Zaph|Audio

Small Driver Comparison

About the Test

All response curves are with the drivers on an infinite baffle. All drivers are countersunk, and all baffle openings are chamfered in back for smooth airflow. Don't forget that in the real world, baffle step and diffraction will affect the curves. These curves are all far field, taken with a 10ms gating window. Below 600 Hz, a near field measurement is merged in for accuracy. Response curves include impedance curves at the bottom.

Close-up impedance curves are provided to show more detail that may not be seen in the response curve. Any variation from complete smoothness is generally a bad thing. Small bumps in the impedance curve, no matter how small, will always mean either linear or non-linear distortion. There may be a peak or dip in the response curve, or an increase in harmonic distortion to coincide with the impedance bump.

Cumulative Spectrum Decay (CSD) charts are 1/12 octave smoothed. Time slices are taken up to 3ms with the start marker right at the beginning of the impulse. All levels are equalized to 30dB to accurately show comparitive energy storage regardless of individual driver efficiency.

Harmonic distortion charts are taken semi-far field with the mic directly on axis. The far field method shows a more realistic top end distortion but does allow some room effect to show up also. The same conditions apply to all drivers. Amp output level was adjusted for each driver so that the fundamental is 96dB at 1/2 meter. Harmonics F2 thru F5 are tracked. F2=Green, F3=Blue, F4=Purple and F5=gray. In general, the higher the order of harmonic distortion, the more offensive the sound. The range is 20Hz to 5kHz and the level is +30 to -110 dB. The only tradeoff with doing HD tests far field are room effects. For normal DIY'ers like me, anything less than a full anechoic chamber is going to introduce some inaccuracies in the results. Important: there is a small room effect showing up at 240 Hz in all measurements.

The pros and cons of this type of harmonic distortion testing

There are two general types of harmonic distortion tests - Single frequency spectrum and fixed harmonic sweeps. I do sweeps, while many others do single frequency.

Single frequency has two primary benefits. First, the level at the fundamental frequency can be adjusted to the same level as other drivers tested, making easier a direct comparison at a single frequency. Second, very tall order harmonics can be seen. For example all the harmonics above F6 can be seen, along with other spectrum noise.

Fixed harmonic sweeps have several benefits. The first and foremost is that distortion is shown for all frequencies at once, rather a single selected frequency. Single frequency testing requires *many* tests to get a complete picture of distortion across the spectrum, and even then, sharp peaks in distortion could hide between 2 tested frequencies. With a sweep however, the primary harmonics F2 through F5 will be clearly shown at every frequency.

For example, if speaker with a large and very audible peak in the 3rd harmonic at 1.5kHz had single frequency tests done at 1kHz and 2kHz, the harmonic distortion would be completely missed. This is particularly important when testing stiff drivers with breakup nodes within the audible band. This is the primary reason I choose sweeps for harmonic distortion testing. There is a lot more information in one image.

We can't have everything with sweeps, and we loose the ability to see harmonics above F5. In my opinion, this is a fair trade off. Taller order harmonics far above the fundamental frequency are more audible than a low order harmonic of the same level. But tall order harmonics are typically at a much lower level. Looking at the data with trending in mind will help see around these limitations.

How to read harmonic distortion sweeps

Reading harmonic distortion sweeps is fairly easy. This section will deal with interpeting the data and "reading between the lines" to help see around the limitations of this type of testing.

These sweeps are not EQ'ed to flat. Nor are they filtered or crossed over in any way. This is both an advantage and a disadvantage depending on how the driver is used. It is an advantage if the frequency in question falls within a range that is intended to be run without any sort of response shaping or crossover. For example, the top two octaves of a tweeter or the midbass of a woofer. In that case, what you see is what you get. It is a disadvantage when the response curve will be modified to reach a target response shape. For example, an extended low end of a tweeter will have it's harmonic distortion reduced in the area where the crossover begins to take effect. A woofer crossed over to a sub will have it's audible distortion reduced as the woofer rolls off.

Related to the above, the enclosure tuning for woofers affects the low end distortion. The baffle dimensions and driver location for all drivers will also affect the distortion level due to baffle diffraction ripple response and baffle step response due to 2pi to 4 pi conversion. The most important thing to remember when looking at these harmonic distortion sweeps is how the drivers will be used.

