Not another 2x10 DIY Project?!?

[michabass]

To continue from here:
http://www.talkbass.com/forum/showthread.php?p=6429078#post6429078

Building a top performance speaker cab for bass guitar amplification chain is all about making compromises: a cab needs to have a huge “bottom” (low frequency extension) which requires a big cabinet, while at the same time it needs to be portable, lightweight, and to be able to fit into a busy gigging musician’s trunk, which means small cabinet. So there you have it – you cannot have both. It’s Physics…

It is the same when choosing a loudspeaker: the moving parts (cone, surround, spider, and voice coil) need to move very fast, and to respond to fine nuances of musicians playing style with ease, meaning they have to be thin and as light as possible. However, they also need to be robust and strong to survive the continuous onslaught of a, for example, loud rock gig night after night, which means they have to be thick and heavy. Again, it is all about compromise.

Like any other speaker cabinet design process, this one started with choice of the driver. I noticed that one particular little gem keeps showing up over and over again in a vast majority of contemporary bass guitar 2x10“cabinets. You guessed right, it is the Eminence Delta 10.

Manufactured by one of the largest companies on the market (if not THE largest), Delta series 10” woofer offers surprisingly long cone excursion at low distortion, and a quite high efficiency considering the relatively small cone surface and magnet size. This speaker has a pressed steel basket unlike the more expensive cast aluminum. It has simple terminals with provision to connect another speaker in parallel. The vented ceramic magnet, voice coil, braids, spider, surround, paper dust cap and cone all seem to be good quality, making this speaker a best buy unit with excellent price/performance ratio.

One other thing: it was not made for weight weenies!
Nor was the cabinet: It’s MDF and it weighs around 54lbs – I’m a strong enough guy to carry it around myself and it fits into the trunk of my old jalopy car nicely, leaving plenty of spare room for the head, cables and what not…

I use MDF, tough carpet covering, steel grills, and plastic corners to cope with rigors of gigging as well as rear side ports to lower the tuning frequency and some damping to fight the internal resonances. The assembly method of choice for a DIYer is certainly glue and screws. For weight weenies out there - when the glue sets you can even take the screws out, just the glue will hold for sure... I am not so obsessed with weight so I will leave them in. To reduce clutter in my working room I had the MDF depot pre-cut the panels to dimensions I had specified.

One rule of thumb I always follow is to first gather all the parts for a cab and only then begin assembly. That way you can make sure that all dimensions are “true” and you will have no gaps or tight fits in your project.

 

[bgavin]

The Delta 10a is a less than optimum driver for electric bass. First, it has a ferrite magnet (not ceramic). This is of no impact to performance, but should be noted for accuracy. However, it is cheap and also available in 16 ohms.

The Fs is 66 Hz, which is too high unless you are interested in a baritone bass. Horn loading the Delta 10a will push the system resonance lower than 66 Hz, but reflex loading will not. This is fine for anybody interested in 2nd harmonics only. Delta 10a is not a big bottom driver under any circumstance.

The 3.5mm Xmax is somewhat short compared to better drivers. However the 9.4mm Xlim is nice. Vd is only 121cc, the same as or less than Vd of the Neo drivers, or the 207cc of the BP102.

As to MDF... too much weight. Been there, done that. Loading 135 pound MDF subs at 2am is a pain in the back and knees. There is no good reason whatsoever to use MDF for portable rigs. Mine took a lot of road abuse and held up fine, other than rounding off all the corners and edges. 12mm (half-inch) baltic birch is stronger and weighs less. 41 pounds per cubic foot vs. 49 pounds for MDF. One can save more weight by using Arauco, Spruce, or other lighter weight plywoods. 12mm does not buzz at all if properly braced. All bracing can be swiss-cheesed to reduce weight.

Every non-subwoofer cabinet should be fully lined to absorb internal reflectances. An RTA of before vs. after is very revealing as to how much damping improves the sound. Mattress topper (Walmart, $9.50 USD, twin size bed) works just fine for this. It is easy to install and does not have the nasty problems one experiences with fiber glass.

Screws left in the project only add to the weight. There is no strength advantage of any kind to leaving the screws. If you use PL Premium Polyurethane adhesive, you will never have a joint break, nor will it leak. This is the messy stuff applied with a caulking gun that expands as it cures. The wood will break before the PL breaks.

