New Project for Critique...

**meb46** · 10 January 2012, 01:59 Tuesday

Hmmm... seems like my embedded imagines didn't load in correctly or I got some thing wrong.

Any moderator fancy fixing my error and embedding my images... please please?

Cheers

**JonMarsh** · 10 January 2012, 08:50 Tuesday

Originally posted by meb46

Hmmm... seems like my embedded imagines didn't load in correctly or I got some thing wrong.

Any moderator fancy fixing my error and embedding my images... please please?

Cheers

Your image links were referencing on your hard drive. The way it works is to upload the image, then click on those links and open in a window and right click on the graphic to copy the image address, or copy it directly (some browsers don't like doing that from the link- go figure). Then use the image icon in the tool bar and paste the link of the uploaded picture in.

**---k---** · 10 January 2012, 10:33 Tuesday

It looks beautiful. Very ambitious. The crossover will be the make or break deciding factor. I can't really see a way to improve it.

**Paul W** · 10 January 2012, 11:31 Tuesday

Looks like a great project. The only thing that comes to mind is making the side walls a bit stiffer by adding either horizontal or vertical braces from the side walls to the middle of the central window braces.

A lot of us will be watching this build!

**Bear** · 10 January 2012, 11:36 Tuesday

It looks like the back half of the upper cabinet is open to the lower cabinet? You may want to consider that space for the crossover location if you aren't already. Also, if you want to go really crazy with the mid chamber, consider making it deeper to give you more room to damp the rear wave.

**---k---** · 10 January 2012, 15:59 Tuesday

Originally posted by Paul W

Looks like a great project. The only thing that comes to mind is making the side walls a bit stiffer by adding either horizontal or vertical braces from the side walls to the middle of the central window braces.

A lot of us will be watching this build!

I thought about that too. I thought the back was getting about 2x the bracing as the sides... but the box is getting braced every 12". Should be good.

Originally posted by Bear

It looks like the back half of the upper cabinet is open to the lower cabinet? You may want to consider that space for the crossover location if you aren't already. Also, if you want to go really crazy with the mid chamber, consider making it deeper to give you more room to damp the rear wave.

I figured two separate boxes for the upper and lower would be a LOT easier to construct.

I also thought people wouldn't like the port location directly behind the driver and/or firing into the base without a big space shown below the base.

**cjd** · 10 January 2012, 17:05 Tuesday

Looks like a ton of fun.

Cooking up something that seems to be leaning toward a classic Avalon look myself (it'll have a nice warm'n fuzzy sound characteristic I suspect, though still pretty low distortion, so I figure that may be about right...) - finally gonna use the OW1's I have had for... 5yrs?!

I'll agree on the mid-box size - rear-wave cancellation/management seems to be rather important, and I'm not sure the somewhat shallow box will do it justice. A simple angle on it may help, as will some wall treatment, but... if you really need the extra volume in the lower chamber, will an extra cm or two in depth really hurt that much? I'd just leave the upper as a separate box entirely. The extra volume will not hurt the mid.

C

**Generic George** · 10 January 2012, 18:25 Tuesday

If you are going for a design of this level of cost and complexity. Especially as you are not an experienced crossover designer. I would strongly recommend at least trying out some sort of active crossover. It makes "testing" your crossovers, much simpler (just changes in software) and does offer possibilities that are very difficult to implement in physical crossovers. If nothing else it should make zeroing in on what you want the crossover to be much simpler.

I'd look at the MiniDSP probably the 4x8 version. You will need one amp channel per driver (possibly only 1 for the woofers depending on how you wire them).

**meb46** · 10 January 2012, 20:58 Tuesday

Some great advice guys... much appreciated...

As I sat dwelling on things last night preparing to start and draw up the 2D plans, I was reconsidering the top box design. Daunted by the sheer number of different shaped panels and the fact that the two boxes needed to be sealed to make the top cabinet effective... I was thinking it maybe time to simplify things... your words of feedback come at the perfect time

The rear of the top box is open to the Bass Unit to add in around 12 Litres to the total Bass Cabinet Volume. I think CJD is right, and perhaps a few cm's in depth may simplify the design back to a traditional two box set up and also gives me a place to put the Crossover up top. Consider it amended.

