Which 15 or 18 ınch woofer- best for open baffle

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Years ago I built a pair of OBs that used Selenium 15" woofers with a Qts of 0.7 I found them ideal to work with and very much enjoyed the sound. My neighbors also enjoyed the sounds. :) Alas one woofer was crushed when we moved house, and they don't make them any more. PRV does have a similar woofer for sale, tho.
 
https://www.newark.com/mcm-audio-select/55-2974/15-woofer-with-poly-conerubber/dp/80R7013

Note the review (right side of page scroll down on review section) by "montekay".


I've got just a pair of these parallel connected for the low-freq. effects channel in my floor-loaded dipole sub platform for my HT. I should have gotten at least 4.. but they still do well for that task with just 2 even though I'm over-driving them. The only problem I did have with them is that the VC leads were bowed-out/down to the cone so much that when driven to over-excursion that the diaphragm slapped against the VC leads. I got rid of this problem by gluing the excess leads to some felt that I glued to the frame (right near those leads); sort of a "lift and separate" of those leads.

It's NOT a driver I'd want to use much above 90 Hz because the motor is so weak that it lacks clarity/articulation. (..a .6 Qts driver with most of that lower number derived from a low Qe, usually provides better clarity - but it looses-out on bass extension near the average.)
 
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Not truth, if you read my subsequent post.

TRUTH:

Maybe the best option if OB is you thing is to double up the number of drivers you think you need right away. The distributed load difference between 2 x 15s and 4 x 15s a side is significant. I use 6 x 15s a side with FS of the drivers at 42hz and I do get a slight roll off below 40hz after EQ but usable down to 25hz and I don't hear the stress that I heard with 2 x 15 a side.

For OB I like the presentation of less physical impact. It does not pressurize the room like sealed or ported.
 
Hi
8 for open baffle config and 2 for a sealed box project I had going on.
And here I am. About 6 month later, and I am very very pleased with the sound I get. The speakers go deep. They start falling rapidly at about 28 Hz. So I guess the listed FS at 26 Hz is about right. I cross them over at 100 Hz 24dB-LR filter. I wouldn’t go much higher than about 110 Hz. The sound is deep, punchy and has good detail. 8 woofers move a lot of air and thus the distortion is low. But 4 woofers can also do, the job nicely.

That speaker looks great! Very nice job. I would be interested in building something like this. Do you have a build thread somewhere? or at least some more information like a design or measurements?
 
Here are some measurements:
I have measured te frequency responce at 2 different positions in my room, to show how big an impact the romm has on the bas responce.
I have also included a measurement, with no x-over. The x-over is 24db @100Hz
 

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Now that I'm here.
Has anyone tried the GRS woofers? They look to offer great value for the money.
I have succesfully used the GRS 10PF-8 in a couple of designs, but the bigger 12PF-8 og 12SW-4 look interesting for OB bas.
Can anyone advise on what to go for:4x 12PF-8 (cone area) or 2x 12SW-4 (x-max).

Here is some info:
Model Qts Fs Xmax Sen Pris Eur
12PR-8 1,26 32 3,5 84 30
12PF-8 1,54 35 3,5 87 23
12SW-4 0,98 29 8,5 88 37

10PF-8 1,27 43 3 87 18,5
15PF-8 1,39 29 4 87 40
 
Two very smart guys with more experience than most (and serious $$ resources!) in subwoofer design and open baffle bass systems are:
http://www.humblehomemadehifi.com/download/Humble Homemade Hifi_Serious Sub.pdf
and "Stig Eric" on this DIY forum, search up his "https://www.diyaudio.com/forums/multi-way/142015-baffle-dipole-beyma-tpl-150-a.html thread which ends up with THE best ever open baffle bass... One of the best threads ever on this forum... The guy is a legend!
Cheers
A.
 

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Wow that is cheap!

Several years ago i tested OB with Alpha 15a driver to get a feeling of it. I think the GRS on paper look the same.

The high Qts omits the need for high EQ in the low end, but price to pay for that is weak magnet.

I sold my Alpha 15a soon after I found the bass to be one-note!
 
Thank you for your swift Reply Mikkel! I was thinking using an inexpensive woofer like:
vervangingsspeaker 15 inch kopen? - Elektronicatekoop.nl

or a GRS like this one:
GRS 15PF-8 15" Paper Cone Woofer
GRS 15PF-8 woofer kopen - SoundImports

Not the best for open baffle im sure but close enough and the combined cone area should compensate for low bass response quite a bit.

Made a quick sketch:
View attachment 965809

Gr, Mike

I would go with the GRS 15PF-8.