal roll off is paramount because the signal begins with seriously strong content from 2-120 Hz in a LOT of soundtracks, and it only takes one of them in the right (wrong) situation.

 

Lots of folks are indiscriminately adding lots of shelf boost (I've seen posts mentioning >14dB of boost) below 20 Hz and running the sub trim hot to boot and if there aren't precautions taken amps will be the typical casualty, especially with a clone amp that's flat to 2 Hz with 14000 burst watts plugged into a 30A home run.

 

Most receivers and players are flat to 5 Hz which means 5 Hz is going into the amp and it doesn't matter much how rolled off the amp is at 5 Hz... most of them go nuts. Over the years I've used Crown, QSC, Marathon and American Audio big iron amps and a half dozen clone platform Asians. They all were flat to 5 Hz at least. The ones with poor protection circuitry are dead and buried and it always happened with WOTW-type content.

 

A shelf is doing nothing in most every case with content >20 Hz. Most everyone uses the rumble tone/RS meter to calibrate the sub trim level, then they bump it another +6dB. So, you cruise along using 500W and suddenly the content/signal chain/boost requires 15,000W to amplify a spread of 2-12 Hz.

 

Add to that the fact that the amp is seeing 7-10V when its sensitivity is set at or is global at 2V with "my amp knobs are at 12 O'clock" and look out.

 

This is the #1 reason for the clone-cooking in that AVS thread, driving the amp to way past full output with single-digit content that's boosted to >+6dBRL.

 

Capacitors are used to prevent DC offset. This doesn't necessarily mean that there will be a roll off, which is proven by the clones circuitry that keeps them flat to 2 Hz.

 

Here's a loopback graph of two popular digital EQ choices, Marchand Bassis and three versions of DC offset circuitry in my SEQSS:

 

 

You can see that we successfully eliminated DC offset while achieving virtually zero roll off. The Bassis has always been flat to 2 Hz and the other 2 are flat to <5 Hz. Others roll off sooner and steeper, but the point is that anyone who is gonna let 'er rip should be aware of their situation beforehand.

 

Take the SEQSS set at the +10dB L/T position fed by a signal chain that's -3dB @ 5 Hz (like so many who are now using the new OPPO BDP-105 as a preamp directly into their EQ or amps) and the signal you're feeding the amplifier is virtually dead flat to 3 Hz.

 

Amps do not react to high input single digit algorithmically created content the same way they do to signal above 20 Hz and, of course, neither to subwoofers, regardless of the alignment.

[Kyle]

EP4000 is great for the price, don't they make a 2000 version for 50 bucks less? I can't remmeber

 

clipping can sound pretty bad, bottoming out is like nothing else. Its loud and will make you cringe.

[FOH]

tuxedocivic,

Amplifiers, inexpensive or not, can react differently when driven into clipping. Many envision the typical flat topping of the waveform, or even worse the transient spike artifacts that can occur as well. I'd suspect in the case you reported, due to modest amp clipping scenario, the amp temporarily loses all control of cone motion ... and thus bottoms easily and violently.. I call it dumping.

 

We know an amp's ability to control the cone's motion is Damping Factor (load impedance divided by amplifier output impedance). Since both the VC's impedance, and amp output impedance vary with frequency, so does the damping factor. The amp's design could use distortion lowering global feedback approaches by design. Such techniques increase damping factor, yet when encountering a hard clipping, there's no excess gain remaining to maintain the feedback loop, and the amp can't control the cemf generated by the cone's inertia.

 

I recently posted about this over at The Cult. I believe I've experienced this very phenomena in one during some experiments with my IB. After discovering this "dumping" distortion, I posted about it but got no traction. Then I found both Paul Spencer mentioning it, and John Janowitz describing a similar scenario in a perm club install he performed.

 

Bottom line, who know's what occurred, however it appears an amp's behavior at clipping certainly could cause the dumping scenario I described.   

 

Thanks

[tuxedocivic]

So you think maybe my amp lost control an the cone bottomed. Wouldn't something need to drive the cone to the limit of the suspension? I don't have a good sense of the ins and outs of amplification. But it sounds pretty unanimous that what ever happened is the amps fault. I'll upgrade it as soon as I can and see what kind of improvement I get.

 

BTW, subwoofer trim was set to 0 and MV set to -13db when this happened. I thought I would have been ok. Even though that wasn't calibrated, I figured I was still a ways away from reference levels. But I suppose directing the bass from the other channels into the LFE can increase the subwoofer demand quite a bit.

