Ascend Sierra Luna Mini-Monitor Review

[Mudjock]

Thanks Amir!
I am not a fan of ribbons unless they are in a 3 way and limited to playing lower down.
It seems amazing that similar looking speakers to these can measure so much better. At least it looks good

With a front port and hanging brackets, I am wondering if the goal for these is rear surround speakers.

Here is the info from their website

"The Luna’s versatility is unmatched, crossed at 80Hz and used with a sub, they make terrific main's sounding nearly identical to our Sierra-2. The Luna’s are the perfect surround speaker with any of our ribbon speakers as fronts, or for someone seeking the ultimate desktop monitor. Using the integrated mounting hardware, the Luna’s become the perfect on-wall speaker. "

"crossed at 80Hz and used with a sub, they make terrific main's sounding nearly identical to our Sierra-2.
You would need to use an AVR's dsp and also need a ton of power?

"The Luna’s are the perfect surround speaker with any of our ribbon speakers as fronts"
This seems like the most likely fit. Would a mid range AVR have enough power for these to handle surround channel duty?

"Or for someone seeking the ultimate desktop monitor"
You would need a subwoofer and good DSP just to get close.

It's certainly not easy to design a passive speaker of this size that will do well with the ASR test methods.

• There isn't room in the cabinet to employ a very complex crossover, which usually limits how linear the response can be.
• Any of the available enclosure options are a challenge.
  • A port has to have a relatively small cross sectional area in order to have a length that will reasonably fit in such a small cabinet, which will lead to high velocities and the associated turbulence/resonance if trying to make any substantial bass.
  • A sealed enclosure this small will not allow much bass extension.
  • A passive radiator will need to be on a side or rear of the cabinet, which limits placement/mounting options. It can also be difficult to avoid physical interference between the woofer and passive radiator(s). There just isn't a lot of room.

With an active speaker employing DSP, many of these issues can be addressed.

• The response can be linearized and individual driver responses can be tailored with outcomes that would be difficult to achieve passively.
• Deep bass can be filtered out aggressively
  • Reduced port turbulence and woofer distortion
  • Increased SPL capability
• A sealed design can be tailored with some bass boost combined with a sharp cutoff.

The typical use cases for a speaker of this size are as outlined by Ascend (high-passed with a sub filling the bottom, or nearfield low SPL duty). In those use cases the port and distortion issues will not be nearly as large an issue as indicated by the ASR measurements. The ASR measurements are certainly useful to indicate what a speaker can and can't do, but it is important to keep in mind that the weaknesses identified may not be applicable to your use case. Small speakers can provide a good experience when used within their limitations.

 

[Robbo99999]

"Woah!" I said when I first set eyes on that spinorama...that's Halloween in a spinorama right there!

 

[sam_adams]

One way to determine how the port contributes to or detracts from the FR would be to plug the port and remeasure. I don't expect @amirm to do this though as the speaker is probably off the test stand and on its way back to the contributing member.

 

[napilopez]

One way to determine how the port contributes to or detracts from the FR would be to plug the port and remeasure. I don't expect @amirm to do this though as the speaker is probably off the test stand and on its way back to the contributing member.

If the original owner has a umik or other measurement mic, perhaps they can help. Given the speaker is very small, you could probably measure it from about 1-2 feet and see less of the room while not having serious issues with driver integration. For a single on-axis measurement of bookshelf speakers, I find 2x baffle width(in this case 2x 5.75 in) is pretty much always pretty close to a 2m measurement. Certainly close enough to investigate what's going on in the lower midrange.

 

[pjug]

Can anyone explain why these small speakers have this problem with a front slot port? I have the WOW1 where Amir showed a problem with the port. I also have much larger Usher V601 that are front slot ported and the FR of the port looks smooth, see below.

 

[andreasmaaan]

Can anyone explain why these small speakers have this problem with a front slot port? I have the WOW1 where Amir showed a problem with the port. I also have much larger Usher V601 that are front slot ported and the FR of the port looks very smooth.

Ports have issues like those you see here for two main reasons. Firstly, ports have pipe resonances which are a function of port length (longer port = lower frequency pipe resonances). Secondly, the woofer's backwave, if not sufficiently damped, tends to spill out of the port.

In a smaller enclosure, it is more difficult to adequately damp the enclosure due to lack of space, making it harder to minimise (a) the extent to which the pipe resonances are excited and (b) the extent to which sound radiated off the back of the woofer spills out of the port.

Moreover, because the ratio of port surface area to port length determines the frequency of the system resonance (i.e. the resonance you do want), a trade-off needs to be made between the surface area of the port and its length. Increase the port's surface area, and you must increase the port's length to achieve the same resonance frequency.

A shorter port (which will necessarily have less surface area for a given system resonance frequency) will have pipe resonances higher in frequency, at frequencies where internal damping is more effective at absorbing the woofer's backwave and thereby avoiding the excitation of (unwanted) pipe resonances. However, as the port will have less surface area, it will suffer from higher turbulence for a given SPL.

