hi Edward
Could we have more info please?
This 18Sound driver is really a thing of beauty, both build and on paper. I have decided I am going to proceed with a pair of these.
I have been contemplating, as I read this thread, a downsize, condo friendly iteration of things. The wideband unit, and treble radiator will be mounted alone on 18 inch baffles, and I will figure out the bass later, likely using again the Ripol design, which worked really well with the DarkStars. (B200 + 2X Delta 15LF) I would be looking at a ~200Hz divide.
Bill Wood of YorkVille Sound fame had strongly recommended the B&C D250? c/d driver some time ago to me, calling it outstandingly smooth, musical, non harsh, it has a polyester diaphragm. I may choose this, and mount it to the 18Sound eliptical waveguide. However, for a bit more, the 18Sound drivers, with their radial arrayed Nd mini magnets look like a serious step upward, thoughts on this are appreciated. Also they both avoid metal diaphragms.
I dont know how many of you are familiar with the software based www.thuneau.com crossover products. I think something like this is the way to go, if you wish to avoid Behringer "quality" and the need to blow large cash on the Rane stuff.
Opinions on this are welcome at this time.
Could we have more info please?
This 18Sound driver is really a thing of beauty, both build and on paper. I have decided I am going to proceed with a pair of these.
I have been contemplating, as I read this thread, a downsize, condo friendly iteration of things. The wideband unit, and treble radiator will be mounted alone on 18 inch baffles, and I will figure out the bass later, likely using again the Ripol design, which worked really well with the DarkStars. (B200 + 2X Delta 15LF) I would be looking at a ~200Hz divide.
Bill Wood of YorkVille Sound fame had strongly recommended the B&C D250? c/d driver some time ago to me, calling it outstandingly smooth, musical, non harsh, it has a polyester diaphragm. I may choose this, and mount it to the 18Sound eliptical waveguide. However, for a bit more, the 18Sound drivers, with their radial arrayed Nd mini magnets look like a serious step upward, thoughts on this are appreciated. Also they both avoid metal diaphragms.
I dont know how many of you are familiar with the software based www.thuneau.com crossover products. I think something like this is the way to go, if you wish to avoid Behringer "quality" and the need to blow large cash on the Rane stuff.
Opinions on this are welcome at this time.
EdwardWest said:
A friend of mine and I purchased 4 of the 8NMB420's last month from Universal Music LLC in Miami, FL.
No problem, he called them with a credit card number and they were on a truck in two-days. I don't know how complete the inventory is, but they've got the 8NMD420's
Edward
Well what the heck...I emailed them and no response. Phoned them today but they were probably already closed. I'll try again tomorrow. Big thanks for the tip Edward!
Hi
Edward, could you - or your friend - do a quick CSD measurement on the 8NMB420 and post it here ?
I did search around but not many measurements are available for these drivers.
Its pretty easy to do CSD with ARTA and any reasonable mic AND it does not have to be perfect.
http://www.fesb.hr/~mateljan/arta/
Other 18Sound candidates I am interested in are the 10NDA610 and the 12NDA520 if anyone already has one in use.
All those 18Sound drivers are really "speedy" and have lots of displacement volume.
In the case of the 12NDA520 this one is capable of 110 dB down to 75 Hz in OB according to the SL spreadsheet for example.
Greetings
Michael
EdwardWest said:
A friend of mine and I purchased 4 of the 8NMB420's last month from Universal Music LLC in Miami, FL.
No problem, he called them with a credit card number and they were on a truck in two-days. I don't know how complete the inventory is, but they've got the 8NMD420's
Edward
Edward, could you - or your friend - do a quick CSD measurement on the 8NMB420 and post it here ?
I did search around but not many measurements are available for these drivers.
Its pretty easy to do CSD with ARTA and any reasonable mic AND it does not have to be perfect.
http://www.fesb.hr/~mateljan/arta/
Other 18Sound candidates I am interested in are the 10NDA610 and the 12NDA520 if anyone already has one in use.
All those 18Sound drivers are really "speedy" and have lots of displacement volume.
In the case of the 12NDA520 this one is capable of 110 dB down to 75 Hz in OB according to the SL spreadsheet for example.
Greetings
Michael
dmason said:
What additional information were you hoping to get?
augerpro said:
Our order did not require any significant effort, so just try calling a few times - should work out fine.
mige0 said:
I have done a basic measurement of the speakers that we ordered - 2 ft, on-axis, free-air. The purpose was to complete a quality check and determine if the four drivers behaved the same. I determined that they all worked fine, and three of the four has an almost identical HF roll-off behavior. The odd-ball had a similar shaped response with a couple-hundred hertz shift in the feature frequencies.
