Sending less than RMS to Dynaudio drivers?

[SCtud]

I keep reading about people throwing way over the RMS ratings to Dynaudio drivers because of their power hungry reputation. I'm curious as to what actually happens when the Dyns are fed less than RMS or just under it?

As a backdrop, I am contemplating throwing 100 watts to each driver from some Tru billets to a set of Dynaudio Esotar 430s 4" mids and MW182s 9.5" mid-woofers. Both drivers seem to be rated b/w 150-180 watts RMS (and it seems everyone who has them throws them 200+ watts each). I guess the same question would apply to the subwoofer (300 watts to a 400 RMS rated subwoofer).

Is the actual impact decreased output levels? Do you lose some sound quality or punch from the driver? Do you end up driving the amplifier too hard and risk overheating/damage? Can you compensate by boosting the gain or eq'ing on those channels?

I'd rather not add another amplifier for a couple reasons - space limitations, desire to minimize number of components, and desire to minimize load on the alternator/battery.

Here's a bonus question - does an IB subwoofer need more, less or the same power as a sealed/ported one?

[gymrat2005]

TRU amps are rated pretty conservatively. I mean a B4100 is calling for a 100 amp fuse, where an alpine PDX 4.100 only calls for 60amp fuse, so it's not always cut and dry. A Billet would be just fine to run with the Dyn's. Sound quality would not be effected at all. Just depends on what type of listening level you are used to, or trying to achieve.

[m3gunner]

OK... I'll bite.

The difference between 100 watts and 200 watts is exactly 3 dB.

The difference between 300 watts and 400 watts is exactly 1.2 dB.

If that difference in SPL is important to you, then by all means go with the larger amp. I'm running 75 watts per channel active to a pair of Dynaudio MW150s and they're loud enough to chase me out of the car. I used to run them on 150 watts with a Dynaudio xover. It was enough to chase me out of the car.

The key is making sure that you can make your desired SPL without your amp clipping. Dynaudio drivers can soak up just about anything you can throw at it, but it's more about how loud you want to go...

There are a lot of variables in your bonus question... but the typical IB driver is:

1. More efficient than the the same driver in a sealed box.
2. Handles less power than the same driver in a sealed box.

I don't do vented boxes, so I can't give you good feedback on that one...

[SCtud]

I guess the alternative question is, what is the benefit of throwing so much extra power to the Dyns if they are fine with running at or below RMS?

Is the objective because the listener wants to play the music that loudly? Keep the amplifier running at the lowest gain levels?

[jp88]

Originally Posted by SCtud

I guess the alternative question is, what is the benefit of throwing so much extra power to the Dyns if they are fine with running at or below RMS?

If they are not then you will be in trouble when you turn the volume knob down

[SCtud]

I've read about the logic that "underpowering" speakers doesn't damage them and am more interested in the effects on the resulting sound than possible damage (well, I'm actually concerned about damage to the amplifier from possibly trying to drive it too hard to achieve volume levels).

So to turn to real world numbers - and I'm inferring this math based on this thread (3 db - 10 db increase [ explained ]) which I may be interpreting incorrectly.

If the speakers are rated at 90db sensitivity (oddly, I can't find the sensitivity specs so just guessing) - will I get 90 db (translates to lawnmower loudness according to "howstuffworks.com") if I throw it the RMS wattage? And thus, with 100 less watts, do I end up with 87 db (90 minus 3)? Since listening above 85db "can" cause hearing loss, I don't imagine I'd listen for prolonged periods of time at those levels, but am curious as to what this setup maxes out at (I have a convertible which requires louder playing when the top is down).

[jp88]

No, sensitivity is either rated at 1w/1m (1 watt/1 meter) or 2.83v/1m. for every doubling of power you will add 3 db theoretically.
The only problem you can run into by using too small of an amp to run speakers is caused by Operator error. The problem I speak of is when a amp is just under the thermal power handling of the driver, and the operator drives the amplifier into clipping. When this happens the amplifier can deliver a square wave that may be greater than the thermal power handling of the driver.

[SCtud]

how does one calculate the starting db from which to base the + or - db from RMS wattage?

[sqshoestring]

I forget, I use a model to tell me dB its easier.