Taking all these factors into consideration, tradeoffs must be made between:

• port length/surface area: a longer/larger port will result in less turbulence, but pipe resonances will occur lower in frequency where they will be harder to damp, whereas a shorter/smaller port will push pipe resonances higher up in frequency where they are more easily damped, but will increase turbulence in the port, leading to more port compression/distortion
• internal damping: more/heavier damping will result in less "spill" and less excitation of pipe resonances, but also less effective operation of the port (and in such a small enclosure, there is a limit on how much damping can be squished in, anyway)

These factors all also apply to larger ported enclosures, but are much harder to balance in a smaller enclosure for the reasons mentioned.

 

[CDMC]

I do respect the difficulty in designing quality products and the little guys have the disadvantage with resources, that said Ascend is big enough and their products cost enough. (these are not budget priced speakers, even if the so called mark-up is less than some competitors that use similar drivers)
These guys can afford to send their products for Kipple testing or Ancheotic chamber measurements and other more microscopic testing.
They may need to charge more if they invest this way however then their products will actually be worth the $2k bill or whatever vs costing $1500 but being worth $500 in comparison to competitors.

I don't think this is necessarily true. Dennis Murphy is able to design great speakers without these resources. Dennis Richie also seems to be able to (once you get past his voodoo stuff). Both seem to have a commonality in that they are married to how they want the end product to perform and have certain design beliefs that dominate. With Mr. Murphy it is linear on axis, matching directivity at the crossover and a smooth fall-off of axis. Mr. Richie appears to have similar goals, but has expressed that he also believes vertical directivity is very important and is willing to compromise on axis response to get better vertical performance off axis.

What I notice from both of them is they do not spend time discussing the cost of drivers versus the final product price, nor are they married to any particular driver. Rather, they pick the drivers that best meet their goals for the price point they are building. I think not being married to a particular brand or type of drivers allows a designer to be more open to finding products that fit their needs. As far as I know, the BMR radiator that Mr. Murphy uses is an extremely inexpensive full range driver that was designed for small bluetooth speakers. Many would have probably ignored it as not being "audiophile approved", Dennis saw a driver that offered incredibly smooth response and low distortion in the range he needed.

 

[amirm]

If the unwanted port resonances in the mid-range deliver 5dB more sound pressure than the intended BR fundamental resonance, one should think about whether there is not a faulty design (this was surely noticed already with the first prototype).

I would not rely on the exact level of the port versus the drivers. The distance to it is not the same as the distance to the driver.

Edit: I say the above independent of the point you were trying to make.

 

[CDMC]

Can anyone explain why these small speakers have this problem with a front slot port? I have the WOW1 where Amir showed a problem with the port.

Small, slot ports tend to have a high air velocity that causes resonances. I think the WOW1 measurements looked much better than the Luna:

https://www.audiosciencereview.com/forum/index.php?threads/salk-wow1-bookshelf-speaker-review.14842/

 

[amirm]

One way to determine how the port contributes to or detracts from the FR would be to plug the port and remeasure. I don't expect @amirm to do this though as the speaker is probably off the test stand and on its way back to the contributing member.

Correct. A full scan and documentation costs a day and opportunity to test another speaker.

 

[pjug]

Ports have issues like those you see here for two main reasons. Firstly, ports have pipe resonances which are a function of port length (longer port = lower frequency pipe resonances). Secondly, the woofer's backwave, if not sufficiently damped, tends to spill out of the port.

In a smaller enclosure, it is more difficult to adequately damp the enclosure due to lack of space, making it harder to minimise (a) the extent to which the pipe resonances are excited and (b) the extent to which sound radiated off the back of the woofer spills out of the port.

Moreover, because the ratio of port surface area to port length determines the frequency of the system resonance (i.e. the resonance you do want), a trade-off needs to be made between the surface area of the port and its length. Increase the port's surface area, and you must increase the port's length to achieve the same resonance frequency.

A shorter port (which will necessarily have less surface area for a given system resonance frequency) will have pipe resonances higher in frequency, at frequencies where internal damping is more effective at absorbing the woofer's backwave and thereby avoiding the excitation of (unwanted) pipe resonances. However, as the port will have less surface area, it will suffer from higher turbulence for a given SPL.

Taking all these factors into consideration, tradeoffs must be made between:

• port length/surface area: a longer/larger port will result in less turbulence, but pipe resonances will occur lower in frequency where they will be harder to damp, whereas a shorter/smaller port will push pipe resonances higher up in frequency where they are more easily damped, but will increase turbulence in the port, leading to more port compression/distortion
• internal damping: more/heavier damping will result in less "spill" and less excitation of pipe resonances, but also less effective operation of the port (and in such a small enclosure, there is a limit on how much damping can be squished in, anyway)

These factors all also apply to larger ported enclosures, but are much harder to balance in a smaller enclosure for the reasons mentioned.

