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Old 8th November 2001, 02:45 PM   #1
ogp is offline ogp  United States
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Hi all. I am planning on building a pair or two of ported satellites (one pair for monitoring) with two <a href="http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=290-403&DID=7">10's</a> or <a href="http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=290-405&DID=7">12's</a> and a <a href="http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Product_ID=7607&CATID=49">horn tweeter</a> (all eminence drivers). As far as the subwoofer goes, I was thinking about stereo 15's, but am not sure of the type of subwoofer I should use. I plan on using the Eminence <a href="http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=290-460&DID=7"> KAPPA-15LFA</a>. Here are the specs:

*Power handling: 400 watts RMS
*Voice coil diameter: 3"
*Voice coil inductance: 1.27 mH
*Impedance: 8 ohms
*DC resistance: 5.4 ohms
*Frequency range: 35-3,000 Hz
*Magnet weight: 95 oz.
*Fs: 39 Hz
*SPL: 101 dB 1W/1m
*Vas: 5.6 cu. ft.
*Qms: 6.08
*Qes: .41
*Qts: .38
*Xmax: 5.5mm

I have had one person give the opinion that I should use a 4th order bandbass box which doesn't sound like a bad idea since they have good transient response and power handling. But does anyone have any other suggestions? Should I go with a ported or sealed design? If so, why?
On a side note, do you think I should make the satellites ported? Would it be better to make them sealed?

Thanks for any suggestions or comments.

Dave
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Old 10th November 2001, 08:35 PM   #2
Wizard of Kelts
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OGP:

According to AVI loudspeaker program, a 1 cu. ft sealed box will give you a 3 dB cutoff at 80 Hz. Small box, but not exactly subwoofer territory. A 2 cu. ft sealed box scarcely improves matters-a 72 Hz cutoff. Double the size, but only get one sixth octave more bass-not good.

A cyber friend of mine from Ireland who runs a DJ business-he has people working for him-likes Eminence and likes a 3 cu. ft box as being the best combo of bass and portability. That 3 cu. ft. box will give you a minus 3 dB cutoff of 50 Hz if tuned to 45 Hz.
The lowest note of a bass guitar is 42 Hz. To obtain that, you need a box of 4.5 cu ft tuned to 41 Hz. The last two designs were obtained using the Boxplot program.

I should point out that most 15" PA speakers have a cutoff of 60 Hz. in a 3 cu. ft box. So these do a little better than that. Hope this helps.

I can give you port diameters and lengths if you tell me what size box you want.


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Old 11th November 2001, 12:14 AM   #3
ogp is offline ogp  United States
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so are you suggesting a closed box? Doesn't the F3 represent the cutoff frequency of the speaker? What do you mean by tuning it to 45 Hz? Is this the optimal frequency the speaker reproduces? I thought I had a decent understanding of the basics, but I seem to be slightly confused. Could you point me to a site where they explain the basics of design?

Anyway, are you suggesting a closed design because you think it would perform better than a vented or bandpass? What do you think about the satellites? Should they be vented or sealed? Thanks again for any help. BTW, I am using Unibox for designing these speakers.

Dave
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Old 12th November 2001, 04:04 AM   #4
Wizard of Kelts
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OGP:

I should have explained myself better. The last 2 designs are ported. You cannot tune a closed box design; you can only build a bigger or smaller box. You can only tune a ported, (bass reflex), box. You do this for any given enclosure by changing either the area or the length of the port.

80 Hz is way too high a 3 dB cutoff point for a 15 inch woofer. It definitely should go down deeper. You need a ported box as opposed to a sealed box.

I have not built a large bandpass box. Generally, they are not usually superior to ported units in deep bass response for any given enclosure size. I will let someone else tell you how to build a bandpass box if you or they think superior results can be achieved that way.

I haven't found a good tutorial for Thiele-Small parameters and how to use them on the net. I learned from the book, Designing and Building Loudspeaker Systems by David Weems.

Sometimes the box is tuned to the F3 frequency, sometimes not. I don't have Unibox, but all the design programs are similar. I will give you some tips.

A) If your Qts equals .38,(or .4), and you build your box volume to equal Vas, and tune your box to the free air resonance,(Fs), then your F3 will be equal to Fs.

B) If your Qts is .38 or so, and your box is smaller than Vas, then the smaller box should be tuned somewhere above Fs, and in fact F3 will be above the new box tuning frequency. For instance, if you decide to build a 3 cubic foot box for your Kappa, your box tuning frequency will be 45 Hz and your F3, (3 dB down point) will be 50 Hz.

Let me know how big a box you want-remember, the larger the box, the deeper the bass-and I will give you the specifications as to how low it's 3 dB cutoff point is, (the lower the better), and the size and length of the port. Your ported box can range from 2.5 cubic feet up to 11 cubic feet. Again, the larger the box, the deeper the bass.

