As well as various frequency response and distortion tests, this evaluation of high frequency drivers allows you to compare the recorded sound of six different compression drivers on the same model horn, (each equalized for flat response) to the original recording.
Two different crossover points were used, for each driver, 630Hz and 1250Hz.
No actual woofer was used, the woofer is "virtual" having been edited in the sound files from the original source (low passed) and added to the high frequency horn recording.
The recordings of the compression drivers were run at different drive levels using both sine waves and music.
The low level music recordings used around one watt, high level recordings were at levels up to 132.4 dB at one meter.
The recordings are normalized, so everything you hear is at the same volume, allowing you to hear the changes in character as drive level and sound pressure level are increased in the various tests.
This gives a unique opportunity to compare different drivers with your own headphones or speakers in a familiar listening environment at a level comfortable to you.
A list of the recordings and where to find them is at the bottom of the post under "recordings".
This HF compression driver evaluation was undertaken for three basic reasons:
1. Advances in materials and design has led to higher power handling which may correspond to additional available output and lower distortion.
2. The DH1AMT / DH1A drivers presently in my speaker cabinets weigh 23 pounds, a weight savings of 10 to 20 pounds per 50 pound cabinet could be realized with other drivers.
3. Most of my sound work presently is in the dry high desert of New Mexico, HF air losses in hot summer temperatures require far more acoustic power to overcome those losses compared to similar heat at high humidity.
HF air losses are in addition to the inverse distance 6 dB per doubling of distance.
For example, at 90 degrees, 80 % relative humidity, HF air loss is only 2.4 dB per 100 feet, while at 20% humidity, 22.9 dB loss occurs.
To achieve the same HF response at 100 feet in the desert would requires a 20 .5 dB increase in SPL, over 20 times the power (without considering power compression).
Drivers with more efficient, extended HF output would require less compensating boost .
In the past two decades, LF driver technology has made large advances in linear excursion capability and power handling, resulting in more clean LF output per driver, although requiring more power to achieve that goal.
Thiele -Small parameters for cone transducers make comparison of cone speakers relatively easy, allow allowing reasonably reliable predictions of response in a particular cabinet alignment.
HF compression driver manufacturers do not publish TS parameters, at best one gets power, Fs (resonant frequency) diaphragm size and composition, exit diameter and response on a specific horn or plane wave tube, sometimes with harmonic distortion figures derived from a single frequency sweep at a small fraction of rated power.
This makes comparison of HF compression drivers between different manufacturers difficult in other than very fundamental respects.
Even comparing within the same company can be difficult, the newer EV DH7 can’t be compared to the older DH1AMT on paper, they used different horns in testing.
This comparison is rather extensive, some basic facts about the drivers and test results are presented first, then my opinions regarding the facts, then my opinions about how the drivers sound with music, then a seemingly endless barrage of test data, pictures, charts and recordings.
The Facts:
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, Exit 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, 24, 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
JensenD-30, PA, 30?, ?, ?, .75”, 2.25”?, Aluminum, 11.40, <0, 2.5
All the tests, other than noted, 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.
1) 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 DE82TN having slightly more output below 1000 Hz, other than the DH1A having slightly more output below 250 Hz.
2/18/16 Revision: I noticed when comparing drivers tested recently to these tests that upper intermodulation distortion (the addition of two fundamental frequencies, 523 + 932 creating a third frequency of 1455, etc.) had been mistaken for ordinary order upper harmonics, resulting in (consistently) under reporting distortion %. Testing a 3.5" Tymphony TC9FD-18-08 "full range" driver on the Maltese horn, found that it had far less IM distortion than the best of the compression drivers, though is not capable of quite as much high frequency output due to less power handling and lower sensitivity.
Comparisons of the TC9FD to the EV DH1A distortion can be seen in post #60.
In the 2 meter dual sine wave “lo” test (about one watt at 523 & 932 Hz, two watts total), second harmonic distortion (2ndHD) of 530 Hz was >32% for the BMS 4552 at 82.6 dB, the BMS 4550 put out 85.2 dB with the same distortion.
These small BMS drivers are only capable of low distortion output down this low at a drive 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%, 409 Hz (difference frequency between the two upper tones) was only 17 dB below the fundamental tone.
The old Jensen did 82.6 dB with half the distortion, 16%.
The inexpensive PSD2002 was a surprise, with 6 dB more power, it hit 95.7 dB at 523 Hz with 8% 2nd HD.
The B&C DE82 at +6 dB did 98.9 dB, 6% 2ndHD.
At +9 dB, 101.9 dB 7% 2nd HD, 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 2nd HD. 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 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.
2) 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
3) The “Hi” test using 2093 & 3729 Hz resulted in less disparity between the drivers, the EV still providing the most output at a reasonable distortion %.
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
4) The B&C has 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.
5) 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&CDE82 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 tones at 104 dB SPL are available in posts #179 #182 of:
http://www.diyaudio.com/forums/multi-way/210914-what-benefits-adding-hf-driver-7khz-up-18.html
Opinions:
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 EVDH1A has more output available with less audible distortion than the other drivers. The B&C, also using a 3” diaphragm, was the next in terms of high output vs. distortion.
The 3” diaphragm drivers have a 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.
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.
I can share the HF tracks separately, but will initially post the mixed output of the LF crossover with the HF horn recording.
Because of the quantity of charts and pictures to post, they are spread over several posts.
Conclusions:
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 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 fighting 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&CDE82 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 have all the other great attributes (other than price) that address those small issues.
I was hoping to find a lighter weight replacement with sound quality exceeding the ElectroVoice DH1A, but 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.
Tests:
Crest CC2800 at “0 dB” (X20 gain setting), Smaart sine wave at -20 dB =4.04 volts (later checked 60 Hz, it was 4.09 v).
Pink noise at -8 for “on” tests, 250 Hz HP LR 24 DBX DriveRack PA.
On axis FR & Phase= driver abbreviation, “on” Maltese horn (13 degree horn angle) 2 meters (2” to 1” adapters are 6 degree, 1.4” to 2” are 7 degrees)
4 volt (one watt) 2.5K sine wave 2 meters=driver abbreviation,”oneW2.5K”
The sum of two different signal powers is roughly + 3 dB if the two powers are equal . Dual sine tests start at -20, about two watts of power, one watt at each frequency.
C 523.251, B flat 932.328 523 & 932 Hz ”Lo”
C 1046.5, B flat 1864.66 , 1046 &1865 Hz ”Mid”
C 2093, B flat 3729.31, 2093 & 3729 Hz ”Hi”
Dual Sine wave 2 meters =driver abbreviation, “dsLo” “dsMid”,”dsHi”
If distortion was not above 10%, level was increased by 3 dB until was
driver abbreviation, “dsLo” +3, +6 +9
An excerpt from Ed Kabotie’s song, “7 Cities of Gold” with voice, acoustic guitar and wood flute was used for a music piece.
