Speakers: MUN17-3W

[GWM]

Yes 50mm baffle is good, the baffles the most important as it radiates in the same plane as the drivers.What type of
ply did you select, I always use marine ply because it never has voids and is easier to work.

 

[fraser.]

This afternoon i did a very quick test fitting. No sanding or anything, just some frog tape to see how if i've ordered the right sizes.... seems to be fine thanksfully!

Rough idea of of bracing outline




Rear cut for hypex:

 

[fraser.]

Yes 50mm baffle is good, the baffles the most important as it radiates in the same plane as the drivers.What type of
ply did you select, I always use marine ply because it never has voids and is easier to work.

I went for hardwood ply as from a rough comparison with the others it seemed good value. I wasn't overly concerned with the quality of the material itself to be honest as the intent was always to brace the hell out of it and use a mixture of loaded resin, blocks of wood / HDF i have lying around and sound deadening material to make the thing tank-like.

To be honest i was tempted to do the whole thing in 3mm ply and use loads more loaded resin; i suspect this might actually be the best way. Other than being nice to work with and look at, wood just doesn't seem like a great cabinet material to me!

 

[GWM]

Well there's a well known very expensive loudspeaker company that bases
all its designs on resin composits.

 

[James]

It's one thing to use resin composites in castings; but quite another as a coating on a (wooden) substrate.

@fraser., will you be making lots of holes in those panels that serve as braces? Otherwise, the apparent volume of the enclosure will seem much smaller to the woofer.

 

[fraser.]

Hi james,

I like to think of it more like cast than a coating - I've purposely bought thin plywood for the sides and top as the intention is that the resin / atabites composite will be at least as deep as the ply.. probably quite a bit moreso

But yes - lots of cutting to do in the braces... I have some large hole saws but need some of jig to attach them to the drill.

I'm not sure if I'm being a thicko here... from an electrical point of view is there any difference between:

a) running cables to the crossovers, then taking the feed from those inputs (as troels has done), or

b) running 4 core cable and inputting 2x straight to the hypex high level and 2x to the crossovers? I'm not sure if I'm missing something but seems odd and a bit ugly to have cables running between cabinets. There must be a neat way of do it... the issue is that I don't want the cabinets to be connected as they'll just be too heavy to move, so the connection needs to be done externally.

 

[James]

... from an electrical point of view is there any difference between:

a) running cables to the crossovers, then taking the feed from those inputs (as troels has done), or

b) running 4 core cable and inputting 2x straight to the hypex high level and 2x to the crossovers? I'm not sure if I'm missing something but seems odd and a bit ugly to have cables running between cabinets. There must be a neat way of do it... the issue is that I don't want the cabinets to be connected as they'll just be too heavy to move, so the connection needs to be done externally.

I'm not sure I understand your question:

If (a) is running a two-core cable from amp to passive crossover, and then running another two core cable from the passive crossover input into the Hypex input, and (b) is running a four-core cable from amp and splitting two into passive crossover and the other two to the Hypex, then it is electrically the same.

 

[fraser.]

Thanks James

The other option is to house some external crossovers but I'm not sure there's a concensus on if that's a good idea.

 

[GWM]

Run your main 2 core cable from power amp to the crossover of the mid/treble box, then connect a twisted pair from the
Crossover input to the Hypex high level input.This is now mine's done, it's also how Troels does it check out his site.It's
best to use the high level input it sounds more uniform.

 

[fraser.]

I looked at the hypex modules today; they're very pretty. Unfortunately the cut-out dimensions provided online look a little incorrect - if i leave it as-is then the ventilation holes would be blocked at the top!



I could use my new toy (router) to sort this however I think i might take this opportunity make the rear look decent. I've been a bit concerned about having a removable rear baffle veneered in the same finish as the rest of the cabinet and I generally don't like it. I've tried that before and it wasn't successful, so i'd rather have the rear baffle in valchromat as well. Another order incoming....

I also need to construct a little box around it to keep the main chamber air-tight, so took the opportunity to measure that out:

 

[fraser.]

Run your main 2 core cable from power amp to the crossover of the mid/treble box, then connect a twisted pair from the
Crossover input to the Hypex high level input.This is now mine's done, it's also how Troels does it check out his site.It's
best to use the high level input it sounds more uniform.

