New lt weight amps vs old heavies

[fdeck]

Just to keep you content Bob, I hereby vow to use the technically correct terminology for rectified mains frequency non-linear power supplies, hereafter known as REMFNOLIPS.

Just be careful that "mains frequency" is 50 Hz and "line frequency" is 60 Hz.

 

[fdeck]

Nope. Speaker impedance is dynamic based on frequency. An 8-ohm speaker can have an impedance as low as .5 Ohm to as high as 25 Ohm. 8 is its nominal (average, at rest) impedance. With really low impedances you need more current available.

My point was that the relationship between voltage and current is determined by the speaker not the amplifier. This is true regardless of the nature of that relationship. You are correct that it is frequency dependent.

An amplifier is designed to produce an output voltage that is reasonably independent of output current. The amp only has to supply as much current as can be drawn at the minimum impedance, which is around 5 Ohms for an 8-Ohm nominal speaker.

There is no particular reason to think that a heavyweight amp can supply more current than a lightweight amp if they have similar output power ratings. In both cases, all of the current passes through tiny little chunks of silicon, or slightly larger chunks of vacuum.

 

[grooveway]

Wow! What a great forum/website. I recently found it because I was looking to update the rig, and everyone has been great.

The information you guys have given to this post has been very helpful and also taught me a lot (and refreshed some of my basic electronics understandings).

Here's what I think I heard - a newer lighter weight power amp shouldn't have that much effect on the tightness and punch I like and have now. This would allow me to keep the Trace GP7SM and lighten the rig. That would make my recently purchased EBS 350HD a good low volume/backup amp. (KJung - from what I understand, this used to be yours). Bought it because I had used an older EBS pre-amp a year ago and liked it. What I'm finding now is I love the tone in my room, great clean highs and warm lows, but can't get the mids or the punch I need live. Also have to run it pretty hot to keep up with the rooms we play. It also doesn't really like the 18v actives in my Modulus Q5.

So, I may look into the TF 550 or 750 or the Epifani PS600 instead. As such, I'll ask for some further advice - we really don't have much to choose from in music stores here, so testing before I buy is difficult. I'm not good at describing tone but I would say it's close to Foghat (Nick Jameson) on the solo in Slow Ride, but just a little warmer sometimes on the lows. Given that butchered description, any thoughts on what might work. By the way, haven't completely fallen in love with the Eden's I've played through at festivals or the GK's, but that was plug in-and-go-fiddle-the-knobs-for-30-seconds.

Thanks for the patience.

By the way, the Boogie 15, and an Epifani 112 was a killer setup the other night. Next up is the 112 with the Boogie 210 (loaded with Edens - it came used that way).

 

[Jerrold Tiers]

Please explain how it can be lower than Re as a single driver design, or how if in a multiway passive xovered speaker it could be nominally 8R with a dip to 0.5R. An example would be nice.

The actual physical impedance/resistance can't be less than what it is......

However, a driver can present a 'reactive" load, where there is a large current drawn when output is at at or near zero volts. Just looking at the current and voltage, you'd say the impedance was very low.

Any speaker with a crossover, depending on how well it is designed, may have an impedance 'dip" at crossover. With a poorly designed passive crossover, two drivers may be loading the amp at once, or the crossover itself may be drawing current due to a resonance effect that wasn't dealt with in the design.

many speakers which have been "tweaked" as to the crossover to provide best response, have bad impedance curves due to this sort of thing.

 

[agedhorse]

Excellent post and good info Jerold! These are concerns every amp designer must consider when developing product.

Current, voltage, power are all inter-related, and all are vector quantities (meaning there is both a magnitude and a direction associated with them), the magnitude is the amplitude or level and the direction is the phase angle. Power is volts x amps BUT the phase angle must be used in the calculations to reflect what Jerrold refers to by reactive load.

 

[A9X]

The actual physical impedance/resistance can't be less than what it is......

However, a driver can present a 'reactive" load, where there is a large current drawn when output is at at or near zero volts. Just looking at the current and voltage, you'd say the impedance was very low.

Any speaker with a crossover, depending on how well it is designed, may have an impedance 'dip" at crossover. With a poorly designed passive crossover, two drivers may be loading the amp at once, or the crossover itself may be drawing current due to a resonance effect that wasn't dealt with in the design.

many speakers which have been "tweaked" as to the crossover to provide best response, have bad impedance curves due to this sort of thing.