There's a lot more information in these F2-F5 sweeps than may first meet the eye. You can get a pretty good idea of what's going on further up in the spectrum by looking at the level of the F4 and F5 in relation to F2 and F3 respectively. This is a form of trending. For example, to take a guess at tall odd order harmonics, draw an imaginary curve from the fundamental to the F3 and F5, and it's almost guarenteed that the F7 and F9 are going to fall close to where that curve extends.

For intermodulation distortion, there is nothing more definitive than looking at a 2 or 3-tone spectrum, but in my experience an F4 or F5 of a relatively high level almost certainly points to high IMD as much as it points to high spectrum noise. While I do not provide IMD plots, be aware that drivers with high HD are probably going to have high IMD and high spectrum noise also. All these forms of distortion are closely related.

T/S parameters are only shown for speakers with open backs in this group, N/A for all others. All T/S parameters are actual measured, not from factory data. All Vas numbers are done delta compliance since that method is more accurate than delta mass. Also note that the SPL number on the T/S parameters is an efficiency number based on one watt. Additionally, this number is calculated rather than actual. The SPL shown on the response graphs is a sensitivity number based on 2.83 volts and is actual rather than calculated. If you want to "believe" one, the SPL shown on the response graphs would be best to use. Also note that the Le number on the T/S parameters is not a good comparison point between software packages because of different calculation methods. The Le is often interpeted by software particularly poorly when the motor is complex with substantial faraday sheilding. For accurate impedance vs frequency, look no further than the driver's impedance curve rather than an arbitrary Le number. Flatter is better.

All parts of this test are done with Soundeasy 12.0. This is a modeling package with a lot of extra testing applications included. It is not a full acoustic measurement system such as CLIO or Praxis however, so take these results with a grain of salt. What is important however is that all of these drivers were tested in the same way. Because of this, my test results should not be compared with tests done elsewhere by other people, but comparisons within this group of drivers are perfectly valid. That's why tests like this are best done in groups.

There are a few types of tests that are important, but not shown here in the interests of brevity. Keep this in mind and know that these results need careful interpretation.

Results:

Comparison Application (Javascript Required)

Commentary and review: 5 Star Rating System, drivers sorted by cost.

Cost - Driver cost per one unit in USD. Cost and availability updated 12/14/2008

Usability - This is a function of both linear and non-linear distortion combined. The standard of reference is use in a "normal" system for that type of driver with a "normal" crossover. Obviously, dome midranges are not evaluated for bass performance. Some examples: Subtract points for a response curve that requires extra crossover components to fix or peaks in harmonic distortion that push the tweeter crossover point below a normal frequency. Add points for drivers that have particularly wide usable bandwidth or easily controlled response curves.

Build Quality - This is a combination of fit and finish, along with well engineered features. Some features may help performance in ways not covered here by the normal set of tests. Some examples: Subtract points for glue gushing out at the edge of the surrounds, an off center dustcap or a rough frame casting. Add points for venting behind the spider, clean tinsel lead connection, or an estimate of low air restriction through a frame design.

Consistency - Difference between units. This is primarily a comparison of a response curve and impedance plot, and assumes that I have two units to test. If I have more experience with a driver, this rating will have a greater level of accuracy. If I only had one to test, this category will have a "Not Rated."

Value - This is a comparison of cost to everything else combined.

Remember that aside from cost, the ratings below my subjective opinion. I am one person, namely John Krutke of Zaph|Audio. The ratings are provided for those who wish to know the opinion of this web site's author. I encourage people to use the objective test data, consider their own needs and form their own opinions. I also reserve the right to change these ratings, as I think about things over time and gain more consistency data.

Scan Speak 12M4631G
	Cost: $285 Usability: Build Quality: Consistency: Value:	Comments: This is a midrange specific driver. It is relatively sensitive at just under 90dB, but it's 4 ohm impedance is responsible for this. This uses the Revelator slit-cone design to control breakup and present a respectably flat and extended response. On the other hand, the motor construction lacks the copper faraday rings of it's larger siblings and has higher nonlinear distortion as a result. Still it's not too bad, and easily usable as a very wide range mid driver. Value is extemely low - It's a nice midrange but I'd expect more for that price. Tested February 2007.