The Mid range enclosure is where things get complicated as I have varying sizes recommended from 2L up to 12L. According to Accuton, the driver is pitched as follows;

2L enclosure - F -3 = 160Hz, Q=0.71
4.5L enclosure - F -3 = 170Hz, Q=0.50

Hence I was trying to get the actual volume down to wards 4.5L or lower. With the rear of the cabinet no longer required for additional Bass Cabinet Volume, I maybe able to create a deeper enclosure, but I was still wanting to keep the volume to under 4.5L... unless someone has a strong argument for making this larger in volume?

Side panel bracing... I was relatively confiden that the overall horizontal bracing should be up to the task, but I had considered putting in a couple of "Rib like reinforcers that run vertical only in the very bottom chamber... still to decide...

The entire cabinet will sit on adjustible feet that will then let me tune and set the Port... I have yet to decide if this is going to include a plinth or not...

Will start and knock out the model for this revised version later this evening...

**Hdale85** · 10 January 2012, 21:20 Tuesday

Why not load up the driver specs in some modeling software and figure out where the FR looks right in which size box.

I'd be curious of the effect of the woofers and tweeter being further forward then the mid-range? Generally designs like this that I've seen the top box is slanted enough to make the top drivers flat in comparison to the bottom slant. Your's seem to actually go negative from the bottom slant and then slope forward placing the tweeter out a bit and also making the mid/tweeter face down somewhat. I'm not sure if that's a problem but I'd be curious to know?

I'd have to agree with going active if you're not very experienced with crossover design, a crossover for something like this is going to be rather complex especially if you get in the habit of trying to work out all the little quirks and go for a more complicated crossover network. Going active means you can change things on the fly and tweak it out completely until you get something that's flat in the FR and has the characteristics you like.

**bbcmp1979** · 10 January 2012, 22:36 Tuesday

Wow... i'm subscribing... Looking good btw.

**meb46** · 11 January 2012, 03:55 Wednesday

Right... amendments as follows...

1. Separated back into two separate cabinets, the opening in the base of the top cabinet is just to fit the crossover into (assuming its a passive one at this stage).
2. Bass Cabinet enlarged in overall depth to accomodate ~145L without the need for volume from the top cabinet. After speaker tapering and edge rounding this should increase to just over 150L.
3. Mid Enclosure ~4.8 Litres without Bitumen lining... should work out with a final volume after Speaker tapering and lining at around 4 - 4.5L. Enclosure lengthened for a more elongated shape and all walls of the Mid-Enclosure have been increased to 50mm thick. (Aids assembly and design simplicity). The empty cavity above the Mid Enclosure will most likely be filled with some kind of rigid compound... undecided yet.

And now for my first attempt at placing the pictures into the post properly...

**dlneubec** · 11 January 2012, 09:45 Wednesday

FWIW, here are some thoughts (see drawing).

As others have noted, you have some fairly large unsupported sections on your side panels that may resonate. Consider some vertical bracing that ties into your other bracing to break these panels up into smaller sizes.

Notice the lines with arrows. This is to indicate how you have a number of panels of almost the exact same dimension. This looks good on paper, but what it means is that if these panels resonate, they will do so at the same frequency. On the side panels, since you have two, that means you might have 6 panels of similar dimension and they will all resonate at the same time, with a much greater chance of being audible. It is better to vary the unsupported panel sizes throughout your box so that any resonances are spread out over a wider range of frequencies and are less likely to be noticeable.

As others have suggested, consider making your midrange box bigger and deeper. Assuming you are using and active or passive high pass crossover on the midrange and not relying on the box to create an acoustic high pass, then your crossover will control the low end response of the midrange, not the box, making the Q unimportant. A deeper, bigger box gives you much more chance to absorb reflections rather than having them hit the back wall and reflect right back at the cone. Also, if you taper the box, reflections are less likely and there is little chance for standing waves, since none of your panels would be parallel.

