2" Aura Whisper Waveguide Loaded

[Pete Basel]

Re: 2" Aura Whisper Waveguide Loaded

Dave you might have noticed that I've been saying for many years that flattening
the response is the correct way to do distortion testing and good to know that the
Mini DSP works well for this - I'll probably buy one.
I do like to see how the distortion rises at LF so I'll probably deliberately use a low
cutoff. It won't be seen as much with guide due to the gain obviously.

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

It probably would work other then the mounting plate would have to be modified.

Dave

[Thezeek]

Re: 2" Aura Whisper Waveguide Loaded

I was thinking that this 2" Tang Band may be a good candidate for your 11x6x2 inch wave guide. Any thoughts?

http://www.parts-express.com/tang-band-w2-800sl-2-aluminum-mg-full-range-speaker-driver--264-807

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

I offer any guide that is on my Picasa page. You can click the link from my web site. I just haven't spent the time to get them on my web site.


Pete,
I use a mini DSP. I try to flatten the FR then roll the bottom end off before the distotrtion starts to creep up, depending on the driver, with a fairly high spl. Usually between 90-100 dBs.

Dave

[Pete Basel]

Re: 2" Aura Whisper Waveguide Loaded

Nice work Dave, it looks like you flattened the frequency response (keeping some LF rolloff) before taking the distortion measurements. Wondering what software or DSP device you used to
do that?

[Face]

Re: 2" Aura Whisper Waveguide Loaded

gonna bump this up...

Dave, these results are really impressive. Do you still sell the WG that matches the Aura NS2? I see you have a fair amount of options on your site but don't see any that state compatibility with the NS2.


Also, any way you could test these in the 4.5" round WG? I'd really be interested to see those results. If not, do you have any testing done with that particular WG?

Unless you are looking just for directivity, I wouldn't bother with that small of a guide and this driver.

[ErinH]

Re: 2" Aura Whisper Waveguide Loaded

gonna bump this up...

Dave, these results are really impressive. Do you still sell the WG that matches the Aura NS2? I see you have a fair amount of options on your site but don't see any that state compatibility with the NS2.


Also, any way you could test these in the 4.5" round WG? I'd really be interested to see those results. If not, do you have any testing done with that particular WG?

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

I put the Aura into my 11 x 6 x 2" deep guide.

Flat baffle vs guide (black)


EQ'd flat and rolled off on the bottom


Distortion 85 dbs. best so far


Distortion 90 dbs. I wasn't able to get 90 dbs out of the flat baffle or the 8" guide.


It would be interesting to pair this with a 12" woofer.

Dave

[dlr]

Re: 2" Aura Whisper Waveguide Loaded

Thanks David,
I'll load Praxis on my laptop and test this out. So basically normalizing will make the flat baffle a flat line at 0 dbs and the guide will either show positive numbers if boosting and negative numbers if attenuating the signal, like what can happen on the top end?

Dave

Precisely. You get one output from the divide operation, the variance of the response in question to the reference response (divisor).

The graph shown has only the magnitude line. The phase was not important to me, but it is a complex math operation, so you can show the phase change if you wish. I don't find it useful, however.

One thing to note. In Praxis you will have to convert the input file to the data format used by Praxis before many of the options become available. Praxis makes that pretty easy. Each operation by default will open a new window. You can change that with each operation. It takes a little time learning how to work with it, but to me it's one of the most intuitive GUIs I've used. Bill Waslo is good at that.

dlr

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

Thanks David,
I'll load Praxis on my laptop and test this out. So basically normalizing will make the flat baffle a flat line at 0 dbs and the guide will either show positive numbers if boosting and negative numbers if attenuating the signal, like what can happen on the top end?

Dave

[dlr]

Re: 2" Aura Whisper Waveguide Loaded

What do you mean by " divide by the baffle? I don't follow how you would do this.

