Ascend Acoustics CBM-170 SE vs Arx A1b - Page 4

Some Info on XBL2 from the Adire tech paper.

http://www.adireaudio.com/Files/XBL2TechPaper.pdf

"XBL2 reduces distortion. Keeping the BL flat means more constant motor force at excursion, which means better tracking of large-signal inputs.

This advantage translates into directly measurable and audible reductions in distortion. For the example motors analyzed in this paper, the distortion figures are given for ±10.8mm excursion (70% of Xmax). The

XBL2 motor has less than 30% of the distortion present in the other motors.

XBL2 motors are useful for all audio transducers. While this example has focused on woofers, the advantages are also applicable for midranges and tweeters. In fact, the low inductance and moving mass of this

motor are extremely beneficial in wideband transducers. Typically, XBL2 will halve the inductance of a comparable-excursion overhung motor, which can result in adding a full octave of extension on the high end.

Add in the lower moving mass from the short coil, and the driver designer has a greater degree of flexibility in driver creation."

XBL2 isn't the absolute best its just another very successful way of designing a driver. Theres many other great drivers out there without XBL2 tech.

I won't dispute any of that or anything specific to the woofer in the Arx. I don't own it and haven't heard it...but I have heard other midwoofers that use XBL2 in other speakers. If it is a good driver, it's a good driver, just like the woofer in the CBM-170. If it sounds good, it sounds good....I don't care the speaker gets there, because in the end, it really doesn't matter.

I'm just being specific to XBL2 technology. One can simply google XBL2 and see many of the discussions related to it. It isn't a new design, and has been around for at least 10 years, so there have been many discussions. It started out mainly out for subwoofer drivers, but really is not talked about a lot in that application. Just google "XBL2".

In fact, Dan Wiggins(the owner of the patent) has said that even if a driver uses XBL2, doesn't mean it is a good driver.

You are making the assumption that the Arx has an advantage in distortion.

We would have to see the distortion numbers for each driver to say one has any kind of advantage over the other.

One can poorly implement ANY technology. This is not poorly implemented.

Here is another wideband driver that uses XBL2:
http://creativesound.ca/details.php?model=VWR126X

It is certainly NOT limited to bass use and it does not necessarily mean increased inductance. Minimizing inductance in ALL bass drivers is a constant struggle, regardless of the motor design employed. Often in bass transducers, it is a tradeoff of how much excursion one can achieve vice the inductance which limits upper frequency response/sensitivity. For bass drivers, inductance issues can be present merely as a result of the immense amount of metal in the motor itself and not due to any singular motor design.

These limitations do not hamper a midwoofer which has a much smaller (though relatively very sizeable) motor structure.

I have read that paper, and it is interesting that Dan says it has low inductance, where a lot of discussions I have read talk about higher inductance.

I agree with you, it is a great tech for drivers, but not the only one.

The Ascend uses a std overhung design, no?

Agreed.

In the end, like I said, it is about how the speaker sounds (and for some, how it measures).

Yes. For some.

Well who has a Klippel? lol. I know one person, but he mainly does car audio drivers

Yeah I've noticed alot of car audio guys use Klippel especially on DIY MA car audio forum. Seems like when it comes to drivers they really go to some lenghts to get every little detail.

Now we just have to find someone who is willing to send out there Ascend driver and Arx driver.

Yes..I believe so.

The extreme car audio hobbyist is a different breed...more extreme than their home audio counterparts. At least from I can tell.

Yet initially you only mention reading about the higher inductance (as a drawback). To ask why would be the very definition itself of a rhetorical question.

True...but I read papers like that as more marketing...which you have to admit, is how it reads. The discussions are much more interesting.

Have you ever selectively referenced what could also be construed as marketing like it's objective and/or factual?

Two forums with a several page threads discussing XBL2 tech. For those that want to read up more on it. And I noticed our thread is just a few links down when you search for XBL2 tech.

http://www.caraudio.com/forums/subwoofers/80396-does-xbl2-really-mean-anything.html
http://www.ecoustics.com/electronics/forum/car-audio/151628.html

The only thing I don't get is the recurring claim that XBL2 is more efficient cause to me it seems like my Arx need much more power to get to a certain level compared to all my other speakers i've. Going from Axiom to Arx was a huge step in the opposite direction especially for output were the Axioms didn't need as much volume to get as loud as the Arx.

I'm going to add that XBL2 sacrificing any meaningful amount of efficiency to a std motor is bunk. I'll quote from eCoustics back in 2005 re XBL2:

"BTW, the main benefit of this topology isn't fully realized with subwoofers. This actually sees more benefit with midbasses, midranges, tweeters, and full range drivers. Typically, and XBL^2 driver will still only have 30% of the distortion other designs have at 70% of maximum linear excursion (x-max). In many cases, this translates to around a 1% distortion rating at 70% excursion, while others are between 3 and 5%. This allows a design that yields very clean sound at higher volumes and can fully realize the potential of enclosures such as sealed and infinite baffle, where excursion is naturally higher and SQ tends to suffer at high volumes due to that.

The biggest benefit of XBL^2 is that it allows a smaller driver to have higher output levels and a wider bandwidth, meaning a 6" midbass driver could potentially have the depth of a typical 8" driver and rival some 10" drivers for depth, and be very linear and accurate doing it. Their Extremis midbass driver is a good example of this, it is a 6.8" driver having a 13mm one way X-max, only a .13mH inductance, and is ideal for ported boxes tuned in the 30s, offering in-room extension down to the 20s. Inductive rolloff occurs around 8khz and there are no nasty breakup modes from the cone, crossover will typically be 2-3khz. To give you an idea, the Scan-Speak Revelator and SEAS Excel drivers, which are renowned high end home audio drivers, have a good bit more inductance, right at half or less than half the excursion level, less motor strength, and less bandwidth.[/B][/B] As their designs progress even further, Adire is going to be a very difficult manufacturer to beat, or even level with for that matter.

