So if subs only need like 10 or 20 watts going through them...

[Howard]

Originally posted by: glen

Originally posted by: Howard

Originally posted by: glen

Originally posted by: Howard

Are you saying that goes for all systems with a flat on-axis frequency response?

All system far feild lsitening.
Far field is anything more than a foot, I think.
Car listenign is considered faar feild.

So many speakers (measured in an anechoic chamber) of high repute, then?

What are you asking?

That many speakers of high repute sound harsh because they measure flat in an anechoic chamber.

EDIT: You really think most tweeters need to be rolled off to sound good? Some of the best tweeters available for DIY use do measure flat up to at least 15kHz, with some reaching over 20kHz.

 

[glen]

Originally posted by: Howard

EDIT: You really think most tweeters need to be rolled off to sound good? Some of the best tweeters available for DIY use do measure flat up to at least 15kHz, with some reaching over 20kHz.

If you are playing pink noise through a system, and set it flat from 10hz to 20khz, it will make your ears bleed when you play normal music through it.

You are going to liek a 10db drop or so from 10hz to 20khz.

 

[davestar]

let's keep it simple and theoretical:

Sensitivity of an average 12" sub - 85 dB
SPL loss due to dispersion - 6 dB/(2 x distance)
Distance from trunk to driver - 2 meters
Desired SPL reference level at driver's seat - 100 dB

Ignoring "cabin gain":

For a 1 W amp:
85 dB (at 1 meter) - 3 dB (dispersion) = 82 dB

For a 2 W amp:
88 dB (at 1 meter) - 3 dB (dispersion) = 85 dB

.
.
.

For a 32 W amp:
100 dB (at 1 meter) - 3 dB (dispersion) = 97 dB

For a 64 W amp:
103 dB (at 1 meter) - 3 dB (dispersion) = 100 dB

Now we're getting to the SPL range in which glen is happy.

Siegfried Linkwitz (of Linkwitz-Riley fame) recommends that an amp have headroom of 20 SPL over your desired SPL reference level. This translates to 100 times the electrical power of the amp, or 6400 W in this case.

 

[Howard]

Originally posted by: glen

Originally posted by: Howard

EDIT: You really think most tweeters need to be rolled off to sound good? Some of the best tweeters available for DIY use do measure flat up to at least 15kHz, with some reaching over 20kHz.

If you are playing pink noise through a system, and set it flat from 10hz to 20khz, it will make your ears bleed when you play normal music through it.

You are going to liek a 10db drop or so from 10hz to 20khz.

Why would you care about how the system sounds when it plays pink noise?

http://www.zaphaudio.com/tweetermishmash/fr.html

Almost all of these tweeters are flat to 20kHz. Guess the manufacturers just cater to the ones who like harsh treble...

 

[Howard]

Originally posted by: davestar
let's keep it simple and theoretical:

Sensitivity of an average 12" sub - 85 dB
SPL loss due to dispersion - 3 dB/meter
Distance from trunk to driver - 2 meters
Desired SPL reference level at driver's seat - 100 dB

If by dispersion you mean distance, it's 6dB per doubling of distance.

The numbers don't change at 2 meters, but I thought I'd just clarify that.

 

[Rubycon]

Originally posted by: davestar

Siegfried Linkwitz (of Linkwitz-Riley fame) recommends that an amp have headroom of 20 SPL over your desired SPL reference level. This translates to 10 times the electrical power of the amp, or 640 W in this case.

20dB of headroom is 100x the power so your amp would have to have 6.4kW available which is rather tall for non pro applications!

 

[Howard]

Originally posted by: MS Dawn

Originally posted by: davestar

Siegfried Linkwitz (of Linkwitz-Riley fame) recommends that an amp have headroom of 20 SPL over your desired SPL reference level. This translates to 10 times the electrical power of the amp, or 640 W in this case.

20dB of headroom is 100x the power so your amp would have to have 6.4kW available which is rather tall for non pro applications!

It's sad that the majority of speakers sold today can't reproduce live listening levels (say 110dB transients at the listening position).

 

[glen]

Originally posted by: Howard
Why would you care about how the system sounds when it plays pink noise?

uh?
You don't, but if you want to measure, that is how you do it.

 

[davestar]

Originally posted by: MS Dawn

20dB of headroom is 100x the power so your amp would have to have 6.4kW available which is rather tall for non pro applications!

]Originally posted by: Howard

If by dispersion you mean distance, it's 6dB per doubling of distance.

The numbers don't change at 2 meters, but I thought I'd just clarify that.

righto, i mixed up some 10's and 20's there.

fortunately, with corrections, the point is only more obvious.

 

[Howard]

Originally posted by: glen

Originally posted by: Howard
Why would you care about how the system sounds when it plays pink noise?

uh?
You don't, but if you want to measure, that is how you do it.

