OffTopic (Drive Units)
by Jose Hidalgo 
, Wednesday, April 18, 2007, 17:41 (6208 days ago)
Just a reminder for Bert, if he comes across this topic. I'd like an answer to the following questions please :
1°) Regarding the enclosures, your BR enclosures would suit us well. However, I have noticed (WinIsd) that a big BR enclosure (165L or more) will create a lot of group delay under 60 Hz, while allowing us to gain very few SPL (which we don't want since we're already over 105). Moreover, the Xmax of the BD15 (6mm, is it right ?) will be exceeded before 30 Hz in that case. A smaller enclosure (120L ?) would allow us to have less group delay, at the price of a single dB @ 30 Hz (104 instead of 105 - big deal 
), and with an Xmax exceeded well under 30 Hz. Wouldn't that be better for us ? Or do you see other problems with a smaller enclosure ?
2°) One last question : does someone have some measurement graphs for the DB15 ? We'd really like to have a look at the response, distorsion and impedance graphs for instance. I hope it's possible. Thanks in advance.
Thanks in advance / Jose
OffTopic
by Bert , Wednesday, April 18, 2007, 18:23 (6208 days ago) @ Jose Hidalgo
Jose,
Just a reminder for Bert, if he comes across this topic. I'd like an
answer to the following questions please :
Sorry, missed that one while the "war" started in that topic. Somehow the new messages posted within that topic doesn't show on the threaded topics list....the reason for moving your questions to a new topic.
1°) Regarding the enclosures, your BR enclosures would suit us well.
However, I have noticed (WinIsd) that a big BR enclosure (165L or more)
will create a lot of group delay under 60 Hz, while allowing us to gain
very few SPL (which we don't want since we're already over 105). Moreover,
the Xmax of the BD15 (6mm, is it right ?) will be exceeded before 30 Hz in
that case. A smaller enclosure (120L ?) would allow us to have less group
delay, at the price of a single dB @ 30 Hz (104 instead of 105 - big deal
better for us ? Or do you see other problems with a smaller enclosure ?
Xmax is 7mm. If you would build a dampened reflex enclosure then the group delay isn't so bad.... the bigger enclosure gives a nice gradual roll-off which can be EQ-ed more simple and less strong (saving some power on the amps).
2°) One last question : does someone have some measurement graphs for the
DB15 ? We'd really like to have a look at the response, distorsion and
impedance graphs for instance. I hope it's possible. Thanks in advance.
I never did any distortion plots on the BD15's so I can't help you with that. I am sure that they will give a lot of second harmonic distortion when they are moving a lot...
My ears made the selection for the used paper cone, stiffness, surround, spider, coil (and former) and magnet strength. I have had several prototypes here and the BD15 came out most balanced in terms of audible distortion and dynamical behaviour related to the Q, etc.
Bert
--
BD-Design - Only the Best!
OffTopic
by Jose Hidalgo , Wednesday, April 18, 2007, 18:50 (6208 days ago) @ Bert
Thanks Bert. You finally saw my post ! :wink:
Xmax is 7mm.
If Xmax is 7mm, then either Vd is 599 (not 513), or Sd is 733. So I'll take that Vd is 599. Maybe you can change that in BD15's technical data ?
If you would build a dampened reflex enclosure then the group
delay isn't so bad.... the bigger enclosure gives a nice gradual roll-off
which can be EQ-ed more simple and less strong (saving some power on the
amps).
Understood. So you advice some dampening. Just FYI, I had heard other people advisind not to dampen bass drivers at all.
I never did any distortion plots on the BD15's so I can't help you with
that. I am sure that they will give a lot of second harmonic distortion
when they are moving a lot...
My ears made the selection for the used paper cone, stiffness, surround,
spider, coil (and former) and magnet strength. I have had several
prototypes here and the BD15 came out most balanced in terms of audible
distortion and dynamical behaviour related to the Q, etc.
Yes, I do understand, and I'm quite convinced that the BD15 is one of the top drivers ahead of the rest. No problem about that. Still I think it would do justice to the BD15 if you think about doing some measuring one day. No offense intended of course.
