For The Record This Box Is Still Undergoing Tests

Looks A Little Better Carpeting, Wouldn't You Say?

[QUOTE]Originally posted by Elliot Thompson
[B]Quote:
The box SPL @ 2.83 volts, 1 meter will be 108 dB from 100Hz - 24.3 Hz (+/- 10 dB)

Elliot,

Nice project. I hope you know that the plus or minus ten dB you post as an efficiency window is huge. This is the exact same range as saying, " I'm building an amplifier and the output is either gonna be 1000 watts or it could be 10 watts." dB's are funny that way. Hope it works out well. Keep us posted.

Rob

OOPS! In attempting to reply to Elliot's post here I accidentally hit the 'edit' button instead of the 'quote' button just next to it and in the process appear to have erased one of Elliot's posts, the one I was trying to reply to. Please forgive my fumbling Elliot. Would you please be so kind as to re-post?

Once again my humble apologies.

Rob
Fumblefingers DIY Moderator

The box is siliconed, and, screwed together

The box dimensions are 37.5 x 20 x 25.5

The box uses two 18mm baffle boards to hold the drivers

The box bass port is located in the rear to eliminate port noise

The box will utilize one Beyma Driver, (Top) and, one JBL (bottom)

The box frequency response will be 100 - 38Hz (- 10dB @ 24.3Hz)

The box SPL @ 2.83 volts, 1 meter will be 108 dB from 100Hz - 24.3 Hz (+/- 10 dB)

Not my favorite sounding box, but if your into punchy bass, you'll
love it. The overall cabinet size is 11.07 cubic feet.

Originally posted by Rob
[QUOTE]Originally posted by Elliot Thompson
[B]Quote:
The box SPL @ 2.83 volts, 1 meter will be 108 dB from 100Hz - 24.3 Hz (+/- 10 dB)

Elliot,

Nice project. I hope you know that the plus or minus ten dB you post as an efficiency window is huge. This is the exact same range as saying, " I'm building an amplifier and the output is either gonna be 1000 watts or it could be 10 watts." dB's are funny that way. Hope it works out well. Keep us posted.

Rob

Hello Rob.

I made an error putting +/- 10dB. I should've said 108 dB @ 100 Hz, and slowly declines to 90db @ 24.3 Hz using 2.83 volts, 1 meter.

To be honest, its more of a High Output box. I generally make
Extended Low Frequency Enclosures.

The VAS on these drivers are high, and to achieve the extension, I would need to use a 32 cubic ft box.(internal) Even for High Fidelity Bass, it demanded a 23 cubic ft box.(Internal) For High Output it required an 8 cubic ft. (internal) box. So, once you deduct the drivers, cabinet thickness, bracing, and ports, it gets around 8.49 cubic ft internal.

This box is Actually one of my Double Fifteen cabs, I converted
to a dual 18. My main Double Eighteens have a 18 cubic ft. (External) box, and the woofers have a far lower VAS requirment.

Hello Elliot

Bet that can move some air! Nice box What about the rest of your set-up?? Is that an HT sub? What are you driving it with??

Rob2:)

Hey!

I see you put Rob2 to prevent some confusion :)

Boy, am I glad you did! :D


I feed it around 1200 watts (600 a driver) As I mentioned earlier, its more punchy (100 - 60 Hz) than extension. I'm a sub low fanatic, so its used mainly for Low Mids - Mid Bass.

I told gonefishin, I was going to post some pics of my setup on the weekend. This was the only picture I had in my computer
so, I figured I would post this on the DIY Board today.

Kind of hard to explain what I have, so, I let the picture do the talking this weekend.


Oh,

The Speakers are Beyma 18 LX 60, and JBL 2241 H

Best Regards,

Elliot

Elliot,

Thank you for re-posting. That clears up the dB's thing. I see you like big drivers, large cabinets and lots of LF. 18 inch drivers can move a lot of air. I made a ported enclosure with two 18s in it about 10 years ago that worked very well but wasn't all that large in internal volume. I still have it pushed up against the wall in the laundry room but borrowed the drivers to make a cold cellar infinite baffle subwoofer with the drivers mounted in a reinforced solid door for the home theater. I think the drivers worked better in the small box than the 280 cubic foot concrete enclosure, because I could 'move' the box to where it worked best. I cannot move my cold room. I don't use this subwoofer now as my new full-range hombrew horns sound better without it. I like my bass tight and fast, not boomy or sloppy.

