Direct Mode: Harder on speakers?

[Steve81]

That's another topic - limiters. Why use an amp that is too powerful for the driver in the first place and requires a limiter?

That's a chart showing excursion vs frequency for driver X for a couple different vented alignments and a given power input (200W). As you can see, below the tuning point excursion rises rapidly, meaning you need relatively little power to exceed the driver's limits at ultra-low frequencies. Now you could hamstring this driver with a 50W amp and not need to worry about limiters, abusive customers, etc, and call it a day. Or you can spec an 800W amplifier, throw in a rumble filter and a limiter to keep the system from killing itself, and realize a lot more performance.

 

[AcuDefTechGuy]

That's a chart showing excursion vs frequency for driver X for a couple different vented alignments and a given power input (200W). As you can see, below the tuning point excursion rises rapidly, meaning you need relatively little power to exceed the driver's limits at ultra-low frequencies. Now you could hamstring this driver with a 50W amp and not need to worry about limiters, abusive customers, etc, and call it a day. Or you can spec an 800W amplifier, throw in a rumble filter and a limiter to keep the system from killing itself, and realize a lot more performance.

I don't think anyone is looking for a 50W sub. Just one where the max power rating of the driver is more than the amp's power output.

For example, if the max power rating is 800W, then use a 700W amp. If the max power rating is 500W, then use a 400W amp.

And numbers aside, people should get the sub that sounds great to them. It doesn't need to be 800W to sound great or greater. A sub doesn't need to reach "full potential" to sound great. And if it sounds great with just 50W, then apparently it is not "hamstring". It's almost like the loudness war with compressed music. As if the sub needs to be powered with 1KW or 2kW to sound great? Or that it has to play 120dB @ 20Hz?

I guess it's about preference once again. I personally don't care for anything below 25Hz.

 

[Steve81]

I don't think anyone is looking for a 50W sub. Just one where the max power rating of the driver is more than the amp's power output.

For example, if the max power rating is 800W, then use a 700W amp. If the max power rating is 500W, then use a 400W amp.

The point is that it's not just as easy as looking at a driver's nominal rating. In the above instance, it's possible to drive the system past its linear operating range and possibly cause damage with far less than rated power. That's where limiters come in handy: to maximize the performance potential without putting the driver in danger.

And numbers aside, people should get the sub that sounds great to them. It doesn't need to be 800W to sound great or greater. A sub doesn't need to reach "full potential" to sound great. And if it sounds great with just 50W, then apparently it is not "hamstring". It's almost like the loudness war with compressed music. As if the sub needs to be powered with 1KW or 2kW to sound great? Or that it has to play 120dB @ 20Hz?

It really has nothing to do with loudness wars / SPL drag racing, and everything to do with being a balanced, and ultimately cost effective design for manufacturing. I mean, SVS could offer a 100W amplifier with their PB13U as opposed to the 1kW Sledge amp and charge a few hundred less for a PB13-Lite, but I'd daresay such a design would get universally panned as being a horrible value.

 

[3db]

SVS uses limiters, Rythmik uses servo control .

 

[herbu]

SVS uses limiters, Rythmik uses servo control .

First, thanks Steve81. We have now left the pedestrian crosswalk, and you confirmed there are indeed valid design considerations for a limiter switch, (I guess). But back in the crosswalk, it would seem desirable from the consumer view for a default design point that can handle normal, everyday music and movies... and have a limiter switch that can be used for unusual/excessive usage. If I have to turn it on for normal use, what would ever be the time to turn it off?

3db, my Rythmik sub has a "Limiter On/Off" toggle switch. My SVS does not have a Limiter option in the setup menu/choices.
So regardless of what's under the covers, Rythmik lets me turn it on/off, SVS does not. Maybe I should just consider that flexibility as a plus for Rythmik.
Both sound great, and I'm not sorry I bought either one of them.

 

[Steve81]

We have now left the pedestrian crosswalk, and you confirmed there are indeed valid design considerations for a limiter switch, (I guess).

Personally I have no idea why Rythmik implements it as a switch It's something you'd expect to leave on at all times to avoid bad noises & possible damage (which is a win-win situation for both parties). If you find yourself needing that last bit of power...it's really time for an upgrade IMHO.

 

[3db]

3db, my Rythmik sub has a "Limiter On/Off" toggle switch. My SVS does not have a Limiter option in the setup menu/choices.
So regardless of what's under the covers, Rythmik lets me turn it on/off, SVS does not. Maybe I should just consider that flexibility as a plus for Rythmik.
Both sound great, and I'm not sorry I bought either one of them.

