Zaph|Audio - Energy C500 tests and review
Energy C500 tests and review
Seas L18 all metal beater...
A forum user recently declared a commercial retail 2.5 way tower as sounding better than the L18 Seas all metal system design on this web site. That is completely OK with me, I'm not a kind of guy that ever gets defensive about anything. But I do look at it with the curiosity of a scientist. Here was my response:
The measurements will tell us what makes the C500 sound better than the L18 system to this person. Was it the 35 Hz bass extension? Was it the output capability? Are the C500 drivers lower in distortion? Was it just a failure to match levels and be tricked by the more sensitive system? Could be any or all of these things, but the simple fact is that a person liked the sound better. Some objective testing will certainly give us more insight than some subjective commentary.
Energy C500, part 1...
My write-up on the Energy C500 will come in 4 parts. 1)listening commentary, 2)build quality review, 3)measurements and 4)crossover fixes if I deem worthwhile. Part 1 is below, part 2 comes tomorrow, then due to a couple other projects on my plate there will be a slight delay before I get around the measurements and mods.
The speaker only took 1 day for delivery, less than 24 hours, to arrive here in Wisconsin from Audio Advisor in Grand Rapids, Michigan. Cost: $400 plus $53 for shipping. I've been listening for half a week now. Some might think that the first thing I would do is take measurements then make an evaluation without even listening to music. True with raw drivers, but not true with completed systems. They were packed well. I opened them up, ran the system at full Xmax for a couple hours and allowed them to cool down. Interesting note: the manual says they need 100 hours worth of breakin, which is complete BS. Most systems don't
change much after the first couple minutes of high output. I could think of a few devious reasons why a manual writer would ask for 100 hours of breakin, and here it is: Most likely they don't want you to return the speaker after the first couple weeks if you finally decide don't like what you hear. They want you to get all the way through the phases of "Wow, these sound great" to "Hmm, some things annoy me about the sound" to "they don't annoy me quite as much now." Some time later you fly past the vendor's return period and you're stuck with speakers you don't like while the seller and manufacturer chalk you up as a happy customer.
I listened in two rooms, one large and one small, set up in positions previously known to work well for most systems. First immediately obvious issue: these are bass heavy. It's somewhere between warm and boomy, maybe a little of both. There seems to be a little one-note tendency on the low end, easily brought out by some rock recordings with kick drums. Much more so than my normal room nodes would emphasize. Then there's a little too much output in the lower midbass. Some male vocals seem a little too high in level. It's pretty much the typical sound you get from a high Qts woofer in a large vented enclosure.
There also seemed to be a little grunge (Thesaurus: muddy or unclear) in the midbass and lower midrange. This is separate from the previously mentioned level issues, and somewhat difficult to differentiate. Everyone has their favorite test recordings but for me, well recorded vocals and piano bring it out the most. This may have been due to non-linear distortion inherent to the woofer, but it may also have been due to insufficient enclosure rigidity. It's very difficult to tell and I may not know the real source until future measurements. It wasn't too bad, but definitely audible compared a higher end 5" TM and a larger MMTMM I currently have in the house. The C500 could not match the midrange clarity of those systems. I didn't do fast switch A-B comparisons because I think it is important that the speakers being compared occupy the same positions in the listening room. As an informal level match, I would turn each one all the way down then with the next system bring it back up to what sounded roughly the same. If I had to guess at sensitivity doing a quick switch A-B comparison with a system of a known level, I'd say about 89dB anechoic. The system did indeed seem to handle power pretty well and get very loud without excessive strain, particularly with the ports open. I did install the supplied port plugs later to help resolve some of the boominess. Nice touch. A lot of the depth and power handling went away, but in my opinion it made the system more listenable at my normal levels.
While the upper treble seemed clean and smooth enough, it sounded like there was a mild dip in the lower treble. Not quite as bad as you might hear with a miswired tweeter polarity in an even order crossover system. It might even sound a bit like what happens to the above axis and/or power response when you configure a TMM as a 2-way rather than 2.5. (no idea of the C500's configuration yet) This probably makes the warm and grungy region sound worse than it actually is.
So far I'm mildly disappointed in the sound, given the hype. This sounds like a lot of complaining but I am being quite critical and there was nothing overly offensive about the system. The C500's sound better than the Insignia's out of the box, and they sound better than the PE BR-1 kit also. The insignias while being relatively clean, have some annoying response issues in the upper midrange while the BR-1's have more of a sizzle/boom/grunge tonality. With the C500, some rock music was particularly "fun" to listen to and without the port plugs it gave a nice in-the-chest slam when the bass kicked in. It's not exactly accurate though and it ruined much of my music that does not benefit from that type of coloration.
Anyway, that's my subjective review, which is about as useless as most other subjective reviews. Note that it comes without discussion of equipment used or music played, which is useless filler and typical audiophile rubbish. Stay tuned for more meaningful information. (read: measurements) Meanwhile, I need to jump in the shower, because that much subjectivity makes me feel unclean. :)
Energy C500, part 2...
