Sierra - The Crossover

[davef]

At the heart of the Sierra is OPPIX™.

OPPIX stands for Optimized Paradromic Phase Integrated X-Over (crossover). This sophisticated variable slope crossover precisely aligns the acoustic phase response of multiple transducers at the exact point where the response of one transducer crosses over to another, with reference to a specific point in space. This precise alignment allows the transducers to mimic a single point source radiator, allowing for symmetrical dispersion even with an asymmetrical transducer layout while maintaining a linear frequency response and greatly reducing off-axis phase and response anomalies. It also avoids the undesirable frequency response anomalies commonly found with even the best coaxial drivers.

As an example, examine the off-axis measurements of these 2 popular high-end 2-way loudspeaker using a common tweeter-woofer driver layout (see below). Notice the dramatic difference in the off-axis frequency response above and below the speaker (vertical symmetry). Also compare the horizontal response to the vertical response. This is a typical asymmetrical response, and since what we hear in a room is a combination of direct-sound and reflected-sound from all directions, even though the on-axis response might be flat, the asymmetrical loudspeaker will deliver a less accurate response, since the speaker performance varies dramatically off-axis.



Competing 2-way loudspeaker
http://forum.ascendacoustics.com/images/ascenduploads/symspkrA.gif

Another Competing 2-way loudspeaker
http://forum.ascendacoustics.com/images/ascenduploads/symspkrB.gif


Now notice how symmetrical the Sierra’s off-axis response measurements are (see below).. Symmetry is maintained up until the point where the length of the sound waves become less than the distance from the source to the edges of the baffle. In the case of the Sierra, precise response symmetry is maintained from 40Hz up to approximately 10kHz, at up to 25 degrees off-axis. This translates to accurate in-room performance, a “correct” soundstage with precise imaging, and allows the Sierra-1 to perform to spec when positioned vertically or horizontally. OPPIX™ also allows the Sierra to perform exceptionally well as a vertical or horizontal main and a vertical or horizontal center. I recommend three Sierras in the front (left, center, right) for the ultimate in timbre matching and soundstage consistency.



The Sierra-1
http://forum.ascendacoustics.com/images/ascenduploads/symsr1.gif


Another feature of the Sierra crossover is maintaining extremely linear electrical impedance. From 1 kHz up through 20 kHz, impedance varies by only ±3 ohms, from 2 kHz up, by a remarkable ± 1 ohm. You will also notice that impedance does not rise as frequency increases. This translates to an easy load for any amp and consistent performance from one amplifier to another. We have tried the Sierra on a host of receivers and amplifiers and it delivered consistent performance from all of them.



The Sierra-1 Impedance + Electrical Phase
http://forum.ascendacoustics.com/images/ascenduploads/BODE.gif



This advanced crossover also features:

High-performance metalized polypropylene capacitors in the direct signal path, these offer lower dissipation than the more common polyester based film capacitors
Air-core inductors to reduce saturation effects combined with heavy gauge windings to reduce resistance and improve efficiency
Low inductance resistors to reduce distortion and provide accurate transient information
Heavy gauge internal copper wiring
Linear impedance response for consistent performance regardless of amplification source
Isolation mounting, whereby the crossover is attached to the cabinet using isolation feet, which reduces the transfer of resonances from the cabinet to the crossover components


Optimizing this crossover and developing the technique and circuit topology to accomplish this was my most rewarding and challenging aspect of this loudspeaker…




The Sierra-1 Crossover
http://forum.ascendacoustics.com/images/ascenduploads/xover1.jpg

The Sierra-1 Center with rotated tweeter (a FANTASTIC center speaker)
http://forum.ascendacoustics.com/images/ascenduploads/center1.jpg

http://forum.ascendacoustics.com/images/ascenduploads/center2.jpg

http://forum.ascendacoustics.com/images/ascenduploads/system1.jpg


Woofer and tweeter tomorrow :)

[Quinn]

Very impressive. Does this mean they are phase aligned from 40hz to 10khz?

