Yet another powered stage speaker thread

[Tusker]

8 minutes ago, Reezekeys said:

 

You can't switch it to mic level input and back off on the gain, like on my K8s? 

That’s the feature on my k8/k12s I was referring to. I talked to tech support at QSC. Basically they said “don’t do it but you can’t hurt our speaker doing it.” So I did it. Didn’t hurt the speaker. 

[Reezekeys]

I'm guessing they advised against it only because some folks without the smarts to understand gain staging could make a connection and, with the gain at max, blow their ears out! When I knew I had to use the switch at "mic" I made sure to turn the gain down before connecting anything. IMO it's absolutely fine to do this, with the K or any other speaker, as long as you're careful like this.

 

FWIW I haven't used the switch at "mic" for many years. With the switch on "line", my laptop or iPad can drive the Ks to a very respectable level, certainly loud enough for any gig I do these days.

[HSS]

1 hour ago, Tusker said:

That’s the feature on my k8/k12s I was referring to. I talked to tech support at QSC. Basically they said “don’t do it but you can’t hurt our speaker doing it.” So I did it. Didn’t hurt the speaker. 

Same here.  I've switched to" mic" gain on my QSC K12, Yamaha DBR10, and on my JBL 515xt's and never a had problem. I just make sure I've dialed the gain all the way down and then ease it up gently a little bit.  I suspect it's no problem on about any powered speaker that has the line/mic switch, assuming one is not an idiot and dials the gain knob way down before doing it. 

 

Having said this, I've only switched to "mic" gain no more than a few times on each of my powered speakers when I don't have the time or I'm too lazy to hook up a mixer for the extra gain.   I do wonder if the output is a little noisier using mic gain but in a loud band in a noisy low-brow bar setting I usually play in, it's probably not discernable anyway.  

[CEB]

No such switch on the EVs.  You would have to use the XLR Mic input.  

[drand48a]

Plugging a line output into the mic input would definitely be a bad idea.  I'd bet that mic input is lo-Z, which is not good for line outputs.  The QSC's probably have 10K or 20K ohm inputs, and "mic" mode is just more gain.  That's not ideal for mikes, but would work.

 

I would expect to not get enough level out of the ZXA1's if plugging a -10dBV line output into it (assuming they're +4DBu) -- you lose about 12 dB and there's only 6dB of gain.  I would not expect to have any problems when plugging a +4 dBu line output into it.  If there is an issue there, then it's just not designed properly, or it's not rated properly.

 

IIRC, the Electro is a -10dBV output.  But the CP4 has +4dBu outputs (based on what I've noticed; it's unfortunately not in the specs.)  The aux input on the CP4 is clearly a -10dBV input, which is a good thing for my purposes.

[Reezekeys]

On 11/29/2022 at 5:15 PM, drand48a said:

The QSC's probably have 10K or 20K ohm inputs, and "mic" mode is just more gain.  That's not ideal for mikes, but would work.

 

I am by no means a electronics expert but while my K8s' mic mode does seem to be "just more gain", they claim different impedances for each input setting.

 

Below is the schematic of my original K. The mic/line switch seems to only switch a 20K resistor in & out of the input path. That's a simple pad, no?

 

 

On the QSC website I see these specs for the original Ks:

 

"XLR / 1⁄4": 40k balanced / 20k unbalanced • XLR / 1⁄4" MIC mode: 2260 balanced • RCA: 10k"

 

So, switching to "mic" does more than "just more gain." Looks like when I needed that eardrum-destroying volume I was feeding my speakers from the headphone output of my MacBook Pro into a 2260 ohms input. Is this bad? All I know is that it worked fine, and sounded fine - and I did this for years (unfortunately, for my ears).

 

I'm pretty sure the warnings to not use mic-level settings on PPAs with line-level sources is based only on the assumption that the user is gonna forget to turn the input gain down before hooking up!

[jazzpiano88]

10 hours ago, Reezekeys said:

 

I am by no means a electronics expert but while my K8s' mic mode does seem to be "just more gain", they claim different impedances for each input setting.

 

Below is the schematic of my original K. The mic/line switch seems to only switch a 20K resistor in & out of the input path. That's a simple pad, no?

 

 

You could look at it that way.   In terms of impedance, however, you want to match the source impedance (instrument or mic) with the amplifier input impedance, hence the switching of the input resistor for each case (hi and lo Z).

[Reezekeys]

12 hours ago, JazzPiano88 said:

You could look at it that way.   In terms of impedance, however, you want to match the source impedance (instrument or mic) with the amplifier input impedance, hence the switching of the input resistor for each case (hi and lo Z).

