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[Shivraj Persaud]

In my search for a good sub plan I came across this plan by selenium on partsexpress.com. It uses 2 15" woofers and will give good bass down to 40hz. Its seems very easy to build.

Here is the link.

  http://www.parts-express.com/mfg/selenium/selenium-cabinet.c fm

thats a link with a lot of plans.

Here is the subwoofer.

http://www.parts-express.com/pdf/selenium/hb1505d1.pdf

[Mike {AB} Butler]

Hmmm..
It would seem to be all right... BUT! My only concern is seeing no Plots for the response (even though it's "from" Selenium). Unless you can get some testimony from a user that has done AND correctly measured these, I'd be more inclined to bet my $$ on the LAB sub (this one isn't significantly smaller, either - less than a 5" difference in height).
Regards,

[Shivraj Persaud]

I cant find any plots, but they should do 137db down to 40hz. They're no way as big as Labsubwoofers. Or see lab sub junior on cowanaudio.com

[Shivraj Persaud]

someone model these already, there basically whats EAW calls the DCS2. for dance clubs. http://www.crownaudio.com/apps_htm/designtools/elect-pwr-req .htm

plugging in 106db and 140db at listener level, 4 of these should provide that.

One of these boxes is bigger than the other.

[Ivan Beaver]

Shivraj Persaud wrote on Tue, 08 December 2009 14:10

I cant find any plots, but they should do 137db down to 40hz.

If you can't find any data-how do you know what they will produce at what freq?

Yes it says they will go down to 40Hz-but so will my tweeters-just how loud is the question.

[Mike {AB} Butler]

Shivraj Persaud wrote on Tue, 08 December 2009 14:10

I cant find any plots, but they should do 137db down to 40hz. They're no way as big as Labsubwoofers. Or see lab sub junior on cowanaudio.com

OK, as Ivan pointed out, you can't take the max SPL output (calculated), and expect these drivers to put out that Max SPL at 40 Hz. In fact, many times the Maximum SPL is waayyy up past the top corner frequency of a typical sub's band pass (I had once had a driver that had it's peak SPL output up at around 810 Hz - no where near the 100 hz HP that the sub was designed for!!). In my 29 years of building subs, I have yet to ever see a subdriver where this wasn't true.
As far as the size, I was quoting the height. IMO, the box IS a Horn, and is still a pretty good sized cubic foot chunk of real estate at 39.371" tall (The Labsub being "just" 44" tall)..  

[Shivraj Persaud]

You're right about that, they're pretty big didn't realize. 39x39 vs 45x45. Wow .. and wider almost 40" hehe. Wow ... I like these cause they are easier to build than lab subs. Good power handling, 1200-1400 watts RMS.

[Art Welter]

Shivraj Persaud wrote on Wed, 09 December 2009 14:43

You're right about that, they're pretty big didn't realize. 39x39 vs 45x45. Wow .. and wider almost 40" hehe. Wow ... I like these cause they are easier to build than lab subs. Good power handling, 1200-1400 watts RMS.

Shivraj,

The size is not 39 x 39, it is approx 39 x 23.4 x 31.2, so about 16.2 cubic feet compared to the Lab sub at 26.36 cubic feet.

I'd expect the frequency response to be similar to my "C horn", the path length and layout are similar.

I went to front loaded 2x12" Lab 12, gave up the upper bass for more low end in a smaller package.

The two are compared below, blue is a single 15" "C horn", yellow the 2x12".
2x12 is 7.76 cubic feet, "C horn" 10.35 cubic feet.

[Shivraj Persaud]

Youre right I made a mistake, not familiar with the metric system. When will America get into the new millenium, (NEVER )

Yes there are two boxes,

1 - 39x34x24 approximately
2 - 39x30x30 approximately
3 -- an 18 inch version also

see link

http://www.parts-express.com/mfg/selenium/selenium-cabinet.c fm

Also I bought 4 B&C 15PS100 woofers which I was gonna build regular bandpass boxes but those are not that efficient about 99db.

With this kind of driver I believe these should do 105+ db. +/- 1 db. what do you guys think, what kind of efficiency can be expected ?

[Ivan Beaver]

Shivraj Persaud wrote on Thu, 10 December 2009 00:08

Youre right I made a mistake, not familiar with the metric system. When will America get into the new millenium, (NEVER ) Yes there are two boxes, 1 - 39x34x24 approximately 2 - 39x30x30 approximately 3 -- an 18 inch version also see link  http://www.parts-express.com/mfg/selenium/selenium-cabinet.c fm Also I bought 4 B&C 15PS100 woofers which I was gonna build regular bandpass boxes but those are not that efficient about 99db. With this kind of driver I believe these should do 105+ db. +/- 1 db. what do you guys think, what kind of efficiency can be expected ?

When you start talking horns-everything is not as it seems.  It is not so much about the particular driver specs-as how THAT driver is used in the box and how well the box and driver work together.  Look at the lab 12 drivers-the sensitivity pretty much sucks-but look how they work in a properly designed horn.

AND where the specs come from (what part of the response curve did the sensitivity number come from).

I remember my eye opening event (in that regards) years ago.  I was running single and double 15" scoop cabinets.  I was using JBL E140's in them-because they had the highest sensitivity of any of the bass speakers in the JBL line.