[Mag_Neato]

Very nice Dave! Identical speakers across the front, like the 340's, but with better dispersion characteristics.

Will that center speaker match well with my 170's?

[Sammy]

This is fantastic stuff. And here I was ready to order the 340's within the next month.

Congrats to you and the company Dave, it's great to see you succeed.

[debo]

Ed...no it won't, your buying my 340 remember!

[Mag_Neato]

Ed...no it won't, your buying my 340 remember!

:D ....but the piano black finish will better match my new AQUOS 32" HDTV!!

Jeff, it will come down to price, my patience, and willingness to save up for one of these. If people are gaga over these once they start getting them, I will definitely be considering the Sierras! Do give me a price for the 340 though.

[curtis]

Very Interesting Stuff!!

[Mag_Neato]

I'm digging the natural bamboo finish a lot. It will definitely require very little maintenance, while daily dusting/polishing of the piano black may be needed.

I noticed that the grill mounting holes for the center are in the same locations as the L/R, while the grill itself has been lengthened to cover the entire front of the speaker. Where will the logo go?

[curtis]

For the center, my guess is that you can put the logo on the grille if you wish.

[Sam1000]

Hi Dave,
what would be an ideal crossover point for Sierra's from subwoofer? Now, when are you taking orders for these?? Can you book me a pair+center channel? :D

[curtis]

Hi Dave,
what would be an ideal crossover point for Sierra's from subwoofer? Now, when are you taking orders for these?? Can you book me a pair+center channel? :D
I bet we get the +-3dB point with the woofer and tweeter info.

[Quinn]

I bet we get the +-3dB point with the woofer and tweeter info.

From the above info "In the case of the Sierra, precise response symmetry is maintained from 40Hz up to approximately 10kHz, at up to 25 degrees off-axis." So, 40Hz bottom end?

[Mag_Neato]

40Hz......at what +/-db? That is a healthy bottom end. You could do without a sub for music if you elected to go that route.

[Quinn]

40Hz......at what +/-db? That is a healthy bottom end. You could do without a sub for music if you elected to go that route.

I'm assuming from that that 40Hz is the +/-3dB point but we won't know until tomorrow.

[BradJudy]

I'm assuming from that that 40Hz is the +/-3dB point but we won't know until tomorrow.

The FR graph has been posted in this thread and it looks like a -3db around 60Hz. (hard to tell with that size of picture and scale)

[JohnMichael]

The more I know about the Sierra the more I want a pair.

[GirgleMirt]

Yeah, from the graph it looks like it's +/- 3dB from ~75hz to 20khz. Which sounds great for sub integration.

5 ohms load, and can we say from the graphs that they have an ~85dB sensitivity or the graphs always position the on-Axis FR to 85dB for the sake of off-axis measurements?

[Sam1000]

Yeah, from the graph it looks like it's +/- 3dB from ~75hz to 20khz. Which sounds great for sub integration.

5 ohms load, and can we say from the graphs that they have an ~85dB sensitivity or the graphs always position the on-Axis FR to 85dB for the sake of off-axis measurements?


I think the FR starts dropping even before 100, that's why I asked the question about sub integration. May be 100hz could be an ideal crossover point. Let's wait and see....

[Quinn]

I really can't see introducing a reference monitor that doesn't have better extension than your other offerings and can't compete with the competition's extension.

Then there is Dave's tidbit on another thread.

"3. We want to move a lot of air with this woofer, a phase plug will actually decrease the piston area of the driver so for this application, the phase plug was a disadvantage." http://forum.ascendacoustics.com/showpost.php?p=22491&postcount=54

Moving a lot of air means bass to me.

[davef]

Hi Guys,

As with most frequency response graphs, the graphs are only valid to about 200Hz. Notice the "green" bars on the top and bottom that extend from 18Hz to slightly over 200Hz. They indicate the invalid portion of the response curve, this is caused by this distance from the 1st reflection point to the mic.