If you need a big bottom from a small cabinet, build an isobaric enclosure. Use a pair of BP102 in a net volume of 2.0 cubic feet. This is a tiny cab with an F3 around 30 Hz. The BP102 always requires a mid-bass driver. An Alpha 6 crossed over at 500 Hz will do nicely. This cab is intended for the bassist wanting a full range box for small venues. It isn't a big noise maker.

 

[michabass]

and actually read what i wrote... nice for starters
@ bgavin
well I have to agree with you on most part. MDF is heavy, Delta woofer is not the ideal speaker one would want in his rig, but looking on the other side DIY is to learn as one goes. What I wanted to display is merely the procedures I use in making a typical cab so novice builders can avoid practical mistakes I made years back while still learning. Those same procedures can be applied with the lightest obtainable materials and the most ideal components available. Thus one would obtain a far better result in the terms you are talking about... The Delta cant be so bad if SWR, EBS and other guys are using can it now?
Anyway if you let me finish where I was going with this I will post a few pics and then you can all be the judge if there is any use in them at all

 

[michabass]

Well I must say I had no plans to make the ultimate box anyway, rather a box that will do the job I had in mind for it: play loud and clear at any* gig. That is exactly what all those working bass players are raving about when they praise those small 1x15, 2x10 and 1x12 boxes. Compact cabs tend to have a “tight” bass with a lot of “punch”.
With all the MDF parts cut to spec by the supplier i opened the holes for speakers. Using a regular jig saw I cut the hole for the Eminence APT tweeter. I like this just a few millimeters wider than the magnet, so there is enough “meat” for the screws that hold it in place.

 

[michabass]

I have cut the holes for woofers, pre-drilled screw holes and tried how the speakers fit. This is important – you do not want to repair a hole that is too tight when you glue the carpet on!

For woofers I choose t-nuts and strong 8.8 grade steel hex head burnished M6 bolts. Drill the hole with 7mm drill bit to allow the t-nut to go in tightly as it measures 7.5mm. This way the t-nut will stay tight for years to come.

I like to make sure it stays there by adding just a touch of glue. It cannot hurt. You want to press these in before you assemble the cab; it is much easier that way.

Two pins closest to the edge of the speaker hole need to be at the same distance from the edge, or they will tear the MDF. You want to press them in gradually to avoid damage of the chipboard. Some do it with a hammer – I don’t.

 

[michabass]

I’ve found an easy way to do this is by slowly tightening the bolt with a long hex wrench. I usually place a heavy flat washer to prevent the bolt head sinking in the wood.

Next I glued the board that connects front and rear baffles. I placed the pieces on a flat surface and drilled the holes for wood screws. Then I applied the glue and tightened the screws.

Do the same with the rear panel.

Let the glue dry for a few hours just to be sure it does not wiggle while you move it around.

I always countersink the screw holes so I get a nice flat surface, which helps a lot later when I apply glue for the carpet. Bottom side goes on, all holes pre-drilled and countersunk.

Apply generous amounts of wood glue. I do it in two passes: one to cover the entire contact surface in a thin coat, and another to make a nice “stack” of glue that will seal any wood imperfections.

 

[michabass]

All screws are in their holes and ready to be tightened. I use a power tool screwdriver to speed things up.

Bottom side is glued, time to glue the top side. Repeat the above steps.

Same thing with the sides of the cab: drill holes, apply glue and tighten screws…

Now to cut out the openings for the recessed handles... I drill holes in the corners matching the radius of handle corners, in this case 10mm. Then I use a jig saw to cut the rest of the hole.

Place the handle in the hole and mark the holes with a sharp permanent marker, like a CD-pen. Remove the handle and pre-drill the screw holes.

I use a 9mm radius router bit to round the cab edges. This is exactly how much it takes for the plastic corners to sit properly.

Before I apply the glue for carpet i prime the MDF cabinet surfaces with slightly diluted wood glue and let it dry overnight. After that the cab is ready for carpet finish.

 

[i_got_a_mohawk]

Another problem with MDF is it'll act like a sponge if it smells moisture, and wont last as well as some decent ply.

And have you thought about using a Delta Lite?

 

[michabass]

it is 2am here and I gotta go to work in the morning at 6:30
I will continue tomorrow if it's OK with you guys?

