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Discussion Starter #1
I have some 12" subwoofers that I will be placing at the back of our room. The door was installed in the wrong place when they got the wrong size the first time. :sneeky: Therefore the subwoofer/subwoofers need to go into the corner away from the doorway must be recessed into a large platform/Helmholtz Resonator. :blink: On each side of the room are the enclosures that are 2 feet deep and 3 feet high. There are some holes on them under the carpet to allow lower frequencies to get into them. They each go into the center of the room which is 13' 6" wide except for a space between them about 24". They are currently filled with insulation and on each end at the center of the room they are closed off with a plywood covering. It is not visible because a couch sits in front of the empty area and a top was added so the area across is near the same level. Since I would like to recess the subwoofers into these areas in the back of the room and they are passive amps and they have ports, I have a few questions.

1. How much insulation do I remove for the ports?

2. Do I run a longer wire to the subwoofers and place the amps in the area with the gap, leave them on all the time? Do I leave an area above the subwoofers to place the amps on? I had some difficulties getting the wire to each amp. They would clip the amps if I used two wires or if the connection was loose. I have not tried longer wire yet but this idea worries me.

3. How will placing them in the enclosures effect the sound quality?

4. Do I place them inside flush against the front, or leave room for them to sit outside some?

They are Crystal Acoustics 12" subwoofers which I have bypassed the amplifiers on using MA-500 mono amplifiers. There is 11" to the doorway and they are 20" long.

5. Do I just do the one by the door or both to make it look or sound uniform?
 

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Re: Best way to install subwoofer inside a cavity?

Therefore the subwoofer/subwoofers need to go into the corner away from the doorway must be recessed into a large platform/Helmholtz Resonator.
From that point on I'm totally lost. Any chance of posting a pic to see what you're talking about? It would make it a whole lot easy to understand.
 

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Discussion Starter #4 (Edited)
Re: Best way to install subwoofer inside a cavity?

Photos of how it is right now. I have cables ordered to do the install already. Firing the subwoofers at the riser makes the response worse so I would like to aim them into the room.





The current measurements if I were to raise my front row higher. Not sure about that one yet but I do know they sound better for decay in the corners anyways. There are four total. No eq applied.



Older photos of the installation of my attempt at Helmholtz Resonators. I did not have excel to calculate the hole size at the time and they have been more recently filled with insulation.

During construction





Before filling with insulation



After filling with insulation



There is alot of it in there. I shoved it in with my legs.
 

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Discussion Starter #5
Re: Best way to install subwoofer inside a cavity?

Do you think I would be better off to use the two in the front in corners and place the other ones slightly inwards then? I'm sure it's not going to make much difference if I move them away from the side walls. There seems to be plenty of available room for them to breath. :huh: There are two 3" ports on the lower back of the subs.
 

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Discussion Starter #6
Re: Best way to install subwoofer inside a cavity?

Brown is a measurement with the mic located lower than earlier, this time the subwoofer by the door is covered in about 4 feet of blankets and pillows on 3 sides, and there is a peice of plywood laying on top. There is practically no room for the ports also so we are looking at what might be close to the worst outcome of enclosing only one sub. Green is with nothing on it. Note these are without the SPL calibrated because I am not intrested in SPL at this time. It looks like I really hurt the response level but I improved the dip at around 60Hz.
 

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Re: Best way to install subwoofer inside a cavity?

This is where you want to put the subs, one on each side?

2023472502_23c7317418_o.jpg

The Crystal Acoustics 12" subwoofers are already in a cabinet and you want to recess them into the corners as shown above, correct? If so what size cabinet and what tuning frequency of the Crystal subs?
 

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Re: Best way to install subwoofer inside a cavity?


We really can't get a feel for what you want to do with those pictures. Maybe some kind of drawing of the room layout would be more helpful.

1. How much insulation do I remove for the ports?
I assume from that that the ports are not on the front side with the driver. If you had to push the insulation in with your feet, that tells me it's pretty densely packed. So, I expect you'd have to take out enough to leave an air space around the sub, and leave venting at the opening where the sub is recessed. Otherwise your ported sub essentially becomes non-ported.