I will post ground plane + anechoic meausurements this evening that will show you the full bandwidth frequency response of the speaker.

The actual quasi-anechoic frequency response of the speaker is +/- 3dB from 44Hz to 22kHz. Expect -3dB in a typical room to be about 39Hz. Technically, the speaker is +/- 1.5 dB from about 55Hz to 22kHz.

Bass response from the Sierra is OUTSTANDING. The combination of the custom designed long-throw woofer + custom port tube + rigidity and less energy loss of the bamboo cabinet gives the speaker a remarkable bass response (very punchy, dynamic and deep) with no bumps or inaccuracies.

I prefer using these speakers without a subwoofer, but they will benefit from being crossed over at about 60Hz and matched with a subwoofer built for sound quality.

I think the bass response will surpise you and if you have a sub, I think you will be turning it off :p

[Mag_Neato]

Sign me up, Dave!

Could there be a bamboo(m) sub in the works?

[curtis]

I swear Dave doesn't sleep.

[Mag_Neato]

Hey, if you can't make Jr. sleep......take advantage of the extra awake-time!

[Sam1000]

I prefer using these speakers without a subwoofer, but they will benefit from being crossed over at about 60Hz and matched with a subwoofer built for sound quality.

I think the bass response will surpise you and if you have a sub, I think you will be turning it off :p

I said earlier that you can book a pair+center, now after reading this, you can charge mt credit card too... ;)

[GirgleMirt]

The actual quasi-anechoic frequency response of the speaker is +/- 3dB from 44Hz to 22kHz. Expect -3dB in a typical room to be about 39Hz. Technically, the speaker is +/- 1.5 dB from about 55Hz to 22kHz.

Bass response from the Sierra is OUTSTANDING. The combination of the custom designed long-throw woofer + custom port tube + rigidity and less energy loss of the bamboo cabinet gives the speaker a remarkable bass response (very punchy, dynamic and deep) with no bumps or inaccuracies.

Ha! That somewhat makes more sens... It's funny how having information 'trickling' somewhat constantly alters your perception of the speaker... You see the response graph, think "well its a 5.5 inch after all, just not designed for low bass, designed to use for a sub", so you see it differently than you saw it before, but then turns out the graphs aren't valid, and they go down to like 40hz and has outstanding bass response...

Each announcement brings a new view of the speaker, guess we really should stop trying to 'figure it out' before the final announcements!

[curtis]

Thank goodness for the flexible bass management in my pre/pro!

[Mag_Neato]

Thank goodness for the flexible bass management in my pre/pro!

Curtis, if you have a S-1 @ each location you can set them globally to 60Hz! :D

[curtis]

Curtis, if you have a S-1 @ each location you can set them globally to 60Hz! :D
I know Dave said it was OK, but right now I just can't put a screw into the cabinets....I just can't.

[Dread Pirate Robert]

Well, I can say that this is the first time I've been amazed by a vertical dispersion measurement. :) For comparison, the CBM-170SE's performance in this regard is very impressive--good enough to be turned on its side and used as a center--and because of my particular arrangement, I can attest to the benefits of this characteristic with all of my speakers, but the Sierra-1's measurements are plainly flat-out better (I can't even tell where the crossover point is, either). When all is said and done, the defining characteristic of this speaker may be that it improves significantly in so many areas with so little compromise.


Yeah, from the graph it looks like it's +/- 3dB from ~75hz to 20khz. Which sounds great for sub integration.

Obviously, this depends on the frequency at which you wish to integrate (I'm thinking 80 Hz?). Based on my own experience, it is best to have as much "breathing room" as possible regarding the speaker's low-end response and the crossover frequency, otherwise you'd probably lose some upper/mid bass dynamics that the subwoofer would be able to handle better (i.e. without compressing at high volumes). Additionally, the high-pass filters used in most if not all of the common A/V receivers and preprocessors have a relatively shallow -12 dB/octave slope that was designed for speakers that have a similar slope, which is the typical case for sealed speakers but not for ported ones. And even then, with a typical sealed bookshelf-type speaker, I've found that you can lose dynamics if you cross over at 80 Hz or lower and too close to the -3 dB point of the speaker.

