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(4) Sealed 21": Funk Audio UH-21v1


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#21 MemX

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Posted 31 August 2016 - 12:30 PM



The features they share in common are: a decrease in box resonance frequency, a boost in sensitivity and efficiency that starts in the mid band and grows with increasing frequency up to a strong peak somewhere in the upper end of the response.  There is a corresponding impedance peak here as well.  I believe excursion is also reduced somewhat over most of the range.  Unfortunately, the location of the first peak from the slot load varied substantially depending on what modelling approach was used.  The model with the throat chamber had a much smoother top-end as well.  However, regardless of the modelling approach, I did not find a slot-load cabinet design with suitable dimensions whose first peak fell below 100 Hz.  Enhancement of output in the 20-40 Hz range was pretty poor, IIRC hitting +3 dB at 40 Hz in the best case.  I suspect my problem here is simply one of geometry.  I don't know horn theory too well yet, but I imagine I need either a longer slot length or greater exit area than I can accommodate without giving up valuable internal volume.

 

From memory of my reading on PPSL, the decrease in resonant frequency (of the drivers - and therefore the box?) and the increase/peak towards the top end of the band/range are both features seen in PPSL boxes.

 

Again IIRC, the depth of the slot is the biggest influence on the response range - the bandpass effect of the slot means that only the longer wavelengths escape, so I think that a deeper slot reduces where the peak in response falls, if I have the slightest clue what I'm talking about (which is not guaranteed... :P lol).  I'm not sure if a deeper slot reduces the resonant frequency or not, though?

 

 

WRT to the thoughts about differences in slot width/geometry due to the exact excursion of the drivers at any given time, is it really an issue?  (Not a rhetorical/sarcastic question because I honestly don't know!)  As I sit here and ponder on it now, surely any horn-type arrangement will have differing geometry at any given driver excursion?  i.e. a driver at rest will have, say 2" from the cone edge to the face of the internal wall opposite, which will increase and decrease as the driver moves back and forth in its range? giving a differing pressure experienced in the area between the cone and the wall as the driver moves back and forth?

 

I'm not really sure where I'm going with this train of thought TBH...  :lol: lol



#22 SME

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Posted 31 August 2016 - 07:26 PM

The drivers facing each other version sounds like the way a PPSL is modelled. AIUI this is generally described as an OD so S1-S2 forming the rear of the slot and S2-S3 the front of it. This means you'd set S1-3 to some constant value according to the area of the slot and set the lengths accordingly, set to a sealed back chamber and use Vrc/Lrc as usual to define the size of it.

 

Hmm.  I can give this variation a try, but I don't expect results compelling enough to change my plan.  Dunno.  Actually, leaving the slot open at the rear of the cabinet but putting it against the wall may help to effectively lengthen the slot by quite a bit, so maybe I should include that as a separate horn segment as well.  By OD, do you mean omni-directional?  I'm not sure how to configure Hornresp this way, but I'll put some more time in and see if I can figure it out.

 

Thanks.



#23 3ll3d00d

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Posted 31 August 2016 - 07:30 PM

Hmm.  I can give this variation a try, but I don't expect results compelling enough to change my plan.  Dunno.  Actually, leaving the slot open at the rear of the cabinet but putting it against the wall may help to effectively lengthen the slot by quite a bit, so maybe I should include that as a separate horn segment as well.  By OD, do you mean omni-directional?  I'm not sure how to configure Hornresp this way, but I'll put some more time in and see if I can figure it out.

 

Thanks.

go to Driver Arrangement (Ctrl+D) and change the dropdown to Offset Driver OD

 

there's a good summary of the options here -> http://www.hometheat...m-everyone.html

 

I don't think this is comprehensive for all the options hornresp has today but I found it useful for understanding what the different params in hornresp correspond to in different arrangements



#24 SME

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Posted 31 August 2016 - 08:12 PM

WRT to the thoughts about differences in slot width/geometry due to the exact excursion of the drivers at any given time, is it really an issue?  (Not a rhetorical/sarcastic question because I honestly don't know!)  As I sit here and ponder on it now, surely any horn-type arrangement will have differing geometry at any given driver excursion?  i.e. a driver at rest will have, say 2" from the cone edge to the face of the internal wall opposite, which will increase and decrease as the driver moves back and forth in its range? giving a differing pressure experienced in the area between the cone and the wall as the driver moves back and forth?

