Prices and availability updated 12/14/2008. Drivers sorted by cost, (ea) followed by commentary: Scan-Speak 7000 ($398) - This driver is essentially the high end version of the XT25. Performance is indeed a small step up in all areas. Build quality is top notch with a thick metal flange that will never warp. Unfortunately, the price is ridiculous and value is low. Tested March 2008. Seas Crescendo ($336) - Seas new flagship tweeter, very expensive. Great build quality and looks, visually matching the Nextel painted woofers. While it does perform a little better than the Millenium, it's still merely average in linear and non-linear distortion, and the price is ridiculous. Tested February 2007. Scan-Speak 7100 ($285) - One of the ultra-high end tweeters from Scan-Speak, one step down in price from the 7000 ring radiator. Externally, the dome is similar to the 6600, but there are some differences in the damping coating and former, along with a different magnet structure and venting. A little more sensitive than the 6600. Very clean low end, and low harmonic distortion everywhere. A little ragged response in the top octave, but overall great performance. Note: this is the -01 version. Tested February 2007. Accuton C23-6 ($262) - Very expensive ceramic dome tweeter. Slightly ragged response and related energy storage issue at 4kHz. Mild top octave droop. Excellent 2nd order HD. Exceptional tall order HD above 3Khz, but high 3rd order HD below. If you can fix the response curve in the crossover, this is generally a good tweeter. There are better in this group however, and for less money. Tested September 2005. Seas Millennium ($224) - The definitive and popular high end tweeter. Decent 2nd order HD, disappointing 3rd order HD. Near perfect response curve. Physically well built with a distinctive and recognisable copper ring. Heavy, thick flange. Note that some folks have mentioned a peak in response at 12kHz. Not on mine however. Tested April 2005. Scan-Speak 6600 ($220) - Also known as the "AirCirc" from it's unique magnet and rear chamber design. This tweeter very low non-linear distortion. It takes a few design elements from the XT25 and improves on a few things. Low end distortion is better, and off axis response is closer to normal for a 1" dome. The only negatives to this are a small dip in the top octave response, the high price, and some production variance over the years. Old/Other tests available. Tested May 2008. Scan-Speak 602010 ($199) - This is the first tweeter to be released under Scan Speak's Illuminator line. It is a small flange neo magnet tweeter with a rear chamber and a very low resonance. Very wide bandwidth and very low distortion. It's obviously a close relative to the 6600. If you need a small tweeter that can cross over very low, this may be the one, though at a high price. If crossing over higher however, there may be a more suitable tweeter at a lower price. Tested November 2008. Hiquphon OW4 ($132 ea) - Similar performance to the OW1 (see below) but with a higher SPL. A peak in the F5 at 3.5k could lead to the impression of false detail. Works surprisingly low for a 3/4" dome, LR4 @ 2kHz is no problem. Tested March 2006. Scan-Speak 9500 ($132) - Slight "twin peaks" in the impedance curve and the related ragged low end rolloff. Response is very smooth otherwise. Nice distortion numbers except for a slightly high F4 at 2kHz. Decent metal faceplate. Tested April 2005. Hiquphon OW1 ($110 ea) - Popular and expensive 3/4" dome. Near perfect response curve and equally perfect off axis curve. The CSD stops on a dime. On the negative side, HD is merely average. Cleaner than the OW4 above 3kHz, but tall order HD peaking at 2kHz. Crossing over higher is better for the OW1. Tested March 2006. Seas T25CF001 ($103) - Extremely smooth response and excellent build quality. Decent harmonic distortion above 2kHz. Very good even order HD and average odd order HD. Slightly higher tall order harmonics than the best in this group. Slightly expensive for what you get. Tested April 2006. Seas 27TTFNCGW ($89) - This is a titanium dome tweeter with a ring neo magnet, rather than the more common slug magnet in most neo tweeters. The rear chamber is extruded aluminum that doubles as a heat sink. Performance