2. Do I run a longer wire to the subwoofers and place the amps in the area with the gap, leave them on all the time? Do I leave an area above the subwoofers to place the amps on? I had some difficulties getting the wire to each amp. They would clip the amps if I used two wires or if the connection was loose. I have not tried longer wire yet but this idea worries me.
I like to keep my electronics in the equipment rack. Sounds to me like the enclosures are too densely packed with insulation to allow for adequate cooling of an amplifier.

3. How will placing them in the enclosures effect the sound quality?
If the ports were front-firing, I'd say "little to nothing. " With the ports firing inside the enclosure into packed insulation - hard to say.

4. Do I place them inside flush against the front, or leave room for them to sit outside some?
Flush. Hanging them out won't accomplish anything.

Regards,
Wayne
 

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Discussion Starter #10
Re: Best way to install subwoofer inside a cavity?

They would be sharing the same cavity. What I have decided to instead of using the subwoofers I have in there, it to do this:

Place two subwoofers in the front corners - each bridged with an MA-500
Place single subwoofer under the center channel using the internal amp (optional, currently doing this). There is room for only one.

Set speakers to large - This elminates distortion from the internal amp of the center channel sub, and gives me a 75dB target for the XA2. FYI when I calibrate the SPL meter using REW and DVE to 75dB, then use REW internal sub caclulation pink noise it = 85dB. This is with the output in REW at 50 in my mixer. Bruce says the XA2 is normal output of the subs according to XA2 specs so I will have to go by that.

Next I am going to use my new cables and buy two in-wall subwoofers for the back corners. Ones that have front firing ports also and I would prefer them to be powered if possible.

As it is the measurement tracks according to my subwoofer specs of 30Hz extention unless I add two 3dB boost from 25Hz - 35Hz, with an optional boost around 60Hz that does very little as that is my steel ceiling/concrete floor room node. It is a distance from floor to ceiling (above ceiling tiles) of around 8' 7".

Rather than to place the front row higher, since my little experemint shows me that the sub range around 60Hz does not cancell when enclosed by large absorption at the sides and top at the rear of the room, I expect 60Hz dip to improve into target range. With the added SPL of two more subs, I also expect to have the 25Hz or lower extention naturally, but there will be more cuts using the BFD.

With more subwoofers, (what will be one extra than previously measured, or not) I will be able to use the small setting on the speakers again, although I do notice that the overall SPL level is higher, and the null improved, by using the large setting.

That is the plan.
 

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Discussion Starter #12
Re: Best way to install subwoofer inside a cavity?

The Velodyne SC-600IFIC In-Floor/In-Ceiling Passive Subwoofers look nice also. Only $ 1K plus shipping lol.
 

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Discussion Starter #13 (Edited)
sealed of front ported 12" design for inside another enclosure

I have an area in the back of the room I wish to place subwoofers. Due to the limitations of the room dimensions they must be placed inside pre-exsiting enclosures. See above.

I would like a pair of 12" subwoofers in the back corners of the room with FR of around 30Hz-150Hz that I could power with my MA-500 mono amps. The amplifiers are rated 125W @ 8ohm 180W @ 4ohm. I would like them to be fairly hidden. Are there any ideas on what will work well? I have a hotglue gun, hammer, drill, jigsaw, table saw, and access to renting tools or having custom woodwork done.

Cheap is good here but I don't want audible distortion or the subs to bottom out. Just looking for anything that will work, sound good, and be cheap. Budget is somewhere around $500.00 or less for materials and the drivers.

Edit: Title should have read sealed or front ported
 

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Re: Best way to install subwoofer inside a cavity?

So are you going to have a total of 5 subwoofers?

That in wall sub you posted looks like it could be a good solution. Doesn't look like it has any kind of port so it would basically act like a sealed sub using your wall as the box. I see you also posted a thread about building a DIY sub back there inside a pre-existing enclosure, so what enclosure are you placing these subs in at the back of the room?

What kind of subs are you using at the front? Adding boost to a ported sub below its tuning point is not such a good idea. Below tuning the driver and port are working against each other and the driver is more likely to bottom out. Adding two more subs tuned at 30hz won't help under 25hz, you'll need a sub that is designed to work in that range.
 