Thanks very much for this. It may take a while (maybe never?) for me to digest it. What causes the effect to be so choppy? For example the 30dB difference between 500Hz and 600Hz in the port measurement in this Ascend?

Edit: looking again the peaks are just multiples of ~600Hz. Somehow that wasn't apparent to me at first.

 

[andreasmaaan]

Thanks very much for this. It may take a while (maybe never?) for me to digest it. What causes the effect to be so choppy? For example the 30dB difference between 500Hz and 600Hz in the port measurement in this Ascend?

These pipe resonances I mentioned tend to be very high in amplitude but very narrow in bandwidth (like sharp spikes). Since they occur at harmonics of the port's length, they are spaced apart at constant intervals. It looks here as though the first pipe resonance is at around 600Hz. The rest of the mess that follows is a result of higher-order pipe resonances at harmonic frequencies of the first pipe resonance (i.e. multiples of it), plus "spill", which peaks at frequencies at which standing waves form inside the cabinet (these frequencies are determined by the internal dimensions of the enclosure).

I don't know for sure why that dip is there just below the first pipe resonance at 600Hz, but this would also likely be related to the internal dimensions of the enclosure - perhaps at the location inside the enclosure of the port entrance there's a null (if you're familiar with room modes, this is a similar phenomenon here, only at a much smaller scale).

 

[infinitesymphony]

I’m not sure what they mean by “Reference Quality Mini Monitor”... Must be a joke, lol...

If you think that's bad, you should see the reference speaker!

</Dangerfield>

 

[Chromatischism]

It looks like this result reveals more shortcomings in Ascend's measurement setup than anything. Maybe they will consider updating that to get a clearer view of things during the design process.

 

[amirm]

It looks like this result reveals more shortcomings in Ascend's measurement setup than anything.

That's my sense of it. Given the fact that they publish measurements, should they have seen the reality, they would thought twice. This is a common theme with many smaller manufactures making rough measurements like this. With advent of NFS scanner and service cost as low as $1000 to get spin data, companies small or large should get proper measurements. There is no excuse anymore.

 

[ModDIY]

It looks like this result reveals more shortcomings in Ascend's measurement setup than anything. Maybe they will consider updating that to get a clearer view of things during the design process.

Yes but it's a shame for those who have already bought these speakers and I think it is not acceptable coming from a supposedly serious company, and claiming that it is a mini-monitor of reference.

 

[ctrl]

It's certainly not easy to design a passive speaker of this size that will do well with the ASR test methods.

However, @amirm has already measured small loudspeakers that deliver significantly better quality.

In addition, the faulty BR port could have been detected with the simplest measuring equipment and thus avoided.
If the loudspeaker would only cost a few dollars or a DIY beginner would have designed it, no problem.

To show how the BR port of a small loudspeaker measures up, developed by a bloody DIY beginner with only rudimentary knowledge of loudspeaker development, here are my first developed small BR loudspeaker (4'' woofer + tweeter, it's a bit over ten years ago and I'm a bit ashamed of the mistakes made).

Measured directly at the BR port, the result was

A midrange resonance has the same sound pressure as the BR resonance frequency - the result when dilettantes develop loudspeakers
With a little more experience the results became better over time (bookself speaker with 8'' woofer):


Remember, the unwanted BR-port resonances of the Luna RAAL are 5dB higher then the intended BR resonance according to Amir's measurement.
What I mean to say is that something like this should simply not happen with a high-priced "reference monitor".

 

[andreasmaaan]

I really doubt this comes down to inadequate measurement equipment.

A measurement like the one which Amir used to diagnose the problem can be done at home with any <$100 measurement mic:

I don't know what the reason is that this port/enclosure is such a mess, but the measurements suggest that the enclosure volume/dimensions are way off for this woofer, and that in an effort to squeeze a port that wouldn't chuff at even low SPLs into a (probably) 2.5 litre enclosure, they have had to make it way longer than is sensible for a woofer that crosses over at around 3500-4000Hz in an enclosure in which they were not able to fit damping material that would be effective in the pipe resonance range of the port.

My best explanation is that they decided from the outset that this would be a <3 litre bass reflex enclosure, but then when it came to prototyping, they discovered that the woofer, the enclosure, and the port couldn't be made to work properly together given the design constraints (some of which I can only guess at). Then, instead of abandoning the speaker or going back to the drawing board, they did their best to make a finished product out of it and released it anyway.

Ofc, this is all very speculative...

 

[Chromatischism]

Yes but it's a shame for those who have already bought these speakers and I think it is not acceptable coming from a supposedly serious company, and claiming that it is a mini-monitor of reference.

To be fair, the owners like the sound, quite a bit in fact.

 

[Chromatischism]

I really doubt this comes down to inadequate measurement equipment.

It doesn't show in Ascend's measurements, so something is either wrong with their measurements, or something is wrong with the sample.