Here's the C500 build quality review. On a scale of 1-10 with 1 being white van speakers and 10 being the average $10,0000+ speaker, I'd give these a 3. A couple of the positive items are a nicely finished gloss black front baffle with CNC countersinks. The front baffle is 21mm thick, just over 3/4". The crossover has a surprisingly high parts count of 11, meaning there's a good chance it's actually doing something useful besides protecting the tweeter. The only concern might be the size of the components - 2 very small electrolyic caps and 3 tiny inductors. Power handling is the main concern there, not sound quality. There is one poly cap, probably on the tweeter. Ports are nicely flared on both ends. A shelf brace does exist though it's only about 3/8" thick. The terminals look nice. The grill is a nice design, as it is form fit to the radius at the bottom and the inside area around the tweeter is beveled to limit edge reflections. On the negative side, the side enclosure walls are only 5/8" thick and very resonant. It's only partially covered with insulation. The knuckle rap test fails, but that's generally not the best way to judge rigidity. When playing music you can really feel the walls vibrate. The finish is black wood grained vinyl, and there's no mistaking it for any sort of wood. It looks like black plastic.
The woofer seems to be a paper base with the gray textured fiberglass adhered to the front side. The cone has a curved profile and seems relatively thick and stiff. The dustcap is a sharp parabolic shape and painted silver. Could be visually mistaken for a phase plug and that's probably the idea. The frame is stamped steel of a flimsier thickness than most stamped frames. The magnet is tiny and there is no ventilation of any kind anywhere. The tweeter is a smallish neo, though size is no judging point for quality. There seems to be a ring glued to the inside of the perforated grill. The tweeter has a fabric surround and appears to have a rear chamber.
Overall these speakers look pretty cheap. If I had paid the full USD $750 for the pair, I would not be happy. But they seem to be worth it for the discounted $400 per pair. They are definitely a few steps above white van quality and there are are at least a few concessions to sound quality. If I could improve one thing, it would be the flimsy side walls. I'm pretty sure I can hear them resonate in the midbass.
Energy C500, part 3...
Driver and system measurements will be shown and discussed in this section. Let's start with the individual drivers.
C500 Tweeter
![[Image]](C500T-FR.gif){kind=link}
![[Image]](C500T-HD.gif){kind=link}
![[Image]](C500T-IMP-2.gif){kind=link}
![[Image]](C500T-CSD.gif){kind=link}
C500 Woofer
![[Image]](C500W-FR.gif){kind=link}
![[Image]](C500W-HD.gif){kind=link}
![[Image]](C500W-IMP-2.gif){kind=link}
![[Image]](C500W-Le(x).gif){kind=link}
![[Image]](C500W-CSD.gif){kind=link}
![[Image]](C500W-TS.gif){kind=link}
Overall, not too bad, though the drivers are quite a bit different from what the average DIY'er is used to. The tweeter is very clean in the non-linear distortion department. It has a strangely high Fs at 2.7kHz and early low end roll off. I could not even see the impedance peak without a zoomed in plot. The low end is clean enough to actually operate well below Fs. The top end has a dip in the response, which is not going to be very audible. Everywhere else it's relatively smooth. The tweeter reminds me in some ways of the Vifa DQ25. In other words, very nice. Measurement conditions were the same as the tweeter group elsewhere on this web site.
The woofer has a respectably flat response, however it has a very high inductance with related upper rolloff. Impedance is 45 ohms at 10kHz and the rolloff starts at 300Hz. This immediately made me wonder if the system is really configured as a 2.5 way since there's not really enough response in the high midrange to work with. We'll see in some other measurements below. In any case, this kind of smoothness is commendable and the soft parts of this driver appear to be well designed even though some obvious cost cutting measures have been taken. The harmonic distortion, while not great, is good enough to not be an much of an audible issue, particularly when two woofers are in use rather than just one. The Le(x) plots show major inductance changes at excursion limits, and Qts is very high. This is all the result of a simple and small motor.
Moving on to the system measurements, let's start with the internal dimensions. I measured approximately 12 x 6.5 x 34.5 = 2691 cu in = 1.557 cu ft = 44.1 liters. There are two ports, each 2.75" [69.8mm] x 7.5 [185mm] Calculated tuning comes out to 45 Hz and actual measured tuning as usual is slightly lower at 42 Hz.
![[Image]](C500system-IMP-vented.gif){kind=link}
![[Image]](C500system-IMP-sealed.gif){kind=link}
The impedance droops to about 4 ohms in the midbass. Since that's where most of the music is, this would qualify as a 4 ohm system, maybe considered 6 ohms nominal. The impedance curve is very smooth. The system comes with foam port plugs, a nice touch and for many people, a requirement to avoid one-note bass.
