Re: High Frequency Compression Driver Evaluation
I will try measuring the inner and outer diameter and calculate what is left. Should be close.
I will try measuring the inner and outer diameter and calculate what is left. Should be close.
High Frequency Compression Driver Evaluation
- Thread starter Art Welter
- Start date
Re: High Frequency Compression Driver Evaluation
Hi Art,
sorry for the late reply, Im buried with work,
actually I dont know drive levels, PP mag is plotting SPL versus frequency at 3 and 10% THD.
When there is time, I will measure the 920 in respect to distortion at high drive levels and post some results
Uwe
Hi Art,
sorry for the late reply, Im buried with work,
actually I dont know drive levels, PP mag is plotting SPL versus frequency at 3 and 10% THD.
When there is time, I will measure the 920 in respect to distortion at high drive levels and post some results
Uwe
Re: High Frequency Compression Driver Evaluation
Art,
How do you find the consistency between your DH1A's is? I measured a bunch of these that came out of some nearly 20 year old deltamax boxes and the response of each driver was quite significantly different (found the smaart screenshots, amazed I still had these). I don't know the history on the drivers I measured, but just wondering how these have aged for you. They are certainly a very stout driver in all senses.
Art,
How do you find the consistency between your DH1A's is? I measured a bunch of these that came out of some nearly 20 year old deltamax boxes and the response of each driver was quite significantly different (found the smaart screenshots, amazed I still had these). I don't know the history on the drivers I measured, but just wondering how these have aged for you. They are certainly a very stout driver in all senses.
Re: High Frequency Compression Driver Evaluation
Nine of ten DH1AMT I have used since 1992 are still probably all within a few dB of each other, and their response still looks like the published charts.
One pair looked a bit different, after cleaning the gaps and swapping the diaphragms between the pair, both looked better but the "most different" response followed the diaphragm, rather than the driver.
Diaphragms made at different times may have slight differences, and drivers that have been dropped may loose some magnetism, a dirty old road system probably would show more differences than a system that had light duty hanging in a church.
When taking pictures of the drivers, I found rocks and dirt to have enough ferrous content to stick to the magnets. Systems used outdoors in windy dusty conditions could collect enough particles in the gap to change response.
Jeff,
Nine of ten DH1AMT I have used since 1992 are still probably all within a few dB of each other, and their response still looks like the published charts.
One pair looked a bit different, after cleaning the gaps and swapping the diaphragms between the pair, both looked better but the "most different" response followed the diaphragm, rather than the driver.
Diaphragms made at different times may have slight differences, and drivers that have been dropped may loose some magnetism, a dirty old road system probably would show more differences than a system that had light duty hanging in a church.
When taking pictures of the drivers, I found rocks and dirt to have enough ferrous content to stick to the magnets. Systems used outdoors in windy dusty conditions could collect enough particles in the gap to change response.
Re: High Frequency Compression Driver Evaluation
Hi,
I have measured quite a few BMS drivers for Harmonic distortion along with other brands.
The one trend I see the most is at low voltage the BMS driver have more distortion then other drivers.
But once you start putting more voltage into the measurement the BMS driver has less distortion.
Hi,
I have measured quite a few BMS drivers for Harmonic distortion along with other brands.
The one trend I see the most is at low voltage the BMS driver have more distortion then other drivers.
But once you start putting more voltage into the measurement the BMS driver has less distortion.
Re: High Frequency Compression Driver Evaluation
The BMS 4550 and 4552 had more distortion at all drive (voltage) levels than the cheaper Eminence PSD 2002 as you can see (and hear) in my test results. Even the 50 (guessing) year old Jensen Hypex had less distortion than the BMS drivers.
What other brand drivers had more distortion than the BMS drivers?
Could you post the distortion measurements you took?
Art
Too Tall,
The BMS 4550 and 4552 had more distortion at all drive (voltage) levels than the cheaper Eminence PSD 2002 as you can see (and hear) in my test results. Even the 50 (guessing) year old Jensen Hypex had less distortion than the BMS drivers.
