Importance of Xlim versus Xmax??

[jakeb]

I am considering using either the Selenium 15PW5 here from partsexpress or I found a Selenium 15PW6 at beachaudio dot com. http://www.beachaudio.com/Selenium/15pw6-p-302706.html
Both companies offer free shipping, have good reviews, and both woofers are about 98 dollars.
Here are the specs for the 15pw6
http://soundmaster.tradernet.eu/products/prod00000014/15PW6.pdf

I modeled both in WinISD and they both yield a good response in a 4cubic foot ported box at 40 hz.

The major difference I see is that the pw6 has 2x the Xlim... I assume from the bigger moter and extended pole piece for more power handling.
Interestingly the specs suggest the frequency response of the 15pw6 doesn't go very low....but winisd doesn't show that.

the 15pw5 gives a smoother response, especially the smaller dip around 400hz. These will be run from 500hz down.

For the price I can't find any other woofers that come close to the performance. The kappa 15 LF might be the next comparable woofer, but is noticeably more expensive

I am using these for a 3 way with dual 15's per cab, for use with a 30hz cut.

Any thoughts on the importance in the specs? Any other suggestions?

[SpasticColin]

All of the drivers you mentioned are nice for what they are, but will disappoint and frustrate you if you try to run them anywhere close to 30 Hz, filtered or not.

In the real world, you would run out of useable excursion at much more than walk-in music levels. Seriously. Yes, the boxes will make noise at higher volume, but nothing anyone really wants to hear.

Look again at the Selenium 15PW6 spec sheet. If Xmax produces 10% distortion @ 4.5mm of excursion, an Xlim of 21mm only means the noisy bits can move nearly an inch before they fly apart. The distortion by then will have increased exponentially. A hard slope low cut filter at 50 or 60 Hz will help control distortion (and self-destruction) but now you are flirting with "hey, I got no bass". Thwack instead of thump is what you got.

Alternatives? Go with some rather more expensive fifteens with bigger motors and more Xmax (Eminence Kappa Pro15LF-2, B&C 15PS100, Peavey Low Rider 15), or stick with high efficiency/low Xmax fifteens and put some subs underneath, like eighteens or some kind of folded horns. If you end up going that way you might as well put twelves in the top boxes and save money and space!

Good luck,

SC

[jakeb]

I appreciate the comments.

A couple of comments.....

1) These are not intended to be subs. The 15"ers need to integrate well with the midrange. As per Zaph himself....the bigger the Xmax tends to reduce the subjective upper mid performance. http://www.zaphaudio.com/lowxmax.html
Albeit, I do need some Xmax...and all prowoofers have reduced xmax compared with High fi subs.

2) Budget is a concern. I am not intending to spend 180 a driver (I need 4 of them!), I have considered the Kappa Pro-15 LF-2, but it only has 6mm Xmax too....with a 120oz magnet, it models almost no better than the Selenium I mentioned. At least not 50 bucks better. The extra few hz of low end performance is not what I am going for. However, I still want solid 40 hz tones, not 50hz that I would get with 12's.

How about other recommedations on equally footed wooofers? I know.....you get what you pay for.

If I am missing something regarding the seleniums I chose...please fill me in.

Also, QSC chose the Celestion 1530 for the 3-way I am cloning.
http://professional.celestion.com/pro/products/tf/detail.asp?ID=17

The QSC seems to perform? am I mistaken?
http://www.qsc.com/products/speakers/dcs/dcs_small_cinema_solution.htm
http://www.qsc.com/products/speakers/hpr/hpr153i.htm

The 3way I am making is a hybrid of the above two. QSC seems to suggest that the celestions will hit 130 peak SPL's???

[SpasticColin]

Your mention of a 30 Hz high pass suggested subwoofer duty.

Flat response to 40 Hz at full power is still going to be difficult to achieve in real world conditions with the drivers you mentioned. Reread my comments.

Maybe you could back up and explain your overall goal for the speaker system, its use or deployment, venue size, associated amplifiers, etc. That's probably where we should have started.

Modeling and spec sheets are fine but they can only take you so far.

I'm still concerned by your reference to Xlim and how it pertains to this discussion.

SC

[jakeb]

More clarification.....

These will not be large venue intended.

Powered most likely by a Behringer ep1500 for starters (260 at 8 ohms -450w rms 4 ohms - woofer section is 4 ohms - 8 ohms mid/tweeter)

I do not plan on running the system FULL power - I am just trying to find the best balance between cost and the Max SPL that can be attained for that cost. I believe this is where the true value of the woofer comes into play. For example, if I can get 129db max SPL from a single 3015LF, or from 4 Seleniums mentioned above..., and goal is equal distortion at 129 (pick a number), why go for 4 of the 3015LF's if that is overkill.

For this same reason, perhaps it is why QSC chose to go with the Celestion....BTW: it only has 2.5mm of Xmax. QSC only recommends a 30Hz cut.

What is my goal max SPL.....I dont' have one.

I am not sure what you mean modeling will only take you so far? I have to buy these woofers on more than faith, right? What more do I have besides modeling and spec sheets??

