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Sunfire/Boston Acoustics Frankenstein Experiment

13647 Views 35 Replies 10 Participants Last post by  princeseva
Hi all,

I've never really though about building my own home sub until the last couple of weeks ( looking at some of the builds here really propelled me in that direction ) The biggest motivator was the voice coil coming apart from the spider in my Sunfire MKII sub..a real downer. I was going to buy another driver, and that got vetoed by my better half, so I thought about sending my current driver out for repair but couldn't decide.

I have a Boston SPG555 car subwoofer in 1cu/ft, 3/4"MDF sealed enclosure, that I built in a hurry without any care other than it was sealed well ( read: it's ugly :dumbcrazy:). This sub was pretty impressive when I had it in my car, it was the best sub that I had owned after owning a multitude of car subs from my younger days..I really did forget just how impressive:R

It will handle 1000w RMS, and as mentioned, fits in a 1 cu/ft sealed box, and has more surface area than a 12" sub.I really wish I had the know-how to use the specs in the manual to custom design a box for this particular build. Since I don't, I though I would experiment with whatever I currently have at my disposal. Here is the sub:

I decided to hook up the Sunfire amp to the Boston sub, I was a little worried at first because of what I'd read about the circuitry in the amp/crossover/voice coil work together utilizing the high back EMF of the Sunfire woofer's monster magnet. The boston has a large neodymium magnet, and so I thought 'why not ?':scratch:

..and I tried it:bigsmile: At first at low to medium volume, and soon enough, I turned it up. I was pretty shocked with the result, it was louder and tighter than the MKII..unfortunately, I now have a few annoying vibrations in my room that this sub brought out:R . In fact, some music that never sounded right with the MKII ( Tupac, some metal music ) all of a sudden sound great, and the speed of a fast kick drum in metal music has never hit so hard and fast as it does now. I really loved my MKII, and didn't want to ever part with it, now I'm rethinking that idea.

Well yesterday, I had the day off and decided to try phase 2 of this experiment. I took the passive radiator out of the Sunfire, and put it on the opposite side of the boston. I was a little worried that this may be taking things too far, because I really don't know anything about designing a sub box, especially one with a round passive radiator on an oval sub:coocoo: ( if somebody is willing to help with this, please post here ). I also lack tools/space to build a decent enclosure.

Here's the MKII beside the ugly block:

After trying it, it appears to be a good move. I don't have a db meter or test equipment ( yet ), so I used the db meter on my iPhone, and I gained just over 3db on my phone:scratch: It also seems to play lower frequencies louder than just a sealed box( not sure if this box is still considered sealed ? ) Yet it's still tight.

The sub amp volume is turned down lower than before( a couple notches lower than midpoint ) but the thing seems louder than ever before, and my room has less nulls, where before, the bass relied heavily on proper placement because my room has a strange ceiling design. I decided not to fix the Sunfire, and instead build a nice enclosure for my Frankenstein setup instead. The only lingering question, can someone design an enclosure that would better exploit the full potential of my equipment ? I'm sure there is, and I hope they aren't shy about posting, you're help will be appreciated.
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Well the new box is finally built. We ended up making 1.5 cu/ft instead of 1. I haven't painted it or put legs on it yet. It sure looks better than the old hack-job box I had before.

It's 2 layers thick all the way around. The inside box is 3/4" plywood, and the outside is 3/4" MDF. I decided to leave the plate amp off for a couple of reasons..but mainly because it's one less big hole in the box, making it more sturdy. The other reason is less vibration on the Sunfire amp, which I will mount to the wall or somewhere else, which will also have the added benefit of better cooling ( not that it needs it really, but it can't hurt ).

I've been experimenting a little before I put legs on the box. Normally, as you all know, the sub/radiator are side-firing. I decided to experiment with a down firing setup instead. I'm not sure how high I should make it, so I've been adding 'layers' ( hack-job again, until I find the ideal height ), and living with the height adjustment to see how it sounds, then I add another 'layer', rinse, repeat:big smile: Not the fastest way to do it, and certainly not the smartest.:unbelievable:

My question to my fellow Shacksters..is there a certain height that a down firing sub should be away from the floor? Does it depend on the area of the cone ( 555 sq/cm )? Also, should the active driver be facing toward the floor, with the radiator to the ceiling, or vice-versa, or does it matter? I currently have the active driver facing down, and it seems to work great. It shakes the floor, the couch, the walls, and my body, and the bass is tight for music. For what it is, it's quite intense.