Visaton Ti100
	Cost: $189 Usability: Build Quality: Consistency: Value:	Comments: Titanium cone midwoofer with a straight cone profile. Very well built but also very expensive. Smooth response with a large breakup node at 6.5kHz. Class leading harmonic distortion from 100-1kHz but rising above that. Low HD along with a low Le point to an excellent motor design. This will sound the best crossed around 1600hz to a large format tweeter, however it could work fine crossed higher depending on your tolerance of the 3rd order HD peak at 1800 hz. Tested July 2007.

Tangband 75-1558SE
	Cost: $86 Usability: Build Quality: Consistency: Value:	Comments: This is a 3" textile dome midrange with very good performance on all fronts. Smooth response with only mild breakup peaking at 7kHz. With the clean distortion profile, how low you cross is limited only by how loud you need them to play. My initial estimate is 400 Hz LR4 or 700 Hz LR2. A well damped resonance will likely not need a conjugate circuit to flatten impedance. The flange is fairly large and in some cases a small cone mid may be a better choice. The high pass crossover point will be limited by center to center distance and off axis rolloff, I recommend no higher than 3kHz. Off axis response curves available. Tested June 2009.

Mark Audio Alpair 6
	Cost: $70 Usability: Build Quality: Consistency: Value:	Comments: It's good wide range driver with a few flaws. There are no serious issues in the harmonic distortion and the response is extended. Aside from the metal cone breakup in the top octave, there is a major resonance at 1900 and a minor at 800. Not too bad, but generally outperformed by several other wide range drivers, most for less money. The Alpair's response curve is pretty far off from the manufacturers, which may indicate a consistency issue. Tested March 2009.

Seas L12
	Cost: $69 Usability: Build Quality: Consistency: Value:	Comments: Possibly the smoothest response curve to ever be had in a 4" woofer, aside from the metal cone breakup of course. The cone is a pure piston until the breakup node. The T/S parameters work to give this woofer respectably deep response in a small box. On the negative side the non-linear distortion is only average, and due to the breakup induced HD this woofer should cross over at 2kHz or lower. Definitely more of a woofer than a mid. Tested January 2007.

Vifa PL11WH09-04
	Cost: $64 Usability: Build Quality: Consistency: Value:	Coated paper cone midwoofer from the Vifa Premium Line. (now Peerless V-line) Very smooth and extended response, and very sensitive even for a 4 ohm woofer. This could make a good midrange driver in a high sensitivity system, with it's only downfall being merely average harmonic distortion through it's operating range. Tested July 2007.

Tangband W4-1337SA
	Cost: $55 Usability: Build Quality: Consistency: Value:	This is a very wide bandwith driver that could work as a small woofer, a dedicated midrange or even a full range driver provided a filter is used to tame the top end. This driver's breakup node above 10kHz does not propagate as harmonic distortion lower in frequency, meaning you can cross it over as high as you want. Harmonic distortion is merely average, but the smoothness of the response curve is class leading - a fair trade to many. This is a titanium cone, but it exhibits very "non-metal" behaviour due to the thin, light cone with exponential profile. Generally good value and consistency. It has a underhung voice coil that is vented under the spider, a cast frame and great build quality all around. Tested June 2007.

CSS FR125SR
	Cost: $50 Usability: Build Quality: Consistency: Value:	Comments: This is a 4.5" driver marketed as a full range, however I think it would still pay to use it with a cheap tweeter due to a top end rolloff. Very smooth midrange response and average but well controlled harmonic distortion through the midrange. Slightly high distortion below 100Hz for a woofer of this size. Usability is somewhat limited by a very high Qts and low sensitivity - traits that encourange using this woofer in a sealed enclosure with very little baffle step compensation. Tested June 2009.

Tangband W4-1720
	Cost: $48 Usability: Build Quality: Consistency: Value:	Comments: Underhung 4" woofer with a high Xmax for this size category. Like it's larger brothers, it has a relatively large motor. Good sensitivity, though not quite high enough to work in all 3-way systems as a midrange Overall good performance except for somewhat high bass distortion from wind noise in the motor, which nullifies the benefit of high Xmax. Tested June 2009.