I did consider this, and realise it's probably the easiest solution. I'm just tempted to try some sort of Wilson monstrosity just for the sake of it

 

[GWM]

The Hypex modules get pretty warm and need ventilation, you need to allow air to flow both in at the bottom and out at
the top.During the early days of production a few people didn't allow for this and had failiers.

 

[Alan McClymont]

Came across this thread late last night and did some binge reading. Very interesting for me to follow your progress as I enter the final stages of building Troel's Faital 3W10. My first go with a Troels kit although I have had a go at Wilmslow Audio kit many years ago. The crossover (bags and bags of expensive bits) has been a real worry for someone with next to no experience with a soldering iron and strange diagrams. I have had loads of help from forum members pointing me in the right direction. With a thumping heart I powered up the first speaker about 3 hours ago and guess what........ it works !

Keep up the good work.

If it's of any interest the thread I started a few days back is in the diy section.

Best, Alan

 

[fraser.]

sounds interesting Alan, i'll take a look! I looked at several of those 3way designs he did - they all looked great

good on you for taking on the crossover with little experience - i've taken the easy route and got someone more capable to do it!

 

[fraser.]

This doesn't count as woodworking by any stretch of the imagination but I started gluing stuff together tonight.

First I decided I don't want a removable baffle on the rear of the mid / treble section; i'll either just put the tweeter crossover in there, have both crossovers in the bass cab or mount them externally. So i made a start on the rear, top and back of the upper cabinet :




To keep things square I used the baffle from speaker 2 to brace against.

Then i joined the 9mm and 18mm ply front baffles of the bass cabinet together:

little and large:


Gluing baffle 1 to start:


once that was pretty dry i added the second to save some time:





I can do a little bit more, but I'd likely be better off waiting until I've done some more test fitting and routing first... patience isn't a strong point

 

[James]

... patience isn't a strong point

You can still fix mistakes before the glued joint is dry. Beyond that, it's a world of rework pain. I'd recommend thoughtfulness and presence of mind with your project. More haste = less speed.

 

[fraser.]

If wiser words are uttered in this thread I'll eat my hat James!

 

[fraser.]

I'm making no commitment to heed them however. The baffles turned out well, by my standards




A sneak preview of woofer in all it's glory



I'm really not sure about rebating for this driver now. I thought it would be quite flat around the edge but it's really quite curved... won't it look a bit baff if it's rebated? It also gives me a good excuse not to risk messing up the valchromat!

You can see here how much chamfering needs done, bearing in mind there's another 18mm still to be added to the baffle. If i'd thought that through properly I would have cut the hole bigger to start with... back to James' point. I think i'll end up taking a fair chunk out of this baffle.


I'm also uneasy with the thought of just having it mounted with some woodscrews. One because of the weight but also the depth of the magnet; surely that must be causing quite a strain on the fastenings? Scanspeak have provided a solid rubber membrane which covers the whole rear assembly, so i think i may cut another brace and have it supporting the weight of the woofer from the base of the cabinet. It won't vibrate; the rubber seems very strong.

 

[James]

Fraser,

I offer two insights from my experience, which you can take or leave.

First, I'd strongly advise against the use of wood screws; especially for a woofer as heavy as the Scan-speak 28W. The mounting holes are sized for M6 bolts, which I'd recommend for use with either threaded inserts or T-nuts. Fashioning a brace to support the motor is unnecessary if the woofer basket is securely located on the baffle.

Second, the flange of the 28W has a similar profile to its little brother the 15W, which I used in my E-IX design. The rebate I cut is deep enough only for the gasket and vertical edge. I think it looks better partially rebated.

If you're thinking of chamfering the inside edge of the woofer cutout, consider if you're going to use machine bolts with threaded inserts or T-nuts first. These will need to be located before cutting the chamfer around them. See how I've done it below:

James

 

[fraser.]

Thanks James - that's really useful!

The thought of using threaded inserts / t-nuts does make me squirm a little as getting it wrong means a lot of re-work. There will be many hours spent on youtube tonight watching examples / ideas of how best to do it...