Yeah, I suppose. But you still haven't convinced me that a flat response sounds harsh.

Check the response graphs I linked to in my previous post (3rd to last?).

 

[Aquila76]

OK, so I'm trying to see how to adjust a system for glenn's spec w/my Alpine CDA-9855's built-in EQ.
I would start off at the first bass point, leave it at 0dB, and every 3 octaves drop a dB? i.e.: 20Hz=0db, 60Hz=-1dB, 200Hz=-2dB, 600Hz=-3dB, 2kHz=-4dB, 6kHz=-5dB, etc?

Just so I don't seem like an uber-n00b here, I custom built my dual 12w6 enclosure and the door pods for my XR525 components. I'm running it all off of a V12 Alpine MRD-F752 5-channel amp (75x4 + 250x1 RMS).

Glenn, do you have a slope graph of your setup or something you could post, I'm just having a hard time picturing this for some reason. I blame the drinking and nachos over the weekend and the fact that I just woke up an hour or so ago.

 

[Accipiter22]

Originally posted by: glen
All this uproar started because I said that all you need for an 18" sub in a car is 20 watts.
I have emailed the audio techs at Adire audio for some real world data.
They have likely measured an 18"( or 15") sub in a car with 20 wats of power and can tell us exactly how loud it is.

whoah....there's enough on Adire's sight to keep me reading for a while

 

[Accipiter22]

Originally posted by: sharkeeper
A 1000W amp in a car can also serve another purpose. If it's truly designed to put out 1000W RMS continuous and your electrical system is up to par you can use it for a variety of things such as:

Making a pot of coffee
Powering a circular saw to cut up some plywood (but you should have done that BEFORE the storm cut the power dummy!)
Run a vacuum, etc.

How?

Just make a CD of a 60Hz sinewave (or 50Hz for those folks living across the pond) with a track 80 minutes long. Remove your speaker cable and grab an extension cord and lop off the plug. Wire this to your amp and plug in a power strip. Play your 60Hz sinus track and turn the gain up just to the onset of clipping. You may need to turn on your loads FIRST depending on the amp as some amps get unstable with no load.

I joked about this idea back in 1991 and then did it with a HiFonics Colossus Amp bridged (1800W x 1 at 4 ohms) We ran a milwaukee hole hawg (right angle drill) and drilled some holes to run wires through studs and ran a decent sized shop vac to clean up the mess. All on amp power. We tried Techmaster PEB as well but the drill did NOT like that very much and the brushes started sparking real bad so we stopped. Think about that the next time you need an inverter. Remember your mileage may vary and as a matter of fact you can blow your amp and alternator out so you may want to tread lightly at first.

Cheers!

really?





Ok, so from what I've gathered in this thread, not matter whos point I believe....I wasted quite a bit of money on the Infinity REF1211A....

 

[Accipiter22]

Originally posted by: davestar
let's keep it simple and theoretical:

Sensitivity of an average 12" sub - 85 dB
SPL loss due to dispersion - 6 dB/(2 x distance)
Distance from trunk to driver - 2 meters
Desired SPL reference level at driver's seat - 100 dB

Ignoring "cabin gain":

For a 1 W amp:
85 dB (at 1 meter) - 3 dB (dispersion) = 82 dB

For a 2 W amp:
88 dB (at 1 meter) - 3 dB (dispersion) = 85 dB

.
.
.

For a 32 W amp:
100 dB (at 1 meter) - 3 dB (dispersion) = 97 dB

For a 64 W amp:
103 dB (at 1 meter) - 3 dB (dispersion) = 100 dB

Now we're getting to the SPL range in which glen is happy.

Siegfried Linkwitz (of Linkwitz-Riley fame) recommends that an amp have headroom of 20 SPL over your desired SPL reference level. This translates to 100 times the electrical power of the amp, or 6400 W in this case.

ugh...I made that exact chart in excel earlier...I wish I could cancel this order

 

[davestar]

Originally posted by: Accipiter22

Originally posted by: davestar
let's keep it simple and theoretical:

Sensitivity of an average 12" sub - 85 dB
SPL loss due to dispersion - 6 dB/(2 x distance)
Distance from trunk to driver - 2 meters
Desired SPL reference level at driver's seat - 100 dB

Ignoring "cabin gain":

For a 1 W amp:
85 dB (at 1 meter) - 3 dB (dispersion) = 82 dB

For a 2 W amp:
88 dB (at 1 meter) - 3 dB (dispersion) = 85 dB

.
.
.

For a 32 W amp:
100 dB (at 1 meter) - 3 dB (dispersion) = 97 dB

For a 64 W amp:
103 dB (at 1 meter) - 3 dB (dispersion) = 100 dB

Now we're getting to the SPL range in which glen is happy.