What other brand drivers had more distortion than the BMS drivers?
Could you post the distortion measurements you took?
Art
Re: High Frequency Compression Driver Evaluation
I used DH1A's for a long time and about 8 years ago switched to the Neo version NDYM1 and the later ND6x. How do you you think the Neo versions would compare to your findings. Have you ever tried any of the slightly heavier / thicker diaphragms in them like the 84234XX or 84233XX depending on your needed impedance verses the standard 81256XX or 81320XX.
I used DH1A's for a long time and about 8 years ago switched to the Neo version NDYM1 and the later ND6x. How do you you think the Neo versions would compare to your findings. Have you ever tried any of the slightly heavier / thicker diaphragms in them like the 84234XX or 84233XX depending on your needed impedance verses the standard 81256XX or 81320XX.
Re: High Frequency Compression Driver Evaluation
I don't know if HF drivers were included, but I remember hanging out at the Rat shop one time while Dave was working on Microwedge settings. We got onto the topic of drivers. Dave mentioned that drivers (I'm assuming cones) are audibly and measurably inconsistent from one to the next even when they're from the same run of manufacturing. Sometimes the differences are really noticeable. He and Brian Rat were surprised when they first made the discovery in the early days of Rat when they started building a lot of cabinets. I guess they're sort of like "a box of chocolates." Has that been your experience at all Art?
I don't know if HF drivers were included, but I remember hanging out at the Rat shop one time while Dave was working on Microwedge settings. We got onto the topic of drivers. Dave mentioned that drivers (I'm assuming cones) are audibly and measurably inconsistent from one to the next even when they're from the same run of manufacturing. Sometimes the differences are really noticeable. He and Brian Rat were surprised when they first made the discovery in the early days of Rat when they started building a lot of cabinets. I guess they're sort of like "a box of chocolates." Has that been your experience at all Art?
Re: High Frequency Compression Driver Evaluation
I just thought of something that may cause a slight measurement difference with the EV diaphragms. I have cut the diaphragm out of some of the back cap assemblies over the years. While most have about a 1/4 inch thick piece of foam glued to the inside of the cap a couple of them did not, just the hard plastic was exposed. If I can find any of those caps I'll check the serial numbers to see if there is some pattern to those with and with out. ( I have no idea why I keep old diaphragms!)
For what's it's worth the biggest failure I've seen with them is cracking in the surround at the point where the voice coil is glued to the diaphragm.
I just thought of something that may cause a slight measurement difference with the EV diaphragms. I have cut the diaphragm out of some of the back cap assemblies over the years. While most have about a 1/4 inch thick piece of foam glued to the inside of the cap a couple of them did not, just the hard plastic was exposed. If I can find any of those caps I'll check the serial numbers to see if there is some pattern to those with and with out. ( I have no idea why I keep old diaphragms!)
For what's it's worth the biggest failure I've seen with them is cracking in the surround at the point where the voice coil is glued to the diaphragm.
Re: High Frequency Compression Driver Evaluation
I compared the N/DYM1 to the DH1A about 20 years ago, as the specs show it had slightly smoother response and slightly less 3rd harmonic distortion than the DH1A.
I have not tried any other diaphragms in the DH1A.
Your observation about some diaphragms lacking foam fill would certainly explain a difference in sound.
Also, certain types of foam break down over time, a pile of foam dust in the bottom of the diaphragm would sound different than a 1/4" foam cover on the compression chamber.
Art
Mike,
I compared the N/DYM1 to the DH1A about 20 years ago, as the specs show it had slightly smoother response and slightly less 3rd harmonic distortion than the DH1A.
I have not tried any other diaphragms in the DH1A.
Your observation about some diaphragms lacking foam fill would certainly explain a difference in sound.
