Build Thread: "The Fatbelly's"

[mzisserson]

Finally after several months of toying with the deaign, I am building it!

I wanted a bookshelf speaker that could satisfy the monkey coffin guys, while being refined enough for delicate ears. Extended responce and dynamic impact, and power responce were the main focus of this one.

No 5" or 6" here. The Hivi D8.8 measure 9 5/8's in diameter, with a TRUE 8" cone size. X-max of 8.8mm as well. This is not a Budget speaker, but one with a heck of a purpose. The D2604-83300 brings its "A" game too. 475Hz FS, Frequency responce to 40K (VERY flat to 20K), and controlled impedance with no breakup. Take a lookie:



They need to look the part too, squat and powerful. The bass responce represents an approximate "Q" of .78 giving a 1dB bump around 55Hz, an F3 of 40Hz and F10 of 30Hz. 4dB of baffle step and a very soft transfer function on the tweeter smooths out the transition. The diffraction matches the soft crossover which ultimately will assist the tweeter down low. At 50Wrms sine input, the woofer does not exceed x-max until 23Hz, avaraging 102dB from 38Hz on up. It is good with 100W to 28Hz outputting 108dB as well. Vent velocity does not exceed 19m/s. All in a Mere .625ft3 (15x11x12.5).

Here's the sim:




And Build progress:







There will be more "triangle" braces from all surfaces as well as the one you see. The walls will be lined with sinic barrier, and the cabinet will be stuffed. The ports will actually be two of the 1.5"x4"-ers glued back to back to make a dual flare 8" long port.



More to come...

[Brewski]

Re: Build Thread: "The Fatbelly's"

I'm gonna have to check those out on my next trip down or at DIY NE :D
Hard to believe how deep those cabs are. It's looking good though.

Take it easy
Jay

[[email protected]]

Re: Build Thread: "The Fatbelly's"

nice build.

[Taterworks]

Re: Build Thread: "The Fatbelly's"

Finally, a speaker design that's inspired by me! :D

Use those D8.8's with a powerful amp. Their 4" voice coils can handle gobs of peak power. I can't wait to see how they turn out. You're way past driver selection, obviously, but I would have looked at pairing one of the Wavecor 1-1/4" dome tweeters with that midbass, because it would probably put up well with the low crossover frequencies the D-series and DG-series drivers demand.

I was going to get a design going based on the D5G, but one of the first two drivers I ordered had a VC rub, and then when I ordered a replacement, the replacement was sent two per box, but the two drivers I received were both physically different (the newer-production units had voice coil perforations, and the older-production units did not), and I learned that in the course of going through those drivers, I'd gone through PE's entire stock, and no more could be expected until May. Blast.

[r-carpenter]

Re: Build Thread: "The Fatbelly's"

Hey Mike.
Nice design but couple of questions.
Are you talking about power vs distortions of a loudspeaker or vertical and horizontal response? Because the response that Scan shows https://www.madisound.com/store/manu...00-feb2011.pdf isn't so hot in terms of off axis (I am assuming it's 0,15,30 fr).
The other thing about big monkey coffin speakers, is that they do sound big and the presentation is different. So, no matter how nice your bookshelve will be (and I am sure it'll be great) it will not present the music the same way.
Anyhow, bring them to next NY DIY whenever that may be?

[mzisserson]

Re: Build Thread: "The Fatbelly's"

Finally, a speaker design that's inspired by me! :D

Use those D8.8's with a powerful amp. Their 4" voice coils can handle gobs of peak power. I can't wait to see how they turn out. You're way past driver selection, obviously, but I would have looked at pairing one of the Wavecor 1-1/4" dome tweeters with that midbass, because it would probably put up well with the low crossover frequencies the D-series and DG-series drivers demand.

.

Tweeter selection was a tough one. I like to keep em' as small in diameter as possible. From the testing I have done on the tweeter alone, it handles a lot of power and stays well behaved. I ran a 475Hz tone though it at 90dB for nearly an hour (wife was not a big fan) and the thing just belted it out with no audible distortion or issues. At the time I only had an RTA which will not show everything, but we will see! Can you link to those wavcor's? I admit they made it under my radar...

My amp is a biggun' they are not ment to be driven with flea-watts or anything of that nature. It was something I was willing to sacrifice. The D8.8 acts more like a good subwoofer than a woofer in a lot of ways I am amazed. I used the 5.8 in a smaller bookshelf called The Reds. The 5.8 shocked a lot of people (including myself) with how smooth it sounded in the mids and robost the bass was.

Hey Mike.
Nice design but couple of questions.
Are you talking about power vs distortions of a loudspeaker or vertical and horizontal response? Because the response that Scan shows https://www.madisound.com/store/manu...00-feb2011.pdf isn't so hot in terms of off axis (I am assuming it's 0,15,30 fr).
The other thing about big monkey coffin speakers, is that they do sound big and the presentation is different. So, no matter how nice your bookshelve will be (and I am sure it'll be great) it will not present the music the same way.
Anyhow, bring them to next NY DIY whenever that may be?

Hi Roman,

As a rule of "design thumb" I like to use, I like to keep tweeter nasties above 15K. They look ragged off axis, but I do not believe it is telling the whole story from when I mocked them up in a baffle. I will have good measurements once they are complete of the design. They fall off off-axis, but not as awkwardly as the mfg specs show.

