Diamond Audio D6 15" Subwoofer Build

[MidnightSensi]

I had a lot of fun playing with the JLs and got some good results, so I'm going to attempt my first home subwoofer. The driver I want to use is a Diamond Audio D6 15" in a vented enclosure. Here is the design:

I based the idea of how to vent it off the Infinity Kappa Perfect builds here, but I had to go wider because this driver pumps so much air, so the entire bottom of the enclosure becomes part of the vent.

The Driver:

Diamond Audio D6 15" dual 4-ohm
SPL(dB):87
Re(Series) 6.0
Qms: 4.52
Qes: 0.58
Qts: 0.51
Fs: 28Hz
Vas: 74L
Cms (MM/n):0.081
Mm(g): 398
Sd(m^2):0.080
BL (T*M):27.2
Xmax mm): 15
Pwr(w) nom/max: 750/1500

My box will be a 5.5ft^3 vented with a 22Hz tune. Vent is 3inx18in (HxW) and 49.35in long.

What do you guys think?

It's dual 4-ohm, so should I get a two channel amplifier and run one voice coil off each channel?

 

[MidnightSensi]

Oh, also, do I need more bracing? The sides will have 2 3/4" walls, because stiffness increases by a square so that will quadruple the side stiffness. The top is what Im a bit worried about, maybe another 3/4" there too or some triangles in the front?

 

[MidnightSensi]

So playing with the sub design today I made some changes. I didn't like how tall the other one was, because while this subwoofer will be big I think a low profile would at least make it fit under TVs, behind a couch, or be stackable, etc. So here is the new design, it has basically the same parameters but the port is 3.5x17, which has the airspeed in the port to 62fps maximum.

I have a few questions:

1. I read WmAx's post about using birch ply rather than mdf. I want to try this, because with MDF the subwoofer weighs 109-lbs, and with birch only 91-lbs (without the driver). I'm not sure how much the Diamond D6 15" weighs, but I'm sure its probably in the 40s. I will need to put handles on either side, and it will take two people to carry, but I'd still like to keep the weight as low as possible.

I'm handy and work with fiberglass and composites often, should I laminate the inside for added stiffness? E-glass at $3 a lb. or so is probably a pretty cheap way to stiffen.

2. Do I need to put any filler in there? The box is the right size, but I see a lot of people putting some fillers in their boxes to help with standing waves and such. Will that change the tuning of my box?

3. Anyone have handle recommendations?

4. The sub is dual voice coil with 750-watt continuous power handling, I'll get the 4-ohm version. Should I just buy a stereo amp and wire each channel to a voicecoil?

Cheers

 

[MidnightSensi]

Here is a view of it closed up

 

[annunaki]

I would cut some windows in your bracing pieces to help alleviate additional displacement as well as weight.

8lb/ft^2 mineral wool can be used to help with resonances at higher frequencies. Depending upon the x-over frequency it may or may not be needed.

Fiberglass inside would not add much in the way of stiffness unless it had many bends in it. In any case, it simply is not necessary. Additional bracing can't hurt though

 

[MidnightSensi]

I would cut some windows in your bracing pieces to help alleviate additional displacement as well as weight.

8lb/ft^2 mineral woll can be used to help with resonances at higher frequencies. Depending upon the x-over frequency it may or bay not be needed.

Fiberglass inside would not add much in the way of stiffness unless it had many bends in it. In any case, it simply is not necessary. Additional bracing can't hurt though

Thanks for your response, I'm really excited about this project.

I just ordered hardwood birch ply, should be here in a few days with my regular shipments.

I also just ordered a dbX DriveRack PA Processor for my 20Hz cut and any EQing I want to do once in the room.

The amplifier will be a Crest Audio CC 1800 (1850W). The amp is a little overkill, but, its what I have. The driver has 750-watt continuous power, but its dual voice coil... so if I run each channel from this amp it will have 700-watts per coil at 4-ohms... is this gross overpowering going to be a problem or will I be okay as long as I don't turn it up so much that it distorts? Should I run off of one channel (700-watts at 4-ohms) instead? At 2-ohms its 900-watts per channel.... how do you think I should wire this thing up?

I'm going to order some handles and input terminals from parts-express today also. I'll grab some mineral woll too... I'm gunna cross over at 80Hz (the tops are M&K S-150s) so resonances shouldn't be a problem..but, can't turn to toss some in there.

As far as when I build it, if all the parts come in I want to try to do it sometime this month. Time is where I have a bit of a problem.

How should I finish it? Would AWL Grip work? Black AWLGrip?

 

[annunaki]

The Behringer DCX2496 is a fabulous processor. I do believe it to be cheaper than DBX products as well.

