JL 8w7 built in cabinet

[Bushka]

So, here's what I would do in your circumstances:

1) When finalizing the cabinet and sub dimensions, ensure the sub it will fit in the cabinet without touching the back or side walls.
2) Glue some carpet underlay (or other resilient material) around the perimeter of the opening in the cabinet bottom. Then position the sub enclosure on top of the material.

That's how I installed my in-ceiling subs and it worked well for me.

Yeah, I think I'll stay away from in-ceiling.

I know some people on the other thread got very nervous when I started talking about putting a sub inside a cabinet. Have you seen other people isolate a sub as you recommend?

If I build the box into the cabinet itself, then the speaker will point straight into the toe kick area. If I set the box inside the cabinet with carpet underlay as a vibration insulator, the speaker will now be kind of set up into the cabinet instead of bonded to the bottom, and I wonder if that will allow sound/vibration to leak from inside the cabinet. Anything to worry about there???
Thanks.

 

[TLS Guy]

Yeah, I think I'll stay away from in-ceiling.

I know some people on the other thread got very nervous when I started talking about putting a sub inside a cabinet. Have you seen other people isolate a sub as you recommend?

If I build the box into the cabinet itself, then the speaker will point straight into the toe kick area. If I set the box inside the cabinet with carpet underlay as a vibration insulator, the speaker will now be kind of set up into the cabinet instead of bonded to the bottom, and I wonder if that will allow sound/vibration to leak from inside the cabinet. Anything to worry about there???
Thanks.

I would set the sub inside the cabinet without making it part of the cabinet.

For one thing you may have vibration problems and that location may be a lousy location for the sub. The you have the fall back of taking the sub out of the cabinet and placing it elsewhere.

 

[GO-NAD!]

As TLS said, I wouldn't build the sub as part of the cabinet. And, I would not screw it to the bottom of the cabinet. If you leave a clear opening in the bottom of the cabinet for the driver and vent, I wouldn't worry about sound/vibration in the cabinet. Just bear in mind, the sound waves coming from the sub will be transmitted to the surrounding walls - you just don't want anything to rattle. That's why I suggest isolating the sub from the cabinet with the foam. You could even try it without the foam - who knows, there may be no problem. Then if you do get a vibration or rattle in the cabinet, you could try the foam. By not hard mounting the sub, it can give you some flexibility in addressing any vibration issues you encounter. If you build it into the cabinet, there won't much you can do to fix them.

 

[Bushka]

Hi guys. Getting this thing built has been painstakingly slow due to time commitments on my part. I did get the TV installed, though.

Something occurs to me. I've been going on the concept for a long time that this subwoofer would be built into the cabinet. Now it appears from the last couple of posts that it is probably best to have a "free standing" sub placed over a hole in the bottom of the cabinet instead. It occurs to me that maybe I can buy a down-firing sub instead of building one. I know if I took my time I could build one, but it seems difficult to determine the exact box volume needed (and I'm not sure how exact this volume has to be), best bracing and so on. So I'm weighing the two alternatives. Do I spend say $400 on components to built a sub that hopefully sounds like a $1000 sub, or do I spend $400 on one already done? Can you get a sub worth having for $400?

Any help is appreciated. I'd kind of like to build one myself, but I just wonder if my construction is going to be good enough to get the correct sound out of it. (For instance, if I'm off by 10% on the box volume will you even be able to tell?)

 

[TLS Guy]

Hi guys. Getting this thing built has been painstakingly slow due to time commitments on my part. I did get the TV installed, though.

Something occurs to me. I've been going on the concept for a long time that this subwoofer would be built into the cabinet. Now it appears from the last couple of posts that it is probably best to have a "free standing" sub placed over a hole in the bottom of the cabinet instead. It occurs to me that maybe I can buy a down-firing sub instead of building one. I know if I took my time I could build one, but it seems difficult to determine the exact box volume needed (and I'm not sure how exact this volume has to be), best bracing and so on. So I'm weighing the two alternatives. Do I spend say $400 on components to built a sub that hopefully sounds like a $1000 sub, or do I spend $400 on one already done? Can you get a sub worth having for $400?