There is little need for the thicker members in your midrange cabinet, as long as bracing is adequate. This is going to be one heavy speaker as it is without adding unnecessary weight.

When choosing the angle of your MT box baffle, consider looking at the height and distance to your listening position and not just how it looks aesthetically. Typically the idea of sloped cabinets is to attempt to time align the drivers, so that they are equidistant from your ear. Say your LP is 37" high and 12' away. In your cad drawing, side view, create an arc centered on this point through the approximate acoustic centers of your drivers (for simplicity sake, lets say this is approximately where the voice coil connects to the cone at the center of the cone) and use this to align the drivers along the curve. This can help to determine the ideal slope of the upper cabinet baffle. Though not required and you may elect to go with aesthetic considerations instead, aligning the drivers could make the crossover design a bit easier to accomplish with less need for asymetric slopes and potentially fewer parts. This is not truly time aligned, but it gets you in the ballpark and likely closer than if you didn't consider it at all.

**---k---** · 11 January 2012, 10:47 Wednesday

Great advice.

**JonMarsh** · 11 January 2012, 11:56 Wednesday

Great ideas and feedback. Sheesh- I might have to move up my own build, with just dual 10's. But spare time? How do I find that?

I just suspect moving around an Isis Junior may be a bit easier... now which of the 10's I have to use? Scanspeak? Aurasound? Scanspeak Discovery?

**kraniet** · 11 January 2012, 12:40 Wednesday

nice project. Have you checked what kind of airspeed you get in the port? a single 10cm port seem a bit small for dual 12inch. In a 10cm port with god port endings (streamlined ends and with an internal "baffle") you should be ok with 10m/s port speed. Without proper port endings and the internal baffle youll only get half that airspeed before the air flow is all turbulent.

The port airspeed is linear to the diameter of the port. So in a good 5cm port you should get 20m/s without turbulent flow.
Proper loading for one 12 inch should be around 10cm port hence you should think about doubling the ports.

An alternative is to make a slot. A slot port can manage larger airflows without turbulent flow.

**Hdale85** · 11 January 2012, 15:37 Wednesday

If this project proves to be a success you may have to post the CNC files so I can cut my self a set

I may have to modify them a bit for the drivers I'd want to use (if you end up going active, or if I end up going active) as I've always wanted a set built like this.

**cjd** · 11 January 2012, 16:28 Wednesday

Originally posted by JonMarsh

Great ideas and feedback. Sheesh- I might have to move up my own build, with just dual 10's. But spare time? How do I find that?

I just suspect moving around an Isis Junior may be a bit easier... now which of the 10's I have to use? Scanspeak? Aurasound? Scanspeak Discovery?

Soooo, how 'bout if we went, say, Neo8 as the mid and maybe the Aurum Cantus AST2560 tweeter at the project? Oh yeah, that's one I have cooking in the back of the mind (I have the Neo8's to use since the open baffles will probably get the Neo3+Neo10 now.) At that point, if you can get the sensitivity in the woofers you could hit 92-94dB sensitivity. That makes it a little more interesting a game, and I haven't yet found woofage to make me happy. A quad of the 4ohm SB Acoustics 180mm drivers gets into the mid-low 30's (ported) at 92dB+ without going crazy insane big on the box. AE TD10(H or X) might be a good fit. Or back up to larger drivers and a more intricate box setup (for weight reasons.) Which brings me back around here.

If weight is beginning to be a real concern, consider thinner walls and MUCH more bracing (but also with much thinner material.) Construction could become a headache, but if you're going CAD and CNC it may not matter.

C

**JonMarsh** · 11 January 2012, 17:23 Wednesday

Originally posted by kraniet

nice project. Have you checked what kind of airspeed you get in the port? a single 10cm port seem a bit small for dual 12inch. In a 10cm port with god port endings (streamlined ends and with an internal "baffle") you should be ok with 10m/s port speed. Without proper port endings and the internal baffle youll only get half that airspeed before the air flow is all turbulent.

