Pass SLOB Build Discussion

Yes this also use to confuse me.... but then my brain turned on.
20 to 80Hz is slow, but when you multiply that by the linear cone excursion at bass frequencies (being orders of magnitude greater than at higher frequencies of the mids and treble) the actual linear velocity of the cone is actually quite high. This is one point people haven't seemed to consider at all.

I also wonder about the apparent stiffness of a cone due to aspect ratio changes as you go up in diameter, ie to maintain structural stiffness, thickness would also need to be increased, affecting moving mass considerably, and if not accounted for I suspect higher distortion would be the result, fine for special effects in movies, possibly not ideal for music. This isn't something I have had a chance to personally test out though, so possibly (even likely) not quite right.

I'm certainly not disagreeing with you just sharing my own thoughts, except my definition of a subwoofer is sub 30Hz, certainly not as high as 80 Hz. I'm not a fan of getting super pedantic about sub 30Hz as it tends to create it's own problems ie everything that can resonate will resonate, doesn't sound nice at all if you have that scenario occurring.

Using my own logic I tend to agree with you, but when looking at the very clever ones, who actually know the math behind, and see their results then my logic also tells me to believe these guys.

My own experience also tells me that you need a lot of cone area, and if you dont't need to go high in frequency then one large woofer is better, than many small. It's easier for me to find a large woofer with low Fs, middle Qt, high Xmax and at a reasonable price than many smaller woofer. Many good quality small woofer is more expensive than one large good quality woofer.

I also think that one large woofer looks nicer, than a tower of four or six small woofers.
 
Using my own logic I tend to agree with you, but when looking at the very clever ones, who actually know the math behind, and see their results then my logic also tells me to believe these guys.

My own experience also tells me that you need a lot of cone area, and if you dont't need to go high in frequency then one large woofer is better, than many small. It's easier for me to find a large woofer with low Fs, middle Qt, high Xmax and at a reasonable price than many smaller woofer. Many good quality small woofer is more expensive than one large good quality woofer.

I also think that one large woofer looks nicer, than a tower of four or six small woofers.

For your requirements it certainly makes sense to do it like that. I agree if you're only covering a narrow frequency range things are quite different, than when trying to cover a broader range of frequencies.

I don't have a lot faith in mathematicians, I prove them wrong virtually every day at work. ;)
 
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Quick question if I may...

Since I'm OB oriented these days, how do you mount the drivers to the baffle?
Not needing to be sealed, but do you still add a gasket to de-couple the driver from the baffle, or do you mount the driver directly on the baffle to benefit from the added mass of the baffle?

My baffles are 5cm (2") thick.
 
Finalizing my layout this morning on milimeter paper, editing and combining those pictures takes longer

Using red meranti marine plywood 9mm with stacking 3pcs should be strong. Bottom slot, wings, and front baffle will be modular, connected by aluminium L plate 50x50x6mm. Front baffle 27"x45" will be separated into 3 sections in order to make easy FR & HF driver rolling.

2x ACR Fabulous 100185 18" subwoofer
Fostex F346 12" fullrange
Fostex FD600 & H500

I'm looking at some finished speaker as my reference for finishing, it seems sonus faber elipsa is fabulous :D wish me luck..
 

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Just visited Sinar Baja showroom in Jakarta, i was like a kid in toys store :D all Satori line up in the show case is so tempting to test but it was not my intention.

first objective to get 12" for mid, it was easy choice to choose this one which has neo magnet, nice cast frame
12? PA- 75124 W-N FABULOUS BY ACR | ACR Speaker

However it was hard to pick which sub for my OB, after testing some 18" and 21" then absolutely my choice is 21"
21″ PA 113212 SW FABULOUS BY ACR | ACR Speaker

this beast with big oommmpphh on free air, 18kg weight, strong magnet, seems perfect. might need to buy another pair in next few month.

12" neo is $315/pair, 21" is $440/pair

now my 20" wide baffle seems tiny and those entry level 15" woofer might not be used anymore.

it's time to build 30" wide baffle and bottom slot loaded
 

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From my understanding, the shorter, the better... whether it's active or passive.

If you are going for longer cables, you'd want to use something thicker, to reduce the resistance coming from the length of the cable. Resistance will build quickly in thin wires over length.
 
Speaker Cable Length

Speaker cable size relative to length is something that should be experimented with because conventional rules of thumb are not always correct.

Here is a case in point. I put my Lowthers on open baffle using the Dick Olsher Basszilla design. Someone mentioned that he tried using 28 guage magnetic wire with his Lowthers and found that there was a noticable improvement. I tried this and my results agreed with that person's claims. My speaker cable (magnet wire) run lengths were about 8 feet.

There are different theories why this is so. Lowthers are very efficient have a very strong magnet and can produce a large back EMF back to the amps which can affect the amps ability to work effectively. The high resistance magnet wire maybe helps to reduce that back EMF - at least that was an explanation given which made some sense.

In my case, I am using single ended tube amps with Lowthers and other amps and other speakers would have a different interaction.

My advice would be to try different speaker wire and use what works best.
 
Enjoy the building, probably the most exciting part (IMHO)
Yeaa 100% agree :D

bought my first jigsaw, trimmer, sander and started cutting wood. watching youtube guide for dummies woodworking help alot. since i'm afraid to use circular saw, and table saw is not an option, i have to cut with jigsaw first (extra 3mm) and clean up with trimmer. takes time but precise cut. making those flush mount hole was also a big challenge

my original plan was to make 3 separate panel and connect them with aluminium L plate, but later i think that making them into 1 panel should be more solid. now i have to glue 1by1 since not many clamp that i have. it will be repeated with 2nd layer to make 2x18mm plywood. still long way to finish.

it's fun for me, but not for the family members. loud noise and dust on backyard should be compensated with my wife lovely hand bag and my twin boys want extra toys too :D
 

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already in shape now, just tested those 21" with gainclone, eventhough had given extra bass boost on windows setting and wmp equalizer, it seems it requires an amplifier with extra muscle. while my laptop dont have enough gain to drive aragon2004. another adventure to get proper amplifier, maybe i should build PA amplifier with 1kW rating.

testing 12" mid and horn with passive 2nd order filter @1.6kHz with class a amp gives me another AHA moment :D

need more weekend to complete them
 

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