The post you quoted was sarcasm.

The vast majority of typical MI speaker enclosures are simple single or series, parallel or combinations of the same drivers. In these cases Re defines the minimum Z.

Some MI boxes have xovers for HF drivers, usually simple HPF element or at best 2nd order. I find it difficult to beleive that in an MI box, the Z at any frequency will dip to 1/16th of it's nominal Z, or 1/10-1/12 of it's Re without a major design flaw in it's xover.

I invite you to show me the measured curve of one.

I'd also like to cite John Atkinson's Stereophile tests. Though Stereophile is full of flowery prose, the measurements, usually on an AP One are excellent. Even with the often complex xovers of multiway hifi speakers, such a massive drop in speaker Z is extremely rare in direct radiator dynamic driver designs; electrostatics may drop this much at a very high freq. In MI designs it would be rarer still.

Being concerned about a drop to <10% Re is a waste of time. many amplifiers would not deal with such at any level, let alone in the mix and match way many musos use their varied cabinets.

 

[KJung]

That would make my recently purchased EBS 350HD a good low volume/backup amp. (KJung - from what I understand, this used to be yours). Bought it because I had used an older EBS pre-amp a year ago and liked it. What I'm finding now is I love the tone in my room, great clean highs and warm lows, but can't get the mids or the punch I need live. Also have to run it pretty hot to keep up with the rooms we play. It also doesn't really like the 18v actives in my Modulus Q5.

Your description is exactly why I sold that head a while back. At 350 watts, with an inherent mid scoop in its tone, and only a single mid control, that's probably not the best example of some of the newer lighter weight amps in the 500-600 watt range that have more punch and 'weight' to their tone.

That being said, it's a beautiful sounding amp, and when run into an efficient 4ohm cab, it's a pretty nice sound if you like it sizzly and modern.

 

[agedhorse]

Horn loaded cabinets are one example of where the actual electrical speaker impedance may vary widely from nominal impedance. The acoustic impedance will reflect back mechanically to the driver, resulting in adding to or subtracting from the electrical impedance. It's all due to the "transformer" nature of these transducers.

All cabinets exhibit this effect to some degree, though 1/10th the nominal impedance may be a bit of a stretch.

Also, poorly designed crossovers canm definately cause problems, again energy storage in the elements and resonant (tank circuit) effects can cause some wildly unpredictable results. That's a lesson I learned early in my career.

 

[grooveway]

KJUNG - Question then on the Epifani PS600 it looks like it also has a single mid control, which has been my hesitation on purchasing. Or is it more flexible?

Thanks

 

[KJung]

KJUNG - Question then on the Epifani PS600 it looks like it also has a single mid control, which has been my hesitation on purchasing. Or is it more flexible?

Thanks

That is one of the things that has kept me away from the Epi stuff in the past. However, I ordered a 502 a couple of weeks ago, and it's due in any day. I've played the 502 enough now, and the mid control seems voiced quite wide, so even though the amp is voiced a little bit to the lows and highs, it can get nice and punchy. That being said, I still prefer either a more mid voiced head like the TF, that also has filters and enough mid EQ that you can roll some out if you want, or the Markbass LMII or F1, both of which are very 'flat'.. meaning plenty of even mids, but two nicely voiced mid EQ bands to tweak the balance between the upper and lower mids... AND an enhance type control to boot.

I'm looking forward to checking out the new Genz Shuttle 6.0 also... tube in the pre, about 5 pounds, 600 watts, one semiparemetric mid, but the amp is voiced to the mids a touch if it's anything like some of their other offerings.

That's just me though... the Epi stuff is voiced very nicely, and the extra power and more even voicing to me would make the PS600 punch more then the EBSHD350.

All of this stuff sounds good, just depends what you want.

K

Edit: So much has to do with the inherent voicing of the head... a somewhat 'scooped' voiced head (to my ear) like the EBS350 with only a single mid control doesn't work for me. On the other had, the mid voicing of the TF is so good to my ear, that I rarely use the massive number of semi-parametric mids. With the LMII, I find the two mid bands work wonderfully to slightly change the nature of the mids of that amp. I haven't spent enough time with the Epi at this point, but my guess is, if you like the HD350, you would LOVE the Epi... similar sheen and sparkle, deep lows, but seemingly a bit more mid voiced to begin with, and much more power.