Any help is appreciated. I'd kind of like to build one myself, but I just wonder if my construction is going to be good enough to get the correct sound out of it. (For instance, if I'm off by 10% on the box volume will you even be able to tell?)

The sub you will build will be comparable or better than one costing 2K or more. You won't get anything close to that sub for $400.

 

[lsiberian]

Do I spend say $400 on components to built a sub that hopefully sounds like a $1000 sub, or do I spend $400 on one already done? Can you get a sub worth having for $400?

Any help is appreciated. I'd kind of like to build one myself, but I just wonder if my construction is going to be good enough to get the correct sound out of it. (For instance, if I'm off by 10% on the box volume will you even be able to tell?)

Building a DIY is not hard if you know how to build a box. Some corner bracing and rib bracing from the scraps should do fine for a box. IB is an option you might consider too. I really am a big fan of this approach where hidden subs are desired. You get amazing performance with no floorspace.

There is a large window of error in box volume construction. It's need not be super precise to get fantastic results. Get it in the ballpark and you will be just fine. If ported is too complex for you than just do sealed.

 

[Bushka]

It's good to hear you can get such good quality by building your own, without having to maintain aircraft grade specs! I'm not sure what IB is, but I can probably say it won't work for my situation.

So I'll go ahead with the DIY model. I need to re-research the amp and driver since it's been so long. I think they discontinued the one I was looking at before, but not sure. I'll try to draw up a sub design an post it here. Maybe one of you guys can check my work before I start making anything.

Thanks again for the guidance!

 

[lsiberian]

It's good to hear you can get such good quality by building your own, without having to maintain aircraft grade specs! I'm not sure what IB is, but I can probably say it won't work for my situation.

So I'll go ahead with the DIY model. I need to re-research the amp and driver since it's been so long. I think they discontinued the one I was looking at before, but not sure. I'll try to draw up a sub design an post it here. Maybe one of you guys can check my work before I start making anything.

Thanks again for the guidance!

No it wouldn't your driver is designed for a box. Of course your driver is amazing. My suggestion is build a sealed box and see if it's good enough for you. If not we can talk about a ported design. If you need me to calculate an Volume and cut list I can.

You can take a look at my build to see how simple it is. I do recommend hex head screws. It took me only a couple days with a circular saw and router to build the sub.

 

[Bushka]

To recap, some of you guys recommended the O Audio BASH amp:

O Audio - 500W BASH Subwoofer Amplifier

and the JL Audio 8w7-3:

8W7-3 - Car Audio - Subwoofer Drivers - W7 - JL Audio


I note this is advertised for cars. Is the 500w recommended, or is the 300w amp enough for what I'm doing (mostly for 5.1 with movies). I like the idea of the 500w (bigger is always better?) but for the extra $100 over the 300w is it worth it?

The rest of the system is going to be ceiling mounted speakers (on another thread). Not ideal, I know, but at least the sub will be optimal.

Before I go buying this stuff, are there any other ideas? Are these the right components for me to get? The room is pretty large but I have to think this sub will do the trick.

 

[lsiberian]

To recap, some of you guys recommended the O Audio BASH amp:

O Audio - 500W BASH Subwoofer Amplifier

and the JL Audio 8w7-3:

8W7-3 - Car Audio - Subwoofer Drivers - W7 - JL Audio


I note this is advertised for cars. Is the 500w recommended, or is the 300w amp enough for what I'm doing (mostly for 5.1 with movies). I like the idea of the 500w (bigger is always better?) but for the extra $100 over the 300w is it worth it?

The rest of the system is going to be ceiling mounted speakers (on another thread). Not ideal, I know, but at least the sub will be optimal.

Before I go buying this stuff, are there any other ideas? Are these the right components for me to get? The room is pretty large but I have to think this sub will do the trick.

I've always found external amps to be way easier. I hate having to mount a plate amp on the back of a sub. Either way it would be a good idea to have an EQ system of some kind too. A Peavey IPR1600 would get you plenty of power for dual subs. You could use a minidsp for EQ. If you want to do a plate amp the O-Audio should be fine.

