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Ricci's Skram Subwoofer & Files

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7 hours ago, Alexlel said:

Can't make my mind between Othorn or Skram.
At first I was going for 2xOthorn + 2xES18BPH to cover 27.5hz - 110hz, so Othorn playing on one octave (27.5hz - 55hz) and the ES18 on another one (55hz - 110hz).

But then the Skram comes out and offer me the possibility to cover those 2 octaves with only one bin + the possibility to tune it lower for movies.
That means :

- Less amplifiers
- Less cabs so less speakers, cables, storage difficulty etc
- Less phase problems 
- Easier building and less wood required

I would save a lot of money, almost enough to build two others Skrams quickly.

The only thing I'm afraid of is the Skram "kick" power, is it something I should care about ?
I like the ES18 kick but it does it with light Mms drivers, the skram would kick with a 412gr Mms (B&C 21DS115-4).

@jay michael review makes me hesitate even more ahah.

Is the Skram far away of an Othorn + ES18BPH combo ? :)

Sorry Alexlel, I'm hoping my posts will help and not make decisions harder :)

A couple things.  I have pulled the drivers out of my Othorns to go in my second pair of Skrams so I am not doing a proper a/b between the two of them.... so my reflections are based on memory so take that how you will.  Like SME said, perhaps a little eq might be all that's needed to add a little bump to the low freq of the skram.... I can't stress enough how similar they are, I'm talking a 9.7 vs a 10 rating at 30hz.   With the Othorns and my old rcf tops I was adding a substantial eq bump to the rcf's kick range as the Othorns just didn't quite give me the visceral feel that I wanted, the skram's excite me in that range.

I've never heard the es18bph but I strongly considered building them.  I actually also own 6 martin audio b115 bins that I picked up in the spring, I'm almost done reconditioning them.  I will eventually experiment  using those in between the skrams and the danleys.

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2 hours ago, m_ms said:

Interesting impressions - much appreciated. The Skram appears to be one heck of a sub (and the Othorn as well), and I'd also like to have a closer listen to the Danley's. 

Regarding named perceived differences between the Skram and Othorn (grunt vs. growl, if you will), I'm wondering whether the more pronounced rowdy character or "growl" of the Othorn is at least partly explained due the driver being more exposed at the mouth? The way you describe it though doesn't make it sound as if the Othorn is sonically akin to a typical direct radiator (i.e.: if we accept there is any such typicality to the sound of a direct radiator), and moreover I've heard other people speak of the tapped horn sound in ways quite similar to yours (something about a combination of presence, smoothness, a certain visceral feel, and even a touch of "warmth") - impressions I can relate to via my own tapped horns, though it may at first glance sound like any capable, well integrated sub regardless of topology.. 

Interesting also that the Skrams appear to be more impactful (alive?) in the upper end of their range compared to the Othorn and how this is explained (simply caused by a rise in the frequency curve in the upper range?). I've always imagined the Othorns were good to some 125Hz. 

I would say the Othorn sounds considerably different than direct radiators...in a good way!  At least compared to the rcf 18's that I owned previous.  I have seen it written more than a few times from Othorn users that there is a "sound" to them that people really enjoy, and I can completely agree with that.  Perhaps it is due to the driver placement, I cant say for sure. I haven't come across anyone who figured the Othorn was well suited for playback up to 150, I crossed mine around 70 most times and let my tops do most of the kick region.  I would have been entirely happy to keep the othorns to be honest.  The release of the skram plans happened pretty much right when I was gearing up to build another pair of Othorns.  After estimating costs, factoring wood and cnc time in Canadian dollars it cost me roughly 1500 dollars to build 2 othorns and about 1600 dollars to build 4 skrams.  With both cabinets built I am happy with changing directions, I think the skrams fit my needs better and will cost less to build more if the time comes.  I will likely load the othorns again when I have some spare cash, my living room needs a major stereo upgrade :)

 

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I'd put a broad PEQ at 30Hz to bring that up to equal the 70Hz SPL (or bring down the 60Hz alternatively). The 85Hz notch might need some experimentation, it may or may not be good trying to even that out. It is so narrow so you might not even notice a difference. I found that positive EQ'ing with a very high Q often doesn't provide any desirable changes.

