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[Ernest Walsh]

hello,
maybe you can help me select which speaker parameters to compare when I'am choosing a speaker?
I will provide the settings, one higher and one lower , you should say that parameter should be higher or lower, in order to choose the speaker for building subwoofer.
For example: As a general rule of thumb, a lower Fs indicates a woofer that would be better for low-frequency reproduction than a woofer with a higher Fs. Of course: This is not always the case though, because other parameters affect the ultimate performance as well. Source:http://www.eminence.com/support/understanding-loudspeaker-data/


For me it is important to know what other parameters should be . And maybe you can help select a parameter important and which are not.

P.S. I ask you to talk about the options in choosing a speaker for its parameters. For now it's just about speaker parameters, not about the speaker box or anything else.

*BL factor: 26 N/A  vs  24 N/A (higher is better vs lower is better) (important / less important)
*Moving mass: 0,165 kg  vs  0,101 kg  (higher is better vs lower is better) (important / less important)
*Winding length: 25 mm  vs  20 mm (higher is better vs lower is better) (important / less important)
*Air gap height: 14 mm  vs  12 mm (higher is better vs lower is better) (important / less important)
*Qms: 14,2  vs  7,7 (higher is better vs lower is better) (important / less important)
*Qes: 0,32  vs  0,18 (higher is better vs lower is better) (important / less important)
*Qts: 0,31  vs  0,17 (higher is better vs lower is better) (important / less important)
*Vas: 250 l  vs  85 l (higher is better vs lower is better) (important / less important)
*Cms: 229 µm / N  vs  83 µm / N (higher is better vs lower is better) (important / less important)
*Rms: 3,2 kg/s  vs 2,8 kg/s (higher is better vs lower is better) (important / less important)
*Sd: 0.0855 m²  vs  0.0755 m² (higher is better vs lower is better) (important / less important)
*Xmax: 9,5 mm vs 7,5 mm (higher is better vs lower is better) (important / less important)
*Vd: 805 cm³ vs  705 cm³ (higher is better vs lower is better) (important / less important)
*Le @1 kHz: 2.7 mH vs 1.7 mH (higher is better vs lower is better) (important / less important)

[Ivan Beaver]

That is NOT an easy question to answer-especially on a forum type discussion with an open ended question.

In most cases there is no "better" or worse, but rather better for a particular type of application.

It depends on what you are trying to "accomplish".

Is it low freq reproduction?  What does that mean? is 50Hz low or is 20Hz low.

WHat sort of box configuration are you looking at? Ported-sealed-bandpass-horn?

Is sensitivity important to you?

Depending on the answers to the question, you will come up with different parameters that are better suited to one style of cabinet or another.

There is no "one set of parameters is better for all cabinets".

What makes one parameter for one cabinet better makes it worse for another type of cabinet or usage.

FIRST you have to define exactly what you are looking to do (performance wise-size wise etc) with the cabinet.

THEN you start to look at drivers.

Sorry but it can get VERY involved.

And sometimes drivers with different parameters can end up "cancelling out" and ending up with a net result pretty much the same.

There is no perfect equation-sorry.

[Art Welter]

Ivan said all the right stuff.
That said, in regard to output in the "sub" range, there is no replacement for displacement, so Sd x Xmax will give a good idea of what can be expected from a driver, (assuming the specs are correct), and assuming the driver can handle enough power to be driven to Xmax in a particular design.

In general, horn loaded designs require more Bl to push the driver under high compression ratios, and more MMs to withstand the higher forces without buckling.

[Ernest Walsh]

That is NOT an easy question to answer-especially on a forum type discussion with an open ended question.

In most cases there is no "better" or worse, but rather better for a particular type of application.

It depends on what you are trying to "accomplish".

Is it low freq reproduction?  What does that mean? is 50Hz low or is 20Hz low.

WHat sort of box configuration are you looking at? Ported-sealed-bandpass-horn?

Is sensitivity important to you?

Depending on the answers to the question, you will come up with different parameters that are better suited to one style of cabinet or another.

There is no "one set of parameters is better for all cabinets".

What makes one parameter for one cabinet better makes it worse for another type of cabinet or usage.

FIRST you have to define exactly what you are looking to do (performance wise-size wise etc) with the cabinet.

THEN you start to look at drivers.

Sorry but it can get VERY involved.

And sometimes drivers with different parameters can end up "cancelling out" and ending up with a net result pretty much the same.

There is no perfect equation-sorry.

Thank you for your response.
Yes, that‘s definitely not an easy question but at the same time that‘s the reason why I‘m looking for help here in „LAB Subwoofer Forum“. I believe that people here have some experience in making subwoofer.

Yes, I do understand that it depends on the result that one wants to achieve but I also think that it‘s equally important for everyone to recreate the range of frequency from 35Hz/40Hz to 150Hz (-3db), continuous max SPL output above 130 db.
The box itself doesn‘t matter to me. What matters is the result. Subwoofer will be used both indoors and outdoors. I‘m thinking of using 15‘‘ speakers for indoors and 18‘‘ for outdoors. The style of music varies from live music with drum kit to Hip-Hop DJ. The subwoofers I have are EV ELX 118P, Dynacord A 118 A, JBJ PRX 715XLF, Wharfedale Pro Lx-218b, JBL SRX 728. Even though the quality of JBL isn‘t of the highest rank, I like them since they‘re powerful and also reliable. Especially JBJ PRX 715XLF: such a small box with so much power.
Let‘s focus on the power since for me high output power is the first priority. The size of the box isn‘t  the most important criteria, I‘m willing to sacrifice the size of it for higher power and better quality of frequency recreation. Having in mind that speakers won‘t be moved often.

