Small rig (*ahem) advice

Discussion in 'Amps and Cabs [BG]' started by Stephen Russell, Aug 9, 2022.

  1. small Class D heads are more affordable than ever, why guess if the other amp head is going to fry the speaker?
     
  2. I'd add the crossover may fail as well, although how likely that is I don't know.

    Most players, or most players that need to have a cab repaired?
    That is a very important distinction, and a potentially very different group of people. The squeaky wheel gets the oil and all that.
     
    Baloo Pasquariello likes this.
  3. Undoubtedly not a bad thing to note, but I can't help but think that in good part, that's because most people have never actually damaged a speaker from simply putting too much power into it. I certainly haven't, so that leaves me free to personally judge others that, assuming less than 300 watts is "safe", damaging a speaker rated for handling 300 watts with an amp with a power output rating of 350 watts as making a bonehead move :p

    Bear with me and I admit that at my level of technical understanding, all facts may not line up with my reasoning, but as I understand it, in this case, "350 watts" is running continuous (for an RMS number) at flat-out approximate maximum, right?

    If that's correct, then changes in loudness from the speaker correspond to changes in the wattage output of the amp. Shouldn't it then be the case that if running that amp at its maximum capacity for loudness from the speaker is at 350 watts, then half of its capacity for loudness would mean 35 watts going into the speaker (i.e., 10 times the power with the same amp and speaker results in a 10 dB of SPL increase, which is twice as loud)?

    Because of that logarithmic relationship, power increases from 50% to 100% loudness (i.e., twice as loud) in 1 dB increments look roughly like this ...

    If 90 dB at 20 feet comes from 35 watts from a given amp/speaker
    +1 dB = 44 watts
    +2 dB = 55 watts
    +3 db = 70 watts
    +4 dB = 88 watts
    +5 dB = 111 watts
    +6 db = 139 watts
    +7 dB = 175 watts
    +8 dB = 221 watts
    +9 db = 280 watts
    +10 dB = 350 watts

    It seems that it's a question (that doesn't have a precise answer) of, "How many watts are going into the speaker in your real world scenarios?" I don't believe I'm so different from most people in that I only ever use some part of my amp's capacity for loudness without ever knowing precisely what fraction that is...but I'm pretty sure it's never 100%. Here, where the amp's maximum output would be unsafe, what would feel like ~75% would probably be somewhere just above 100 watts. 300 watts (ostensibly "safe") would probably be something like 95%.

    Personally, I turn my amp up to a level that's sufficient and appropriate for the situation not to try to use all of my watts. IMO, if a situation generically makes a 300 watt 112 cab sufficient, it seems that an amount of power a good bit less than the cab's handling limit is probably going to be sufficient, and that would be the case whether you're using a 250 watt amp or a 500 watt amp. For the non-boneheaded, they both have volume controls to reach the same level.

    Most really, it would be nice if amps had a wattage output display.
     
  4. H K

    H K Supporting Member

    Jun 18, 2021
    Norway
    Get an old Peavey mini rig. They did a 212 w/ 250w head IIRC
     
  5. Wasnex

    Wasnex

    Dec 25, 2011

    If your cab can safely play significantly louder than you require, you are relatively safe running an amp with more power than the cab can take. Accidents can still happen. The more the available wattage exceeds the cab's power rating, the more likely an accident can take out a driver.

    Unfortunately, IMHO, it's not hard to imagine a situation where a 112 simply can't play loud enough. How are you to know when you have exceeded the cab's power limits? There is no guarantee you will ever hear the cab complain before it fails. When the cab is not capable of playing loud enough, using an amp that can produce way more power than the cab can take is a pretty good recipe for disaster.

    I believe I am usually satisfied with a rig that can produce at least 124dB. So a Mesa Subway 112 or GK NEO 112 IV should (barely) meet my minimum needs. Both are rated to produce about 124dB.

    IMHO it would be a lot better to run a pair, as that would bump up the max SPL to about 130dB. Then, playing a pair at 124 dB would give each cab 6dB of headroom: If 130dB requires 800W (400W per cab), then 127dB is 400W total (200W per cab), and 124dB is 200W total (100W per cab).

    It's a lot safer to run a 400W cab at 100W, than to push it to 400W. As you mentioned, you really have no idea when you push the amp to 400W. Even worse, the mechanical power limit of many cabs is actually less than their RMS power rating. So if you like heavy lows, you may destroy the cab with only 300W (or maybe less).

    Many of us are overly focused on how much power the amp can make. The real focus needs to be on how loud the rig can safely play, and whether the resulting SPL meets our minimum requirements. Even better if the rig can exceed our SPL needs by a fair margin.
     