Further measurements are on my to-do list for this project. When I complete the CSD measurements I would be happy to post them here. Realistic time-frame for these measurements could be as much as 3-4 weeks - but I'll post them as soon as I get them.
Edward
Hi
Edward, great I am looking forward to your measurement !
Anyone who has or can point to a CSD measurement of the Beyma 605ND ?
Its a pure midrange ( ~ 110dB above 300 Hz in OB ) and about 20% less " speedy " than the 18Sound's but has EXCELLENT Qms and extended upper frequency response .
Greetings
Michael
EdwardWest said:
Edward, great I am looking forward to your measurement !
Anyone who has or can point to a CSD measurement of the Beyma 605ND ?
Its a pure midrange ( ~ 110dB above 300 Hz in OB ) and about 20% less " speedy " than the 18Sound's but has EXCELLENT Qms and extended upper frequency response .
Greetings
Michael
Someone in the german "HIFI-FORUM" posted some measurements of the 8NMB420
http://www.hifi-forum.de/viewthread-104-9228.html
http://www.hifi-forum.de/viewthread-104-9228.html
Hi
Jogi59, thanks for the link! Christoph Gebhard did a great job there.
CSD looks pretty good even at cone brake up and the deviations in FR to the original datasheet might be due to the baffle size used.
Harmonics are VERY interesting as I would have expected K2 to be at least 10 dB less due to the faraday rings. K3 dropping above 1 kHz is nice to have though. Higher harmonics are pretty low as well.
I was considering this driver as well but " drive " and Qms are not so hot compared to some other 18Sound or neo- Beymas.
Greetings
Michael
jogi59 said:
Jogi59, thanks for the link! Christoph Gebhard did a great job there.
CSD looks pretty good even at cone brake up and the deviations in FR to the original datasheet might be due to the baffle size used.
Harmonics are VERY interesting as I would have expected K2 to be at least 10 dB less due to the faraday rings. K3 dropping above 1 kHz is nice to have though. Higher harmonics are pretty low as well.
I was considering this driver as well but " drive " and Qms are not so hot compared to some other 18Sound or neo- Beymas.
Greetings
Michael
dmason said:
What advantage does the 18Sound 8NMB420 hold over the B&C 8NDL51?
I used the B&C as midranges along with JBL compression drivers in my old Honda Accord. They're fantastic midranges. I have measurements of the setup over on AudioGroupForum.com. I wrote about them in a few threads over there; here's one.
For my current project I am using the 18sound elliptical waveguide you mentioned, along with a BMS compression driver, a Dayton midbass and Audax woofers.
Thanks for the 8NMB420 specs!
The 2nd harmonic rise at 3.2 kHz, combined with a fair amount of CSD energy storage at the same frequency, strongly indicates the use of a steep notch filter regardless of the rest of the crossover topology. It also looks like use above 2 kHz isn't a good idea, again based on a fairly steep rise in distortion starting at 1.8 kHz and increasing CSD energy storage in the same region. I agree that data of this quality for the 10NDA610 and the 12NDA520 would be most interesting.
Integrating the B&C 8NDL51 with a ribbon crossed at 1.8 kHz looks like it would require two notch filters, one right at the crossover frequency (very awkward) and another somewhere between 2.8 and 3.5 kHz. My experiences with multiple notch filters have not been positive - tuning all of them against an electromechanical system that is working its way into breakup isn't easy or simple. I suspect in professional use they simply use active 24 dB/octave crossovers set at 1.2 kHz or lower, and just dump the troublesome region into the reject band.
Since pro drivers are typically designed for active crossovers with very sharp slopes, I surmise less attention is paid to controlling resonances and breakup in the out-of-band region. The ultra-high-priced exotics don't really distinguish themselves here either - whizzers certainly don't help, that's for sure. At least those dreadful whizzers aren't used in the pro world.
The reason I'm going on about these peaks is they not only concentrate distortion, they tend to be quite directional, which defeats equalization and makes time compensation, even in the digital realm, counterproductive. The pro approach of steep filtering has its issues as well - the colorations are attenuated, true, but they are certainly not reduced to zero, and tend to pop in and out of audibility depending on program level and spectral content. Play massed choral at symphonic levels and you'll hear the resonant colorations come and go in a very disturbing and annoying way.