Ed Kabotie Freedom Songs - DreamCatcher.com
The drivers were equalized to as flat as possible from 630 to 16K using a DBX DriveRack PA , then the excerpt was played to determine what input level would make the amp’s clip light illuminate so power levels could be compared. SPL level dBA “Slow” read about 12 dB less than peak ( dBA impulse) reading.
The Crest CC 2800 used is rated 1400 at 2 ohms, 965 at 4 ohms, 595 watts at 8 ohms, but has no 16 ohm rating, going from the other power ratings it is estimated at 367 watts in to a 16 ohm load when the clip indicator illuminates.
The various DSP settings result in slightly different drive levels, so the excerpt was played to determine at what drive level the amp clipped, then relative wattage for each level derived assuming a 16 ohm load.
Noise floor in general was about 65 dBA, various wind gusts, bird and car noises can be heard in the lower volume tests.
A 24 dB per octave 200 Hz HP filter is engaged on the Logic (similar to Pro Tools for Macintosh) recording of the horn/driver, a 24 dB per octave 30 Hz HP filter is engaged on the DRPA output which has been mixed in with the HF horn to make the recording, full range, yet with with reduced wind noise and (hopefully) similar phase response. Logic recordings have been “bounced to MP3.
The recordings of the horn only are available upon request.
The musical excerpt was also recorded using the DH1A on a Paraline horn (1AP...), the 4552 also tested on a 90 x45 A horn (52a...).
BMS 4550
50on
50oneW2.5K 109.6 dB 5K 87.3 dB 7.5K 64 dB
50oneW10K 104 dB dB 20K 80.5 dB
50dsLo 530 Hz 85.2 dB, 1060 Hz 75 dB, 2ndHD 32%
50dsMid
50dsMid+3 1046 Hz 105.7 dB, 2092 Hz 84 dB, 2ndHD 8 %
50dsHi 2093 Hz 110.7 dB, 4186 Hz 86.4 dB, 6% 2ndHD %
50dsVHF (16 kHz, 20 kHz) 16K 104.8 dB, 20K 94.5 dB 4K 56.4 dB
Music Recordings, crossover at at 630 and 1250 Hz:
50n2063 -20, 630 Hz ( .073 watt, 94.2 dBA peak)
50n1063 -10, 630 Hz ( .73 watt, 103.8 dBA peak)
50n0630 0, 630 Hz (7.3 watts, 114 dBA peak)
50n0125 0,1250 Hz (1.83 watts, 109.1, dBA peak)
50p10125 +10, 1250 Hz (18.3 watts, 122.3 dBA peak)
50p13125 +13, 1250 Hz (36.6 watts, 125.5 dBA peak)
+ 17 is just below amp clipping at 630 Hz (with comp gain +3)
+ 20 is just below amp clipping at 1250 Hz (with comp gain +4)
BMS 4552
52on
52oneW2.5K 109.6 dB 5k 87.2 dB 7.5K 67.6 dB
52Aone2.5K (on 90 x45Asymetric horn)103.8 dB 5K 70.7 dB 7.5K 52.2 dB
52oneW10K 105.4 dB 20K 82.5 dB
52dsLo 530 Hz 82.6 dB, 1060 Hz 72.4 dB, 32%2ndHD
52dsMid
52dsMid+3 1046 Hz 104.8 dB, 2092 Hz 85.1 dB, 10 % 2ndHD
52dsHi 2093 Hz 110.3 dB, 4186 Hz 84.7 dB, < 6% 2ndHD
52dsVHF (16 kHz, 20 kHz) 16K 104.7 dB , 20K 95.7 dB, 4K 60.6 dB
Music Recordings, crossover at at 630 and 1250 Hz:
52n20630 -20, 630 Hz ( .073 watt, 93.1 dBA peak)
52n10630 -10, 630 Hz ( .73 watt 102.7 dBA peak)
52n0630 0, 630 Hz (7.3 watts, 116.3 dBA peak)
52n0125 0,1250 Hz(4.56 watts, 111.3 dBA peak)
52p10125 +10,1250 Hz (18.3 watts 116.9 dBA peak)
52p13125 +13, 1250 Hz(36.6 watts 124.6 dBA peak)
52a0125 0,1250 Hz 90 x45 A horn (5.74 watts, 105.8 dBA peak) (Asymmetric, 10 degs down)
52a1063 +10, 1250 Hz 90 x45 A horn(57.4 watts 110.7 dBA peak)
52a1363 +13, 1250 Hz 90 x45 A horn( 115 watts 114.0 dBA peak)
+ 17 is just below amp clipping at 630 Hz
+ 20 is just below amp clipping at 1250 Hz (+19 with 52A EQ)
B&CDE82
82on
82oneW2.5K 105.1 dB 5K 74.9 dB 7.5K 51.9 dB 10K 47.3 dB
82oneW10K 104.9 dB 20 K 79.9 dB
82 25W (25 watts at 2.5K) 115.7dB 5K 94.4 dB 7.5K77.8 dB 10K 63 dB
82dsLo
82dsLo+6 530 Hz 98.9 dB, 1060 Hz 74.7 dB, 6% 2ndHD
82dsMid
82dsMid1m At one meter instead of 2
82dsMid+3 1046 Hz 106.6 dB, 2092 Hz 81.1 dB , 6% 2ndHD
82dsHi
82dsHi+3
82dsHi+6 2093 Hz 111.1 dB, 4186 Hz 83 dB, 5% 2ndHD
82dsVHF (16 kHz, 20 kHz) 16K 103.5 dB, 20K 96.7 dB, 4K 56.0 dB
82 25w (16.48 V, 2 meter, “0 dB attenuation)
82throat ( 5.75V at 10 inches from bug screen, 0 dB attenuation )
82mouth ( 16.48 V 10 inches from mouth, 0 dB attenuation)
Music Recordings, crossover at at 630 and 1250 Hz:
82n20630 -20, 630 Hz (.073 watt 96 dBA peak)
82n10630 -10, 630 Hz (.73 watt 103.2 dBA peak)
82n0630 0, 630 Hz (7.3 watt 113.2 dBA peak)
82p1063 +10, 630 Hz ( 73 watts 123.5 dBA peak)
82p1363 +13, 630 Hz (146 watts 126.3 dBA peak)
82p1312 +13, 1250 Hz (73 watts 121.6 peak)
+17 is just below amp clipping at 630 Hz
+20 is just below amp clipping at 1250 Hz
Eminence PSD2002
(Series 1 diaphragm, less VHF, smoother response than Series 2 diaphragm)
02on
02oneW2.5K 105.1 dB 5K 74.9 dB 7.5K 51.6 dB 10K 63.5 dB
02oneW10K 105.0 dB 20K 78.5 dB
02dsLo
02dsLo+3
02dsLo+6 530 Hz 95.7 dB, 1060 Hz 73.2 dB, 8% 2ndHD (chart taken too soon, shows “skirts”)
02dsMid
02dsMid+3 1046 Hz 104 dB, 2092 Hz 80.1 dB, 7% 2ndHD
02dsHi
02dsHi+3
02dsHi+6 2093 Hz 108.4 dB, 4186 Hz 79.6 dB, 4% 2ndHD
02dsVHF (16 kHz, 20 kHz) 16K 77.6 dB, 20K 81.8 dB, 11.89K 46 dB 4K 46.2 dB
Music Recordings, crossover at at 630 and 1250 Hz
02n20630 -20, 630 Hz ( .073 watt, 83.5 dBA peak)
02n10630 -10, 630 Hz ( .73 watt, 98.4 dBA peak)
02n0630 0, 630 Hz (7.3 watts, 110.3 dBA peak)
02p0125 0, dBA 1250 Hz ( 11.5 watts 113.8 dBA peak)
02p10125 +10, dBA 1250 Hz (115 watts 118.9 dBA peak)
02p15 125 +15, dBA 1250 Hz (367 watts 125.8 dBA peak, oops)
+17 is just below amp clipping at 630 Hz (after lowering gain by 5 dB)
+15 is just below amp clipping at 1250 Hz (gain normal)
Electro Voice DH1A16
DH1AMT16 is the same driver without the 2” to 1.4” adapter, it weighs about 2.5 lb. less, thought the EV spec sheet claims it to be only .2 pounds less.
