Starting my first speaker design

[Dabspok]

Ok first attempt at the woofer part of my speaker design. Bottom of speaker is going to have 4 Peerless 831735"s. 4.6 cu ft/130 L vented seems awfully big. Am I missing something? Or is that correct?

[PWR RYD]

Re: Starting my first speaker design

That's just Unibox throwing out a suggestion. There are endless alignments possible, so that suggestion isn't necessarly the "best". I haven't done anything with that particular driver, but 4.6 cubic feet does seem kind of big. You need to decide how big, how loud, and how low you want and then play with box size and tuning to find an design that meets your requirements.

[50 watt head]

Re: Starting my first speaker design

You need to decide how big, how loud, and how low you want and then play with box size and tuning to find an design that meets your requirements.

+1

Important questions: Is this for music or HT (or both)? Will you be using a sub? How much power will you be using?

The 831735 sounds great sealed; four of them might be great in as little as 60L with good power handling and roll-off for HT mains. Just one possibility.

[Dabspok]

Re: Starting my first speaker design

These will be mostly for music. Loosely based off of Pete's Peerless design and the Elsinore.
Tweeter is Seas 27TBFC/G with a Dayton 6 1/2" waveguide, mid is 5 1/4" Peerless 832873, base is four 6 1/2" Peerless 831735. MTWWWW format to get the tweeter approximately listening height. Truncated edges will be against each other. Probably wired for bi-amping.

Initial baffle design.


Looking at my response in the box design, I wonder if I am trying to drive it too low. Maybe it should have a smother roll off on the bottom?

[Dabspok]

Re: Starting my first speaker design

Maybe this is better. I don't know if I am supposed to "optimise Fb for wanted peak"? Roughly 3.7 cu ft.

[Chris Roemer]

Re: Starting my first speaker design

Maybe this is better. I don't know if I am supposed to "optimise Fb for wanted peak"? Roughly 3.7 cu ft.

How does 34 Hz in 2.1 cf sound? That's what WinISD says, and I trust it.

Just use 2 woofers. You get the +6dB gain in sensitivity, same as with 4. Box size is halved. 4 cf is L - A - R - G - E in anyone's book. 6mm Xmax is a good amount of throw. 3"id x 6" port will do.

Chris

[Dabspok]

Re: Starting my first speaker design

These are the reasons I am working with the 4 woofers. I have eight 6 1\2" Peerless 831735, two 5 1/4" Peerless 8327873 and on the way are two Seas Seas 27TBFC/G, I'm sure its over kill. :D



Although the Paradigm Signature S6, Studio 60 and the Monitor 9 all are TMWW, not to mention Pete's TMWW above.

[mdocod]

Re: Starting my first speaker design

If uber SPL is not part of your game plan, you can tune/load these suckers right down to 20hz and get all the glorious movie rumble, and to be honest, music would still sound great on them because your port tuning and group delay will peak below most musical material anyways. If it's a fairly small room, there may be enough room gain to pull that 20hz response up to near flat anyway. Even vented tuned to ~20-25hz will still deliver better efficiency than a sealed box so it should be considered a valid option.

On the other hand, if 20hz response is not important to you for movies at all, and you would like to have more dynamic reach for music, tune a 2-4ft^3 box in the 30 - 35hz range. The smaller boxes will simply require more EQ and amplification to "shim up" the bottom end- depending on room gain characteristics. The 4ft^3 box tuned to 30hz will run out of Xmax at around 100W, a 2ft^3 tuned to 35hz will run out of Xmax around 175W. Try to align available amplifier power so that you can "reach" all of your available Xmax within your box design, leaving untapable Xmax on the table would be a shame.

Eric

[Dabspok]

Re: Starting my first speaker design

So 100 L roughly 3.5 cu ft, tuned to 30hz=

[bkeane1259]

Re: Starting my first speaker design

I got a 40Hz F3 in Jeff's WBCD in a 100L box. It seems like they want more space to hit really low.

Just bumping up the volume to 110L and tuning to 35Hz gives an F3 of 32.8Hz.

[mdocod]

Re: Starting my first speaker design

Throwing box space at the problem to get a better looking F3 is merely an efficiency thing. If you don't want to EQ the bottom end, then that F3 point may be important, but if you can some control over it (via EQ), then the F3 point is really pointless (even more so in most enclosed spaces). You can have nearly any bottom end extension (within reason) that you desire with that much woofer surface area, Qts, and Xmax. The trade-off is maximum SPL within the intended bandpass.

Don't just look at the predicted response curve, look at driver excursion relative to frequency relative to power input. There is a lot more to the final design than a response curve. The "F3" point is really only an important consideration in free space with no EQ and no loading below F3. You can have an F3 of 50hz with these drivers, yet still have useful loading to 20hz that will play louder than predicted in most rooms due to room gain anyways.

The front mains in our "living room/home-theatre" are 3-ways with dual 8" woofers each, with similar Xmax to the woofers you are working with, total displacement is actually nearly similar (yours would actually have more displacement capability)... I have them tuned to about 20hz via a single big nasty long throw 10" passive radiator (peerless XLS as I recall). If I recall, my F3 is something like 55hz, but they are "loaded" down to ~20hz (-16dB as I recall). In room, We have no real significant need for a sub. Just a bottom end bass boost (~+6dB) on the receiver and room gain takes care of the rest.

Regards,
Eric

[bkeane1259]

Re: Starting my first speaker design

I will add that in my sim, there's no filtering, no EQ, etc.

Just seems like the right balance is somewhere in that 3.5-4.0 ft^3 area, but closer to the larger enclosure. If bumping up the volume just a tad drags the F3 down that much (from 40 to 32.8Hz), I'd build the bigger enclosure.

I modeled with 100 watts and was under XMAX. Also used a 4.5" port and kept the velocity under 25m/s.

More than one way to skin a cat I suppose. The only thing is, it's very easy to EQ and very hard to build a different box.

[Dabspok]

Re: Starting my first speaker design

Bryan did you just change the port size and let the software resize the port diameter? I am getting 5-6" ports in my tries.

I have seen that these drivers seem to really like more volume. Their xmax is only slightly longer than the standard 830875. Are there additional properties that make them want more volume?

I am thinking 3.5 cu ft is going to be a good compromise, and I can use some help understanding the port size. Seems like I am missing some charts that show port velocity etc. that would help.

Thanks!
David

[Chris Roemer]

Re: Starting my first speaker design

Bryan did you just change the port size and let the software resize the port diameter? I am getting 5-6" ports in my tries.

I have seen that these drivers seem to really like more volume. Their xmax is only slightly longer than the standard 830875. Are there additional properties that make them want more volume?

I am thinking 3.5 cu ft is going to be a good compromise, and I can use some help understanding the port size. Seems like I am missing some charts that show port velocity etc. that would help.

Thanks!
David

If either Vas or Qts go up, so does box size. It's proportional to Vas, so upping that by 10% (say, from 2.0 to 2.2) increases the box by 10%, but a 10% increase in Qts (say, from 0.40 to 0.44) can increase volume requirements by a LOT more, like 25%.

Chris

[Dabspok]

Re: Starting my first speaker design

There are so many variables to these projects. It reminds me of setting up race car suspensions and engines. But my brain was younger and quicker then. Thanks Chris!