The 2nd harmonic rise at 3.2 kHz, combined with a fair amount of CSD energy storage at the same frequency, strongly indicates the use of a steep notch filter regardless of the rest of the crossover topology. It also looks like use above 2 kHz isn't a good idea, again based on a fairly steep rise in distortion starting at 1.8 kHz and increasing CSD energy storage in the same region. I agree that data of this quality for the 10NDA610 and the 12NDA520 would be most interesting.
Integrating the B&C 8NDL51 with a ribbon crossed at 1.8 kHz looks like it would require two notch filters, one right at the crossover frequency (very awkward) and another somewhere between 2.8 and 3.5 kHz. My experiences with multiple notch filters have not been positive - tuning all of them against an electromechanical system that is working its way into breakup isn't easy or simple. I suspect in professional use they simply use active 24 dB/octave crossovers set at 1.2 kHz or lower, and just dump the troublesome region into the reject band.
Since pro drivers are typically designed for active crossovers with very sharp slopes, I surmise less attention is paid to controlling resonances and breakup in the out-of-band region. The ultra-high-priced exotics don't really distinguish themselves here either - whizzers certainly don't help, that's for sure. At least those dreadful whizzers aren't used in the pro world.
The reason I'm going on about these peaks is they not only concentrate distortion, they tend to be quite directional, which defeats equalization and makes time compensation, even in the digital realm, counterproductive. The pro approach of steep filtering has its issues as well - the colorations are attenuated, true, but they are certainly not reduced to zero, and tend to pop in and out of audibility depending on program level and spectral content. Play massed choral at symphonic levels and you'll hear the resonant colorations come and go in a very disturbing and annoying way.
Attachments
Lynn, this fellow has an idea reminiscent of something I think I read on your Nutmeg site.
http://www.diyaudio.com/forums/showthread.php?s=&postid=1339644#post1339644
This would make an interesting OB.
http://www.diyaudio.com/forums/showthread.php?s=&postid=1339644#post1339644
This would make an interesting OB.
Hi
FrankWW. two things these digital speaker guys seem to forget
a) speed
b) reconstruction filter
a)
I haven't calculated in detail yet but which real world speaker you think is " speedy " enough to jump form idle state to max SPL in lets say 1 /100th of the sampling frequency ( at 44.1 kHz = 200 nsec ) ?
Even more difficult:
which real world speaker you think is capable to come back form max excursion to quietness in zero position in this time window ?
Not to mention that this speakers would have to have sort of DC SPL capability ( continuous air compression ).
b)
But even IF you could manage the " speed " and DC requirement you MUST HAVE sort of reconstruction filter afterwards . This can't be the upper frequency limit of the speaker itself as easily seen in point a)
Greetings
Michael
FrankWW said:
FrankWW. two things these digital speaker guys seem to forget
a) speed
b) reconstruction filter
a)
I haven't calculated in detail yet but which real world speaker you think is " speedy " enough to jump form idle state to max SPL in lets say 1 /100th of the sampling frequency ( at 44.1 kHz = 200 nsec ) ?
Even more difficult:
which real world speaker you think is capable to come back form max excursion to quietness in zero position in this time window ?
Not to mention that this speakers would have to have sort of DC SPL capability ( continuous air compression ).
b)
But even IF you could manage the " speed " and DC requirement you MUST HAVE sort of reconstruction filter afterwards . This can't be the upper frequency limit of the speaker itself as easily seen in point a)
Greetings
Michael
Since this is becoming a reference dipole thread...
I have questions regarding diffraction and reflections on a wide baffle.
If the entire baffle surface is curved instead of flat, how much can this affect diffraction?
If a curved surface can help eliminate diffraction for a midrange and tweeter, how do you calculate a radius that will do this?
I ask because the R909 baffle surface is obviously radiused for an acoustic reason, not just an aethetic one. A wide flat baffle with rounded edges will still have reflection problems through the midrange.
Any help is appreciated,
C
p.s. I have attached a concept picture that is an alternative to the wide flat rectangular baffle. Comments?
I have questions regarding diffraction and reflections on a wide baffle.
If the entire baffle surface is curved instead of flat, how much can this affect diffraction?
If a curved surface can help eliminate diffraction for a midrange and tweeter, how do you calculate a radius that will do this?
I ask because the R909 baffle surface is obviously radiused for an acoustic reason, not just an aethetic one. A wide flat baffle with rounded edges will still have reflection problems through the midrange.
