# Repurposed monkey coffins!



## fusseli (May 1, 2007)

Edit: skip to post#24 for final crossover and impressions!

About five or six years ago I was given some old Fisher STV-723 floorstanders. They had beat up drivers (3" & 4" paper tweet and mid, woohoo) and didn't sound good to say the least. I started my first DIY endeavors by dropping in new drivers and other Xover experiments. They got to a relatively mature state a year or two ago, with a bona fide 3-way Xover (PCD 7), cab tuning and choice drivers. The problem being they looked like old cabinets that had been hacked up. To complete the overall project and avoid constructing new monkey coffins, my limited tools don't really yield good big cab construction. The following were done to transform the old cabs: New vinyl, New terminals, New vent, 1" rubber feet, 2x4 bracing, some acoustic foam lining, New baffle!

*The Xover had been designed around this driver spacing and z-offsets, prior to actually making new baffles. Drivers: Dayton RS28A, Dayton RS150S, Dayton DC300.

The old, *cringe*, pic taken at some point with other drivers and dropped in. Don't have a pic of the original drivers (square frames & white cones).









Imagine that sinking into shag carpet...


----------



## Zeitgeist (Apr 4, 2009)

Great re-use of an old cab.

Do you have some new pics that you'll be posting?

How does it sound?


----------



## fusseli (May 1, 2007)

Not bad for just a jigsaw, rotozip, and power drill 









Old cab prepared to accept new baffle. Yes, the midrange chamber is a 2.5L paint bucket siliconed on and stuffed with polyfill. Hey. It works.


















Old vs. new layout









Paint is Rustolium Fine Texture Black. I almost with it kept the gloss it had while wet!









Prior to baffles being glued & screwed









Dried to a subtle satin sheen









Close up showing paint texture









Testing on a PV900 and graphic EQ. Results... Couldn't be happier. Low low bass and the amp starts soft clipping before the drivers start distorting.


----------



## Zeitgeist (Apr 4, 2009)

Wow! Talk about a world away.... Looks great!

That looks like it would have some woofage. 

Glad to hear it worked out so well.


----------



## fusseli (May 1, 2007)

Haven't made grills yet but the guides are in place on the baffles. Here are Xover details, final response should be roughly a 85.5dB speaker +/- 2.5dB, solid 8 Ohm load. Full BSC via RL shelving circuit. Intent there being that these are fully functional by temselves in a fullrange setup with EQ. However I am using them currently as my mains crossed into a sub.

True 3-way, before BSC:









After BSC:


----------



## robbo266317 (Sep 22, 2008)

That is an impressive way to restore an old pair of cabinets.
What are your impressions of them? (The top end looks like it is rolled of a little.)

Cheers,
Bill.


----------



## fusseli (May 1, 2007)

robbo266317 said:


> That is an impressive way to restore an old pair of cabinets.
> What are your impressions of them? (The top end looks like it is rolled of a little.)
> 
> Cheers,
> Bill.


I think they sound great :T According to the FR it could probably use a treble bump, but I haven't tried any yet.

Ya the less than perfect response is a side effect of the design process of this particular Xover. It was made flat without baffle considerations (essentially IB), which was my own mistake a year or two ago. Then BSC compensation was added as a seperate series leg. Not the ideal way to go but it certainly functions beautifully.

I'm sure it would have been possible to get a flatter response designing an all new Xover, but that won't be happening haha. These are a done deal as far as I'm concerned. Untill a driver fails or soemthing that is! haha then maybe it'll get a redesign.


----------



## bambino (Feb 21, 2010)

Very nice looking rebuild. Probly saved a ton of time having the cabinets allmost completely ready to go. Again fine job.:T


----------



## fusseli (May 1, 2007)

bambino said:


> Very nice looking rebuild. Probly saved a ton of time having the cabinets allmost completely ready to go. Again fine job.:T


That was the goal, all the way! Why build cabinets when lazy me just has to make some baffles :neener:


----------



## bambino (Feb 21, 2010)

fusseli said:


> That was the goal, all the way! Why build cabinets when lazy me just has to make some baffles :neener:


Nice. LOL! I like your way of thinking.:devil:


----------



## GranteedEV (Aug 8, 2010)

They look absolutely great!! I think big woofers are the way to go, for that critical 100hz to 300hz region that subwoofers don't cover.

