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Advice needed....which to replace, my Stewart World 2.1 or my Acme Low B4II ???

Discussion in 'Amps and Cabs [BG]' started by jetsetvet, Jul 13, 2005.

  1. jetsetvet

    jetsetvet Banned

    Mar 24, 2005
    :help: I am hoping that one or more of you can offer a reasoned opinion on my gear dilemma. My rig is: Furman PL-8 power conditioner -- SansAmp RBI preamp > Rane PE17 parametric EQ > Rane DC24 gate/expander/dual band compressor/limiter > Stewart World 2.1 amp > Acme Low B4II cab.

    As hard as it is for me to believe, I am having my amp shut down due to clipping when I pop a string, or more commonly when I am playing hard and a string makes contact with a pole piece on my pickup. And even when I have compression and peak-stop limiting, as well as high and low pass filters at 40 Hz and 10 KHz, these peaks are enough to cause the Stewart's protection circuitry to shut the amp off (for about 30 seconds or so). Musicus interruptus is a serious bummer. And when this occurs I am playing loud, but not as loud as one might think, considering all the power I am pushing.

    I have spoken with Andy Lewis at Acme, as well as tech guys at Stewart and Rane each, on several occasions regarding this problem. All of these people have been very helpful and have been very generous with their time....yet, as might be expected, each claims ultimately that their particular component is not the root of my trouble, and that I need to replace a component other than the one they represent. The conclusion I have drawn from these conversations and emails is that all of the components of my system are working to spec and performing as they should. Hence, I conclude that I have an incompatibility between my amp and cab, and one of these two needs to be changed.

    I play in a loud garage rock trio, mostly doing raucous covers of Stooges, MC5, Flamin' Ghoulies, Vaselines, etc. When I am playing in this group it is typical for the -20dB lights on the front of my amp (bridged to mono) to light up much of the time, at least on every thump of my E or A strings. The 0dB lights come on every now and then as well, but if a string hits a pole piece, the clip lights come on for that brief moment and the amp shuts down about half of the time that this occurs. Sometimes the right channel shuts down, sometimes the left, and sometimes both....and because of this the reps at Stewart said that it is highly unlikely that there is a problem with the sensitivity of the protection shut-down, because if there were, then I would observe only one of the channels repeatedly shutting down. The liklihood that a problem would arise simultaneously in both channels (which in a Stewart amp are completely discrete) of the amp is statistically very remote. The truth is that while playing :bassist: , up until the point that my amp shuts down, I absolutely love the tone I get out of my cabinet......the low bass is huge and thick, but tight at the same time, with smooth mids and highs too.

    So, it seems as though I need to go with either a bigger amp or a more power efficient cabinet. The trouble is that I really like the sound of both of these parts of my rig. I used to use a QSC PLX 2402 in this rig, which did occasionally clip but never shut down, but it did not sound nearly as good (less bass, shrill highs) as the Stewart. So while I could get a more powerful QSC, I really don't want to go with that option. I called Crest Audio and spoke with a rep there that recommended a CA12 amp to alleviate my trouble (and I know a guy that uses a CA9 in his bass rig that sounds very good), but a CA12 weighs in at 67 lbs and takes up three rack spaces. Considering that my Stewart is 17 lbs and two rack spaces, that sort of a change seems less than thrilling, but I am considering it. To the great credit of the rep at Crest, he said that the new CC line and the top-o-the-line Pro200 line of Crest amps are not as well suited to a bass rig as the CA line (which is a less expensive line of amps). He even said that I should consider just selling my rack and getting an Ampeg SVT!

    So which do I dump? :confused: And whether it is the amp or the cab that you think I should replace, what is your opinion on what I should replace it with? I must say that it sure seems ridiculous to me that I need more than 1800 watts RMS/2100 watts peak, to have the headroom to play in a loud three piece garage band.

    Amps to consider: Crest CA12, Crown?
    Cabs to consider: Schroeder, Accugroove (too f'n overpriced for me really), EA (also too $$$), Avatar, Dr.Bass, Low Down Sound, Ampeg, Eden, Bag End etc?

    If I replace the Acme cab, is there any cab that can match that deep low end AND be efficient enough to require less power at a given volume? Would I be correct to think that my Acme is really not capable of delivering the loud rock-n-roll volume I am seeking, regardless of how big and amp I drive it with? I want the tone of my Acme at twice the volume! If I can't always get what I want, then tell me how to try sometime to get what I need!

    Thanks in advance to any who may have a comment.

