kipman725

would be cool to at least get the database back online there is a lot of useful info

I was trying to avoid audio connectors so that the wrong cable didn't get plugged in. 

We are building 8 Skrams at the moment with B&C 21SW152.  I notice the suspension is super stiff out the box on these drivers but finding the space to do any kind of free air break in is a challenge while also building the subs.  Does anyone see an issue performing break in with the driver mounted in the subs and the hatch removed?  also failing that I guess break in is actualy not that important and will occour with usage?

The thermal sensors sound interesting I have thought about adding 1 wire temp sensors to the magnets of our speakers but am a bit stuck for low cost gas tight connectors and cabling and also how to attach the sensors to the magnets. 

10 hours ago, Tahoejmfc said:

QSC PL380

Admark amps seem to be getting good reviews and are a step up in power.  We are using Gisen amps for a few years without issues.  

Even in an archived state the site is very useful,  I don't know anywhere else with such subwoofer data.  30$ a month to run a small forum is excessive, there are few active threads like the SKRAM and SKHORN thread, these could be restarted on DIYA?

Perhaps the forum content could be captured somehow and hosted cheaply?

went with the 'B' rack solution of two EXTRON XPA 2004, more than enough power for home use.  This also means my other rack is less restricted on noise so I can replace my Yamaha with high power Gisen amps and shrink that rack size and weright.  The Yamaha also have decent re-sale value so the total cost is low.  

In the UK the psytrance scene is into using Opus  systems which have custom linear amplifiers (that are possibly the most dense objects in the universe), 25mm thick cabs and sometimes exotic drivers like TAD.  Only reflex loading ASFIK.

On 9/20/2022 at 8:55 AM, Mike said:

Hi All, Finally I have all the parts for my for my active versions built. I'm using NSW6021-6 21"  with Loto Dsp amp module from powersoft with either the 3004PFC2 or 4HV amplifier amp modules, I might try both amps options...The DSP has a few limit options available. What's the best value for the NSW6021-6 driver for the following limiters.  

1, TruePower TM

2, RMS Voltage

3, RMS current

4, Peak Limiter

 

Thanks

this document from powersoft has some guidelines (6" coil): https://www.powersoft.com/wp-content/uploads/2019/01/powersoft_TN009_LimiterSetup_en_v1.0.pdf

Limiters are also a function of the box design and to an extent the program material.  They are used to prevent over excursion and thermal damage.  You can check this in Hornresp but I don't think the amplifiers above have enough output voltage with this driver to cause over excursion with an appropriate high pass filter.  Then you are just left with thermal damage for which you want the TruePower limiter.  To set this you start at a low value and measure magnet temperature* over a long period of time while running program material that is heavily compressed by the limiter.  Adjust up the limiter slowly (it may take on the order of an hour for the magnet temp to stabilize) until you reach the maximum magnet temp you want to allow (<100C !).  This procedure takes a long time, makes a lot of noise and may destroy your driver...   

On 9/7/2022 at 7:03 PM, Shayne32 said:

Thanks a bunch for the reply and all your hard work on the project!!!

will post back with my results when complete, probably a few months off yet 

you can try using a limiter with a long time constant (4-10s attack, 8-30s release) set for the output voltage that results in 2/3rd AES power disipated at the boxes minimum impedance or Re of the driver if you can't measure that.  Should be quite hard to kill the drivers due to thermal failiure with that in place.  Many LMS don't support such long time constants though. 

Any experience of the fan noise of the Linea Research amps?

I don't think you can buy an X8 even if you have the money at the moment as the electronics parts shortage hit Powersoft hard and they prioritized install.  Powersoft give the following spec:  fan Noise - 1/8 Maximum Output Power @ 8 Ω (1m) 40 dBA SPL, so if idle could go <35dBA at idle that would be fine I think to use at home.

Another idea would be to use amp modules to make my own amplifier.  It looks like I could fit 8 channels of this:

https://icepoweraudio.com/buy/as-series/2000as2hv/

in 3U (needs space for heatsink on base).  Hypex also sell high power modules:

https://www.hypex.nl/product/nc2k-oem/79

At a lower cost I could also try and find who makes these modules and devise a cooling system for them:

https://www.bluearan.co.uk/index.php?id=JMSQ10M#

looking to reduce the size of my amp rack.  Currently use 3*P7000S and 1*P5000S (Yamaha)  which are silent when not operating at high output.  Ideally looking for 4 channels in 2U that can do 2000W/ch 8ohm but as I also use this rack at home with low fan noise when at low output.  With modern technology this should be quite easy! but it seems like the minimum fan speed on most amps is programed relatively high.  So far I have heard the Labgruppen C series is quite quiet so that's a possibility.  I wonder if anyone else knows of quieter amps? 

The other idea would be to just get a load of 1/2U EXTRON xpa amps and have a low power 'b' rack hidden away at home, replacing my current Yamaha amps with something like Gisen K21x4 which we already have been using two of for a year on a larger system and been impressed with its performance for the price but is quite noisy. 