[Edited by kelticwizard on 11-11-2001 at 11:23 PM]
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Old 13th November 2001, 02:10 AM   #5
ogp is offline ogp  United States
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Could you please clarify what the difference is between the F3 of my speakers and what I tune them to?

I thought the F3 was the cutoff of the frequency they could reproduce or something. Am I right?

I've been playing with Unibox and thinking I might possibly make a 5 cu. ft. box. Could you tell me exactly what I want my spl vs. frequency graph to look like? Don't I want a gradual slope as oppossed to a steep one? Thanks.

Dave
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Old 14th November 2001, 12:33 AM   #6
Wizard of Kelts
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F3 = the point at which the bass response rolls off to where it is 3 dB down from the norm. Below F3 the bass response increasingly goes down.

Fb = the frequency the box is tuned to. A combination of how large the box volume, plus the area and diameter of the port, determines the box tuning frequency. For instance, an internal box volume of 2 cubic feet with a round 3" diameter port that is 8.4" long will be tuned to 30 Hz.

Important: Fb and F3 are NOT necessarily the same.

Yes, sometimes Fb is is a little lower than the F3 cutoff. In most speakers, (not all), the response rolls off at 18 dB per octave or even faster. So in most cases, Fb is the lowest note that the speaker can really effectively reproduce, even if it is located slightly below the F3 frequency.

I will soon post how to tune your 5 cu. ft box. Gotta run now.
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Old 14th November 2001, 04:28 AM   #7
ogp is offline ogp  United States
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How do I know where I should have the frequency cutoffs for my tweeters, midrange and subwoofer? I want to have my satellites consist of two <a href="http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=290-405&DID=7">12"</a> woofers and a <a href="http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Product_ID=7607&CATID=49">comp ression tweeter</a>. The frequency range of the woofers is 45-5,000 Hz while the tweeter's range is 1.2 kHz-12 kHz. The <a href="http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=290-460&DID=7">15"</a> sub's range is 35-3,000 Hz.
Should I go with a first order crossover? Is the steeper slope of higher order crossovers detrimental to the "flow" of sound or something?
As I mentioned earlier, I was thinking of going with a 5 cu. ft. sub and I think the satellites will be 3 cu. ft. Everything will be vented. What do you think?
One last thing, I am a little confused about the <a href="http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Product_ID=7607&CATID=49"> horn driver</a>. Does it need a lense? The picture makes me think that it does, if this is true, how do I know which one to pair it with?

Thanks again for answering my questions on this.

Dave
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Old 14th November 2001, 05:38 PM   #8
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Exclamation Kappa 15 efficiency

Hi there,
Just wanted to flag up a small issue with Eminence cone drivers - the sensitivity ratings they quote seem to be on the high side compared to reality.

Here's a couple of equations I've seen for calculating it yourself....

Reference efficiency = ((Fs^3*Vas*2.7E-8)/Qes)*100

Sensitivity = (10*log(Reference efficiency/100))+112

Using the T/S parameters you quoted yields a sensitivity of 95.4dB, quite a lot less than the 101dB they quote.

Hope this is useful to you - and if anyone has more info concerning those equations - feel free to correct me if needed.

Cheers,
David.
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Old 15th November 2001, 12:23 AM   #9
walker is offline walker  Australia
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Dmorrison, maybe you are being a little unfair. As I understand the 101dB/W/m reading was recorded down hill with a tail wind and Venus was aligned with Mars!

If a manufacturer exaggerates their specs then I believe it's a waist of my time trying to use their products.

Regards WALKER

PS 101dB/1W/1m, 400Wrms =137dBspl!!!!!! Thats as much as some jet engines.

[Edited by walker on 11-14-2001 at 07:30 PM]
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Old 15th November 2001, 04:46 AM   #10
Wizard of Kelts
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OGP:

For a 5 cubic foot box, I would tune the Eminence Kappa 15 inch to 38 Hz. This will give you an F3 of about 42 Hz.

To accomplish this, use a round 5" port of 3.67", or three and five eighths inches length.

I cannot dispute DMorrison's calculations about SPL. I can only say that when I see a chart of most brands of pro sound speakers, the SPL @ 1 Meter/Watt ratings really do seem exaggerated by about 2 dB or so. Six dB seems excessive. I can only say that from what I have heard, Eminence is a highly regarded speaker. You might try Emailing or contacting Eminence to get a frequency response chart to check. If you do get a frequency response chart-I sent for and got them from Eminence years ago-remember that that the chart will show the speaker when it is not enclosed. An unenclosed speaker will have a response chart that indicates virtually no bass. The bass response picks up when the speaker is enclosed.

Hmmm. Just checked the sensitivity ratings on BoxModel. According to that program, these Thiele-Small numbers add up to a speaker that plays at 95.5 dB @ 1Meter/Watt, just as DMorrison said.

[Edited by kelticwizard on 11-15-2001 at 12:58 AM]
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