Cheap watts for sub array? - Page 2

paulspencer · 17th January 2005, 01:00 PM

I prefer the pro amp + sub processor route

* don't need to mount amp in the box >>> design flexibility
* more watts for your dollar
* PA amps have more authority in my experience

You do need a processor, not BFD. You need things like a rumble filter, lowpass filter at the very least. A diy kit is a good way to go.

Bogie · 17th January 2005, 05:29 PM

Okay - I'll figure on using a pro amp, along with a crossover and the BFD (hey, I'm already using it...).

My design models out to not have gnarsty cone excursion down to about 15 hz or so. A "rumble filter" is basically just a very low highpass, right?

simon5 · 17th January 2005, 05:34 PM

Exactly, but if you can put the very low highpass before the pro amplifier, it's way cheaper in components when you work on a 5V signal or so.

paulspencer · 18th January 2005, 04:37 AM

A rumble filter is a high pass filter, typically at 20 Hz or lower, often with a slope of 3rd - 6th order. If you model with WinISD you can find out what slope and corner frequency you need. I'd aim to make sure that the excursion below 20 Hz would never be greater than that above 20 Hz. If this is true, you aren't likely to have excursion problems with low signals. Some movie effects go down VERY low, keep in mind, sometimes as low as 2 Hz. Looking at my RTA when watching movies with low bass, I've noticed some rise in amplitude when you go down lower, which is likely to cause you excursion problems.

The basic idea of a rumble filter is to avoid overexcursion in the range that is too deep for your system to reproduce useable output. No sense giving up what you can hear for the sake of what you can't.

Bogie · 18th January 2005, 05:27 AM

Just checked on WinISD, and a combination of a 4th order highpass at 15hz, and a bit of judicial use of a parametric equalizer, could keep cone excursion under control, while cutting spl only approx 1db at 20hz...

Hmmm... Now to pull out The Book From Hell, and see if I can figure out a 6th order filter...

paulspencer · 18th January 2005, 05:51 AM

No need to reinvent the wheel, ESP have a 6th order rumble filter PCB ...

Bogie · 18th January 2005, 06:16 AM

Paul...

I understand PCB, but what's ESP? I'm not psychic...

(grin)

paulspencer · 18th January 2005, 07:20 AM

Elliot Sound Products

http://sound.westhost.com/

Bogie · 18th January 2005, 01:05 PM

Hmmm... that stuff looks INTERESTING.

It's project 99, right?

I may also try the sub amp project.

paulspencer · 18th January 2005, 01:11 PM

Correct.

I considered building an amp, but concluded in the end it was no way to save money. YMMV but I foudn it was more expensive than a NEW amp, and you don't get a warranty with diy. The only thing is, you learn from diy and you have a better chance of fixing it if anything goes wrong (very rare).

17th January 2005, 01:00 PM	#11
paulspencer diyAudio Member Join Date: Sep 2003 Location: Melbourne, Australia	I prefer the pro amp + sub processor route * don't need to mount amp in the box >>> design flexibility * more watts for your dollar * PA amps have more authority in my experience You do need a processor, not BFD. You need things like a rumble filter, lowpass filter at the very least. A diy kit is a good way to go. __________________ Red Spade Audio Blog \| Writer for: Hifi Zine S3 Synergy horn + 18" active woofers + T20 horn sub + B&C active surrounds + Custom Acoustic Treatment

17th January 2005, 05:34 PM	#13
simon5 diyAudio Member Join Date: Nov 2004 Location: Québec, Québec	Exactly, but if you can put the very low highpass before the pro amplifier, it's way cheaper in components when you work on a 5V signal or so. __________________ DIYaudio for President !

18th January 2005, 04:37 AM	#14
paulspencer diyAudio Member Join Date: Sep 2003 Location: Melbourne, Australia	A rumble filter is a high pass filter, typically at 20 Hz or lower, often with a slope of 3rd - 6th order. If you model with WinISD you can find out what slope and corner frequency you need. I'd aim to make sure that the excursion below 20 Hz would never be greater than that above 20 Hz. If this is true, you aren't likely to have excursion problems with low signals. Some movie effects go down VERY low, keep in mind, sometimes as low as 2 Hz. Looking at my RTA when watching movies with low bass, I've noticed some rise in amplitude when you go down lower, which is likely to cause you excursion problems. The basic idea of a rumble filter is to avoid overexcursion in the range that is too deep for your system to reproduce useable output. No sense giving up what you can hear for the sake of what you can't. __________________ Red Spade Audio Blog \| Writer for: Hifi Zine S3 Synergy horn + 18" active woofers + T20 horn sub + B&C active surrounds + Custom Acoustic Treatment

18th January 2005, 05:51 AM	#16
paulspencer diyAudio Member Join Date: Sep 2003 Location: Melbourne, Australia	No need to reinvent the wheel, ESP have a 6th order rumble filter PCB ... __________________ Red Spade Audio Blog \| Writer for: Hifi Zine S3 Synergy horn + 18" active woofers + T20 horn sub + B&C active surrounds + Custom Acoustic Treatment

18th January 2005, 07:20 AM	#18
paulspencer diyAudio Member Join Date: Sep 2003 Location: Melbourne, Australia	Elliot Sound Products http://sound.westhost.com/ __________________ Red Spade Audio Blog \| Writer for: Hifi Zine S3 Synergy horn + 18" active woofers + T20 horn sub + B&C active surrounds + Custom Acoustic Treatment


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17th January 2005, 05:29 PM	#12
Bogie diyAudio Member Join Date: Dec 2004 Location: St. Louis	Okay - I'll figure on using a pro amp, along with a crossover and the BFD (hey, I'm already using it...). My design models out to not have gnarsty cone excursion down to about 15 hz or so. A "rumble filter" is basically just a very low highpass, right?

18th January 2005, 05:27 AM	#15
Bogie diyAudio Member Join Date: Dec 2004 Location: St. Louis	Just checked on WinISD, and a combination of a 4th order highpass at 15hz, and a bit of judicial use of a parametric equalizer, could keep cone excursion under control, while cutting spl only approx 1db at 20hz... Hmmm... Now to pull out The Book From Hell, and see if I can figure out a 6th order filter...

18th January 2005, 06:16 AM	#17
Bogie diyAudio Member Join Date: Dec 2004 Location: St. Louis	Paul... I understand PCB, but what's ESP? I'm not psychic... (grin)

18th January 2005, 01:05 PM	#19
Bogie diyAudio Member Join Date: Dec 2004 Location: St. Louis	Hmmm... that stuff looks INTERESTING. It's project 99, right? I may also try the sub amp project.

18th January 2005, 01:11 PM	#20
paulspencer diyAudio Member Join Date: Sep 2003 Location: Melbourne, Australia	Correct. I considered building an amp, but concluded in the end it was no way to save money. YMMV but I foudn it was more expensive than a NEW amp, and you don't get a warranty with diy. The only thing is, you learn from diy and you have a better chance of fixing it if anything goes wrong (very rare). __________________ Red Spade Audio Blog \| Writer for: Hifi Zine S3 Synergy horn + 18" active woofers + T20 horn sub + B&C active surrounds + Custom Acoustic Treatment

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