1Aon
1AoneW2.5K 108.5, 5K 83.1, 7.5K 64.4
1AoneW2.5K A
1AoneW2.5K C
1APon (Paraline)
1APoneW2.5K (Paraline) 101.5, 5K 59.5 dB 7.5K 54.5
1AoneW10K 106.2 20K 82.7
1AdsLo -20
1AdsLo+3 -17
1AdsLo +6 -14
1AdsLo+9 -11 530 Hz 101.9 dB, 1060 Hz 78.7 dB, 7% 2ndHD
1AdsMid
1AdsMid+6
1AdsMid+9 1046 Hz 112.1 dB, 2092 Hz 92.2 dB, 10%2ndHD
1AdsHi
1AdsHi+3 2093 Hz 112.9 dB, 4186 Hz 88.6 dB, < 6% 2ndHD
1AdsVHF (16 kHz, 20 kHz) 16K 102.6 dB, 20K 86.6 dB, 4K 53.9 dB
Music Recordings, crossover at at 630 and 1250 Hz
1An20630 -20, 630 Hz ( .073 watts, 96 dBA peak)
1An10630 -10, 630 Hz ( .73 watts 103.2 dBA peak)
1An0630 0, 630 Hz (7.3 watts, 116.7 dBA peak)
1Ap1063 +10, 630 Hz ( 73 watts, 122.3 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)
1APn20630 -20, 630 Hz Paraline ( .073 watt, 88 dBA peak)
1APn10630 -10, 630 Hz Paraline ( .73 watts, 95.9 dBA peak)
1APn0630 0, 630 Hz Paraline (7.3 watts, 108.7 peak)
1APp1063 +10, 630 Hz Paraline( 73 watts, 119.8 peak)
1APp1363 +13, 630 Hz Paraline( 146 watts, 122.8 dBA peak)
1APp1312 +13, 1250 Hz Paraline (115 watts, 119.5 dBA peak)
+17 is just below amp clipping at 630 Hz (for Paraline, too)
+20 is just below amp clipping at 1250 Hz ( -19 for Paraline)
Jensen Hypex D-30
The D-30 1” 18-TPI thread on driver was used on PA reentrant horns and Leslie rotating horns. It’s rolled off HF response works well to reduce the upper noise content of the Hammond organ tone wheels.
It appears to have an aluminum diaphragm with no phase plug.
The diaphragm is visible through the throat exit, the cavity in front of the diaphragm reducing in size to the 5/8” diameter exit produces an acoustic low pass filter, response drops at about 18 dB per octave from 2500 Hz with resonant peaks at 8.39, 13.71, and 23.34 kHz, and a shelved response from around 8 to 16 kHz.
After the tests, when checking out the throat there was a fair amount of debris in it, possibly remnants of some damping material that fell apart over the years. Surprisingly, this sawdust like material (possibly cellulose fiber) caused no apparent buzzing, even though it was bouncing off the front of the diaphragm as the horn was tested pointing upward.
Driver code is 220439 (model D-30,C6101), this Jensen Hypex could have been manufactured in 1954, ‘64, or ‘74.
PAon
PAoneW2.5K 105.4 dB 5K 77.3 dB 7.5K 62.3 dB
PAoneW10K 73.3, dB 20K less than 46.3 dB, buried below the noise threshold
PAdsLo 530 Hz 82.6 dB, 1060 Hz 66.2 dB, 16% 2ndHD
PAdsMid
PAdsMid+3
PAdsMid+6 1046 Hz 104 dB, 2092 Hz, 80.5 dB, 7% 2ndHD
PAdsHi 2093 Hz 106.4 dB, 4186 Hz, 77.3 dB, <4 % 2ndHD
PAdsVHF (16 kHz, 20 kHz) 16K 58.6 dB, 20K 60.6 dB, 10K 44.1 dB 4K 33.0 dB
The dual sine VHF caused a pulsing response cycling at about 2 second intervals, all the other drivers SPL remained stable.
PAn20630 -20, 630 Hz ( .073 watt, 75.4 dBA peak)
PAn10630 -10, 630 Hz (.73 watt , 79.2 dBA peak)
PAn0630 0, 630 Hz (7.3 watts, 95.3 dBA peak)
PAp363 +3, 630 Hz ( 14.6 watts 96.3 dBA peak)
PAp312 +3, 1250 Hz (11.5 watts, 93.8 dBA peak)
PAp612 +6, 1250 Hz (23 watts, 96.8 dBA peak)
PAp912 +9, 1250 Hz (46 watts, 99.5 dBA peak)
+15 is just below amp clipping at 630 Hz(-12 on Xover for -20, -10, 0 tests)
+16 is just below amp clipping at 1250 Hz
Inverse distance test:
1.25K crossover set to +4.5 with EQ, pink noise output at -2, amp 0.
82dBA110 2 meters
82dBA 115.2 1meter
82dBA 119.7 .5 meter 19.5”
82dBA122 .5 .25 meter 9.75”
82dBA 124.2 .125 meter 4.875”
82dBA 126.3 at horn mouth, 26” from throat screen
82dBA 131.7 13” from screen
82dBA136.8 6.5” from screen
82dBA 141.0 3.25” from screen
82dBA 143.7 at screen (144+ on impulse, flat) (about 8.2 V )
82dBA 149.1 at screen, amp xover output turned up to +11 (+6.5 dB over last test, reads 17.5V)
152.8 is 0 dB Full Scale for the B&K 4004 at -12 dB in Smaart
Set up photos, frequency response and RTA screen shots of the dual tone tests are attached to this first post.
Recordings:
Recordings of 523 & 932 Hz "low" dual sine tones dual sine wave recordings (“C” & “B flat) in MP3 format are attached are posted in #2.
1046 & 1865 Hz ”Mid” dual sine wave recordings in MP3 format are attached in post #5.
The 1046 & 1865 Hz for the B&CDE82TN and 2093 & 3729 Hz ”Hi” dual sine wave recordings are posted in #7.