is good but not compared to the cheaper standard 27 series. There is a shelf in the response between 2 and 3kHz likely due to an internal reflection from the back of the chamber, and harmonic distortion is a bit higher than the 27TBFCG. Tested July 2007. Peerless 810921 ($78) - Also known as the new HDS tweeter. Peerless finally creates a world class tweeter to compete with the best from Seas and Scan-Speak. Very low distortion levels and smooth, controllable response. Minor FR dip at 6.5kHz. Beautiful cast metal frame. Reasonable price. There's not much to complain about here and this is one of the best in the group. Tested June 2006. Seas 27TBCDGB-DXT ($52) - A unique small waveguide version of the respected 27TBFCG tweeter. No ferrofluid results in a slightly ragged and peaky impedance curve. Distortion is low and response is smooth. 15 and 30 degree off axis response is impressive. While I could hope for a larger waveguide version, this is an excellent tweeter. Off axis response curves available. Tested March 2008. SB Acoustics SB29RDC ($50) - Smooth response and low distortion - there's not a lot to complain about, even considering the price. It is a form of ring radiator, and it's no surprise that performance is quite a bit like a Vifa XT25, but the SB is cleaner on the low end. It does not have as much 3.5 kHz cliff in the response as it's cheaper brother. There are a few tweeters that perform a tiny bit better but cost a lot more. Tested March 2009 Dayton RS28A4 ($49) - An Usher tweeter custom made for Parts Express. Ruler flat frequency response from 1 to 12kHz with a 5dB dip at 17kHz. Excellent CSD, Highish F3 HD below 2 kHz. Good HD above 2kHz. Nice build quality and metal faceplate. I've tested many of these, and there was a consistency problem. Started shipping without ferrofluid at some point, Old/Other tests available. Tested October 2008. Seas 29TAFW ($49) - This is the metal dome counterpart to the 29TFFW below. Similar performance though slightly cleaner HD and a bit more frequency response variance in the top octave. More extended and clean low end make this suitable for low or shallow crossover usage. Nice mid priced tweeter. Tested December 2007. Vifa XT25 ($48) - Smoothest and most extended response curve in the group, and resulting CSD is excellent. Good tall order HD above 2kHx, but average 2nd order HD. Poor HD levels of all types below 2kHz, even considering the extended low end. It may have a 500 Hz Fs, but don't think about crossing it below 2kHz LR4 or 2.5kHz LR2. Off axis response curves available. Tested January 2006. Seas 29TFFW ($49) - Highish Fs, steep low end rolloff. Smooth response with 2dB droop on top end. Good CSD. Average 2nd order HD, increasing 3rd order at 1.2kHz. Best crossed over LR4 1.5kHz or above. Nice thick flange design. Very efficient. Tested August 2005. Seas 27TBFCG ($43) - Very smooth response, down a few dB at 20kHz. Very low distortion of all types, particularly the near non-existant high order harmonics. No notable energy storage problems. Ultrasonic breakup node at 26.5Khz. The hexagrid cover is ugly. Off axis response curves available. Tested April 2005. Seas 27TDFC ($40) - Exactly the same as the TBFCG, but with a fabric dome. Slightly rising top end response but overall very smooth. No ugly hexagrid. Similar to the old 27TFFC, but with a polymer surround and slightly cleaner performance. Tested April 2005. Vifa D26NC55 ($37) - Very smooth response with mild tilt down of a couple dB over it's range. Near perfect CSD without no high frequency garbage. *Very* low HD above 2.5kHz with a mild 3rd order peak at 1.6kHz. Almost a complete lack of tall order HD products. Well built small flange neo with heat sink and excellent internal construction. Off axis response curves available. Old/Other tests available. Tested December 2007. Seas 22TAFG ($34) - Very smooth response with 3dB rise at 20Khz which is flat when 15 deg off axis. Breakup node at a very high frequency. Average Fs for a 3/4" in this class. High HD below 2kHz, best if crossed over 2.5kHz LR4 or 3kHz LR2. Another ugly hexagrid cover. Tested August 2005. Seas 27TDF ($33) - Near flat line response through this tweeter's entire bandwidth. Similar to the "C" verion but slightly