A sub IB typically will handle half its box RMS rating then it will xmax. When it hits xmax is all you have to worry about, not a number. You can subsonic them and run more power before you xmax as lower frequency takes more cone travel. However if you can run multiple subs at low xmax, you will get very low distortion from the subs.

Most SQ people will run huge amps, but the turn the gain down. Why....well because music is made of peaks of sound, so if you get close to your amps max output and hit a peak it will clip. If you never want it to clip you get a larger amp. Especially on dynamic music as compared to modern compressed rock/pop. Remember if you are listening to 1 watt (usually a normal TV has a 1w amp, so that all the way up) and the sound gets twice as loud on a drum or something you need 10w to not clip. Same for 10w double the volume is 100w.

[quality_sound]

The first thing I'd recommend is running them active. I had mine (System 340) off a bridged 4150XXK and I HATED them when run passive.

[SCtud]

How are you running them now? 320 watts to each side is some serious power, though I would be sending a similar amount (100x3, or ~130x3 if you believe that the Trus are roughly 30% underrated).

[quality_sound]

I'm not. I haven't had them 2 or 3 years now. I could never get the 140/2 to sound worth a crap no matter what I did and I didn't have the room for the 5.25" mid so I sold them when I sold the car and moved on.

130x3 isn't the same as 320 through a passive. For the sake of argument we'll say the passive doesn't soak up any power. Each driver would have the same 320 Watts available because they're playing different freq. bands.

Having said all of that, Don is running a single B8 to his Esotar setup (110s, 430s, 650s, 1200s) and eh said it rattles the walls so I'm thinking you'd be fine with a single B8.

[m3gunner]

Originally Posted by SCtud

how does one calculate the starting db from which to base the + or - db from RMS wattage?

You can use either a measurement (with an SPL meter) or the factory rating. You have to be careful with how they measure it at the factory, however, as some use 1 watt at one meter and others use 2.83 volts at one meter for the reference.

2.83 volts is 1 watt... but only for 8 ohm loads. For 4 ohm loads, it's actually 2 watts (you need to subtract 3 dB from the rating to get the 1 watt dB rating).

If they're using 1 watt, you can get the total dB by doing this calculation:

dB + (10* Log(Power))

So, let's say you have a driver that does 90 dB at 1 watt at one meter and an amplifier that puts out 50 watts. The calculation is:

90 + (10* Log(50)) = 107 dB

If you're trying to find the difference between two wattages, you can do this calculation:

10*Log(wattage2/wattage1)

So... moving from 50 to 100 watts:

10*Log(100/50) = 3 dB

The cool part is that it works the other way as well:

Moving from 100 to 50 watts:

10*Log(50/100) = -3 dB

This totally points out the diminishing returns thing:

Moving from 10 watts to 100 watts = 10 dB (humans perceive this as a doubling in loudness)

Moving from 100 watts to 1000 watts = 10 dB (again... a doubling of loudness)

[Problemhouston]

I’m running Dyn 6 and tweet through the passive dyn crossover. I’m lacking midbass in my truck but I am guessing it’s because I don’t have enough power going to the 6. They are being powered by a McIntosh 50x2 amp (MC425). Gains on the amp are about 60%. My question is with the amp info I just gave about how many watts should I assume are getting to the 6's? I have them wired from the crossover at + - 0db for both the mid and tweet.

When I go active I will be powering the 6's with an MCC222 that is rated 110x2 and the tweets will get the MC425. And finally the MCC82 with 40x2will take care of center channel duty.

[cyberdraven]

IMHO, any speaker will sound decent but will have problems handling transients, peaks and lows if underpowered by any amp. Look at it this way, when a speaker says 150RMS and 300watts Max, your amplifier must be able to supply enough power for those transients that go 300W. Usually, speakers maximum ratings are double their RMS ratings.

However, for amplifiers, if you will notice, most of them will have 20-50% maximum ratings as compared to their nominal/ RMS ratings. Which means that if you power a speaker rated at 150RMS/300W peak with an amplifier rated at 150RMS/200W peak, you will not harvest the full potential of your speakers.

Remember also that when you use passives, you will encounter huge losses and could go as high as 50%.

I follow the rule of thumb of thumb here in diyma that in choosing, get an amp that pumps out power equivalent to atleast 150% of your speakers RMS ratings. If you will notice, most competition-grade set-ups powers as much as twice the RMS ratings of their speakers.