Music recordings start in post #9, including the equalized driver frequency response.
More higher power level Music recordings are in post #11 and #14.
The highest SPL level Music recordings are in post #15.
The remaining Music recordings are in posts # 26 & 27.
Music recordings of the HF horn output only, with no low frequency "virtual driver":
http://soundforums.net/varsity/4329-high-frequency-compression-driver-evaluation.html#post29143
Testing took a total of 50 hours.
Another 96 hours were spent to mix, analyze, write up and post the findings, a total of 146 hours of work in this project.
I found the answers to my main questions regarding the newer drivers in the first two days of testing, hope you find the recordings of all the drivers of interest.
The recordings afford an insight in compression driver comparison (as far as I know) never available to the public before this study.
Art Welter
Two different crossover points were used, for each driver, 630Hz and 1250Hz.
No actual woofer was used, the woofer is "virtual" having been edited in the sound files from the original source (low passed) and added to the high frequency horn recording.
The recordings of the compression drivers were run at different drive levels using both sine waves and music.
The low level music recordings used around one watt, high level recordings were at levels up to 132.4 dB at one meter.
The recordings are normalized, so everything you hear is at the same volume, allowing you to hear the changes in character as drive level and sound pressure level are increased in the various tests.
This gives a unique opportunity to compare different drivers with your own headphones or speakers in a familiar listening environment at a level comfortable to you.
A list of the recordings and where to find them is at the bottom of the post under "recordings".
This HF compression driver evaluation was undertaken for three basic reasons:
1. Advances in materials and design has led to higher power handling which may correspond to additional available output and lower distortion.
2. The DH1AMT / DH1A drivers presently in my speaker cabinets weigh 23 pounds, a weight savings of 10 to 20 pounds per 50 pound cabinet could be realized with other drivers.
3. Most of my sound work presently is in the dry high desert of New Mexico, HF air losses in hot summer temperatures require far more acoustic power to overcome those losses compared to similar heat at high humidity.
HF air losses are in addition to the inverse distance 6 dB per doubling of distance.
For example, at 90 degrees, 80 % relative humidity, HF air loss is only 2.4 dB per 100 feet, while at 20% humidity, 22.9 dB loss occurs.
To achieve the same HF response at 100 feet in the desert would requires a 20 .5 dB increase in SPL, over 20 times the power (without considering power compression).
Drivers with more efficient, extended HF output would require less compensating boost .
In the past two decades, LF driver technology has made large advances in linear excursion capability and power handling, resulting in more clean LF output per driver, although requiring more power to achieve that goal.
Thiele -Small parameters for cone transducers make comparison of cone speakers relatively easy, allow allowing reasonably reliable predictions of response in a particular cabinet alignment.
HF compression driver manufacturers do not publish TS parameters, at best one gets power, Fs (resonant frequency) diaphragm size and composition, exit diameter and response on a specific horn or plane wave tube, sometimes with harmonic distortion figures derived from a single frequency sweep at a small fraction of rated power.
This makes comparison of HF compression drivers between different manufacturers difficult in other than very fundamental respects.
Even comparing within the same company can be difficult, the newer EV DH7 can’t be compared to the older DH1AMT on paper, they used different horns in testing.
This comparison is rather extensive, some basic facts about the drivers and test results are presented first, then my opinions regarding the facts, then my opinions about how the drivers sound with music, then a seemingly endless barrage of test data, pictures, charts and recordings.
The Facts:
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, Exit 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, 24, 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
JensenD-30, PA, 30?, ?, ?, .75”, 2.25”?, Aluminum, 11.40, <0, 2.5
All the tests, other than noted, 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.
1) 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 DE82TN having slightly more output below 1000 Hz, other than the DH1A having slightly more output below 250 Hz.
2/18/16 Revision: I noticed when comparing drivers tested recently to these tests that upper intermodulation distortion (the addition of two fundamental frequencies, 523 + 932 creating a third frequency of 1455, etc.) had been mistaken for ordinary order upper harmonics, resulting in (consistently) under reporting distortion %. Testing a 3.5" Tymphony TC9FD-18-08 "full range" driver on the Maltese horn, found that it had far less IM distortion than the best of the compression drivers, though is not capable of quite as much high frequency output due to less power handling and lower sensitivity.
Comparisons of the TC9FD to the EV DH1A distortion can be seen in post #60.
In the 2 meter dual sine wave “lo” test (about one watt at 523 & 932 Hz, two watts total), second harmonic distortion (2ndHD) of 530 Hz was >32% for the BMS 4552 at 82.6 dB, the BMS 4550 put out 85.2 dB with the same distortion.
These small BMS drivers are only capable of low distortion output down this low at a drive 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%, 409 Hz (difference frequency between the two upper tones) was only 17 dB below the fundamental tone.
The old Jensen did 82.6 dB with half the distortion, 16%.
The inexpensive PSD2002 was a surprise, with 6 dB more power, it hit 95.7 dB at 523 Hz with 8% 2nd HD.
The B&C DE82 at +6 dB did 98.9 dB, 6% 2ndHD.
At +9 dB, 101.9 dB 7% 2nd HD, 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 2nd HD. 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 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.
2) 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
3) The “Hi” test using 2093 & 3729 Hz resulted in less disparity between the drivers, the EV still providing the most output at a reasonable distortion %.
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
4) The B&C has 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.
5) 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&CDE82 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 tones at 104 dB SPL are available in posts #179 #182 of:
http://www.diyaudio.com/forums/multi-way/210914-what-benefits-adding-hf-driver-7khz-up-18.html
Opinions:
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 EVDH1A has more output available with less audible distortion than the other drivers. The B&C, also using a 3” diaphragm, was the next in terms of high output vs. distortion.
The 3” diaphragm drivers have a 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.
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.
I can share the HF tracks separately, but will initially post the mixed output of the LF crossover with the HF horn recording.
Because of the quantity of charts and pictures to post, they are spread over several posts.
Conclusions:
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 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 fighting 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&CDE82 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 have all the other great attributes (other than price) that address those small issues.
I was hoping to find a lighter weight replacement with sound quality exceeding the ElectroVoice DH1A, but 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.
Tests:
Crest CC2800 at “0 dB” (X20 gain setting), Smaart sine wave at -20 dB =4.04 volts (later checked 60 Hz, it was 4.09 v).
Pink noise at -8 for “on” tests, 250 Hz HP LR 24 DBX DriveRack PA.
On axis FR & Phase= driver abbreviation, “on” Maltese horn (13 degree horn angle) 2 meters (2” to 1” adapters are 6 degree, 1.4” to 2” are 7 degrees)
4 volt (one watt) 2.5K sine wave 2 meters=driver abbreviation,”oneW2.5K”
The sum of two different signal powers is roughly + 3 dB if the two powers are equal . Dual sine tests start at -20, about two watts of power, one watt at each frequency.
