BillFitzmaurice.info

"dynamic compression of -20 dB at 50 Hz"

I'm not familiar with that measurement spec. Can someone explain that in layman's terms for me?

Rich4349 wrote: ↑Tue Jul 19, 2022 10:39 am "dynamic compression of -20 dB at 50 Hz"

I'm not familiar with that measurement spec. Can someone explain that in layman's terms for me?

Example:The soundboks is flat from 40hz to 20000 hz playing at 90 dB. But if you turn it up - the bass can't keep up because of various reasons - so that doesn't get any louder, but everything else does. The Dynamic compression graph shows a frequency response at a specific SPL. Normally, turning up the volume will cause distortion - but the designer implements a dynamic EQ to turn down the bass, as the volume is turned up. Thereby having a speaker, that will only play as loud as it's capable off, at all frequencies.

Does that make sense?

I understand it, but it doesn't make sense.

It also used for ported subs. You play the sub at 80 db, and the sub at max output. Then subtract the two curves - that's basically a compression curve. If the port "Chufs" the sub is not able to play the tuning frequency as loud as other frequencies.

Found the "Worst case scenario" for the soundboks 2. Pretty impressive for 2x10 inch on battery power. And i don't really get how

https://imgur.com/a/Sl6ql

JensToft91 wrote: ↑Wed Jul 20, 2022 10:23 am Found the "Worst case scenario" for the soundboks 2. Pretty impressive for 2x10 inch on battery power. And i don't really get how

https://imgur.com/a/Sl6ql

And after calculating how loud i should be able to play with a Tuba HT and 200 W I no longer believe that graph.
200w should be a 23 db gain - 100 db sensitivity at 50 hz, should be 123 db.

The amps in a soundboks is around 70w, or 19db gain. So they're saying that 2 10inch in a vented cabinet is more sensitive than a tuba HT.

Can you confirm?

JensToft91 wrote: ↑Wed Jul 20, 2022 12:39 pm
Can you confirm?

Your figures are good.

When I saw the graph, without any accompanying context such as methods used to capture and calibrate, "I don't think so" was my first thought. But, I didn't want to open that conversation and make the argument that's it's BS. Glad you caught that on your own

The breakup in the high end suggests to me that the measurement may have been taken near a boundary. But, that's pure supposition. Just a thought.

Seth wrote: ↑Wed Jul 20, 2022 12:55 pm But, I didn't want to open that conversation and make the argument that's it's BS.

That measurement was brought to you by the same people that produce the wattage ratings for Behringer amps.

Bruce Weldy wrote: ↑Wed Jul 20, 2022 1:05 pm

Seth wrote: ↑Wed Jul 20, 2022 12:55 pm But, I didn't want to open that conversation and make the argument that's it's BS.

That measurement was brought to you by the same people that produce the wattage ratings for Behringer amps.

No, no, no... in this case, it appears something was actually measured.

He's explaining everything here, including that high frequency dip, and measurement methods.

https://www.reddit.com/r/diyaudio/comme ... t/db7crdw/

I wish I'd just buy a book about sound, 1000 pages long, so i know the answers to all these things. It irritates me, that I firmly believe something must be off - and he still insist that this is completely true.

I just cannot wrap my head around, that we're building huge 12 inch horns - and someone comes along with 15 kgs, with a harness to carry on your back - with measurements of 123 db at 60 hz. On a 12v battery.
But - i've listened to it myself - the sound is impressive at lower-mid volumes, but max it out and you're like: Can you please please turn that shit down? - the bass thins out, and it just starts to scream.

I really like sound - but damn. It's a source of frustration to say the least. I really don't like, when there's something i don't understand.

The system is EQ'd up to about 2kHz. That's why it's so flat to there, and why it's not above that. The SPL level is suspect. Knowing the box design and driver used it would take me all of ten minutes to confirm or disprove it.

JensToft91 wrote: ↑Wed Jul 20, 2022 2:44 pm I wish I'd just buy a book about sound, 1000 pages long, so i know the answers to all these things.

432 pages, and $26. Go for it!

https://www.amazon.com/Sound-Reinforcem ... 7335&psc=1

Being from 1988 most of what's in it would be obsolete. No line arrays, no Bluetooth, no DSP, no digital boards.

Bill Fitzmaurice wrote: ↑Wed Jul 20, 2022 4:04 pm The system is EQ'd up to about 2kHz. That's why it's so flat to there, and why it's not above that. The SPL level is suspect. Knowing the box design and driver used it would take me all of ten minutes to confirm or disprove it.

All it says on the website is 3x72w amps, 2x10 inch (sensitivity: 96 db.), 1 "compression tweeter" (104 dB).
The box is vented, and is 66cm x 43 cm x 32cm overall.

So, when's this neighborhood party deal gonna happen?