kipman725

So I wouldn't go as extreme in some ways as that pdf suggests, the bass boosts are way too much and will make a system sound like mud if you actually follow an equal loudness contour. However the tip "110 - 120dB 2.6kHz -5dB BW= 0.34 Q= 4.233" is totally spot on if your playing dance music and system sounds a bit harsh. My procedure for dance music is: 1) system has existing PEQs that make it flat on axis 2pi 2) play pink noise and adjust aiming of speakers to maximize stereo image area (you could get a distinctive whooshing noise in this area) 3) perform spacial averaged measurements in room 4) fit system response to overall room trend (usually about -10dB at 20 kHz) using PEQs 5) start playing tracks and tweaking, normally all that's required is the above and a some bass boost depending on the room perhaps a PEQ at around 50Hz to apply a small amount of boost 6) configure input compressor with 10:1 ratio and slow attack and release times with pink noise at the point the limiters are starting to be occasionally triggered.

the 93Hz (actually 91Hz sorry) is a bit of an in joke, hit someone with 120 dB of 500 Hz and you still get TR: https://forum.speakerplans.com/uploads/8883/Void_System_Tips_EQ.pdf my sub section is 4*15" reflex (soon hopefully 6*15") and my tops (in total) are 2*15" reflex (with a way smaller amp) so it makes sense to keep the crossover high. Another type of user who keeps the crossover high is someone using fully horn loaded tops as usually the horns are too small to have good efficiency at a low sub crossover point.

I use a 120Hz crossover to my subs in my PA system LR4 slopes, I match the sensitivity of the subs and the tops so this is also the acoustic crossover frequency. My tops do play down to 80Hz but I want to keep the thermal load off them and reduce the chance of clipping their smaller amp. A lot of PA's (essentially everyone I know personaly who isn't running a large touring sound company) will use an 80Hz electrical crossover but then tune the sub amp sensitivity by just turning it up until it sounds right. This adds an effective bass boost and puts the acoustic crossover typically around 150 Hz. Another reason I like to cross at 120Hz is I actually want a mono source for 93Hz which is the frequency that rattles the chest, subs can be arranged for best coverage but top locations are more fixed for stereo image . The kick drum in Bicep - Glue is at 53Hz If your interested in tests that might be applicable for higher frequency speakers I find knowing the residual noise with no signal interesting as some amps hiss too much to be used on compression drivers in quiet environments.

The leads can be preformed but this is an additional manufacturing step so would add cost. In this image of a real LG amp I found they are also soldered on top but the pads are more surface mount style. This image is actually quite surprising to me as lots of the components look very 'retro' (blue axial leaded capacitors!).

thats odd, it looks like the leads are meant to be bent through the holes but have been cut too short. Also where is Q50?

Have you checked the relay is open when the amps switched off? the contacts may be welded shut Also what amps do you have to test?

Two minutes of full output it too long in my opinion, sure the amp should survive but it doesn't reflect real world operating conditions and as such the 'thermal reserve' (to use the MA5002VZ terminology) is typically insufficent. When testing the Crown CTS4200 which is an SMPS class AB the amp started to thermally limit at 1:30 of full output on a single channel. "The longest duration of more or less uninterrupted bass was 28 seconds with a pretty low crest factor." I feel this is towards the upper end of what is asked of amps. Contrast is needed in the music so going on much longer than 10s has diminishing returns. Yeah my amp looks quite close to what Powersoft is dong, much less sophisticated and not full range but similar results. I would love a couple of X8 but I don't think that's happening any time soon.

I'm in the UK where the most common power is 240V, 13A so that's my initial target*, but if I can complete the project I will try and do universal PFC. Basic topology is: 240VAC -> 3.5 kW boost PFC (390VDC output) -> three phase buck converter operating in average current mode control (this is where the maximum current regulation occurs which in turn will regulate the line current) (300VDC bus, that drops under load) -> Full bridge IGBT based, low switching frequency class D amp Input is digitized and a look ahead limiter with trajectory estimation on the rail voltage is used to avoid clipping. The buck converter is using microprocessor control so the maximum current can be set based on the available AC power and there is the possibility of lowering the 300VDC bus for IPAL compatibility. Another feature is no mains isolation to increase efficiency. Its early days at the moment I am working getting the buck converter stage test boards produced. One issue is actually testing this properly is going to require a really big electronic load! *I have made power converters before up to 90kW continuous output so I'm OK with going to higher currents but I don't have the facilities or test equipment at the moment and things get very expensive fast.