I just went and checked onmy LV-12R. I have no such limiter switch on my sub; a control for slope, extension, and phase along with volume and power.

 

[JonnyFive23517]

My pedestrian conclusion is that the amp and driver are better matched. Maybe I'm wrong. I was once.

SVS has optimized that roll off slope to allow a lot of output without damaging the driver. So while it's not a hard limiter, I believe they've taken steps to make it hard for you to damage that sub. If you removed that roll off filter (which I think is similar/same as a rumble filter?) I bet you could damage the driver.

So perhaps it's a case of amp + driver + excursion control mechanism being well matched?

 

[Steve81]

SVS has optimized that roll off slope to allow a lot of output without damaging the driver. So while it's not a hard limiter, I believe they've taken steps to make it hard for you to damage that sub. If you removed that roll off filter (which I think is similar/same as a rumble filter?) I bet you could damage the driver.

So perhaps it's a case of amp + driver + excursion control mechanism being well matched?

To my knowledge, all SVS subwoofers utilize an advanced DSP limiter/compressor to keep things reasonably well behaved under even the most abusive loads. That is in addition to the rumble / high pass filter (or roll off filter if you prefer) which is noted in the FR measurements of all of their vented subs that I've seen. I know I got the limiter indicator to light up like a Christmas tree on my old PC12-NSD from time to time.

 

[AcuDefTechGuy]

Personally I have no idea why Rythmik implements it as a switch It's something you'd expect to leave on at all times to avoid bad noises & possible damage (which is a win-win situation for both parties). If you find yourself needing that last bit of power...it's really time for an upgrade IMHO.

Probably because some people feel that limiters compress the sound and limit the dynamics. You won't notice the compression most of the time. But limiters can compress the sound.

I think that's why my Funk and RBH subs sound so sensational and amazingly dynamic - I don't use a limiter.

The 2 Funk are getting the ATI AT3002 (450W into 4 ohms) and the 5 RBH are getting the ATI AT2005 (300W into 4 ohms).

 

[herbu]

I just went and checked onmy LV-12R. I have no such limiter switch on my sub; a control for slope, extension, and phase along with volume and power.

For another $900 you could have had a switch.

 

[Steve81]

I think that's why my Funk and RBH subs sound so sensational and amazingly dynamic - I don't use a limiter.

I dunno, I'd put my active 18.0SE's against one of your Funk's fed by your ATI and expect it to do just fine, limiters and all (no switch, sadly ).

 

[3db]

For another $900 you could have had a switch.

LMAO Good one

 

[AcuDefTechGuy]

I dunno, I'd put my active 18.0SE's against one of your Funk's fed by your ATI and expect it to do just fine, limiters and all (no switch, sadly ).

As long as it sounds good, that's all that matters.

I think most active subs come with some form of peak limiters or compression, but most people will never notice it and most sounds aren't extremely dynamic most of the time.

I find that passive subs without limiters do sound subjectively punchier and more dynamic than active subs.

Some people also complain that bass from active subs just don't sound as "musical" and dynamic as bass from tower speakers being fed by high quality amps without limiters.

And so I contribute this to the limiter.

Some people may also contribute this to the difference in amps, like high-end amps vs pro amps. However, I am not one of those people, although I find high-end amps to be more fun to own and use.

But, regardless, the only thing that matters is that the subwoofer sounds great, active or passive, limiter or no limiter. Whatever sounds great is the important thing.

 

[Josuah]

Unless I'm thinking of a different limiter than you are, an amplifier limiter is included so that if the input signal plus the amplification level would result in an final signal that is too high, the final signal is instead limited to something lower. This prevents clipping and overdrive of the amp electronics and speaker. Without the limiter, the amp and speaker could be damaged.

But any limiter built into an amp is going to only care about the amp's limits. It won't know what your speaker limits are. Active speakers like most subwoofers are going to pair the amp properties to the speaker and enclosure to prevent damage to both the amp and driver. But otherwise using a 400W amp that contains a limiter with a speaker only capable of handling 50W and then turning your volume all the way up will still destroy your speaker.

In theory a limiter should never be engaged if your input and resulting signals are not too high. But of course the limiter consists of circuitry so it could affect the sound quality even if that scenario isn't hit. I have my doubts as to a limiter resulting in the audio characteristics you described but I haven't done any serious experiments to find out. I'm pretty sure most amps include a limiter for their own protection, and maybe they even need to for UL/CE certification (in which case all pro amps would).