I suspected that level of pricing, makes it pointless for me as I could get the eminence nsw6021-6 which presents a better load for my amps for that price.  Practically however I will go with the B&C 21ds115-4 when we have the funds because in almost all our use cases its better to have more subs to form arrays than fewer slightly higher output subs.

https://audioxpress.com/news/lavoce-launches-powersoft-ipalmod-compatible-18-and-21-subwoofers

http://www.lavocespeakers.com/lavoce/assets/datasheets/1636475255_LAVOCE_SAN216.00iP_21in_SUBWOOFER_E.a.pdf

Bl^2/RE = 378

Interesting the comments about USB protocol delay been additive to the number you see in the driver, would make using very small buffers quite pointless.  Ethernet should be much better but you might require small frame lengths to achieve the best possible latency.  For live sound I would say around 50mS would be acceptable for FOH but perhaps as low as 10-20mS for any monitoring system.  For FIR filters for speaker correction 512-1024 taps @ 48KHz would seem to be OK for live sound.  I notice the Linea research ASC48 has 768 tap filters @ 96kHz correction filters (~4mS delay).

If you get your DSP software running on ARM you could also potentially use something like Xilinx Zynq to accelerate FIR filters.

I've seen various PC based crossover/DSP software on DIYAudio and had assumed that the delays would be too great for live audio.  What kind of delay do you get SME?

It should be easy to temperature limit sub woofers as the thermal overload is slow usually over hours and the voice coil is aluminum or copper for which we know the thermal coefficient.  The amplifier should be able to use a low frequency excitation of low amplitude (say 5Hz) to sense the voice coil resistance and by comparison with the cold resistance at a known temperature sense the voice coil temperature (using the thermal coefficient).  This way you wouldn't even need to have an impedance plot of the cab.  For high frequency drivers however this wouldn't be suitable and we would have to do some kind of model fitting to extract the Re term from live impedance plots obtained via dual channel FFT analysis. 

It's not going to happen but the ideal platform for this would be if Powersoft just opened up the FPGA or DSP chip that they presumably have inside their amps which must already have ADCs monitoring output voltage and current....

My limiter on the input is a simple compressor not multiband its more like a system volume limit, if I want to restrict the maximum volume I just reduce the threshold.

The outline newton might be able to implement your setup? I haven't used one (out of my price range...): https://www.production-partner.de/test/outline-newton-audio-dsp-prozessor/

12 hours ago, peniku8 said:

Are you sure you meant the 15" drivers?

I meant the 21" oops

The maximum peak SPL spec is essentially meaningless but I can tell you from comparing the SKRAM to FANE 18XB reflex subwoofers in simulation 4 SKRAM with B&C 21DS115-4 will surpass the output 10 40Hz tuned 18XB loaded reflex boxes.  So to surpass the output of your 4 single 18" subs I would expect you to need two SKRAM.

I run peak and 'RMS' (longer time constant) limiters, usually the system is over provisioned and we are controlling output level through the mixing desk though so they are not activating.  I also have a compressor on the input with a long attack and release and medium knee that is adjusted with pink noise to engage when the output limiters are starting to engage such that its impossible to activate the output limiters constantly with music signals (the compressor effectively turns everything down if that happens).  Perhaps its just our priorities with the speakers we bring but I find the most demanding content is live bands on the tweeters where we have observed limiting and once lost a diaphragm.

Its pretty easy to bring the connectors out to patch panels, I use Symetrix 8x8 DSP + DIGIO and wouldn't go back to fixed signal flow.

Symetrix or QSC or BIAMP DSPs do arbitrary signal processing with a flow graph approach.  You can download the software and design site files offline to see if it will work for you.  The Symetrix limiters accept side chain input which could simplify your signal flow.   Powersoft amps can limit on real power input to the driver.

I'm not quite sure why no one has developed an amp that senses real time voice coil temp from the copper/alu thermal coefficient yet but that should be possible (and guarantee driver survival from thermal failure).  A low frequency small amplitude excitation could be used to sense DCR.

https://www.china-sanway.com/D20KQ-4-Channel-Class-D-Digital-DSP-Amplifier-16000W-for-Subwoofer-pd49629476.html

I suspect the latest Sanway amps are at least a development on the original LG designs as the power levels are beyond the amplifiers that they are meant to be a clone of: https://www.prosoundnetwork.com/gear-and-technology/labgruppen-fp-series-amplifiers

Very useful data.  I'm impressed you tested close to 130dB I have tested at ~115dB before and also experienced this tactile HF sensation.  Under 10% HD in the 22.5V test of the AXI2050 on K402 is impressive.  Its a shame the Klipsch charge so much for this horn.  I did consider buying a pair of 2360A until I heard a them in a club in Berlin (more of a listening room).  Initially I the sound was very impressive but after a while I noticed an unreal kind of cupped nature to the midrange which would have annoyed me if I had bought some.

Did some quick tests on the TASCAM US-2X2HR similar the the Fireface at 4V loopback THD+N = -98.5dB