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I don't think it is correct to look at sensitivity numbers in this fashion.  Horn, direct radiator, ect, a given speaker can only get so loud if you can reach max power.  Sensitivity is a measure of how easy the speaker can be driven.  If there is enough power and a driver can reach the max spl, that is all that is required whether a horn or direct radiator.  It just comes down to  physics.   A La Scala can hit 120 db's but, at what frequency.

 

A given driver only has so much Xmax and Xmech, this is physics, and applies to horns, direct radiator, ect.  As for input voltage, it should be lower than the output voltage.  PEQ boosting or lowering can effect what the amp is doing.  Thinking of an amp as a two stage device, the input stage and output stage is the way I look at it.  The input stage is coming from the avr/ preamp, ect.  The output stage is the amps power capacity.  This stage is less likely to be involved with clipping compared to the input stage.  The gain knob is just something to help regulate the input stage so that the amp puts out X amount of given power.

 

Even considering max spl of a speaker is not very realistic: most sane people will not subject their ears to 121 db of spl for long.  Or, this hobby will be on their short list.  I keep ear protection in the room with my system; how carzy is that, lol.  Box design and material can also shift the senitivity/need watts to reach X spl.

Edited by derrickdj1
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when does the spud/clone run out - ?

 

I guess I don't understand that question.

 

The spud never seems to run out.  Then again, when I turn it off and run no sub, it doesn't seem to make that much of a difference. 

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This  brings up voltage gain since most people using the Spud or other passive subwoofer are driving them with external amps like the Crown, I Nuke, ect. Preamp Input and the output stage have to be matched.  Some people get a powerful sub and are immediately disappointed because they were expecting a huge increase in output and headroom.

 

There is a difference between using balanced vs unbalanced cables between the preamp/amp.  Voltage gain is how much or to what the degree the preamp signal is amplified by the amp.  THX recommends a voltage gain of 29 db.  Unbalance systems can usually do this without problems. Balanced systems do around 23 db. This means that with a balance system the Vrms has to be higher. 

 

 

If the preamp can't deliver enough input voltage for the desired output, then the preamp will clip.  This clipped wave can have negative consequences on the amp and speaker.  Even if the amp is capable of some high watts like 3-4000 watt the voltage from the preamp may be only able to support 500 watt.  This is overly simplified but, hopefully easy to understand.

Edited by derrickdj1
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Trying to figure out when a sub will run out of steam is difficult.  Movies and music contain many layers of different frequencies all being amplified at the same time and of varying amplitude.  It sounds like the Spud is a great fit for you(The Dude).

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The question was what how many volts other sub users needed to get 100 dB at 22 Hz

 

Not an f20 or a single driver unit. But my spud clone single cab running dual 8" takes about 9 volts to push 22 hz from youtube to 100 db.  That is about 12' away from the measurement mic.

 

 

Well I googled tang 8 in drivers  -  84dB sensitivity + 2 = 87 dB     so

 

Dude  :mellow:   you have LaScala  104dBb+ 2 = 107 dB,    when does the spud/clone run out    -  ?

 

Real quick. 84db sensitivity is based on the 440 cm3 SD of the pair of Tangs, you should look at the fact that the Spud is not only a horn loaded and sealed sub with a 1570 cm3 mouth, it is also a tapped horn design which is another +3db. The total increase in output would be:

 

84 + 3 = 87

1570 / 440 = 3.57

3.57 * 3 = 10.71

87 + 10.71 = 97.71 db efficiency

97.71 db plus 1/2 space gain = 100.71 db at mouth

 

The measured 100db of 22Hz at 12' (3.66m) using inverse square calculations means at 1 meter he would be 111db at 9 volts.

 

Reverse calculations on 9 volts (20.25 watts at 4 ohms) to get 111 db at 1 meter would calculate backwards to 2 volts (1 watt at 4 ohms) to about 100db.

 

So you see, two 8" Tangs with an 84db efficiency in a tapped horn with a 1570cm3 mouth measured in half space is 100db efficient, and is verified by the 12' measurement of 22Hz.  This is less efficient than a LaScala, but the Spud can take over 350watts before reaching excursion at 22Hz sine. That means it can output 2db more than the max a LaScala can.

 

The Spud can keep up with LaScalas unless they are stacked, and even then, it is only 1db short.

Edited by mustang guy
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The question was what how many volts other sub users needed to get 100 dB at 22 Hz

 

Not an f20 or a single driver unit. But my spud clone single cab running dual 8" takes about 9 volts to push 22 hz from youtube to 100 db.  That is about 12' away from the measurement mic.

 

 

Well I googled tang 8 in drivers  -  84dB sensitivity + 2 = 87 dB     so

 

Dude  :mellow:   you have LaScala  104dBb+ 2 = 107 dB,    when does the spud/clone run out    -  ?

