Log in
Register
Home
Forums
New posts
Search forums
What's new
New posts
New profile posts
Latest activity
News
Members
Current visitors
New profile posts
Search profile posts
Features
Log in
Register
Search
Search titles only
By:
Search titles only
By:
New posts
Search forums
Menu
Install the app
Install
Reply to thread
Home
Forums
Pro Audio
Varsity
High Frequency Compression Driver Evaluation
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Message
<blockquote data-quote="Art Welter" data-source="post: 51266" data-attributes="member: 52"><p>Re: High Frequency Compression Driver Evaluation</p><p></p><p><strong>The Facts:</strong></p><p></p><p>All the drivers tested are nominally rated as 16 ohm. “DCR” was the DC resistance measured (in ohms), for relative comparison. Sorry for the run on mess, tabs (and more than single spaces in a line) vanish after editing.</p><p></p><p>Driver name, Test name, AES, Peak, Rated Range, Exit, Diaphragm, DCR, Angle, Lb.</p><p>BMS 4550, 50, 80, 450, 500-20 kHz, 1”, 1.75”, Polyester, 12.3, 12, 4.95</p><p>BMS 4552, 52, 80, 450, 500-20 kHz, 1”, 1.75”, Polyester, 12.3, 12, 1.83</p><p>BCDE82, 82, 110, 220, 500-18 kHz, 1.4”, 3”, Tit.,Polyimide 8, <1, 9.9</p><p>PSD2002, 02, 80, N/A, 1.2K-20 kHz, 1”, 2”, Titanium, 11.0, 10, 5.0</p><p>EVDH1A, 1A, 50, 200, 500-20 kHz, 1.4-2”, 3”, Titanium, 10.4, 14, 23.5</p><p>Jensen D-30, PA, 30?, ?, ?, .75”, 2.25”?, Aluminum, 11.40, <0, 2.5</p><p></p><p>The tests used Welter Systems Maltese conical expansion horns (13 x 13 degree horn angle) with adapters to fit the various compression driver exits. The narrow horn results in an on axis sensitivity around 6 dB more than most typical 90 degree horns, the 2 meter results would be similar to one meter results on some horns.</p><p>Care was taken to insure a smooth transition between driver, adapter and horns, requiring a fair amount of drilling, filing and cursing those that made poorly aligned adapters and drivers that have unique bolt patterns.</p><p>The Maltese horn exhibits increasing “ripple” (frequency response dips and peaks) below 1000 Hz, the ripple reduces to less than .25 dB by 2000 Hz, where the frequency response differences between drivers become large, in some cases over 20 dB. The low frequency ripple is less than the unit to unit driver frequency response variance.</p><p></p><p><strong>1)</strong> Size does matter regarding LF output, there is no replacement for displacement. The larger diaphragm drivers have more output below 1250 Hz, the 3” diaphragm driver’s response extending to 200 Hz. The larger diaphragms provide more output with less distortion.</p><p>The smallest driver, the BMS 4552 had the least LF, followed by the 4550, the Jensen Hypex D-30, and the Eminence PSD2002.</p><p>The EV DH1A and the B&C DE82 were neck and neck in LF response, the DE82 having slightly more output below 1000 Hz, other than the DH1A having slightly more output below 250 Hz.</p><p></p><p>The BMS drivers are only capable of low distortion output with a 630 Hz crossover frequency at a level lower than one watt. BMS makes coaxial 2” exit drivers with better LF response.</p><p>The BMS also had more IM distortion than the other drivers, around 14%.</p><p>The old Jensen half the distortion, 16%.</p><p>The inexpensive PSD2002 was a surprise, with 6 dB more power, it hit 95.7 dB at 530 Hz with 8% 2ndHD.</p><p>The B&C DE82 at +6 dB did 98.9 dB, 6% 2ndHD.</p><p>At +9 dB, 101.9 dB 7% 2ndHD, the ultra-heavyweight EV DH1A had a clear 3 dB “win”.</p><p></p><p>The distortion levels above do not include the (minimal) contributions of upper harmonics past the second, and are rounded to the nearest whole number above the actual 2ndHD. Anyone willing to crunch the numbers further is welcome to look at the RTA charts and derive finer resolution. Having done so in the past to prove the point that 3rd, 4th etc. harmonics, unless they exceed the second, change THD very little.