Precision devices

[Geenius]

Originally posted by derf
.........How long have you been playing?

Just over 25 years of which the first 10 only on bass-guitar

[paulspencer]

Is that a double bass I see there?

There's nothing like acoustic double bass, I just recently bought a Dianna Krall live in paris DVD just to hear the double bass! Although, sadly, it revealed that the bass from my mains is far better than my subs

I'm keen on trying dipole bass properly as I'm convinced its the only kind that will really satisfy me as getting the most accurate bass I can get, especially for double bass!

One thing I'm curious about is how large PA drivers compare to some of the better subs with shorting rings and/or XBL2 or competing technologies, when it comes to accuracy.

How big are those PD drivers? The magnet looks huge!

[Geenius]

Originally posted by paulspencer
Is that a double bass I see there?

There's nothing like acoustic double bass, I just recently bought a Dianna Krall live in paris DVD just to hear the double bass! Although, sadly, it revealed that the bass from my mains is far better than my subs

I'm keen on trying dipole bass properly as I'm convinced its the only kind that will really satisfy me as getting the most accurate bass I can get, especially for double bass!

One thing I'm curious about is how large PA drivers compare to some of the better subs with shorting rings and/or XBL2 or competing technologies, when it comes to accuracy.

How big are those PD drivers? The magnet looks huge!

Yep that's a double bass, 3/4 size German model from the late 1960's.

The PD's are 21" woofers. Fs is 22Hz and Sd 1630cm2 each. Xmax is 12mm and the displacement limit is stated to be 38mm. BL is a huge 34,28T/m.

I owned a Velodyne DD15 before this but always had the impression it sounded like a large heavy cone in a small box. It went flat down to 15Hz, great for popular music and home theatre but being a fan of classical music and jazz I was never completely happy with it.

[paulspencer]

Tony, there's nothing quite like double bass. I once heard a local band which had a double bass, seeing them live the bass player used a bow (which I hadn't ever seen before) and I was impressed!

The PD's are 21" woofers. Fs is 22Hz and Sd 1630cm2 each. Xmax is 12mm and the displacement limit is stated to be 38mm. BL is a huge 34,28T/m.

WOW!

12mm one way xmax?

I owned a Velodyne DD15 before this but always had the impression it sounded like a large heavy cone in a small box. It went flat down to 15Hz, great for popular music and home theatre but being a fan of classical music and jazz I was never completely happy with it.

I'm surprised to hear that. I've never heard a velodyne. It's a servo sub? I would have thought that it would work well for jazz as well. So you like the PD much better?

[Geenius]

Originally posted by paulspencer
12mm one way xmax?

The voice-coil winding depth is 30mm and the magnet gap height 15mm's. That would be 15mm peak-peak displacement, PD state 12mm Xmax but I'm not sure if that is one way or peak-peak. But with all that cone area the air displacement should be enough even if it is only 6mm one way.

I'm surprised to hear that. I've never heard a velodyne. It's a servo sub? I would have thought that it would work well for jazz as well. So you like the PD much better?

Don't get me wrong, the Velodyne is very very good, it's me, I want the best when it comes to bass quality. The Velodyne is a servo controlled sub with digital room correction. I will probably order their SMS-1 which is the digital control unit from the DD-series and build my own sub(s). I haven't tested the PD's enough yet to tell which I like best but the PD's certainly have the potential.

[jdunham]

Kevin,

I noted you said you could only house a 12" driver.

This is what I did with 2 x 15" drivers. They don't use any more frontal area that a 12" would take up on the front:







Not really a sub-woofer as such (flat down to 30hz), but great up to 200hz where the font-horn takes over. My room is 12' x 18'.

I've been really pleased with these.

I am using Lambda TD15's but I was going to buy the PD's if not - they are good units.

Regards,

Jonathan

[derf]

One thing I'm curious about is how large PA drivers compare to some of the better subs with shorting rings and/or XBL2 or competing technologies, when it comes to accuracy.

To be honest, shorting rings/other fancy technology just can't compete with sheer surface area, when it comes to bass reproduction. If it was a choice between a 12" with shorting ring etc and an 18", I'd pick the bigger driver any day(all else being equal).

I think a lot of the 10"/12" subs around today are a product of people wanting deep bass and small size, which is fine, but with it comes limitations. Limited SPL, higher distortion, only good up to 100-150hz(a product of being long throw?).

I'd seriously consider the 15"/18" offerings from Eminence, in particular the Delta15LF and the Sigma Pro.

The Delta driver is cheap as chips over here(around £50 a piece), has good Xmax, around about the right Qts. 2 a side in a W/H/Flat baffle would be a great proof of concept and wouldn't cost the world to implement.

[paulspencer]

Jonathan, I'm curious why you have angled those dipoles as you have!

Derf, is that based on actual comparisons or your theoretical gut feeling?

For the larger driver to be more linear means that its excursion would need to be more linear. This is easier to achieve with less excursion, however, it doesn't necessarily follow that less xmax and more SD means lower distortion.

[derf]

Jonathan, I'm curious why you have angled those dipoles as you have!

As am I, do tell!.

For the larger driver to be more linear means that its excursion would need to be more linear. This is easier to achieve with less excursion, however, it doesn't necessarily follow that less xmax and more SD means lower distortion

To the best of my knowledge, in it's most basic terms excursion=distortion. Excursion is a product of a driver working hard to reproduce whatever signal it's being fed.

These long excursion drivers are truly a marvel of engineering and allow people to achieve deeper bass in smaller living circumstances. However, given the inclination/larger space/need for more spl etc, I believe any comparable 18" with normal excursion(say 5-6mm), would be able to provide lower distortion for the same input and spl level.

Given that the typical 18" has twice the surface area of the typical 12", it just seems very logical to me that this'd be the case.

Unfortunately, at this point it's just my theoretical ramblings, although I'm hoping someone who has actually done some tests/has some proof of this will chime in.

Of course, if I've got this wrong, I'm willing to take a slap on the wrists too. Aslong as my knowledge of things progresses, I don't mind being told I'm wrong once in a while.

[maiky76]

Hi!

Maybe this could be interesting for you!

the device is:
http://www.behringer.com/DSP1124P/index.cfm?lang=ENG
And it shoulb have a very close over all performance compare to Velo's one, much cheaper at least.

Some "how tos" to turn it in a very user friendly device.
http://www.snapbug.ws/bfd.htm
http://homepage.ntlworld.com/john.mu...meq/index.html

You can even use a DCX2496 from behringer wich is a unmatch Q/P audio digital eq, I had one for a while. I loved it. In addition the DCX could be use for many aims that should interest you!

@+
Maiky