When EQ'ing out phase problems I encountered a very wierd pumping phenomenon once. When playing back a sine wave, the level would sway, as if it was controlled by some kind of LFO.

You can't recover the 150Hz dip as that it caused by internal phase cancellations. More energy also means more cancellation so you end up without any improvements.

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22 hours ago, medico said:

Very interested in this design, going to build one just to have a listen. and if i like what i hear i'll build 8+ of them for our rig!

 

one thing, our tops are bit wider than these, so would want to build them 2inch or so wider, and possibly taller, by few inches.

will this effect the sound in anyway? and how so?

 

also whats the best way to do so? scale everything up?

 

look forwards to hearing back!

Cheers, 

Murdoch

Adding 2" of width shouldn't affect things much but I'd not add the height. Can you not lay the subs on their side so they are 36" wide? If you are using more than 4 or more subs you should be able to stack them or arrange side by side for plenty of width.

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4 hours ago, jay michael said:

Yeah I suspect that its entirely possible that some eq tuning could change the character of the sound from the skram. The only eq applied so far is the recommended dsp settings that Danley provide for the sh46's.  I didn't experiment with higher crossover points above 80 hz, its something that I want to do the next time I have them out.  I will have the full system outdoors for 4-5 days aug 15 weekend so I will get lots of time to experiment some more.  Here is the response of just the skram as I had it processed meeting the sh46

https://imgur.com/mTse4If

If one was to try applying some individual eq just to the sub to improve it, what should I strive for?  More of a flat response? what about the notch's at 85 and 150 ish? Should I try to even those out?

Here is the response of both speakers together

https://imgur.com/gallery/EMtk6eN

Certainly open to suggestions if anybody has some!

 

 

The 85Hz notch is fairly narrow and shallow. it wasn't in the raw measurements so it's likely some sort of artifact or perhaps an unintended EQ band. The port resonance cancellation at 160Hz cannot be filled in. Don't worry about that. If anything you may find that adding a band of EQ to knock that peak at 200Hz down may improve it a bit. The low pass is already pushing it way down in level but it may be worth a shot to knock it back another 10+dB. You may hear a difference or you may not.

Response through the bass and mid bass region with the Danley's looks fairly smooth. For music and especially live sound or club work I'd run the bass quite a bit hotter. The crowd always loves the bass. Start with the JBL/Harmon curves and season to taste.

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I really need to get a pair of these going. I'm ashamed I haven't even tested or listened to these yet!

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5 hours ago, jay michael said:

Yeah I suspect that its entirely possible that some eq tuning could change the character of the sound from the skram. The only eq applied so far is the recommended dsp settings that Danley provide for the sh46's.  I didn't experiment with higher crossover points above 80 hz, its something that I want to do the next time I have them out.  I will have the full system outdoors for 4-5 days aug 15 weekend so I will get lots of time to experiment some more.  Here is the response of just the skram as I had it processed meeting the sh46

https://imgur.com/mTse4If

If one was to try applying some individual eq just to the sub to improve it, what should I strive for?  More of a flat response? what about the notch's at 85 and 150 ish? Should I try to even those out?

Here is the response of both speakers together

https://imgur.com/gallery/EMtk6eN

Certainly open to suggestions if anybody has some!

Smooth response is more important than flat response.  In fact, you may prefer a response with a substantial rise toward the bottom.  Also, I believe broad scale features are actually a lot more important than features at narrower scales.

As @Ricci recommends, I would not try to "fix" the notch from the port resonance at 150 Hz.  I'm not sure about notch at 85 Hz, but I don't see it in your earlier measurements.  This suggests to me that it could be caused by interference from one or more reflections.  If that is the case, then you should leave that notch alone also.  The key thing is that you want to EQ actual problems with the sub and not features caused by acoustic interference.  Easier said than done.

