Okay I ordered the Driverack PA2 🙂 but following DBX Driverack 260 auction and waiting for the t.racks FIR DSP 408 to be available again.
The specs of the dual 15" JBL say "1350 W (5400 W peak)" so for each of the two 15" it would be 675W (2700W peak) right? What would be the optimal power of the amp per channel? When I had the Behringer NX-6000D going half way was already LOUD and in most cases we won't need so much. The PLX 2402 was 300 and I could use it for the JBL AC18/95. So I'm still looking for a decent amp for both JBL ASB6125.
Thank you for the picture but I cannot make complete sense of it. It looks like the back of the CD is embedded in the box and protrudes outwards. But the JBL 2450H as Hifi connectors at the back and I need to connect them to Speakon sockets. Hence they can't be outside but must be inside the box with the Speakon socket facing out. How about cutting a hole in a board with the diamater of the CD at point A (see below) and mounting that board inside the box? There are also holes at point B but they have no thread and I have no clue what they are for?
The idea would be to all EQing and other adjustments from the tablet so all we would need is a mixer instead of a huge FOH area.
I have no idea what it does to be honest. But let's say you're deciding between DBX Driverack PA2, DBX Driverack 260 (used) and t.racks FIR DSP 408 all about the same price, you wouldn't hesitate to buy the t.racks FIR? It won't run on Mac or iOS though which may not be a dealbreaker.
I will, thanks for the link. BTW: they always talk about rooms. But I assume they're also suitable for outside venues?
Do you know how this support usually looks like? Would the board with cutout at point A (see above) be the correct approach?
The processing your speakers need for optimal performance and protection should be setup before the system ever sees an event, this processing should not change at each venue. If the system needs any additional EQ at an event it should be easily done on the mixer.
I'd buy the DR260 because of the routing limitations in the PA models(can only do stereo configs), but any FIR based unit will have a current processor inside versus a 10-20yr old processor found in the Driveracks.
You're still thinking you can use these tools at venues, I promise you this won't be the case most of the time. But to answer your question the "Room" part of the name simply indicates the designer was thinking more home audio applications, but the software doesn't know if the speakers are in a room or outside.. the operator has to know how to decipher the data the software presents.
There are lots of possibilities, you can find metal brackets that mount between the driver and horn, this drivers appears to have mounting eyelets so you could do something as simple as bolt a small L bracket to one of those holes and then attach that to a block of wood that sits under the driver.
Yes, you have divided by 2 correctly.
Around 3000-6000 watts peak into 4ohms would allow the JBL ASB6125 to reach their peak output potential, which could damage hearing of anyone near the speakers not wearing hearing protection.
The NX-6000D can do ~3000 watts peak into 4 ohms, or 1600 watts into 8ohms per channel.
It has useful power indicator LED lights:
"Limit" illuminates when ~ 3000 watts peak into four ohms is reached,
The amp will limit power to under that if the input exceeds 0dBu (.775volts) with the input volume control turned fully clockwise.
Most mixers can exceed that level by 20dB or more.
"-3dB" illuminates ~ 1500 watts (half power).
"-6dB illuminates ~ 750 watts (1/4 power).
"-40dB" illuminates ~3 watts.
Your JBL ASB6125 2x15" sensitivity is around 100dB SPL (sound pressure level) 1/w1m outdoors.
100dB 1watt
110dB 10watts
120dB 100watts
130dB 1000watts
133dB 2000watts
136dB 4000watts
Outdoors, each doubling of distance reduces level by 6dB. Indoors, levels are room dependent.
Outdoors, at 10 meters, 100watts (+20dB) would be required to reach the 1w/1m level.
The picture showed exactly that, a circular support hole the diameter of the EV DH1A compression driver at point A cut into a piece of plywood.
The "holes at point B" attach the 2350's 1.5" to 2" throat adapter.
Without the adapter, the driver would be a 2450SL, a 1.5" exit driver.
Horns are made to fit specific throat diameters.
Art
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Ok then the Mac/iOS issue won't be a deal breaker. I probably return the PA2 and get the t.racks FIR.
True but wouldn't it adjust everything based on the measurement microphone, e.g. it will "hear" no reflective surfaces so it will adjust accordingly or is this to naive? We won't need acoustics of an opera hall just avoiding things are too far off.
Not bad but I wonder why it's used for home cinema i.e. listed under Cinema Sound > Immersive Rooms > ASB6125
That's interesting and a bit confusing. So at 10 meters away to have 100dB (which is quite loud), we only need 100W? Also your dB > Watt chart shows extreme diminishing returns beyond 1000W. Should I not scope the amp to this level, i.e. a little above 1000W per channel?