 

[Bushka]

I've always found external amps to be way easier. I hate having to mount a plate amp on the back of a sub. Either way it would be a good idea to have an EQ system of some kind too. A Peavey IPR1600 would get you plenty of power for dual subs. You could use a minidsp for EQ. If you want to do a plate amp the O-Audio should be fine.

You have to know that I'm not well versed on all the components needed for an entertainment system. My understanding is that I need the following:

1. cable box to receive television channels
2. Blu Ray for discs
3. 5 speakers for a 5.1 surround system
4. sub woofer with amplifier
5. Receiver to hook everything together and amplify inputs for the speakers.

I do not know if I need an equalizer, but I assume it is something I could add later easily.

Also, I'm a little confused on the amplifier for the sub. I assume the sub needs its own amp instead of using the receiver to amplify the signal, so the signal coming from the receiver to the sub's amp is not "pre amplified" if that makes sense. Do I have that right?

Also, the BASH amp has an "auto on" feature which seems to make sense. I don't know if I have to manually turn on the other amp that you recommended each time I use the system.

Finally, I want to buy good components, but the cost adds up quickly and if something like a 300w sub will work for my application just as well as a 500w. Am I giving up much with a little smaller sub?

Thanks.

 

[lsiberian]

You have to know that I'm not well versed on all the components needed for an entertainment system. My understanding is that I need the following:

1. cable box to receive television channels
2. Blu Ray for discs
3. 5 speakers for a 5.1 surround system
4. sub woofer with amplifier
5. Receiver to hook everything together and amplify inputs for the speakers.

I do not know if I need an equalizer, but I assume it is something I could add later easily.

Also, I'm a little confused on the amplifier for the sub. I assume the sub needs its own amp instead of using the receiver to amplify the signal, so the signal coming from the receiver to the sub's amp is not "pre amplified" if that makes sense. Do I have that right?

Also, the BASH amp has an "auto on" feature which seems to make sense. I don't know if I have to manually turn on the other amp that you recommended each time I use the system.

Finally, I want to buy good components, but the cost adds up quickly and if something like a 300w sub will work for my application just as well as a 500w. Am I giving up much with a little smaller sub?

Thanks.

You would have to manually toggle the amp off and on, but you could leave it on if you wanted. I only turn mine on when I want the sub on. There are times(wife's shows) I leave it off.

Are we porting or sealing the sub?

 

[Bushka]

You would have to manually toggle the amp off and on, but you could leave it on if you wanted. I only turn mine on when I want the sub on. There are times(wife's shows) I leave it off.

Are we porting or sealing the sub?

OK, so the amp doesn't draw any power when not being used even while on.

I don't mind building the amp into the box but I could be persuaded either way I suppose. It would be one less component in the cabinet that way, but if there are drawbacks then that's not important.

I think I'll try for the vented box.

 

[TLS Guy]

OK, so the amp doesn't draw any power when not being used even while on.

I don't mind building the amp into the box but I could be persuaded either way I suppose. It would be one less component in the cabinet that way, but if there are drawbacks then that's not important.

I think I'll try for the vented box.

That driver is only suitable for car use sealed. For home HT is needs to be the vented design I sent you.

 

[Bushka]

So another 5 months has rolled by...

Yes, I'm back at it! It took me a few days to read back over everything I've been told on this forum and I do appreciate the effort many of you have made to help me get what I need for my living room. Your help is not wasted as I'm going ahead with the cabinet build now and have to finish designing this sub box.

I was looking at the specs for the OAudio 500W BASH amp recommended here and it says that the amp is designed for drivers rated at 4 ohms or greater. From the manual:

"CAUTION – This amplifier is designed for use with drivers that are rated at 4Ω or greater. Drivers whose nominal impedance rating is less than 4Ω can damage the amplifier. Driver combinations (this includes any configuration where there are multiple voice coils) that result in a load of less than 4Ω (when calculated using the driver’s nominal impedance) can damage the amplifier. Damage caused by low impedance loads are not covered by the warranty."

