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Multi-Way Conventional loudspeakers with crossovers

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Old 15th December 2001, 08:18 AM   #11
pkgum is offline pkgum  Australia
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According to Unibox and IspCAD Lite the sensitivity calculated is 87.6Db 1W 1M........not the claimed 91Db 1W 1M in the blueprint website

So, can you think of any reasons why it isn't falling 12Db/octave?
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Old 15th December 2001, 03:27 PM   #12
Wizard of Kelts
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Gum:

If the sensitivity is in fact 87.6 instead of 91 dB, then we have gone a long way toward solving the discrepancy. That is a difference of 3.4 dB, and the figures I calculated are about 4 dB more than the WinISD figures.

As for the rolloff, the speaker/box combination has a low Q of 0.5. This configuration is getting to be increasingly popular. Before, most sealed manufacturers aimed for a Q of 1 or of .7.
The higher the Q, the steeper the rolloff after you hit resonance. F3 doesn't have anything to do with it.

Since 0.5 is a low Q for a speaker/box combination, the bass rolloff will be more gradual.

Try running the program for a sealed volume of 15 liters. That should give you a final speaker/box Q, (otherwise known as Qtc) of about 1. The resonance frequency will be about 67 Hz. See what the rolloff characteristics look like then. It should be about 12 dB/octave after you hit 67 Hz.

One important thing to re-emphasize is that in the box of 120 liters, your SPL will be limited not by the excursion of the cone, but by the sensitivity of the 1503 and the fact that you can put "only" 1,000 Watts through it. All the way down to 15 Hz, the 1503 has "extra excursion" to move after the 1,000 Watts have been pumped through it.
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Old 15th December 2001, 03:43 PM   #13
ucla88 is offline ucla88  Tahiti
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actually, you're both right about the roll off. at frequencies around f3, the slope of the rolloff depends highly on the Q. as you move below f3, no matter what Q, eventually both curves drop off at the same 12db/octave for a sealed box.

my kingdom for a graph.
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Old 17th December 2001, 12:38 PM   #14
pkgum is offline pkgum  Australia
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are these more accurate specs impressive for a 15" subwoofer?
Is this subwoofer louder than a Velodyne HGS 18? If so ...by how much?

For those who know the PR Stryke audio cube....is this sub louder or is the Stryke louder?

Note: Room gain is NOT included

Relative
Freq .....Gain ...MAX SPL
[Hz] ..... [dB] ....[dB]
10.00 -22.01 95.59
15.00 -15.78 101.82
20.00 -11.80 105.80
25.00 -9.09 108.51
30.00 -7.16 110.44
35.00 -5.76 111.84
40.00 -4.70 112.90
45.00 -3.90 113.70
50.00 -3.28 114.32
55.00 -2.79 114.81
60.00 -2.40 115.20
65.00 -2.08 115.52
70.00 -1.82 115.78
75.00 -1.61 115.99
80.00 -1.43 116.17
85.00 -1.28 116.32
90.00 -1.15 116.45
95.00 -1.04 116.56
100.00 -0.94 116.66


BTW...how much Decibels do you add for room gain in a subwoofer in a typical listening room?
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Old 17th December 2001, 03:46 PM   #15
Wizard of Kelts
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Gum:

I put a couple of links to room gain charts on Ignite's thread, entitled "Room Gain". Here is the link to the thread, which contains the links to the charts: Room Gain

You want to increase performance? Time to say the "P" word-Ported. Run the programs with the speaker tuned to 16 Hz. A 5 inch diameter port that tunes a 4.2 cu. ft box to 16 Hz takes up about half a cubic foot, so be sure to run the program with a box volume of 3.7 cu. ft , or 105 liters, to compensate. If you run Boxpot, make Alpha 1.00-the speaker's Vas is 92 liters, and with Boxplot, you want to take an additional 10 percent off.

Even with the volume adjustments, look at that reponse jump at 16 Hz or above. Yes, as with all ported boxes, once you hit the box tuning frequency, that is it-there is nothing usable under that. But a study has shown-granted, the study was run in the 80's-that there were no soundtracks at all and only 5 music CD's with bass below 16 Hz. It is a great cutoff to aim for.

Don't forget that your hearing becomes less and less sensitive the lower the frequency. To which I will also add that such things as distortion, etc., become less hearable as well. Really, when you move into the under 30 Hz range, you are looking for something to make a roar. The higher frequencies are where the subtle interplay of voice, strings, etc become important, and those are handled by different drivers.

But don't take my word for it. It seems to me that you have a very attractive option. Build the 120 liter enclosure for the 1503. Include in it a 5 inch port-with a good, sturdy, airtight plug, capable of being a permanent installation. Run the sub with the plug in-and the plug out. Compare-it is your sub after all.
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Old 20th December 2001, 02:17 AM   #16
pkgum is offline pkgum  Australia
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ported boxes arn't the way to go....i need superior transient response because i'm listening to 100% MUSIC..not home theatre

I don't want the 'muddy' sound of the ported box which is suited for home theatre.....I rather have the 'constipated' sound of the sealed box because it is quick and suited to music
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Old 20th December 2001, 02:49 PM   #17
Wizard of Kelts
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So now the entire ported principle has been consigned to "Home Theater Only"? Thanks for the news.

I'm sure the people who have spent $5,000 on such speakers as the B&W Matrix 801 will be saddened to discover that they have home theater speakers.

At any rate, the sealed box has it's adherents, and you are perfectly entitled to build your sub on that principle. If only you could find a speaker like the Blueprint 1503 but with a higher Q-that would help your output problems in the very low bass range versus the ported system.

Good luck!
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Old 20th December 2001, 08:20 PM   #18
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I would cheerfully strangle the idiot who started this whole concept that there are "Home Theater" subs and "Music" subs.
A well designed sub is a well designed sub, and will work well for either application. The requirements are identical: flat response, good transient response, low distortion, and adequate volume levels for the listener.
Granted, I lean slightly towards sealed enclosures on a maybe 60/40 ratio, but I've also heard some really excellent ported systems that I could happily live with.

Grey
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Old 21st December 2001, 02:47 AM   #19
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Grey

Quote:
I would cheerfully strangle the idiot who started this whole concept that there are "Home Theater" subs and "Music" subs.
Make room for a second pair of hands.......


pkgum

Your post are beginning to take on a troll like quality.

And FIY it's possible to make a low Qtc ported design, if you have the knowledge........
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Old 21st December 2001, 03:39 AM   #20
pkgum is offline pkgum  Australia
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I've been seriously mislead

--------------------------------------------------------------------------------
I would cheerfully strangle the idiot who started this whole concept that there are "Home Theater" subs and "Music" subs.
--------------------------------------------------------------------------------

I've been mislead by some magazine reviewers who say..."This sub is suited to hometheater"...."This sub is suited to music"....because they can distinguish differences in sound quality between the two applications
The subs they preferred for home theater seemed to consist of a significant number of ported subs while the subs they preferred for music seem to be mostly sealed subs...
Is that the answer why my posts are a troll like quality?
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