The port airspeed is linear to the diameter of the port. So in a good 5cm port you should get 20m/s without turbulent flow.
Proper loading for one 12 inch should be around 10cm port hence you should think about doubling the ports.

An alternative is to make a slot. A slot port can manage larger airflows without turbulent flow.

Good points- it all comes down to SPL targets- and also why I suggested by PM using Unibox for an LF analysis/modeling. 4" probably reasonable for dual 10's. Also, if you damp the enclosure internally some, reducing the Q and output of the port, then the port velocity issue subsides. Depending on room placement and boundary reinforcement, this may be something to consider.

**dlneubec** · 11 January 2012, 17:34 Wednesday

Originally posted by cjd

Soooo, how 'bout if we went, say, Neo8 as the mid and maybe the Aurum Cantus AST2560 tweeter at the project? Oh yeah, that's one I have cooking in the back of the mind (I have the Neo8's to use since the open baffles will probably get the Neo3+Neo10 now.) At that point, if you can get the sensitivity in the woofers you could hit 92-94dB sensitivity. That makes it a little more interesting a game, and I haven't yet found woofage to make me happy. A quad of the 4ohm SB Acoustics 180mm drivers gets into the mid-low 30's (ported) at 92dB+ without going crazy insane big on the box. AE TD10(H or X) might be a good fit. Or back up to larger drivers and a more intricate box setup (for weight reasons.) Which brings me back around here.

If weight is beginning to be a real concern, consider thinner walls and MUCH more bracing (but also with much thinner material.) Construction could become a headache, but if you're going CAD and CNC it may not matter.

C

Off topic...

I have a pair of AST2560's coming sometime soon (purchased and awaiting shipment). I may be pairing them with single and/or dual Neo10's (possibly open back, but not OB/dipole). In my case, since the Neo10 can get down to 200-300hz or so, I plan use an active low end to match woofer sensitivity when using dual neo10's, with maybe a 2.5way approach on the MTM. I'm also looking at the Transducer Labs N26C as an option as well as the Neo3, and waveguides are being explored for all three tweeters as well. :E

Looks like we are dabling with some of the same drivers, Chris. :T Now if I just had my garage shop back and an easy place to measure again!

BTW, thanks for the Neo3 dimensions. They are plugged in and I should have 4 waveguides in my hands to test soon. They will range in size from about 4.5"Hx6.5"Wx1" deep to 5.5"Hx6.5"Wx1.5" deep, each size with two throat angle configurations, one a 90º angle in the thoat where it matches the tweeter and the other with something closer to a 60º angle.

**dlneubec** · 11 January 2012, 17:41 Wednesday

Originally posted by JonMarsh

Good points- it all comes down to SPL targets- and also why I suggested by PM using Unibox for an LF analysis/modeling. 4" probably reasonable for dual 10's. Also, if you damp the enclosure internally some, reducing the Q and output of the port, then the port velocity issue subsides. Depending on room placement and boundary reinforcement, this may be something to consider.

Heck, depending on where in the room these are placed and whether the position of the woofers on the baffle is a bit flexible and could be lowered, a sealed pair of Aura 12's could be pretty hard to beat, once you factor in room and boundary gain. Then the boxes could probably get smaller, though I haven't modeled this driver to be sure of that.

IIRC, I looked at a pair of Aura 10's, sealed, with the bottom one pretty close to the floor and about 3' from the front wall or so and sealed in about 80-90l they looked darn good with room and boundary gain included.

**JonMarsh** · 11 January 2012, 18:18 Wednesday

Originally posted by dlneubec

IIRC, I looked at a pair of Aura 10's, sealed, with the bottom one pretty close to the floor and about 3' from the front wall or so and sealed in about 80-90l they looked darn good with room and boundary gain included.

Yeah, similar to my thinking and analysis. I've got to do something with the double pair of NS10's I have- it's just a big investment overall to make for something I don't have a backup set of drivers for.