![[Image]](C500system-FR-sealed-anechoic.gif){kind=link}
![[Image]](C500system-FR-sealed-individual-anechoic.gif){kind=link}
System response curves were taken with the port plugs in place. All the normal methods to acheive an accurate representation of anechoic response were used. A 200ms window nearfield on the low end was modified by a baffle step and diffraction simulation and then merged with a 10ms window semi-far field. The crossover frequnecy appears to be 2000 Hz, but tweeter 6dB down point is 3kHz and the woofer 6dB down point is about 1200 Hz. The woofer level is a few dB higher than the tweeter level. This all adds up to a lack of lower treble and a preponderance of midbass. Response is smooth, but quite innacurate. There will be even more droop in the response off the horizontal axis in the upper midrange due to the woofer's piston diameter based upper rolloff. In other words, power response will be equally bad or worse than the on-axis response.
While I did not put together a vented anechoic curve, (a tedious pain in the ass to do right) rest assured that it would be the same except +3dB at 100 Hz and +8dB at 40 Hz. If that +8dB at 40Hz happens to line up major room node peak, get ready to plug those ports. Bass models are for both vented and sealed are shown further below for comparison.
![[Image]](C500system-FR-sealed-nearfield-top-bot.gif){kind=link}
Above we have a nearfield response curve of the top and bottom woofers. The measurement method was unconventional - a large wood barrier was positioned externally on the enclosure between the upper and lower woofers. The adds some reflection artifacts, but the artifacts will be the same for both measurements. This allows us to isolate the response curves and see differences between the upper and lower woofers while they are both mounted in the enclosures. So, don't pay attention to the response shape, only the differences between the two. I am trying to answer the question "is this a 2.5-way system"? The answer is.... hmmmm, sort of. The lower woofer does have a little more rolloff than the top, but the rolloffs are identical below 800 Hz. There is very little baffle step compensation built into the crossover due to the huge inductance in the woofers. For the vertical lobing, what we have here is a system with a taller vertical window than a TMM configured as a 2-way, but a much shorter vertical window than the average 2-way TM system. It's effectively somewhere between 2-way and 2.5-way. A full 2.5-way is not workable with woofers of this high inductance.
![[Image]](C500system-tuning-modeled.gif){kind=link}
![[Image]](C500system-tuning-modeled-bafflestep.gif){kind=link}
If you take the T/S parameters and enter them into an average box modeling program, you'll get something like what is shown in the first plot above. That's not realistic however. To get a better glimpse of reality, I've added in the baffle step and diffraction. Sealed resonance is still slightly off from reality due to the port plugs having some porosity. The measured sealed box anechoic response show above still matches the modeled low end closely.
![[Image]](C500system-FR-vented-inroom-1.5m.gif){kind=link}
![[Image]](C500system-FR-vented-inroom-2m.gif){kind=link}
![[Image]](C500system-FR-vented-inroom-2.5m.gif){kind=link}
For a glimpse of the response in a couple listening rooms, I've taken some room responses. Mic was at tweeter height. The 1.5 meter response was taken in a typical setup in a small room with the front of the baffle about 2.5 feet out from the rear wall and 3.5 feet from the side wall. The 2 and 2.5 meter responses were taken in a medium to large room, 3 feet out from the rear wall and 4.5 feet from the side wall. One of the common response issues is the primary floor bounce resulting in a dip/peak combo at 300 and 600 Hz. In these conditions, the anechoic response can't really hide. The dip helps some of the excessive output between 300 and 500 Hz but it's still lots of bass below that and a lack of lower treble. The peak at 600 is less audible than it seems as I suspect (but can't prove) at that frequency our brains differentiate between direct and reflected sound. Room nodes dominate the response below 200 Hz, with the 1.5 m measurement having a lot of output (read: one note bass) near the port tuning. I do room response curves with all my designs but I don't always post them because they are of limited use. Everyone's room is different. However if you dig into the SR71, ZRT and L18 designs, you'll see some examples in there.
Summary of measurements
None of the drivers in this system want to do much work in the lower treble, making the midbass seem even louder. This could be considered a full baffle step design, however there is no baffle step compensation built into the crossover - it's all in the woofer's massive inductance. There is really not much problem in the non-linear distortion of the drivers. While not great in that regard, they are acceptable. This system's coloration is primarly in the frequency response. Some of it could also be in enclosure vibration, but I did not break out an accellerometer to prove it.
Those willing to EQ could easily bring up the lower treble and vastly improve the overall tonal balance. An average wide band bass tone control centered at 100 Hz could also help somewhat with a good 6-8 dB cut. I think it's obvious that there will be a group of people who enjoy this system's natural tonality as is without wanting to make any changes. Some of these folks came forward on forums, which raised my interest in this system. For those, this measurement section is showing you what you get, and therefore what colorations you like. Those who want accurate sound, meaning they want to hear the music the way the recording engineer intended, will generally not be impressed by this system unless they are willing to EQ.
This system is a good value at the current discounted price of $400 USD per pair. It's not so good a value at the normal price of $750 a pair, at least in regards to what you can do for yourself with that amount of money along with some enclosure building and system design skills.
Page done by John "Zaph" Krutke © 2009
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