While Hornresp simulations are not perfectly accurate, I went ahead and used the Filter Wizard in Hornresp to look for a good PEQ that might help smooth the response.  The PEQ I came up with is:

   Frequency 93 Hz; Q 2.1; gain -2.2 dB

The result simulates quite flat, albeit with a very slight bump in the low 70s Hz.  Without knowing how the subs behave in real life, I'd suggest applying the PEQ while listening to music, and varying the gain until it sounds "balanced".  A balanced sound will exhibit the positive characteristics of all these frequencies simultaneously, without letting any one frequency area get in the way of the others.

Keep in mind that you'll probably need to turn the subs up a bit more after doing this PEQ to keep them matched with the mains, and you'll want to do this before critically evaluating any adjustments.  And yes, do critically listen to the results with your ears and body.  Measurements are very helpful to understand what's going on, but i see too many people listen with their eyes, obsessing over how pretty their measurements under the misplaced conviction that the measurements are the absolute truth.  (For a number of reasons, it's way more complicated than that.)

3 hours ago, peniku8 said:

I'd put a broad PEQ at 30Hz to bring that up to equal the 70Hz SPL (or bring down the 60Hz alternatively). The 85Hz notch might need some experimentation, it may or may not be good trying to even that out. It is so narrow so you might not even notice a difference. I found that positive EQ'ing with a very high Q often doesn't provide any desirable changes.

When EQ'ing out phase problems I encountered a very wierd pumping phenomenon once. When playing back a sine wave, the level would sway, as if it was controlled by some kind of LFO.

You can't recover the 150Hz dip as that it caused by internal phase cancellations. More energy also means more cancellation so you end up without any improvements.

I would not recommend PEQ boost of any kind at 30 Hz.  The vent tune will already be contributing to ringing there, and any boost, no matter the bandwidth, will likely accentuate that ringing.  If instead of cutting from the top, one wishes to boost the bottom, I'd suggest trying a low-shelf filter if that's available.  A low-shelf centered around 75 Hz  (looking again at the sims) could be helpful.  However, I think the PEQ I suggested above may be a better place to start.

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1 hour ago, Ricci said:

The 85Hz notch is fairly narrow and shallow. it wasn't in the raw measurements so it's likely some sort of artifact or perhaps an unintended EQ band. The port resonance cancellation at 160Hz cannot be filled in. Don't worry about that. If anything you may find that adding a band of EQ to knock that peak at 200Hz down may improve it a bit. The low pass is already pushing it way down in level but it may be worth a shot to knock it back another 10+dB. You may hear a difference or you may not.

Response through the bass and mid bass region with the Danley's looks fairly smooth. For music and especially live sound or club work I'd run the bass quite a bit hotter. The crowd always loves the bass. Start with the JBL/Harmon curves and season to taste.

Ok thanks for the suggestions. Next time I have it up and running ill tame that peak at 200 a bit.  I had the subs pretty close to my fence this time so perhaps that's what was happening around 85.  Agreed fully on increasing the sub output.  I kept it flat-ish to not completely drive my neighborhood nuts.  In your opinion which is the better way to do this?  Reading the manual for my venu360 dbx seems to suggest I should turn down the attenuators  on my amp powering the Danleys until the desired top vs sub balance is achieved.  I have read from other sources to just boost eq for the range controlling the subs.

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28 minutes ago, SME said:

Smooth response is more important than flat response.  In fact, you may prefer a response with a substantial rise toward the bottom.  Also, I believe broad scale features are actually a lot more important than features at narrower scales.

As @Ricci recommends, I would not try to "fix" the notch from the port resonance at 150 Hz.  I'm not sure about notch at 85 Hz, but I don't see it in your earlier measurements.  This suggests to me that it could be caused by interference from one or more reflections.  If that is the case, then you should leave that notch alone also.  The key thing is that you want to EQ actual problems with the sub and not features caused by acoustic interference.  Easier said than done.