**dlneubec** · 11 January 2012, 19:09 Wednesday

Originally posted by JonMarsh

Yeah, similar to my thinking and analysis. I've got to do something with the double pair of NS10's I have- it's just a big investment overall to make for something I don't have a backup set of drivers for.

Sounds familiar. I have 2 pair them to use as well, though I picked them up on closeout at $80 each, so that's not too much invested. They look so nice, I hate to hide them in a box. They would look great, rear mounted, OB.

I have yet to even measure mine. I bet you did yours. Mind posting your results or pointing out where they were previously posted? I'm wondering just how high they might be crossed if pushed.

**meb46** · 11 January 2012, 21:32 Wednesday

Wow... some really great feedback... Luckily my progress on the final Solidworks model is slow (compared to Sketch-up) so I can continue to make adjustments for another few days yet with your worthy feedback.

dlneubec - notes as follows:

The three chambers in the Base cabinet have some theory behind them. The main two that the woofers back into are identical but they also have the most bracing. I am realivetly confident they wont resonant (noticibly). They are machined in a way that should make the CNC easy/cheaper and should create exactly the same loading and impact on each of the woofers. The lower chamber is considerably larger. 370mm in mid height versus 300mm in the two main rear woofer chambers. However, as mentioned in my earlier post, I may but some ribs between the base and the first horizontal brace that is fixed to the side of the cabinet. This should provide further resistance against resonance. I will model in the ribs in the final solidworks model.

On the mid-range suggestion, It seems I now have mounting justification to enlarge this enclosure and the crossover point is valid. Let me have a re-think on that and see what I can model. Seems like the key volume suggestion is around 10L based on a number of peoples feedback.

On the angle/time alignment issue... this was already taken into account. When I first modelled the idea I was trying to design specifically for a seated position ~2.5m from the cabinet at about 0.9m height from the floor. At the time I modelled it with the drivers, using a combined woofer center (Mid point of the two woofers center points) and then the respective points of the Mid and Tweeter and came up with a diagram as you see below. This gave an approximate difference of around 11mm between all three drivers. Crude, but there was some method behind my numbers...

kraniet - notes as follows:

As I mentioned in an earlier post... or meant to if I didnt... the port will have flares on both the top and the bottom. THis will all be part of the tuning and measuring phase, but not modelled at this point. I am also thinking of some how securing the top of the port to mechanically protect it agaist vibration. THis will include some whizzy machined part the holds the port and the two vertical braces.

Planning on re-visiting the mid-enclosure some time tonight and include some of dlneubec's feedback...

**Hdale85** · 11 January 2012, 21:40 Wednesday

Awesome, looks like you're taking the proper approach to this!

**meb46** · 11 January 2012, 23:31 Wednesday

Amendments after latest round of feed-back...

1. Mid Cabinet enlarged to ~7L without Baffle tapering... should equate to around 8L once machined and tapered front Baffle. I still want the small section in the rear of the top cabinet for the crossover... it will be a tight fit, but at least I have made some allowance. Panel thicknesses on the Top Cabinet remain at 50mm thick as this creates an easy cut plan out of the 50mm material.
2. A quick version of the Rib I was considering using...

**meb46** · 11 January 2012, 23:38 Wednesday

Sorry... changed my mind... I have opted for a simplified Top Cabinet... this equates to a just over 10L Cabinet volume and still has a relatively complex shape to help dissipate standing waves etc...

**cjd** · 12 January 2012, 11:34 Thursday

What's the wall thickness on that top cabinet? If you can go thinner it would perhaps allow opening up that tunnel behind the driver just a little more?

Man, we're being crazy nit-picky on this for you and you're taking all the feedback with such good grace. :T

**mdocod** · 12 January 2012, 18:54 Thursday

This looks like a very impressive endeavor. Very neat cabinet shape. I'm impressed.

Someone else made mention of the port size possibly being a problem. I was thinking the same thing and decided to model it up and see how it looked...