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What enclosures at the back of the room are you installing these into? More importantly, what are the dimensions?

If the enclosures are pre-built and you have the amps, you could build a pretty nice setup. I personally would suggest building one larger more capable sub. You mention that you want distortion free bass without bottoming the woofer but you don't say how loud you listen. If you're looking to do this into the reference level range with WOTW you'll need something big :bigsmile:

You could do a FI-18 with an EP2500 for that budget and it would destroy that in wall sub you posted on the other thread.
 

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Discussion Starter #16
re: Sealed or front ported 12" design for inside another enclosure

On each side of the room is a Helmholtz Resonator/platform area that each measures 3ft high 2 feet deep, and something around 11' 6" wide. They have holes in them and lots and lots of insulation. I have 3 12" subwoofers that I fit in the front of the room already, and I am worried if I had a larger sub, they would not work well together. I listen at around -10dB reference level. I used to listen to reference level with one sub before my receiver died. There is currently around 105dB peaks but with only 3 12" subwoofers, I have to set the output of the XA2 for my speakers as large as this gives me +5dB gain, but still seems to apply some sort of crossover in the pink noise measurements I did. I think that 5 X 12" drivers are about as good as an 18" as far as SPL goes if I am not mistaken. Also I don't think I will be affording this very soon, just exploring my options.
 

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re: Sealed or front ported 12" design for inside another enclosure

On each side of the room is a Helmholtz Resonator/platform area that each measures 3ft high 2 feet deep, and something around 11' 6" wide. They have holes in them and lots and lots of insulation.
Are these in the back of the room? I got the impression they were in the front. Are you enclosing the subs into them?

I have 3 12" subwoofers that I fit in the front of the room already, and I am worried if I had a larger sub, they would not work well together.
Why would this be the case? The bigger sub would out perform all of your other subs by far, not just with output but with extension and distortion as well. IMO your best bet is to build one of these and use if for the LFE and use the 3 subs you have up front to supplement your mains. Adding 2 more of what you have now won't gain you much if anything in output or extension. About the only thing you might gain is even response across your listening area, but it's just as likely that things will get worse.
 

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Discussion Starter #18
Re: Best way to install subwoofer inside a cavity?

I was thinking I would build an enclosure to the specs in the manual of whatever sub it was. In the front of the room there are 3 X 12" Crystal Acoustics subwoofers. Two I am powering with Bridged MA-500 mono amps. These amps bridged each see a 2ohm load and I am impressed the protection has not came on for them for some testing I gave them thus far. The third subwoofer in the center is powered with the supplied internal amplifier. I have three more of the amps not in use because there is audible distortion at the crossover frequency range when speakers are set to small, which I am currently not doing.

I do not hear the subwoofers bottom out, but then I am not sure I would really be listening correctly. I used to have 2 kicker comp 15" speakers powered by single mono amps and they would bottom out quite often with a thunk noise to them.

If adding larger speakers to extend the FR in the rear of the rooms corners is disirable and will not result in boomy bass, I am all for it. I want them in the corners however because this causes a very tight bass to be heard in my room.

This is really meant to be family HT, and I am worried anything such an 18" might send my parents or younger cousins running out the room. If I can get away with high quality12" woofers, I will be very pleased. With four 12" I have audible 25 Hz extention at target level so I thought adding another might do the same. Maybe reserve the larger subs for the next HT project should I ever get around to another one..
 

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Discussion Starter #19
re: Sealed or front ported 12" design for inside another enclosure

Yes the enclosures are in the rear of the room. I will consider some larger subs to suppliment the other ones if adding more 12" isn't going to improve things. The lower extention with subwoofers in the rear of the room is not as good for the front, but improves the peak in the back of the room around 30Hz. In the back of the room is around 20Hz or lower extention already. I wonder if adding larger subs in the back of the room might not just cancel more of the front in the room or too much in the back? Maybe I just need a larger one in the front?
 

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Discussion Starter #20
re: Sealed or front ported 12" design for inside another enclosure

I just remembered that adding more to the front isn't going to help the 60Hz room node. :duh:
 
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