cheaper and without the rear chamber. Without the chamber, this tweeter has more ouput between 1 and 2kHz, a higher Fs and a higher Qts, but can operate just as low with a crossover that deals with the sharper impedance peak. Tested November 2008. Vifa XT25SC50 ($33) - Smooth response except for a mild peak at 4kHz with a small bit of ringing in the CSD. Decent harmonic distortion performance for neo tweeters in this group. Recommend 2.5kHz LR4 0r 3kHz LR2 xover points. Performs well but not equal to it's larger brother. Tested April 2006. Morel MDT20 ($33) - (discontinued) Poor 2nd order harmonic distortion and a ragged response curve in the top two octaves. Regardless, this would still sound pretty good crossed at LR4 2khz or higher. High intermodulation distortion. (not shown) Tested April 2005. Seas 27TAFNCG ($32) - Smooth response with a mild Qts bump at the bottom. Multi-chamber neo magnet allows lower Fs than many other neo tweeters. Good but not great HD, but should have no problem crossing over at 2kHz. Small front/surface mount design. Tested May 2006. Seas 27TFFNCG ($32) - Smooth response with a mild Qts bump at the bottom. Mild response droop above 15kHz. Essentially the same as the aluminim dome version above, but with a fabric dome and a hexagrid cover. Small front/surface mount design. Tested March 2007. Seas 27TFFNC-CG ($32) - The tweeter is exactly the same as the 27TFFNCG, but with a flange that is a copy of the popular D26NC55. This Seas is a decent tweeter, but the Vifa is generally a better performer. Tested March 2008. Vifa DX25 ($31) - Smooth and extended response at both ends with mild 3dB depression in the whole top octave. Low Fs for a tweeter with no rear chamber. Good CSD. Excellent 2nd order HD above 1.8kHz, very bad 2nd order HD below 1Khz. Cross over 1.8kHz LR4 or 2.5kHz LR2. Very efficient with high power handling. Tested August 2005. Vifa D27SG15 ($28) - (discontinued) Shielded full size tweeter in the bunch. Relatively smooth and extended response. Small 3rd order HD peak at 1.6kHz. Rising 2nd order HD below 1.5khz. Cross over steep to avoid these issues. Slightly high 3rd order HD at 5kHz, bordeline audible. D27TG05 and D27TG15 perform identically. Tested April 2005. Seas 25TFFN ($27) - Strange tweeter. Drooping response at both ends but smooth. Decent, but high 3rd order HD limits crossover point to anywhere above 4kHz. Shaped kind of like the old cheap Audax polymers. Can be surface mounted with no ill effects. Tested April 2005. SB Acoustics SB25STC ($25) - This is a low cost tweeter with excellent build quality but a few issues that prevent it from being the best at this price. Harmonic distortion is good but not great, and the response curve is rough with internal reflections causing an issue at 3.5 kHz. Tested March 2008. Tangband 25-1414 ($24) - (discontinued) Performs almost the same as the cheaper fabric 25-1166 version listed below, with the same 10kHz depression, slightly below average HD performance and a little more sensitivity. Tested February 2007. Dayton DC28F-8 ($20) - The popular "silkie" returns with a redsign and hopefully some consistency. Response is relatively smooth but harmonic distortion is average to poor. It will work crossed LR4 at 2kHz or higher. Not the best value in the under $20 range. Only 3 screws on a flange this big is a bad idea. Tested February 2006. Dayton ND28F ($19) - This is a nice performing small flange neo tweeter. The harmonic distortion is relatively clean for this price range and the tweeter should be able to handle 2 kHz LR4 at reasonable levels. Sensitivity is low. The response curve looks good except for a high Qts low end bump that will need to be addressed in the crossover. Tested December 2007. Tangband 25-1166 ($19) - Relatively smooth low end rolloff for a neo tweeter. High F3 and F5 limit use down to 3Khz with a steep crossover. Slightly drooping response around 10kHz probably contributes to a laid back sound. Sticky coating = a furry dust covered dome in a year. Tested April 2005. North D2506-S ($18) - (discontinued) High value tweeter with relatively good performance for the price. Sold in "matched pairs" a point which is of questionable value. Can easily cross over as low as 1600 Hz LR4. Ovarall, one