Everybody was telling me I should be running JBL 2225's-but I pushed back because they had a lower sensitivity "rating".
Eventually I purchased a couple of 2225's and WOW-those were so much louder-but how could that be?

Upon closer examination of the specs-I saw that the E140 was rated in a higher freq band than the 2225's were-hench the different sensitivity.

You CANNOT describe how a loudspeaker reacts (power-sensitivity-freq response etc) with a single set of numbers.  It is a very complex thing that HAS to be looked at from various angles.

The BEST way is to build one and measure it accurately and THEN you will have an idea of what it will actually do.

Models will give you clues-but will not tell the whole story.

[Art Welter]

In the 80-100 HZ range, the single 15 “C horn” pictured in my previous post is around 103 dB one watt one meter. Doubling the “C horn” would bring it to 106 dB one watt one meter, in line with your expectation, but it would be about 97 dB at 40 HZ.
The above results are using  EVX150A speakers.
I would expect the Selenium 2x15” folded horn to be very similar.
The horn needs a fair amount of EQ to be “flat”, but sounds good after the EQ.

So far, I have not heard a bandpass box that sounds as good (defined bass)as a proper bass reflex or horn even though they may read a few dB louder.

[Shivraj Persaud]

http://www.cowanaudio.com/hornsubjr.html

Well then I was wrong to assume this Selenium Folded horn would have the same response as that little subwoofer.

I understand about the dB. My 15PS100s are rated at 94.5db and my friends fane 15xb colossus are rated at 99 db. I started drueliing over the db, but when I looked at the curve its about the same One is over rated and the other is not.

If what William is saving 106db and flat to 40hz is true that is one great little subwoofer.

Check out his tapped horns too... great site

[Art Welter]

Shivraj Persaud wrote on Thu, 10 December 2009 12:25

http://www.cowanaudio.com/hornsubjr.html Well then I was wrong to assume this Selenium Folded horn would have the same response as that little subwoofer. I understand about the dB. My 15PS100s are rated at 94.5db and my friends fane 15xb colossus are rated at 99 db. I started drueliing over the db, but when I looked at the curve its about the same One is over rated and the other is not. If what William is saving 106db and flat to 40hz is true that is one great little subwoofer. Check out his tapped horns too... great site

Note that the figures William Cowan is talking about are in room, corner loaded.
The short horns simply won't do that unless corner loaded.

“The horn fires into the corner at 45degrees with the horn mouth touching the two walls, creating a triangle in the corner between the top of the box and the corner itself. Firing the horn at the corner at 90 degrees raises the LF cutoff by some 5Hz, with an optimal spacing (around 300mm).”

[Shivraj Persaud]

oh I didnt realize. thats good to know.

[Shivraj Persaud]

what do you guys think about these two subs ?

http://www.speakerplans.com/index.php?id=184sub

http://www.speakerplans.com/index.php?id=x1

Is this for real?

[Caleb Dick]

What's wrong with the LAB sub?  That would be my first choice for a DIY sub.

Caleb

[Shivraj Persaud]

I actually built a labsubwoofer. Its way way too big.

[Art Welter]

Shivraj Persaud wrote on Thu, 10 December 2009 19:41

what do you guys think about these two subs ? http://www.speakerplans.com/index.php?id=184sub http://www.speakerplans.com/index.php?id=x1 Is this for real?

Very similar to  one half of the cabinet in the current
“6th order bandpass build”
thread, and easier to build.
Building two cabinets rather than one has the advantage of a stiffer cabinet, and killing one cone won’t allow the dead cone to absorb the live cone’s output.
The specs are simulated, but they look believable.

As I have said before, so far, I have not heard a bandpass box that sounds as good (defined bass) as a proper bass reflex or horn even though they may read a few dB louder.

That said, for program material that goes “boooooom booooom”, this type of cabinet could be the cat’s pajamas, especially if they were built in Rog Mogale’s temple in Tibet by a team of hand picked Shaolin masters who can support all there weight on one finger for hours .

Art Welter

[Shivraj Persaud]

Thanks Art I learned a lot from your posts and others.

I came across the Beyma 18LX60 but they are discontinuing it.
Why would they discontinue such a great woofer?

Its 18" Vas - 500L gts- 0.36 qms - 11.45 ges - 0.35

According to some program called ajdesigner it would make a really good vented box. -3dB at 30hz.

Are there any other drivers in the same ball park ?

[Ivan Beaver]

Shivraj Persaud wrote on Thu, 17 December 2009 00:18

Thanks Art I learned a lot from your posts and others. I came across the Beyma 18LX60 but they are discontinuing it. Why would they discontinue such a great woofer? Its 18" Vas - 500L gts- 0.36 qms - 11.45 ges - 0.35 According to some program called ajdesigner it would make a really good vented box. -3dB at 30hz. Are there any other drivers in the same ball park ?

Don't start getting hung up on particular drivers.  At one time you were talking horn-loading-then it went to bandpass-and not you are talking vented.

VERY different designs-with different woofer needs.  What works great in one box design may be lousy in a different box design (VERY common).

You need to settle on what type of design you want-THEN find the driver that works for THAT design.  NOT finding what you think is a "great driver" and then trying to fit a box around it.

The two (box and driver) need to bve matched to each other-jsut like a marriage.  Just because you have 2 "great" people does not mean they are compatable.