Siegfried Linkwitz (of Linkwitz-Riley fame) recommends that an amp have headroom of 20 SPL over your desired SPL reference level. This translates to 100 times the electrical power of the amp, or 6400 W in this case.

ugh...I made that exact chart in excel earlier...I wish I could cancel this order

why do you say that? glen is basically the only person on here (or anywhere else, for that matter) that believes you can effectively drive a sub with very little power. for the example i just showed, Siegfried Linkwitz (a much more trusted audio authority than glen, sorry glen) a 6,400 W amp is recommended. you're fine

 

[Goosemaster]

My Subs run on jiggawatts

 

[Rubycon]

Originally posted by: Goosemaster
My Subs run on jiggawatts

Where do they come from? (the jiggawatts)

Do your magnatmotors have trinity stabilizers?

 

[Goosemaster]

Originally posted by: MS Dawn

Originally posted by: Goosemaster
My Subs run on jiggawatts

Where do they come from? (the jiggawatts)

Do your magnatmotors have trinity stabilizers?

5lb U-235-powered Ford Pinto whos alternator is hooked up to my state....

 

[Cattlegod]

Originally posted by: Accipiter22

Originally posted by: davestar
let's keep it simple and theoretical:

Sensitivity of an average 12" sub - 85 dB
SPL loss due to dispersion - 6 dB/(2 x distance)
Distance from trunk to driver - 2 meters
Desired SPL reference level at driver's seat - 100 dB

Ignoring "cabin gain":

For a 1 W amp:
85 dB (at 1 meter) - 3 dB (dispersion) = 82 dB

For a 2 W amp:
88 dB (at 1 meter) - 3 dB (dispersion) = 85 dB

.
.
.

For a 32 W amp:
100 dB (at 1 meter) - 3 dB (dispersion) = 97 dB

For a 64 W amp:
103 dB (at 1 meter) - 3 dB (dispersion) = 100 dB

Now we're getting to the SPL range in which glen is happy.

Siegfried Linkwitz (of Linkwitz-Riley fame) recommends that an amp have headroom of 20 SPL over your desired SPL reference level. This translates to 100 times the electrical power of the amp, or 6400 W in this case.

ugh...I made that exact chart in excel earlier...I wish I could cancel this order

not for low end, they never say what frequency that is measured at. with an A-Weighted scale if it was measured at 6khz, then you have to -50db for each one of those values at 20hz, -40db for frequencies at 30hz and so on.

 

[glen]

Originally posted by: Howard

Originally posted by: glen

Originally posted by: Howard
Why would you care about how the system sounds when it plays pink noise?

uh?
You don't, but if you want to measure, that is how you do it.

Yeah, I suppose. But you still haven't convinced me that a flat response sounds harsh.

Check the response graphs I linked to in my previous post (3rd to last?).

I don't know that I can.
You would have to hear it, or believe that I actually EQed my system flat, hated it, and then asked folks in the recordign industry, and they told me .

 

[gigapet]

its pretty simple really you don't need 1000 watts to power a 50 watt sub if you had a 800 watt sub then you may want a 1000 watt amp for it. not rocket science i don thtink

 

[glen]

Originally posted by: Aquila76
OK, so I'm trying to see how to adjust a system for glenn's spec w/my Alpine CDA-9855's built-in EQ.
I would start off at the first bass point, leave it at 0dB, and every 3 octaves drop a dB? i.e.: 20Hz=0db, 60Hz=-1dB, 200Hz=-2dB, 600Hz=-3dB, 2kHz=-4dB, 6kHz=-5dB, etc?

Just so I don't seem like an uber-n00b here, I custom built my dual 12w6 enclosure and the door pods for my XR525 components. I'm running it all off of a V12 Alpine MRD-F752 5-channel amp (75x4 + 250x1 RMS).

Glenn, do you have a slope graph of your setup or something you could post, I'm just having a hard time picturing this for some reason. I blame the drinking and nachos over the weekend and the fact that I just woke up an hour or so ago.

I think you are misunderstandign something.
You have to have a device with a microphone that listens to your system before you can know how to EQ it.

This is an overly simple guide from eHow

How to Use a Real-Time Analyzer to Tune a Car Audio System
If you are a fanatic about the sound quality of your car's stereo system, you will want to use a real-time analyzer (RTA). It can monitor each frequency of music across the spectrum from 20 Hertz (Hz) to 20,000 Hz and discover peaks and valleys in the frequency range. Once you know where the peaks and valleys are, you can make adjustments to eliminate them, ensuring a smooth transition between frequencies.

Preparations

Steps:
1. Get a CD that plays pink noise. Pink noise is all frequencies of the spectrum generated at the same level. It sounds like static when you play it.

