Introducing Directiva - An ASR open source platform speaker project

[Newman]

To get a fair comparison, we would have to raise the frequency range around 100Hz by at least 11dB for the 6ND430 driver.

Quite the converse IMO, equalising both drivers to have the same output from 100 Hz up (given they have the same output at 100 Hz), you have to supress the output of the 6ND430 at higher frequencies by up to 11 dB.

Your attempt to raise its output by 11 dB at 100 Hz will only make it 11 dB louder than the SB15, and you have to turn it back down by 11 dB to match...

 

[ctrl]

Quite the converse IMO, equalising both drivers to have the same output from 100 Hz up (given they have the same output at 100 Hz), you have to supress the output of the 6ND430 at higher frequencies by up to 11 dB.

You don't understand what is meant by "average sound pressure level".

In my last post, I drew (visually estimated) the average SPL (average of 300-3000Hz) for both drivers as an orange line (as the reviewer measured the drivers).

Then for both drivers the SPL is adjusted, for example by measuring with an SPL meter, so that both average SPL are at 90dB (in our example, so that both orange lines are at 90dB).

The average SPL for both drivers is now 90dB. When both driver measurements are superimposed at 90dB, it looks like this (in the sketch it should of course be "range" not "rage" - Freud sends his regards):

Around 100Hz, the 6ND430 has about 11dB less SPL than the SB15NBAC30-8 driver. Therefore, the harmonic distortion in this frequency range is not comparable.

In the frequency range 600-2000Hz the SPL is congruent (red measurement curves) and thus the distortion is directly comparable here.

 

[gy-k]

Because of those two factors the 6ND430 can get about 4 to maybe 5dB louder below 100Hz before reaching xmax. For your use of crossing at 100Hz the 6ND430 would be a good option, the bigger size would change the directivity response higher up and it may not match to the DXT as nicely as the SB15 does in the R2.

Just one more thing about 6.5" drivers on a related note. The SICA 6H1.5CP-8 has similar values for Fs, Vas, Qts to the SB15, the SPL for speculation about distortion performance is closer, and their specs state 10% THD for Xmax and include Xvar.

 

[Rick Sykora]

Just one more thing about 6.5" drivers on a related note. The SICA 6H1.5CP-8 has similar values for Fs, Vas, Qts to the SB15, the SPL for speculation about distortion performance is closer, and their specs state 10% THD for Xmax and include Xvar.

Thanks, SICA has been brought up previously.

Looks promising enough but they have no US distribution so got shelved.

 

[Newman]

Thanks @ctrl for your time. I will let it drop -- I don't think the curves used for this analysis represent the way these 2 drivers would measure in the R2 cabinet anyway, so, wrong starting point, wrong end point. Also, the dibirama response for the 6ND430 looks a bit sus to me, reasons unknown, compared to its bass response on an IB, source. Even though that's an apple and an orange, whatever caused the massive 6ND430 rolloff at dibirama, I'm dubious. Would like to see the two drivers on an R2 cabinet for measurements, then we actually know.

cheers

 

[fluid]

Also, the dibirama response for the 6ND430 looks a bit sus to me, reasons unknown, compared to its bass response on an IB, source.

Just completely different scales, when the 6nd430 16 ohm is scale matched they virtually lay on top of each other

 

[Newman]

So where is the 11 dB rolloff?

 

[fluid]

So where is the 11 dB rolloff?

If you draw a line from the nominal sensitivity of the driver at 92.5dB and draw another line at 100Hz there is about 8.5 dB difference. If the nominal SPL for the distortion measurement was 92.5 the 100Hz level would be 8.5dB lower. To have the 100Hz levels match for distortion comparison at that frequency the nominal level would have to be 8.5dB higher.

In the SB 100Hz and 1K are at the same level so the distortion at the frequencies in between can be compared directly.

The box sim before showed that if you put both in a small sealed box and fed them the same power the level at 100Hz would be virtually the same, but the 6ND430 has much more output above that point as it is a rising response pro driver.

The problem is that both drivers were not measured with the same voltage going in but with it changed to create a certain SPL.

 

[giolight]

Thanks, SICA has been brought up previously.

Looks promising enough but they have no US distribution so got shelved.

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[Rick Sykora]

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Welcome to ASR!

Thanks for trying, but guess I needed to say established major distributor. The other US one at least has a website, but does not have any Sica product displayed.

There is one in Puerto Rico though! Oops, Lol it is the same guy!

Looking over Sica’s presence elsewhere, would appear they intentionally avoided being here. Seems odd and could not feel comfortable recommending to others. Seems a shame as I recall they had some interesting coaxial drivers.

Have you bought any product from them?

 

[giolight]

Yes I have bought from them but I'm in Italy. I agree the US distribution looks unreliable.

 

[fluid]

Looking over Sica’s presence elsewhere, would appear they intentionally avoided being here. Seems odd and could not feel comfortable recommending to others. Seems a shame as I recall they had some interesting coaxial drivers.