C 523.251, B flat 932.328 523 & 932 Hz ”Lo”
C 1046.5, B flat 1864.66 , 1046 &1865 Hz ”Mid”
C 2093, B flat 3729.31, 2093 & 3729 Hz ”Hi”
Dual Sine wave 2 meters =driver abbreviation, “dsLo” “dsMid”,”dsHi”
If distortion was not above 10%, level was increased by 3 dB until was
driver abbreviation, “dsLo” +3, +6 +9
An excerpt from Ed Kabotie’s song, “7 Cities of Gold” with voice, acoustic guitar and wood flute was used for a music piece.
Ed Kabotie Freedom Songs - DreamCatcher.com
The drivers were equalized to as flat as possible from 630 to 16K using a DBX DriveRack PA , then the excerpt was played to determine what input level would make the amp’s clip light illuminate so power levels could be compared. SPL level dBA “Slow” read about 12 dB less than peak ( dBA impulse) reading.
The Crest CC 2800 used is rated 1400 at 2 ohms, 965 at 4 ohms, 595 watts at 8 ohms, but has no 16 ohm rating, going from the other power ratings it is estimated at 367 watts in to a 16 ohm load when the clip indicator illuminates.
The various DSP settings result in slightly different drive levels, so the excerpt was played to determine at what drive level the amp clipped, then relative wattage for each level derived assuming a 16 ohm load.
Noise floor in general was about 65 dBA, various wind gusts, bird and car noises can be heard in the lower volume tests.
A 24 dB per octave 200 Hz HP filter is engaged on the Logic (similar to Pro Tools for Macintosh) recording of the horn/driver, a 24 dB per octave 30 Hz HP filter is engaged on the DRPA output which has been mixed in with the HF horn to make the recording, full range, yet with with reduced wind noise and (hopefully) similar phase response. Logic recordings have been “bounced to MP3.
The recordings of the horn only are available upon request.
The musical excerpt was also recorded using the DH1A on a Paraline horn (1AP...), the 4552 also tested on a 90 x45 A horn (52a...).
BMS 4550
50on
50oneW2.5K 109.6 dB 5K 87.3 dB 7.5K 64 dB
50oneW10K 104 dB dB 20K 80.5 dB
50dsLo 530 Hz 85.2 dB, 1060 Hz 75 dB, 2ndHD 32%
50dsMid
50dsMid+3 1046 Hz 105.7 dB, 2092 Hz 84 dB, 2ndHD 8 %
50dsHi 2093 Hz 110.7 dB, 4186 Hz 86.4 dB, 6% 2ndHD %
50dsVHF (16 kHz, 20 kHz) 16K 104.8 dB, 20K 94.5 dB 4K 56.4 dB
Music Recordings, crossover at at 630 and 1250 Hz:
50n2063 -20, 630 Hz ( .073 watt, 94.2 dBA peak)
50n1063 -10, 630 Hz ( .73 watt, 103.8 dBA peak)
50n0630 0, 630 Hz (7.3 watts, 114 dBA peak)
50n0125 0,1250 Hz (1.83 watts, 109.1, dBA peak)
50p10125 +10, 1250 Hz (18.3 watts, 122.3 dBA peak)
50p13125 +13, 1250 Hz (36.6 watts, 125.5 dBA peak)
+ 17 is just below amp clipping at 630 Hz (with comp gain +3)
+ 20 is just below amp clipping at 1250 Hz (with comp gain +4)
BMS 4552
52on
52oneW2.5K 109.6 dB 5k 87.2 dB 7.5K 67.6 dB
52Aone2.5K (on 90 x45Asymetric horn)103.8 dB 5K 70.7 dB 7.5K 52.2 dB
52oneW10K 105.4 dB 20K 82.5 dB
52dsLo 530 Hz 82.6 dB, 1060 Hz 72.4 dB, 32%2ndHD
52dsMid
52dsMid+3 1046 Hz 104.8 dB, 2092 Hz 85.1 dB, 10 % 2ndHD
52dsHi 2093 Hz 110.3 dB, 4186 Hz 84.7 dB, < 6% 2ndHD
52dsVHF (16 kHz, 20 kHz) 16K 104.7 dB , 20K 95.7 dB, 4K 60.6 dB
Music Recordings, crossover at at 630 and 1250 Hz:
52n20630 -20, 630 Hz ( .073 watt, 93.1 dBA peak)
52n10630 -10, 630 Hz ( .73 watt 102.7 dBA peak)
52n0630 0, 630 Hz (7.3 watts, 116.3 dBA peak)
52n0125 0,1250 Hz(4.56 watts, 111.3 dBA peak)
52p10125 +10,1250 Hz (18.3 watts 116.9 dBA peak)
52p13125 +13, 1250 Hz(36.6 watts 124.6 dBA peak)
52a0125 0,1250 Hz 90 x45 A horn (5.74 watts, 105.8 dBA peak) (Asymmetric, 10 degs down)
52a1063 +10, 1250 Hz 90 x45 A horn(57.4 watts 110.7 dBA peak)
52a1363 +13, 1250 Hz 90 x45 A horn( 115 watts 114.0 dBA peak)
+ 17 is just below amp clipping at 630 Hz
+ 20 is just below amp clipping at 1250 Hz (+19 with 52A EQ)
B&CDE82
82on
82oneW2.5K 105.1 dB 5K 74.9 dB 7.5K 51.9 dB 10K 47.3 dB
82oneW10K 104.9 dB 20 K 79.9 dB
82 25W (25 watts at 2.5K) 115.7dB 5K 94.4 dB 7.5K77.8 dB 10K 63 dB
82dsLo
82dsLo+6 530 Hz 98.9 dB, 1060 Hz 74.7 dB, 6% 2ndHD
82dsMid
82dsMid1m At one meter instead of 2
82dsMid+3 1046 Hz 106.6 dB, 2092 Hz 81.1 dB , 6% 2ndHD
82dsHi
82dsHi+3
82dsHi+6 2093 Hz 111.1 dB, 4186 Hz 83 dB, 5% 2ndHD
82dsVHF (16 kHz, 20 kHz) 16K 103.5 dB, 20K 96.7 dB, 4K 56.0 dB
82 25w (16.48 V, 2 meter, “0 dB attenuation)
82throat ( 5.75V at 10 inches from bug screen, 0 dB attenuation )
82mouth ( 16.48 V 10 inches from mouth, 0 dB attenuation)
Music Recordings, crossover at at 630 and 1250 Hz:
82n20630 -20, 630 Hz (.073 watt 96 dBA peak)
82n10630 -10, 630 Hz (.73 watt 103.2 dBA peak)
82n0630 0, 630 Hz (7.3 watt 113.2 dBA peak)
82p1063 +10, 630 Hz ( 73 watts 123.5 dBA peak)
82p1363 +13, 630 Hz (146 watts 126.3 dBA peak)
82p1312 +13, 1250 Hz (73 watts 121.6 peak)
+17 is just below amp clipping at 630 Hz
+20 is just below amp clipping at 1250 Hz
Eminence PSD2002
(Series 1 diaphragm, less VHF, smoother response than Series 2 diaphragm)
02on
02oneW2.5K 105.1 dB 5K 74.9 dB 7.5K 51.6 dB 10K 63.5 dB
02oneW10K 105.0 dB 20K 78.5 dB
02dsLo
02dsLo+3
02dsLo+6 530 Hz 95.7 dB, 1060 Hz 73.2 dB, 8% 2ndHD (chart taken too soon, shows “skirts”)
02dsMid
02dsMid+3 1046 Hz 104 dB, 2092 Hz 80.1 dB, 7% 2ndHD
02dsHi
02dsHi+3
02dsHi+6 2093 Hz 108.4 dB, 4186 Hz 79.6 dB, 4% 2ndHD
02dsVHF (16 kHz, 20 kHz) 16K 77.6 dB, 20K 81.8 dB, 11.89K 46 dB 4K 46.2 dB
Music Recordings, crossover at at 630 and 1250 Hz
02n20630 -20, 630 Hz ( .073 watt, 83.5 dBA peak)
02n10630 -10, 630 Hz ( .73 watt, 98.4 dBA peak)
02n0630 0, 630 Hz (7.3 watts, 110.3 dBA peak)
02p0125 0, dBA 1250 Hz ( 11.5 watts 113.8 dBA peak)
02p10125 +10, dBA 1250 Hz (115 watts 118.9 dBA peak)
02p15 125 +15, dBA 1250 Hz (367 watts 125.8 dBA peak, oops)
+17 is just below amp clipping at 630 Hz (after lowering gain by 5 dB)
+15 is just below amp clipping at 1250 Hz (gain normal)
Electro Voice DH1A16
DH1AMT16 is the same driver without the 2” to 1.4” adapter, it weighs about 2.5 lb. less, thought the EV spec sheet claims it to be only .2 pounds less.