[FOH]

So you think maybe my amp lost control an the cone bottomed. Wouldn't something need to drive the cone to the limit of the suspension? I don't have a good sense of the ins and outs of amplification. But it sounds pretty unanimous that what ever happened is the amps fault. I'll upgrade it as soon as I can and see what kind of improvement I get.

 

BTW, subwoofer trim was set to 0 and MV set to -13db when this happened. I thought I would have been ok. Even though that wasn't calibrated, I figured I was still a ways away from reference levels. But I suppose directing the bass from the other channels into the LFE can increase the subwoofer demand quite a bit.

 

Who knows what happened precisely at that moment, it's just my best guess. I'm not as well versed in amplification as I'd like to be either.

 

Yeah, an upgrade would sure be a step in the right direction, but an amp upgrade alone doesn't nessesarily assure what I described couldn't happen again. It's a function design, not mere price. Most higher priced amps are accompanied with a more robust operational characteristics, but..you never know. 

 

Hell, any of us here should be operating just this side of clipping. Maybe just tickling the lights, at worst, during the most demanding peaks. I've constructed my system to be just about bullet proof, our physical handling of the energy is the limiting factor. My 12 y.o. son recently asked if some big pulse that came through the system was bad for it. I explained the entire system, top to bottom is, by design, immune from catastrophic overload, etc. My mains are 2kw tri-amped, clean all the way up, my surrounds are active 1kw biamped, clean all the way, the subs; (4)18s, and (4)15s, are all gain structured and balanced to be essentially bullet-proof.  He'll be 13 next month, .. I'm guessing he's quietly looking forward to getting his hands on the remote!   

 

Like Bosso said, it's a shame amps such as those clones aren't fully protected.  

 

Enthusiasts can benefit from the high value offerings like the clones, the Behringers, etc. But working pros wouldn't rely on any amp that would be unpredictable in worst case overload scenarios. At worst, an amp's protection should open up, remove the fault/cool down, etc., and then be good to go none the worse for wear.    

[lilmike]

The thing is, it doesn't matter what your sub can do, the content is there regardless. Knowing the signal roll off is paramount because the signal begins with seriously strong content from 2-120 Hz in a LOT of soundtracks, and it only takes one of them in the right (wrong) situation.

 

...snipped for brevity - but lots of good stuff there...

 

Understood. Thanks for the clarification Bosso.

 

In my case - as I KNOW my sub is bandwidth-limited and I understand what that means when I twist the knob to the right, I have a steep highpass in place.

 

While the preamp may see single digits, the output side does not.  As I stated, I got off the train at 15 Hz. 

[Ricci]

Since we are talking about amps, overloads and damaging woofers...My other TD18 Apollo is thoroughly toasted. (The other is back at AE since it was DOA to begin with.) The other one died at our gig last Sat night. Pushing in on the cone reveals some seriously crunchy scratchy noises. It was getting a 1400w rated channel of a Crest 8002 full range for bass guitar. It made it through about 3 or 4 rehearsals before cooking at the gig. We smelled the adhesive a little at practice but I just assumed it was a new driver getting heated the first couple of times. It is rated as a 1000w driver in regular form and this was the Apollo version which is supposed to have even better heat sinking. Saturday it stunk up the whole stage prior to failing completely at the end of our 3rd song. The Crest acted like nothing had happened and kept on going with the other channel while muting the other. The amplifier was never clipping during any of this so it was not producing full power. The 18n862 driver took the other 50% of the load and has not shown any signs of problems. Its cabinet smells like wood and duratex still. At this point I am not sure whether this bass guitar app is just too much power for the TD18 coils or whether this driver also had some sort of problem in the vc winding from the get go, like the other.

 

Moral of the story here is personally I do like an amp with good protections built in. Otherwise I could easily have had a damaged amp as well on Saturday from it being driven into a shorted load on one channel. This is why I like to stick with tried and true brands that I know get failure tested into all sorts of nasty conditions. I've killed at least 5 drivers that I can remember with the same PS k10 and it acts like nothing happened.

[tuxedocivic]

Crazy Ricci. Sucks to burn up such a nice driver

 

I bought a Crown XLS202 on ebay from a guy close to me (Vancouver). Not a great up but I'm going to start with this running two pairs in series for a 2 x 8ohm load. Then hopefully I'll buy another down the road for a 4 x 4ohm load. I don't need much power cause I don't listen loud. -13db MV was pretty loud for me. We'll see how this pans out. Hopefully the easy 8ohm load will allow the amp to power my subs easily without clipping or being over worked.

