Best new midwoofer?

[dthomas]

Re: Best new midwoofer?

I'll ask the foolish questions. Why would I buy this mid-woofer over the Peerless 830875 or Tang Band W6-789E? (These are examples that give you the idea.) I want to learn, really. This is a "price point" I don't look at normally. I understand the principals of low distortion and excellent low Fs, but otherwise, most of this is over my head. Jeff B. ,I know you are a reliable source and can help an idiot like me.

The W6-789E is a beast of it's own. Bass is just ok but the midrange clarity of that driver is amazing. I have 4 stashed away that are going to be an MTM above a pair of RS225s with a BG Neo 3. So a WWMTM.

Look at the moving mass of the W6-789E it is very small compared to most 6.5" midwoofers I think this is what makes it's midrange so detailed and pleasing to listen to. On the other hand it could well be why it is just so-so in the sub 100Hz region. Bass sounds bloated and boxy.

[dlr]

Re: Best new midwoofer?

Diffraction.

And with a narrow baffle like most use, that bump at the transition will show up over a fairly wide listening angle.

I thought that might be your answer. I haven't often seen it improve the situation a lot in this area. I've also seen it be worse. It's also in the area where our hearing is most sensitive, so I've always been reluctant to consider a driver with this issue, even if it is a dip.

Linear distortion is my concern, not the non-linear. I'm still not convinced of the ultimate audibility of distortions that we measure once the levels are down to a reasonable level (whatever that value is).

dlr

[ErinH]

Re: Best new midwoofer?

I'm still going to say the illuminator would be the woofer of choice here. The 18wu has nearly twice the linear throw as tested by Patrick Turnmire for Voice Coil. 4.6mm limited by suspension for the Satori, whereas the Scan illuminator gets 9.1mm IIRC.


Of note, Vance Dickason's test results mimic yours, Jeff. His results show a rise in distortion at 1.2khz as well as a rise in FR here. His off axis FR plots, however, show no spike in this region.
Unlike your results, however, there's a rising distortion trend starting around 150hz. This brings up my question before: what are your test parameters? What distance was the mic for testing? I know the omnimic is calibrated for SPL so if you're doing nearfield measurements, it's a bit misleading for distortion measurements as the level In the farfield would be lower. Just trying to get a gauge here is all.

Edit:
Scan illuminator 18wu Klippel data:

http://www.diymobileaudio.com/forum/klippel-reviews-driver-specs/115001-scanspeak-illuminator18wu-4741t00-klippel-test-data.html

This is my data. VC mag actually has it being about 1mm better.
Again, I'll be happy to put them on my klippel if someone is game. Or we can go with the data already out there.

[Jeff B.]

Re: Best new midwoofer?

Here's a lttle more......

OK. This is going to be the final set on this driver, I believe.

Like I did with the N26 Tweeter earlier, I ran distortion sweeps on this woofer again, but at much higher level. These were ran at 100dB to the mic at 1 Meter from the speaker. As mentioned in the other post, this was very LOUD and my amp was turned up higher than I hardly ever go with it when listening to anything. So, without further ado, here it is:


Still excellent nonlinear behavior.


Here is the CSD waterfall for the Satori. From this we see that the 1200 response anomaly is a real resonance that clearly shows up in this decay:


Everyone should really take a look at what Bill says about CSD's in the User Guide for OmniMic. They may show energy storage, but they are also offer a very poor correlation to what we hear versus what we see in the graph, so they should not be given too much weight. CSD's often clearly show types of resonances that we can not hear, while hardly showing at all resonances that can clearly be an issue when listening. As I have already said, this one above falls in the category of something that is likely inaudible.


As Dave (dlr) requested, here is the on-axis and a 45 degree off-axis plot overlaid (I used PCD because I forgot to snapshot in OmniMic, but I did grab frd's of both). The dip does smooth out considerably off-axis, but it's hard to say if it's completely clean. As Dave said, it may be a spider resonance, or possibly could still be from the surround.



Jeff B.

[ErinH]

Re: Best new midwoofer?

Jeff,
Can you please answer my questions above regarding your test setup and procedures so I can better understand the data?

Thanks

[Jeff B.]

Re: Response and Distortion plots.

X2

What kind of windowing do you use, what stimulus, and what is your room like? It looks as though you have an anechoic chamber or are nearfield. I've not been able to get that smooth of a response in the farfield ever. I'm jealous!

The speaker was mounted on a 16" x 9" baffle with acoustic foam and thick felt on the front around the woofer. It was placed on the floor in the middle of my family room facing up. I mounted the OmniMic on a boom that extends over the speaker facing down. I usually have it about 2-3 feet above the driver, sometimes closer depending on what I am trying to measure. I then run a few implulses and look for ripples and then set my window as far out as possible before any distrurbances show up.

