I am intent on the protection for many reasons...
Last Feb we had our annual desert party, it was the first run with the stadiumhorns. I left the soundstage in the hands of someone I trust greatly, anyway he still managed to blow something up.. Luckily it was in the last hours of the party and people weren't even dancing. We switched to our EONs and everything was fine.
More than anything though, I value headroom over driving things to the max all the time. This is a way I can guarantee whoever is using this system will have to respect my montra. Yes, the sound will shut off completely and be a complete buzzkill if they drive it too hard- but they will learn very quickly like a shock collar on a dog. I am totally into that, and this frees me from the shackles of worrying about leaving my system in the hands of other people. It is foolproof
If there is a simple limiter that can run with a 12V supply and has some sort of LED feedback to show when it is limiting, I would definitely like to know about it- I may use that instead. But I couldn't find anything that fit the bill?
Last Feb we had our annual desert party, it was the first run with the stadiumhorns. I left the soundstage in the hands of someone I trust greatly, anyway he still managed to blow something up.. Luckily it was in the last hours of the party and people weren't even dancing. We switched to our EONs and everything was fine.
More than anything though, I value headroom over driving things to the max all the time. This is a way I can guarantee whoever is using this system will have to respect my montra. Yes, the sound will shut off completely and be a complete buzzkill if they drive it too hard- but they will learn very quickly like a shock collar on a dog. I am totally into that, and this frees me from the shackles of worrying about leaving my system in the hands of other people. It is foolproof
If there is a simple limiter that can run with a 12V supply and has some sort of LED feedback to show when it is limiting, I would definitely like to know about it- I may use that instead. But I couldn't find anything that fit the bill?
JG,
Great video! The sound quality was pretty good actually and whatever you used to record apparently has stereo mics. I was listening to it on the bus with headphones and the expletives that came out on the right side made me look up and over to see of the person sitting next to me said it. Anyhow great to see and hear it in action. It looks like an amazing sub.
Regarding your VU meter and Arduino. Awesome that you are also handy with programming micro controllers. If Arduino has an analog output, you can use that to put a 3.3v max (http://www.minidsp.com/forum/hardware-support/9007-re-2x4-master-volume-control-questions) to 0v output into the middle pin of the three pin volume control input of the miniDSP. MiniDSP uses a voltage divider from a pot to feed an analog input pin which then interprets the level and sets the volume allowing for remote volume control. This could be used to clamp down the max excursion should it be sensed by your circuit. You need to enable external volume control in miniDSP software plugin.
You can program your Arduino to perform a buzzkill mode of setting 0% if it detects breach of drive levels to sub, or maybe just do a 25% (-6dB) warning cut. Should work like gangbusters though.
Great video! The sound quality was pretty good actually and whatever you used to record apparently has stereo mics. I was listening to it on the bus with headphones and the expletives that came out on the right side made me look up and over to see of the person sitting next to me said it. Anyhow great to see and hear it in action. It looks like an amazing sub.
Regarding your VU meter and Arduino. Awesome that you are also handy with programming micro controllers. If Arduino has an analog output, you can use that to put a 3.3v max (http://www.minidsp.com/forum/hardware-support/9007-re-2x4-master-volume-control-questions) to 0v output into the middle pin of the three pin volume control input of the miniDSP. MiniDSP uses a voltage divider from a pot to feed an analog input pin which then interprets the level and sets the volume allowing for remote volume control. This could be used to clamp down the max excursion should it be sensed by your circuit. You need to enable external volume control in miniDSP software plugin.
You can program your Arduino to perform a buzzkill mode of setting 0% if it detects breach of drive levels to sub, or maybe just do a 25% (-6dB) warning cut. Should work like gangbusters though.
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Wow xrk- that is a GREAT idea!! I didn't think of interfacing the arduino to the pot volume control on the 2x4. Wow, heck yeah.
Hopefully it can handle a PWM signal from one of the arduino's analog outs, if not I'll have to make a little voltage filter to smooth it out.
Wow, bingo. Great solution! I am for sure doing it that way.
Glad you enjoyed the video as well! Thanks so much
Any ideas what I should do about this synergy top? Getting the TH completed, I am itching to have the highs that match so I can let her rip a little stronger. Right now it is super unbalanced LF/HF, even with the sub at -5dB and EONs at +6dB.
EDIT: yep, tons of people already controlling minidsp volume w/ PWM signals. I'm totally doing this!! Still going to add a VU meter though just for neat factor.
I will need this: http://www.instructables.com/id/Analog-Output-Convert-PWM-to-Voltage/
Hopefully it can handle a PWM signal from one of the arduino's analog outs, if not I'll have to make a little voltage filter to smooth it out.
Wow, bingo. Great solution! I am for sure doing it that way.