As for Xlim.....my first question focused on the difference between the two selenium drivers. I thought the Xlim difference was a significant difference. Longer, extended pole piece, less likely for damage, high power handling....Why else did Selenium make this model?

I not sure why you are so confused SpasticColin.

If your suggestions, are going to be vague, as in buy more expensive, more powerful, subs....that is not my goal or intention.

The specific questions are as posed above, feel free to reread.

[billfitzmaurice]

Any thoughts on the importance in the specs? Any other suggestions?
Run your sims in WinISD Alpha Pro and look at the Maximum SPL chart.

[SpasticColin]

I am not sure what you mean modeling will only take you so far? I have to buy these woofers on more than faith, right? What more do I have besides modeling and spec sheets??

****

I not sure why you are so confused SpasticColin.

If your suggestions, are going to be vague, as in buy more expensive, more powerful, subs....that is not my goal or intention.

The specific questions are as posed above, feel free to reread.

jakeb,

You asked a question on the Internet.

You didn't like or understand my answer.

You got what you paid for when you requested free advice.

Besides modeling and specs sheets? Experience.

If I want to be ignored or insulted, well, I'll just go home and spend more time with my family.

Good luck,

SC

[jakeb]

Ok then......

[jakeb]

Bill,


I must be doing something wrong with my Max SPL plot.

I put in the driver info....modeled it for 4 cu, 40hz, and select an SPL plot, and get a nice curve.

I then click the tab on Max SPL tab, and get nothing.

How do I get the settings right to do the proper comparison?

Can I model two drivers side by side?

Also, I have clicked on the Signal tab on the driver window and put in the System Input Power at 100w or whatever, and got a large SPL plot that goes way off the charts.

Am I doing something wrong?

[jakeb]

Ok.

So, I changed the graphing units under File, Options....that helped a bunch.

It appears that I gain nothing in Max output versus Xmax, comparing the Seleniums versus a Kappa Pro LF2, or Kappa LF (all 15's) this in a 4 cubic foot box and tuned to 40 hz. Max output at about 200 watts with max Xmax obtained.


Tuning the Box to 30hz gets about 3db more low end extension at 30 hz, about 2-3 db reduced ouput from 40-100hz. Output limited to 150w with max Xmax.

Does that answer my question? Go with the Selenium 15PW5? The Xmax is 5.5 on the Selenium with 12 Xlim. I know the Kappa 15LF2 has about 18 Xlim and 6 mmXmax.

Am I gaining anything with the Kappa LF2 for 50 extra bucks (besides looks, cast frame...120oz magnet..eminence name...warranty -none issue).

[billfitzmaurice]

Ok.

So, I changed the graphing units under File, Options....that helped a bunch.

It appears that I gain nothing in Max output versus Xmax, comparing the Seleniums versus a Kappa Pro LF2, or Kappa LF (all 15's) this in a 4 cubic foot box and tuned to 40 hz. Max output at about 200 watts with max Xmax obtained.


Tuning the Box to 30hz gets about 3db more low end extension at 30 hz, about 2-3 db reduced ouput from 40-100hz. Output limited to 150w with max Xmax.

Does that answer my question? Go with the Selenium 15PW5? The Xmax is 5.5 on the Selenium with 12 Xlim. I know the Kappa 15LF2 has about 18 Xlim and 6 mmXmax.

Am I gaining anything with the Kappa LF2 for 50 extra bucks (besides looks, cast frame...120oz magnet..eminence name...warranty -none issue).
Now compare those drivers to a Kappalite 3015LF.
Chances are what you thought you needed to use two drivers for can be done with one. As for the crossover to the mids the 3015LF is quite capable to 1kHz.

[jakeb]

I did just model the 3015LF

According to WinISD Alpha

At 1 W the 3015LF - is 97db

2 Selenium 15PW5 are - 100db

For Max SPL - at 300 W , 2 seleniums hit 125db

at 300W for the 3015LF it is 122db

for Max SPL for the 3015LF it is thermally limited to 450W at 124dB

So, Yes, the 3015LF is better than 2 seleniums.

However, at any given wattage, it is also 3 dB less efficient (cone radiating area).

I am not planning on biamping, so not really able to level control.

Also, won't I get 1/2 the distortion at any given SPL? I don't know the distortion specs on the 3015LF

Bottom line, the 3015LF is a great driver. However, it seems that if I don't need 129dB (max SPL according to Eminence specs), I get more SPL for a given wattage with 2 Seleniums. Total Max SPL will be less, but acceptable to me.

[jakeb]

Maybe this factor is most important.

When reading the stated SPL there is a number: Selenium 97, 3015LF - 99.8

Looking at the graphs, in the relative bandwidth 100-500hz, the selenium varies between 98 and 100, and the 3015LF is about 99 straight across.

When plugged into WinISD, the nominal SPL is both around 97dB.

Which one is accurate?

Maybe I could get away with one 3015LF if it truely were 99-100 SPL. Or is it really 97 dB??

Why you ask? I want the mid/horn combo at 100db sensitivity. Has anyone measured a 3015LF for 1W sensitivity?

[billfitzmaurice]

Maybe this factor is most important.