My commiserations on blowing the amp I have also had an amp blow during testing (DAP Audio Qi-4600), nothing aggressive just sustained 4ohm load on one channel. I then proceeded to totaly blow it trying to fix it. Forgetting that it had a bipolar supply I hooked the scope probe up to the negative lead of a decoupling capacitor, shorting the power supply and unleashing a spectacular fireworks show. My view is that if an amp fails like this its better than failing in a more critical situation and/or taking out speakers (the DC protect did not work on the Qi-4600, relay jamed shut). My main lock down activity has been working on a new subwoofer amp that addresses the stout AC line issue by using a current limited supply and large capacitors. The idea is that it never pulls a line current over a preset maximum but has huge transient energy reserves. The attached PDF shows the basic idea. Bass_hit_analysis.pdf

with the +19dBu issue quite a few amps are designed to give their maximum output at 18dBu input. So the input of something connected to your interface output could have some input voltage protection circuit that's causing distortion

Ah great I have added them to the list, I started the thread after getting a load of Cloud VTXs home and finding they where so loud that I could hear them clearly several rooms away from where they where on with a closed door! subsequently I fixed a few of the amps and found they had failed because the airflow over the circuit board in one particular location was so strong it had worn away the track that switched the output relay.

This is the best design I have seen so far. Especially for the compact size and ability to have such a wide selection of loads. I attach an image of my load bank which sits at the other end of the quality spectrum and is just a fixed 4ohms. I tested a couple of amps with this load here: https://www.diyaudio.com/forums/pa-systems/339848-quiet-pa-amps-5.html

Performance looks great, more output than my subs in half the size. You also don't have any deep cancellation notches from the port pipe mode.

for $1000 you could build many small sealed subwoofers and hide them round the room, this combined with equalization will sound great. If you get a multichannel amplifier with DSP you could use this: https://www.andyc.diy-audio-engineering.org/mso/html/index.html (also good links on the site). People seem to like this amp as a budget option (perhaps there is something similar in the US?): https://www.thomann.de/gb/the_t.amp_quadro_500_dsp.htm?ref=intl&shp=eyJjb3VudHJ5IjoiZ2IiLCJjdXJyZW5jeSI6IjQiLCJsYW5ndWFnZSI6ImVuIn0%3D

I have appeared to miss read the specs and just quoted the voice coil size. by distortion I was referring to high frequency THD which is limited by air non linearity and not low frequency distortion so I can confidently make this statement because the phase plug design of the AXI2050 allows extension to 20 kHz while the M200 has no phase plug and the BMS has a mid-range optimized phase plug: http://www.bmsspeakers.com/fileadmin/bms-data/product_data_2014/bms_4599nd_preliminary.pdf I'm building an old school style big stack of horns system at the moment for medium scale stuff so I have got a bit per-occupied with getting low distortion at high SPL.

I have had an interest in the K402 and AXI2050 for a while but the costs are so prohibitive. There is a lot of information about the AXI2050 in the horn loudspeakers book, one thing to note though is that although it has a 5" diaphragm the effective surface area of the diaphragm is less than a conventional compression driver (its still obviously huge though). Another thing to note if using these drivers at high SPL is that distortion performance in the midrange is worse than dedicated midrange drivers like the community M200 (still available), M4 (sadly out of production) and the BMS dual diaphragm mid range. Anyway I plan on building a similar horn to the K402 soon for the M200 (in UK paying for all the CNC work is much cheaper than a K402 and I can tweak the design for my needs). Are any of you simulating horns in ABEC3 or similar?

Simulating the CKRAM at full output with a 27Hz 4th order high pass I get ~35 m/S as the peak vent velocity. Previous designs of mine have had peak velocities in simulation ~25 m/s which resulted in 1 - 2 dB of port compression. Also my design for the 15BTX100 is coming out with 35 m/s vent velocity. Looking as designs on data-bass such as: https://data-bass.com/#/systems/5c48bfc611126b0004ca12eb?_k=sypf1q I don't see much evidence of port compression at tune in the long term output graphs even though vent velocity must be high. what kind of compression can we expect at 35m/s?

Great my mistake was that I thought the vent divers where 18mm not 12mm. I used method 3 for the length but its within 1cm of your number so the discrepancy could just be metric US customary units conversion as I work in metric. (although to be totally accurate Hornresps use of cm and cm^2 isn't metric...).