of the best at this price point. Tested March 2006. Hi-Vi TN28 ($17) - Bonus points for a neat looking top mount design. Minus points for energy storage at 8kHz. Tested in a typical configuration on top of an enclosure. High F5 at 1.6kHz will melt your ears if crossed over too low. Poor performer overall. Vifa DQ25SC16-04 ($16) - A very nice performing low cost tweeter. In fact it's only downfall is a slightly rough top end that's not likely to be audible. Very clean operation on the low end, particularly for a small neo tweeter. It's a value leader in this price range. Tested May 2008. Hi-Vi SD1.1 ($13) - "A" version tested. Nice performance for a tweeter of this price, and probably worth the few bucks more than the K1, but there are some consistency issues. Twin impedance peaks cause a slightly bumpy low end that smoothes out in box with typical baffle diffraction peaking. Slight rise in the top octave goes to flat a few degrees off axis. Make sure you have the shiny dome shown on the right. The dull one on the left measures horribly. Old/Other tests available. Tested February 2007. Vifa BC25SC06-04 ($12) - This is a low cost fabric dome tweeter with mild horn loading. Very nice harmonic distortion but a mild internal reflection causes a hiccup in the response curve at 4kHz. Response is otherwise smooth. Good value. Tested May 2008. Aura NT1-204-8D ($12) - Small and inexpensive rear mount dome tweeter with pure titanium dome and a coated fabric surround. Smooth response and good harmonic distortion above 3Khz. Exact same rear mount flange as the Dayton ND20. Great value and a good mate to a small woofer or mid. Tested March 2007. Hi-Vi K1 ($12) - Smooth response. Shielded magnet, rather large 116mm flange. Low Fs for a tweeter with no rear chamber and a solid pole piece. High F5 below 2.2khz. Average to slightly high IMD. (not shown) Cross LR4 @ 2.2kHz or LR2 @ 3kHz for best results. Decent performer in a garbage price range. Tested September 2005. Goldwood GT-525 ($10) - This is a horrible tweeter on all counts, just stay away. It has a ragged low end response and piercing harmonic distortion. Low build quality tops it off. Tested April 2008. Goldwood GT-520 ($10) - This appears to be a horn loaded version of the GT-525. Harmonic distortion is improved over the 520, but now the response curve is completely unworkable. Poor performance overall. Tested April 2008. Hi-Vi X1R ($9) - Worst performing tweeter in this group. I have to wonder if they were somehow defective, but my two samples measured the same... then went in the garbage. A dome material that's too light and flexible plus ferrofluid that's too thick = no impedance peak and horrible distortion. Tested February 2007. Hi-Vi TN25 ($9) - This is a neo magnet tweeter with a rear chamber. Flow restriction between the chambers causes two impedance peaks and a dip at 500 Hz. Harmonic distortion is generally too high across the board, and there are cleaner options in the price range. Tested April 2008. Dayton ND20FB ($8) - Very smooth, usable response. Nifty rear mount design. Good distortion performance above 3.5kHz. Super small and super cheap but definitely usable. Note that this "F" version has ferrofluid. Old/Other tests available. Off axis response curves available. Tested April 2008. Dayton ND20FA ($8) - Like above, but front mount press fit. Slightly different dome material and slightly more peaking on the top end. Tested surface mounted, a likely installation for this tweeter. Note that this "F" version has ferrofluid. Old/Other tests available. Tested June 2008. Dayton ND16FA ($8) - Very nice "super-mini" dome 5/8" diameter. Press fits into an easily drilled 1-1/4" hole. Works well from 3500 Hz and up, making it a possible mate with small woofers or mids. Big value for small dollars. Tested February 2007. Hi-Vi T20-8 ($5) - The cheapest tweeter in this test is worth the money with some limitations. The top octave response is rough but good enough. A smooth low end makes for an easy crossover but harmonic distortion limits useful low end range to 4 kHz. Off axis response curves available. Tested April 2008. Hi-Vi T20-4 ($5) - 4 ohm version of the T20 above. Very similar, but 3 dB more sensitivity and a DCR of 3.3 ohms. Tested May 2008.