  2. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    Hi Curt,

    Is the Stewart running hot when it shuts down? If so, maybe moving some air through it will help.

    Unless the Stewart has EQ boosting the bass, it and the PLX would actually have the same amount of bass and highs (because both have very flat frequency response, as power amps tend to), unless you EQ the signal going into the amps differently.

    Continuing on the suggestion above, if your rack has rear rails, I would try putting a rack-mount fan behind the Stewart.
  3. jetsetvet

    jetsetvet Banned

    Mar 24, 2005
    Thanks for your comments. There is no overheating going on...the top of the amp barely even gets warm. This shutdown is definitely due to the super fast trasient peaks. I do not understand why the Rane DC24 does not clamp down on these completely but it does not (it is seeming that these transient peaks come through so fast that the limiter doesn't even kick in until they have already passed through. And I know it does not fully clamp down on them because as an experiment, I placed the gate/compressor/limiter that I used to use (before acquiring the Rane), a dbx 166XL, in line AFTER the Rane DC24 and set the dbx compressor as a limiter (ratio at infinity, attack and release as fast as possible). Even after both limiting threshold lights (one for each of two bands) on the Rane would solidly light up, I could still achieve another 10 to 16 of gain reduction lighting up the dbx if I slapped a note on the E string hard . If the Rane was truly clamping the signal below a ceiling, then the dbx should not show any more gain reduction when it sees this already limited signal. The Rane compression sounds better than that provided by the dbx (due to the dual band compression) but with respect to peak limiting, it is a disappointment. If it did what it claims to, I don't belive that I would need to replace anything in my system!

    As far as my comments on preferring the sound of the Stewart over the QSC, I must say that the differences were small between the two, and that they both sound very good. I just felt that the low end was slightly better through the Stewart on my particular system. As far as the QSC highs being "shrill"....I probably made an overstatement. Better I should say that...in my rig with all other variables the same, the QSC had sharper highs than the Stewart......but this is nothing that could not be made equivalent with a slight adjustment of the treble control on the preamp (or on the parametric EQ that I run as well). I replaced the QSC PLX2402 not out of dissatisfaction, but because I found a terrific deal on the Stewart used, and slightly preferred its sound. If I could turn back time in retrospect, I would have not switched to the Stewart......but this problem, and its causes did not become apparent to me until I had sold the QSC. It seems as though the protection circuit on my Stewart is working as it should to protect my speaker when the amp clips hard. Truth be told, I don't know what type of amp to use to drive my Acme LOUD. I'm thinking that the kind of LOUD I am looking to get, just cannot be had with an Acme no matter how much clean power is provided.

    Part of me wants to just get rid of this whole rig and get a head made specifically for amplifying electric bass. It's kind of like owning a Ferrari that drives really great but breaks down every time it hits 70 mph. I think I need to get rid of my Ferrari and get a Saab.......you know? :cool:

  4. Eric Moesle

    Eric Moesle

    Sep 21, 2001
    Columbus OH
    Personally, I'd remove one item from the rack at a time, and see which is the offender. Perhaps avoid using the limiter one night, avoid the parametric one night, borrow a power amp for one night, borrow a pre for one night. The loser will show himself eventually . . . .
  5. You could always get a second Acme. And a second power amp. That would give you the same tone, but louder, if that's want you want.
  6. KJung

    KJung Supporting Member

    I'm going to take the other side of this.... as a former Acme owner who liked the sound but was not so enamored with the low efficiency... there are a ton of cabs out there that would just sing with the Stewart.... from Accugroove which would (IMO) keep some of that 'flat' Acme vibe, to EpifaniUL to Bergantino, etc.

    The Acme line is great, but I always found the 210's I had to be a little overpowering on the low end and somewhat underperforming in the upper mids and treble (I know, I know... they are flat, learn to adjust the EQ... but it's more than that). I only played out of an Acme 410 once, but from what I remember, it had the same single mid driver (that tiny little 5" or whatever it is, and that single small tweeter... it was very mushy IMO).

    Anyway... I'm not bagging on the Acme stuff... I used the LowBII's for quite a while... but if you are having trouble pushing that 410... just take your rig as it stands and plug it into a Bergie or an Epifani... I think you would be shocked at the volume and punch. I remember playing out of the Acme210 in my rehearsal space and then, just for the heck of it, plugged my amp (a WW Ultra 1200 watts) into my old BagEnd S15D-X and it was about 5 times as loud on the same volume setting of the amp (same ohmage, etc.) That was a revelation to me!
  7. LeonD

    LeonD Supporting Member

    How is your EQ set? Sometimes a boosted EQ will take a lot more power to drive.