Believe me... The Beasties have all of that presence you are refferring to. I am sure as a bookshelf, they will not quite be able to get completely there, however they should capture some presence and dynamic impact given the large woofer size and the capability of the 8.8. I am not a dreamer, they will not replace a Monkey Coffin, but if a monkey coffin owner can nod their head and say "nice work", I hit my design goal.

Speaking of which, when are you planning the next event? :D

[lunchmoney]

Re: Build Thread: "The Fatbelly's"

Looks great Mike!

Previously the design called for a dramatic tweeter offset... what changed?

[r-carpenter]

Re: Build Thread: "The Fatbelly's"

Believe me... The Beasties have all of that presence you are refferring to. I am sure as a bookshelf, they will not quite be able to get completely there, however they should capture some presence and dynamic impact given the large woofer size and the capability of the 8.8. I am not a dreamer, they will not replace a Monkey Coffin, but if a monkey coffin owner can nod their head and say "nice work", I hit my design goal.

Speaking of which, when are you planning the next event? :D

I need Founteks to finish my line array and Madisound isn't going to have them for... I am guessing another month. So, by the time they will get the tweeters, by the time I am done with the work. Me thinks August if everyone is ready?

[mattp]

Re: Build Thread: "The Fatbelly's"

Very cool Mike, I'm glad someone else is putting the larger format HiVi's to use, you don't see that too often. You mentioned using the 5.8, have you had any experience with the 6.8? I'm currently working on a three way (think the Tarkus look) using the D8.8+, D6.8 and XT25. Just looking for some input on the midrange quality of the 6.8.

I cant wait to see these done! I'm a huge HiVi fan.

[billschu]

Re: Build Thread: "The Fatbelly's"

Interesting about waiting for the Foundteks. I'm still waiting for Madisound to get the C173-6-095E Accuton drivers back in stock. Might just have to go with Scan Speak Illuminators.

I need Founteks to finish my line array and Madisound isn't going to have them for... I am guessing another month. So, by the time they will get the tweeters, by the time I am done with the work. Me thinks August if everyone is ready?

[ligs]

Re: Build Thread: "The Fatbelly's"

D 8.8 drirver is a really handsome driver. The similarity between D 8.8 and Dynaudio 21W-54 certainly is striking. The cone of 21-54 is made of magnesium silicate filled polypropylene. In commone language, it is also a form of mineral filled polypropylene.

http://www.gattiweb.com/images/dynaudio/21w54_data.pdf

I am looking forward to read more about "The Fatbelly's"

[johnnyrichards]

Re: Build Thread: "The Fatbelly's"

Big bang in a little box. Looks like a heckuva speaker, Mike.

[johnnyrichards]

Re: Build Thread: "The Fatbelly's"

By the way Mike, is that the 1/2" chucked Craftsman 19.2V drill? I have the same drill. I like the drill, but the batteries leave a little to be desired. Just threw another one away last night.

[billschu]

Re: Build Thread: "The Fatbelly's"

Mike let me hear a hacked together wired up mock-up. He's got a pretty good start. I like the drivers he chooses.

I'm probably going to use the D10.8 sealed in a three way this summer just based on the 5" and 8" versions I heard. I have a feeling the slow rolloff of this driver combined with room gain is going to work really well in my listening room. Hoping for an Accuton 6.5" to go with it.

Bill

D 8.8 drirver is a really handsome driver. The similarity between D 8.8 and Dynaudio 21W-54 certainly is striking. The cone of 21-54 is made of magnesium silicate filled polypropylene. In commone language, it is also a form of mineral filled polypropylene.

http://www.gattiweb.com/images/dynaudio/21w54_data.pdf

I am looking forward to read more about "The Fatbelly's"

[mzisserson]

Re: Build Thread: "The Fatbelly's"

Looks great Mike!

Previously the design called for a dramatic tweeter offset... what changed?

The new cab dimensions made it so I can center the tweeter, putting the 1-2dB of diffraction to good use at the x-over point. It allowed me to dip the tweeter slightly lower at x-over to compensate for any boost due to the diffraction signature.

Very cool Mike, I'm glad someone else is putting the larger format HiVi's to use, you don't see that too often. You mentioned using the 5.8, have you had any experience with the 6.8? I'm currently working on a three way (think the Tarkus look) using the D8.8+, D6.8 and XT25. Just looking for some input on the midrange quality of the 6.8.

I cant wait to see these done! I'm a huge HiVi fan.

I am too! Hivi drivers are a very good value. I know wolf loves the M series. Never used the 6.8, but the 5.8 and the 8.8(so far) have great midrange with a lot of laid back resoultion. Not sure of the 6.8 would make a good mid only because I have found the D series to be "true" woofers, not midwoofers. It would work fine, but I would think something like an AC130 might make a better mid for that setup letting the D8.8 doo all the bass/midbass glory.

By the way Mike, is that the 1/2" chucked Craftsman 19.2V drill? I have the same drill. I like the drill, but the batteries leave a little to be desired. Just threw another one away last night.

It is! My sentimates exactly. I have two batteries. It has a lot of power, when it runs.