About efficiency, XBL^2 is actually more efficient than most motor designs out there overall, it is the soft parts that tend to bring down the efficiency of the subs they are used in. Adire uses epoxy treated paper cones in their subs, which are heavier than many other materials, but chosen for their damping ability, they also use a wider profile surround as opposed to a taller one, which controls the subwoofer very well, but cuts down surface area, and tighter suspension designs than many. XBL^2 isn't really the reason a Brahma isn't as efficient than other subs, but rather the reason it isn't less efficient than it already is. Adire is also more true with their sensitivity specs than many other manufacturers. Remember as well, that sensitivity specs are very misleading and give no clue to how loud a subwoofer will be at higher volumes. Excursion is low at 1 watt , a subwoofer with a parabolic BL curve will do well at 1 watt, but lose motor strength (thus efficiency) at higher volumes. XBL^2, on the other hand, offers flat BL and will give more BL at higher volumes than many other motor designs, making it more efficient with the power."

http://www.ecoustics.com/electronics/forum/car-audio/151628.html

I would reference this quote regarding the efficiency issue:

"Remember as well, that sensitivity specs are very misleading and give no clue to how loud a subwoofer will be at higher volumes. Excursion is low at 1 watt , a subwoofer with a parabolic BL curve will do well at 1 watt, but lose motor strength (thus efficiency) at higher volumes. XBL^2, on the other hand, offers flat BL and will give more BL at higher volumes than many other motor designs, making it more efficient with the power."

I don't think XBL2 implementation means more wideband efficiency, necessarily. It does mean an increase in efficiency in bass frequencies as excursion increases AND a reduction in distortion at all frequencies."

In the real world, this won't appear as standard "efficiency" in terms of notches on the volume dial. It will, however, appear as vastly reduced dynamic compression of bass transients at higher playback levels, with speakers maintaining their dynamic bass performance to much increased spl outputs. The bass won't wither when the cabinets are pushed hard and dynamic compression will be MUCH reduced. It will stay more "punchy".

Make sense?

As for overall sensitivity, one is always trading excursion capability and cone mass (for good bass performance) for higher sensitivity. As cschang said, tradeoffs must be made. But my point is that ZERO unique tradeoffs had to be made to employ XBL2/SplitGap tech into the Arx midwoofers. These are tradeoffs that ALL designers face....regardless of the motor design or technology implemented.

See definition # 3:
http://www.merriam-webster.com/dictionary/vice

"Definition of VICE:

in the place of 'I will preside, vice the absent chairman'; also : rather than"

It is common usage in law enforcement and MIL communities. It is less common for regular folks. You're not the first one who has asked me this.
Edited by BufordTJustice - 1/8/13 at 11:55am

Makes sense now lol.

Never though of it that way. I had to have the dial much higher than I ever did with the Axioms and I first thought something might be wrong. Just like the Axioms had more "efficiency" but seemed strained once they started to play louder. The Arx producing the drum kick for example still had authority even with the cone moving like crazy. Where as the Axioms seemed to have almost zero excursion from the woofers (M22s).

Is MIL short for milf? If so, the word vice might have a very different definition in that particular case.

Haha. It's short for military. However, if the MILF is hot and no longer married, she is fair game.

Yeah, think about it as more control over the cone at higher excursions (and higher volume settings). This, necessarily, means reduced distortion at higher volumes.

I'm sure I have.

If I may, any woofer's F3 limit and related efficiency at that point are tied to the physics of the driver, the cabinet air volume, and the bass reflex tuning parameters. These parameters describe both the bass limit and loudness at that limit, and involve only those inherent physics and not the speaker brand, quality, or even moving coil technology, at least to any significant degree. When we analyze them we always find that the larger piston enjoys an advantage - it is simply the larger acoustic lever.

In other words, to make the 5.25" woofer go as low as the 6.5" woofer in similar volumes of cabinet air, we have to decrease the efficiency of the smaller driver. Of course, we can easily gain this difference back with any good amplifier with ample available power.

Another significant factor enters in, which is current flow through the voice coil. Assuming that typical modern amplifier, a true 8 ohm woofer develops on average half (-3dB) the sensitivity of that same voltage across half that load, that being the 4 ohm woofer. The lower impedance driver will naturally be louder, at the cost of that much loudness again at the amplifier's maximum output.

Since current rises exponentially as frequency drops, the speaker with the 8 ohm midwoofer - regardless of the impedance peaks in its bass reflex region or in its crossover or tweeter region impedance magnitudes - should be considered a true 8 ohm system. Furthermore, the mid/woofer's impedance sets the entire speaker's average efficiency - a designer typically tunes tweeter levels down to the mid/woofer's level and not the reverse. (When the A1b is noted for spectral cohesion and natural dimensionality, it's partly because the tweeter is matched to the midwoofer.)

In short, to make them comparable under test, an 8 ohm load requires a 2.83v signal for 1W, while a 4 ohm load requires a 2.0v signal for 1W.

Whether such a difference applies here is up to readers to research in order to develop their perspectives.

Thanks Jon.

I just remember when I first got the A1s how much further I had to turn the volume up to new levels I never went too before. But they easily out classed the more "efficient" speaker especially in the bass and just pure fullness.