As for the amplifier, the amount of headroom (extra rms power on tap) one has is important. Especially when running a significant amount of eq (depending upon the room, or with sealed enclosures). The EQ in your case (vented enclosure) will mostly be to tame room modes (peaks) or bump response very slightly (2-3db).


Most of the time you will only be using 10 watts of power or so. The additional power is not going to cause a problem unless you are trying to wake the dead with a 2 hour long, non-stop, bass fest.

What loads will the amplifier handle? Will it do 8 ohm mono? If so, what is the output?

One coil per channel is fine if you voltage match the outputs before hooking up the woofer.


With normal regular usage you should have no worries in overpowering it.

 

[MidnightSensi]

The Behringer DCX2496 is a fabulous processor. I do believe it to be cheaper than DBX products as well.

Yeah, I just already know how to use the dbX and have had better luck with the brand in the past.

As for the amplifier, the amount of headroom (extra rms power on tap) one has is important. Especially when running a significant amount of eq (depending upon the room, or with sealed enclosures). The EQ in your case (vented enclosure) will mostly be to tame room modes (peaks) or bump response very slightly (2-3db).

Most of the time you will only be using 10 watts of power or so. The additional power is not going to cause a problem unless you are trying to wake the dead with a 2 hour long, non-stop, bass fest.

What loads will the amplifier handle? Will it do 8 ohm mono? If so, what is the output?

One coil per channel is fine if you voltage match the outputs before hooking up the woofer.

Nope, it won't do 8-ohm mono. 4-ohm stereo it will...

8 Ohm Stereo - 450 W
4 Ohm Stereo - 700 W
2 Ohm Stereo - 900 W
4 Ohm Bridged - 1800 W

http://www.crestaudio.com/products/browse.cfm/action/detail/item/116299/number/01000800/cat/342/begin/0/CC%201800.cfm

What does voltage match the outputs mean? Make sure the gains are set the same?

With regular usage you should have no worries in overpowering it.

Yeah, and at 115-116dB peak, if that WinISD software is correct, its well above what I would ever use. That's pretty frickin' loud....especially once I put it in a room.



Thanks for all your help man!

 

[annunaki]

Yeah, I just already know how to use the dbX and have had better luck with the brand in the past.



Nope, it won't do 8-ohm mono. 4-ohm stereo it will...

8 Ohm Stereo - 450 W
4 Ohm Stereo - 700 W
2 Ohm Stereo - 900 W
4 Ohm Bridged - 1800 W

http://www.crestaudio.com/products/browse.cfm/action/detail/item/116299/number/01000800/cat/342/begin/0/CC%201800.cfm

What does voltage match the outputs mean? Make sure the gains are set the same?



Yeah, and at 115-116dB peak, if that WinISD software is correct, its well above what I would ever use. That's pretty frickin' loud....especially once I put it in a room.



Thanks for all your help man!

It will do 8 ohm mono. It will do it at around 900 watts or so. If it will do 4 ohm mono it should do 8 ohm mono without breaking a sweat. Unless of course you are seeing some weird stipulation that I am not?? They simply are not specifying what the power output is. I am sure the marketing people wanted the biggest number possible on there 4 ohms mono will accomplish that task.

Volatge matching is a process of setting the amplifier gain. One would play a single frequency and use a DMM (Digital Multi-Meter) on a speaker output and check the voltage (AC). THen on the other channel slowly adjust the gain until they match exactly. The gain knobs always have some variance between the channels.

Mono operation obviously rids one of this step.

 

[avaserfi]

If you have the port at 3.5 x 17" the port is probably in excess of 70" long? If this is the case your first port resonance will be fairly low and you will need to cross over below 80Hz to remove any colorations created.

What does WinISD say your first port resonance is?

 

[MidnightSensi]

It will do 8 ohm mono. It will do it at around 900 watts or so. If it will do 4 ohm mono it should do 8 ohm mono without breaking a sweat. Unless of course you are seeing some weird stipulation that I am not?? They simply are not specifying what the power output is. I am sure the marketing people wanted the biggest number possible on there 4 ohms mono will accomplish that task.

No, I think your right, they just didn't list the 8-ohm mono.

So I would wire positive into the + of voice coil 1, then from the - of voice coil 1 into the + of voice coil 2, then the - of voice coil 2 back to the amp/negative. That makes it a series connection and 4+4 is 8... right?

The lowest impedence of that driver as such is like 7.98-ohm, so, it should be a pretty easy load.

If you have the port at 3.5 x 17" the port is probably in excess of 70" long? If this is the case your first port resonance will be fairly low and you will need to cross over below 80Hz to remove any colorations created.

What does WinISD say your first port resonance is?

Oh, whoops, I wrote the wrong dimensions for that port. I slept like crap last night haha. It's actually 3.25x19" and 56.78in long ...first resonance is 119.15Hz so I should be okay crossing over at 80.