When reading the stated SPL there is a number: Selenium 97, 3015LF - 99.8

Looking at the graphs, in the relative bandwidth 100-500hz, the selenium varies between 98 and 100, and the 3015LF is about 99 straight across.

When plugged into WinISD, the nominal SPL is both around 97dB.

Which one is accurate?

Maybe I could get away with one 3015LF if it truely were 99-100 SPL. Or is it really 97 dB??

Why you ask? I want the mid/horn combo at 100db sensitivity. Has anyone measured a 3015LF for 1W sensitivity?The difference in the 1x15 versus 2x15 sensitivity isn't worth quibbling over unless you don't have enough power to drive the 3015LF. The mid/horn combo sensitivity also doesn't matter, that's why you have EQ. The doubled size and more than double weight of the 2x15 versus 1x15 may not matter to you, it would be of concern to most.

[Paul O]

The doubled size and more than double weight of the 2x15 versus 1x15 may not matter to you, it would be of concern to most.

Yes.. it is a concern because what you're gong to find is that speakers have to be elevated to put sound out in the whole room when it's full of people, and hoisting a double 15 cab off the ground safely is the problem. The solution most people with double 15 tops use is to stack it on top of a sub, but if you're using subs the 15's become redundant so it makes better sense to use a single 15 or 12 top which can be easily hoisted up on a stand in most cases. And that's also good because subs work better on the ground and when they are clustered together.

[billfitzmaurice]

Yes.. it is a concern because what you're gong to find is that speakers have to be elevated to put sound out in the whole room when it's full of people, and hoisting a double 15 cab off the ground safely is the problem. The solution most people with double 15 tops use is to stack it on top of a sub, but if you're using subs the 15's become redundant so it makes better sense to use a single 15 or 12 top which can be easily hoisted up on a stand in most cases. And that's also good because subs work better on the ground and when they are clustered together.
Of course, but he stated that he wanted to go with a 3 way with a 30 Hz F3. Separate subs and 2 way tops loaded with tens or twelves are far more practical and versatile, but I assumed he had his reasons for not taking that route.

[wg_ski]

but I assumed he had his reasons for not taking that route.

The likely reasons are limited amplifier power (single EP1500) and ease of just hooking up a pair of speakers and an amp (no biamp/crossover). I wouldn't try to mic a rock band through it, or even DJ a school dance, but sometimes a single pair of full range cabs is all you need.

[badman]

For modest, real world output, either will be plenty, in a domestic space. Naturally, there are those who pray to the headroom gods, but 15"s are 15"s. Sure, they're substantially Xmax limited at LF, but the lower you tune, the less of an issue that tends to be, and at 30Hz, a pair will do 110dB or so at the listening position. That accounts for typical in-room behavior of a pair of 15"s.

This equates to 90dB continuous with 110dB peaks, without significant limiting.

And Xmax isn't usually treated as 10% distortion, though sometimes that's how it's speccd- it's usually the amount of overhang.

[billfitzmaurice]

a pair will do 110dB or so at the listening position. In a living room at eight feet away, yes. This is the pro-sound forum, where the listening position is usually a tad further out. :D
If the OP is using these in a living room he'd be better served with speakers intended for that application.




And Xmax isn't usually treated as 10% distortion, though sometimes that's how it's speccd- it's usually the amount of overhang. The overhang method of measuring xmax was rendered obsolete by Klippel analysis, which give a much more useful spec for real world applications. If you see a driver spec'd via the overhang method it's because the manufacturer hasn't gone to Klippel yet. Another benefit to Klippel is that it works with underhung coils, which otherwise would be listed with an xmax as small as zero.

[badman]

In a living room at eight feet away, yes. This is the pro-sound forum, where the listening position is usually a tad further out. :D
If the OP is using these in a living room he'd be better served with speakers intended for that application.


The overhang method of measuring xmax was rendered obsolete by Klippel analysis, which give a much more useful spec for real world applications. If you see a driver spec'd via the overhang method it's because the manufacturer hasn't gone to Klippel yet. Another benefit to Klippel is that it works with underhung coils, which otherwise would be listed with an xmax as small as zero.

Well, don't that bust all. I thought I was in the general forum, hahahahhahaha.

Xmax specs are simply not standardized, it's not necessarily that a manfuacturer doesn't use klippel analysis, but often that they've done the overhang method since forever and continue to do so.

But point well taken. Thanks for the forum awareness piece especially) I'll doublecheck the header in the future. I think it's time for me to cut back on forums, I'm registered at quite a few.

[billfitzmaurice]

Xmax specs are simply not standardized, it's not necessarily that a manfuacturer doesn't use klippel analysis, but often that they've done the overhang method since forever and continue to do so.
.Klippel is the defacto standard today, but yes, not all manufacturers have adopted it yet, though there's no excuse for it IMO.
A few years ago Dupont (Kapton) dropped out of the voice coil former business, forcing everyone to switch suppliers, and that resulted in changes to driver specs. That time line coincided with the introduction of Klippel, so when Eminence re-measured all their drivers with the new coils they did so using Klippel, so all their specs are Klippel based.