I've been thinking of saving up and doing something extremely similar with some sealed sony monkey coffins i've got, albeit with added bracing/damping/peel n seal and aggressive baffle edge roundovers. I'm thinking of taking a miniDSP and bi-amping

Fountek NeoCD3-v2
SS Discovery 10F
+
JBL W12GTI (or the current, and surprisingly-decent 12" sony woofers)

not that I really modeled anything.

The main thing I would do differently from your build would be to seriously offset the midrange and tweeter for mirror pair rather than center them to hopefully reduce diffraction and improve imaging - not quite sure how significant any audible advantages would be of course.

Of course, this would only be a temporary solution, until I build a custom enclosure mimicking a Salk Soundscape. :devil:


----------



## fusseli (May 1, 2007)

Offsetting the mid and tweet would reduce the amount of ripple introduced by the baffle since different distances to different baffle edges won't contribute at the same frequencies. A wide baffle (such as this one @ 14") also reduces effect of edge ripple, same with rounded edges. I couldn't decide on a layout that didn't look funny to me with them off center, so I centered them :yes: The difference in FR is minor, especially on a wider baffle.

Good luck with your build!


----------



## GranteedEV (Aug 8, 2010)

fusseli said:


> I couldn't decide on a layout that didn't look funny to me with them off center, so I centered them



I dunno, i think offset drivers above one huge driver look sweet:










:hsd:


----------



## fusseli (May 1, 2007)

Wowzers. You would need speakers that big to fill a castle ballroom with sound haha


----------



## GranteedEV (Aug 8, 2010)

nah, it's for mid-field monitoring at low levels










:spend: :whistling: :innocent: 

I would suspect they have some serious vertical lobing issues at the listening position but maybe because they're active they use really high order slopes.. or something... not sure. Regardless, they are one of my favorite monkey coffins... though they're big enough to fit more than one monkey.


----------



## fusseli (May 1, 2007)

Hahaha ya they are pretty cool looking. I'm sure they are optimized for power response similar to PA speakers, since the listener is rarely directly on axis.


----------



## Seaxe (Sep 13, 2008)

G`day, fussili, excellent re-use of "monkey coffins". I did the same thing about 6 yrs ago. Had apair of John Bowers Active 1`s. These active (and expensive) speakers were on thier way out. So I purchased the Madisound Solist kit, and retrofitted this to my cabinets. I did not build according to instructions, using a sealed MMT, instead of an ported MTM setup. That said, and allowing for BSC, I could not be happier. The JB Active cabs, together with my custom stands simply could not be discarded. With each large stand mount cab plus stand weighing in at 190Lbs, these Scanspeak puppies are here to stay. I must add that the retrofit took many months of calculations to discover what would work. Again congrats on making a working project. Cheers Mike.


----------



## fusseli (May 1, 2007)

fusseli said:


> After BSC:


Gonna address that taper in the highs afterall after realizing how easy it is to do. Just have to add a 8.2uF cap to the BSC stage (RL to RLC), which will pass the highs un-attenuated. The BSC shelf is more of a BSC notch now 

Old response in the overlay.


----------



## gvimhoof (Aug 25, 2009)

Very nice! Like the old school look of the finished project. Let us know how the new BSC works!

later,
G


----------



## fusseli (May 1, 2007)

Did some sweeps in-room @ the listening position, no EQ or anything. The left channel is right by a door so that should explain some of the mismatch. FR doesn't look too bad and they sound great. Useful bass down below 20Hz without a sub, though it is a fairly small room.


----------



## Alex2507 (May 10, 2008)

I'm going to make speakers out of real human coffins and see how cute you guys think it is.
Really ... can he just say monkey coffins like that? 

Those do look pretty sharp. It would be pretty cool to design something like that around like a Bose 901. 
They show up a lot needing new surrounds. Too bad I don't know anything about speaker design. :neener:


----------



## robbo266317 (Sep 22, 2008)

I was playing around with transmission line designs that had slanted sides. One of my mates saw them and said - Why have you got two coffins in your lounge room? :rant:


----------



## jvinhj240 (Aug 18, 2012)

amazing job


----------



## fusseli (May 1, 2007)

Almost forgot to update, I re-hacked the crossovers a couple months ago to try and get the best possible results regardless of complexity. I used my WT3/DATS to measure and model true T/S params of the mids and woofers as well as get true .zma of each pair of drivers. Acoustic slopes are 4th-order Linkwitz-Riley across the board. Results are phenominal, big change in sound over the previous crossover, I honestly wasn't expecting much since it's still the same drivers but it turned out to be hugely noticeable. The load is easily "4-6 Ohms" now, but that's no issue for my A500 amp.


