Meet the LGK Fourtress

Peter J · « **on:** 13 Jul 2014, 03:04 am »

Just put together a prototype cabinet that will use 4 LGK drivers which I'm fixin' to send Danny so he can evaluate it's potential. This is a configuration he suggested and I drew some time ago, but I've been swamped and didn't get it built till now. Might be a pretty cool design, as he said, "it should image like crazy".

Started here, side hidden so you can see the innards

Here's the proto, I made the back removable on this one to allow gerfingerpoken, but final design would have removable bottom for internal access...much cleaner looking. Also will need plinth or outriggers for stability.

Captainhemo · « **Reply #1 on:** 13 Jul 2014, 06:45 am »

Interesting design Peter. Looking forward to reding some test results after Danny has had a chance to test. How low are you guys expecting these to play in a ported config like this ?
Have you got the drivers/ports on hand ... are you going to get a chance to listen to them before you send them off ?

-jay

Guy 13 · « **Reply #2 on:** 13 Jul 2014, 07:41 am »

Hi all.
Are the LGK supposed to be extended range drives?
Because, Danny said at one time that it's not recommended to put side by side
two extended range drivers.
Please explain why in this case it will work ?
Thanks.

Guy 13

Jonathon Janusz · « **Reply #3 on:** 13 Jul 2014, 01:08 pm »

I'm not Danny, but I've seen other designs cross over both the lower driver and or the rear firing ones at various frequency points such that only the top, front driver is playing full-range. My guess is that the lower front driver is there to increase cone area in the lower midrange, and the rear drivers are intended to provide ambiance by changing the dispersion pattern in the room?

Neat design! I think the lower driver count and straightforward box design will make for a nice, competitively priced kit once the sound gets sorted out. The big, elaborate kits are cool for sure, but there is something to be admired in keeping things simple sometimes, I think.

Another configuration I got to wondering about after looking at yours is an omni - on driver firing up, one firing forward?

Peter J · « **Reply #4 on:** 13 Jul 2014, 01:49 pm »

Jay, just a single cabinet for now to evaluate viability. If that looks promising, a pair will be next. I have a couple of LGKs here for fitting, but they for sure will need a network. I'll (necessarily) leave that to Danny, I'm the wood guy...

Jonathan, I believe you're right about how they will be networked. I imagine Danny can shed more light there as well as anticipated frequency response. Interestingly enough, this design sprang from a conversation with him about substituting LGKs for the no-longer-available drivers I used in this project;

http://www.audiocircle.com/index.php?topic=103789.0

Should be interesting, I'll update here as things progress.

ebag4 · « **Reply #5 on:** 13 Jul 2014, 03:18 pm »

Very nice Peter. I have not yet seen an actual LGK driver, I seem to be having trouble getting a sense of scale. I imagine these cabinets are 4.5" or less based on other designs I have read about using these drivers. Would you mind letting us know what the dimensions are on this mock up?

I can see this potentially morphing into a slender tower with an 8" sub firing out the side at some point.

Best,
Ed

Peter J · « **Reply #6 on:** 13 Jul 2014, 04:03 pm »

Ed, indeed the size is visually deceiving on these, they are small in stature. 4 1/2" x 8 1/2" footprint, 37" high. When and if this evolves into a viable speaker, I'll detail the cabinet a little more and make the SketchUp model available to anyone that wants it.

CD case gives a comparative sense of scale.

ebag4 · « **Reply #7 on:** 13 Jul 2014, 04:13 pm »

Quote from: Peter J on 13 Jul 2014, 04:03 pm

Ed, indeed the size is visually deceiving on these, they are small in stature. 4 1/2" x 8 1/2" footprint, 37" high. When and if this evolves into a viable speaker, I'll detail the cabinet a little more and make the SketchUp model available to anyone that wants it.

CD case gives a comparative sense of scale.

Haha, thanks Peter. The pic on the table and the CD case definitely help with the scale, they are tiny for a floorstander. I look forward to reading about how these perform and what frequency ranges they will cover.

Best,
Ed

persisting1 · « **Reply #8 on:** 13 Jul 2014, 06:46 pm »

Clever name

mlundy57 · « **Reply #9 on:** 13 Jul 2014, 07:42 pm »

Peter,

Verrrrrryyyy Interesting.

Mike

Danny Richie · « **Reply #10 on:** 13 Jul 2014, 10:24 pm »

Quote from: Guy 13 on 13 Jul 2014, 07:41 am

Hi all.
Are the LGK supposed to be extended range drives?
Because, Danny said at one time that it's not recommended to put side by side
two extended range drivers.
Please explain why in this case it will work ?
Thanks.

Guy 13

Like Jonathon said, only the upper driver on each side will play full range. The one right below it will be in series with the one above, but by-passed with a large cap. So in the lower range they both share the load but as frequency increase only the upper driver plays.

Guy 13 · « **Reply #11 on:** 14 Jul 2014, 01:52 am »

Hi Danny.
Thanks for the explanation, makes sense.
However, the lower driver will be more or less used as a mid-low woofer,
I wonder how it will sound since wide-range drivers are known for their limited excursion.
Anxious to read the final impression on sound.

Guy 13

Early B. · « **Reply #12 on:** 14 Jul 2014, 02:08 am »

Danny - can you create two crossover options --one for a stand-alone speaker and one with a steep drop-off so that a servo sub could handle the bass? The second option will alleviate all of the bass duties from the full range drivers.

Danny Richie · « **Reply #13 on:** 14 Jul 2014, 03:17 am »

Quote

I wonder how it will sound since wide-range drivers are known for their limited excursion. Anxious to read the final impression on sound.

Adding a second driver like this doesn't change the characteristics of how one sounds. With two drivers sharing low frequency duty the distortion cause from pressure on the cone is cut and half. So for the same volume level the lower region is cleaner. It also doubles power handling.

Then add a second pair to the back and you double power handling again.

And Guy, these little drivers have a pretty decent X-max for a little driver. 2.5mm each way.

Danny Richie · « **Reply #14 on:** 14 Jul 2014, 03:18 am »

Quote from: Early B. on 14 Jul 2014, 02:08 am

Danny - can you create two crossover options --one for a stand-alone speaker and one with a steep drop-off so that a servo sub could handle the bass? The second option will alleviate all of the bass duties from the full range drivers.

With a design like this there is more of an overlap range than a crossover.

What you are wanting is a high pass filter for the whole thing. That can be handled with an inline RCA style filter. So that's a piece of cake.

pslate · « **Reply #15 on:** 17 Jul 2014, 12:27 am »

This is very cool

Would love to see how things progress.

Mr. Oczka · « **Reply #16 on:** 18 Sep 2014, 02:27 am »

Danny,

Just curious how the testing on this design is going?

Thanks,

tom

Danny Richie · « **Reply #17 on:** 25 Sep 2014, 05:03 pm »

Quote from: Mr. Oczka on 18 Sep 2014, 02:27 am

Danny,

Just curious how the testing on this design is going?

Thanks,

tom

It morphed a bit to make it work out better. Here are the new drawings of the box. http://gr-research.com/pdf/Fortress%20box.pdf There might be a few little tweaks to the drawings still.

Peter's building out a pair of the boxes for me and he is converting the drawings into a 3D form.

ebag4 · « **Reply #18 on:** 25 Sep 2014, 07:16 pm »

I guess "Fourtress" is out, too bad, it was a catchy name.

Peter J · « **Reply #19 on:** 25 Sep 2014, 07:19 pm »

Aaaaaand.........Presto!