Ascend speakers are rather good at handling marginal integrations, and I'm sure that the Sierra-1 will be at least as good as the previous models in this regard, but you'll have to experiment rather than just going by measurements. Obviously, it also depends on what you listen to--for example, if you only listen to soft jazz, maybe you won't have to worry about the dynamic impact of gunshot sound effects so much. :)


Each announcement brings a new view of the speaker, guess we really should stop trying to 'figure it out' before the final announcements!

The excitement certainly is ratcheting up plateau by plateau--Dave is better at this marketing stuff than he gives himself credit for, and I think in this case, he's hardly trying (doesn't need to). ;)


Curtis, if you have a S-1 @ each location you can set them globally to 60Hz! :D

And some say that the 170SE is overkill for surrounds.... :rolleyes: ;)

[Dread Pirate Robert]

As with most frequency response graphs, the graphs are only valid to about 200Hz. Notice the "green" bars on the top and bottom that extend from 18Hz to slightly over 200Hz. They indicate the invalid portion of the response curve, this is caused by this distance from the 1st reflection point to the mic.

I'd like to point out that this also applies to the dispersion graphs of each of the other speaker models on this website.


Bass response from the Sierra is OUTSTANDING. The combination of the custom designed long-throw woofer + custom port tube + rigidity and less energy loss of the bamboo cabinet gives the speaker a remarkable bass response (very punchy, dynamic and deep) with no bumps or inaccuracies.

Sounds like it's going to be quite efficient, as well (don't forget to give us that spec!).


I know Dave said it was OK, but right now I just can't put a screw into the cabinets....I just can't.

I couldn't either, although I can understand how I might feel differently if I had built the things, as all Ascend speakers have mounting holes of some sort drilled into them at the factory.

If you feel that you need to mount your surrounds at an angle, you might want to look into small TV mounts that would support the speakers at the bottom (the BT-77 is nice but only angles down about 7 degrees). You'd have to find a non-destructive way to secure the speakers (e.g. a wire bolted to the existing attachment point plus Blu-Tack or generic equivalent), as well as a way to hang the mount from the rafter (e.g. a thick strip of metal into which you can drill appropriately placed holes).

[davef]

Sounds like it's going to be quite efficient, as well (don't forget to give us that spec!).

Efficiency is about average, to gain this type of bass response - you must sacrifice efficiency. My numbers indicate 87dB.

Average impedance is 8 ohms with a minimum impedance of 5 ohms. Impedance is VERY linear and the speaker is an easy load for all receivers and amps.

Because of the efficiency drop compared to our other products (which were all high-efficiency), I recommend a minimum of 50 watts.

[davef]

Hey, if you can't make Jr. sleep......take advantage of the extra awake-time!

Hah! And that is the problem --- I wouldn't classify it as "awake time". More like being a zombie.

My mistress Lunesta is calling my name tonight though :p

[Dread Pirate Robert]

Efficiency is about average, to gain this type of bass response - you must sacrifice efficiency. My numbers indicate 87dB.

Thanks for the spec--what service! :) Yes, I meant quite efficient for having a single, modestly-sized woofer with that level of bass response. 87 dB is pretty comparable to most competing designs, yet it reaches significantly lower than many (that I've seen).


Average impedance is 8 ohms with a minimum impedance of 5 ohms. Impedance is VERY linear and the speaker is an easy load for all receivers and amps.

Generally, other high-end bookshelf speakers I've seen with comparable bass and efficiency tend to be much harder to drive (e.g. 4 ohms nominal), so I think you've found a pretty sweet combination of design compromises and new technologies (such as the cabinet material).