Also, certain types of foam break down over time, a pile of foam dust in the bottom of the diaphragm would sound different than a 1/4" foam cover on the compression chamber.
Art
Re: High Frequency Compression Driver Evaluation
Back in the "olden days" we used RTA for measurement, I only saved a few printouts, but there were differences in both cones and HF drivers, some from the factory, some over time from road use and abuse.
I have a lot of Eminence Alpha 8A and Lab 12 cones, they all measure remarkably consistent (within 1 dB) regardless of age purchased.
The Eminence PSD2002 and APT tweeters are not as consistent, with unit to unit variations of more than 3 dB.
When designing passive crossovers for those drivers, I have had to use an average between units.
To reach more consistency I matched and numbered the four pairs of APT tweeters used in my stage monitors, that way at least each pair will work together with one EQ.
Art
Greg,
Back in the "olden days" we used RTA for measurement, I only saved a few printouts, but there were differences in both cones and HF drivers, some from the factory, some over time from road use and abuse.
I have a lot of Eminence Alpha 8A and Lab 12 cones, they all measure remarkably consistent (within 1 dB) regardless of age purchased.
The Eminence PSD2002 and APT tweeters are not as consistent, with unit to unit variations of more than 3 dB.
When designing passive crossovers for those drivers, I have had to use an average between units.
To reach more consistency I matched and numbered the four pairs of APT tweeters used in my stage monitors, that way at least each pair will work together with one EQ.
Art
Re: High Frequency Compression Driver Evaluation
The JBL 2440/2441 drivers in my boxes are well aged and the foam inside the back covers is really old and crumbly. Low and behold, JBL still makes the foam! Picked up a set of new ones and I'm replacing them as I change out diaphragms over time. I suppose I should do a measurement of a before and after foam replacement and see if there's an improvement. I suspect there are some resonances that improve with the new foam.
The JBL 2440/2441 drivers in my boxes are well aged and the foam inside the back covers is really old and crumbly. Low and behold, JBL still makes the foam! Picked up a set of new ones and I'm replacing them as I change out diaphragms over time. I suppose I should do a measurement of a before and after foam replacement and see if there's an improvement. I suspect there are some resonances that improve with the new foam.
Re: High Frequency Compression Driver Evaluation
Wonder if the new foam is more stable than the old, foam surrounds for speakers have been vastly improved over the years.
The DH1A diaphragm and back chamber (with or without foam according to Mike Caldwell) are a one piece assembly, no way to get to the foam without cutting up the diaphragm.
Although I prefer the 3" diaphragm DH1A over the 4" JBL, being able to replace the foam is a good thing.
Wonder if the new foam is more stable than the old, foam surrounds for speakers have been vastly improved over the years.
The DH1A diaphragm and back chamber (with or without foam according to Mike Caldwell) are a one piece assembly, no way to get to the foam without cutting up the diaphragm.
Re: High Frequency Compression Driver Evaluation
I changed out the foam on 2 JBL drivers yesterday whilst replacing diaphragms on 2 TAD TD2001 drivers (ouch). I was in a hurry and didn't have time to setup measurement. I've got one more driver to change foam on so I'll do it then. One the JBLs was getting "kazooy" with sine wave so I put a new diaphragm in that one too. Radian JBL drop-ins are a heck of a lot cheaper than the TADs. I really which Radian would make diaphragms for those. Hear that Radian?! $100 is a lot cheaper than $550.
I changed out the foam on 2 JBL drivers yesterday whilst replacing diaphragms on 2 TAD TD2001 drivers (ouch). I was in a hurry and didn't have time to setup measurement. I've got one more driver to change foam on so I'll do it then. One the JBLs was getting "kazooy" with sine wave so I put a new diaphragm in that one too. Radian JBL drop-ins are a heck of a lot cheaper than the TADs. I really which Radian would make diaphragms for those. Hear that Radian?! $100 is a lot cheaper than $550.