I looked at the driver also recommended here (the JL audio 8w7-3 pro) and it appears to be 3 ohms. It seems I can't use this amp and driver together. Am I reading it wrong?

Also, I want to be sure I got this right: I am going to determine the overall size of the box, Vt, by starting with Vb of 1.463 (from TLS Guy). I'm adding the following to Vb:

volume of air inside the vent,
volume displaced by the vent plywood itself,
volume of the driver,
volume of the plate amp,
volume of the figure 8 bracing.

Adding all these together will give me an internal volume I can use to make the box. One little complication is that it seems that adding the volume of the bracing makes it an iterative calculation. In other words, I need the volume of the bracing in order to tell me the Vt, but I can't calculate the bracing volume unless I know the dimensions of the box. I guess if I calculate the bracing a couple of times I will get very close. I know I'm probably making this more complicated than necessary, but better to obsess twice and cut once.

I think I prefer the plate amp for space reasons, but this will make it more complicated to build the box. I'm trying to visualize how I can fit a figure 8 brace into a smallish box with a plate amp and long internal port.

Thanks again for any help, and I PROMISE to start building this thing already!

 

[annunaki]

The W7 drivers, though rated at 3 ohms actually have a DCR much closer to a 4 ohm woofer. You should be fine using an 8W7 on the Bash amplifier.
As for the bracing get the dimensions you need with everything else accounted for. Then estimate your bracing volume based upon those dimensions and make small alterations from there.

Yes, I'm back at it! It took me a few days to read back over everything I've been told on this forum and I do appreciate the effort many of you have made to help me get what I need for my living room. Your help is not wasted as I'm going ahead with the cabinet build now and have to finish designing this sub box.

I was looking at the specs for the OAudio 500W BASH amp recommended here and it says that the amp is designed for drivers rated at 4 ohms or greater. From the manual:

"CAUTION – This amplifier is designed for use with drivers that are rated at 4Ω or greater. Drivers whose nominal impedance rating is less than 4Ω can damage the amplifier. Driver combinations (this includes any configuration where there are multiple voice coils) that result in a load of less than 4Ω (when calculated using the driver’s nominal impedance) can damage the amplifier. Damage caused by low impedance loads are not covered by the warranty."

I looked at the driver also recommended here (the JL audio 8w7-3 pro) and it appears to be 3 ohms. It seems I can't use this amp and driver together. Am I reading it wrong?

Also, I want to be sure I got this right: I am going to determine the overall size of the box, Vt, by starting with Vb of 1.463 (from TLS Guy). I'm adding the following to Vb:

volume of air inside the vent,
volume displaced by the vent plywood itself,
volume of the driver,
volume of the plate amp,
volume of the figure 8 bracing.

Adding all these together will give me an internal volume I can use to make the box. One little complication is that it seems that adding the volume of the bracing makes it an iterative calculation. In other words, I need the volume of the bracing in order to tell me the Vt, but I can't calculate the bracing volume unless I know the dimensions of the box. I guess if I calculate the bracing a couple of times I will get very close. I know I'm probably making this more complicated than necessary, but better to obsess twice and cut once.

I think I prefer the plate amp for space reasons, but this will make it more complicated to build the box. I'm trying to visualize how I can fit a figure 8 brace into a smallish box with a plate amp and long internal port.

Thanks again for any help, and I PROMISE to start building this thing already!

 

[TLS Guy]

Yes, I'm back at it! It took me a few days to read back over everything I've been told on this forum and I do appreciate the effort many of you have made to help me get what I need for my living room. Your help is not wasted as I'm going ahead with the cabinet build now and have to finish designing this sub box.

I was looking at the specs for the OAudio 500W BASH amp recommended here and it says that the amp is designed for drivers rated at 4 ohms or greater. From the manual:

"CAUTION – This amplifier is designed for use with drivers that are rated at 4Ω or greater. Drivers whose nominal impedance rating is less than 4Ω can damage the amplifier. Driver combinations (this includes any configuration where there are multiple voice coils) that result in a load of less than 4Ω (when calculated using the driver’s nominal impedance) can damage the amplifier. Damage caused by low impedance loads are not covered by the warranty."