</p><p>Odd order harmonics tend to sound worse (at least from a western musical standpoint) and there are differences in their levels between the drivers.</p><p></p><p>Harmonics of the “Mid” test, using 1046 & 1865 Hz sine wave tones occurred at 819 Hz ( IM sub harmonic component) and around 2092, 2660, 2920, 3138, 3450, 3730, 3980, 4730, 5010, 5620, 5790, 7760, 8410 Hz.</p><p>The Jensen Hypex PA30 driver, lacking a phase plug, had an additional 16 odd harmonics occur.</p><p></p><p>The BMS drivers again had the highest IM content. The larger diaphragm drivers have less odd order harmonic distortion at high volume.</p><p></p><p>Harmonics of the ”Hi” test, using 2093 & 3729 Hz tones sine wave tones occurred at 1636 Hz (IM) and around 4190, 5360, 5822, 6280, 7460, 7915, 9100, 9550, 10008, 11190, 11640, 12100, 13280, 13740, 14920, 15380, 16290, 17010 Hz.</p><p>The Jensen Hypex PA30 driver, lacking a phase plug, but having an acoustic high pass filter, had less upper harmonic distortion.</p><p>The Eminence PSD2002, which has little output above 12500 Hz, hit a slightly higher SPL than the other 1” drivers with similar distortion level.</p><p> </p><p><strong>2)</strong> The dual sine wave “mid” test using 1046 &1865 Hz came out with a different order at the bottom in a close race, the DH1a again the top driver in terms of clean output capability.</p><p>02dsMid+3 104 dB, 7% 2ndHD</p><p>PAdsMid+6 104 dB, 7% 2ndHD</p><p>52dsMid+3 104.8 dB, 10 % 2ndHD</p><p>50dsMid+3 105.7 dB, 8 % 2ndHD</p><p>82dsMid+3 106.6 dB, 6% 2ndHD </p><p>1AdsMid+9 112.1 dB, 10% 2ndHD</p><p></p><p><strong>3)</strong> The “Hi” test using 2093 & 3729 Hz resulted in less disparity between the drivers, the EV still had the most output:</p><p>PAdsHi 106.4 dB <4 % 2ndHD</p><p>02dsHi+6 108.4 dB, 4% 2ndHD </p><p>52dsHi 110.3 dB, < 6% 2ndHD</p><p>50dsHi 110.7 dB, 6% 2ndHD </p><p>82dsHi+6 111.1 dB, 5% 2ndHD</p><p>1AdsHi+3 112.9 dB, < 6% 2ndHD</p><p></p><p><strong>4)</strong> The B&C DE82 had the flattest response, +/- 3 dB from 644 to 5000 hz, with a peaked rising response above. The BMS and EV drivers have more output in the 1600 to 8000 Hz range. </p><p>The Eminence PSD2002 has a rough response, and little output above 12.5 kHz.</p><p>The Jensen Hypex rolls off at 2500 Hz, with a shelved upper response, more explanation in it’s test section below.</p><p></p><p><strong>5)</strong> Compression drivers “compress” the output of a relatively large diaphragm in to a much smaller throat volume, a 3” diaphragm with a 1.4” exit at minimum has a 4.55/1 compression ratio, ratios as high as 10/1 are common. This compression results in high throat SPL, at the upper power levels the drivers were tested at the non- linearity of air is responsible for a significant (though undetermined percentage) of the of distortion measured, that non- linear distortion is unavoidable in any compression driver design.</p><p>With approximately one watt of input, the B&C DE82 measures 110 dBA at 2 meters, that level results in 143.7 dBA at the bug screen, still one inch from the throat. Using a conservative value of 20 dB above that level (well within the AES power rating) throat SPL will reach a level of 168 dB SPL.</p><p>I have not measured any closer than the bug screen, one other fact found during testing is pebbles and dust contain enough ferrous material to stick to the driver’s magnets, requiring cleaning with sticky tape to remove. Removal of the bug screen would be an invitation to introduce magnetically attracted “trash” in the gap.</p><p>Examples of air non-linearity introduced by the mixing of two ultrasonic tones at 104 dB SPL are available in posts #179 #182 of:</p><p> <a href="http://www.diyaudio.com/forums/multi-way/210914-what-benefits-adding-hf-driver-7khz-up-18.html" target="_blank">What are benefits of adding HF driver 7khz up? - Page 18 - diyAudio</a></p><p></p><p><strong>Opinions:</strong></p><p>Considering the disparity between size, weight, diaphragm material, and design, the constraints and compromises inherent in each approach, once equalized for flat on-axis response there was surprisingly little difference in the end results of listening tests.