Re: High Frequency Compression Driver Evaluation
Hi Art, is it your opinion that this is a driver distortion byproduct?
The 4552 still has a conical output, the same as any conventional driver. So kind of moot.
For line array BMS has a planar output driver with a 4"x1" exit, and true flat front wavefront, not just a conical exit driver mounted to a rectangular guide. 4510. It does use the same VC/membrane as the 4552, but in a much different configuration.
Regards, Jack
Hi Art, is it your opinion that this is a driver distortion byproduct?
The 4552 still has a conical output, the same as any conventional driver. So kind of moot.
For line array BMS has a planar output driver with a 4"x1" exit, and true flat front wavefront, not just a conical exit driver mounted to a rectangular guide. 4510. It does use the same VC/membrane as the 4552, but in a much different configuration.
Regards, Jack
Re: High Frequency Compression Driver Evaluation
Each driver tested varies from the original recording, the variance from the recording is the particular distortion "signature of the driver under test.
How would you describe the sound of the BMS drivers compared to the others in the test?
Did you get any answers from BMS regarding the questions I previously asked?
Art
Jack,
Each driver tested varies from the original recording, the variance from the recording is the particular distortion "signature of the driver under test.
How would you describe the sound of the BMS drivers compared to the others in the test?
Did you get any answers from BMS regarding the questions I previously asked?
Art
Re: High Frequency Compression Driver Evaluation
Hi Art,
First apologies for taking so long to reply. I was behind on something and would not do a comprehensive search till I finished.
As for method I used Praxis with stepped sine waves.
There is a huge difference between what you did and the data I have.
I collected Harmonic Distortion to see where I could put a crossover frequency. I never thought of using them in such a project as yours.
Mostly because I don’t get the wide sweep of drivers you tested.
About 2/3rds or more were BMS drivers on a variety of horns.
One of the favored drivers is the 4552ND (1” throat)
As for how valid my conclusions are, they are an impression I have come to over near a decade of working with BMS drivers and that driver in particular.
One of my glaring faults is the lack of skill in storing my data so that I can find them later if needed. As I said before the tests I did were done for a very different purpose and attention to detail may have been lost.
I do not recall throwing away distortion data for any of the tests I did, but I can not find more than one or two.
I did switch computers so all the data may be saved in my external back-up drive. That said it should still have found it in a search.
As time permits I will keep looking since it has become an irritation.
So in absence of solid data on my part we have you with data and me with a recollection that the BMS 4552ND did better at higher levels.
That married to a good horn and a very nice BMS 12” it sounded very nice indeed.
At near 60 years of age and many years of narcotic pain killers makes my memory less then reliable.
Thanks for the work.
Hi Art,
First apologies for taking so long to reply. I was behind on something and would not do a comprehensive search till I finished.
As for method I used Praxis with stepped sine waves.
There is a huge difference between what you did and the data I have.
I collected Harmonic Distortion to see where I could put a crossover frequency. I never thought of using them in such a project as yours.
Mostly because I don’t get the wide sweep of drivers you tested.
About 2/3rds or more were BMS drivers on a variety of horns.
One of the favored drivers is the 4552ND (1” throat)
As for how valid my conclusions are, they are an impression I have come to over near a decade of working with BMS drivers and that driver in particular.
One of my glaring faults is the lack of skill in storing my data so that I can find them later if needed. As I said before the tests I did were done for a very different purpose and attention to detail may have been lost.
I do not recall throwing away distortion data for any of the tests I did, but I can not find more than one or two.
I did switch computers so all the data may be saved in my external back-up drive. That said it should still have found it in a search.
As time permits I will keep looking since it has become an irritation.
So in absence of solid data on my part we have you with data and me with a recollection that the BMS 4552ND did better at higher levels.
That married to a good horn and a very nice BMS 12” it sounded very nice indeed.
At near 60 years of age and many years of narcotic pain killers makes my memory less then reliable.
Thanks for the work.