While Hornresp simulations are not perfectly accurate, I went ahead and used the Filter Wizard in Hornresp to look for a good PEQ that might help smooth the response.  The PEQ I came up with is:

   Frequency 93 Hz; Q 2.1; gain -2.2 dB

The result simulates quite flat, albeit with a very slight bump in the low 70s Hz.  Without knowing how the subs behave in real life, I'd suggest applying the PEQ while listening to music, and varying the gain until it sounds "balanced".  A balanced sound will exhibit the positive characteristics of all these frequencies simultaneously, without letting any one frequency area get in the way of the others.

Keep in mind that you'll probably need to turn the subs up a bit more after doing this PEQ to keep them matched with the mains, and you'll want to do this before critically evaluating any adjustments.  And yes, do critically listen to the results with your ears and body.  Measurements are very helpful to understand what's going on, but i see too many people listen with their eyes, obsessing over how pretty their measurements under the misplaced conviction that the measurements are the absolute truth.  (For a number of reasons, it's way more complicated than that.)

I would not recommend PEQ boost of any kind at 30 Hz.  The vent tune will already be contributing to ringing there, and any boost, no matter the bandwidth, will likely accentuate that ringing.  If instead of cutting from the top, one wishes to boost the bottom, I'd suggest trying a low-shelf filter if that's available.  A low-shelf centered around 75 Hz  (looking again at the sims) could be helpful.  However, I think the PEQ I suggested above may be a better place to start.

SME, thanks for the thoughtful information here. I should have some free time next week before we head off to our site to start production.  Ill give your peq suggestion a try and let you know how it goes.  When you say I may prefer having a substantial rise towards the bottom I am not sure if I gather what you mean?  Are you suggesting a peak near 30 that falls the higher the frequency goes?

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1 hour ago, SME said:

I would not recommend PEQ boost of any kind at 30 Hz.  The vent tune will already be contributing to ringing there, and any boost, no matter the bandwidth, will likely accentuate that ringing.  If instead of cutting from the top, one wishes to boost the bottom, I'd suggest trying a low-shelf filter if that's available.  A low-shelf centered around 75 Hz  (looking again at the sims) could be helpful.  However, I think the PEQ I suggested above may be a better place to start.

That would've been something around

F30 +2db Q0.6

I doubt that you'd notice much ringing with a filter like that, but you're correct of course. Also, I think modern processing equipment should be accurate enough to reduce rining to a minimum. There are mixing consoles that have up to like 48bit 192khz processing. Mixing desks are not loudspeaker management systems, but I'm sure these are also up to modern standards.

1 hour ago, jay michael said:

Ok thanks for the suggestions. Next time I have it up and running ill tame that peak at 200 a bit.  I had the subs pretty close to my fence this time so perhaps that's what was happening around 85.  Agreed fully on increasing the sub output.  I kept it flat-ish to not completely drive my neighborhood nuts.  In your opinion which is the better way to do this?  Reading the manual for my venu360 dbx seems to suggest I should turn down the attenuators  on my amp powering the Danleys until the desired top vs sub balance is achieved.  I have read from other sources to just boost eq for the range controlling the subs.

I'd prefer having the subs and tops at the same volume at the crossover frequency (you can easily measure that by sending them a sine wave at that frequency and measuring the SPL of the speakers individually), then applying an EQ to shape the response of the entire system. You can experiment with different low shelves. On my home system I have the sub some 9-10db hot and have a low shelf of +6db 30Hz Q0.7 on top of that. PA systems often start rising up to like 10db from 1khz down to 100hz and some more in the sub region. At least that's what I've seen in an l.acoustics paper.

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Just now, jay michael said:

SME, thanks for the thoughtful information here. I should have some free time next week before we head off to our site to start production.  Ill give your peq suggestion a try and let you know how it goes.  When you say I may prefer having a substantial rise towards the bottom I am not sure if I gather what you mean?  Are you suggesting a peak near 30 that falls the higher the frequency goes?

A peak at 30 Hz, yes, but not like a bell-shaped PEQ peak.  Rather, I'm thinking of a smooth ramp for the combined response, like a straight line with a slope of maybe around -3 dB/octave from the bottom up to 250-500 Hz or so.  When using the subs indoors near boundaries, you may see that kind of shape arise naturally in measurements, albeit with a lot of messy finer details due to the effects of interfering reflections, room resonances, etc.