Glad you enjoyed the video as well! Thanks so much
Any ideas what I should do about this synergy top? Getting the TH completed, I am itching to have the highs that match so I can let her rip a little stronger. Right now it is super unbalanced LF/HF, even with the sub at -5dB and EONs at +6dB.
EDIT: yep, tons of people already controlling minidsp volume w/ PWM signals. I'm totally doing this!! Still going to add a VU meter though just for neat factor.
I will need this: http://www.instructables.com/id/Analog-Output-Convert-PWM-to-Voltage/
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I was going to say all you need is an RC filter to convert the PWM to analog. Make sure the noise rippling on it is very small or is above the bandwidth of the volume control otherwise you will get PWM noise on your whole signal output. I am working on a sim of the synergy tops now with the 90deg H x 40deg V geometry as suggested by Weltersys. That horn is short so cannot sustain a 100Hz front loaded horn output from the 8FE200's. A narrower (and longer horn) may work. What is the narrowest coverage angle you can live with? Would you be willing to go with a 3 way horn and add a couple of 15 in woofers to the horn to cover 100Hz to 400Hz?
This looks like a great RC filter solution for arduino for pot input to the minidsp: Super simple DAC
As far as the tops, I would really like a 90 degree dispersion because usually our gigs are up close and personal to the dance party. I suppose I could live with 60 or 70, though.
How about a dual cell narrow/long horn? I do happen to have two 8FE200's and two CD's
I dunno if that would work. Also, how long is long? I am trying to keep the exterior depth to 25" so it doesn't stick out of the back end over the sub
Thanks for all of the help and support, you continue to amaze me with that
As far as the tops, I would really like a 90 degree dispersion because usually our gigs are up close and personal to the dance party. I suppose I could live with 60 or 70, though.
How about a dual cell narrow/long horn? I do happen to have two 8FE200's and two CD's
I dunno if that would work. Also, how long is long? I am trying to keep the exterior depth to 25" so it doesn't stick out of the back end over the subThanks for all of the help and support, you continue to amaze me with that
Ok...I'm officially jelly...and very anxious to see how well a 3d printed Synergy comes out.
Now I remember, you are the one who asked if I could make a horn of arbitrarily complex 3d surfaces, what would it look like via 3d printing. You have a diy 3d printer that is huge by 3d printer standards - very cool. An option might be to make it in two halves and cement the two together to get a larger size.
The 25in length constraint will mean that you will need rather large woofers to provide the bass from 90Hz to 400Hz, typical of many synergies. The dual 8FE200's could be used for throat side injection for the 400Hz to 1kHz range, and the CD can handle 1kHz and up. If you can accept a 40 in long (add 6in for CD and misc), you might be able to handle the 100Hz to 1kHz with just the 8FE200's.
These are just some of the physical limitations of a horn...
Here is a picture from Bwaslo's spreadsheet showing a typical synergy so you get an idea of what this may look like. The tiny little holes near the throat would be for the face of the 8GFE200's (I would use equivalent CSA of a 2.75in dia hole for each driver), and the slots towards the middel would be for either the bass reflex ports or for the additional woofers you could add.
Here are some preliminary results of the 90deg H x 40deg V 2-way synergy with dual 8FE200's and a B&C DE250CD (model not verified but gives you an idea of what CD's can do in a horn).
Here are the 8FE200's running with sealed rear chambers:
Here are the 8FE200's with 4in dia x 10in long bass reflex ports, routed to about 75% distance from throat at horn walls, the bass assist helps bring up the levels down to 100Hz, but there just isn't enough of it to compete with the highly sensitive front loaded output of the same driver. I think a couple of 15 in woofers ported to these same locations might give you better efficiency (which at circa 110dB is crazy high):
Alternatively, if you can live with 107dB sensitivity, just EQ cut the front loaded output to be level with the bass reflex output and it will be balanced. That is the cheap and easy, but not ideal, fix. Is 107dB a match for your TH?
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Ah yes! And now I'm remembering that you were the one who told me it would only be useful for waveguides, right?? I didn't forget! I've been saving it!
And yes I was thinking exactly that... Probably bond it together as I fiberglass over it. I could apply the fiberglass on the backside as not to affect the horn surface. Probably a thin coat of epoxy on the front side would make it good enough to sand down to a shine
And yes I was thinking exactly that... Probably bond it together as I fiberglass over it. I could apply the fiberglass on the backside as not to affect the horn surface. Probably a thin coat of epoxy on the front side would make it good enough to sand down to a shine
From Cross Spectrum Labs or from Parts Express?
If it's from PE chances are good the CAL file is garbage. It won't matter for measuring subs but it might matter a whole lot for measuring and tweaking your tops.
Now that the sub is done, a couple of semi OT notes unrelated to acoustic design.