</p><p>The dual sine wave tests made hearing the differences between the drivers easiest, simply stated, the EV DH1A has more output available with less audible distortion than the other drivers. The B&C DE82, also using a 3” diaphragm, was the next choice in terms of output vs. distortion.</p><p></p><p>The 3” diaphragm drivers had large advantage in terms of low frequency output, they also had close to a 3 dB advantage in terms of HF output. </p><p>Though the BMS drivers were more sensitive in high frequency output, the smaller diaphragms and throats “run out of gas” about 3 dB SPL before the larger diaphragms. </p><p>The Eminence PSD 2002 wins the low end 1” competition, the BMS the mid -high.</p><p>I expect opinions to vary widely on this, the low end distortion in the BMS may be construed as “warmth”, and although the PSD2002, has more undistorted LF, when pushed hard sounds more “grindy” compared to the BMS.</p><p>The Jensen Hypex, once equalized, sounded surprisingly good considering it’s abysmal raw response.</p><p></p><p>With a music playback, when pushed hard, even with a 1250 crossover, the "s" sounds in the word “cities” seemed to get the most “spitty” with the BMS drivers, and the harmonics of the flute seemed a bit odd. The BMS drivers have the smallest diaphragms of the drivers tested, whether this type of distortion is simply the result of the higher throat SPL required by the smaller diaphragm and exit diameter, or the driver design itself is an unanswered question.</p><p></p><p>The upward masking from lower frequencies crossover masks those distortion effects to a large degree.</p><p></p><p>While recording I only listened to the HF output, what I heard often reminded me of distorted screams heard in “B” grade horror movies, I was surprised to find how much distortion can be tolerated in the presence of the low frequency output.</p><p></p><p><strong>Conclusions:</strong></p><p>All of the drivers tested showed many desirable characteristics and some defects.</p><p></p><p>The Jensen Hypex is an antique, no longer available except on the used market. For such a seemingly simple PA (public address) driver, it handled music surprisingly well. Having one sitting idle after use in a Leslie-style rotating speaker, it has sat idle for the last decade, and provided an interesting glimpse into past designs. I had assumed from it’s rolled off upper response it used a phenolic diaphragm as most thread on PA drivers, finding it used an aluminum diaphragm was a surprise.</p><p></p><p>The Eminence PSD2002, the cheapest driver of the bunch, had far more undistorted lower frequency output than the other one inch exit drivers, though upper response was lacking, and more “heroic” equalization was required throughout it’s operating range. The PSD2002 is used as an OEM driver by many manufacturers, it provides fairly bulletproof operation. Having owned many of these drivers, have found unit to unit consistency to be quite poor, the driver tested was the best of four units I still own. </p><p></p><p>The BMS 1” drivers have extended clean HF response, but require fairly high crossover points if high volume, low distortion response is desired. The BMS 4552 is by far the highest output for size and weight of the drivers tested. The small size lends itself to line array applications, the close driver spacing reducing the complexity of the driver/wave guide interface. In quantity, it is also a great choice for combating HF air attenuation, sixty four units have been coupled to single horns using Tom Danley’s layered combiner. They have a “classic” HF driver response that would work well with many “old school” horns, yet have upper HF response extending above human audibility.