The real problem is that for a new customer like me it's very difficult to actually hear a BD15 (it remains a quite confidential driver and we can't find it in stores other than yours, can we ? ). That means we often have to choose it without actually hearing it. :shame: And for that, well, at least a bit more technical documentation with some measuring would be good. The small BD15 PDF really lacks some information IMHO. That's a pity because an excellent driver really deserves a good documentation, don't you think ? (well, maybe you don't... ).
Hey, maybe one of the current BD15 owners and would be able to do some measuring so that everyone can benefit from it ? That would surely be very nice (at least it would be better than nothing). IMHO of course.
Just my two cents...
OffTopic
by PeterSt. 
, Netherlands, Wednesday, April 18, 2007, 21:17 (6208 days ago) @ Jose Hidalgo
edited by unknown, Wednesday, April 18, 2007, 21:26
Hi Jose, and Eddie,
First of all, don't laugh ...
Because of my more or less technical viewing (say, equalling your "monitor" listening Jose), I can advise you to draw Musicality (Prince) which is (so far) the only CD pulling the BD15 to this 7 mm mentioned. Even at lower levels (btw, second track and further). Why ? well, because of the "square" synth bass coming from the CD, that being output like that with the proper playback means (start with a nos-DAC).
I mention above, because in all other music the BD15 hardly moves (4mm forth/back all together), and I can confirm this by usually playing at 90dB as low average point at 4m distance ...
Also, the situation Eddie mentiones was a kind of crazy one, proving that at that level -in a (estimate) 50m3 room- even bass waves would not interfere with eachother. And they didn't. However, that level (and I was there too) overdrove the 7W tube amp we used in the highest regions, so it did not sound comfortable anymore. Not because of distortion as you might expect, but because of sheer clipping of the amp.
For Eddie : lateron we confirmed this by running the same crazy "square clicks" on my amps, and at Bert's at lower levels, where the clicks now had a tune/tone which we did not hear back then.
The most important thing Jose, is even at that levels in *my* 290 m3 room, there's hardly excursion from the BD15 drivers. For that matter, do not expect too much doppler distortion.
And as said earlier (in a probably by me deleted post), my BD15 165L cabs measure straight to 26,5 Hz (the volume of the room contributing to that).
I can't measure distortion levels though ...
HTH,
Peter
Edit : With "bass waves would not interfere with eachother" I meant : the individual vibes of a e.g. a bass guitar were at the high SPL still as audible as at normal levels. This test was about something else, but showed anyway the tight control of the drivers.
OffTopic
by Eddie , Wednesday, April 18, 2007, 20:01 (6208 days ago) @ Jose Hidalgo
Hello Jose,
A while ago I measured the response of my BD-15's that are in a 165 ltr. bass reflex box whith very little damping material inside but with very heavy walls and a few braces. I measured at the listening position with a professional Breul&Kjaer instrument. The -3 dB point was at 29 Hz with a quite steep roll-off to lower frequencies, I guess at least second order. I think that this is related with my room size which gives me a lowest resonance of about 30 Hz. At higher frequencies I also see quite strong room effects leading to sharp peaks and dips in the response. So the room is quite important and yours will be different from mine.
What I also found out is that I listen in the evening to an average sound level of 70 dB with peaks of up to 80 dB and I find that adequate and pleasing despite the fact that my ears already lost part of their sensitivity. Last month at Bert place we listened to the Swings at 106 dB for a few minutes. It was very impressive how clean and undistorted the sound was at this level, but for me it was much too loud to listen comfortably to music.
Kind regards,
Eddie
OffTopic
by Jose Hidalgo , Wednesday, April 18, 2007, 20:54 (6208 days ago) @ Eddie
Thanks Eddie, that's a very interesting comment (although most of it is subjective of course). It's interesting to see that a pair of BD15's can easily go below 30 Hz without major problems (and we expect even better results with our active crossover).
For the listening experience @ 106dB, I'll take that into account, but it would be so much more self-speaking if we could find a way to get some distorsion graphs one day... let's cross fingers !
OffTopic
by Bert , Wednesday, April 18, 2007, 22:00 (6208 days ago) @ Jose Hidalgo
Hi Jose,
For the listening experience @ 106dB, I'll take that into account, but it
would be so much more self-speaking if we could find a way to get some
distorsion graphs one day... let's cross fingers !
If all only depends on measurements to decide then do not buy them and find another candidate elsewhere. I do not care about measurements or even highly rated reviews either. Neither do I need to sell thousands of the BD15's and fishing all the time for plots is only pushing me further away from that topic.
