# Low power 350 watts high SPL



## 8675309 (Jan 8, 2007)

So I have some things going on at the moment and I am trying to confirm many years of enclosure designs. 

This is what I have in mind. I am not going into detail because there is more to this. 

Brand A 5 channel amp with a mono section of 350 @ 2 ohms

Brand B woofers 4 of them with an RMS of 400 together and a wired sens of 98 DB at 1 watt. Huge high gain ported box for spl. 

Again no big details but I am going for very simple SQL type setup with low power. LOL

Should I go for single woofer or multiple with high sens in a high gain Ported box to get the most??

This is directed at a couple of folks.


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## DS-21 (Apr 16, 2005)

It doesn't matter. Sensitivity at the low end is determined overwhelmingly by box size. So if you want high sensitivity down low, use a big box.

Now, the multiple woofer setup might get you more in the 50-200Hz octave pair.


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## m3gunner (Aug 6, 2008)

The short version is that a watt is a watt.

If you're starting with 98 dB @ 1 watt, you'll get the following:

10 watts: 108 dB
100 watts: 118 dB
350 watts: ~123.8 dB

Of course, this is not taking into effect any gain from the car and the measurement is based on the same distance as the original reading.

If you do a BB4 alignment, you can extract a few more dB (2-3 dB) from the driver above the tuning frequency... at the cost of a reduction in output below the tuning frequency.

Illustration here: Speaker Workshop Project Subwoofer Enclosure (A)


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## DS-21 (Apr 16, 2005)

Neither system, unless the box is like 20" x 70" x 70", is going to be 98dB/w/m down low in free space.


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## Sulley (Dec 8, 2008)

I've done 129db with music on a cheap Scosche SPL meter (who knows how accurate it is). Two 12" Rockford P2's bridged of the rear channels of a Hifonics amp for a claimed 340watts. Ported box almost 4ft^3 tuned to about 34hz in a Pathfinder.

I don't know how accurate that meter is but i know it gets pretty loud. It sounded like ass that loud though...just saying.


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## 8675309 (Jan 8, 2007)

This is what I am thinking. If I did a single 15 in a big ported box and that 15 has a rated sens of 88db and will handle 350 or more. Compared to 4 - 15's with a combined sens of 98db and has an RMS of 400 in a big ported box. What I am thinking and how it compares to other single driver designs I am working on, the 4-15's have a higher output based on the design output. The thing I am looking at is will the cheaper 4 - 15's create more output than the single better 15 with the same amount of power. In theory the 4 should do this but in SPL this may not be the case. 

For example if I did a single Diamond D315 compared to say 4 - Dayton Classic 15's. "Just an example"

Something else to keep in mind, I am trying to keep the total cost of the woofers at less than $200

So make up for the cheaper price with higher sens more woofers and a big ported box or get a single 15 in that price range that may not have the higher sens but can handle more power.

Based on 15 years of using bass box and designing with it, 4 - dayton classic 15's in a big ported box seems to be the best bet with the amount of power I have. "for example"

I am also looking at a design that would use 8 - 10's that would work out well with the amount of power I have.



DS-21 said:


> Neither system, unless the box is like 20" x 70" x 70", is going to be 98dB/w/m down low in free space.


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## TREETOP (Feb 11, 2009)

The 4 cheaper 15s would have both the advantage of more cone area _and_ higher sensitivity. While they'd _each_ be getting less power than the single 15 option, I believe you'd get a LOT more output from them with the same total power.


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## 2500hd (Aug 22, 2009)

What about 3 eminence alpha 15a? $180 for 103db @ 1w/1m, but it would have to be IB or OB...


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## Volenti (Feb 17, 2010)

TREETOP said:


> The 4 cheaper 15s would have both the advantage of more cone area _and_ higher sensitivity. While they'd _each_ be getting less power than the single 15 option, I believe you'd get a LOT more output from them with the same total power.


Yes, this. Of course you pay for it with a massively larger enclosure, but if you have the room, you have the boom


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## Oliver (Jun 25, 2007)

DS-21 said:


> box is like *20" x 70" x 70".*





stockley.rod said:


> I've done *129db*... It sounded like ass that loud though...just saying.


With a *humongous box* you will get close to 125 - 130 dB's on a *Term Lab*microphone.


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## 8675309 (Jan 8, 2007)

I have found some 10's that claim to have a 109 db sens. If I can verify this and find the specs I may look into 8 of these.

What ever I do I will have to keep the load at 2 ohms so I can get the most power from the amp.


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## DS-21 (Apr 16, 2005)

8675309 said:


> I have found some 10's that claim to have a 109 db sens. If I can verify this and find the specs I may look into 8 of these.


They might....at 1kHz, with rapidly falling response below like 400Hz.

But in the low end, sensitivity of the driver just isn't relevant. It's all about box volume. So focusing on the sensitivity ratings of subwoofer drivers is beyond pointless.


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## 8675309 (Jan 8, 2007)

Going with a single 15 and about 700 RMS in a high gain box. 




DS-21 said:


> They might....at 1kHz, with rapidly falling response below like 400Hz.
> 
> But in the low end, sensitivity of the driver just isn't relevant. It's all about box volume. So focusing on the sensitivity ratings of subwoofer drivers is beyond pointless.


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## DS-21 (Apr 16, 2005)

What's a "high gain box"?


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## cubdenno (Nov 10, 2007)

Are you going for audible loudness or SPL?
Ever been to a SPL contest where a guy who is louder externally than the SPL "winner"?

Here is a quote from another forum. The guy's name is Pete Kulicki. Does some fantastic box designs.



> One of the biggest problems on car audio forums is that people try to apply the dynamics from one environment within another. Classical horn theory, transfer theory, quarter-wave theory, standing wave theory, etc... I can see how this could happen, as just about every book and web site out there that tackles the dynamics of sound is written from a home audio / infinite environment perspective. Exporting these principles into contained environments (i.e. vehicle cabins) is kind of like attempting to build a flying machine on Mars by reading about the design principles behind the flying machines on Earth.
> 
> What I'd like to attempt here is to illustrate the problem with the theory that doubling your power results in a 3dB gain. This theory was never intended for low efficiency drivers, high gain environments, and high current applications. As most other theories mentioned above, this one has it's roots elsewhere. Think of infinite environment low current sound reproduction systems and 1 meter on-axis benchmarks where the first watt is always the most important watt... you may begin to see why this theory falls apart when applied to car audio.
> 
> ...


There is a bunch more that I have gathered from him for SPL such as more flex =less SPL. You are after pressure so anything that reduces pressure is bad.


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## 8675309 (Jan 8, 2007)

Bout 8 cube with a 16 db bump around 50, that is based on BBpro. The design will use a changeable port so I can play with tune to get the most at cabin res. I am doing this type of box for one reason and one reason only. At this point I am back into an area I understand on design. Using multiple woofers with low power was creating a design problem for me. I am not looking to break any records, I am only looking to add points to my score sheet.


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