    Also in one of the ACME posts on this board, someone said that they cut the lows (50 hz) a bit. It tightened up the sound and made it louder.

  8. popinfresh


    Dec 23, 2004
    Melbourne, Aus
    Ok, I didn't read all of that, as I have to go.. But I saw you mention that sometimes only the right or left sides shut down, correct? So your running this rig stereo?

    Have you tried running it mono?

    Sorry if I missed something..

    BTW: I know someone using two LowB2's and it's been powered by a QSC 1 space power amp of some description.. From memory, it puts 800 watts into each cab (someone will know the model).
    Anyway, that rig is LOUD.. I mean, I was standing in the crowd and he did a solo, on the lower strings my throat and even body was just vibrating. Whilst there was PA, you could hear his rig easily.
    I really think you should have though watts to push it..
  9. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    I don't think you'll gain anything from throwing extra power at the system. The 50Hz highpass filter on the PLX amps does a great job of increasing the maximum volume you can get from Acmes, whilst also removing the sub-lows that don't translate well in the mix. I hit my pair of Low-B2s with 900W each and they go loud and my PLX 3002 has never stopped working, even when riding the limiters.

    Lowering your pickups so the strings don't hit the polepieces may actually solve the problem (I'm guessing that when you pop a string that the same is happening, though it's disguised by the pop). Or getting pickups with covered polepieces like Barts or EMGs.

    An Accugroove El Whappo or Whappo Jr would also solve the problem, but it'll cost you! I'd definitely look earlier in the signal chain, to how you're playing, how your bass is set up and what bass you're playing.

  10. Fuzzbass

    Fuzzbass P5 with overdrive Gold Supporting Member

    Excellent point. Strings hitting the polepieces is just nasty... nothing good can come from that, it's bad news.
  11. Lonnybass

    Lonnybass Supporting Member

    Jul 19, 2000
    San Diego
    Endorsing Artist: Pedulla Basses

    You and I are running rigs that are very similar - I'm using an Alembic F-1X (and a bunch of other rack stuff) into a Stewart 2.1 into a pair of 4 ohm Acme B2's in stereo mode. While I would never push the power amp levels past about one o'clock, there have been a few times when the amp has shut down. My mistake? I was plugging the Stewart into my Furman with the rest of the gear instead of directly into an electrical outlet. According to the Stewart techs, this is a commonly made (and very big) mistake that people have made. Solved my problem right away and started getting more figurative bang for the buck.

  12. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    That's a really good point.

    I was looking at it from the angle of it's shutting down for ~30 seconds, it's probably overheating and then resetting when it cools down enough. I forgot that many of the Stewart models take about that amount of time for the power supply to turn on (I rented a small PA system once some years ago to provide sound for a meeting my wife was helping to run, and I almost dropped a nut when the Stewart power amp seemed to be dead when I turned it on--as I was poking around in the back of the rack to see what was wrong, it started up and worked fine; whew!). Thus, if for some reason a peak in current draw caused the AC voltage to drop enough to shut down the power supply, then it would be just like shutting off the AC power and then turning it back on again. In this case, removing any extraneous AC-handling gear could help in finding out if something was acting as an AC bottleneck.

    I always figure, if you can potentially solve a problem for little or no money or time, it's worth exploring before you try the expensive or time-consuming solutions. ;) That's gotten me a bit of heat sometimes from salesmen, but that's okay.
  13. I'm thinking this is part of it too.

    Most fields (mag, gravity, etc) in nature vary by the square fo the distance to the object. Having the pickups too close to where the strings are hitting sometimes could cause crazy huge transients. Keeping them farther away could reduce those.

    going from 1mm to 2mm away from pickups as the string moves is big difference. The same 1mm difference is much smaller proportionally when its varying between 9mm to 10mm. Just an example to illustrate... you get the point though...

    That and bypassing the Furman for the power amp are easy and inexpensive to try. ALWAYS try the cheap, easy things first before trying expensive difficult things when troubleshooting.

  14. Lonnybass

    Lonnybass Supporting Member

    Jul 19, 2000
    San Diego
    Endorsing Artist: Pedulla Basses
    Bob's description of the delay when starting up his Stewart is something built in to those amps. I had a few scary start-up delays myself! Essentially, the amps are building up full power during startup time since they lack internal transformers. Put the Stewart into the Furman, and all of a sudden, you're instantly limiting the amount of power going into the amp...meaning it might not work at full power and could be tripped if pushed too hard. It's taken me a while to figure out, and seems to go against instinct in not plugging a rack unit like that into a power distributor.