I'm going to adapt this design for my 15BTX100 so I have been going through it in order to understand things like how the bent port is altering simulation inputs. Firstly I calculate the port area as: 13.5 * (60.96-(5*1.8)) = 701.46 Based off the port height (13.5cm) overall width (60.96cm) and divider thickness (1.8cm) which differs from the Hornresp input for all vents open of 725.76, has the port area been increased to take into account viscus drag effects on tuning? Secondly for the port length I get 102.97 cm using just the mid point and 100.99 cm using the advanced center line method but the input is 102 cm so what method was used to arrive at this? *Also does anyone have complex inductance parameters for the 15BTX100? I'm having difficultly getting them my scales seem to have become inaccurate. advance_center_3rd.webp

Much more clear that makes sense. I would just use the baffle screws into the inserts and foam tape between the baffle and front assembly, not bothering with the end grain screws and relying on the clamping force to damp any vibration.

cool design! it reminds me a bit of my own subs. Mine differ in that its more of series design, with a port meeting an isobaric driver in the chamber with the cover plate on it. My simulations results (just reflex) where not matching in the upper bass, I hadn't thought about modeling it as a 6th order bandpass: https://www.diyaudio.com/forums/subwoofers/345807-isobaric-sub-based-pyle-plpw15d.html Looking at the plans for the CKRAM I don't quite understand how your driver cover attaches, as it appears to me that the design is saying to screw into the end grain of the ply?

I'm running my PA at a party at the end of the month and it will be the first time I am using my new design: https://www.diyaudio.com/forums/subwoofers/345807-isobaric-sub-based-pyle-plpw15d.html TL:DR >115dB/2pi/1m continuous from 30Hz. I have four of them which I will arrange in a coupled line configuration across the front of the stage. This is indoors so I should have some boundary reinforcement. Each sub is wired as 16 ohm nominal but there are the usual double peaks due to the reflex tuning. The drivers have 2.5" coils on an aluminum former. I never burnt a coil in the previous sealed boxes even when running into heavy limiting on nu6000dsp and having hot boxes (boxes wired for 16ohm). The cooling is much improved in the new cabs. During the power compression testing I see about 2dB compression in the excursion limited portions of the sweep applying 94V to the cab and about 1.5dB of compression at port tune. As this was right on the limit of the amp I was using (nu6000dsp) I'm not sure if its actually less. I have two amps available: NU6000DSP, P7000S In bridge mode the P7000S will do 200Vrms which would seem like it could be worthwhile as the cabs seemed to have a bit more to give at 94V.... however the amp is only rated at 8ohms bridged. Although tantalizingly there is a short duration power rating for 4 ohm bridged in the manual. As per usual I need everything I can get from all my get from my gear so I am wondering what combination of amps would work best. My current thinking is perhaps risking loading them all bridged onto the P7000s as actual impedance will (most of the time) be over 4ohms or running the center subs off the bridged P7000s and the outer ones off the inuke. My other question is what to set my thermal limiting to, I think 300w per coil is reasonable as they have an aluminum former so should cool better than typical non conductive formers. This gives 600W per cab and 97Vrms. With my limiters I can set attack and hold times up to 3s I would guess I want a attack time less than the thermal time constant of the voice coil and the longest release time possible?

Based on innovative M-Force® transducer from Powersoft®, THOR employs transmission line acoustic design, called in to maximize the performance and deliver otherwise unachievable SPL and frequency response. TH then, Stuffing?

Thanks for the tip on directivity I'm quite satisfied now that's what I'm seeing in the outdoor measurements: The gain (~6dB @50Hz) of the 'inbox' and compensated in room measurements over the bass reflex sim in horn resp I have also managed to reproduce by modeling the box as a stepped tapped horn, trying to keep volumes the same and include acoustic path lengths to the front and back of the driver. This sim is not totally faithfully to the actual geometry but is showing the same mid bass boost. Also interesting was the power compression tests I did they mainly show the amp running out of steam rather than the sub >70Hz in the long duration sweeps. So probably better test methodology would be to monitor actual drive voltage during the sweep for the higher level sweeps.

The drivers are wired in series for 16ohms. I reach xmax around 60V according to hornresp, within the output voltage limitations of an inuke6000dsp. By doing this I can run 8 subs off one amp. The above tests are renomalised to 4V (1W into 16ohm) and 1m. Actual drive voltage was 5.46V and distance 2m. microphone was umik-1 which is usb and calibrated, I don't have a calibrator to check but have always got plausible results when using it to develop full range speakers using time gated measurements. Voltages where measured using a true RMS voltmeter and a constant sine at 50hz at the same drive level as the sweep. I will have a look at the baffles directivity characteristics.