 

[michabass]

Another problem with MDF is it'll act like a sponge if it smells moisture, and wont last as well as some decent ply.

And have you thought about using a Delta Lite?

It wont smell any moisture as I keep it in my bedroom (very dry take my word for it). As for others feel free to use Baltic birch or any other elusive and omnipotent monkey-picked type of plywood you can get your hands on!

I have thought about using a Deltalite and gave up for economical/local procurement lead times reasons... as for others -well you guessed it - any space age, NASA made, lighter-than-a-feather-woofer will do nicely...

 

[michabass]

I apply the glue to both the carpet and the cab surfaces. Wait 10 - 15 minutes and press them together. This is contact glue so no excessive pressure is really required. I always start at the bottom side so the seam is out of the view.

I glue one side at a time. First bottom, then side, then top, then the other side and finish at bottom again. I don’t apply the glue on carpet where the holes are.

While I wait for the glue to dry I trim the front baffle corners.

The „wrap-around“portion of carpet is in place. After that I will glue the front edges of „wrap-around“piece so I can turn the box on its face and prepare for the rear side. This is how it looks from the rear...

...and from the front.

I cut the corners like this: i overlap them and use a very sharp knife to cut them at once. This will leave a nice looking joining surface.

When all four corners are prepped i apply generous amounts of glue to both surfaces. You don’t want to go cheap here as the carpet can easily come off of the edges if there is not enough glue... Wait 10min and press.

This is how it should look when front side is done. At this time I usually install the handles so I can manipulate the box around easier.

Turn the cab on its face and apply glue on both surfaces. For the rear side I choose a „letter” type joint. One side at a time: glue one side, overlap and cut the neighboring side, then glue it and overlap and cut the next one...

Two opposite sides are glued and ready to overlap with its neighbors.

I use a very sharp knife and a straight piece of wood to make the cut right. Keep the knife vertical to make the joint seamless. I apply brute force and make the cut in a single pass for the best result. Step on the plank to prevent it from wiggling.

There will be a piece of the bottom layer of carpet that you want to pull out.

Pull out all the pieces from under.

Repeat the above procedure for the opposite side.

Now, as you do this you may feel there is little or no glue left under the joint. Apply generous amounts of glue as this is one place you don’t want the carpet to come off.

The joint may seem messy but if the cut was vertical you’re OK.

Wait 10-15min for it to dry and press firmly. I usually tuck it in like this to make the joint seamless.

 

[michabass]

After you’ve glued the rear side you can cut the vent holes out.

This is how it should look like with vent holes and connector plate hole ready. If you did a good job there will almost be no visible seam.

Now you’re ready to glue the front baffle carpet. Apply the glue on both surfaces, wait 10-15min and press firmly.

Cut the speaker holes out with a sharp knife.

Rat furr in all it's glory

The rear vent tubes are in place, glued and pressed in. The cabinet slowly starts to look like it should...

Try once again if everything fits properly, this is the last chance to make any corrections… and the first chance to see the cab finished.

Once you are sure everything fits OK you can proceed to solder the speaker cables to crossovers and terminals. If you made the tweeter hole as snug as I did the tweeter cable will not fit in the hole next to the magnet, so you will have to make a channel like this to pull the cable thru.

This is how the cable should fit in the channel. You can avoid this if you make the hole larger but that is something I just don’t do...

The APT horn is in its place.

I filled the cabinet with “tailor’s wool”. You do not want to over-dampen the cab with this stuff. A rule of thumb I use is: it should be easily compressible by hand all the way to the rear side, but when released it should easily expand on its own to fill the cab volume…

When soldering you should leave a generous run of cable going from crossovers to the drivers. In the future you may wish to take them out and then you’ll be glad you did. Use a 60-100W soldering gun and a lead-free solder wire to do it right. Tighten everything firmly and you’re done!

 

[michabass]

Summary

That is pretty much it!
On the back, I installed connectors for speaker cable going to the amp. There is one Speakon™, one ¼” jack and one attenuator switch for the horn level with three positions: normal/low/off.
I will not deal with the crossover here since it is not the purpose of this tutorial. I will only say it is a simple third-order/automotive light bulb design proven over and over again in practice. I can provide schematic if anyone wishes to see it thou...