I scheduled to do some measurements at the end of this week but suddenly more important things to do showed up and I have only two hands to work with.
Bert
--
BD-Design - Only the Best!
Frustation...
by Bert , Wednesday, April 18, 2007, 22:59 (6208 days ago) @ Jose Hidalgo
Jose,
Sorry for the "rant" in my previous answer, you are not the first one with a computer trying to design a loudspeaker, asking for thoughts and then argue with software telling you different stories... why bothering asking then?
This is not an excuse but merely to explain that I have had enough discussions about this in the past leading to nowhere in the end (similar situation as talking about Foobar on this forum...).
You have set your mind to do the things your way, no problem with that but it is NOT the way I would design speakers these days simply because computers, simulations and measurements only show the things they are able to show and that is just limited information compared to all the things we are able to hear!
Bert
--
BD-Design - Only the Best!
Frustation...
by PeterSt. , Netherlands, Wednesday, April 18, 2007, 23:53 (6208 days ago) @ Bert
edited by unknown, Thursday, April 19, 2007, 08:58
But Bert ...
The way Jose anounced himself is really not different from how I am.
To you (and possibly to you all out there) I am this theoretical over the top freak just the same.
I must "admit" though, that it needs a kind of adoptiveness to the mystiqueness of audio to behave in your circles (which are mine obviously), and once you come from - what I name "hydrogen" communities, it is very hard to be taken serious overhere.
If I would post on Hydrogen, I would be banned right after the first post (and that's not because of deleting it :no
.
I know you mean well Bert, but your last post sounds even more harsh to me than Foobar (yea, pun intended). And, *of course* this is not to put you on the right track (who am I), but merely because of I think Jose just means well just the same.
And Jose, knowing Bert, he will not put out distortion graphs or anything, because in the end it is really not about that. I can tell you, Bert is not about selling, just as I am not in my own company. I only sell to people when the "click" is there. So the implied "take it or leave it" sounds very familiar to me.
Last thing for now : I can tell you that "we" are kind of fed up with buying stuff with good graphs. They s*ck anyway. This world is full of faking.
I dare to say that everything put out in this forum is not put out because those who say something copied it from the internet. Otoh it might be subjective obviously. But genuin.
Piece, edit : djeezz, peace !
Peter
Frustation...
by Jose Hidalgo , Thursday, April 19, 2007, 02:10 (6208 days ago) @ Bert
edited by unknown, Thursday, April 19, 2007, 02:24
@PeterSt : thanks for that extensive post. I found it very interesting to read (you have a 290m3 room ? wow !).
And Jose, knowing Bert, he will not put out distortion graphs or anything,
because in the end it is really not about that.
Yes, I can understand. At least I have given my humble opinion (who am I also... nobody), and Bert has answered me. That's the most important.
I can tell you, Bert is not about selling, just as I am not in my own
company. I only sell to people when the "click" is there. So the implied
"take it or leave it" sounds very familiar to me.
Yes, I understand too. I had seen that. Bert is probably more a passionate than a salesperson, isn't it ? :wink:
Last thing for now : I can tell you that "we" are kind of fed up with
buying stuff with good graphs. They s*ck anyway. This world is full of
faking.
Yes, sure. But how can we do ??? If we caNot listen to a given speaker (are there any BD15 owners in the south of France ?), then T/S and graphs are all that's left for us... 
----------------------------------------
@Bert : don't worry, I understand your rant, everything's OK. I didn't mean to push you : I respect you very much, and I respect all the work you do, which is obviously awesome according to the unanimous comments you get. I'd just like to explain this to you once, and if you don't agree that won't be a problem, I'll keep respecting you just the same. :wink: So, here it is :
Me and my small team of friends (I could do almost nothing alone 
) need to choose a high-end driver for our application, and we need to choose it together. So like I said, we have searched almost everywhere. We have found very few good candidates (probably 3-4, not more), and to sum it up in the final shorlist we have the BD15, the TADs and something from JBL (there's also Altec and Iconicspkrs, but I don't think they'll fit the bill so let's leave them aside).
How can we choose between these drivers ? If we could listen to all of them in the same exact listening conditions, that would be easy. But of course it's impossible.