In the current tuning and box size, The drivers will be Xmax limited to ~280W (140W per driver), and at that power, will produce a calculated peak port air velocity of 140ft/s @12hz. Obviously that would be VERY noisy as it's about 5X the peak velocity you would want in a system. However, the way it behaves at 12hz is not important since there isn't any program material down there... at 35hz, air velocity is down to ~30ft/s which is acceptable.

Whether or not you change the port size is really dependent on whether you intend to leave the bottom end full-pass and have musical tastes that include frequencies below 35hz or not. If you high pass the system at ~30-35hz port noise would probably never be a problem with the current implementation.

If you want acceptably low port noise down to ~20-25hz, port size should increase to ~150mm diameter, length ~1000mm. Keep in mind that this will consume ~20L of box space, the result is a smaller effective box, and Xmax limited Pe increases to ~325W.

------

edit in: I forgot to add, I would suggest by-amping this. It will eliminate a lot of x-over headaches which are bound to be the most problematic on the low-mid x-over. You can more easily achieve steeper slopes that will allow for lower x-over points, which will result in better off-axis response.

Best Regards and Good Luck!
Eric

**Hdale85** · 12 January 2012, 19:20 Thursday

Are you planning to use that space to store the crossover and be able to access it? Are you sure a crossover would even fit in there? For something like this I'd expect the mid/tweet crossover to be quite complicated so I think you may find that you'd have a hard time even putting a crossover in there.

**meb46** · 12 January 2012, 19:56 Thursday

CJD - "Crazy nit-picky"

Haha... as I'm sure you can imagine, the cost in both drivers and even more so TIME on this project, I want to make sure I get it right... so i'm completely open to suggestions and critisism's... what is suggested... and suitably convincing... I will take into serious consideration. All feedback is greatly appreciated

The wall thickness in the top cabinet is 50mm... probably over kill. Do you think as a trade off, reducing the wall thickness to 25mm to allow a uniform taper on the tunnel behind the Mid Driver and risking greater wall resonance is a fair compromise? If I reduced the wall thickness this would naturally also open up the crossover cavity considerably and make then resolve some of Hdale85's points... thoughts?

mdocod - I had played around a bit with this in unibox, but still not settled firmly on the port arrangment... I was more inclined to further review this when it comes to tuning the box. With the current design... I can accomodate one of two options... 1. Single port diameter up to 120mm and max length of anything up to ~700mm or 2. Dual ports diamters up to 120mm and a max length of anything up to 400mm on one and 700mm on the other. Lots of flexibility... remember, these will be flared at both the top and the bottom. Further to this, I still need to model the taper on the main woofer openings which should give me some additional/considerable volume to the enclosure coupled with all of the internal edges being radius'd off. This is done on the model as it will be hand routed after CNC machining.

Another few questions for you all... In construction, the front baffles are going to be a layered MDF/Hardwood Ply sandwich. Since I am using Ply in parts of this, is there any benefit in using Hardwood Ply over MDF in any other area of the cabinet construction? The Ply is slightly slower to machine (according to my machinist), but how does it compare if I used it for the bracing? Benefits/draw-backs?

Lastly, when others have sandwiched layers of different woods for front baffles like the Ardents or similar, what glue have you used? Is standard wood glue been sufficent or do I risk boards separating during machining? Should I consider an epoxy, or is this overkill? Thoughts? As I prepare the Solidworks files, I will also start the sandwich materials for the front baffles and thus giving them a few weeks for glue to dry and settle before machining etc.

**cjd** · 12 January 2012, 21:24 Thursday

Wow. 50mm?! I'd be using 18mm, 25mm max. I used 18mm for the dual 180mm mids in the Canaiolo, 25mm walls, and only 36mm baffle. So yeah, 50mm seems far beyond necessity to me. If I were worried about resonance I'd be adding 12mm bracing.