 

By my theoretical reasoning, yes.  Measurements would be helpful to confirm its existence, but it won't really show up as IMD without using multi-tone test signals.  The severity will depend a lot on the specific design though.  The narrower the region that the drivers fire into, the greater the effect will likely be as the slot size modulation is much greater as a percentage, and of course it depends on actual excursion required for the SPL you want.  Sealed boxes are likely to suffer more than ported boxes at the same SPL (and above the tuning frequency) because the sealed will need more excursion.

 

Yes, I can see this being a potential problem with a lot of horn designs, but mid and high frequency horns are probably more immune as they just don't involve much excursion anyway.  Likewise, I doubt you're going to encounter distortion from the M.A.U.L. unless the drivers are moving a lot.  So for example, a 30 Hz tone playing at, say, > 125 dB at 2m GP may cause any mid bass played at the same time to sound yucky and distorted.  (I'm taking some liberties with numbers here as I don't know what actual excursions are involved).  Is that an issue?  Surely the answer depends on the application.  In your living room or car, perhaps not if you aren't pushing it to extreme levels.  In a pro-sound setting, you might be playing to an audience at 20m away, and it could come into play.

 

Then there's the whole messy problem of how much distortion of what kind is audible.  The correct answer is that it depends.  It depends a lot on the linear distortion characteristics (acoustics) of the listening environment, on the content, and on the nature of the distortion.  Even small amounts of distortion can be very audible under the right (or wrong) circumstances, but this might only be the case 1% of the time with real content.  That 1% might matter though if the distortion is especially offensive.  I also wouldn't be surprised to learn that distortion has greater impact on transient content, which again may make it less relevant if your room acoustics are still doing greater damage to the sound.  It's way too complicated to figure out how much some particular distortion matters and much easier to make a best effort to avoid it where possible.

 

Edit: I just looked at the M.A.U.L. CEA results and distortion data, and it looks like the thing may still be a long way from excursion limits when the amp taps out at 30 Hz.  The distortion is a bit high there, but that is most likely because of the high acoustic amplification of the 2nd and 3rd harmonic from the horn loading.  So it might sound fine with 125 dB @ 30 Hz @ 2m GP.  Nevertheless, if one were to upgrade the amp and wanted to get every last dB out of the thing, the IMD problem could prove to be the biggest issue.  (It's also possible that IMD from the driver itself could be a major problem, for example if inductance is especially non-linear in stroke or current).


Edited by SME, 01 September 2016 - 06:15 AM.


#25 SME

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Posted 07 September 2016 - 06:37 AM

My drivers have shipped!  I'm not sure yet if I'll get them Friday, but they are definitely on their way.

 

go to Driver Arrangement (Ctrl+D) and change the dropdown to Offset Driver OD

 

there's a good summary of the options here -> http://www.hometheat...m-everyone.html

 

I don't think this is comprehensive for all the options hornresp has today but I found it useful for understanding what the different params in hornresp correspond to in different arrangements

 

Hey, thanks.  I actually read the beginning of that tutorial but didn't realize the info I needed was further down.

 

I did some additional simulations using the offset drivers option a week ago.  I already forgot most of the details, but I think I will stick with my original design of just a standard D.O. box and 6-7" driver clearance beside the racks.  The additional simulations I did gave me more confidence.  I may choose to divide the air space with a barrier, just in case they show any tendency to move out of phase.

 

My plan is to finish the cabinets with Duratex but aiming for a smooth matte finish to match the rack cabinets.  I saw a DIY thread on how to do this finish somewhere, but I don't remember where right now.  I just know it's do-able and is what I want.



#26 Funk Audio

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Posted 07 September 2016 - 07:24 PM

So due to the confusion that seems to be happening with the GUJV1 motor being a Focusworks Audio product, and the GUJV2 being Funk Audio, we have decided we should rename it before putting it up for sale. What does everyone think of; UHFA(driver size) Mk1?, (under hung funk audio, mark one).



#27 chrapladm

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Posted 08 September 2016 - 12:00 AM

WOW thats a lot of letters. BUT doesnt bother me which you decide. I will most likely just call it the UH18 or 21 for short..


"Music is not in the notes, but in the silence between."