1Aon
1AoneW2.5K 108.5, 5K 83.1, 7.5K 64.4
1AoneW2.5K A
1AoneW2.5K C
1APon (Paraline)
1APoneW2.5K (Paraline) 101.5, 5K 59.5 dB 7.5K 54.5
1AoneW10K 106.2 20K 82.7
1AdsLo -20
1AdsLo+3 -17
1AdsLo +6 -14
1AdsLo+9 -11 530 Hz 101.9 dB, 1060 Hz 78.7 dB, 7% 2ndHD
1AdsMid
1AdsMid+6
1AdsMid+9 1046 Hz 112.1 dB, 2092 Hz 92.2 dB, 10%2ndHD
1AdsHi
1AdsHi+3 2093 Hz 112.9 dB, 4186 Hz 88.6 dB, < 6% 2ndHD
1AdsVHF (16 kHz, 20 kHz) 16K 102.6 dB, 20K 86.6 dB, 4K 53.9 dB
Music Recordings, crossover at at 630 and 1250 Hz
1An20630 -20, 630 Hz ( .073 watts, 96 dBA peak)
1An10630 -10, 630 Hz ( .73 watts 103.2 dBA peak)
1An0630 0, 630 Hz (7.3 watts, 116.7 dBA peak)
1Ap1063 +10, 630 Hz ( 73 watts, 122.3 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)
1APn20630 -20, 630 Hz Paraline ( .073 watt, 88 dBA peak)
1APn10630 -10, 630 Hz Paraline ( .73 watts, 95.9 dBA peak)
1APn0630 0, 630 Hz Paraline (7.3 watts, 108.7 peak)
1APp1063 +10, 630 Hz Paraline( 73 watts, 119.8 peak)
1APp1363 +13, 630 Hz Paraline( 146 watts, 122.8 dBA peak)
1APp1312 +13, 1250 Hz Paraline (115 watts, 119.5 dBA peak)
+17 is just below amp clipping at 630 Hz (for Paraline, too)
+20 is just below amp clipping at 1250 Hz ( -19 for Paraline)
Jensen Hypex D-30
The D-30 1” 18-TPI thread on driver was used on PA reentrant horns and Leslie rotating horns. It’s rolled off HF response works well to reduce the upper noise content of the Hammond organ tone wheels.
It appears to have an aluminum diaphragm with no phase plug.
The diaphragm is visible through the throat exit, the cavity in front of the diaphragm reducing in size to the 5/8” diameter exit produces an acoustic low pass filter, response drops at about 18 dB per octave from 2500 Hz with resonant peaks at 8.39, 13.71, and 23.34 kHz, and a shelved response from around 8 to 16 kHz.
After the tests, when checking out the throat there was a fair amount of debris in it, possibly remnants of some damping material that fell apart over the years. Surprisingly, this sawdust like material (possibly cellulose fiber) caused no apparent buzzing, even though it was bouncing off the front of the diaphragm as the horn was tested pointing upward.
Driver code is 220439 (model D-30,C6101), this Jensen Hypex could have been manufactured in 1954, ‘64, or ‘74.
PAon
PAoneW2.5K 105.4 dB 5K 77.3 dB 7.5K 62.3 dB
PAoneW10K 73.3, dB 20K less than 46.3 dB, buried below the noise threshold
PAdsLo 530 Hz 82.6 dB, 1060 Hz 66.2 dB, 16% 2ndHD
PAdsMid
PAdsMid+3
PAdsMid+6 1046 Hz 104 dB, 2092 Hz, 80.5 dB, 7% 2ndHD
PAdsHi 2093 Hz 106.4 dB, 4186 Hz, 77.3 dB, <4 % 2ndHD
PAdsVHF (16 kHz, 20 kHz) 16K 58.6 dB, 20K 60.6 dB, 10K 44.1 dB 4K 33.0 dB
The dual sine VHF caused a pulsing response cycling at about 2 second intervals, all the other drivers SPL remained stable.
PAn20630 -20, 630 Hz ( .073 watt, 75.4 dBA peak)
PAn10630 -10, 630 Hz (.73 watt , 79.2 dBA peak)
PAn0630 0, 630 Hz (7.3 watts, 95.3 dBA peak)
PAp363 +3, 630 Hz ( 14.6 watts 96.3 dBA peak)
PAp312 +3, 1250 Hz (11.5 watts, 93.8 dBA peak)
PAp612 +6, 1250 Hz (23 watts, 96.8 dBA peak)
PAp912 +9, 1250 Hz (46 watts, 99.5 dBA peak)
+15 is just below amp clipping at 630 Hz(-12 on Xover for -20, -10, 0 tests)
+16 is just below amp clipping at 1250 Hz
Inverse distance test:
1.25K crossover set to +4.5 with EQ, pink noise output at -2, amp 0.
82dBA110 2 meters
82dBA 115.2 1meter
82dBA 119.7 .5 meter 19.5”
82dBA122 .5 .25 meter 9.75”
82dBA 124.2 .125 meter 4.875”
82dBA 126.3 at horn mouth, 26” from throat screen
82dBA 131.7 13” from screen
82dBA136.8 6.5” from screen
82dBA 141.0 3.25” from screen
82dBA 143.7 at screen (144+ on impulse, flat) (about 8.2 V )
82dBA 149.1 at screen, amp xover output turned up to +11 (+6.5 dB over last test, reads 17.5V)
152.8 is 0 dB Full Scale for the B&K 4004 at -12 dB in Smaart
Set up photos, frequency response and RTA screen shots of the dual tone tests are attached to this first post.