By that I mean to divide by the SPL response as measured on a flat baffle using the divide function in capable software. I don't know if the software that you use can do this. You can use the free version of Praxis to do this. It's very powerful and has many post-processing operations available.

The divisor is essentially the reference. Take an SPL measurement in a waveguide, then divide by the SPL response on a large (quasi-anechoic) flat baffle. The latter is the response of the driver only. The result of dividing the waveguide SPL by the flat baffle SPL shows the effects of the waveguide in isolation. The result is that the 0db represents the divisor response (flat baffle SPL as reference) with the variation around the 0db line being waveguide influence (for this particular example).

You can think of it as an equivalent to the diffraction curve you get from modeling a driver on a baffle, then exporting that response, the way it's done with the BDS.

For example, the first graph below shows the absolute measurements of the mid/tweeter in my 3-way. The second graph shows the same set of responses, but normalized to the on-axis response. Note that on the latter the on-axis response is a flat line. All other axes on the second graph are simply relative differences from the on-axis response. In my case, it shows the directionality with horizontal angle.




Those above were LAUD measurements that I processed with Praxis (IIRC), then imported them into SoundEasy for display.

This second set shows the impact of felt on a baffle. The first shows two absolute measurements, the second one shows the normalized result of the response with felt to the one without. This shows the change made by the felt in isolation. These are shown using the free version of Praxis.




dlr

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

Dave, let me suggest something that may help in your evaluations. If you're interested separating the changes due strictly to the waveguide, take the waveguide response on a given axis, then divide by the flat baffle response on that axis. The result will be a normalized response (if all test conditions remain the same) that is purely the influence of the baffle. Of course you want to know the response in the waveguide and work towards an acceptable result, but the normalized response will make it easier to tweak the waveguide.

What this may do is help to make an analysis with different waveguides, what in the guide changes the results. You can also take the off-axis responses in the guide and divide by the on-axis response in the guide to see absolute changes with angle more easily. With these you can create a set of normalized polar responses to compare guide to guide that has the divisor as the zero db basis. The actual divisor SPL non-linearities in SPL become moot. This is probably most useful with the same driver since each driver reacts differently to a guide, but you could build up a set of characteristics over time with multiple drivers.

I thought you might need more to keep you busy! ;)

dlr

What do you mean by " divide by the baffle? I don't follow how you would do this.
Sorry a little thick headed at times.
Dave



Dave

[dlr]

Re: 2" Aura Whisper Waveguide Loaded

Dave, let me suggest something that may help in your evaluations. If you're interested separating the changes due strictly to the waveguide, take the waveguide response on a given axis, then divide by the flat baffle response on that axis. The result will be a normalized response (if all test conditions remain the same) that is purely the influence of the baffle. Of course you want to know the response in the waveguide and work towards an acceptable result, but the normalized response will make it easier to tweak the waveguide.

What this may do is help to make an analysis with different waveguides, what in the guide changes the results. You can also take the off-axis responses in the guide and divide by the on-axis response in the guide to see absolute changes with angle more easily. With these you can create a set of normalized polar responses to compare guide to guide that has the divisor as the zero db basis. The actual divisor SPL non-linearities in SPL become moot. This is probably most useful with the same driver since each driver reacts differently to a guide, but you could build up a set of characteristics over time with multiple drivers.

I thought you might need more to keep you busy! ;)

dlr

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

Distortion at 85 dbs with damping on back of screen



Just for comparison this is before.


What a huge difference. It also was not maxed out at 85 dbs as before. Couldn't go any hire tonight or I'll wake up the family.


Davd

[davepellegrene]

Re: 2" Aura Whisper Waveguide Loaded

Thanks for the great work dave! You have my permission to remove that screen if you believe that the response will smoothen out. Overall, im very impressed with the work you have done and im greatly appreciate it. Im also shocked at that little driver!

I'll look into whether the damping material can be put inside then put the screen back over. If it's not removable without damage I can't see why not just put it over top like I did. It does the job.

Dave