  15. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    They do have transformers, but they operate at a high frequency instead of the AC line frequency of 50 or 60 Hz.
  16. jetsetvet

    jetsetvet Banned

    Mar 24, 2005
    To all of you who have responded. I thank you! The TB community is remarkable and the passion we bass players share is very cool.

    Despite all the great recommendations and thoughts on what might be a fixable problem, I have already explored most of that over the past few months in talking several times with technical representatives at Rane, Stewart, and Acme.

    Stewart reps told me to not plug my amp into my Furman, but to go directly into a grounded 15amp (or more) 120V AC circuit. Making this change did nothing to change the shut down problem in any perceivable way.

    As far as lowering my pickups goes, it certainly is a sensible thing to do, in concept. There are a couple of other issues here though. I probably play too hard much of the time, from a schooled bass player's POV. If you have ever seen Mike Watt play, I would suppose that I play with the same sort of attitude and approach, albeit with only a fraction of the talent. (One time when Watt was asked for advice on how to approach playing the bass he said, "just grab the neck and strangle it!"....I like that philosphy a lot!) The truth is that I am not sure that lowering the PU's would solve this problem, because sometimes I go nuts (while playing) and beat on my basses pretty hard. Even if lowering them prevented the string-pole contact 9 out of 10 times from the way it is happening now, it could and would still occasionally happen, and hence, especially when gigging, it would still be an unacceptable potential point for failure. The other problem is that I play a few different basses, of which the favorite is my Travis Bean, which is one of the basses this contact problem happens with quite easily.....and it has pickups that cannot be adjusted for height at all....they are bolted hard to the aluminum through-neck.

    e82cb23a. 8dad9f0a.

    I also experiece the string-pole contact with others....Fender Jazz, Yamaha BB3000S, and a G&L L2000E. And I must say that I get the amp shutting down from hard peaks that do not involve string-pole contact......like if I slap the E string, especially if I am fretting it somewhere up the neck.

    Likewise, some of the very good comments made regarding the advantages of frequency pass filters and limiters are issues that I think I have adequately dealt with in my system with the Rane PE17 low and high pass filters set at about 40Hz and 10K Hz, and the Rane DC24 with its dual-band peak limiters. It seems however that when these peaks come through the Rane DC24 that they are such instantaneous transient peaks that they sneak by the limiter before it has a chance to clamp down (and there are no adjustable attack and release times on this unit). In this respect, the limiting on the Rane has been a dissapointment, because it reacts too slow, and simply does not do the job it is supposed to do. If the Rane really clamped down such that absolutely no signal of any kind and at any speed of attack could possibly go above the set threshold, then I would not have felt the need to start this thread, because my amp would be completely protected from what is shutting it down now.

    Overall, I think I just need more headroom. The fact that the -20dB lights on the Stewart are on more than half of the time I play (that is to say, they go on and off, but are on more of the time than off), suggests to me that I am not that far from clipping the amp when I am just playing at my typical loudness and intensity of attack. Then, (usually at the crescendo of the last chorus) when I play harder, I go into clipping fairly easy. And hence, I maintain that since each component is functioning as it is designed to do, in order for me to get the headroom I require.....I need to either get a more powerful amp or a more efficient cabinet. And, as much as I love the sound of my Acme B4, I am inclined to think that it is the part to replace. For no scientific reason at all it just seems to me that a 4x10 cab that needs more than 2000 watts just to play loud without the amp clipping is a problem in an of itself, no matter how good it sounds. In other words, I feel that replacing a 2000 watt amp with something even bigger, just to play using one 4x10 cab in a little garage rock band, is bordering on complete absurdity. :meh: Isn't it? :confused:

    So, what kind of cab (or amp) to get? Again, I sincerely thank you all for your valuable advice. :hyper:

  17. Not to hijack the thread, but Bob could it be possible to damage an amp by keeping it plugged into a Furman? The reason I ask is because I just had my 2402 repaired because of blown transistors. I had it plugged into my Furman in my rack.
  18. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    No, that won't cause damage.
  19. Ostinato

    Ostinato Guest

    Feb 7, 2005
    Toronto ON
    Dump that DC24 man. Rane tried marketing those as a do-all compressor limiter, but they're way too much technology for a guitar or bass rig, I should know... I had one for three years and couldn't get any decent mild compression out of it. Those are broadcast-quality units for serious pros.
  20. LJW


    Feb 8, 2002
    northeastern pa.

    Perhaps add another B4?