As far as how to do this with EQ, I guess it depends on what's available.  Multiple shelf filters, spread out across the frequency range, may be a better choice than PEQ filters.  Even better might be to use an FIR-based solution to nail down the desired shape precisely but I don't know that these are commercially available for bass usage.  Unfortunately PEQs and shelf filters both contribute new resonances to the sound, to the extent that they don't perfectly cancel out existing problems in the response shape.  Used skillfully, these filters can be an effective medicine, but they come with a bitter aftertaste.

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53 minutes ago, peniku8 said:

That would've been something around

F30 +2db Q0.6

I doubt that you'd notice much ringing with a filter like that, but you're correct of course. Also, I think modern processing equipment should be accurate enough to reduce rining to a minimum. There are mixing consoles that have up to like 48bit 192khz processing. Mixing desks are not loudspeaker management systems, but I'm sure these are also up to modern standards.

The ringing is already there, as a consequence of the HPFs (both electronic and acoustic) at/near the vent resonance.  It can't be avoided because it's a fundamental property of the cabinet alignment.  One would have to EQ it to not roll-off at its lower limit, which obviously doesn't work in practice.

If the PEQ you suggest does not precisely cancel a comparable existing dip there, it will also contribute its own resonance.  At Q 0.6, this is likely to substantially affect transient sounds, in addition to directing listener perception disproportionately toward the ringing that's already there.

While many DSP systems have problems with filters at very low frequencies, I'm not discussing that here.  The ringing I speak of arises from the final response shape, not necessarily the processing that was applied to get it to that shape.

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14 hours ago, jay michael said:

Sorry Alexlel, I'm hoping my posts will help and not make decisions harder :)

I've never heard the es18bph but I strongly considered building them.  I actually also own 6 martin audio b115 bins that I picked up in the spring, I'm almost done reconditioning them.  I will eventually experiment  using those in between the skrams and the danleys.

Of course those help !
It's just quite hard to believe that this cab can do the job of a sub and a kickbin ! And that it possibly do it even better.
I really want it to be real ahah, I'm in holidays in 2 weeks, so I have 2 weeks to make my decision between Othorn + ES18BPH or the Skram !

I like the ES18BPH sound, may not be everyone taste btw.

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On 7/31/2019 at 3:12 AM, jay michael said:

Of note.  The skram's have a powerful 30hz grunt to them, very clean and hifi sounding..... but I think the Othorn sounds slightly more exciting with those really low frequencies.   The Othorn has some sort of a unique harmonic growl to its 30hz output that is just really sexy.  The Skram's are seriously almost there... they are just ever so slightly perhaps a little cleaner so it doesn't sound quite as rowdy as the Othorn does down low.  On the other hand the skram up higher is noticeably more impactful and punchy which for most types of music I think is going to serve you better.    If you are strictly a bass music lover the Othorn is a pretty amazing beast,  If your musical tastes are wider I think the Skram is the way to go. 

Someone previously mentioned adding kick bins to their system.... you were me a year ago, that's what I figured I needed for the sound I was chasing.  I would try the skram first with a nice beefy top cabinet, you may likely agree that kick bins are not needed, the skram's kick plenty.   If your stuck on the kickbin idea then maybe the Othorn might be your ticket. 

 

Ah Jay your making it trickier for me aswell aha, both our kicks and subs can be used down to 40hz, so low end grunt is what we are after.  both seem great options, hard to argue with price point of skram but then again othorns will still be cheaper than pro audio stuff, and as good if not better. at least i am no rush to decide. 

14 hours ago, Ricci said:

Adding 2" of width shouldn't affect things much but I'd not add the height. Can you not lay the subs on their side so they are 36" wide? If you are using more than 4 or more subs you should be able to stack them or arrange side by side for plenty of width.

okay cheers.

yeah we would likely stack on sides anyway, its just nice to have have an option to stack one sub and one top for smaller gigs (without over hang), i mean theyd be fine, itd just do my ocd in.

