jay michael

Calgary Alberta Canada 

7 hours ago, SME said:

I bought my UMIK-1 several years ago, directly from Cross Spectrum Labs.  The cal file did not contain an absolute SPL reference.  I had to calibrate the absolute SPL using the procedure described above.  Your situation may be different.

This calibration doesn't affect the shape of the curves, only the absolute number.  There's no need to remeasure as long as you can figure out what the SPL difference before and after calibration is.  You can add or subtract dB to a curve in REW on the "all SPL" tab.  Under controls, look at "Measurement Offsets".  Enter the number of dB to add and click "add offset to data" to apply the change.  Don't forget to save.

The SH-46s ought to be very good as tops.  My only concern would be that they are a bit narrow in coverage at "40 x 60 degrees".  Maybe that's typical for PA, and if they can be turned onto their sides to get 60 degrees in the horizontal, that'd be helpful.  A dance floor is not necessarily "long and skinny" like a concert venue.  Though larger events can be like that.  A lot depends on the details of the setup.

I once went to a multi-day outdoor festival with a huge system in the absolute middle of nowhere (rural Zambia to be precise).  A huge array was flown like 15-20m up (rough guesses on dimensions) on temporary scaffolding.  I think it took a sizable crew a week to build it, even with help from a crane.  The whole dance floor was something like 200m deep x 100m wide.  The camping areas were probably 0.5 km behind the stage, and the bass still thumped clearly in our tents all day and all night.

Ok thanks for that, Ill try doing the calibration tonight.  Yeah the 46's have a pretty tight pattern, i plan for the time being to run them in landscape config to utilize the 60 deg coverage angle.  To realize my goal of a highly power dense system in the least amount of cabinets and size,  the 46 seemed to be one of best options I could find.  As they are designed to array with more 46's it keeps the door open to expansion down the road.  For the time being I am planning to add a second pair of smaller synergy horns to act as fills when I need the extra coverage and to use when I don't need the power of the 46's. Working on a deal now for a pair of sm60f's.   I think the 4 subs and 4 synergy horns should give me decent flexibility for both our studio space and our festival stage.  Outdoors we deploy in a large geodesic dome, to expand on size this year we are moving the sound and booth tech outside of the dome under an inflatable stage cover that will basically nest up to the arc of the outside of the dome. The dome will cover the dance floor, using shade sails instead of the full cover to provide shade for the daytime.

https://jaymichaelt.imgur.com/all/

https://imgur.com/a/67pWeUh

Another point is everything needs to fit inside a 8 foot by 12 foot enclosed trailer, sound system, dome, scaffolding camping gear etc.  We could barely make it work before, the new system is considerably smaller and approx 400 pounds lighter. 

I did not calibrate my mic with a db meter. Looking at the REW website they mention this.

Calibrating the SPL Reading

Calibrating the SPL reading gives REW an absolute SPL reference by entering a reading from your SPL meter while a speaker or subwoofer calibration signal is playing. Alternatively an SPL calibrator may be used. This step is not required if you are using a USB mic with a cal file that contains a sensitivity figure.

If I am reading this correctly my mic should already be calibrated?? I am using the minidsp umik1 which came with a calibration file. 

Thanks for explaining the calculations, its what makes this place really special,  I have been learning a ton!    If I do need to calibrate the spl, ill try and get that done and remeasure asap.  Regardless,  I can say that I have a huge freaking smile on my face now!  That was a tremendous amount of work getting those 4 cabs completed on my own and now I am feeling the rewards   You guys rock!   

Fedex is showing my SH-46's arriving tomorrow, its like Christmas over here!  Can't wait to get some music through the new rig, should be a potent little system.  

Thanks for the explanation, I don't understand most of it but super appreciate the people who do!  Thanks a ton for putting another great design out into the public for people to build!  I do have a question, if my measurement was taken at 1 volt @ 1 meter, what is the assumed power shown in the predictions?

5 hours ago, SME said:

I think proximity of measurement to the port would affect the balance between upper and lower frequencies, not the low frequency corner.  It looks like the rear wall may be effectively lengthening the port more than anticipated.  The tuning looks to be around 26 or 27 Hz maybe?  I'm curious what the simulation looks like.  How much extra length do you add to the port in the sim to account for the rear wall?