I looked at the driver also recommended here (the JL audio 8w7-3 pro) and it appears to be 3 ohms. It seems I can't use this amp and driver together. Am I reading it wrong?

Also, I want to be sure I got this right: I am going to determine the overall size of the box, Vt, by starting with Vb of 1.463 (from TLS Guy). I'm adding the following to Vb:

volume of air inside the vent,
volume displaced by the vent plywood itself,
volume of the driver,
volume of the plate amp,
volume of the figure 8 bracing.

Adding all these together will give me an internal volume I can use to make the box. One little complication is that it seems that adding the volume of the bracing makes it an iterative calculation. In other words, I need the volume of the bracing in order to tell me the Vt, but I can't calculate the bracing volume unless I know the dimensions of the box. I guess if I calculate the bracing a couple of times I will get very close. I know I'm probably making this more complicated than necessary, but better to obsess twice and cut once.

I think I prefer the plate amp for space reasons, but this will make it more complicated to build the box. I'm trying to visualize how I can fit a figure 8 brace into a smallish box with a plate amp and long internal port.

Thanks again for any help, and I PROMISE to start building this thing already!

You have the correct additions to get to Vt from Vb. 100% correct.

I also think you will be fine with the Bash amp.

 

[lsiberian]

The bash amp will handle the 8w7.

 

[Bushka]

OK, so I'll design based on the JL driver and Bash plate amp. Take a look at the drawing below. I calculated a total volume of 2.0 cubic feet, which would work out to internal dimensions of 12" wide by 17" deep by 17.4" high. This makes installing figure 8 type baffles almost impossible.

The blue dotted box on the side is where the plate amp goes, and of course the driver and internal vent are facing down as shown. The internal vent will span from front to back, and I imagine will act as a pretty good stiffener in that direction.

My question is how crazy I have to go on stiffening this box. Given that the vent will provide good bracing, can I get away with one or two 1x2's or the like going in the side to side direction? In the drawing below, I inserted a green baffle that could be squeezed in between the vent and the plate amp (just to the left of the plate amp). I could dado this baffle in and cut a hole in the middle, but the top of the baffle will have to stop short of the top of the box because the vent is in the way. I'm hoping that bracing with 1x1 or 1x2's etc will be sufficient, as these can be added much more easily after the components are situated.

Anyway, not sure if this is too confusing to follow with this drawing, or if it makes sense.

 

[TLS Guy]

OK, so I'll design based on the JL driver and Bash plate amp. Take a look at the drawing below. I calculated a total volume of 2.0 cubic feet, which would work out to internal dimensions of 12" wide by 17" deep by 17.4" high. This makes installing figure 8 type baffles almost impossible.

The blue dotted box on the side is where the plate amp goes, and of course the driver and internal vent are facing down as shown. The internal vent will span from front to back, and I imagine will act as a pretty good stiffener in that direction.

My question is how crazy I have to go on stiffening this box. Given that the vent will provide good bracing, can I get away with one or two 1x2's or the like going in the side to side direction? In the drawing below, I inserted a green baffle that could be squeezed in between the vent and the plate amp (just to the left of the plate amp). I could dado this baffle in and cut a hole in the middle, but the top of the baffle will have to stop short of the top of the box because the vent is in the way. I'm hoping that bracing with 1x1 or 1x2's etc will be sufficient, as these can be added much more easily after the components are situated.

Anyway, not sure if this is too confusing to follow with this drawing, or if it makes sense.

Your design looks OK. However bracing is very important. You do have space for interlocking boards with holes in. These should be datoed into the side and top and bottom walls. I'm not a fan of butt joints. Dato joints seal much better and are stronger.

Two by four braces have been shown to do little good. Good Dato bracing actually makes the cabinet easier to construct, as you build from the inside out and it keeps everything lined up.