Recordings:
Recordings of 523 & 932 Hz "low" dual sine tones dual sine wave recordings (“C” & “B flat) in MP3 format are attached are posted in #2.
1046 & 1865 Hz ”Mid” dual sine wave recordings in MP3 format are attached in post #5.
The 1046 & 1865 Hz for the B&CDE82TN and 2093 & 3729 Hz ”Hi” dual sine wave recordings are posted in #7.
Music recordings start in post #9, including the equalized driver frequency response.
More higher power level Music recordings are in post #11 and #14.
The highest SPL level Music recordings are in post #15.
The remaining Music recordings are in posts # 26 & 27.
Music recordings of the HF horn output only, with no low frequency "virtual driver":
http://soundforums.net/varsity/4329-high-frequency-compression-driver-evaluation.html#post29143
Testing took a total of 50 hours.
Another 96 hours were spent to mix, analyze, write up and post the findings, a total of 146 hours of work in this project.
I found the answers to my main questions regarding the newer drivers in the first two days of testing, hope you find the recordings of all the drivers of interest.
The recordings afford an insight in compression driver comparison (as far as I know) never available to the public before this study.
Art Welter
Attachments
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A photo of the B&K 4004 microphone response used for all the testing and recording is attached. The B&K 4004 uses a 130 volt power supply (compared to 10-48 volts for typical test microphones) for unusually low distortion at levels as high as 153 dB SPL.
The loudest recording, (posted in another post) was in the 130 dB range, well within the B&K 4004 linear range.
523 & 932 Hz dual sine wave recordings in MP3 format are attached,level is -12 dBFS.
The file type suffix < .zip > must be changed to < .mP3 >, they will then open with your mP3 app.
Refer to post #1 for description of the test initials, and RTA screen shots of what the harmonic distortion you hear looks like.
Art
The loudest recording, (posted in another post) was in the 130 dB range, well within the B&K 4004 linear range.
523 & 932 Hz dual sine wave recordings in MP3 format are attached,level is -12 dBFS.
The file type suffix < .zip > must be changed to < .mP3 >, they will then open with your mP3 app.
Refer to post #1 for description of the test initials, and RTA screen shots of what the harmonic distortion you hear looks like.
Art
Attachments
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2093 & 3729 Hz ”Hi” ”Mid”Hz dual sine wave recordings (“C” & “B flat) in MP3 format are attached, level is -12 dBFS.
The file type suffix < .zip > must be changed to < .mP3 >, they will then open with your mP3 app.
Refer to post #1 for description of the test initials, and RTA screen shots of what the harmonic distortion you hear looks like.
The 82dsmid test will be posted later, only 10 files per post.
Art
The file type suffix < .zip > must be changed to < .mP3 >, they will then open with your mP3 app.
Refer to post #1 for description of the test initials, and RTA screen shots of what the harmonic distortion you hear looks like.
The 82dsmid test will be posted later, only 10 files per post.
Art
The 1046 &1865 Hz ”Mid” dual sine wave recordings (“C” & “B flat”) for the B&CDE82TN in MP3 format are attached, level is -12 dBFS
The B&CDE82TN reached 6% distortion +3 from the level of the first test, unfortunately that recording was missed, though the RTA was saved.
2093 & 3729 Hz ”Hi” dual sine wave recordings (“C” & “B flat”) are also included below.
Music recordings will be posted next, refer to the bottom of Post #1 for a complete list of recordings as they are posted.
The file type suffix < .zip > must be changed to < .mP3 >, they will then open with your mP3 app.
Art
The B&CDE82TN reached 6% distortion +3 from the level of the first test, unfortunately that recording was missed, though the RTA was saved.
2093 & 3729 Hz ”Hi” dual sine wave recordings (“C” & “B flat”) are also included below.
Music recordings will be posted next, refer to the bottom of Post #1 for a complete list of recordings as they are posted.
The file type suffix < .zip > must be changed to < .mP3 >, they will then open with your mP3 app.
Art
The Maltese HF horn, though it loads to around 200 Hz, was designed for a 1200 Hz crossover. It does provide a relative comparison between the various drivers performance down low, but it's performance down low is weak.
Though all the drivers "did better" with the mid tones, the EVDH1A really crushed the other drivers with 6.4 dB more clean output available than the top 1", and 5.5 dB better than the other 1.4" exit 3" diaphragm driver.
For cleanly reproducing brass, reeds, and drums at or near "live" levels (or louder than live for sound reinforcement) the additional six dB "gets it there".
Back to the download slog, music recordings coming right up.
Art
An excerpt from Ed Kabotie’s song, “7 Cities of Gold” with voice, acoustic guitar and wood flute was used to compare the output of various HF drivers all fitted to the same type horn.
Ed Kabotie Freedom Songs - DreamCatcher.com
A full range copy of the excerpt recorded from the analog outputs of the Philips CD player used for playback on all the horn/driver recordings is presented first, that recording is “as good as it gets” here.
The CD’s analog output went to a DBX DriveRack PA , (a digital crossover with digital delay & EQ) the low and high outputs were recorded and mixed together for a “benchmark“ of any change in sound quality caused by the DSP.
Additional 24 dB per octave digital filters at 30 Hz (low channel) and 200 Hz (high channel) are also used in the mix down to MP3.
These same filters were used to reduce wind noise in the recording of the HF horn, the 30 Hz filter was inserted on the low side to result in a similar filter delay/phase for both channels of the mixed outputs.
The ”7 Cities of Gold” excerpt’s peak levels are on the “S” sounds in the word “citys”, about 14 seconds in. The 30 second overall time varies slightly by recording as each start and finish time had to be cut to length individually. The levels of each recording have been adjusted to within about 1/10th of a dB, so playback will be uniform even though the original level ultimately varies over as much as a 37 dB power input range.
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 mentioned in the OP, distortion is also much more obvious with the horn output alone.
The specifics and SPL level of each recording are given in the OP "Tests" section.
Screen shots of the raw and equalized response of the drivers are included below, levels offset for clarity, the LF response was in all cases exactly on the “0 dB” line. The “82” response shows the horn/driver’s acoustical response using the 24 dB LR crossover. The missing curve of the BMS 4550 was similar to the “52”.
I regret missing taking a shot of the equalized response of the “PA” driver, though it took “heroic” measures, as I recall it came out near as flat as the other drivers to around 16 kHz.
The “02” was the only driver not capable of flat 16K response without an inordinate (power wasting) HF boost. Rather than “cook” the voice coil with frequencies above 12.5 kHz, which would have made comparison with the other drivers difficult, I let the top 1/3 octave roll off naturally.
The file type suffix < .zip > must be changed to < .mP3 >, the music files will then open with your mP3 app.
Art
Ed Kabotie Freedom Songs - DreamCatcher.com
A full range copy of the excerpt recorded from the analog outputs of the Philips CD player used for playback on all the horn/driver recordings is presented first, that recording is “as good as it gets” here.