Safety - that sub is big and heavy enough to kill you if you get into a head on collision with another vehicle or even a stationary object at moderate to high speed. Don't count on the seats to hold it back, usually there are just a few small headed bolts grabbing onto thin sheet metal to hold the seats down. It will rip the seats right out without even slowing down much and then it's coming straight at you. Since it needs to be removable you can't really bolt the sub down but maybe you could weld a retainer bar in front of it or something to keep it from flying straight ahead. Don't forget the extra batteries too, those are also small death missiles if not properly restrained.
Maintenance - keeping the drivers clean. I don't off road (much) in my car but I do drive on dirt quite a bit and there's always about 1/4 inch of dust on everything. When the cones face out of the box that isn't much of an issue because you can just wipe the cone off but with the basket exposed all that fine dust can find it's way right inside the motor and up into the gap. All of your pictures show your equipment is very clean so maybe this isn't an issue for you or maybe you just clean a lot, but I wouldn't take an expensive system like that down a dirt road, certainly not off road. My last system cost $300 (kijiji special dual Kicker 12 inch L7 with Planet Audio BB1250.1 amp) and I felt bad exposing THAT system to the road dust in my car.
You have a few options for replacing your tops. My first recommendation (for 8 inch woofer compact category) is the DR200 by BFM, second being the slightly larger DR250.
Those designs are horn loaded and at 106 dB/watt they will keep up if not decimate the stadium horns (saving you precious power in the desert)
If you want to design your own I recommend making a small line array with 6.5 inch pro drivers and a stack of cut down piezos. You can build SLA Pro's or design your own in a similar fashion. 4-6 midrance and 6 tweeters and you should have more than enough output. Plus it will be skinny and tall, if that form factor is a plus.
Disclaimer: I like BFM's stuff, you can always design your own so in that case I would say try experimenting with creating horn loaded tops, may be fun!
Those designs are horn loaded and at 106 dB/watt they will keep up if not decimate the stadium horns (saving you precious power in the desert)
If you want to design your own I recommend making a small line array with 6.5 inch pro drivers and a stack of cut down piezos. You can build SLA Pro's or design your own in a similar fashion. 4-6 midrance and 6 tweeters and you should have more than enough output. Plus it will be skinny and tall, if that form factor is a plus.
Disclaimer: I like BFM's stuff, you can always design your own so in that case I would say try experimenting with creating horn loaded tops, may be fun!
Jennygirl,How about a dual cell narrow/long horn? I do happen to have two 8FE200's and two CD's
Xrk971's 90x40 2x8" BR Synergy simulation shows the level at 100 Hz around -12 dB from the midband, almost the same as DSL's popular SM80. Many EDM DJs seem quite happy with a ratio of one SM80 to 2 (or more) DSL TH118 outdoors.
The SM80 has about 8 dB more midband output than xrk971's 90x40 2x8", but a pair of TH118 (driven at rated power) probably have more than that much more output over your 2x15" TH.
Going with two 45x40 degree Synergy horns would give you the same coverage as the 90x40 but increase the LF horn extension and sensitivity considerably. Also would allow stereo top operation, you could strap the cabinets down for transport and spread them out to party. You could even start with just a single 8" per cabinet, then add the second later, or even expand to 3 or 4 on each cabinet, in which case they probably would exceed the TH level.
Art
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Thanks for all of the nice options folks, and thanks epa for the congrats
Really digging the dual idea, though. Running the tops stereo would be an awesome bonus.
Art do you think that is possible with what I have on hand and fit into a 25" length (50cm actual horn path)?
I'm okay with EQing the 200hz+ down using the minidsp. In the end I'll probably run the sub about 3dB hotter than the top anyway... So I'm looking for roughly 125dB capability
Thanks again for all of the wonderful suggestions. A pair of 10s are not out of the question at all, I would just love to make do with my 8's that I have on hand. Sorry if that makes it a lot more difficult
Really digging the dual idea, though. Running the tops stereo would be an awesome bonus.
Art do you think that is possible with what I have on hand and fit into a 25" length (50cm actual horn path)?
I'm okay with EQing the 200hz+ down using the minidsp. In the end I'll probably run the sub about 3dB hotter than the top anyway... So I'm looking for roughly 125dB capability
Thanks again for all of the wonderful suggestions. A pair of 10s are not out of the question at all, I would just love to make do with my 8's that I have on hand. Sorry if that makes it a lot more difficult
IIRC you only have a pair of 8", you really would want at least a pair in each cabinet.
The depth is no problem, the DSL SH50 (50x50) is only 22.5" finished depth, going to 45x40 won't add much length, and you can truncate the second portion of the horn to save depth. You could also make the second portion of the horn as a separate piece, and add it on with over center clamps, turnbuckles or a ratchet strap when you get to the music destination.
The sketch below of a 3x10" 90x40 with 1.4" HF shows the concept.
Art