#28 Funk Audio

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Posted 08 September 2016 - 12:05 AM

WOW thats a lot of letters. BUT doesnt bother me which you decide. I will most likely just call it the UH18 or 21 for short..

We are open to suggestions, UH21 Mk1 could work.



#29 chrapladm

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Posted 08 September 2016 - 12:10 AM

I like the UH21 Mk1 myself.


"Music is not in the notes, but in the silence between."


#30 dgage

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Posted 08 September 2016 - 12:37 AM

So due to the confusion that seems to be happening with the GUJV1 motor being a Focusworks Audio product, and the GUJV2 being Funk Audio, we have decided we should rename it before putting it up for sale. What does everyone think of; UHFA(driver size) Mk1?, (under hung funk audio, mark one).

 

I concur with the UH21 as the FA in the model would be redundant since it will often be referred to as the Funk Audio UH21, Funk UH21, FA UH21, or simply UH21, which is great if it becomes so well-known that UH-21 is all that is needed.


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#31 SME

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Posted 08 September 2016 - 07:09 AM

UH-21 Mk1 works for me.



#32 Funk Audio

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Posted 08 September 2016 - 04:39 PM

UH-21 Mk1 works for me.

Ok that's what it is then. Its official


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#33 Ricci

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Posted 08 September 2016 - 09:06 PM

Edit: I just looked at the M.A.U.L. CEA results and distortion data, and it looks like the thing may still be a long way from excursion limits when the amp taps out at 30 Hz.  The distortion is a bit high there, but that is most likely because of the high acoustic amplification of the 2nd and 3rd harmonic from the horn loading.  So it might sound fine with 125 dB @ 30 Hz @ 2m GP.  Nevertheless, if one were to upgrade the amp and wanted to get every last dB out of the thing, the IMD problem could prove to be the biggest issue.  (It's also possible that IMD from the driver itself could be a major problem, for example if inductance is especially non-linear in stroke or current).

 

That's correct. The drivers are not near xmax in the bandwidth when the amp runs out.

THD high? It's under 12% from 13-94Hz during the loudest sweep and that's with the amp giving out and the loading of the upper bandwidth boosting some of the THD harmonics. In band excursion max should be near 21-23Hz. Consider the output levels during this as well. Once you drop the output back 5-10dB the THD drops well down. Actually it's one of the more natural and cleaner bass systems I've heard due to the extremely low distortion and huge headroom. Very little driver excursion is used. The problems with it's performance and sound happen up above 90Hz and it's not really meant to be used that high so I consider that stuff out of band. I tried it run up to 120Hz or so and I just couldn't get it to behave. It gets wonky if it isn't low passed and equalized correctly. 

 

Those drivers are some of the best air pumps with regard to inductance variation versus stroke,due to the coil arrangement and motor design. 

 

I'd worry more about the structural integrity of some areas in the cab rather than IMD. The compression ratio and air speeds in the slot/horns is not very much comparatively and the driver excursion isn't much unless driving the hell out of it near 20-30Hz. 


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#34 SME

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Posted 09 September 2016 - 06:39 AM

That's correct. The drivers are not near xmax in the bandwidth when the amp runs out.

THD high? It's under 12% from 13-94Hz during the loudest sweep and that's with the amp giving out and the loading of the upper bandwidth boosting some of the THD harmonics. In band excursion max should be near 21-23Hz. Consider the output levels during this as well. Once you drop the output back 5-10dB the THD drops well down. Actually it's one of the more natural and cleaner bass systems I've heard due to the extremely low distortion and huge headroom. Very little driver excursion is used. The problems with it's performance and sound happen up above 90Hz and it's not really meant to be used that high so I consider that stuff out of band. I tried it run up to 120Hz or so and I just couldn't get it to behave. It gets wonky if it isn't low passed and equalized correctly. 

 

Those drivers are some of the best air pumps with regard to inductance variation versus stroke,due to the coil arrangement and motor design. 

 

I'd worry more about the structural integrity of some areas in the cab rather than IMD. The compression ratio and air speeds in the slot/horns is not very much comparatively and the driver excursion isn't much unless driving the hell out of it near 20-30Hz. 

 

Yeah.  It's funny how most distortion problems go away when you add more drivers.  :)


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#35 chrapladm

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Posted 09 September 2016 - 02:43 PM

Well BC prices seem to have just sky rocketed for me now so I am very interested in hearing more about these 21's and their 18" brothers.