    Rip Van Dan likes this.
  6. Rip Van Dan

    Rip Van Dan DNA Endorsing Artist Supporting Member

    Feb 2, 2009
    Duvall, WA
    I found some conflicting info on the amp. Some said it was 750-watts but didn't specify that was an rms rating. Then I did find a listing from AMS that gave a little more detailed info. However it said the 750 was 700-watts into 4Ω and 350-watts RMS at 8Ω. No big deal about the 50-watts difference really and if it really is [email protected]Ω and [email protected]Ω that's actually better for you - closer to the max for your 112 cab.

    As long as you're running a clean sound and don't get carried away turning the master up, AND the Hartke cab is 8Ω you should be fine with this. You will need to listen carefully for any farting sounds if you get real loud because that tells you that you are on the edge of blowing that speaker. Do not finish the song without adjusting it. First thing to try is to drop the Bass EQ some and if that doesn't do it, you must drop the master.

    I have a couple of Eden EX-112 cabs. They'll handle 300-watts rms and when using both I have to plug them into my dual powerblock Eden WT500/800 amp because both cabs are 4Ω cabs. So I plug one into each channel even though the amp I used them could put out 100-watts more than they can handle. I used for my medium-sized venues for about a year and never got close to overpowering or stressing them. They were more than loud enough for medium venues with my master running between 9 o'clock and 10 o'clock depending upon the room.

    I do run a very clean and clear sound though, so I would hope to hear them being stressed in time to fix it. However, if you run distortion on your signal or even overdrive, the ability to hear if the speakers are being pushed to hard virtually disappears. In my case the cabs were more than loud enough for the gig long before they had a chance to get stressed. So if you are judicious about it and conscious of the fact you can blow them if you turn them way up, I think you'll do fine.

    Below is my "small venue" set up. It has an Eden TN226 (226-watts rms) class D amp to drive it and goes into an Eden EX-112 cab. It's a sweet sounding set up but I should have bought the 500-watt version (TN-501) and bought the 8Ω cabs. Then I could have used both of my 112's with a 500-watt amp that weighs 5.3-lbs. Bought the amp used at a decent price and the cabs were just $269 each new (has Neo speaker) and weigh 31-lbs.. Got a LOT of compliments on my sound with it.

    TN226PlusEX112_600x846.jpg
     
  7. Rip Van Dan

    Rip Van Dan DNA Endorsing Artist Supporting Member

    Feb 2, 2009
    Duvall, WA
    One other thing to add to Wasnex's great info. Two 112's always sound fuller than a single 112 even if the SPL is the same - playing at low levels. Has to do with a boost to bottom end when two cabs are stacked together that a single speaker cab just doesn't have. If you have one 112 that sounds good, adding a second not only gets you a higher SPL, it sounds better too.
     
    Ric Vice and Wasnex like this.
  8. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    The power ratings on most speaker are thermal ratings, yest on bass speakers the vast majority of failures are from exceeding the speaker's mechanical capabilities. VERY few manufacturers publish mechanical power handling ratings because they typically fall between 50 and 100% of the thermal ratings and don't look as good to the marketing departments. Therefore, in spite of player being confident that they can hear a speaker being stressed, in fact in testing that I have done under controlled conditions (ie. no drums and cymbals, guitars, O/D or distortion pedals), roughly 1/2 couldn't hear the speaker as it was being driven well beyond Xmax. Then, adding the band tracks and/or pedals, the number fell to around 10-15%. In a band situation, I have a tough time as well, even knowing exactly what I am listening to.

    And for the folks who claim that Xlim is the point where damage occurs, actually there is an exponential line between Xmax and Xlim that relates lifespan to how close to Xlim. For example, a speaker may last 50,000 hours at 1/4 rated mechanical power 20,000 hours at 1/2 rated mechanical power, 5000 hours at Xmax (rated mechanical power) and a few hours to a few minutes at Xlim. Xmax and Xlim are part of the mechanical power handling, which is a function of the driver, the cabinet and the HPF being used within the amp.

    Since the rated mechanical power is almost always less that the rated thermal power, you should be able to see why it's easy to unintentionally overpower a speaker.
     
  9. Kaa

    Kaa

    Sep 28, 2004
    Cleveland, Ohio
    That's a lot o' treble.
     
  10. Kaa

    Kaa

    Sep 28, 2004
    Cleveland, Ohio
    So, for a general "rule of thumb", should one keep to the 50% of thermal watt handling when looking for a cab/speaker to be on the safe side?
     
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Depends on the robustness of the cabinet design.

    Claims vary by manufacturer, and then there are some manufacturers that double to quadruple the thermal rating by using “program” or “peak” power ratings.

    For example, a 2000 watt 210 is not going to be using RMS metrics, nor mechanical power handling, but some combination of thermal and program or peak power.