</p><p></p><p>The B&C DE82 has most all the elements I look for in a compression driver: low distortion, extended bandwidth, high output capability, relatively low weight and cost. It was not the most efficient driver, but was the flattest overall, and appears to handle the extra power it requires over the others with no problems. The only small complaint are some response glitches at the very top end of it’s response, BMS makes other drivers that (other than price) address those small HF issues.</p><p></p><p>I was hoping to find a lighter weight replacement with sound quality exceeding the Electro-Voice DH1A, but in this series of tests it simply was the best sounding driver in every metric I can think of: low distortion, extended bandwidth, high output capability, and durability with prolonged unit to unit consistency.</p><p></p><p>It appears to me that although LF transducer technology has made some definite improvements in the past decades, HF driver design constraints have limited improvements to voice coil and diaphragm survivability and lighter weight.</p><p></p><p>Of course, if any manufacturer’s would like to send me pairs of free compression driver production samples to evaluate, I’ll be happy to re-evaluate my last conclusion upon finding a driver with better overall performance than the EV DH1A or DH1AMT.</p><p>Until then the ten DH1AMT and single DH1A drivers I own will remain in their present cabinets.</p><p></p><p></p><p>Since as a professional in the audio feild you probably care far more about the performance of a driver when pushed hard, several examples will be posted.</p><p></p><p>The musical recordings include the output of the high frequency horn only, a full range mix of the same files are available, recorded at the same and lower levels down to just under a watt:</p><p><a href="http://www.diyaudio.com/forums/multi-way/212240-high-frequency-compression-driver-evaluation.html" target="_blank">High Frequency Compression Driver Evaluation - diyAudio</a></p><p></p><p>1A = EVDH1A</p><p>02= Eminence PSD2002</p><p>50= BMS 4550</p><p>52= BMS 4552</p><p>82= B&C DE82</p><p>“DRPA630HiOutOnly” is a recording of the DSP HF output driven by a Phillips CD player.</p><p>The recordings below are an excerpt from Ed Kabotie’s song, “7 Cities of Gold” </p><p><a href="http://dreamcatcher.com/ed-kabotie-freedom-songs.html" target="_blank">Ed Kabotie Freedom Songs - DreamCatcher.com</a></p><p>with voice, acoustic guitar and wood flute used to compare the output of the various HF drivers all fitted to the same type horn.</p><p> </p><p>The drivers were equalized as flat as possible from 630 to 16K using the three PEQ and 1/3 octave filters afforded by the DBX DriveRack PA. Each driver also used a specific delay compensation to align it with the LF track, slightly different delay and EQ were required for the 1250 Hz alignment.</p><p>The process was akin to aligning a dozen different PA systems, no small feat in itself.</p><p>The process “babied” the 1” drivers, allowing for the LF track to carry some extra “weight” around the 630 Hz crossover point. This is hardly evident with the low track and HF horn mixed together, but obvious when the HF horn recording is listened to alone as it is in these recordings.</p><p></p><p>The actual SPL and power levels for the recordings are:</p><p></p><p>1An0630 0, 630 Hz (7.3 watts, 116.7 dBA peak) </p><p>1Ap1363 +13, 630 Hz ( 146 watts, 128.9 dBA peak) </p><p>1Ap1763 +17, 630 Hz (367 watts, 132.4 dBA peak, oops) </p><p>1Ap1312 +13, 1250 Hz (73 watts, 127.8 dBA peak)</p><p></p><p>02n0630 0, 630 Hz (7.3 watts, 110.3 dBA peak) </p><p>02p0125 0, 1250 Hz ( 11.5 watts 113.8 dBA peak) </p><p>02p10125 +10, 1250 Hz (115 watts 118.9 dBA peak) </p><p>02p15 125 +15, 1250 Hz (367 watts 125.8 dBA peak, oops)</p><p></p><p>50n0630 0, 630 Hz (7.3 watts, 114 dBA peak) </p><p>50p13125 +13, dBA 1250 Hz (36.6 watts, 125.5 dBA peak)</p><p></p><p>52n0630 0, 630 Hz (7.3 watts, 116.3 dBA peak) </p><p>52p13125 +13, 1250 Hz( 36.6 watts 124.6 dBA peak)</p><p></p><p>82n0630 0, dBA 630 Hz (7.3 watt 113.2 dBA peak)</p><p>82p1363 +13, 630 Hz (146 watts 126.3 dBA peak)</p><p>82p1312 +13, 1250 Hz (73 watts 121.6 peak)</p><p></p><p>Not wanting to run the risk of burning up this antique driver, it was given less power:</p><p>PAp363 +3, dBA 630 Hz ( 14.6 watts 96.3 dBA peak)</p><p>PAp912 +9, dBA 1250 Hz (46 watts, 99.5 dBA peak)</p><p></p><p><strong>The files are in mp3 format, to open them change the suffix < .pdf > to <.mp3 > they will open with your mp3 app.