Keep us posted. That 108dB efficiency at 100 Hz is something I'm looking for now in a new speaker design. I don't need the SPL's at high power, but rather the efficiency for low power SET use.

Rob

Hello Rob. :)


I focus mainly on 15, 18, 21, and, 24 inch drivers. However I do have a few 12's that I consider rather good, and will give you
around 90 db's (Single driver)

I ran a quick design using a 12 inch driver in a 5.251 (Internal)
cubic ft enclosure, and got 90.6 dB @ 100 Hz and slowly declines
to 70 dB @ 11.3 Hz The box is tuned to 19.15 Hz, and has - 3dB
@ 22.76 Hz

If I tune the box to 25Hz, you will stay flat at 91 db from 100 - 28.5 hz. At 70 dB, your looking at around 13.5Hz. (This would be the best of both worlds. Efficency, and, High SPL)


If this sounds good to you, I can send you the driver
parameters, enclosure dimensions, and, where you can get the driver.

Since I use 8 ohm drivers, you can get two of these units, and
have your bass extension even lower. The driver is a
PA Speaker, so you will get high SPL guarantteed! :)

Not to mention a 13mm Xmax (one way) it will handle anything
you can throw at it.

Remember these measurements are 2.83 volt (1 watt since its one driver) 1 meter.


If you feed it lets say 100 watts (Worst case scenerio) your looking at 107 db's flat from 100 - 21.9 Hz(Lets call it 22Hz)

BOX TUNED TO 25Hz

200 watts = 110 db 100 - 22.8Hz

400 watts = 113 db 100 - 23.7Hz

Originally posted by Elliot Thompson
Hello Rob. :)


...I ran a quick design using a 12 inch driver in a 5.251 (Internal)
cubic ft enclosure, ...
If I tune the box to 25Hz, you will stay flat at 91 db from 100 - 28.5 hz. At 70 dB, your looking at around 13.5Hz. (This would be the best of both worlds. Efficency, and, High SPL)


Elliot,

That performance sounds quite good, but I'm trying to better that efficiency by a large measure (need over 100 dB/1W) starting at a higher bass frequency and using multiples of smaller 8" drivers. Loudspeaker design like everything else in engineering is a compromise. In the search for a design that will work better than most at one to five watt power levels I will be happy with 'apparent', bass down to 35-40 Hz for my new design. This is indeed a challenge as I'm trying to do this without going the proven by adhering to physical laws, real estate intensive, materials expensive route of a huge horn. I am approaching the problem instead through the experience I bring to speaker design from my past work as a microwave antenna engineer. In radio science the horn is the standard high performance antenna which is absolutely predictable and used often as a calibration reference. The physics is generally the same for acoustical problems and antenna techniques work equally well in speakers, hence horns, lenses, waveguides, all microwave radio terms being seen in modern audio literature.

I would be interested in any ideas you might have in this direction and we could communicate via PM if you'd like.

Rob

Hi Mike,

BTW, check your private mail (PM) I sent over a week ago to you.

You have the ballpark efficiency I desire in my quest but two things are wrong for my design criteria. One is that you need too big a cabinet volume for my application.

I accept that your single bass bin in the near field would sound good, however I believe that time delay is also critical in the bass region and this makes separate subs more often than not an unacceptable compromise for a true Hi-Fi system. It is why I don't use my sub after all the trouble I went to to build it. Subs and HT is another matter entirely IMO and the same rules as to Hi-Fi do not necessarily apply.

Actually I'm surprised that you don't get enough bass from your neat speaker shown as your avatar. This is essentially a bandpass cabinet using a Karlson coupler as a way to increase the bandwidth and de-Q the tuned output port yes?

Rob

Hey Mike Nice Sub. :)



Hello Rob :)

I don't mind using PM Messages. The only drawback I've experienced with PM Messages, is their 1000 letter limit.

We can exchange Emails, or we can continue this on the board.

I really need to know;

What's the largest box you will consider.

What kind of power your using.

What's the largest driver you will accept.

What speaker companies that are readily available in your country.


Elliot.

Elliot,

PM word limit is a big pain in the ass. I'll PM you my phone number and email address.

Thanx,
Rob


Originally posted by Elliot Thompson


Hello Rob :)

I don't mind using PM Messages. The only drawback I've experienced with PM Messages, is their 1000 letter limit.

We can exchange Emails, or we can continue this on the board.

<snip>
Elliot.