You will gain the full potential of your speakers as well as good headroom! Think about it.

[gymrat2005]

Originally Posted by cyberdraven

IMHO, any speaker will sound decent but will have problems handling transients, peaks and lows if underpowered by any amp. Look at it this way, when a speaker says 150RMS and 300watts Max, your amplifier must be able to supply enough power for those transients that go 300W. Usually, speakers maximum ratings are double their RMS ratings.

However, for amplifiers, if you will notice, most of them will have 20-50% maximum ratings as compared to their nominal/ RMS ratings. Which means that if you power a speaker rated at 150RMS/300W peak with an amplifier rated at 150RMS/200W peak, you will not harvest the full potential of your speakers.

Remember also that when you use passives, you will encounter huge losses and could go as high as 50%.

I follow the rule of thumb of thumb here in diyma that in choosing, get an amp that pumps out power equivalent to atleast 150% of your speakers RMS ratings. If you will notice, most competition-grade set-ups powers as much as twice the RMS ratings of their speakers.

You will gain the full potential of your speakers as well as good headroom! Think about it.

??? So if I hook up a 1000w amp and only use 30w of it, I'm going to lose some transient response, because I'm not using the max amp/speaker power? Makes absolutely no sense.

If you play an amp/speaker combo until you reach an adequate volume for your tastes, and you've done so without clipping the amplifier, you are missing nothing.

If however, you cannot drive the speakers to a volume level that is loud enough for your taste, then you risk clipping the amplifier trying to get too much out of it. That is the only danger of sending less power than a speaker's RMS rating.

[cyberdraven]

Originally Posted by gymrat2005

??? So if I hook up a 1000w amp and only use 30w of it, I'm going to lose some transient response, because I'm not using the max amp/speaker power? Makes absolutely no sense.

If you play an amp/speaker combo until you reach an adequate volume for your tastes, and you've done so without clipping the amplifier, you are missing nothing.

Nope. Id use 220RMS amplifier to power a 150RMS speaker. If I had enough bread, Id use 300RMS ampligier for a 150RMS speaker. Dont know where did you get the 30w and 1000w idea.

[gymrat2005]

You said "any speaker will sound decent but will have problems handling transients, peaks and lows if underpowered by any amp" So according to your statement, if you do not listen to an amplifier wide open, you lose transient response. According to your statement, even if an amp is rated at 1 1/2 times the RMS of the speaker, if I chose to turn the volume knob down I will be losing transient response because I will be using well under the speaker's RMS rating.


That's like saying I have these tires that are Z rated tires. They can do 149MPH and stay within spec. But if I don't put them on a car that can do 149mph, then all of a sudden they won't perform as well and the handling will suffer. Those tires (speakers) will perform just as well at 80mph as they will at 149mph. It's the car's (amps) limits that come into question at those speeds, not the tire's (speakers).

[m3gunner]

Originally Posted by Problemhouston

I’m running Dyn 6 and tweet through the passive dyn crossover.

Really, now... I wonder where you got those?

Originally Posted by Problemhouston

My question is with the amp info I just gave about how many watts should I assume are getting to the 6's? I have them wired from the crossover at + - 0db for both the mid and tweet.

I don't know how to calculate crossover loss, so it's hard to tell how much is getting through, but the Loudspeaker Design Cookbook sez:

"One 60W and one 30W amplifier in a biamp setup will clip at about the same levels as one 175W amplifier with a passive crossover" (Page 192)

Based on that and using our calculator above:

10 * Log(175/60) = 4.6 dB loss

So... working backwards:

100 watts = 20 dB
Through the crossover = 20-4.6 = 15.4 dB

Dynaudio doesn't publish dB specs at their website:

Dynaudio - Authentic Fidelity

But if you check out the graph in the pdf, it shows that they're testing at 2.83 V and that at the 2.83 volt level, it puts out about 87 dB through most of the midrange.

Subtract 3 dB for 84 dB and add 15.4 to get 99.4 dB through the crossover for ONE DRIVER. Two drivers should give you around 102 dB or so.

I run a pair of MW150s and a pair of Dayton 1" tweets active with a JL Audio 300/4 and it's loud enough to chase me out of the car. Used to run the MW150s with MD100s on your crossover with a JL Audio 300/2 and it was about the same loudness (both could chase me out of the car...)

Rock on!