Thanks, I didn't know the difference between these. But I actually meant the holes as seen below. Do they have any purpose? They don't have threads, just holes.
Yes the mic input is all it has to work with, the problem is the processing doesn't know why the response it measures has non linearities and the only tool it has to correct that is to boost or cut with EQ. If the mic happens to be positioned in a node where there is cancellation at a certain frequency due to different arrival times from the speakers, no amount of EQ will fix this the only thing that does affect it it moving the speakers or the mic. Same applies to phase and time alignment issues through the crossover region, these cannot be fixed with EQ. Bottom line is developing effective corrective processing for a loudspeaker system requires a lot of manual hands on testing and experimentation, it's not something that has been sucessfully automated yet.
The listing has everything from 2-way 8"/HF, to four-way 2x15", 4x8" + 4"/HF.
"Large format and 3D cinemas require perfect coverage in every seat of the auditorium, wide dynamic range and extended bandwidth, as well as inaudible levels of distortion. Digital soundtracks require sound systems for premier auditoriums that can accurately reproduce the sound exactly as recorded."
An experienced contractor will pick what is appropriate for the room size and SPL requirements.
Yes, that's what the specifications say.
You are confused because you are not yet conversant with the inverse square law and the concept of the decibel, a unit used to measure the intensity of a sound or the power level of an electrical signal by comparing it with a given level on a logarithmic scale.
The decibel and inverse square law are as basic to sound as the 12 note octave scale is to western music.
The decibel concept is now 100 years old, I only became aware of it about 50 years ago (-3dB) 😉
What you call "diminishing returns" is inherent in the logarithmic nature of sound propagation and perception.
If you decide you don't want to use the +6dB headroom available above 1000w (4000watts), no need to buy an amp with that "scope".
The extra +6dB allows twice the coverage distance.
Then again, if you don't want to use that output, you could get by with two 15" rather than four..
They can be used to attach shackles or support brackets similar to this JBL cinema system:
Have fun, good luck!
Art
Thank you especially @weltersys & @conanski. MY next "project" is to do it completely digital so I posted this:
What else than an Apple Mac Pro M3 do I need to replace DBX Driverack PA2
What else than an Apple Mac Pro M3 do I need to replace DBX Driverack PA2
Mike,
To go "completely digital" will also require your amplifiers to also have digital inputs compatible with your chosen architecture..
I chose to use the BSS (Brooke Siren Systems) BLU-100 12x8 Signal Processor with London Architect software with my older Mac computers and analog input amplifiers.
Very flexible, and can do FIR implementation.
I found the learning curve for it difficult, forgot more than I remember.
I've since sold it with the speaker system it processed, and now still use my DBX DriveRack PA for my various system processing.
Art
To go "completely digital" will also require your amplifiers to also have digital inputs compatible with your chosen architecture..
I chose to use the BSS (Brooke Siren Systems) BLU-100 12x8 Signal Processor with London Architect software with my older Mac computers and analog input amplifiers.
Very flexible, and can do FIR implementation.
I found the learning curve for it difficult, forgot more than I remember.
I've since sold it with the speaker system it processed, and now still use my DBX DriveRack PA for my various system processing.
Art
I was wondering why in the age of M4 Apple Macs we still use hardware crossovers decade-old design rather than everything software-based. Here is why: https://www.diyaudio.com/community/threads/pc-as-active-crossover.293156/post-4765097
Do you agree the t.racks FIR DSP 408 is at least a newer design and perhaps better than the PA2?
Certainly newer and far more capable, though I have no working knowledge of it's software/hardware/user interface.
FIR capability is really a game changer, whatever platform you decide to adopt, and has become affordable now.
Properly implemented FIR processing is the reason cheap powered cabinets can now out-perform older IIR based systems that use better drivers.
Art
Does someone (@weltersys 😉) have some feedback regarding the SRX828S? I realized with the JBL ASB6125 I don't get so much sub-Bass frequencies, I mean the deep, rumbling sounds. I found the HPF at 40Hz works well, otherwiseI get a lot of air moving but not much sound. I could get one SRX828S at half price. Would it be a good investment? At least on paper, it doesn't go much deeper than the ASB6125 though.
Not a good investment considering what you already own.
As mentioned in #20, your JBL ASB6125 Fb (tuning frequency) is 40Hz (the impedance and excursion minima), response is -6dB at Fb.
Depending on the slope and type of HPF your HP may a bit high at 40Hz.
Using a BW24 HPF at 35Hz may allow a bit more LF than what you are using, and a +6dB boost around Fb would make quite a difference in the perceived "depth".