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Sooo I created a thread in "bass gear" about the loss of a big voicecoil sitting in a skram and how to prevent this from happening again.

It was the second time I used my skram and I was using a NX6000 amp. 

I'm posting this here as well to give a little bit of a heads up on how these things can happen even with moderately powerful amps and how to avoid them. 

Please learn from my mistake and treat your skram's nicely :)

http://data-bass.ipbhost.com/topic/771-burnt-a-costly-drivers-coil-with-a-pricey-ampfollowup-and-prevention-of-costly-mistakes/

 

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In case there was any doubt yes a lowly Behringer NX amp is capable of smoking a 21DS115 or most any other driver with the right/wrong? :unsure: circumstances. 

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22 hours ago, SME said:

The ringing is already there, as a consequence of the HPFs (both electronic and acoustic) at/near the vent resonance.  It can't be avoided because it's a fundamental property of the cabinet alignment.  One would have to EQ it to not roll-off at its lower limit, which obviously doesn't work in practice.

If the PEQ you suggest does not precisely cancel a comparable existing dip there, it will also contribute its own resonance.  At Q 0.6, this is likely to substantially affect transient sounds, in addition to directing listener perception disproportionately toward the ringing that's already there.

While many DSP systems have problems with filters at very low frequencies, I'm not discussing that here.  The ringing I speak of arises from the final response shape, not necessarily the processing that was applied to get it to that shape.

I wonder how it would affect rining if one EQ'd the sub flat to say 5Hz and recreated the sub's rolloff in a dsp. Probably not in a good way.

I only noticed ringing while using a heavy linear phase EQ on a snare drum (pre-ringing that was) once and never had any issues with it again, but I'll pay more attention to the phenomenon in the future and see if I can get a clearer picture for myself. Ringing is a very interesting topic which I only once read about. Did so when trying to figure out how to deal with phase issues when EQ'ing and most of the info I gathered was 'was really bad in the analog world, but is not an issue anymore with digital EQs).

Guess I could do some tests to visualize how something like a FabFilter pro Q-3 handles ringing.

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It's in the first post. 

The DXF for this will not attach here. 

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5 hours ago, Alexlel said:

Wood and B&C 21DS115-4 on their way !

2 Skrams should be up in France before the end of the month :)

Excellent. I look forward to hearing your thoughts on it. 

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On 7/31/2019 at 3:35 PM, Ricci said:

I really need to get a pair of these going. I'm ashamed I haven't even tested or listened to these yet!

Dont worry, Ive had my wood cut for 2 weeks and still havent started building mine yet! Lol

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Ok... report after 3 full days of Skram use.  Josh, thank you for this amazing design! I am simply blown away that this kind of performance can be had through diy designs, you are doing the music world a huge service with your knowledge and plans! 

I do feel I need to apologize if I created any doubt in my previous posts about the low frequency output of these things.... a stack of 4 center clustered with all the mouths centered to each other create just a crazy amount of output, they blur your vision and make your voice change haha!   After the feedback from earlier discussions I added some parametric eq to flatten the the raw response (thanks SME) and they really seemed to respond well to that. They still retained the incredible kick and midbass impact while also having literal giggle inducing deep gobs of sub bass output.  They are just so incredibly clean and powerful no matter what you put into them, just stunning really. 

Following some recommendations in another thread I had my limiters set as per the recommendations for 45 volts / 500 watts during bass music acts and lowered it to about 35 volts or 300 watts during our techno and psytrance acts.   I never needed to run them up to these limits, they provided tons of output to easily keep up with my sh-46's.  The combination of the skrams and danleys is just amazing, I couldn't be happier.  

I didn't take any videos myself as I was running my ass off all weekend, but a friend shared this iphone video with me.  Ben Rama from Techgnosis records playing some super minimal atmospheric tech trance.  If you listen with headphones you can get a sense of how powerful and clean the dynamics of the skrams are.  Kick drums and bass feel immense,  and clean clean clean.  Video taken at about 150 feet from our visuals booth. 

And a pic of the set up https://i.imgur.com/IGh2BDp.jpg

 

 

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