The cab does look nicer without the grilles but aesthetics come second here.
A perfect match would be a grill covering the entire front baffle with larger holes like Gallien-Krueger cabs and alike have, but at the time I could not find any that go with this cab so I had to settle with individual grills. I know, I know it looks like a car sub... I will look for a suitable one-piece grill in the near future when these get bent ouf shape.

The cab can be used sitting down or standing up. Two last pictures show the cab with an ASHDOWN MAG300 amp and a custom made ILLIANI bass guitar.

 

[Energy]

hey, nice job!
how does it sound?

 

[michabass]

hey, nice job!
how does it sound?

Basicaly it sounds like an SWR redhead 2x10 combo (the speakers part only). I compared it with the SWR and it is in all respects the same except the SWR has a little more umphh since it has some 10l more volume. This is with both tweeters fully on.

I did a few gigs with it, one of which was on a yacht/night club in the open and was surprised at how much punch and growl this litlle thing had!
I had to compete with a loud drummer and it did the job with such authority that I now wonder why in the world I bothered with a 2x12 cab for the past three years

The Ashdown pumps 300w at 4 ohms, and I have to be honest here: the speakers fart out at extreme bass EQ settings, or with low B fairly easy, but then again it is only a 10 incher! Find me one that does not do this at almost full volume and I will give the cab away! If your smart you will have plenty of headroom.

 

[mcrracer]

Hi, Nice job. You may want to check out this site if you want to get serious about high performance speaker cabs.
http://www.billfitzmaurice.com/

 

[bgavin]

Exactly.

You presented an excellent tutorial with great photographs. I'm not being nasty here, but advising the newbie to use Delta drivers and MDF is just wrong.

The major manufacturers use Delta because it is CHEAP. Their designs have to follow a specific look and feel to be accepted in the market. They have to be CHEAP so they can make a profit without charging a boutique price. This includes SWR. There is a huge difference between two cheap drivers in a pretty cab vs. a highly engineered design.

Even installed in an optimal alignment, the Delta driver has an F3 around 88 Hz. This is a mid-bass driver, not a bass driver. If you need a tiny box, the Basslite S2010 is a whole lot better driver, weighs less, has an F3 20 Hz lower. Delta is just plain wrong for electric bass.

As to weight, it is typical commercial construction: make it too thick and use no bracing. MDF is just plain awful for a portable cabinet. You could make this same cabinet out of 9.5mm baltic birch with modest bracing, and save a ton of weight.

Mattress topper (Walmart, $9 USD, twin bed size) is open cell foam that looks like egg crate material. Easy to work with, and you can hot glue it to all the internal walls. Felt carpet underlay is another damping material easily applied in sheets. There is never a problem with loose material impeding the cone or blocking the driver vent.

The photos and step-by-step examples are very well done. This cab would work well as a top box with a subwoofer low passed at 100 Hz. For your next project, build a 3015LF sub for the Delta box. Use 12mm baltic birch and brace it. The pair will open a new world of authoritative bass that doesn't exist with the Delta box alone.

 

[sleepy_monkey]

Cool! Gives me some ideas for using 2 10" GK's I have lying around....

Anywhere to find dimensions/schematics of a 2x10 cab?

 

[michabass]

thanks for the kind words and constructive criticism. I appreciate it really.
One thing thou: I do not advise the beginner DIYers to use MDF or heavy delta drivers or rat fur or car-sub grilles!
I do not advise no one to use anything at all... as I wrote above this is just a simple project captured in this convenient form. If anyone finds useful the technical aspects of such a build that is fine, if not that is OK too.
I have made cabs out of birch ply before and they are by all means superior to MDF. I have used ceramics, alnico, neo, piezo and just about any other type, shape and size of speaker available. What I have shown here is just a simple project showing the steps anyone can repeat with basic skills. It does not pretend to be superior to any other method. I just showed how I do it...
Jeez you guys are a tough crowd I should not have to explain myself, I mean I planned, bought the parts and built the thing in like 3 or 4 days, because I needed a speaker for some gigs with money I had in my pocket! There was no time to search for the holly grail of tone

 

[OldogNewTrick]

cool, thanks for the effort of posting - the result looks great.
Your tips for covering are helpful to me.

Always something new to learn from every project.