Of course, your room will have a huge influence on the low end response, you could be listening in a null point..
Since you have found your JBL ASB6125 to have more than enough output above 40Hz, you could lengthen it's ports to drop the Fb down to around 31Hz and get another 1/3 octave of useful low end from the cabinet, though more low boost/upper cut would be required to flatten response.
The SRX828S Fb is likely similar or higher than the ASB6125, unfortunately JBL's specifications of a passive cabinet using undefined "Main Tuning" and no impedance curve makes comparisons difficult.
My estimation is you won't get any lower output from it than your ASB6125, though due to the 2279H larger cone area and higher Fb, the SRX828S is capable of more output above ~45Hz.
Art
Where are you listening to this system while making these observations?
VLF response indoors is always dominated by the listening enviromment, it's is impossible to avoid substantial room nodes that create hugh nulls in the systems response. Outdoors away from structures that problem goes away and you can hear everything the system produces but because there are no walls to contain sound you will find you need 6dB more sub output to achieve the same percieved overall subbass levels you get indoors.
Also, achieving good PA system output across the bottom active(20-40hz) is generally the reserved domain of advanced/upscale operators, this is because it requires a lot of large and expensive equipment outdoors and some advanced engineering techniques to reliably accomplish indoors without negatively impacting other aspects of system performance. In short that subbass range just becomes an indistinct quagmire of mud once room reverberations are added so in most cases engineers do thier best to filter it out of the PA system.
For lower level operation, you could cover one port- Electro-Voice called this the "step down" mode, which would drop Fb by ~1/3 octave.
The port cover could easily be removed if you want to trade the LF response for more output.
The EV TL15-2 drops from 40Hz to 28Hz with one port covered:
https://products.electrovoice.com/binary/TL15-2_Engineering_Data_Sheet.PDF
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Thank you for the responses! I'm currently solving the crossover approach. I'm not happy with the Driverack PA2 and will return it. It's great and easy to set up and operate but only goes half-way digital compared to the t.racks FIR DSP 408 at almost same price. But that thing doesn't have Mac-software so I went down the Mac-as-DSP path. I installed CamillaDSP with simple XO config and using Behringer UMC404HD and all works good. I found out that crossing over at 1600Hz gives a much fuller sound in the mids.
Is it safe to run the up to 1.6 kHz JBL ASB6125 which is rated 32 Hz - 1 kHz ?
Is it safe to run the up to 1.6 kHz JBL ASB6125 which is rated 32 Hz - 1 kHz ?
So given the image below, I would create four triangular extensions that fit into the triangular holes/ports of the JBL ASB6125?
Optionally, instead of one triangular extension, I would close one of the triangular holes/ports but which one and only one or two?
Yes, it is "safe". The higher the crossover frequency, the more narrow the dispersion of the 15".
Previously, I wasn't aware the ASB6125 cabinet had four ports with two different dimensions.
You could extend all ports, or pairs.
If the cabinet is split internally, one smaller and one larger port tune each chamber.
The two ports of different dimensions combine to one aggregate tuning.
Covering the smaller port may lower the Fb less than covering the larger port.
That gives three tuning options per chamber:
1) Both open-40Hz
2) Smaller port closed ~35Hz
3) Larger port closed ~30Hz
If both speakers share the entire cabinet, you have more tuning options.
The more ports covered, the lower the Fb, but the higher the vent air velocity.
At higher velocity more vent noise can be heard, and less SPL is possible before the lesser air volume in the ports becomes "blown out".
Art
I was wondering if I'm getting down to 30 or 35 Hz in this way, would it impair the upper frequency range, i.e. around 1400-1600 Hz?
A lower Fb shouldn't have much effect on the upper frequency range until the drivers approach or exceed Xmax.
When driven past Xmax, the upper frequency range becomes amplitude modulated by the low frequency excursion, and may sound "gargly".
Efficiency drops with a lower Fb, so more excursion will be required for a given SPL down low.
When driven past Xmax, the upper frequency range becomes amplitude modulated by the low frequency excursion, and may sound "gargly".
Efficiency drops with a lower Fb, so more excursion will be required for a given SPL down low.
Hi Art, I now got the BSS FDS 360 (wasn't happy with the Ethernet-only connection of the PA2, lack of Mac software of the t.racks FIR DSP 408 and with the Mac-as-DSP using CamillaDSP). How do I know which crossover point is set with the cards that came with it? The cards in FC1 and FC3 look identical to the image below except that R5B and R7B are not soldered on i.e. empty.
Okay now I need to read the colors. Some are thick, some are thin, some are barely visible, some are weird... how will this ever be reliable?
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