Any help is appreciated,
C
p.s. I have attached a concept picture that is an alternative to the wide flat rectangular baffle. Comments?
Attachments
From FRD-BDS simulations I found a radius of 50mm - 100mm to be suitable for normal baffle widths from 150mm to 300mm with a crossover point around 2-3kHz. Think of wavelengths. A smaller radius would only have an effect on higher frequencies but at those frequencies tweeters beam so round edges have very little effect. A larger radius is unnecessary because below 2kHz the midwoofers play a dominent role and their larger cone areas (think of distances of sound sources from the edges) would make diffraction to be a non-issue.
I selected 70mm radius for my new U-frame OB speaker. the FRD-BDS simulations show the baffle diffraction to be very smooth. With a proper XO, I can get to +/-0.2dB or even less from 1kHz up provided that the drivers are ruler flat, in constrast to a sharp edge baffle that usually exhibites up to +/-2dB from 1kHz up.
Note that all of these are based on on-axis response and my guess is that for rounded edges the off-axis response will also be a lot smoother.
Regards,
Bill
I selected 70mm radius for my new U-frame OB speaker. the FRD-BDS simulations show the baffle diffraction to be very smooth. With a proper XO, I can get to +/-0.2dB or even less from 1kHz up provided that the drivers are ruler flat, in constrast to a sharp edge baffle that usually exhibites up to +/-2dB from 1kHz up.
Note that all of these are based on on-axis response and my guess is that for rounded edges the off-axis response will also be a lot smoother.
An externally hosted image should be here but it was not working when we last tested it.
Regards,
Bill
Re: Since this is becoming a reference dipole thread...
If I were you, I would start a new thread on the topic of diffraction, and see if you can get the attention of Dr Geddes. He lives for this stuff, there is absolutely no one in the world who's put more thought into the subject of diffraction. And lucky for us, he posts here. We were talking about his Summa speakers one day, and he mentioned that a HOUSEPLANT near the speaker was causing diffraction effects! Can you imagine that?
Are you sure you're approaching this problem from the right perspective?
As I see it, the WIDTH of the baffle and it's TERMINATION are the primary concerns.
Here's why:
The width of the baffle will cause a frequency response dip based on the frequency that's equivalent to the width. For instance, with a 12" wide baffle response will be down 3db at 380hz. (Olson's formula from trueaudio.com.)
:: BUT THERE'S A CATCH ::
That formula doesn't take TERMINATION into account. If you use a SERIOUS round-over, the transition is MUCH gentler.
That's why the Summa's have a two-inch roundover on all edges, which makes the cabinet expensive and difficult to manufacture.
Make sense?
In my Big Audio Dynamite Thread I am using a 2in roundover for my dipoles also.
chrismercurio said:
If I were you, I would start a new thread on the topic of diffraction, and see if you can get the attention of Dr Geddes. He lives for this stuff, there is absolutely no one in the world who's put more thought into the subject of diffraction. And lucky for us, he posts here. We were talking about his Summa speakers one day, and he mentioned that a HOUSEPLANT near the speaker was causing diffraction effects! Can you imagine that?
Are you sure you're approaching this problem from the right perspective?
As I see it, the WIDTH of the baffle and it's TERMINATION are the primary concerns.
Here's why:
The width of the baffle will cause a frequency response dip based on the frequency that's equivalent to the width. For instance, with a 12" wide baffle response will be down 3db at 380hz. (Olson's formula from trueaudio.com.)
:: BUT THERE'S A CATCH ::
That formula doesn't take TERMINATION into account. If you use a SERIOUS round-over, the transition is MUCH gentler.
That's why the Summa's have a two-inch roundover on all edges, which makes the cabinet expensive and difficult to manufacture.
Make sense?
In my Big Audio Dynamite Thread I am using a 2in roundover for my dipoles also.
Re: Re: Since this is becoming a reference dipole thread...
I don't get it. I house plant ( or other artifacts in the playback causing diffraction ) is deterimental to the sound, but score stands, chairs etc. on the stage, or the seats around you in the auditoriom are not?
Patrick Bateman said:
I don't get it. I house plant ( or other artifacts in the playback causing diffraction ) is deterimental to the sound, but score stands, chairs etc. on the stage, or the seats around you in the auditoriom are not?
Re: Re: Since this is becoming a reference dipole thread...
Well, if you consider that objects that cause reflection that radiates into a wider angle diffraction, I think anything that has a dimention smaller than 30cm could caus diffraction of some sort that is measurable.Patrick Bateman said: