[jsalk]

Chris ordered a pair of BePure 2's with custom side-firing passive radiators to use as a second check on music he was mastering.  He recently sent me an email commenting on the results.  Here is his email...

"Hey Jim,
     This is Chris Capaletti,  I am sorry it took me so long to reach out regarding these speakers you made for me.  I was waiting on a custom amplifier that took about an extra month to arrive.  That was the most trying month of my life, staring at these beautiful speakers without being able to listen to them. 

Though the focus of this email is my listening & measurement impressions, these came out absolutely beautiful and match the acoustic treatment I have in the room perfectly!  I am not planning to say much regarding the sound / measurement of these in this email but I do feel like what I am seeing / hearing warrants a conversation with you.  It is truly AMAZING!!! 

I am flat down to 17hz with no enhancement and only using dirac to flatten out the humps of my room.  Yes, what I am saying is only reduction not elevation!!

I am a systems calibration engineer for a living and also a mastering engineer, and the sound that this passive radiator version of these speakers is producing is unimaginably good.  I am driving them with a custom built amp, based on the latest iteration of Bruno Putzeys Class D module, that after much research made me feel was the perfect companion for your speakers. 

Maybe the ported version sounds the same / better, but considering all of the systems I have heard / tuned in my career I feel like I can honestly say this is something very special.  I honestly don't believe a ported system could keep up with the speed at which this system fires bass.  Not even just bass but it has a percussive nature all the way up through the mid band. 

My original plan was to have this be a second take on my mastering work that I do on my Amphion system in the studio, but after playing things back on both systems I am having a VERY hard time convincing myself that I hear better on the Amphions.  Anyways, I feel like in the least I owe you a positive review somewhere that will help you out, but I didn't know what your plans were for a radiator version of this speaker going forward so I didn't want to put it out there without your consent.  Also I do personally feel like you did something special here.  Thanks again Jim and bravo for this design / tuning for modern music making  / reference. I have never heard anything like this! 

-- Chris Capaletti"

Thanks, Chris, for the kind words.  And, by the way, the BePure 2's can be ordered with passive radiators as an add-on if desired.

- Jim

[GlennDog]

Wonderful!

Do you have a pair of these (with the PR) in the shop for audition? Or without . . . to .. you know, whet my appetite

TIA

[jsalk]

Wonderful!

Do you have a pair of these (with the PR) in the shop for audition? Or without . . . to .. you know, whet my appetite

TIA

We do not.  All of the BePure 2's we're currently working on have a standard port.  But we do have a pair of BePure 3's on hand and can explain the difference is sound.  From 32Hz up, they sound about the same.  The 3's just play deeper.  And they have passive radiators.

If you want to hear something truly special, stop by.

- Jim

[owlsalum1]

Have an estimated date for release of the BePure Monitor, Jim? Perhaps some preliminary specs to share? Mention of the Monitor on the CAF thread caught my attention big time. Very interested ...

[jsalk]

Have an estimated date for release of the BePure Monitor, Jim? Perhaps some preliminary specs to share? Mention of the Monitor on the CAF thread caught my attention big time. Very interested ...

These are preliminary specs...

FR = 36Hz - 40kHz +/- 3db.  Sensitivity around 87db. Size: 20" H z 8.5" W x 14" D.  Price?  Don't know yet, but it will be a more expensive monitor speaker.

I talked with Dennis yesterday and he thinks the crossover is basically done.  We are already building the first pair of production cabinets.  They will need to be finished before we can use them, but it shouldn't take all that long to do so.  I would look at a intro date just after the first of the new year.

If you are at all interested, you can email me and we can perhaps finish the first pair in the finish you desire.  You are not obligated to purchase them, but if they test out fine (which I assume they would) and the price works for you, you wouldn't have to wait to get your hands on a pair.  Just a thought...

- Jim

[DMurphy]

I'm winding up the crossover design today.  I should have some measurements if anyone is interested in seeing them. 

[DMurphy]

The drivers Jim selected for the BePure series are probably the best behaved units available.  Here is the on-axis response of the new BePure1.  Final voicing of the highs involves a lot of listening and discussion between Jim and me, but I've started this design off with slightly shelved down highs to avoid any brightness in rooms with lots of hard surfaces.  We may twiddle with the resistor settings, but you can see just how smooth these drivers are.  This is about the best I've seen:

[RonN5]

Dennis, Jim

It’s not all that common but there are some speakers that have the ability for the user to change resisters themselves to tweak the sound to their rooms and liking. I’m wondering if you have any thoughts about why this hasn’t become the norm…what am I missing?

[DMurphy]

That's a good question.   External resistor switches used to be quite common--KLH, Advent, Dynaco, and AR all used some kind of external adjustment.  Crossovers today tend to me much more complex than back in the day, and these adjustments add a lot of resistors and added complexity unless you use AR's continuously adjustable Lpads, which corroded and failed after a few years.  I try to use a crossover topology that allows the highs to be shelved down by adding a resistor in line with the tweeter positive input terminal.  But we certainly don't encourage owners to do that.  It's of more use in allowing Jim to make a needed adjustment if a particular tweeter is a little out of spec.  I think the honest answer to your question is that manufacturers don't want to be bothered with the added circuitry and don't sense much demand for it. 

[AllanS]

I've started this design off with slightly shelved down highs to avoid any brightness in rooms with lots of hard surfaces. 

Very impressive.  It sounds like you're designing them for my room!  Time to start selling some stuff...

[Rocket]

Hi Jim/Dennis,

Would it be possible to have a front ported version of the Bepure 2's? or would the long port prevent this from being placed in the front baffle?

Cheers Rod

[jsalk]

Hi Jim/Dennis,

Would it be possible to have a front ported version of the Bepure 2's? or would the long port prevent this from being placed in the front baffle?

Cheers Rod

It is possible.  No problem.

- Jim

[Boybees]

What is the price differential for the BePure 2 with passive radiator?

[jsalk]

What is the price differential for the BePure 2 with passive radiator?

Four pasive radiators, four additional grills and the extra labor would run about $900.

- Jim

[Tone Depth]

Do passive radiators change the frequency response on the BePure2s, or any other specs?

[c_note]

Jim and Dennis, can you say a little more about vented vs. passive radiator designs?  Do passive radiators produce more bass (i.e., lower f3) or do they change the perceived quality of bass (faster, tighter, etc.)?  Does adding passive radiators change the speakers' dimensions (i.e., require more depth and internal volume)?  For ultimate performance, which would you personally recommend?  Thank you for your insights!

[jsalk]

The use of passives does not change the optimum tuning of the cabinet.  It is just another method of tuning and does the exact same job as a port.  The advantage is that there is no possibility of port noise (chuffing).  But when we design a cabinet, we expand the area of the port so that it is large enough to avoid chuffing in the first place and then simply extend the length of the port to create the appropriate tuning. So the specs are the same regardless of which approach you take.  This includes the cabinet size which, in either case, provides the appropriate internal volume for the driver being used.

With ports, the area of the port and the port length combine to provide the tuning.  If you want to tune the cabinet lower, you extend the length of the port.  (Of course, this will only get you so far.  If you tune too low, the output falls off earlier so the F3 actually rises.)

With passives, if you want to change the tuning, you increase or decrease the amount of mass attached to the passive cone.  The more mass you add, the lower the tuning (the lower the resonant frequency of the passive). This does allow you to change the cabinet tuning more easily than changing the port length.

In either case, the goal is to obtain the maximum bass extension while still maintaining flat response above the F3.

When we first used passive radiators, we found one benefit we had not expected.  The ports or passives are responsible for the bass extension of a woofer cabinet.  So the deepest bass eminates from the port or the passives.   With passives, you wil generally have a passive on each side of each speaker.  So it is like having four small subwoofers spread across the front of the room.  We find that this loads the room with very evenly with deep bass.  Other than that, you should not expect any difference in terms of performance provided the port has enough area to avoid port noise.

I hope this helps.

- Jim

[jsalk]

One thing I failed to mention in the above post is that there are situations where increasing the area of the port to avoid port chuffing results in a port length that is simply not workable.  Passives solve this problem.  So, in a way, the ports or passives question is a design question.

Jeff Bagby (RIP) wrote a rather involved blog post for our web site.  Here is a link for those intersted in a more technical explanation...
https://salksound.com/blogtopic.php?id=6

- Jim

[RonN5]

Jim, are you using passive radiators in order not to have to increase the speaker size when the tuning model shows you would need a bigger box to accommodate a longer port in order to achieve the bass/f3 you are targeting?

[jsalk]

Jim, are you using passive radiators in order not to have to increase the speaker size when the tuning model shows you would need a bigger box to accommodate a longer port in order to achieve the bass/f3 you are targeting?

All those kind of considerations are taken into account when designing a new model.  Sometimes the port becomes so long, there is no physical way fitting them in a cabinet.  I've had situation where the port would be 7' long.  You can fold it, but that would require many folds and the cabinet would end up far too large.  Passives are an easy solution for that situation.

- Jim