</strong></p><p></p><p>Hope you find the recordings interesting, they offer an insight in compression driver comparison (as far as I know) never undertaken before this study.</p><p></p><p>Art Welter</p></blockquote><p></p>
[QUOTE="Art Welter, post: 51266, member: 52"] Re: High Frequency Compression Driver Evaluation [B]The Facts:[/B] All the drivers tested are nominally rated as 16 ohm. “DCR” was the DC resistance measured (in ohms), for relative comparison. Sorry for the run on mess, tabs (and more than single spaces in a line) vanish after editing. Driver name, Test name, AES, Peak, Rated Range, Exit, Diaphragm, DCR, Angle, Lb. BMS 4550, 50, 80, 450, 500-20 kHz, 1”, 1.75”, Polyester, 12.3, 12, 4.95 BMS 4552, 52, 80, 450, 500-20 kHz, 1”, 1.75”, Polyester, 12.3, 12, 1.83 BCDE82, 82, 110, 220, 500-18 kHz, 1.4”, 3”, Tit.,Polyimide 8, <1, 9.9 PSD2002, 02, 80, N/A, 1.2K-20 kHz, 1”, 2”, Titanium, 11.0, 10, 5.0 EVDH1A, 1A, 50, 200, 500-20 kHz, 1.4-2”, 3”, Titanium, 10.4, 14, 23.5 Jensen D-30, PA, 30?, ?, ?, .75”, 2.25”?, Aluminum, 11.40, <0, 2.5 The tests used Welter Systems Maltese conical expansion horns (13 x 13 degree horn angle) with adapters to fit the various compression driver exits. The narrow horn results in an on axis sensitivity around 6 dB more than most typical 90 degree horns, the 2 meter results would be similar to one meter results on some horns. Care was taken to insure a smooth transition between driver, adapter and horns, requiring a fair amount of drilling, filing and cursing those that made poorly aligned adapters and drivers that have unique bolt patterns. The Maltese horn exhibits increasing “ripple” (frequency response dips and peaks) below 1000 Hz, the ripple reduces to less than .25 dB by 2000 Hz, where the frequency response differences between drivers become large, in some cases over 20 dB. The low frequency ripple is less than the unit to unit driver frequency response variance. [B]1)[/B] Size does matter regarding LF output, there is no replacement for displacement. The larger diaphragm drivers have more output below 1250 Hz, the 3” diaphragm driver’s response extending to 200 Hz. The larger diaphragms provide more output with less distortion. The smallest driver, the BMS 4552 had the least LF, followed by the 4550, the Jensen Hypex D-30, and the Eminence PSD2002. The EV DH1A and the B&C DE82 were neck and neck in LF response, the DE82 having slightly more output below 1000 Hz, other than the DH1A having slightly more output below 250 Hz. The BMS drivers are only capable of low distortion output with a 630 Hz crossover frequency at a level lower than one watt. BMS makes coaxial 2” exit drivers with better LF response. The BMS also had more IM distortion than the other drivers, around 14%. The old Jensen half the distortion, 16%. The inexpensive PSD2002 was a surprise, with 6 dB more power, it hit 95.7 dB at 530 Hz with 8% 2ndHD. The B&C DE82 at +6 dB did 98.9 dB, 6% 2ndHD. At +9 dB, 101.9 dB 7% 2ndHD, the ultra-heavyweight EV DH1A had a clear 3 dB “win”. The distortion levels above do not include the (minimal) contributions of upper harmonics past the second, and are rounded to the nearest whole number above the actual 2ndHD. Anyone willing to crunch the numbers further is welcome to look at the RTA charts and derive finer resolution. Having done so in the past to prove the point that 3rd, 4th etc. harmonics, unless they exceed the second, change THD very little. Odd order