There's a couple of problems that come with this intensity. This sub used to dance across the floor when the woofers were firing side-to-side..now it bunny-hops instead getting up to 1" of vertical air time. I first noticed this when watching Ender's Game, it was a scene about 1 hour into the movie, I noticed movement from the corner of my right eye, when I looked over at my sub, it was hopping around and moving side to side. When I try and hold it down against the floor, then the floor starts to rattle and thump. I wouldn't want spikes on this one..

The sub is located at the front right corner, near my front-right BP10 tower. The pressure is causing my BP10 tower to vibrate and shake, and hop slightly. I didn't know that this was happening until I put my hand on it one day and I could really feel it. I am quite happy with the sound though. I just need to know how high to make it so if anyone has an answer, please share.

Here's the box:

Now I need to build a 3rd sub..I've been reading about Dr. Earl Geddes, and I'm convinced about what he has to say ( even though I don't understand most of it..I'm just not smart enough, still trying to learn what most members here already know )
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Does anybody have any suggestions on how high the legs should be, or does it even matter( I'm assuming it does ) ? I'd like to get this box painted up, but can't do that until I decide on the legs. Another question I'm curious about is wether the active drive should face up or down? If someone can lead me in the right direction, that would be fantastic. Thanks in advance.
So nobody has any suggestions? Tough crowd :D
Thank-you for replying..I just measured and it's currently sitting at about 3 1/4", maybe I'll go higher. I wasn't sure if there was an actual 'optimum' height I should be aiming for. Thanks again.
When your ready to sell your boston subs and radiators let me know. Are there any of those radiators left from the place you bought them from?
Sorry my friend, I can't see me selling this sub..I actually wouldn't mind getting another one :bigsmile: It's a pretty impressive unit when coupled with that amp..I still haven't gotten around to learning how to use REW, but I really want to learn how to use it. The last time I used it was to check the new calibration file on my Umik mic..I set my master volume to -15, which matched what I saw on my laptop screen using REW, so I assumed that the file is correct.

As far as availability for the radiators, I couldn't tell you for sure if they have them, but I know that they had to get them shipped from Japan ( I think that was what she told me ), and I had no trouble getting 2 of them at the time.

I want to build a 3rd sub, and try Geddes's sub setup method. The friend that told me about Earl Geddes has also been in Earl's personal theatre and was blown away by the sound, and the whole thing was running off of an inexpensive Pioneer receiver, from what he told me..that made me perk up and listen, and since then I've been looking up information on Dr. Geddes, and his speakers/methods. Now I'm saving my pennies in hopes of buying 3 Nathan speakers before they aren't available anymore...wife is gonna kill me soon:paddle:
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Wow, it's been a long time since I posted on this forum, and a lot has happened since. The biggest change was my wife and I bought another house, with much better room for my HT room, and an attached garage. It's a 4 level split built in the 60s, with the lowest level dedicated to my HT/sound room ( read: NO WAF required, only considered :T )

I'm in the process of renovating my old house so that I can list it for sale, until then, my HT room build can't start. This doesn't mean that I am living in misery without my system lol. I mocked it up in the new room a few days after moving in lol. After all, I have to figure out where everything will be placed best before my build commences.
I'm also eagerly waiting on my 3 GedLee Nathan speakers which I'm guessing will be here in a month.

On to the sub, this thing has been nothing short of amazing in it's performance and output, it baffles me and my other HT friends, all who are running bigger subs than what I run in my setup. One friend runs 2 PSA 15", and the other has 4 -21" in 27cu/ft sealed enclosures. I'm not sure what brand but they're built in Winnipeg. I run this sub( approx 13" ), along with an SC4000( 8" )which I'm going to sell and buy or build 2 cheaper subs at some point, and a 12" Sound Dynamics sub that I bought on Kijiji for 75 bucks lol. I also had a ported JBL 10" ( again kijiji, $75 )sub but the amp died when watching the movie 9. It sounded good until that night lol. All my subs are sealed, and I will stick to sealed subs from this point on. Ported subs( cheap ones anyway ) seem to have more potential for failure at high levels. I refuse to buy another 1K+ sub again though, I'd rather buy 5-$200 subs for the money (* assuming you have the room for multi subs * )

I'm also now convinced that as long as you have one great subs( by that I mean, plays deep and loud enough..like this Boston ), the other subs you add only need to be decent subs, they need not be expensive to get fantastic bass as long as you have 3 or 4 of them. I'm also convinced that they should all be different from each other, many might argue those points, and I respect their point of view of course, but I'm quite convinced on these points after tinkering for the last 6-7 months with setup.

