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Old 3rd February 2011, 08:26 PM   #331
jbell is offline jbell  United States
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Quote:
Originally Posted by soho54 View Post
I never said it was always expected.

Have I seen it before in a horn? Yes.
wow... this is a first for me.

When you said this awhile back, I blew it off as crazy talk... but now you've got me second guessing. Hornresp says it should be a 24db/oct fall from 60hz on down. This clearly shows it is about a 12db/oct drop from 60-40hz, and then a 24db/oct drop from there.

And you are really saying that this could be caused from 'better loading' at large signal vs small signal???

And the consequence of saying that: Part of the reason that Tom's charts on DSL beat the pants off of the competition is that he tests at 28v10m... and if only the competition knew that.... then they could compete. (not being serious here....)

Click the image to open in full size.

Last edited by jbell; 3rd February 2011 at 08:31 PM.
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Old 3rd February 2011, 10:28 PM   #332
soho54 is offline soho54  United States
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I think "different loading" would be a more correct way to put it here.

"Better" was a bad choice on my part. I said, "You are seeing an decrease in rolloff due to the greater pressures in the horn that are loading it better down low." I was speaking about the straight FR to FR profile comparison there. What I meant was that the loading differences make it graph better here.
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Old 3rd February 2011, 11:44 PM   #333
jbell is offline jbell  United States
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Quote:
Originally Posted by soho54 View Post
I think "different loading" would be a more correct way to put it here.

"Better" was a bad choice on my part. I said, "You are seeing an decrease in rolloff due to the greater pressures in the horn that are loading it better down low." I was speaking about the straight FR to FR profile comparison there. What I meant was that the loading differences make it graph better here.
different, better, whatever... I've not met a dj yet who runs his subs at 2.83 volts....

Still unbelievable to me that at volume would be anything other than worse compared to 2.83 volts.
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Old 4th February 2011, 12:18 AM   #334
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Quote:
Originally Posted by jbell View Post
different, better, whatever... I've not met a dj yet who runs his subs at 2.83 volts....

Still unbelievable to me that at volume would be anything other than worse compared to 2.83 volts.
Jbell,

Having done quite a bit of testing, I have found no appreciable difference between one watt and 100 watt tests of subs unless the speaker is not capable of 100 watts without exceeding Xmax, or is leaky or not well braced.

Testing with the microphone on the ground at 10 meters is advisable for subs, especially large sized subs or arrays, where directivity can make one meter tests not representative of actual response (other than at one meter ;^).

The sine wave testing measurements of your one sheet sub are encouraging, have you checked it against any other “known quantities” ?
A comparison with the same speaker in a sealed or ported box would be a good “reality check”.
The Smaart RTA chart you showed shows 40Hz more than 6 dB down from the 63-125 range, if 40hz is actually 98.5 dB, and 100hz at 104.5, that is a quite impressive 5 dB gain in sensitivity over a similar sized Fb 44 Hz box.

That said, the ported box can take 400 watts without exceeding Xmax (9.6mm a bit more than 3/4 inch peak to peak), what is the excursion like with the tapped horn at 400 watts (58 volts)?

The 3015LF in a ported box can do 125 dB with 400 watts, what is the max you have read with the tapped horn in the 50-100 Hz range?

Art

Last edited by weltersys; 4th February 2011 at 12:22 AM.
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Old 4th February 2011, 03:01 AM   #335
Djim is offline Djim  Netherlands
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Not just horns can give better results with 100w/1m. Most PA loudspeaker manufactures give SPL responses of 1w/1m because this was and still is the AES standard for measuring loudspeakers under controlled circumstances. And it works in favour for some to produce 'better' results. Manufactures like RCF for instance provide charts with -10dB Pmax SPL responses to manufacturers if requested. It is not unfamiliar those readings give better results. So it’s not just a horn thingy! They suppose to produce the best results at -10dB Pmax, don’t they?!


