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Started and finished another audio project yesterday afternoon in 5 hours flat!


chops

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Sat night, 9pm:

So I decided to do something with the two spare Dayton 15DVC drivers I had sitting around (1 used, 1 new), so I built a push-pull subwoofer to save space and still get max output and extension. After driver and brace displacement, I'm guessing it's about 6.3 cu.ft. sealed from it's original 6.59 cu.ft. It's a 24" cube. It's not the prettiest thing, but certainly sounds darn good!

Sun, 1pm:

So once I figured out what I was doing for a sub, I went up to Lowes with my "other" brother and his SUV to get the 4x8 sheet of .75" MDF and have it cut there to my specs. I'm just tired of building all of my projects with a stinkin' jig saw all the time, hence why I had them do the cutting. I was expecting to pay $30 or so for the wood and cuts. The MDF was $20 and there were about 7 or 8 cuts @ $.50 each.

The guy that was helping me was the department manager. He was a little light in his loafers too, if you know what I mean, but he was pretty cool and funny as hell. Anyway, he said he hadn't used that vertical saw in a while, and he made a couple of mistakes, being about an 1/8" off on a couple of cuts. So he ended up giving me the 4x8 sheet and all the cuts, plus corrected the cuts for a grand total of $10!! All because he appreciated us being so patient with him!

2pm:

We get back home and I start measuring out the voids to cut out of the brace and the driver motorboards. I then ask my brother jt1stcav to give me a hand in cutting and assembling the cabinet.

6pm:

After a lot of drilling and screwing and siliconing, and lunch break, I wire up and install the drivers (both VCs wired in parallel for 4 ohms on each driver) and connect them to the amp.

Between 6-8pm, I clean up everything, eat dinner, play several different choice CDs, then setting down around 8:30 or so for a movie... AEon Flux

According to one of the guys on the DIY Audio forum, he says that my sub should have a Qtc of about 1.0 and an F3 of 30Hz via BassBox software. Then when you consider the room gain (which comes on strong in my room below 30Hz), I'm getting solid clean output well below 16Hz.

Efficiency is another amazing thing about this sub. With moderate volume levels, the amp is only reading between 0.5 and 1 watt! When I'm really cranking the volume with some of my CDs or in the movie last night, the meter only reached 30 watts and peaked 50 watts once or twice, and it was loud as heck in here. Louder than I would normally ever play my system. I would really love to know what the actual efficiency of this sub is. I'm thinking that it's maybe up there around 100dB or so.

The amp I'm using is an old Technics SU-8099 integrated that was bought

back in 1979 with the Cornwalls new. It's rated at 115W @ 8 ohms per ch

and 180W @ 4 ohms per. I have the drivers wired to a 4 ohm load to each

channel of the amp and have the sub line-out on my receiver going into

the "Main In" on the SU-8099 which bypasses ALL tone and volume

controls. Right now, it is nothing more than just a two-channel amp.

Plus its freq resp is rated down to DC (0Hz) for the first 5 watts or

so!

I was thinking about getting a Samson Servo 600 amp to put 600 watts into this sub, but now I'm not sure I even need it. And I think I can safely say that this sub outperforms my old SVS PB12-ISD/2 that I used to have, even when tuned to its 16Hz setting.

I know this thread should probably be in the "Subwoofer" section of the forum, but with all the stuff going on down there right now, I'd rather not have to go there.

So with that all out of the way, on with a few pictures... of course! [:P]

IMG_0452.jpg

IMG_0454.jpg

IMG_0462.jpg

IMG_0468.jpg

IMG_0473.jpg

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i too am using an old receiver to power my sub, but it's very quirky..

i can't get good output unless i connect it to the phono inputs on my receiver.

if i connect it to the cd input, i have to literally turn my receiver volume up 100% to get output. i can't figure out why, and it drives me nuts.

i also have tape in/outs but i haven't tried those. been using phono for now, but it's not too clean.

any suggestion on an inexpensive subwoofer amp (preferably not plate.. i don't want to have to modify my enclosure again) i can pick up? don't need much power.

sub is a 12" adire audio shiva using the plans for their 80 something litre sealed enclosure.

thanks.

-chris

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how are these wired ?

The drivers have dual 8 ohm coils. I wired the VCs in parallel for 4 ohms per driver total. I am powering each driver with one channel of the amp. It's a 2-channel amp, one driver per channel.

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Nice job. You do good/quick work. How did you have the time with all the BOSE Cannon debate going on?

LOL

Come on people, let's not crap up this thread now.

And to answer your question jacksonbart, I am quite capable of multitasking.

Please, let's stay on topic.

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Nice job. You do good/quick work. How did you have the time with all the BOSE Cannon debate going on?

LOL

Come on people, let's not crap up this thread now.

And to answer your question jacksonbart, I am quite capable of multitasking.

Please, let's stay on topic.

How did you handle the cross over or are you sending the full signal over? How does it work if both speakers are powered, vs say a passive speaker, doesn't it cause an issue if both are powered and in phase? Not being a smart @ss just trying to learn.

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How did you handle the cross over or are you sending the full signal over? How does it work if both speakers are powered, vs say a passive speaker, doesn't it cause an issue if both are powered and in phase? Not being a smart @ss just trying to learn.