If you take a look at my newest measurement it doesn't seem to show as low of a tune as my earlier measurements.   I am still pretty new to measurements so hard to say if I am getting the best data, but I did try to follow your guy's recommendations on the second measurements

6 hours ago, Alexlel said:

Hello !

@jay michael Your last measurements has been done with 1 cab ?

@Ricci How close is it to the simulation (21SW152-4) ?

I expect to build 2 Othorns next month but the Skram looks like a real contender, what sensitivity should I expect for 1 Skram, 21DS115-4 loaded ?
My aim is to get the highest output between 25hz and 70hz , can't make up my mind between Othorn or Skram...

Yes this is with 1 cab.  I've built both. The Othorn is amazing, its got a low growl to it like nothing else I have heard before.  That said, the skram more or less equals the low performance of the Othorn and to my ears sounds just as clean doing it.  The skram is substantially easier to build, is also smaller and lighter.   Factoring in cnc time, I built 4 skrams for just a little bit more money than what it cost to build 2 othorns. 

Yup, rookie mistake!  I had my prolite 7.5 amp set with the sub crossover setting engaged on the back! Sorry guys.   I have run the test over again using my k10, mic measured at 1 meter from the mouth and 2 inches off the ground with a voltage of 1 volt measured at the speaker terminals.   It still has the notch that starts at about 149hz.... but it doesn't roll off drastically after 100 hz like it did on the previous measurement. I was in a hurry and forgot to check what my amp gain settings were, ill take a look tomorrow.  Anyways, here are pictures of the measured 1 volt at the terminals and the new freq response.  

https://imgur.com/kWPYnU3

https://imgur.com/GK5D7zt

I didn’t, And probably won’t. The tuning is low enough for my my needs, wouldn’t make sense to me to trade efficiency for a lower tune 

1 hour ago, chrapladm said:

Ok so I am sure someone knows by now how may sheets of 18mm do I need for a pair of Skrams?

 

I am going to start building my pair very slowly. I am going to be out of town a lot for work over the next coming weeks but would like to get started on building these. I have had my pair of SW152's for quite some time sitting on a shelf. Got a lot of other issues going on to make my,  already extremely slow, progress on builds even slower but this build will definitely get my spirits up.(Life has been rough for a few years now)  Hopefully will finish them in 2 months or less. Will also be looking at designing or build an existing design for my single 15HST. 

I made a post earlier on page 3 with cut sheet plans. A pair will take 6 sheets of 5x5 18mm and 1 sheet of 5x5 12mm.

I did do some more frequency sweeps today, testing some new cables I made up with my k10.  One thing that really surprised me is the directionality of these things. I didn’t use a db meter to measure but these things have a substaintial reduction in energy behind them, which I’m pretty excited about. My rcf’s were basically as loud behind and they were in front.  Going to be handy on our festival site as we have had some noise issues in the past with a neighboring property.  

20 minutes ago, SME said:

Does your multimeter have "True RMS" capability or something similar?  The best test signal may be a 50-60 Hz sine wave as that's likely what the meter handles best.  Play it at the same level that you use for a sine sweep measurement and measure the voltage.  You might want to do this while the amp is connected to a load, as I've heard rumors that even some solid state amps don't like running disconnected.  Most are probably fine though.

Whatever voltage you read, you can either adjust the test signal level until you get to 1.0 V (if measuring at 1 meter) or adjust the data afterwards based on the actual voltage and distance used.  Assuming the measurements are accurate, this tells us how the sub(s) respond in an absolute sense.  If you also know the max voltage your amplifier can output, then you have an optimistic estimate of max output using that amp.  The estimate is very optimistic though because the driver and/or other aspects of the system may overload or sound bad before you max out the amp.  The amp itself may not be able to maintain the max voltage if the current/power demand is too high.  Still the information is very useful to be able to understand the performance and capability.

Edit: I have cable with SpeakOn on one end and bare wires on the other.  I also have a paralleling SpeakOns Y-adapter.  This let's me measure voltage even when connected to a sub.

Ah cool thanks that’s super helpful. I’m using a powersoft k10. I’ve got some spare Speakon connectors so I’ll prob just make a test cable like you did. I’ll gave to take a look at my meter, it should have something similar, it’s a professional grade automotive multimeter. I’ll try to get another measurement soon. 