 

I thought the resistor was primarily to reduce the higher line-level signal so as not to overload the input stage - it's a pad, for level-matching, not specifically "impedance-matching." It make sense that at the "mic" setting, the 20K resistor is bypassed so there's 20K less resistance presented at the input - that seems to account for the difference in impedance specs between the two settings (20K vs 2260 ohms).

 

I'm gonna derail this thread a little bit further then get outa here. It turns out my MacBook Pro's headphone output has a pretty low impedance: <24 ohms. From an Apple Support page, these are the specs for the older MBPs:

 

During playback of a 1 kHz, full-scale sine wave (44.1 kHz output sample rate, 24-bit sample depth, 100 kΩ load, unless otherwise specified) the audio line output has the following nominal specifications:

Jack type: 3.5 mm stereo Maximum output voltage: 2 VRMS (+8.24 dBu) Output impedance: < 24 Ω Frequency response: 20 Hz to 20 kHz, +0.5 dB/-3 dB Signal-to-noise ratio (SNR): > 90 dB Total harmonic distortion + noise (THD+N): < -80 dB (0.01%) Channel separation: > 75 dB

 

Obviously my K8's inputs - both line and mic - present less than the 100K load Apple cites in their specs. So what are the implications of this? I have no idea! I can only relate real world experience and say without hesitation that plugging the headphone output from either my MacBook Pro or iPad directly into my QSC K8s (or now, my Alto TX308s) sounds absolutely fine, with more than enough undistorted gain I need to play any gig. This is my experience from when I started using a laptop on gigs twenty one years ago (can't believe I actually typed that!) and cabled it directly to Mackie SRM450s. It worked fine then and works fine now, at any input setting, as long as you observe proper gain staging.

[Reezekeys]

I've been reading a bit further on the subject of impedance. You don't necessarily need or want to match impedances between output and input. In short, a low impedance output feeding a higher impedance input is OK. I've read that the ideal ratio is 1:10. That would mean my MacBook Pro's headphone output is (supposedly) better matched to my QSC when its input switch is set to "mic." Who knew?

[jazzpiano88]

You're right.  EE principles tell us to match impedance to maximize power transfer, but in the audio case of XLR and Line it almost always doesn't matter because there is always enough signal that an impedance mismatch is ok.  All you need is enough current to drive the amp to operate in a good noise performance.  This also makes sense that amplifier design is almost always high impedance input (even 2k is considered high) and low impedance output to drive speakers or headphones. 

 

Sorry for my incorrect comment above (I'm more of an RF, Antenna guy).  One thing to keep in mind is that the signal levels can be anything and not always conform to High Impedance High Level and Low impedance Low level.   A good example is your headphone out which is low impedance high level (> line level), like in the case of an Amplifier output.   Hence the need for you to turn down the gain as it is about twice the usual line level.  Interesting discussion!

[funkyhammond]

Anyone have any experience with the old JBL Eon 510 (or the 500 line in general) and how much of a sound upgrade the current line of 10" Yamaha DBX/DBR or QSC K10.2 would be? This will be mostly for a small practice space and a small band and I'm trying to get acoustic piano patches to sound more hi-fi and less tinny (and hopefully also better lows but not a priority). I won't want to spend the money if acoustic pianos are going to sound hardly any better. I don't need huge amounts of volume so is the DBR as good of a choice as the DXR sound-wise? I will see if I can get the Yamahas to test out or rent first but just thought I'd get some thoughts if anyone has experience with those JBLs.

 

EDIT: Looks like I can rent an HK Audio Polar 10 to try out. Would this probably be more hi-fi than the Yamaha or QSC? That's what I've generally read about column speaker arrays.

[Sam Mullins]

Has anyone checked out the Electrovoice Everse 8? Looks kind of sweet. 16 pounds with 4 channel mixer and can be run on an internal battery that last 12 hours. Would think buskers would be all over this. 

[drand48a]

Hey, I'm back.  I put speakers on the back burner for a while but I'll have a chance to hit the big box stores soon, so I can audition a few.  Sam Ash & GC.

 

Regarding impedance matching: that's important for dynamic mics, which have low signal levels.  Matching impedance maximizes power transfer which maximizes S/N ratio.  Plugging anything but a dynamic mic, and impedance matching doesn't provide anything detectable to the ears (or probably even to test equipment.)

 

Regarding old JBL Eon 500's, a friend used to have some big ones (15" IIRC).  This was about 10 years ago, and they weren't new.  IMHO his Hammond clone sounded great through them, and his RD700 sounded good enough.  But a modern powered speaker will sound obviously better, especially for piano.

 

Regarding the QSC's input circuit, thanks for the schematic and specs.  I can't read the schematics well enough but the specs are clear.  Long ago, the relatively low impedance (2260 Ohms) might cause some line outputs to fail.  These days, you can generally even short them and they don't fail (but they don't sound good! or at all ...)  No idea how much this might compromise the sound, but my guess is, not much if at all.