The bass I'm experiencing is far beyond what I ever expected in a home, especially when I added the miniDSP into the mix. Not only do I have more bass than the other rooms I frequent in town, it's also tighter, more accurate and quite even throughout all the seating/listening positions. This sub being the main sub, placed in the front right corner ( 3 cement boundaries ). I've basically setup my bass loosely following Geddes' method ( one corner sub, one on the opposite side wall mid room above centre point, and one at the rear, close to the middle of the rear wall), BUT, I haven't did any measuring with the mic during any of my setup, it's all by ear/tactile feel..it will shake your clothes walking around anywhere in the room, and even at low volume I feel the bass in my sinuses and brain lol. So my apologies, as it's all subjective at this point. I came from car stereo bass, so I know what intense bass is like..I actually can't stand car stereos anymore..you really miss a lot of bass frequencies in those boomy setups. My friend with the 4 -21" subs just shakes his head and says, my room has the pressure of some car stereos, yet its dead on accurate. I'm just as baffled as he is. I expected his 4 21s to peel the skin off my face. He has about the same amount of bass, maybe a little less, but he's lacking in different bass frequencies..it still sounds good, just not the same.

I should add, I like my bass on the hotter side, but not over-bearing..I also like my transients and details. I may take some measurements when my Nathans arrive, but until then, I'm just too busy, and there's really no point because everything is going to change ( CLD/resilient channel damping ) when the room build starts, I will measure just to see what the change does to the room. I don't use EQ ( Audessy etc )for any speakers, and haven't EQ'd the subs, just band limited them with varying slopes and overlapped them.

My front towers are running in 'Large', and the subs are all bandpass filtered via miniDSP, and are all overlapped, overlapping into the mains. The bass is fantastic, for music-any genre I've tried-, for movies it's downright scary..I've given my self near-heart attack on movies that should scare a child, but the unexpected impact of bass ripples through the couch, my clothes, and the carpet which is on cement. This Boston sub is worth it's weight in gold. Even my friends with the bigger subs are scratching their heads as to why my bass is the way it is. I always had big bass, but applying the multi sub 'mic-less-loose-Geddes' sub setup has taken my bass to a level I was hoping for after my room was built and damped lol! The best is yet to come for this room.

This sub can still be found on eBay for under 500 bucks, I'd love to buy a second one for a spare, because I certainly don't need to run 2 at once..It gives the structure of my house a real workout, 2 may cause some issue down the road. I know I have a couple of new cracks in the drywall in the kitchen/living room doorway right above my room..as my wife was quick to point out one afternoon..I really have to get my room structurally damped to hopefully avoid that from happening..that's up in her territory:R She doesn't mind the cups and dishes rattling away, but the cracks made her take notice.
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It's the Boston SPG555 car sub. I'm powering it with a 2700 watt Sunfire plate amp that came off of my MKII sub. it's 555sq/cm and shaped like a Nascar track. It comes apart ( I have a spare voice coil, which take maybe 10 minutes to change out without having to remove the driver from the cabinet. I have the 4ohm version.
Ok I thought it was bent from the photo! That makes sense.
I should add..the sub is rated for 1000watt RMS, 14lb Neo magnet, 3.5" voice coil
Ok I thought it was bent from the photo! That makes sense.
LM*O! that's hilarious!!:rofl:
I started gathering my parts for this exact build December 2013. I had the Sunfire 2700w plate and 2 Boston SPG555 Subs. Both are 2 ohms. I didnt know about this site or I would have built along with you.
Since that time I have gathered even more parts and pieces and I have yet to put anything together. I now have a collection of Boston 3 G5 10s, 1 G512 and 4 soft parts kits for the 10s. I have a smaller Sunfire Jr and wanted to take the build to a slightly smaller scale with the G5s. (I have teens that dont have a sense of how much things cost when stuff breaks)
Post an update on the set up and let me know if you have made changes or updated anything.
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