The CD’s analog output went to a DBX DriveRack PA , (a digital crossover with digital delay & EQ) the low and high outputs were recorded and mixed together for a “benchmark“ of any change in sound quality caused by the DSP.
Additional 24 dB per octave digital filters at 30 Hz (low channel) and 200 Hz (high channel) are also used in the mix down to MP3.
These same filters were used to reduce wind noise in the recording of the HF horn, the 30 Hz filter was inserted on the low side to result in a similar filter delay/phase for both channels of the mixed outputs.
The ”7 Cities of Gold” excerpt’s peak levels are on the “S” sounds in the word “citys”, about 14 seconds in. The 30 second overall time varies slightly by recording as each start and finish time had to be cut to length individually. The levels of each recording have been adjusted to within about 1/10th of a dB, so playback will be uniform even though the original level ultimately varies over as much as a 37 dB power input range.
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 mentioned in the OP, distortion is also much more obvious with the horn output alone.
The specifics and SPL level of each recording are given in the OP "Tests" section.
Screen shots of the raw and equalized response of the drivers are included below, levels offset for clarity, the LF response was in all cases exactly on the “0 dB” line. The “82” response shows the horn/driver’s acoustical response using the 24 dB LR crossover. The missing curve of the BMS 4550 was similar to the “52”.
I regret missing taking a shot of the equalized response of the “PA” driver, though it took “heroic” measures, as I recall it came out near as flat as the other drivers to around 16 kHz.
The “02” was the only driver not capable of flat 16K response without an inordinate (power wasting) HF boost. Rather than “cook” the voice coil with frequencies above 12.5 kHz, which would have made comparison with the other drivers difficult, I let the top 1/3 octave roll off naturally.
The file type suffix < .zip > must be changed to < .mP3 >, the music files will then open with your mP3 app.
Art
Attachments
An excerpt from Ed Kabotie’s song, “7 Cities of Gold” with voice, acoustic guitar and wood flute was used to compare the output of various HF drivers all fitted to the same type horn.
Ed Kabotie Freedom Songs - DreamCatcher.com
The specifics and SPL level of each music recording are in the OP "Tests" section.
The "- 2" output of the "PA" driver was too low to make a decent recording, "-10" has been included instead.
The file type suffix < .zip > must be changed to < .mP3 >, the music files will then open with your mP3 app.
Art
Ed Kabotie Freedom Songs - DreamCatcher.com
The specifics and SPL level of each music recording are in the OP "Tests" section.
The "- 2" output of the "PA" driver was too low to make a decent recording, "-10" has been included instead.
The file type suffix < .zip > must be changed to < .mP3 >, the music files will then open with your mP3 app.
Art
quote from OP:
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.
Although that level (and far higher) is common in PA use, most home users don't play music that loud.
For those that desire the levels achieved by live brass, reeds and percussion (which can easily exceed 110 dB at 2 meters) in their living room, it would be accompanied by some degree of distortion using the BMS 1" drivers.
Many of the music recordings of the horns are now available for you to listen to, you may determine at what level the distortion becomes unacceptable to you, or you may find that the levels of distortion at the loudest levels I recorded at are still acceptable.
The OP is updated at the bottom listing the post #s containing the recordings.
Art
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 “spitty” distortion increases in the higher power levels used in the tests, starting at a few watts of power, around 110 dB at two meters. Typical horns would have about 6 dB less output level, so would require about 8 watts to achieve that SPL, with an additional rise in distortion.
Although that level (and far higher) is common in PA use, most home users don't play music that loud.
For those that desire the levels achieved by live brass, reeds and percussion (which can easily exceed 110 dB at 2 meters) in their living room, it would be accompanied by some degree of distortion using the BMS 1" drivers.
Many of the music recordings of the horns are now available for you to listen to, you may determine at what level the distortion becomes unacceptable to you, or you may find that the levels of distortion at the loudest levels I recorded at are still acceptable.
The OP is updated at the bottom listing the post #s containing the recordings.
Art
An excerpt from Ed Kabotie’s song, “7 Cities of Gold” with voice, acoustic guitar and wood flute was used to compare the output of various HF drivers all fitted to the same type horn.
Ed Kabotie Freedom Songs - DreamCatcher.com
The specifics and SPL level of each music recording are in the OP "Tests" section.
The "1Ap1763" and "02p15 125" were "oops" moments, recorded at the full (un- clipped ) output level of the amp, around 367 watts peak. None of the other drivers were tested at these levels.
The file type suffix < .zip > must be changed to < .mP3 >, the music files will then open with your mP3 app.
Art
Ed Kabotie Freedom Songs - DreamCatcher.com
The specifics and SPL level of each music recording are in the OP "Tests" section.
The "1Ap1763" and "02p15 125" were "oops" moments, recorded at the full (un- clipped ) output level of the amp, around 367 watts peak. None of the other drivers were tested at these levels.
The file type suffix < .zip > must be changed to < .mP3 >, the music files will then open with your mP3 app.
Art
Art, thanks - I've been listening to these and hearing the differences.
Alas I'm having some trouble with the cyrptic file names and would like to rename the MP3s I have here.
I'm thinking that the first three characters are the driver name, the next 2 the dB level and last 2 are the crossover frequency (630Hz or 1250Hz), right?
So 82p1363 is the B&C driver, +13dB, 630Hz high pass. P= "program".
Alas I'm having some trouble with the cyrptic file names and would like to rename the MP3s I have here.
I'm thinking that the first three characters are the driver name, the next 2 the dB level and last 2 are the crossover frequency (630Hz or 1250Hz), right?
So 82p1363 is the B&C driver, +13dB, 630Hz high pass. P= "program".
Also, while the tests are interesting, I am wondering about the transition between the compression driver's short exit/throat and the throat of the horn. If there is a discontinuity there - the angle changes - then you may have a place where there is diffraction. Might be effecting the distortion and the HF response. Wondering about that.
_-_-bear
_-_-bear
The horn is too deep to get a clear view down the throat.
The pictures in post #1 show the side view of the Maltese horn, the four horns arranged as a Maltese cross show why it was named. The 2" throat of the horn is a simple transition from square to round.
In practice, the horns were arrayed horizontally, the last time I used them for PA I used three per side, which left HF "holes" spread to 90 degree coverage, seven Maltese horns would be required for a 13 x 90 degree pattern.
The explanations for the tests names are in post # one, each "Test" sequence details the tests undertaken for each of the six drivers.
I'd suggest printing out a copy of the tests for easy reference.
The first capitol characters are the driver name. "ds" stands for Dual Sine.
The music tests used a crossover frequency, and a variety of test levels covering as much as 37 dB range from the -20 (n20) tests to as high as p17 + 17 dB.
"n" stands for "negative" and is carried through to the "0 db" , then changes to "p" for positive (+), which carries through to +10, +13 or in a few cases +15 and + 17.
The crossover frequency was 630 or 1250, sometimes only the first few numbers, 63, or 12, or 125 were used.
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