15 minutes ago, SME said:

Impedance can be measured using REW using a custom electrical jig, but I believe that can be a pain to get to work well.  I use a "Woofer Tester 2" to measure impedance.  There may be other methods or products, but I don't know enough about them to recommend any of them.

It's hard to say for sure without seeing impedance measurements, but the frequency response measurements suggest the tune came in a bit lower than 30 Hz.  I also expected to see more output above ~60 Hz, but maybe that has to do with the SW152 vs. DS115?  Or maybe it has to do with measuring at 1 meter instead of farther away.  I'm curious as to @Ricci 's thoughts on these things.

Anyway, those looks like amazing cabs, and tuning a tad lower than 30 Hz is probably not bad for psy-trance which can sometimes have a lot going on at 30 Hz and below.  By chance, do you have a multimeter to use to measure AC voltage?  If you can measure the voltage from the amp, then your measurements will be more meaningful in an absolute sense.  For your cabs using one 4 ohm (nominal) driver each, a good "standard" voltage to measure with is 2 V @ 2 meter or 1 V at 1 meter.

Hey man, I’ll have to do some research on the impedance thing. I did play with the mic distance a bit, and it seemed the response was flatter the closer I was to the mouth. With the mic further away from the mount the response had more of a rising profile to it.  I stuck with 1 meter as that was what josh mentioned in his testing article, but I could easily redo it if he suggests otherwise when he gets a chance to chime in.

i do have a quality multimeter. Are you suggesting running pink or white noise through the amp and literally measuring across pos and neg at the Speakon?  

11 minutes ago, radulescu_paul_mircea said:

Try and limit your graph axis to 10-300 Hz and 45-115 dB. It will show us better details. 

Do you have a way of measuring the Impedance?

Maybe create a Google drive folder to share the measurement data from REW. When you save the data, you can find it in your computer and you can upload it to a shareable folder in your account

Ill look into that Paul.  Here is the graph with the axis like you suggested. https://imgur.com/sn1F5We

How can I measure impedance? Can it be done in REW?

I saved my session in REW,  so if there are any other shots of my measurements you would like to see just ask and ill upload them.

Finally a couple build pics of the finished product.

https://imgur.com/4n7h9Un

https://imgur.com/8cYT8Um

26 minutes ago, Revolt Sound said:

Looks very close to my SK horn measurement. I would be very interested to see the same measurement with all 4 cabs. One with the ports in the center and one with the ports on the outsides.

Sorry having trouble with picture uploads, seems I've used up my allowable data.  Here is a link to a picture showing phase with all 4 subs, still measured at 1 meter away ground plane with the mic in the middle of the 4 subs https://imgur.com/rtHJQ1n

Played around a bit with some frequency sweeps at high volumes, the boxes sound really solid, no rattles or vibrations from the caster wheels. They sound clean and powerful, cant say I think the low end sounds any better or worse than the othorns and the measurements seem to show that they are clean much higher.  All 4 playing together are damn loud, I don't hear any real reduction in volume intensity until they drop below 27hz or so, but still have pretty solid output down to the low 20's before they really start to fall off.  I've sold off my old rcf tops but my danley sh46's are supposed to be here monday or tuesday, ill get them playing together shortly after that and give you guys some impressions with some music played through them.

test area

5 measurements averaged

Distortion

SPL and Phase

Ok, 4 Skrams complete.  Did some measurements today using REW and a minidsp umik 1.  These are loaded with 21sw152 4ohm drivers.  I'm still pretty noob to REW so my testing may not be up standards.  If there is something else you would like to see measured, or measured in a different way please let me know, wont take me long to set it up again.  Measurements were taken in my back yard which is quite large, but there are fences surrounding my back yard.  I placed the mic 1 meter from the mouth with the measurement tip about 2 inches off the ground. I ran the tone generator with pink noise and set the output of the sub to about 90 db.  In the measurement page I tested the output gain and slightly adjusted it louder until REW told me the gain was ok.

Picture 1 shows the settings I have set in the measurement panel. 

Picture 2 shows a single freq sweep measurement all spl raw no smoothing.

What do you guys think the effect would be to run left right stacks in this configuration? Just considering my options for deployment. Putting my sh46’s on top of 2 subs stacked like this would get it them high enough without having to drag out scaffolding.  With the mouths off the ground would the subs not couple to the ground plane as effectively as if the mounts were on the ground?

So close.  Loading drivers and doing the wiring today