Re: High Frequency Compression Driver Evaluation
"That married to a good horn and a very nice BMS 12” it sounded very nice indeed."
Curtis, are you referring to our Bold Audio BA12 box?
Art, comparing any BMS driver with PSD2002, is really a joke to me. Maybe 2002 can go lower, but how loud can it go before the driver dies? Also that driver dont have any high end. I still have like 24 of those collecting dust somewhere in the shop. Those are the worst hf drivers i have ever heard in my life.
"That married to a good horn and a very nice BMS 12” it sounded very nice indeed."
Curtis, are you referring to our Bold Audio BA12 box?
Art, comparing any BMS driver with PSD2002, is really a joke to me. Maybe 2002 can go lower, but how loud can it go before the driver dies? Also that driver dont have any high end. I still have like 24 of those collecting dust somewhere in the shop. Those are the worst hf drivers i have ever heard in my life.
Re: High Frequency Compression Driver Evaluation
You are correct, the tests show the Eminence PSD 2002 goes quite a bit lower, but not as high as the BMS 4550 and 4552.
The series 1 diaphragm have a roll surround, the series 2 have a kind of rectangular oval pattern in the surround.
The series 2 diaphragm goes to about 15kHz (the series 1 about 12.5 kHz) but has rougher response.
I have to admit that most of what goes on above 12.5 kHz makes little difference to me, as 16 kHz unfortunately is the upper end of my hearing, and my sensitivity is quite a bit less above 12.5 kHz.
The PSD 2002 does require more EQ to get a flat response than the BMS drivers.
No joke, the comparisons show the bolt on PSD 2002 (with a series 1 diaphragm) can go louder with less distortion than the two BMS drivers tested.
The Eminence PSD 2002 survived some serious power in the tests I conducted, and I have had only one failure (and that was with the series 2 diaphragm) in many years of use. The Yamaha club series uses PSD2002 and does not seem to have any more problems with the driver dying than is usual for cheap cabinets used (and abused) by inexperienced operators.
Are your PSD 2002 thread on or bolt on, and what series diaphragm?
Listening to the BMS music and sine wave recordings, do you think the BMS drivers sounded better than the PSD 2002?
If so, what is it that sounds better or worse to you?
Art
Marjan,
You are correct, the tests show the Eminence PSD 2002 goes quite a bit lower, but not as high as the BMS 4550 and 4552.
The series 1 diaphragm have a roll surround, the series 2 have a kind of rectangular oval pattern in the surround.
The series 2 diaphragm goes to about 15kHz (the series 1 about 12.5 kHz) but has rougher response.
I have to admit that most of what goes on above 12.5 kHz makes little difference to me, as 16 kHz unfortunately is the upper end of my hearing, and my sensitivity is quite a bit less above 12.5 kHz.
The PSD 2002 does require more EQ to get a flat response than the BMS drivers.
No joke, the comparisons show the bolt on PSD 2002 (with a series 1 diaphragm) can go louder with less distortion than the two BMS drivers tested.
The Eminence PSD 2002 survived some serious power in the tests I conducted, and I have had only one failure (and that was with the series 2 diaphragm) in many years of use. The Yamaha club series uses PSD2002 and does not seem to have any more problems with the driver dying than is usual for cheap cabinets used (and abused) by inexperienced operators.
Are your PSD 2002 thread on or bolt on, and what series diaphragm?
Listening to the BMS music and sine wave recordings, do you think the BMS drivers sounded better than the PSD 2002?
If so, what is it that sounds better or worse to you?
Art
Re: High Frequency Compression Driver Evaluation
If the PDS2002 is in fact what's in a Yamaha Club Series, they sound decent at lower power but very quickly get harsh and brittle at higher volumes. Probably the same "grainy" effect Art noticed.
If the PDS2002 is in fact what's in a Yamaha Club Series, they sound decent at lower power but very quickly get harsh and brittle at higher volumes. Probably the same "grainy" effect Art noticed.