 

Ideally, mic inputs are about 600 ohms.  I'd avoid plugging a line output into that.  Line outputs used to be rated with "minimum load impedance" or "maximum load impedance" which oddly enough mean the same thing, and for most of them, it was 5K or 10K.  These days you never see that rating, so must not be important anymore, so I wouldn't worry about 2K or higher.

 

I'll let you know what speakers I end up checking out and how the sound.  Old ears means I won't be splitting hairs on audiophile quality stuff -- can't hear much past 8K anymore.  But I can definitely hear the suck of for example a Behringer.

[Mark Schmieder]

On 12/9/2022 at 5:07 PM, Sam Mullins said:

Has anyone checked out the Electrovoice Everse 8? Looks kind of sweet. 16 pounds with 4 channel mixer and can be run on an internal battery that last 12 hours. Would think buskers would be all over this. 

Interesting timing, as I had a rehearsal last night for an upcoming show and an additional acoustic guitarist/singer was drafted for a few tunes. He sounds amazing through the Everse 8, and it worked great on stage the night before as well (where we only did six songs as part of a showcase of several acts). He said it's really expensive though.

[cassdad]

Sure, a guitar, as a limited range instrument, will sound great through the EV Everse.  I sincerely doubt they would do the same for a full range piano.  One of my bands is using them, and being kind, I’ll just say that they lack “punch”.

 

Re the topic at hand:  FWIW, I side-by-side bought and tested for days both the QSC K10 and the Yamaha DXR-10s (not DBR). In my end analysis, for piano, the Yamaha DXR10s were much better for piano (and everything else, of course, full-range piano being the most difficult).  I use the DXR10s under a myriad of different situations and environments, and have been told (including pianists) that they sound great in the audience.  (I do not work or have any vested interest in Yamaha).  FYI, they are rated at 131dB ( not sure I believe it, but whatever, they are powerful and clear, and I use them in a rock band scenario, including outside, and they keep up just fine).  Also, I do NOT use a mixer, plugging my Yamaha MOXF8 outputs directly into the DXR10s with no problem…. set the volume on the DXR10s at about -8 dB (well below unity gain), and they kick plenty loud).  I just run them “flat”, and they sound pretty darn good.

Furthermore, Yamaha now has come out with the DXR10 Mark II, which has a larger, more powerful, HF compression driver with neodymium (my old original DXR10x have ferrtie [iron] magnets).  Thus, the new Mark IIs should be even lighter and slightly more powerful.  But I’ve been so satisfied with my old DXR10s, that I have no desire to upgrade nor spend the extra money.

 

I’ve wanted to upgrade to the DZR10’s but they are 10 pounds more (wood cabinet), and I just can’t stomach the extra weight.

 

P.S. Putting the DXR10s on small step stools (8 inches high) makes a world of difference in “throw” and clarity (removing any “mud”).

[drand48a]

Sadly, it seems I'll only be able to audition the QSC and JBL speakers.  GC and Sam Ash don't carry the others, not even the Altos.  Sigh.

 

Thanks for pointing out the DXR rather than DBR -- the DXR looks like a better contender (but since I can't audition them ...)

 

I suppose I could order the others and send back whichever ones lose the shootout.  That means an extra 5-hour round-trip drive to return them, but ... ah well.

[cassdad]

1 hour ago, drand48a said:

Sadly, it seems I'll only be able to audition the QSC and JBL speakers.  GC and Sam Ash don't carry the others, not even the Altos.  Sigh.

 

Thanks for pointing out the DXR rather than DBR -- the DXR looks like a better contender (but since I can't audition them ...)

 

I suppose I could order the others and send back whichever ones lose the shootout.  That means an extra 5-hour round-trip drive to return them, but ... ah well.

Well, i understand, but…..  when trying out, I ordered them on-line, so when they arrived I then had all the original packing, and saved it to use to mail back the “losers” in my personal speaker shoot-out.  But acknowledged, your situation might make that impractical.

[drand48a]

1 hour ago, cassdad said:

Well, i understand, but…..  when trying out, I ordered them on-line, so when they arrived I then had all the original packing, and saved it to use to mail back the “losers” in my personal speaker shoot-out.  But acknowledged, your situation might make that impractical.

 

Free return shipping?  Not sure how they could profit that way.

[cassdad]

6 hours ago, drand48a said:

 

Free return shipping?  Not sure how they could profit that way.

Not free….   but, to me, the return shipping money on the not-wanted units was worth it to ensure that I was making the best purchase for me.  I see it this way:  at $850 each X 2 = $1,700…..  if it cost me a hundred in return shipping, that $100 ensured me that I was spending the $1,700 on the best of the lot.