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#36 SME

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Posted 14 September 2016 - 08:19 AM

The drivers came in yesterday.  I updated the first post with pictures and some specs.

 

The free air tests impressed me.  I didn't get any precise excursion measurements, but these can move some serious air.  There was a point at which the driver looked utterly violent, compelling me to take a few steps back, yet all I could hear was the swisha-swisha sound of air being forced through the vents.  I think I might have been at around 2.5" peak-to-peak at that point, but I did not have a good visual reference.  Distortion grew gradually with each 0.5 dB click above that, and I didn't go much farther so as not to put too much heat into it with low frequency sine waves.  I was pushing up to around 1 kW, depending on frequency, but FWIW, the magnet/motor housing was still cold after the tests.

 

The other remarkable thing is how light they are.  Yeah, they are something like 45 lbs, but considering the size, it doesn't feel like much.


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#37 chrapladm

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Posted 14 September 2016 - 10:14 AM

Just so I understand this correctly, does the UH21 have a 30mm Xmax?

 

The UH21 looks very similar to the SW152 in a 200 liter cabinet with double the voltage.(response shape wise) That pushes it to about 31mm with 1050watts. Does a little better down low than the SW152 but just a touch. Happy to see it does look good in a few of the horn designs I have. AND I LOVE THAT CONE. :D

 

AND did you say 4.5cuft for the pair of 21's? AND do you have any more pics of the cone?

 

Curious if that is like the Aura 18's cone or just the picture.


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#38 Funk Audio

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Posted 14 September 2016 - 03:30 PM

I believe he said 4.5 per driver.

 

Are you talking in sim land?  :rolleyes:. Real world is a little different sometimes.

 

Based on our in house tests compared to the 21.0, the UH21 given the same power in the same box ~3 cubic feet internal, the long term output sweep was about 1-2db lower across the board, although distortion under 60hz was a little better. Throw it in about 7 cubic feet and long term sweep output was 1-2 db higher than the 21.0 under 50hz, along with much lower distortion. In 4.5 it should be fairly close to that, as 7 is too big, didn't actually take much power in the low end. So overall long term output in 4.5 cubic feet should be similar to the GUJ21v1 as tested 20hz down(but with much lower distortion), about halfway between the GUJ21v1 and the 21.0 20-40hz about the same as the 21.0 50-60hz, and a couple db below the 21.0 above 60hz.



#39 SME

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Posted 14 September 2016 - 06:32 PM

Just so I understand this correctly, does the UH21 have a 30mm Xmax?

 

The UH21 looks very similar to the SW152 in a 200 liter cabinet with double the voltage.(response shape wise) That pushes it to about 31mm with 1050watts. Does a little better down low than the SW152 but just a touch. Happy to see it does look good in a few of the horn designs I have. AND I LOVE THAT CONE. :D

 

AND did you say 4.5cuft for the pair of 21's? AND do you have any more pics of the cone?

 

Curious if that is like the Aura 18's cone or just the picture.

 

I'm going to try to give them 4.5 cuft per driver.  I don't think I have been given an official manufacturers "Xmax" figure, but 30 mm is probably a good guess, similar to the Focusworks 21GUJV1.  Xmech, I believe, is closer to 40 mm.

 

I can take more pictures of the cone for you.  What is it you'd like to see?  Any particular angle?  The appearance changes depending on which way you look at it.

 

As for comparison to the Aura 18 cone, I haven't seen an Aura 18, but it looks like that driver uses a brushed aluminum cone.  The dust caps may be similar, but the carbon fiber looks completely different.



#40 chrapladm

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Posted 14 September 2016 - 10:42 PM

Thanks Nathan for the info. I was referring to simulation. When looking at only that they had similar response shapes. But obviously with 30mm excursion there not going to compare for long when at burst mode. I only have simulations to go by for now so thats why I had asked.

 

SME, I believe the dustcap on the Aura 18 has a point and is an actual cone shape. Normally you would have a round dome shape or inverted shape. So when it was hard to tell from the pictures I was curious if it was like the Aura dustcap and coming to a point.

 

Its not a big deal either way just curious is all.

 

Here in this pic you can see the dust cap shape better:

269-186_HR_0.jpg


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