In the case of the frequency response plot I show below I used a 13 mSec window gating, with 1/48th Octave smoothing and set the OmniMic to a "Blended" response. Doing exactly as I described netted me this graph:



Here's another done on a different day, with the same driver, but pretty much the same method:


This distortion test at 100dB @ 1 Meter was done the same way as the graphs above:


The whole key for me is finding the best method for reducing the room reflections that show up in the impulse. If you can get all of the reflections that show in the implulse moved out to beyond 8 mSec you can usually get a pretty decent plot. However, sometimes I have just sat a speaker in the room and used a "blended response" with a 3 mSec gate and just lived with it.

As you can see, my graphs shown here are snapshots in OmniMic, so there is no post-processing of the graph in any way. That's the raw measurement being shown.

Jeff

[Jeff B.]

Re: Best new midwoofer?

Jeff,
Can you please answer my questions above regarding your test setup and procedures so I can better understand the data?

Thanks

See my response above

[mzisserson]

Re: Best new midwoofer?

Jeff,

Thanks for the info. It is interesting how it shows up heavily in even order distortion, and is likely why it is a non-issue.

Just being a why guy, is there any sort of reason why this storage is showing up as even order distortion while other bits of storage show up as odd? FWIW I like it's off axis responce.

[internova]

Re: Response and Distortion plots.

Jeff - thanks very much. I'll try in my room, using other driver of course. Satori's price tag is still too steep for me. ;)

The speaker was mounted on a 16" x 9" baffle with acoustic foam and thick felt on the front around the woofer. It was placed on the floor in the middle of my family room facing up. I mounted the OmniMic on a boom that extends over the speaker facing down. I usually have it about 2-3 feet above the driver, sometimes closer depending on what I am trying to measure. I then run a few implulses and look for ripples and then set my window as far out as possible before any distrurbances show up.

In the case of the frequency response plot I show below I used a 13 mSec window gating, with 1/48th Octave smoothing and set the OmniMic to a "Blended" response. Doing exactly as I described netted me this graph:



Here's another done on a different day, with the same driver, but pretty much the same method:


This distortion test at 100dB @ 1 Meter was done the same way as the graphs above:


The whole key for me is finding the best method for reducing the room reflections that show up in the impulse. If you can get all of the reflections that show in the implulse moved out to beyond 8 mSec you can usually get a pretty decent plot. However, sometimes I have just sat a speaker in the room and used a "blended response" with a 3 mSec gate and just lived with it.

As you can see, my graphs shown here are snapshots in OmniMic, so there is no post-processing of the graph in any way. That's the raw measurement being shown.

Jeff

[DDF]

Re: Best new midwoofer?

A word of caution Jeff. Resonances constant over angle of observation aren't too bad IMO especially if they can be corrected, but those that change with listening angle are quite audible IME, especiallyin this frequency range. This was my experience after months and more of tweaking a B110 with this behaviour. I know others with the same experience.

Why does the OmniMic guy feel a poor CSD isn't a big issue? I read and reread and reread Olives studies on the audibility of resonance and reflection, and he found a correlation between audibility of resonance and audibility of frequency response abbe-ration that it causes That's a 5 dB hole, how can that not be audible?

[mzisserson]

Re: Best new midwoofer?

[QUOTE=DDF;1785017]
Why does the OmniMic guy feel a poor CSD isn't a big issue? I read and reread and reread Olives studies on the audibility of resonance and reflection, and he found a correlation between audibility of resonance and audibility of frequency response abbe-ration that it causes That's a 5 dB hole, how can that not be audible?[/QUOTE.]

I am no expert here, but I have seen, and studied such resonance and odd-holes. I will say from what I can see on paper vs. what I hear, It is extremely frequency dependent. If these abberations occur at some multiple of pi-radii from where the speaker is to the listeners ear, it is not unlike a room mode effecting a subwoofer. It also depends if the driver is in it's conical radiating pattern or not. It seems most cabinet resonance has a far worse effect on the sound if you are lower than the room-transition point. I feel because the the reflected sounds are first arrivals, they are much more likely to be reactive with the sound before getting to your ear, where above the room-transition your bran is receiving and processing the direct sound from the cone first. From what I can tell also, it seems the inverse is true of drivers, to a degree, and depending on the order of distortion, this can easily be inaudible.

I did this all with a resonant cabinet and a tone generator set to the resonance. Set up a mic at a few locations, listened, and played around a little. Just trying to make sense of what all the squiggles man on a CSD. I lack the sophistication to take it much deeper, but it seems to have worked for me and has become a serious part of my design process when considering cabinet proportions, brace placement, port placement, wall thickness, and dampening stratiges. All FWIW, Brain fodder, ect, et al, it's a hobby.

[Jeff B.]

Re: Best new midwoofer?