 

Real quick. 84db sensitivity is based on the 440 cm3 SD of the pair of Tangs, you should look at the fact that the Spud is not only a horn loaded and sealed sub with a 1570 cm3 mouth, it is also a tapped horn design which is another +3db. The total increase in output would be:

 

84 + 3 = 87

1570 / 440 = 3.57

3.57 * 3 = 10.71

87 + 10.71 = 97.71 db efficiency

97.71 db plus 1/2 space gain = 100.71 db at mouth

 

The measured 100db of 22Hz at 12' (3.66m) using inverse square calculations means at 1 meter he would be 111db at 9 volts.

 

Reverse calculations on 9 volts (20.25 watts at 4 ohms) to get 111 db at 1 meter would calculate backwards to 2 volts (1 watt at 4 ohms) to about 100db.

 

So you see, two 8" Tangs with an 84db efficiency in a tapped horn with a 1570cm3 mouth measured in half space is 100db efficient, and is verified by the 12' measurement of 22Hz.  This is less efficient than a LaScala, but the Spud can take over 350watts before reaching excursion at 22Hz sine. That means it can output 2db more than the max a LaScala can.

 

The Spud can keep up with LaScalas unless they are stacked, and even then, it is only 1db short.

 

 

That was a mouthful, lol.  Nice! :):emotion-22:  Well, it is weekend and evening is perfect for a cold one.

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So you see, two 8" Tangs with an 84db efficiency in a tapped horn with a 1570cm3 mouth measured in half space is 100db efficient

 

TH Spud   specs from Danley Sound Labs

 

Sensitivity @
1M .............................................................................................. 94 dBSPL
.........................
(Referenced to 2.83V @1M ½ space, measured as 28.3V @ 10M
 
 
The 2  8 inch 84dB drivers output apparently  get a 7 dB increase from the tapped horn enclosure. 

 

Thanks for the link. I grabbed a piece of that graph. The Danley drivers have a higher excursion and more mass, so they are less efficient. They, however, are rated at 800 watts. I stand by my prediction of 100db for the Spud clone.   :)

 

IRfOgvi.png

 

edit: I would believe the overall efficiency may be less than 100 since it takes an average, and it looks like the tune of the enclosure seems to favor 22 Hz. I will say the efficiency might be 97db. I am simply taking the difference in the graph above at 22Hz at 97 db and the measured 22Hz at 100db. That is 3 less. They have efficiency rating of 94, so add 3 and you have 97. The Spud clone with that driver is 97db efficient and does 22Hz at 100db with a watt.

 

If the drivers are considered Isobaric in that sub, then my very first +3db for the second driver is where I made the mistake. I didn't research, but assumed they were not.

 

The Tang drivers paired up would be 300 RMS - 600 MAX:

Pl5fInj.png

 

The drivers in the Danley are 400 RMS - 800 MAX. They have higher excursion and more mass. I believe 126 db peak is a stretch by a couple db... 

LQjqrDS.png

Edited by mustang guy
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Even considering max spl of a speaker is not very realistic: most sane people will not subject their ears to 121 db of spl for long.

 

About ten years ago or better I was invited to a friends place from FAFB who loves audio, especially subwoofers.

He lived at his folks at the time, in a trailerhouse on the property. I was invited for subwoofer blast day...

 

He had a pair of Adire Tumults in about six foot internal sized cabinets, tuned to 16Hz. Each subwoofer had a Peavey 2000 watt pro-sound amplifier. I think he was using a Outlaw Audio subwoofer active crossover, with gain control and other capabilities.

 

The guy was into car stereo as well, and another friend brought a Term-Lab SPL meter. It's a competition SPL meter for car stereo...it only triggers at 120 decibels.

From the listening position at 12 feet, he pulled 122 decibels at 20Hz, and around 125-126 decibels at 25Hz. This is a continuous sine wave burp, with those poor Peaveys at full clip.

Six inches from the port of one subwoofer, was 130 decibels at 25Hz.

 

It's like being in a thick force field. Cleans everything off the walls, counters, cabinets. The window behind the listening position had to be buzzing at 110 decibels.

We went outside and watched the sheetmetal behind the stereo of the trailer flop back and forth about six inches.

 

Not realistic indeed....stupid loud fun, however. :)>

 

The same day another guy was there with a Dodge Dakota with a wall using six 15" Adire Tempests, tuned to 37Hz powered with a 1000 or 2000 watt Mmatts amplifier. That beast would burp 150 decibels...I made the mistake of riding in the back of that Dakota. The most unrealistic car stereo I had ever listened to at normal levels. 37 hertz...a massive hole...then tweeters...but it wasn't made for SQ, it was made for SPL.

 

post-4542-0-85520000-1464392015_thumb.jp

Edited by mike stehr
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