2. Make sure that the RTA's battery is properly charged. Most devices include a readout that tells you if the battery is charged or needs charging.

3. Make certain that you have a good stand for the RTA's microphone. The microphone will be attached to the stand and the assembly will be put on the driver's seat in the car. The stand needs to have a base securely weighted so that it will stay in one position without moving.

4. Look around the vehicle and take out all items that are not a part of the interior of the car. Remove briefcases, old soda cans, everything; sound bounces off some surfaces and is absorbed by others, and these items influence the sound that is measured by the RTA.


Tips:
You can get a CD with pink noise from any association that sponsors Sound Off contests.


The Test

Steps:
1. Set the microphone stand on the driver's seat, so that the microphone is 26 inches above the seat - roughly the position of the driver's ears.

2. Face the microphone toward the front of the dash.

3. Plug the microphone into the RTA.

4. Play the CD with pink noise through your sound system. Set the CD player to repeat the track.

5. Make sure that all the doors are closed.

6. Take the meter and stand outside the car when you run the test.

7. Put the RTA in the test mode. A graph will appear on its display. This graph is a visual reading of the sound of your system from 20 Hz to 20,000 Hz. The dots beside the bars that define the frequency display a sound level of either 1/10 or 3 dB. This helps you determine how much more sound level one frequency has over another. The RTA will print out a graph.

8. Use the graph to adjust your equalizer to eliminate the peaks and valleys and achieve a smooth transition from frequency to frequency.

 

[KoolAidKid]

Originally posted by: glen

Originally posted by: Cattlegod
he is full of crap. a 20hz signal at 80db would be hardly even loud enough to hear. you need a LOT of power to put out the low frequencies at a high enough SPL to hear.

my system was putting out 140db at 33 hz with the windows up, and 147db at 33 hz with the windows down. It ended up taking 3rd place in the SPL drag race I entered it in.

You can't hear 80db?
You don't know what you are talking about.

That would be audible in any normal enviroment, and percieved as loud in a sound proof room. Loud car stereo systems are 110db. FOr lsitening, I can't see the need to produce mroe than 110 db.

A 20 Hz tone at 80 dB SPL is equivalent in loudness to a 1000 Hz tone at 10 dB SPL.

Also, I have never understood those who say that a flat frequency response sounds harsh. If a flat response sounds harsh to you than real-world sounds should as well.

When a speaker's response isn't flat it introduces artifacts into the output that are not intended to be there. Why is this considered desireable? I guess if you are used to listening to distorted output then perhaps I could understand the preference.

 

[glen]

Originally posted by: KoolAidKid


A 20 Hz tone at 80 dB SPL is equivalent in loudness to a 1000 Hz tone at 10 dB SPL.

Also, I have never understood those who say that a flat frequency response sounds harsh. If a flat response sounds harsh to you than real-world sounds should as well.

When a speaker's response isn't flat it introduces artifacts into the output that are not intended to be there. Why is this considered desireable? I guess if you are used to listening to distorted output then perhaps I could understand the preference.

No.

Why do I spend so much effort trying to help folks?
No good deed goes un punished.
Anyway, CD's are not intended to be played back on systems that measuer flat with pink noise and an RTA.
Counter intuative - yes, but true.
But, this whole tread is pointless - no one arguing with me owns and uses test equiptment.
They are jsut cutting and pasting pieces of information they truely don't understand.

 

[KoolAidKid]

Originally posted by: glen

Originally posted by: KoolAidKid


A 20 Hz tone at 80 dB SPL is equivalent in loudness to a 1000 Hz tone at 10 dB SPL.

Also, I have never understood those who say that a flat frequency response sounds harsh. If a flat response sounds harsh to you than real-world sounds should as well.

When a speaker's response isn't flat it introduces artifacts into the output that are not intended to be there. Why is this considered desireable? I guess if you are used to listening to distorted output then perhaps I could understand the preference.

No.

Why do I spend so much effort trying to help folks?
No good deed goes un punished.
Anyway, CD's are not intended to be played back on systems that measuer flat with pink noise and an RTA.
Counter intuative - yes, but true.
But, this whole tread is pointless - no one arguing with me owns and uses test equiptment.
They are jsut cutting and pasting pieces of information they truely don't understand.

You are incorrect. I do research in psychoacoustics, and in that capacity I often measure the frequency magnitude and phase response of transducers using equipment a lot more sophisticated than a RTA. I have designed digital filters that perfectly flatten the magnitude response and linearize the phase response of speakers, and let me tell you, a properly equalized speaker sounds fantastic IMO.

As to whether CDs are mixed assuming a non-flat speaker, I couldn't tell you. Do you have a good source for this statement? I would be interested in reading about it.