Dayton RS52
	Cost: $41 Usability: Build Quality: Consistency: Value:	Comments: Excellent performing 2" dome midrange with a very wide, smooth bandwith and low distortion. Can be crossed over relatively high though the breakup will need some attention. Low end distortion is clean, and as a result the lower limit crossover point depends only on how loud the driver will be played. My initial estimate is 500 Hz LR4 or 800 Hz LR2. A conjugate LCR trap will likely have to be used to flatten this driver's impedance. This driver has a well designed motor with faraday shielding. Tested June 2006.

HiVi DMB-A
	Cost: $28 Usability: Build Quality: Consistency: Value:	Comments: This driver's flange is huge - as big as a normal 5.5" woofer. As such, that limits the upper crossover point due to vertical lobing, which in turn takes a star off the usability rating. Fs is a little higher than other 2" domes. Harmonic distortion is good. Frequency response has a mild dip at 3.5kHz, a smooth top end rolloff and a slightly high Q low end knee. All things considered, this isn't a very expensive dome and generally a good value. Tested June 2006.

Tangband W4-1052SD
	Cost: $28 Usability: Build Quality: Consistency: Value:	Comments: Wide range 4" woofer with a pattern stamped into a poly cone. Surprisingly good performance for a cheap driver with only some raggedness in the response above 5kHz marring it's review. The stamped steel frame is a solid good looking design and a cost cutting measure that is well chosen. Very sensistive for a driver of this size, though some of that comes from a solid 4 ohms impedance. This driver could be used as a wide bandwidth midrange if the low impedance is not an issue. Tested June 2009.

Dayton RS125
	Cost: $27 Usability: Build Quality: Consistency: Value:	Comments: Excellent performing small woofer, though it's lower efficiency will somewhat limit it's use as a midrange driver. This is effectively a 4" midwoofer with a rather large flange. Typical excellent Dayton RS build quality and consistency. Recommended highest crossover point is 2.5 kHz LR4. I don't recommend LR2 usage with this driver. This driver is visually beautiful. Excellent bass performance for this size driver. Tested June 2006.

Dayton RS100S-8
	Cost: $26 Usability: Build Quality: Consistency: Value:	Comments: This is a great performing 3" driver. The frame is a very nice casting with better than average ventilation. Very smooth, wideband response. Copper appears to be used in the right place in this motor, for very low distortion and no inductive rise. Could be used full range with a breakup notch and a shelving BSC filter, but would be even better paired with a cheap neo tweeter. The cost is not that low for a 3" driver, but considering the performance, value is still very high. Tested March 2008.

Dayton RS100-4
	Cost: $26 Usability: Build Quality: Consistency: Value:	Comments: Nearly identical performance as the 8 ohm version. This 4 ohm speaker is not shielded, has a lower Qts, and is about 3 dB more sensitive than it's 8 ohm brother, all at the cost of a rather low 3.0 ohms DCR. Tested May 2008.

Tangband W3-1364S
	Cost: $26 Usability: Build Quality: Consistency: Value:	Comments: Decent performing paper cone driver, made with bamboo fibers. It has a cast frame, underhung neo motor and a copper cap on top of the pole piece. Response is reasonably smooth except for a 3dB bump at 3kHz and a ragged top end. You can tell from the harmonic distortion plot that this is a soft paper cone with an exponential profile - It has relatively low odd order HD but very high 2nd order HD. That will probably give it a classic paper sound. I'd rate this at a similar or slightly higher level of performance as the Hi-Vi B3S, but at the price it's not quite as good a value. Tested June 2006.

Fountek FR88-EX
	Cost: $26 Usability: Build Quality: Consistency: Value:	Comments: This is without a doubt the highest performing 3" I've come across, at least on a few fronts. The motor is an underhung neodymium design and the cone is thin (and fragile) formed aluminum. The only negative is a slightly ragged top end that may take some filter work if used full range, but I'd generally recommend a cheap and small neo tweeter placed close and crossed over high. There's a lot on the positive side, like high sensitivity, a clean low end and smooth midrange response. The frame is cast with ventilation under the spider, but users will have to pay close attention to airflow behind the cone - It's even more important to chamfer the inside baffle opening and in this case likely use a thinner baffle material as well. Tested June 2009.