 

[A9X]

Horn loaded cabinets are one example of where the actual electrical speaker impedance may vary widely from nominal impedance. The acoustic impedance will reflect back mechanically to the driver, resulting in adding to or subtracting from the electrical impedance. It's all due to the "transformer" nature of these transducers.

Front loaded horns will typically raise Z, along with a number of additional peaks due to the typical truncation/small mouth over a theoretically perfect horn.

All cabinets exhibit this effect to some degree, though 1/10th the nominal impedance may be a bit of a stretch.

Precisely my point, hence the original sarcasm.

 

[agedhorse]

Front loaded horns will typically raise Z, along with a number of additional peaks due to the typical truncation/small mouth over a theoretically perfect horn.

Correct, but below the cutoff, things can get less predictable and with folded horns and goofy compression chambers and ports and taps things get even less predictable.

For ported cabinets, (sub cabinet specifically) generally there are a couple of impedance dips below what would normally be considered a reasonable nominal value. The big problem for an amp designer is when on say a (poorly designed) sub cabinet, there exists 30-40% of the 35-100Hz bandwidth that is substantially sub-nominal. The amp MUST have adequate safe operating area to accomodate reasonable conditions, but IMO this is not reasonable. Many pro amps can handle this, and it's one reason why they cost a lot more. Other amps will just go into protective VI limiting (seperate for a signal limiter) and that sounds terribly nasty IMO.

 

[VicDamone]

To get back to the original poster's query. Switching, or class D, amplifiers have now become a large variety of designs and as with tube and linear solid state amplifier's should no longer be casually generalized as to their sonic personalities. Point being, suggestions are no substitution for a personal audition.

Many leading Hi-Fi and pro powered subwoofer manufactures rely on class D designs for output power. The transient attack and decay provided by many class D designs is so sharp and defined it's easily confused as sounding thin when actually its all but eliminated the shortcomings of more traditional designs. I recently had the opportunity to borrow a QSC Powerlite class D to replace my trusty PLX2402 to power my Bag End ELF system. The difference was, 'I've got to get me one of these,' stunning. Nice work QSC!

Clarity and accuracy are not typically required for instrument amplification so this may be a moot point. IMO class D is perfect for bass amplification. If your looking for the subtleties of tone that traditional designs provide, todays effects can get you very close without the weight. I'm thoroughly satisfied with my Acoustic Image powering my Bergi HT322. An opportunity to power an Ampeg 8-10" trunk freshly loaded with Tone Tubby drivers with the little AI was surprisingly effortless.

Vic

 

[KJung]

To get back to the original poster's query. Switching, or class D, amplifiers have now become a large variety of designs and as with tube and linear solid state amplifier's should no longer be casually generalized as to their sonic personalities. Point being, suggestions are no substitution for a personal audition.

Many leading Hi-Fi and pro powered subwoofer manufactures rely on class D designs for output power. The transient attack and decay provided by many class D designs is so sharp and defined it's easily confused as sounding thin when actually its all but eliminated the shortcomings of more traditional designs. I recently had the opportunity to borrow a QSC Powerlite class D to replace my trusty PLX2402 to power my Bag End ELF system. The difference was, 'I've got to get me one of these,' stunning. Nice work QSC!

Clarity and accuracy are not typically required for instrument amplification so this may be a moot point. IMO class D is perfect for bass amplification. If your looking for the subtleties of tone that traditional designs provide, todays effects can get you very close without the weight. I'm thoroughly satisfied with my Acoustic Image powering my Bergi HT322. An opportunity to power an Ampeg 8-10" trunk freshly loaded with Tone Tubby drivers with the little AI was surprisingly effortless.

Vic

And to build on your comment, small and lighweight is no longer dependent on being class D. Lot's and lot's of different designs in the 'under 20 pounds' category (and now, there are even class A/B amps with SMPS under 6 pounds!) that just kill with various combinations of amp classes and power supply designs..

Even though I agree with you that you shouldn't generalize, I agree with your generalition about class D amps.. as a group, they seem to be voiced to the 'transparent, clean, quick' side of things (AI, iAmp, Markbass F1/SD800, Walter Woods, Epifani502/902, etc.) versus other designs. Not sure if that's a function of being 'class D', or if the designers who are attracted to class D amps have those tone goals in mind and just want to keep it small.

IMO!