----------



## robbo266317 (Sep 22, 2008)

The theoretical response looks really good, which is confirmed by your subjective results.

Do you have any Baffle Step compensation in that circuit? I couldn't see any. (mind you I have not gone back to see what size cabinet you are using either :whistling


----------



## fusseli (May 1, 2007)

I have 4dB BSC factored in, that was done in the initial steps in Response Modeller, before going to PCD  Meaning I designed the xover to be flat, as observed, with 4dB BSC in place. Factoring it into the xover doesn't require a separate BSC circuit. The 4dB idea being that a floor-stander in a big and open room will sound full and powerful. It worked for the most part, they sound flat.


----------



## robbo266317 (Sep 22, 2008)

fusseli said:


> I have 4dB BSC factored in, that was done in the initial steps in Response Modeller, before going to PCD  Meaning I designed the xover to be flat, as observed, with 4dB BSC in place. Factoring it into the xover doesn't require a separate BSC circuit. The 4dB idea being that a floor-stander in a big and open room will sound full and powerful. It worked for the most part, they sound flat.


I assumed you would have looked at the total system response. It was laziness on my part not to reread the whole thread. lddude:


----------



## fusseli (May 1, 2007)

It's all good :yes:


----------



## 3dbinCanada (Sep 13, 2012)

Nice set up. Excellent rework on the cabinets.


----------



## Zeitgeist (Apr 4, 2009)

fusseli said:


> It's all good :yes:


So what's the final verdict?

Love them? Like them?

Anything you'd change?


----------



## fusseli (May 1, 2007)

Verdict?

3-ways are complex but quite a nice feat to pull off. The DC300s (12" Dayton Classics) aren't known for particularly low distortion, but they handle midbass so smoothly and effortlessly. The A500 amp I power them with has been bench tested and is proven good to around 180W @ 4 ohms... the amp goes into clipping before distortion is audible :bigsmile: I think the weakest link in my Monkey Coffins could be the voice coils on the RS150s burning up if played rediculously loud for hours on end. Even that's hardly a concern since they only cover three octaves of the spectrum (roughly 300-2400Hz). All in all they sound amazing and I couldn't be more content. The latest LR4 xover is here to stay.

The only thing I would change is that I would have done the midrange chamber differently/better. It is a 2.5qt plastic bucket that I have lined with grey acoustic foam and fully stuffed with acoustastuf. My thoughts is that the volume is on the small side, but okay since it actually helps a high Q for the RS150S which made the crossover easier to design. The downside is that the bucket is so narrow it doesn't leave much clearance around the shielded magnets. Once I get a measurement rig going I will be sure and post measured FR.


----------



## fusseli (May 1, 2007)

Oh and another thing I would do differently is I would have offset the midrange and tweeter on the baffles. I decided not to when I cut the new baffle because I was more worried about looks at the time and I liked the look of the four black circles inline on the baffle. I could have gotten rid of a 1-2dB hump in the modelled upper midrange had I offset the drivers.


----------



## GranteedEV (Aug 8, 2010)

fusseli said:


> Oh and another thing I would do differently is I would have offset the midrange and tweeter on the baffles. I decided not to when I cut the new baffle because I was more worried about looks at the time and I liked the look of the four black circles inline on the baffle. I could have gotten rid of a 1-2dB hump in the modelled upper midrange had I offset the drivers.


Rather than an offset - why not a waveguide? 

It'll correct the diffraction (since offsetting tweeters doesn't correct diffraction - it just changes the way the diffracted sound sums and nulls) and also improve your power response.

... not that you really need to do much anyways. But it could probably let you keep your current baffle too.


----------



## fusseli (May 1, 2007)

Those look pretty slick. For something like that I'd definitely like to take measurements and redesign the xover as needed. Unfortunately I don't have much for a measurement rig... yet! I'm more focused on making a significant AVR upgrade at the moment.


----------



## Dale Rasco (Apr 11, 2009)

Man Russ, awesome work! I can't believe I haven't seen this thread sooner!


----------



## fusseli (May 1, 2007)

Minor upgrade, re-wired them for biamp capability and lined the backs with vinyl dampening. Each is now getting 2x125W from my NR818.


----------

