DX55 OB - Micro Article

[Nelson Pass]

I saw that Mr. Full-Range ("Jon Ver Halen") is offering a steep discount
on the DX55 drivers, which reminded me that I wrote a micro article about
this driver use with the Eminence Beta 15" woofer in an open baffle as part
of BOB (the Big Open Baffle project). BOB is now the size of a book, so I
may as well celebrate the new year by trotting this out for Jon.

www.lowther-america.com

This is a really nice sounding system - a little better on the upper registers
than my usual 8 inch full range favorites, and not at all lacking as long as
you put deal with the size of an open baffle.

The crossover that worked well can be done with a First Watt B5, which is
documented at FIRST WATT or can be done DIY if you feel comfortable
coming up with some op amp or discrete buffers. A fine example is a
variation on the schematic circuit shown in the Slot Loaded Baffle article
on enjoythemusic.com.

The high pass filter is 12 dB/oct at 120 Hz, and the low pass filter is 12 dB
at 80 Hz. Both drivers are wired in phase. A 6 dB bump at 20 Hz is provided
by a high-Q low cut filter, and the top end is shelved down 4 dB above
20 KHz.

The DX55 is mounted at 36" high in the center of a 30" X 60" open baffle,
and the woofer is mounted below that. The open baffle is supported by
wings on the side rears, 12" to 16" deep and about 30 " high.

Attached are two graphics, one showing the near field crossover response
of the drivers separately and together, and another showing the response
full range taken at 1 meter on axis.

And there you have it.

😎

 

[NicMac]

I saw that Mr. Full-Range ("Jon Ver Halen") is offering a steep discount
on the DX55 drivers

Mr. Pass,
where? Very interested but cannot find the location of the offer😕
Cheers,
Nic

 

[fastbike1]

Click the Lowther-America link.

Mr. Pass,
where? Very interested but cannot find the location of the offer😕
Cheers,
Nic

 

[Nelson Pass]

Appendix 1

Here's that crossover.

😎

 

[Nelson Pass]

Appendix 2

Here's a diagram of the baffle.

 

[kmaier]

Quite interesting. I picked up a pair of DX65 drivers 2+ years ago from Jon in 15 ohm impedance. Perhaps this is a nice way to try them out. I also picked up a pair of AE-15 drivers from him... maybe they will work in this interesting little design of yours. Might have to cut some wood....

Regards, KM

 

[Nelson Pass]

The AE's will work perfectly IMHO.

😎

 

[kmaier]

Thanks.... sounds like a plan then. Currently I own nothing but tube amps. We'll see how the AE does with those.

Regards, KM

 

[Nelson Pass]

Depends on the tube amps. I have heard a wide range of performances
with different tube amplifiers, and some that had excellent bass.

😎

 

[mr ed]

I had been slowly working on a DX55 based OB for about a year and a half.
I had just finished a 6SN7 based active XO and was about to start back on bass driver integration. I had a couple aplha 15 un opened in the garage, when fires in our area took my house in Septemer.
I have been thinknig of trying the PM6A and a Tone Tubby next , but now you may be making me re-think and go back to the DX55. I was not sure I could get it to play low enough to blend propperly.

Cheers
Ed

 

[Nelson Pass]

I like to have a set of baffles where I can replace the FR driver easily on an
adapter plate. If you do something like this then you can pop the DX55's in
and see if you like them before trading to PM6A's.

That said, the PM6A and PM5A are pretty much my favorite Lowthers. They
take more of a bite out of the air at the lower frequencies, but their top end
is not as refined as the 5 inchers, so it comes down to personal taste.

😎

 

[alazira]

Hi NP,
What op-amp/buffer is recommended for that crossover?

 

[mr ed]

Thanks Nelson,
I will wait till i am in a new home and know what size room I have to work with before I can pick a speaker plan, but I am hoping for another OB with Lowther. If I have the room I may once again try the DX55, I think it has the best and smoothest mid and top end.
Cheers
Ed

 

[Nelson Pass]

Hi NP,
What op-amp/buffer is recommended for that crossover?

For buffers, a simple Jfet follower works exquisitely. See the B1 article.

😎

 

[alazira]

For buffers, a simple Jfet follower works exquisitely. See the B1 article.

😎

Hi,
I was referring to the crossover in post #4. What kind of op-amp is recommended?

 

[Zen Mod]

each triangle is representing a buffer

just ignore trace going from - to output , if that's easier for you

say that B1 channel (buffer stage alone ) is one triangle

 

[alazira]

each triangle is representing a buffer

just ignore trace going from - to output , if that's easier for you

say that B1 channel (buffer stage alone ) is one triangle

Thanks ZM.
What about the (-) from the 20Hz high pass? It comes from the midpoint of two 10K resistors?

 

[Nelson Pass]

Use any op amp you like, keeping in mind that it's on the bottom end.

Or cobble something discrete together like I did. You can get some ideas
from the article on discrete opamps I wrote.

http://www.passdiy.com/pdf/diyopamp.pdf

😎

 

[alazira]

Use any op amp you like, keeping in mind that it's on the bottom end.

Or cobble something discrete together like I did. You can get some ideas
from the article on discrete opamps I wrote.

http://www.passdiy.com/pdf/diyopamp.pdf

😎

Thanks NP & ZM.
Would this be a good choice?
http://www.ti.com/lit/ds/symlink/opa1641.pdf

 

[Vix]

Don't fret so much over the choice of an op-amp at the bottom end. On the other hand, it's important that the top-end (hi-pass) be done with j-fets. Just use B1 buffer block and you're done 🙂