Because of the efficiency drop compared to our other products (which were all high-efficiency), I recommend a minimum of 50 watts.

It's about equal to the HTM-200's efficiency, isn't it? This shouldn't impact too many people (aside from tube aficionados), but as always your honesty and frankness are much appreciated.

[Grayson73]

I think the bass response will surpise you and if you have a sub, I think you will be turning it off :p

I have to hear it to believe it. These speakers will produce enough bass for bass-intensive movies?

[curtis]

I have to hear it to believe it. These speakers will produce enough bass for bass-intensive movies?
I think Dave meant for music.

[BradJudy]

A -3db of 40Hz should be pretty nice. I totally wasn't thinking about the valid range of the graph.

I look forward to hearing them and to seeing more information.

[Dread Pirate Robert]

I have to hear it to believe it. These speakers will produce enough bass for bass-intensive movies?

It depends on what you mean by "enough." I suspect you'll want to leave your sub on for Master and Commander, for example. :)


I think Dave meant for music.

I would think so! :) His 60 Hz suggestion sounds right for the Sierra-1's frequency range for those who desire more lower end for music, but personally, I'd still at least consider using a slightly higher crossover frequency for movies just to make sure that this or virtually any speaker isn't working harder than it has to in reproducing those ridiculously hyped movie soundtracks we enjoy so much. Dave, if I'm totally off-base here, then please let me know.

Maybe it's just me, but I occasionally question crossing over my 170SEs even at 80 Hz. Granted, the Sierra-1 has far deeper and greater bass output, but at the same time, many soundtracks will begin to increase in loudness stupendously as the frequency gets lower, which is why an 80 Hz crossover is generally recommended even for floor-standing speakers. I don't own any HTM-200s, but if I did, I'd probably cross them over at 90 Hz or even 100 Hz (as much as I dislike the very idea for other reasons) if they were to be used at the front stage. Listening to music is a different scenario, although there could undoubtedly be exceptions.

[SteveCallas]

Congrats on completing the new design Dave.

One thing that I'm a bit puzzled about is that horizontal off axis FR measurements are almost always done in 15 degree increments up to 45 degrees. Every speaker review I have read does that and even the existing measurements for the 170s and 340s do that - it's basically the standard. With these Sierras, you're only showing 5, 10, and 15 degree measurements horizontally......that's not really much of a test me thinks. If a speaker's FR changes much over only a 15 degree window, you better use a heck of a lot of toe in and keep your head in one spot :(

[davef]

One thing that I'm a bit puzzled about is that horizontal off axis FR measurements are almost always done in 15 degree increments up to 45 degrees. Every speaker review I have read does that and even the existing measurements for the 170s and 340s do that - it's basically the standard. With these Sierras, you're only showing 5, 10, and 15 degree measurements horizontally......that's not really much of a test me thinks. If a speaker's FR changes much over only a 15 degree window, you better use a heck of a lot of toe in and keep your head in one spot :(

Hi Steve, no reason to be puzzled or speculative of that graph -- you are looking at a completely different graph with a completely different purpose. The symmetry graph is designed so that you can easily compare the off-axis response from one direction to the same angle in the opposite direction while also comparing to off-axis in a different plane. You can compare 15 degrees to the left of the speaker to 15 degrees to the right to 15 degrees below and 15 degrees above. The graphs you are used to seeing typically show horizontal off-axis in only one direction (left or right of the speaker), nor do they compare it to vertical directivity...

This is a graph that I have developed for my purposes, and to be honest, from a design standpoint -- much more revealing of soundstage and dispersion performance.

However, of course I have the "standard" graphs that you are used to seeing on our site and in various reviews -- actually thought I posted it in the thread but I guess I missed it. The horizontal dispersion of the Sierra is excellent.

I will send myself a reminder to post that graph tonight. I have to crop it to fit in the forum and I don't have the tools here in the office to do it (no photoshop or WS-FTP pro to upload from here)