[Ricci]

Talked with John some more today and it was almost assuredly a bad coil on that driver as well. He went back through his remaining stock of that particular vc and a lot of them are bad. He showed me some pics and basically towards the bottom there are a couple of turns that are uncoated and bare and shorting out. He is taking care of my drivers...

[tuxedocivic]

Good to hear he's taking care of it. Bad to hear he got a batch of bunk coils.

[FOH]

Ricci, interesting ... that sucks but thanks for sharing.

 

As you said, that's the way a well executed amp design should act; basically immune to whatever is thrown it's way. Yeah, it's a shame he got some bad coils (I immediately think of Kevin Haskins issues), but this may illustrate the difference between a small one man operation like AE, and other build houses that may uncover such failures prior to the drivers leaving the facility, via some type of simple sweeping, or full burn in. But I've really no idea how LF driver mfrs operate in this regard. I don't buy very many drivers, but I do know that the set of four Fi-IB3-18s I purchased, seemed as if they hadn't ever had any voltage swung thru them. The subtle scent during my own burn in was evidence, as was the incredible stiffness, thet really took some time to loosen up. So I've no idea what's the norm with either the small owner/operator businesses, or the big build houses.

 

That's cool you're employing the TDs in your bass rig. Was this just an experiment? I seem to remember John J discussing rave reviews in such bass guitar applications, ... I'm guessing due to the low and linearized inductance. I know as far as mid-bass drivers, these designs do seem to be fantastic. IIRC, the "TD" designation refers to Tom Danley. I don't even recall where I discovered that,..or even if it is true. Anyone? The dual 12" drivers in the Seaton's Catalyst I believe are custom sourced from John also, and in LCRs w/6 total 12s across the front, they certainly offer up as much linear bass/mid-bass as one could want in just about any room. It's a critical area of reproduction that's often somewhat compromised. I've always thought a Catalyst would be fun to be an active bass rig. With some type of DI, and pre-amp w/tonal control/shaping, and BAM ... a 2kw, 3way bass rig !!

 

You mentioned the 18n862, I'm curious what your live playback speaker cabinet is comprised of. Were you using just the two Crest channels each feeding an 18? What type of cab/alignment, and is there other MF/HF drivers? It's quite refreshing knowing there's players with such technical knowledge as yourself, out there gigging, having fun, with an eye on the sound quality.

 

I realize we're a bit OT, but as Tuxedocivic said, "the experts are here". I do enjoy the very high quality contributors here too. Ricci, I don't know but I'm guessing you're utilizing the monstrous GH subs as the bottom end for live shows ...? What comprises the tops and how are they driven? Do you mix from the stage, or do you have a FOH engineer? Do you reinforce your bass playback via the PA in smaller shows? Prior to the TD Apollo burn-down, did you get a subjective feel for the relative differences between the neo BMS, and the TD18?

 

 

Thanks,

I'm no longer doing any more live work, but I am still interested. If my health permitted, I'd be interested in seeing you play out.

 

(there's a casino about an hour away and I've discovered the most fascinating acoustics experiences there. They book cover acts, some national acts, but their stage at a center bar, is basically fully exposed, 360 degrees around. By moving around, the LF lobing between the L&R PA elements is clearly discernable. With a very high ceiling (40' or so), and no walls for hundreds of feet in any direction, the manner in which the subs interact is easy to hear if you know what to listen for. If ever there's a case for co-location of subs,...this is it. The good aspect is without modal issues, the clarity is fantastic ... which attributes why one can so easily hear these other negative effects.

There's large areas of listeners, where the impact is destructively sucked away,.. it's fascinating walking all around the stage area. I've found it's easiest to hear when they've got a DJ w/EDM, but live rock is nearly as easy. Also, you can clearly hear the blending of the subs to the tops quite well too. There's very few live music venues where this is as easy to hear as it is at this place. Also, with no boundary reinforcement, the space is brutally tough to fill with energy. I've discussed this with them, but it falls on deaf ears. Occasionally a bigger PA is brought in (New Years, etc), but the same lobing was still there. Last I checked, the house PA is a single, powered JBL VRX18" per side, combined with a powered PRX top, per side.)

 

Sorry, don't get out much

[tuxedocivic]

Hooked up the xls 202 I got off eBay and things are a lot better although I haven't hammered on it with ULF yet. I've got it wired 8ohms. I hate the low input sensitivity, but I knew what I was getting into buying a pro amp.