harmonics tend to sound worse (at least from a western musical standpoint) and there are differences in their levels between the drivers. Harmonics of the “Mid” test, using 1046 & 1865 Hz sine wave tones occurred at 819 Hz ( IM sub harmonic component) and around 2092, 2660, 2920, 3138, 3450, 3730, 3980, 4730, 5010, 5620, 5790, 7760, 8410 Hz. The Jensen Hypex PA30 driver, lacking a phase plug, had an additional 16 odd harmonics occur. The BMS drivers again had the highest IM content. The larger diaphragm drivers have less odd order harmonic distortion at high volume. Harmonics of the ”Hi” test, using 2093 & 3729 Hz tones sine wave tones occurred at 1636 Hz (IM) and around 4190, 5360, 5822, 6280, 7460, 7915, 9100, 9550, 10008, 11190, 11640, 12100, 13280, 13740, 14920, 15380, 16290, 17010 Hz. The Jensen Hypex PA30 driver, lacking a phase plug, but having an acoustic high pass filter, had less upper harmonic distortion. The Eminence PSD2002, which has little output above 12500 Hz, hit a slightly higher SPL than the other 1” drivers with similar distortion level. [B]2)[/B] The dual sine wave “mid” test using 1046 &1865 Hz came out with a different order at the bottom in a close race, the DH1a again the top driver in terms of clean output capability. 02dsMid+3 104 dB, 7% 2ndHD PAdsMid+6 104 dB, 7% 2ndHD 52dsMid+3 104.8 dB, 10 % 2ndHD 50dsMid+3 105.7 dB, 8 % 2ndHD 82dsMid+3 106.6 dB, 6% 2ndHD 1AdsMid+9 112.1 dB, 10% 2ndHD [B]3)[/B] The “Hi” test using 2093 & 3729 Hz resulted in less disparity between the drivers, the EV still had the most output: PAdsHi 106.4 dB <4 % 2ndHD 02dsHi+6 108.4 dB, 4% 2ndHD 52dsHi 110.3 dB, < 6% 2ndHD 50dsHi 110.7 dB, 6% 2ndHD 82dsHi+6 111.1 dB, 5% 2ndHD 1AdsHi+3 112.9 dB, < 6% 2ndHD [B]4)[/B] The B&C DE82 had the flattest response, +/- 3 dB from 644 to 5000 hz, with a peaked rising response above. The BMS and EV drivers have more output in the 1600 to 8000 Hz range. The Eminence PSD2002 has a rough response, and little output above 12.5 kHz. The Jensen Hypex rolls off at 2500 Hz, with a shelved upper response, more explanation in it’s test section below. [B]5)[/B] Compression drivers “compress” the output of a relatively large diaphragm in to a much smaller throat volume, a 3” diaphragm with a 1.4” exit at minimum has a 4.55/1 compression ratio, ratios as high as 10/1 are common. This compression results in high throat SPL, at the upper power levels the drivers were tested at the non- linearity of air is responsible for a significant (though undetermined percentage) of the of distortion measured, that non- linear distortion is unavoidable in any compression driver design. With approximately one watt of input, the B&C DE82 measures 110 dBA at 2 meters, that level results in 143.7 dBA at the bug screen, still one inch from the throat. Using a conservative value of 20 dB above that level (well within the AES power rating) throat SPL will reach a level of 168 dB SPL. I have not measured any closer than the bug screen, one other fact found during testing is pebbles and dust contain enough ferrous material to stick to the driver’s magnets, requiring cleaning with sticky tape to remove. Removal of the bug screen would be an invitation to introduce magnetically attracted “trash” in the gap. Examples of air non-linearity introduced by the mixing of two ultrasonic tones at 104 dB SPL are available in posts #179 #182 of: [URL="http://www.diyaudio.com/forums/multi-way/210914-what-benefits-adding-hf-driver-7khz-up-18.html"]What are benefits of adding HF driver 7khz up? - Page 18 - diyAudio[/URL] [B]Opinions:[/B] Considering the disparity between size, weight, diaphragm material, and design, the constraints and compromises inherent in each approach, once equalized for flat on-axis response there was surprisingly little difference in the end results of listening tests. The dual sine wave tests made hearing the differences between the drivers easiest, simply stated, the EV DH1A has more output