At this very moment, in other forums (DIYaudio, AVS, madisound...), we have people telling us "buy TAD, it's monitor stuff, you can't be disappointed". We have other people telling us "buy JBL, it's pro gear, you can't get better". We have also people telling us "buy BD-Design, it's totally awesome"... and people telling us "BD WHAT ? Never heard of that before". You get the point.
I, personally, have a preference for the BD15 (otherwise I wouldn't be here). But this preference is completely subjective / irrational. I've never heard a BD15 (how could I ?), and ALL I'VE GOT at the moment is that tiny little PDF with some lines of text and some pretty good T/S stuff. So how can I explain my personal preference to the rest of the team ?
Please try to put yourself in my situation : how could YOU seriously choose a driver that you don't know AT ALL (I didn't know the existence of the BD15 one month ago), simply by reading a small PDF with not much information ?
Of course there are all the wonderful comments on this forum. But like I said, there are other people in other forums telling us to buy other brands. Not easy to decide for all of us...
So that's my problem right now. If I were the only one to decide I'd probably buy a couple BD15's right now, just to try them out and see. But I'm not the only one. So in fact, all I'm asking is some kind of HELP so that I can positively influence the rest of the team, and convince them to take a small risk on buying a speaker without even seeing it before.
I hope you understand. It's not only for the measuring thing. I'm just asking for a bit of help, if it's possible. I'll do my best either way, and maybe we'll buy a pair of BD15's whatever happens. I just don't know yet. Thanks for your understanding. :wink:
Frustation...
by Bert , Thursday, April 19, 2007, 09:06 (6207 days ago) @ Jose Hidalgo
Jose,
How can we choose between these drivers ? If we could listen to all of
them in the same exact listening conditions, that would be easy. But of
course it's impossible.
Thanks you for your understanding. My frustation was probably enhanced by the T-amp "pushing" me the music last evening...
Best way to decide which driver suits your and your friends needs is to buy them all and listen to them yourself. If the drivers are well "reviewed" then it will not be a problem to re-sell the ones you do not need.
The same as I did (spending money on amps) just to hear and test these myself objectively to hear if one of these would suit me better than the ones I am using now. It turned out that measurements, highly rated reviews and that kind of sh*t prooved again that this world is only about money and people who do not have any clue.
Please try to put yourself in my situation : how could YOU seriously
choose a driver that you don't know AT ALL (I didn't know the existence of
the BD15 one month ago), simply by reading a small PDF with not much
information ?
For me it is abit the other way around. The BD15's have my logo (just visible, not "screaming") on the dome, how can I trust you and your friends to create a perfect sounding system? If it doesn't then who is to blame for that....me?
It is not about collecting the best parts available, it is the art to have all things work together and there is no computer who can calculate all needed parameters for you.
I hope you understand. It's not only for the measuring thing. I'm just
asking for a bit of help, if it's possible. I'll do my best either way,
and maybe we'll buy a pair of BD15's whatever happens. I just don't know
yet. Thanks for your understanding. :wink:
I understand and I can help giving some suggestions but not with measurements. Sure, I can make plots like all manufacturers do but those do not mean anything!!!!!
You work with computers so you should know that all manufacturers are able to manipulate their given information. So, again listen to them and measure them all yourself so that you see and hear the truth with your own eyes and ears before you decide which driver will fit best in your system.
Bert
--
BD-Design - Only the Best!
OffTopic
Hi Jose
As you see, you got almost all the questions answered that the BD15's are among the best, if not "THE" best. All quotes of course in relative senses as no one once they heard the drivers would be interested in how it meassures, but just enjoys it's fantastic performance.
I have a meassuring curve of the BD15's which shows that it beats all your mentioned alternatives in each diciplin. (I have some older meassurements of your alternatives laying around here and can compare).
I will not post that meassurement, as it is really up to Bert to do that if he should want it.
But I can tell you that it starts low enough to move air and has an expectable amplitude, but incredible linear, rise within + - nothing up to 5 kHz where it smoothely roll's off without breakups.
Now you know that and you also know it is able to move m3's of air into earthquake like airshaking waves without noticeable distortion or reaching it's P-P limits.
Maybe you were not told how incredible fast this drivers is as per it's low Mms and powerfull magnet motor.
The driver is just wonderful and as you were also adviced, buy that first and simply forget the rest of the candidates. Or do as I would have done i your situation, buy them all and test them out. :wink:
GC