[policy]

I have a dual channel amp Im currently running in mono mode (not bridged) because of some cable issues Im having, so Im powering my sub with 400w right now. When I bridge it to mono, the figure will jump to 1140w, which sounds like a huge deal to me. The guy at the place I bought the amp from is claiming that I won't notice a difference at triple the power though, and that at best all I can hope for is a 3-4db difference.


Unfortunately because the sub isn't DIY, this is all the info I have on it: (Adire Sadhara):


Driver Single 12" XBL2 enabled extreme-displacement driver

Alignment Low Q ported cabinet tuned to 20 Hz

Power Recommended for power amps up to 800W

Bandwidth In-Room +0/-3 dB from 17 Hz to 500 Hz

Impedance 4 Ohms

Anechoic Output > 105 dB SPL @ 20 Hz

> 110 dB SPL @ 25 Hz

Peak output 118 dB SPL above 40 Hz

In-Room Output > 120 dB SPL @ 20 Hz

> 123 dB SPL @ 25 Hz

Peak output 130 dB SPL above 40 Hz

(based on an IEC standard room, subwoofer located in front corner)


So, the question is:


Is he lying? Is it not worth the $70 custom cable to run the amp bridged into mono? Will I at BEST gain 3-4db? Because if that's true I'm REALLY dissapointed in the output of the sub. It's blown nothing off the shelf. Yes it vibrates things in the house, but for the size of the sub (100lbs, and about 4 feet tall) I was expecting organ damage :-/

 

[spider_bill_2003]

First I would measure the sound output at 1 meter distance with a "boom" track from a DD or DTS movie. Use a Radio Shack sound level meter - digital version set to max and time record.


Then compare that to the speakers specifications.


You have not said how "loud" the speaker plays right now, nor how loud the system plays with your volume settings.


The rule of thumb is if you double the amplifier power, you can only get another 3 DBspl out of the speaker.


--Bill

 

[Larry Fine]

Pol, what will you be using to invert the signal phase to one of the amp channels?

 

[policy]

Larry-


Crown claims that if you switch the 2 and 3 pins on the XLR cable that it will reverse the polarity, but when I did that, it had no effect. So basically I have no idea how I'm going to do it, other than hope that the store I bought the amp from can work a cable up for me.


But you switch pins in the 1st channels XLR and it reverses polarity down into the one sub cable.

Quote:

The rule of thumb is if you double the amplifier power, you can only get another 3 DBspl out of the speaker.

Why would anyone have anything more than a 500w amp then?

 

[Version]

Everytime you double your power you get a 3 db boost.


50 to 100 to 200 to 400 to 800 - 3 db each time.

 

[spider_bill_2003]

Quote:

Originally posted by policy Why would anyone have anything more than a 500w amp then?

Ego?


Lack of knowledge?


They need 3 more db because they have a very large room?


You can pick up 5 DB extra by running your mains as Large (if the mains are large speakers) along with a dedicated subwoofer. The "audiophile" and "equipment salesman group" group does not like that setup however!


Your speaker seems to indicate that the "Power Recommended for power amps up to 800W". 400 watts should be fine!



"It's blown nothing off the shelf. Yes it vibrates things in the house, but for the size of the sub (100lbs, and about 4 feet tall) I was expecting organ damage"



You are expecting too much. If you want that, use a real explosive device!



--Bill

 

[policy]

I don't have a large room. It's a small room.


Im running it at about 400w right now, so saying that Im getting about [email protected], will I then get [email protected] by going to 1140w, or would I need to go to 1600w to realize the 6db boost?

 

[tubeguy44]

Quote:

Why would anyone have anything more than a 500w amp then?

to have a great sub with low extension and high spl.....


the sunfire sub for example....
Quote:

2700-watt amp featuring patented Tracking Downconverter power supply Frequency response: 16 Hz to 100 Hz (+0, -3 dB) Measurement microphone and automatic internal contour compensation keeps it that way Greater than 116 dB peak SPL with room gain

http://www.sunfire.com/TrueSubwooferEQSigPR.htm



cheers!

 

[Version]

Quote:

Im running it at about 400w right now, so saying that Im getting about [email protected] ... would I need to go to 1600w to realize the 6db boost?

Theoretically, yes.


94db at 100w

97db at 200w


100db at 400w

103db at 800w

106db at 1600w


109db at 3200w

112db at 6400w


You can see that it takes quite a bit of power to ramp up volumes on an exponential curve.

 

[Ovation]

It works much like a car. The formula isn't exactly the same, I think, but it takes quite a bit of extra horsepower to squeeze a few extra mph out at top speed. For audio, it's the same. Another reason to have extra power (though only you can determine how much extra you need) is to have reserves, for those times when the soundtrack demands extra power. You don't want to already be at your power limit when that depth charge explodes in U-571. Just like you'd appreciate the extra horsepower when passing that 18-wheeler uphill on a two lane road.