available with less audible distortion than the other drivers. The B&C DE82, also using a 3” diaphragm, was the next choice in terms of output vs. distortion. The 3” diaphragm drivers had large advantage in terms of low frequency output, they also had close to a 3 dB advantage in terms of HF output. Though the BMS drivers were more sensitive in high frequency output, the smaller diaphragms and throats “run out of gas” about 3 dB SPL before the larger diaphragms. The Eminence PSD 2002 wins the low end 1” competition, the BMS the mid -high. I expect opinions to vary widely on this, the low end distortion in the BMS may be construed as “warmth”, and although the PSD2002, has more undistorted LF, when pushed hard sounds more “grindy” compared to the BMS. The Jensen Hypex, once equalized, sounded surprisingly good considering it’s abysmal raw response. With a music playback, when pushed hard, even with a 1250 crossover, the "s" sounds in the word “cities” seemed to get the most “spitty” with the BMS drivers, and the harmonics of the flute seemed a bit odd. The BMS drivers have the smallest diaphragms of the drivers tested, whether this type of distortion is simply the result of the higher throat SPL required by the smaller diaphragm and exit diameter, or the driver design itself is an unanswered question. The upward masking from lower frequencies crossover masks those distortion effects to a large degree. While recording I only listened to the HF output, what I heard often reminded me of distorted screams heard in “B” grade horror movies, I was surprised to find how much distortion can be tolerated in the presence of the low frequency output. [B]Conclusions:[/B] All of the drivers tested showed many desirable characteristics and some defects. The Jensen Hypex is an antique, no longer available except on the used market. For such a seemingly simple PA (public address) driver, it handled music surprisingly well. Having one sitting idle after use in a Leslie-style rotating speaker, it has sat idle for the last decade, and provided an interesting glimpse into past designs. I had assumed from it’s rolled off upper response it used a phenolic diaphragm as most thread on PA drivers, finding it used an aluminum diaphragm was a surprise. The Eminence PSD2002, the cheapest driver of the bunch, had far more undistorted lower frequency output than the other one inch exit drivers, though upper response was lacking, and more “heroic” equalization was required throughout it’s operating range. The PSD2002 is used as an OEM driver by many manufacturers, it provides fairly bulletproof operation. Having owned many of these drivers, have found unit to unit consistency to be quite poor, the driver tested was the best of four units I still own. The BMS 1” drivers have extended clean HF response, but require fairly high crossover points if high volume, low distortion response is desired. The BMS 4552 is by far the highest output for size and weight of the drivers tested. The small size lends itself to line array applications, the close driver spacing reducing the complexity of the driver/wave guide interface. In quantity, it is also a great choice for combating HF air attenuation, sixty four units have been coupled to single horns using Tom Danley’s layered combiner. They have a “classic” HF driver response that would work well with many “old school” horns, yet have upper HF response extending above human audibility. The B&C DE82 has most all the elements I look for in a compression driver: low distortion, extended bandwidth, high output capability, relatively low weight and cost. It was not the most efficient driver, but was the flattest overall, and appears to handle the extra power it requires over the others with no problems. The only small complaint are some response glitches at the very top end of it’s response, BMS makes other drivers that (other than price) address those small HF issues. I was hoping to find a