That’s the reason why serious manufactures of PA loudspeakers prefer to look at a more real world circumstances at 100w/10m for instance. Or even more fair in my view: -10dB Pmax at 10m (most time the point where serious power compression starts to take place). Then I would like to see the competition between brands like RCF, 18Sound, B&C, Beyma, and others like eminence for instance. We could immediately see who’s fair and who isn’t. power compression would become a real deal with those measurements! Although maybe some drivers would perhaps die before giving those results... But hey, since people demand those 1w/1m charts why not giving them and come up with some crazy pwr ratings, non realistic Xmax numbres, and who cares about power compression and get away with it.

So Jbell, I get it why you prefer to measure at 100w/10m and hope to see more of those charts...

Click the image to open in full size.

Last edited by Djim; 4th February 2011 at 03:23 AM.
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Old 4th February 2011, 05:24 AM   #336
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Quote:
Originally Posted by Djim View Post

So Jbell, I get it why you prefer to measure at 100w/10m and hope to see more of those charts...

Click the image to open in full size.

+1

Response comparisons at maximum safe output would be very interesting! Then we could decide even better which speaker and cabinet to use for which purpose.
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Old 4th February 2011, 06:51 PM   #337
jbell is offline jbell  United States
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Ok... since there has been much talk spent on 28v vs 2.83v measurements.... And I'm a fan of 'There is no substitute for doing...' I went and did something a bit crazy today.

The crown was set for 40-300hz. (and yes, even a butterworth 48db/oct at 40hz cuts a couple db at the high pass freq.)

The pictures speak for themselves.
Attached Images
File Type: jpg Picture 084a.JPG (81.0 KB, 464 views)
File Type: jpg Picture 082a.JPG (199.1 KB, 429 views)
File Type: jpg ss15-283v.JPG (148.8 KB, 187 views)

Last edited by jbell; 4th February 2011 at 06:57 PM.
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Old 4th February 2011, 07:22 PM   #338
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Quote:
Originally Posted by jbell View Post
Ok... since there has been much talk spent on 28v vs 2.83v measurements.... And I'm a fan of 'There is no substitute for doing...' I went and did something a bit crazy today.

The crown was set for 40-300hz. (and yes, even a butterworth 48db/oct at 40hz cuts a couple db at the high pass freq.)

The pictures speak for themselves.
Hmm... does that meter read true RMS?
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Old 4th February 2011, 07:28 PM   #339
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Quote:
Originally Posted by jbell View Post
Ok... since there has been much talk spent on 28v vs 2.83v measurements.... And I'm a fan of 'There is no substitute for doing...' I went and did something a bit crazy today.

The crown was set for 40-300hz. (and yes, even a butterworth 48db/oct at 40hz cuts a couple db at the high pass freq.)

The pictures speak for themselves.
Not sure what the pictures are saying, other than the 3 dB down point with the 40Hz filter is now about 55 Hz, and the 10dB down point 40 Hz.

Using magnitude response at 32K FFT would show the narrow peaks and valleys that can hide in the grass with the RTA, and allow easy comparisons on one screen.

Does the response look different at 1 watt one meter compared to 100 at 10 meters?
What distance is this test from the nearest walls?
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File Type: png Magnitude Vs RTA.png (118.2 KB, 167 views)
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Old 4th February 2011, 07:31 PM   #340
jbell is offline jbell  United States
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Quote:
Originally Posted by Brian Steele View Post
Hmm... does that meter read true RMS?
nope... so you want to take that reading and multiply by .707?

That'll make the numbers look even better....

That was at the end of my sidewalk... about 20' from the house, nothing in front for about a half mile. You can see the toyota off to one side, that's about it.
The pic a few posts back (#331) was 28v10m, I don't see much difference to what I did today.

excuse the 'non-scientific' measurement that was obviously rushed.... it was cold, and snowy, but at least no wind.

Last edited by jbell; 4th February 2011 at 07:39 PM.
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