The sub is crossed over at 50Hz via the subwoofer output on my Pioneer Elite receiver. I'm not sure if it's a 16, 24, or 36dB crossover or not though.

A passive radiator is nothing more than a tuned port, without actually being a vent. The drivers are in fact out of phase being that they face away from eachother.

At the very bottom of this page, it gives you a good explination of the push-pull concept. This has been the design choice of M&K subs for years, since 1989 with the introduction of the MX 2000...

http://www.danmarx.org/audioinnovation/theories.html

http://www.mksound.com/timeline.htm

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some food for thought

i took a look the links...great links...but do you have a hybrid (both woofers installed normally, magnet inside the cab, wired normally) or are you actually installing one of the drivers back-wards as the web site explains...or are you reversing the wiring on the rear woofer assuming it is also installed magnet side in as the front?

what i am curious about...if really set up as push pull...since you show woofers facing left and right rather than front and back...the speaker nearest the invertedly phased woofer (mounted back wards as push pull shows, or wired backwards) would interact in such a way as to cancel out a portion of the lower end closest to the operating frequency of the sub woofer.

if there is any substance to this concern...with some further tweaking...sound potential might be more awesome than the current wireing config.

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some food for thought

i took a look the links...great links...but do you have a hybrid (both woofers installed normally, magnet inside the cab, wired normally) or are you actually installing one of the drivers back-wards as the web site explains...or are you reversing the wiring on the rear woofer assuming it is also installed magnet side in as the front?

what i am curious about...if really set up as push pull...since you show woofers facing left and right rather than front and back...the speaker nearest the invertedly phased woofer (mounted back wards as push pull shows, or wired backwards) would interact in such a way as to cancel out a portion of the lower end closest to the operating frequency of the sub woofer.

if there is any substance to this concern...with some further tweaking...sound potential might be more awesome than the current wireing config.

Yes, both drivers are mounted facing away from eachother. As far as some bass being cancelled between the one phase inverted driver and the K-33 in the CW, I don't know if that's an issue or not. They are both crossed over at 50Hz, so...

This is what you're talking about, correct?

Here's a couple pics showing both sides...

IMG_0471.jpg

IMG_0470.jpg

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that was the question.

but since chops said they are not wired special, then they are in phase....they both push the same direction with the same signal applied (they both go outward together...and inward together).

the web site chops provided introduces a few types of speaker arrangements...the one that caught my eye was the picture with the woofer in the rear mounted backwards (I would imagine the same effect if you just wired the rear one backwards). discribed as push-pull.....with the same signal applied...the front woofer sends waves into the listening area...the second woofer sends waves into the cabinet (towards the rear of the front speaker). under this senerio....depending how close and what in direction the out of phase woofer was...it could cancel out some program at the lower end of the closest speaker...if a gentle slope xover was used.

I did some playing around with dual speaker subs a few years ago and found, in spite of the info in the web-site...that the speakers sounded louder the way chops discribes his subwoofers are connected....rather than the phisical out of phase approach or electrically out of phase connected approach.

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that was the question.

but since chops said they are not wired special, then they are in phase....they both push the same direction with the same signal applied (they both go outward together...and inward together).

the web site chops provided introduces a few types of speaker arrangements...the one that caught my eye was the picture with the woofer in the rear mounted backwards (I would imagine the same effect if you just wired the rear one backwards). discribed as push-pull.....with the same signal applied...the front woofer sends waves into the listening area...the second woofer sends waves into the cabinet (towards the rear of the front speaker). under this senerio....depending how close and what in direction the out of phase woofer was...it could cancel out some program at the lower end of the closest speaker...if a gentle slope xover was used.

I did some playing around with dual speaker subs a few years ago and found, in spite of the info in the web-site...that the speakers sounded louder the way chops discribes his subwoofers are connected....rather than the phisical out of phase approach or electrically out of phase connected approach.

Okay, you guys are starting to comfuse me. LOL

So you are saying that I have it where both drivers are working against eachother, both pushing in towards eachother then away from eachother? I think it's supposed to be as if both woofers are physically attached to eachother, and move in unison. [:^)]

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Ok, first of all your current configuration (regardless of wiring) is

not a push/pull configuration. You simply have two drivers sharing the

same sealed cabinet. And you want to wire the subs such that both

drivers create a positive pressure on the outside of the cabinet at the

same time. If one driver is moving in while the other is moving out

then you will end up with a lot of cancellation and all you will be

hearing is distortion. The whole reason we need cabinets in the first

place is to keep the rear wave away from the front wave.

I have attached a graph that shows your predicted output.

Green = a true isobarik configuration

Blue = your current configuration

The SPL's shown are with 50W of input. The sensitivity for green would

be a peak of 88dB and blue would be a peak of 94dB (6dB loss when

moving to isobarik). Green has an F3 of 40Hz with a Q of .531. Blue has

an F3 of 44Hz with a Q of .781.

If you could post the dimensions of your room and how well you think it

is sealed we can calculate what your performance after room gain might

look like.

post-10350-1381929825459_thumb.gif

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