Aura NS3
	Cost: $22 Usability: Build Quality: Consistency: Value:	Comments: An exceptionally wide bandwidth driver, with smooth response. This is one of the very few drivers that "could" be run full range without a filter, though I'd still recommend at least a little baffle step compensation. If you choose to use a tweeter, you can cross over as high as 4kHz, with the only limiting issue being vertical lobing due to driver spacing. Minus one star in build quality for a stamped steel frame that is flimsy. Not nearly as a good an overall value as the HiVi B3S. Merely average or high harmonic distortion throughout it's entire usable range. Note: old versions of this had significantly better bass performance, taking 1.5 stars off consistency and 1 star off value. Old/Other tests available. Tested August 2008.

MCM 55-1840
	Cost: $19 Usability: Build Quality: Consistency: Value:	This is a low price, stamped frame woofer. Harmonic distortion is acceptable for something in this price range, but the response curve is a bit too ragged to work with. A 4" woofer should have a smooth extended top end response, but this one fails on that point, taking a severe penalty in the usability and value scores. A 4" woofer that requires a low crossover frequency is rather pointless. At $17, you can do much better. Tested June 2007.

MCM 55-3853
	Cost: $17 Usability: Build Quality: Consistency: Value:	Very nice performing cast frame version of the older MCM 55-1853 below. The price is $3 higher and the nice frame makes it well worth it. There are some minor improvements in response smoothness and harmonic distortion but it's obviously based on the same design. This is one of the value leaders in this group. Tested June 2008.

Peerless 830970
	Cost: $17 Usability: Build Quality: Consistency: Value:	(discontinued) This is a unique 2" wide range driver from Peerless meant to go with the smaller Tymphany LAT array. Appears to be well built with a well ventilated frame and a copper cap on the pole piece. It is indeed wide range, but the response curve has a massive peak/dip combo at 2kHz and the harmonic distortion isn't really that great. On top of that, the power handling of this driver anywhere below 300 Hz is low. Not a bad driver, but there really are no 2" drivers without serious limitations. Tested December 2007.

MCM 55-1853
	Cost: $14 Usability: Build Quality: Consistency: Value:	Almost completely unlike the carbon fiber MCM woofer listed above, this is a great little woofer for the price. Good, usable performance all around. The metal cone breakup node is not overpowering, and this woofer should be easy to massage into a 3kHz LR4 crossover. In other words, this driver will work well with just about any cheap tweeter. Build quality takes a small penalty with a flimsy "pin-cushion" style stamped frame. You will have to be careful screwing this woofer into the baffle, because you will warp the frame easily. I can overlook the poor frame because it's a great performer in other areas. Excellent value. Tested June 2007.

HiVi B3S
	Cost: $12 Usability: Build Quality: Consistency: Value:	Comments: Pretty good midrange performance, especially considering the price. Very smooth response, with a minor 8kHz breakup. Below 130hz, bass turns to thick mud. Do Not run this speaker without some sort of subwoofer crossover, preferably active at 150hz LR4. You might be able to cross at 100hz LR4 if you can trade a little distortion and output for subwoofer localization. This driver can run without a tweeter, but will sound better with a notch filter and a small amount of baffle step compensation. Cheap stamped frame, no voice coil venting. Widely available at many vendors. Tested June 2006.

HiVi B1S
	Cost: $5 Usability: Build Quality: Consistency: Value:	Comments: This is a very different driver. Much smaller than the average tweeter, but clearly designed to be used lower in frequency and at lower levels. As such, I've supplied a harmonic distortion curve here, taken at a level 10dB lower than normal. The rear chamber for this is critical, and must be shaped as described here for the best effect: drill a 1-1/4" hole through 3/4" MDF. Then round over the back side with a 1/2" roundover bit. Finally, densly stuff that area with Acousti-stuf and glue another board over it to seal, while allowing holes for the wires to pass though. It took experimentation to get this response, and without it the response curve was terrible. Tested January 2007.

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Small Driver Comparison

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