Have you bought any product from them?

The best place I have found to buy drivers from Sica included is TLHP in France.
https://en.toutlehautparleur.com/
If you register you can see the price you pay which is almost always better than shown on the site without logging in with an exact shipping quote.
For some drivers even including shipping they are cheaper than some local dealers, very reliable and ship quickly. Obviously import and tax considerations will be different depending on where you are.

I have no choice but to buy almost everything I want from overseas so I use them a lot. Sica drivers are very high quality and in quantity the prices can be very low, I bought 8 x 5" drivers on impulse because they were just over 20 Euros each even though the site lists 49.90 for one without logging in.
https://en.toutlehautparleur.com/speaker-sica-5f1-5cp-16-ohm-5-inch.html

 

[YSDR]

For the 6ND430 driver we get, that at reference SPL, the SPL@100Hz is 11dB down.
View attachment 182429

The graph looks different than of the 6ND430, here it is the real 6ND430-8:
http://www.dibirama.altervista.org/...und-6nd430-8-mid-woofer-6-8-ohm-500-wmax.html

 

[Rick Sykora]

Please cut out the spec banter on drivers. If you feel a need to do more driver analysis, start another thread. Have already had enough complaints over the length of this thread and its organization.

It is a team decision to select drivers and we are staying with the 4 ohm SB15NBAC for now. It has a great set of features and is a good value. This thread is not meant for minutae.

Thanks!

Rick

 

[ctrl]

@Rick Sykora sorry, I need to make a last post about this topic, an error correction.

CORRECTION
As @YSDR and @fluid already pointed out:

Sorry, folks I somehow used the wrong FR measurement for 6ND430 (have accidentally used the measurement of a midrange driver, maybe this wasn't so bad, as it points out how absurd the HD-only comparison is, as this driver shows @50Hz@102dB lower HD than both drivers discussed - anyone needing more discussion, please in a new thread, happy to help there).

Below you can see the correct measurements and evaluations.

All my statements in post#1078 and post#1082 are still valid, you just have to replace -11dB with -7dB (unfortunately I can't change my posts anymore).

The real 6ND430-8 evaluation - replace mentally in my previous posts, the wrong diagram with this one.

Again, sorry for the confusion caused - how to complicate a simple topic? This way!

 

[Newman]

Thanks for the correction @ctrl . Like I said #1085 I will let it drop: too much minutae and other factors still make the comparison less relevant than fitting the 2 drivers into an R2 box and measuring.

 

[test1223]

Hello,

very interesting project.

I have a question regarding the cardioid characteristic. If you place the speaker next to a wall the sound of the woofer, the phase shifted ports and both reflections from the back wall will interfere with each other. The resulting characteristic shouldn't look as good am I right? So which distance to the wall in the back is okay?

Best
Thomas

 

[howard416]

Hello,

very interesting project.

I have a question regarding the cardioid characteristic. If you place the speaker next to a wall the sound of the woofer, the phase shifted ports and both reflections from the back wall will interfere with each other. The resulting characteristic shouldn't look as good am I right? So which distance to the wall in the back is okay?

Best
Thomas

I bet you could come up with a reasonable approximation of this scenario in VituixCAD.

 

[fluid]

I have a question regarding the cardioid characteristic. If you place the speaker next to a wall the sound of the woofer, the phase shifted ports and both reflections from the back wall will interfere with each other. The resulting characteristic shouldn't look as good am I right?

You can see a Vituix example of looking at how walls affect the response of a Cardioid speaker, and the front one is not much of a problem as in the troublesome SBIR frequencies there is not much being directed there. The side walls and ceiling are the bigger problem.

https://www.audiosciencereview.com/forum/index.php?threads/dutch-dutch-8c-review.21016/post-989007

And a further BEM simulation to show the difference between a free space and wall placed behind a cardioid speaker and the affect it has on the pattern shape.

https://www.audiosciencereview.com/forum/index.php?threads/dutch-dutch-8c-review.21016/post-990590

 

[test1223]

You can see a Vituix example of looking at how walls affect the response of a Cardioid speaker, and the front one is not much of a problem as in the troublesome SBIR frequencies there is not much being directed there. The side walls and ceiling are the bigger problem.

https://www.audiosciencereview.com/forum/index.php?threads/dutch-dutch-8c-review.21016/post-989007

And a further BEM simulation to show the difference between a free space and wall placed behind a cardioid speaker and the affect it has on the pattern shape.

https://www.audiosciencereview.com/forum/index.php?threads/dutch-dutch-8c-review.21016/post-990590

Thank you

So best practice would be to use a wide baffle or bigger midrange driver combined with a low frequency supercardioid to minimize problems? Can you do this without increasing the distance of the two (or more) sources?

Did you get a lower R60 with all cardioids or dipoles and frequencies due to the cancelation at some points in the room if you linearize the frequency response below schroeder frequency at the listening position?