Why the 8NDL51 is My Favorite Midbass

Someone emailed me the following:

"Hi,

I have seen that you are a big fan of the B&C 8NDL51 (and 8PS21 too) woofer. And your advices I red on this forum are often very interesting ;-)

So, I have few questions...

I plan to build a powerfull 3-way speaker with sidefiring sub, a 7" or 8" woofer, a compression driver if needed or a Satori tweeter in a Jantzen horn...)

1/ Why do you prefer it (8NDL51) over other 8" PA woofers (like 18Sound 8NMD420 or 8PR200 from FaitalPro for exemple) ?

I want to use the woofer from 100 to 1500/1700 Hz...

2/ How will you compare these PA 8" woofers to highy regarded Hifi woofers like AT 18H52, SB MW19P or Vifa NE225W (thes I planned to use before your advice on the B&C 8NML51) ? Resolution, speed wise...

And Do you know why so few Hifi Speakers manufacturers use these PA speakers while most DYIers that use them are very happy ?"


Here's why I like the 8NDL51 so much:

In the realm of "hi fidelity" speakers, manufacturers tend to use 6" and 7" woofers. I think the reason that 6" and 7" woofers are popular is because that's a size that has a nice compromise between low and high frequency extension.

For instance, I have some SB Acoustics woofers here, and they have an FS of 30Hz and the woofer can play to about 2khz.

If you're trying to build a two-way speaker that can cover 40hz to 20khz, a 7" woofer like the SB Acoustics SB17 is a great foundation.

But here's the thing: I couldn't care less about getting my midbass to play to 40hz.

All of my systems include a subwoofer.

So, playing to 40hz is completely unimportant to me.

And that's why I like the 8NDL51 so much. Because it's optimized for a cutoff of about 80Hz, instead of 40Hz, it's more efficient than your typical 7" woofer.

And because it's an 8" woofer, it has higher power handling than most 6" and 7" woofers.

Put these things together, and the 8NDL51 has the ability to blow the doors off of most "audiophile" 6" and 7" woofers.

Of course, you can take this a step further, and use a 10" or even a 12" woofer for a midrange.

I'm not a big fan of doing that, for a couple of reasons:

1) you have to push the crossover lower and lower on the tweeter, which causes issues

2) Though a 10" or a 12" woofer has even more output than the 8NDL51, I don't personally need to hit 120dB in my living room. If I was making a speaker for a club or a big venue, I'd probably consider 10" and 12" midbasses.
 

augerpro

Member
Paid Member
2006-08-27 11:02 am
www.somasonus.net
3rd party measurements at the time showed a competition-beating low distortion motor. Coupled with a well behaved cone breakup, this made the 8NDL51 a perfect marriage of Pro Audio and HiFi. Now technology marches on, so maybe there is something better? Still, I bet it beats 90% of competition in well-balanced performance even today.
 
Why that particular B&C 8"? They have several that look interesting and very similar. I have only used the 8pe21 which is really good but likes a pretty high crossover when used as a direct radiator.

8NDL51 has 3X as much displacement as the 8PE21, a lower FS, and higher QTS.

Basically the 8PE21 is largely unsuitable as a midbass; it's a midrange.

If you want a cutoff of about 80hz, to cross over to a sub, the 8NDL51 is really tough to beat.

For instance, I have some Yamaha two-ways that use a 12" woofer and a 12" waveguide. And though the Yamahas dig down to about 50Hz, if you don't need to play that low, the 8NDL51 can keep up.

Also, the B&C has shorting rings that the Yamaha lacks, and that will likely improve the midrange.

It's a really nice balance of parameters. It's not the greatest midbass of all time, but it's up there.
 

hweb

Member
2011-09-19 8:39 pm
MA, USA
I'm sure the 8NDL51 is an awesome driver, but I never end up using 8" midbass drivers because of the lack of directivity control below 2kHz. I always end up with a 12" - 15" driver simply because I want to push directivity control down as low as I can practically do in my listening room. So, for me, it's drivers like JBL 2226, B&C 15NDL88. My newest project will use a JBL 2217 (14") which will be a first time for me.
 
understood. Why the NDL vs MBX, MDN etc. they have so many options I'm having a hard time making up my mind.
The lumped parameters of 8MBX51 don't seem too different from 8NDL51. Slightly more sensitive, some differences in Fs and Qts that yield a natural response with a higher bass cutoff. The excursion limits look similar on paper, so it hopefully wouldn't be much of a stretch to equalize the differences out.


MDN51 and NDL64 have less bass response and rated excursion.
 

Pallas

Member
2004-08-23 5:59 am
Here's why I like the 8NDL51 so much:
<snip>
And that's why I like the 8NDL51 so much. Because it's optimized for a cutoff of about 80Hz, instead of 40Hz, it's more efficient than your typical 7" woofer.

Are you assuming some sort of high order enclosure or EQ? In a closed box the F3 will be ~an octave higher than 80Hz.

However, the rubber surround version (8BG51) trades a couple dB of sensitivity for a half octave of LF extension.
 

mordikai

Member
Paid Member
2005-11-07 3:34 pm
The lumped parameters of 8MBX51 don't seem too different from 8NDL51. Slightly more sensitive, some differences in Fs and Qts that yield a natural response with a higher bass cutoff. The excursion limits look similar on paper, so it hopefully wouldn't be much of a stretch to equalize the differences out.


MDN51 and NDL64 have less bass response and rated excursion.

thank you, thats helpful.
 
I am planning a three-way compact loudspeaker in which a 5" midrange driver will be used (a Beyma 12LX60V2 will be used as bass driver, a Sica LP 110.28/380 TW as tweeter).

The B&C 5NDL38 was one of the favourites, but in the end I chose the FaitalPro M5N8-80.

I haven't started with the construction yet and so there are no measurements available yet. But I am curious. :)
 
On a semi related note, I designed and built a Unity type horn that used a pair of 8NDL51's and a BMS4550. These were used for many years in a DJ party system driven by an amp capable of 1100W RMS per channel into the 4R load the boxes presented. The amp would often be driven into clipping. These boxes are still going strong and are installed in a night club in my home city. The 8NDL51 is one seriously robust driver!