Is the sensitivity important? Yes, it is since it can be related to efficiency. However, the often written sensibility of a speaker (for example: Sensitivity:100 dB 1 W @ 1 m @ 2Π) is usually the average sensitivity in the whole spectre of recreated frequency, right? Since we’re creating subwoofer, it doesn’t matter to us that the sensitivity of a speaker at 1000Hz is 101 db, we’re focusing on the sensitivity from frequency of 35 Hz to 150 Hz. So, even though the sensitivity of one speaker is 100 db and 96 db of another, in the spectre of frequency (35-150Hz), the bigger sensitivity might be of the second one even though only 96 db is declared? Is that right?

Boxes. Isn’t that strange that, for example Beyma, offers boxes of the same size for different 15’’ speakers with completely different parameters? Of course, these are only recommendations but it’s still strange...
http://www.beyma.com/uploads/descargas/1353675167.pdf
http://www.beyma.com/uploads/descargas/1353675289.pdf
http://www.beyma.com/uploads/descargas/1353675039.pdf

Since the box size doesn’t really matter, I suppose one should firstly choose right speaker and only then start making the box which would match the speaker.

The parameters I’ve mentioned should help in comparing different speakers and choosing which one is better since both of the speakers made by different companies might be extremely similar (for example, AES power both can be 1000w, both speakers can be 15’’,  both can have impedance of 8 ohms, the spectre of frequency can be the same 30-2000 Hz, Voice coil diameter 100 mm 4 in the same, sensitivity, once again, also the same: 98 db, sensitivity in the spectre of frequency also very similar from 35 to 150 hz), so small parameters should help us to decide which one is better. That’s why I’m looking for help here. I need some help with the comparison of small parameters.

[Art Welter]

1)Yes, I do understand that it depends on the result that one wants to achieve but I also think that it‘s equally important for everyone to recreate the range of frequency from 35Hz/40Hz to 150Hz (-3db), continuous max SPL output above 130 db.
2)The box itself doesn‘t matter to me. What matters is the result. The subwoofers I have are EV ELX 118P, Dynacord A 118 A, JBJ PRX 715XLF, Wharfedale Pro Lx-218b, JBL SRX 728.
3)Is the sensitivity important?
4)However, the often written sensibility of a speaker (for example: Sensitivity:100 dB 1 W @ 1 m @ 2Π) is usually the average sensitivity in the whole spectre of recreated frequency, right?
5)So, even though the sensitivity of one speaker is 100 db and 96 db of another, in the spectre of frequency (35-150Hz), the bigger sensitivity might be of the second one even though only 96 db is declared?
6)Boxes. Isn’t that strange that, for example Beyma, offers boxes of the same size for different 15’’ speakers with completely different parameters?
7)Since the box size doesn’t really matter, I suppose one should firstly choose right speaker and only then start making the box which would match the speaker.

Ernest,

1) Everyone does not require the same output as you do ;^). Continuous output can be quite different depending upon measurement and rating, often 10 dB or more higher than you will see in the real world.
2) Boxes are a means to an end.
3) Yes, but power compression is also important, in the link below if chosen by sensitivity, a pair of Lab 12 are higher, but after power compression is accounted for, a less sensitive speaker ultimately has several dB more output.
Sensitivity also does not account for Xmax, higher Xmax speakers are heavier and less sensitive, but given more power, can have more output.
4) Sometimes it is, sometimes it is reported at a frequency peak.
5) Yes, you need to look at the graph, and determine what voltage was used. A 2.83 voltage on a four ohm speaker will be 3 dB higher than if 2 volts (one watt) was used.
6) The bass reflex box will always provide the same tuning, different TS parameters will affect the alignment- a large VAS speaker will not perform as well in a small box, etc.
7) Size does matter, can't escape Hoffman's Iron Law- Loud, Low, Small-pick two.
That said, using a driver with a lot of Xmax, and a design that is 6 dB more efficient can result in a smaller cabinet capable of more output:

http://www.diyaudio.com/forums/subwoofers/185588-keystone-sub-using-18-15-12-inch-speakers.html

The single 18" Keystone has very similar sensitivity and frequency response to the JBL SRX 728, is smaller and lighter, but because of the lesser thermal compression and greater excursion capability of the B&C 18SW115-4 is capable of more output.

Art

[Ernest Walsh]

Art,
I have to study more, thank you for your reply! 

[Ivan Beaver]

Art,
I have to study more, thank you for your reply! 

It is all a matter of tradeoffs.  You trade something for something else.

Different situations/needs have different requirements.

If you think you will find the "perfect combination", you may be hunting for quite a while.  Because what is perfect for one case is completely wrong for another.

Yes sensitivity is important, yes power handling is important.  But at what freq?  Sometimes a "wimpier" driver can actually get louder than a beefier driver-depending on the cabinet-the freq etc.

[ProSoundWeb Community]