 

[annunaki]

Your explanation of the series connection is correct.

Crossover at 80hz, use a 3rd order slope or higher for assurance. You should be safe though.

 

[MidnightSensi]

Your explanation of the series connection is correct.

Crossover at 80hz, use a 3rd order slope or higher for assurance. You should be safe though.

Nod. Also it has a bend in it and is a slot tube. I've heard that might help a bit. For the crossover I can go pretty sharp if its a problem, I'm glad I'm safe at 3rd order though. Because of the bend I wanted to lower the air velocity in the port a lot to keep shuffing down.

For the low end, my cone excursion shoots up at 20Hz or so, below the tuning like expected. By 19Hz I'm at xmax. Should I just low cut at 20Hz, or should I EQ it to keep it under control and then cut it lower?

 

[annunaki]

Add the filter in WinISD it will control it. Typically a 2nd order highpass at 20hz is enough. If you need to, you could use a 3rd order or higher infrasonic filter.

 

[TLS Guy]

I had a lot of fun playing with the JLs and got some good results, so I'm going to attempt my first home subwoofer. The driver I want to use is a Diamond Audio D6 15" in a vented enclosure. Here is the design:

I based the idea of how to vent it off the Infinity Kappa Perfect builds here, but I had to go wider because this driver pumps so much air, so the entire bottom of the enclosure becomes part of the vent.

The Driver:

Diamond Audio D6 15" dual 4-ohm
SPL(dB):87
Re(Series) 6.0
Qms: 4.52
Qes: 0.58
Qts: 0.51
Fs: 28Hz
Vas: 74L
Cms (MM/n):0.081
Mm(g): 398
Sd(m^2):0.080
BL (T*M):27.2
Xmax mm): 15
Pwr(w) nom/max: 750/1500

My box will be a 5.5ft^3 vented with a 22Hz tune. Vent is 3inx18in (HxW) and 49.35in long.

What do you guys think?

It's dual 4-ohm, so should I get a two channel amplifier and run one voice coil off each channel?

Your vent velocity is too high at 60 m/sec. It needs a different port to get vent velocity somewhere below 18 M/sec.

 

[avaserfi]

Your vent velocity is too high at 60 m/sec. It needs a different port to get vent velocity somewhere below 18 M/sec.

He has it listed in feet per second for some reason. I know weird...

 

[WmAx]

What is the reason for choosing this driver? Is their a third party analysis some where demonstrating this to be a very linear driver? For example, one could choose a 15" driver that has such 3rd party analysis available, proving it to have an extremely high quality motor.

-Chris

 

[TLS Guy]

He has it listed in feet per second for some reason. I know weird...

So that would make it 18.26 m/sec. It just gets in by a whisker. Really that driver is for sealed not vented alignment.

He had better use an infrasonic filter, as that driver has a very loose suspension from the T/S parameters. I should think it would self destruct pretty quickly with any large signals below Fb.

 

[MidnightSensi]

What is the reason for choosing this driver? Is their a third party analysis some where demonstrating this to be a very linear driver? For example, one could choose a 15" driver that has such 3rd party analysis available, proving it to have an extremely high quality motor.

-Chris

I've had experience with Diamond in car audio (well regarded) and also used some subwoofers that were DIY prosubs when I used to do some underground parties, and they absolutely pounded while sounding amazing. I've heard them in lots of applications and really liked them, so that's why I decided to use them here. It also mapped out really nicely and I wanted to try something a little different, so, that's why the D6. Diamond Audio isn't really well known, but, in certain circles they are...

With trying a little something different, maybe we can gain some new experiences here to share. I already have a Infinity Kappa Perfect 12 in my truck, so, don't worry I like that one too.

So that would make it 18.26 m/sec. It just gets in by a whisker. Really that driver is for sealed not vented alignment.

He had better use an infrasonic filter, as that driver has a very loose suspension from the T/S parameters. I should think it would self destruct pretty quickly with any large signals below Fb.

I actually talked with Diamond and they said its good for both, and that the rules of thumbs with evaluating T/S parameters are just that. Lots of their customers use vented boxes, he said. JL told me the same thing, since some of their drivers tended to lean one way or the other when looking at that.

That vent speed is at 800-watts, which is insane. My real vent speed will be much lower, also remember this is a 15" ... so there is simply a lot of surface area.

The motors are soft stop, actually one of the reasons I went with them rather than the JL's I was considering (and also like), so they actually are designed to be self-limiting and the suspension stops the driver (within reason) before it self destructs. It's how they became known for really good durability in the SPL circles.

I knows its a little different, but, hopefully that'll keep this build interesting!

 

[MidnightSensi]

Worked on my box today, driver came just a bit ago so I didn't cut the holes yet. Probably do that Monday, need to wait for some parts to come in from Parts Express.

Silicone anywhere air can leak.