    This is a pet peeve of mine, because when a player is lead to believe something is true based on published and then damages their cabinet, it’s not “really” their fault.
     
    Tendril likes this.
  12. Baloo Pasquariello

    Baloo Pasquariello Supporting Member

    Jan 23, 2015
    Battle Ground WA
    Ha, yeah, I took the pic when I was testing the range of the controls with some new flatwounds!
     
    Tendril likes this.
  13. Wasnex

    Wasnex

    Dec 25, 2011

    The RMS rating is how much energy the voice coil can handle long term without overheating. Think of it as sort of a long-term average.

    Let's a assume a driver with this rating: 200W RMS, 400W Program, 800W Peak. The means that thermally the driver can handle short bursts of power up to 400W RMS. Long term the power must remain at or below 200W or the voice coil will overheat.

    The confusing part is the 800W Peak is actually the same power level as 400W Program.
    upload_2022-8-11_14-57-5.png
    In the image assume the top line is 800W Peak and the red line is 400W RMS (Program). So the waveform is exactly the same for both readings, and the only difference is how the waveform is measured.

    To convert Peak volts to RMS volts:
    upload_2022-8-11_15-37-0.png
    In other words, 1Vp = 0.707V RMS.

    So thermally our driver can handle 200W RMS long term with short bursts up to 400W RMS. That does not mean it can handle 400W RMS of bass.

    With bass cabs you also need to be concerned about the mechanical power handling below 100hz. The amount a driver moves when power is applied is related to the tuning of the cab. Assuming a common driver, the mechanical power handling will vary from one cab design to the next. Often the mechanical power handling is significantly less than the RMS rating.

    Examples:
    From a thermal perspective, the Eminence 3015 is rated for 450W RMS 900W Program. As I mentioned earlier mechanical power handling will vary by cab design.

    The typical excursion plot in a ported design has sort of an S-shape--see charts below:
    upload_2022-8-11_15-39-33.png
    Notice the trace turns from black to gray when excursion hits Xmax (5.9mm)

    This one takes more power, but it does not play as low.
    upload_2022-8-11_15-42-34.png

    So mechanically the large design must be limited significantly below the drivers RMS rating. While the medium design can handle the full RMS rating within its pass band, it requires a 40hz HPF to protect the driver from over excursion.
     
    Kaa and agedhorse like this.
  14. dbsfgyd1

    dbsfgyd1

    Jun 11, 2012
    Mascoutah, IL
    Yeah. I hear ya. My D-210-XST is about 48lbs. I had a not convenient load in this last weekend at an old theater. To load in was just a 70’ mini “alley” to the stage door, to manually haul your gear from the street. If you couldn’t get a parking space in front of the theater (the sound company had this occupied), add another 60 feet to cross the street. The “alley” was basically an uneven foot path from broken and shifted concrete and not suitable for dollys. Once you got inside it was another 60’ across the stage. And the stage was 6’ about the theater floor. And at age 69, I got it in and out of there no sweat.

    The upshot was, the the vocals monitors were so loud, and the room had a very excitable 300hz ring, I ended up playing through in ears. LOL!!!
     
    SJan3 likes this.
  15. SJan3

    SJan3 Supporting Member

    Dec 8, 2010
    Ct.
    All that schlepping for nothing?? DANG!
    And those 210XST cabs are listed at 59 lbs.
    You're working harder than you know!!
     
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  16. dbsfgyd1

    dbsfgyd1

    Jun 11, 2012
    Mascoutah, IL
    Maybe. The XLTs are heavier, due to the second port. If I’m not mistaken, they are the ones that are around 60 pounds.

    But since you mentioned it, I’ll dig out my owner’s manual. I’m too tired to lift it on a scale!!!..LOL!!!

    The amazing thing about these cabs is once you get them off the ground, with the way they balance with the top of the cab flat against the waist, they are no problem moving with them. If you try to stoop over them with the back of the cab against your body, all bets are off. It was designed to be a schlepped around, but with proper posture.

    Seriously, I’ve been lugging these for the last 10 years, and I’m no Charles Atlas either. That said, at almost 70 years old, I know I’m not going to hauling them around forever. And soon there will be a time when I can’t. In the meanwhile, it’s good exercise.
     
    SJan3 likes this.
  17. SJan3

    SJan3 Supporting Member

    Dec 8, 2010
    Ct.
    Yes, the XLTs we're heavier yours. My problem is I have arthritis in my back. Lifting that weight in my condition is an exercise in torture. I need lightweight and even so I have to squat carefully and lift slowly.
    Now I use MarkBass cabinets. So much easier to move, especially at the end of the gig. Getting older has it's blessings in the way of wisdom but, for me, physical challenges as well. I go for spinal injections Tuesday. 2nd round..