lighter weight replacement with sound quality exceeding the Electro-Voice DH1A, but in this series of tests it simply was the best sounding driver in every metric I can think of: low distortion, extended bandwidth, high output capability, and durability with prolonged unit to unit consistency. It appears to me that although LF transducer technology has made some definite improvements in the past decades, HF driver design constraints have limited improvements to voice coil and diaphragm survivability and lighter weight. Of course, if any manufacturer’s would like to send me pairs of free compression driver production samples to evaluate, I’ll be happy to re-evaluate my last conclusion upon finding a driver with better overall performance than the EV DH1A or DH1AMT. Until then the ten DH1AMT and single DH1A drivers I own will remain in their present cabinets. Since as a professional in the audio feild you probably care far more about the performance of a driver when pushed hard, several examples will be posted. The musical recordings include the output of the high frequency horn only, a full range mix of the same files are available, recorded at the same and lower levels down to just under a watt: [URL="http://www.diyaudio.com/forums/multi-way/212240-high-frequency-compression-driver-evaluation.html"]High Frequency Compression Driver Evaluation - diyAudio[/URL] 1A = EVDH1A 02= Eminence PSD2002 50= BMS 4550 52= BMS 4552 82= B&C DE82 “DRPA630HiOutOnly” is a recording of the DSP HF output driven by a Phillips CD player. The recordings below are an excerpt from Ed Kabotie’s song, “7 Cities of Gold” [URL="http://dreamcatcher.com/ed-kabotie-freedom-songs.html"]Ed Kabotie Freedom Songs - DreamCatcher.com[/URL] with voice, acoustic guitar and wood flute used to compare the output of the various HF drivers all fitted to the same type horn. The drivers were equalized as flat as possible from 630 to 16K using the three PEQ and 1/3 octave filters afforded by the DBX DriveRack PA. Each driver also used a specific delay compensation to align it with the LF track, slightly different delay and EQ were required for the 1250 Hz alignment. The process was akin to aligning a dozen different PA systems, no small feat in itself. The process “babied” the 1” drivers, allowing for the LF track to carry some extra “weight” around the 630 Hz crossover point. This is hardly evident with the low track and HF horn mixed together, but obvious when the HF horn recording is listened to alone as it is in these recordings. The actual SPL and power levels for the recordings are: 1An0630 0, 630 Hz (7.3 watts, 116.7 dBA peak) 1Ap1363 +13, 630 Hz ( 146 watts, 128.9 dBA peak) 1Ap1763 +17, 630 Hz (367 watts, 132.4 dBA peak, oops) 1Ap1312 +13, 1250 Hz (73 watts, 127.8 dBA peak) 02n0630 0, 630 Hz (7.3 watts, 110.3 dBA peak) 02p0125 0, 1250 Hz ( 11.5 watts 113.8 dBA peak) 02p10125 +10, 1250 Hz (115 watts 118.9 dBA peak) 02p15 125 +15, 1250 Hz (367 watts 125.8 dBA peak, oops) 50n0630 0, 630 Hz (7.3 watts, 114 dBA peak) 50p13125 +13, dBA 1250 Hz (36.6 watts, 125.5 dBA peak) 52n0630 0, 630 Hz (7.3 watts, 116.3 dBA peak) 52p13125 +13, 1250 Hz( 36.6 watts 124.6 dBA peak) 82n0630 0, dBA 630 Hz (7.3 watt 113.2 dBA peak) 82p1363 +13, 630 Hz (146 watts 126.3 dBA peak) 82p1312 +13, 1250 Hz (73 watts 121.6 peak) Not wanting to run the risk of burning up this antique driver, it was given less power: PAp363 +3, dBA 630 Hz ( 14.6 watts 96.3 dBA peak) PAp912 +9, dBA 1250 Hz (46 watts, 99.5 dBA peak) [B]The files are in mp3 format, to open them change the suffix < .pdf > to <.mp3 > they will open with your mp3 app.[/B] Hope you find the recordings interesting, they offer an insight in compression driver comparison (as far as I know) never undertaken before this study. Art Welter [/QUOTE]
Insert quotes…
Verification
Post reply
Home
Forums
Pro Audio
Varsity
High Frequency Compression Driver Evaluation
Top
Bottom
Sign-up
or
log in
to join the discussion today!