I also detest using MDF and go straight ply, but it has slightly different properties. At the thicknesses you're talking, the weight is un-needed and the density may also be. Jon often adds more interesting materials to the mix like bamboo ply or phenolic. Epoxy is going to give you the easiest "works with most materials" properties, and can work really nicely in a way PVA glues just don't (including staining, etc. from what I understand) but PVA strength is also going to be adequate - unless it's tons of heat or odd chemical issues (and you use the right type PVA) epoxy is more of a preference, IMO. Nice stuff, though, if you have the ventilation.

C

**meb46** · 12 January 2012, 21:43 Thursday

Many thanks... i'll look at re-modelling using 25mm in the top Cabinet. Upside is that I will have more room for the crossover.

**cjd** · 12 January 2012, 22:00 Thursday

That puts a little sense of scale on this beast! And you're still free to use 50mm but. Yeowww.

**meb46** · 13 January 2012, 03:27 Friday

Right... after all of the advice and recommendations, I think I have finally got to a point where I am happy to launch into my Solidworks machining files. I have made a few amendments due to suggestions and some thoughts I have been having on overall size and layout...

Amendments are as follows:

1. Mid-enclosure has been re-modeled using only 25mm panels. I have created a slightly larger Cross-over compartment and tried to keep the Mid enclosure to around 12L. Once the baffles are tapered and the Bitumen lining added, the total internal volume for the Mid should be around 11 liters. To keep the volume down, I have added a horizontal brace/divider. As CJD recommended, the use of 25mm sides mean I can create a greater Flare from the Front Baffle into the rear chamber.

2. The Bass Cabinet main vertical braces have been moved slightly further apart to allow for flexibility in the port. I can now fit a 120mm port diameter and an overall length of well-over 800mm... if need be.

This is just for flexibility when I come to tuning. I still entend on somehow securing the internal flare to the internal bracing to add some security against the port vibrating.

As the top and bottom of the Bass Cabinet are the most heavily braced, I have reduced these to 25mm material as I don't see any resonance in this area in favour of the increased internal volume. It also means that now all panels except the Baffles are constructed out of 25mm Ply/MDF, hence easier and more cost effective when it comes to machining.

These changes mean that after all braces are taken into consideration and the Baffle tapering, I end with a volume of 152L... near perfect

3. The position of the Tweeter has moved a fraction to improve the time alignment. This based on my previous picture/note, has a difference of around 5mm to point of listening between Tweeter/Mid/Bass.

4. The 12mm cabinet divider has been removed, (I may make one) and then test with and without this. My baffle/driver calculations were done without this, and hence I have discarded it at this stage.

All in all... I think this is what I will move forward on. I know the Mid is probably still a little square and could possible be a little deeper... but I now want to include the crossovers in the top cabinet and keep this a clean finished solution.

I'll hold off on getting too far into Solidworks files until next week, just in case there is anymore feedback

Attached below are a few more images of the design including the Bass Cabinet Matrix and the method to secure the vertical braces to the Front Baffle.

**dlneubec** · 13 January 2012, 08:13 Friday

Nice job, meb46. The changes all look to be good ones. An accessible place for the crossover is certainly a good idea. It looks deep enough that you might be able to split the crossover into two boards, one against the back panel of the speaker and one against the back panel of the mid box, making it much more likely to fit. Seeing the overall dimensions I now understand why the top cabinet is angled so far forward. I had not envisioned the speaker being that tall when I first looked at it.

I still believe the side panels adjacent to the two woofers are much too large to go unsupported. In imperial units, those must be in the range of 19"x12" or so. With 4 of them at that exact size, I think you are risking some serious resonance from those panels. Just a small brace from the internal structure neat the middle but a little off center should reduce that risk substantially. Frankly, the bitumen is not going to make that much difference, unless you install it in a constrained layer system. so adequate bracing is the key, IMO.