 

[Bob Lee (QSC)]

Class D is a simple concept--PWM, proportional to the signal voltage--but getting there cleanly and without excessive artifacts is not easy. IOW, great sonic performance is not inherent to class D; it has to be engineered that way.

 

[joegeezer]

Maybe you guys in the know, can explain my dilema, with the lite weight amps. I have to say, that I have only tried the 1 space amps. If I'm going to get a lite amp, it only makes sense to me to get a single space amp. I tried the Peavey Deca528, the DPC750, DPC1000, DPC1400X, the SoundtechPS800. The DPC1400X being the most powerfull of the bunch and the most powerfull to be had, till we just found out about the StudioR ACE, I thought would be useable for my bass rig. I found it only useable at small club volumes. All of these amps when cranked up hard, and put into a clip, would clip so violently, that it would make you almost think they were going to explode. The most harsh electrical arcing sounds I have ever heard coming out of my speakers before! All of these amps, when put into a clip will do this. Scary Nasty! Put me off of even using them again. I went back to my Carvin DCM2500 for my rig. I still have a Deca528, that just runs HF horns in my PA. Sold off all the others. This new StudioR ACE 1 space amp has sparked my interest again, but I won't be the first one here to buy one. Someone else can flog one for a while before I'll bite again.

 

[KJung]

Maybe you guys in the know, can explain my dilema, with the lite weight amps. I have to say, that I have only tried the 1 space amps. If I'm going to get a lite amp, it only makes sense to me to get a single space amp. I tried the Peavey Deca528, the DPC750, DPC1000, DPC1400X, the SoundtechPS800. The DPC1400X being the most powerfull of the bunch and the most powerfull to be had, till we just found out about the StudioR ACE, I thought would be useable for my bass rig. I found it only useable at small club volumes. All of these amps when cranked up hard, and put into a clip, would clip so violently, that it would make you almost think they were going to explode. The most harsh electrical arcing sounds I have ever heard coming out of my speakers before! All of these amps, when put into a clip will do this. Scary Nasty! Put me off of even using them again. I went back to my Carvin DCM2500 for my rig. I still have a Deca528, that just runs HF horns in my PA. Sold off all the others. This new StudioR ACE 1 space amp has sparked my interest again, but I won't be the first one here to buy one. Someone else can flog one for a while before I'll bite again.

I think there are two parallel discussions going one... one involving lightweight integrated bass heads (which I think is what the OP is talking about), and the other involving PA type class D/SMPS amplifiers. Can't comment on those.

 

[greenboy]

Hey Joe (dah-dah dah-dah dah),

I've got to say I think you must have been doing something wrong with the DPC-1400X or had a defective one because some of the clubs around here have pretty shoddy electrical service and in nearly 10 years of use, the majority occupied by solid weekend gigging, I've never had an outage, never clipped audibly unless I was driving way past the limits (though I have made speakers go into overexcursion a few times), never have blown a fuse or tripped a breaker, and never gotten any less than I've gotten from other amps in the power class that from time to time have been used in those same clubs. I've used it bridged into 4-ohms, dual mono into 8, 4, and 2 ohms...

In fact its low draw/high conversion efficiency has stood for me in times and places when higher draw amps were tripping breakers. Until recently, because of my first major cab changes in that period I haven't even considered another amp purchase for the bass rig.

 

[A9X]

Correct, {snip}......

We are several miles OT here. Happy to discuss this elsewhere, but I'm an EE and have been designing amps and speakers for years, so the theory and it's application is hardly new to either of us.

Class D is a simple concept--PWM, proportional to the signal voltage--but getting there cleanly and without excessive artifacts is not easy. IOW, great sonic performance is not inherent to class D; it has to be engineered that way.

Yes.

And to build on your comment, small and lighweight is no longer dependent on being class D.

I've had my conventional AB with SMPS Yamaha amp for 2 years. It's 12kg (26lb) but is 700W/8R/ch, considerably more than specialised bass heads.

 

[A9X]

I think there are two parallel discussions going one... one involving lightweight integrated bass heads (which I think is what the OP is talking about), and the other involving PA type class D/SMPS amplifiers. Can't comment on those.

Technically, there is likely to be little difference between the types apart from packaging. The designs used inside MI specific products will not be different in any sort of fundamental way than the PA designs. Specific details such as size, power, voicing etc will differ.