A word of caution Jeff. Resonances constant over angle of observation aren't too bad IMO especially if they can be corrected, but those that change with listening angle are quite audible IME, especiallyin this frequency range. This was my experience after months and more of tweaking a B110 with this behaviour. I know others with the same experience.

Why does the OmniMic guy feel a poor CSD isn't a big issue? I read and reread and reread Olives studies on the audibility of resonance and reflection, and he found a correlation between audibility of resonance and audibility of frequency response abbe-ration that it causes That's a 5 dB hole, how can that not be audible?

Dave,

First, the OmniMic guy is the Praxis guy is the LMS guy is Bill Waslo, the originator of the frd file that we all copy. So, it's not like he doesn't have a lot of experience here. Here is an paste of exactly what he said in the guide, which I agree with in principle and in experience: "Waterfall plots are useful in identifying moderate to high Q resonances in a drivers's frequency response. The audibility of the features easily identified in waterfall plots is somewhat controversial, with some research indicating that the higher Q resonances seen in waterfall displays are significantly less audible than low-Q resonances not as visible in waterfall displays". I believe what Bill says here to be accurate; lower Q - wider bandwith anomalies are more audible than higher Q - narrow resonances are. In addition, dips are much less audible than peaks.

Second, a frequency response anomaly that changes significantly with a change in axis is acoustical in nature (diffraction being an excellent example). Whereas a response anomaly that remains fairly consistent over a wide range of axes is mechanical in nature; being caused by some mechanical cone, spider, duscap, etc. resonance.

The acoustical type can often fill in very nicely in the power response, and if it is a narrow dip, be very difficult to discern at all. A mechanical resonance, on the other hand, will require some type of intervention (ie; notch filter, DSP, etc.).

Diffraction peaks and dips that fill in with axial change are not very audible, the ones that can't fill in (like baffle step) are. It all comes down to what is causing the dip here. The lack of signature in the 3rd order plot appears to indicate that it is not from the motor. The change off axis may indicate surround diffraction. I will investigate this a bit further, but my experience leads me to think this will not be very noticeable at all.

Jeff

[DDF]

Re: Best new midwoofer?

Jeff,

Bill's an experienced old hand at measurement gear but it doesn't make him an expert in resonance audibility. Even his comment was a generic and extremely well known trait. That was trotting out a famous name to "prove a point", I think enough said there.

Definitely the audibility is related to the BW. Judging by the distortion plot, that's a pretty broad bandwidth notch right in a frequency range where the ear is very acute.

I've long been an advocate of not necessarily making on-axis ruler flat by equing to the exact diffraction signature just at one point in space. But this isn't diffraction. There is nothing to indicate that this dip is "filled in" off axis.

Take it FWIW, my experience is that drivers that inherently radiate significantly different signatures at different axes, and not due to diffraction, result in less transparent sound that are very hard to voice.

I know Lynn Olson's posted the same. YMMV

Dave

[ErinH]

Re: Best new midwoofer?

I'm gonna toss this out there one last time and then I'll shuttup, just in case it was missed.

If someone who owns these wants me to klippel it so you can have a direct comparison against the Scan 18wu, I'm happy to do it.

Or, if we want to go off what Voice Coil mag already states, the 18wu has twice the linear throw and based on what data I've seen between the two is the clear winner (yes, I said clear) for a midwoofer application between the two.
HOWEVER, the 18wu runs about $120/pair more. But, again, if the application calls for a long throw midwoofer the Scan would be my choice. I consider it the better option and I've honestly yet to see a 7" driver that outperforms it in low end and higher end as a driver for a 2-way system. I'm not saying it's not out there. I'm just saying I'm not aware of it.
Now, for 3-way as dedicated midbass... that's a different story.

[Jeff B.]

Re: Best new midwoofer?

I'm gonna toss this out there one last time and then I'll shuttup, just in case it was missed.

If someone who owns these wants me to klippel it so you can have a direct comparison against the Scan 18wu, I'm happy to do it.

Or, if we want to go off what Voice Coil mag already states, the 18wu has twice the linear throw and based on what data I've seen between the two is the clear winner (yes, I said clear) for a midwoofer application between the two.
HOWEVER, the 18wu runs about $120/pair more. But, again, if the application calls for a long throw midwoofer the Scan would be my choice. I consider it the better option and I've honestly yet to see a 7" driver that outperforms it in low end and higher end as a driver for a 2-way system. I'm not saying it's not out there. I'm just saying I'm not aware of it.
Now, for 3-way as dedicated midbass... that's a different story.

Yes, I got your point each time it was made. I do not, however, have a driver I can send you for testing at this time. I never said the SB was better than the Scanspeak; I only asked if the SB was the best new woofer - meaning new stuff just coming out. I wasn't pursuing a contest, I was only trying to post some information on somenthing new. You may stick with the Scanspeak, that is fine with me.