**meb46** · 13 January 2012, 09:40 Friday

Dan, now that I have a little more volume to play with in the bass cabinet, I can comfortably add a couple of small block/spacers to tie the side panels into the matrix... consider it done

thanks

**Bear** · 13 January 2012, 12:40 Friday

In the mid chamber, I would strongly recommend thinking in terms of adding stuffing and sound-absorbing liners (e.g., Sonic Barrier, natural (real) wool, etc.), rather than "just" bitumen. You won't "need" more than a few liters of air spring for the '90, but you will definitely want to kill the back-wave to the extent possible. From a "reach" stand point, you are most likely going to end up with a crossover in the 200 - 400 Hz range, so having a greater drop-off in output in the <80Hz range shouldn't hurt your XO slopes. Wool or Sonic Barrier (or other acoustic foam) should do this pretty well if you use it to a decent depth (e.g., 25mm or more). Whisper Mat is another variation in this theme.

**dlneubec** · 13 January 2012, 20:00 Friday

I agree, Bear. I going to try out the Ultra Touch (recycled denim insulation) on my next project, which I understand may be better than the rest of the pack. We'll see how it compares to the combination of 3/4", 3 layer sonic barrier plus acousta-stuff, which is what I typically use.

Make sure it is something you can add to or remove throught the driver opening in case you want to adjust the stuffing. Not enough and you get reflections back through the cone. Too much and the midrange starts sounding lifless.

**JonW** · 14 January 2012, 00:29 Saturday

Meb46-

You’re project looks super! :T This one is all out.

Among other things, I like the choice of drivers. With those drivers and that cabinet, you’ll have to work pretty hard to get a lousy sounding speaker out of it. Plus you’re getting great help from the regulars here. I’d love to see and hear the results.

For what little it may be worth, a couple thoughts come to mind. But note that I have less experience than the others helping you.

First, for a prior project, I mocked up various cabinet configurations with scrap ply, put in the drivers, and took measurements. I found that a slanted baffle measured better than a straight baffle. This was for just an MT. But the slanting was in the opposite direction from the top part of your cabinet. The front flange of the woofer on the bottom was closer to the listener than the tweeter. It makes sense that the acoustic centers are aligned a little better that way. I can dig up the measurements if you want to see them. They are buried somewhere in the Spassvogel MT thread. I was surprised at how much difference it made, with the slope improving things quite a bit. Anyways, I understand why you have the angle that you do, to keep the ear a similar distance from all drivers. But I’m wondering if problems might result. If I found that sloping in one direction helped a lot versus straight and you are sloping in the opposite direction. Some commercial speakers do what you are planning, so it’s probably fine. Maybe those more knowledgeable than I can explain if this inverted slant you propose will be OK.

Second, your lower, woofer cabinet looks like it will be really, really heavy. Again with the Spassvogels, coming out to be 85 pounds each that was really the maximum I was able to move around, on and off the work bench, turning over to veneer, finish them, etc. If you’re planning on some 200 pound monsters, make sure that you have a method for how to actually work on them.

Again, they look wonderful. I’ll read along to follow the progress. Good luck! :T

**mdocod** · 16 January 2012, 15:49 Monday

hmmm....

**JonMarsh** · 16 January 2012, 19:01 Monday

Originally posted by Bear

In the mid chamber, I would strongly recommend thinking in terms of adding stuffing and sound-absorbing liners (e.g., Sonic Barrier, natural (real) wool, etc.), rather than "just" bitumen. You won't "need" more than a few liters of air spring for the '90, but you will definitely want to kill the back-wave to the extent possible. From a "reach" stand point, you are most likely going to end up with a crossover in the 200 - 400 Hz range, so having a greater drop-off in output in the <80Hz range shouldn't hurt your XO slopes. Wool or Sonic Barrier (or other acoustic foam) should do this pretty well if you use it to a decent depth (e.g., 25mm or more). Whisper Mat is another variation in this theme.

+1

I used Whispermat lining the mid walls of the Ardent and stuffed with long fiber wool.

**meb46** · 16 January 2012, 23:06 Monday

All good stuff guys... I have started modelling this in Solidworks and hope to have some initial machining files by the end of next weekend. It's a bit slow going translating details from Sketchup into Solidworks... and obviously Solidworks is a little more "clunky" in its UI... slow going... but progress is being made

New Project for Critique...

New Project for Critique...

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