Under Couch Subwoofer?

[annunaki]

OK - last question! I see that the 10W1V2 comes in 4 and 8 ohm versions. Which should I get? Or does it matter? Does it come down to the amplifier I choose, i.e. 4 ohm = BASH 500 or 8 ohm = BASH 300?

4 ohm and the 300W BASH will be fine.

The sub will still hit in the 105db-106db with only 150 watts. It is quite efficient.

 

[GO-NAD!]

I decided to do some experimentation (which I should've done at the beginning!) and placed my Reel Acoustics RSW 1215 in the position where the under-couch sub would be placed. I took some measurements with my SPL meter in the best listening position and the results were horrendous! I zeroed at 80 dB, 80 Hz. Here's what I got:
63Hz = 92dB
50Hz = 77dB
40Hz = 82dB
31.5Hz = 70dB
25Hz = 66dB

When I moved the sub just 3 feet closer to the corner, which is right where my new component stand is supposed to go, I got this:
80Hz = 80dB
63Hz = 78dB
50Hz = 79dB
40Hz = 80dB
31.5 Hz = 79dB
25Hz = 75dB

I consider that to be excellent and not needing any equalization. But it's the wrong spot!!

I'm re-thinking the plan now. Sigh.....

 

[j_garcia]

3 feet is a pretty big move, so it doesn't surprise me that you got such a big change in response.

 

[lsiberian]

Time for an invisible sub.

 

[GO-NAD!]

3 feet is a pretty big move, so it doesn't surprise me that you got such a big change in response.

I wouldn't have thought so before, but then, I haven't done a lot of sub placement experimentation. I was surprised at the change, to say the least.

 

[GO-NAD!]

Time for an invisible sub.

Huh? I don't get it....

I am seriously reconsidering the under-couch sub now. I'm now thinking about a really compact sealed sub, that would have a footprint no larger than 1 square foot. As I mentioned before, I don't need it to have extremely deep FR. If I could build that is really compact and will give me very good spl down to about 28Hz and relatively flat, I'd be happy.

I'm just throwing that out there for comments...

 

[j_garcia]

I had my sub right in the corner and when I first moved to this place and it didn't sound right, and I knew the corner placement was the reason. I found a big null when I did some measurements. I moved it less than a foot from the corner and had a very noticeable change in response. It took me some adjustment to get it in a good compromise of a location to give me good enough response.

As for the tiny sub, the smaller you go, the harder it is to get a lot of output out of it, or at the very least it is going to take more power.

 

[GO-NAD!]

As for the tiny sub, the smaller you go, the harder it is to get a lot of output out of it, or at the very least it is going to take more power.

Yeah, I'm aware that it would be less efficient, hence the need for more power. The whole justification driving the sub build, is to gain some floor space. SWMBO is willing to entertain the idea on that basis. I just want to build a subwoofer!

The plan for an under-couch design hinged on getting a DCX to equalize the FR, due to the fixed location of the sub. However, when I took some measurements with my present sub in that location (had to move the couch of course), the FR was not good at all, as you can see in the related post. Then I got to thinking, if I equalize for the best FR in the best listening position (with regards to the mains), is it going to adversely affect the FR in other positions. My guess is yes. I have to take more measurements from other positions to confirm my suspicion.

Since the best listening position isn't the most common seating position (I have to temporarily place a chair there, as it blocks the path through the living room), I'm wondering if it's wise to equalize for that position.

In an effort to improve the FR of my mains, which are sitting on cabinets, (attached photo), I stuffed the ports with pieces of foam. The FR tightened up considerably, while significantly reducing the standing wave. In fact, it was better than placing them on stands 2.5 feet out from the front wall! I think the stuffing will reduce output a bit, but the NAD C372 can handle the extra load.

I guess what this really points towards, is to skip the DCX and build a sub with a small footprint. The extra funds freed up, by passing on the DCX, can go towards a more capable driver and more power. I'm thinking JL 8W7 and a BASH 500, vice 10W1V2 and BASH 300.

Something to think about. Annunaki, if you're reading this, I appreciate the effort you put into the under-couch design. What do you think about my present train of thought? Hopefully, it won't look like the train left the tracks...

 

[annunaki]

Yeah, I'm aware that it would be less efficient, hence the need for more power. The whole justification driving the sub build, is to gain some floor space. SWMBO is willing to entertain the idea on that basis. I just want to build a subwoofer!

The plan for an under-couch design hinged on getting a DCX to equalize the FR, due to the fixed location of the sub. However, when I took some measurements with my present sub in that location (had to move the couch of course), the FR was not good at all, as you can see in the related post. Then I got to thinking, if I equalize for the best FR in the best listening position (with regards to the mains), is it going to adversely affect the FR in other positions. My guess is yes. I have to take more measurements from other positions to confirm my suspicion.

Since the best listening position isn't the most common seating position (I have to temporarily place a chair there, as it blocks the path through the living room), I'm wondering if it's wise to equalize for that position.

In an effort to improve the FR of my mains, which are sitting on cabinets, (attached photo), I stuffed the ports with pieces of foam. The FR tightened up considerably, while significantly reducing the standing wave. In fact, it was better than placing them on stands 2.5 feet out from the front wall! I think the stuffing will reduce output a bit, but the NAD C372 can handle the extra load.

I guess what this really points towards, is to skip the DCX and build a sub with a small footprint. The extra funds freed up, by passing on the DCX, can go towards a more capable driver and more power. I'm thinking JL 8W7 and a BASH 500, vice 10W1V2 and BASH 300.

Something to think about. Annunaki, if you're reading this, I appreciate the effort you put into the under-couch design. What do you think about my present train of thought? Hopefully, it won't look like the train left the tracks...

What about doing some room treatments right behind the main L/R speakers rather than stuffing the vents??

Treatment up there will limit the reinforcement the room offers up there.

In any scenario, a DCX will be to your benefit. Not only can you properly integrate "ANY" sub into the room regardless of the position but it will also better integrate your mains with the sub.

What did the response look like with the sub in the couch location?? Were there large nulls or were they peaks? Peaks are easier to take care of than nulls.


How high does your current sub begin rolling off on the low end?

 

[GO-NAD!]

What about doing some room treatments right behind the main L/R speakers rather than stuffing the vents??

Treatment up there will limit the reinforcement the room offers up there.

In any scenario, a DCX will be to your benefit. Not only can you properly integrate "ANY" sub into the room regardless of the position but it will also better integrate your mains with the sub.

What did the response look like with the sub in the couch location?? Were there large nulls or were they peaks? Peaks are easier to take care of than nulls.


How high does your current sub begin rolling off on the low end?

Well, I'm using a Rives test tone CD, and the increments are pretty coarse, but this is what I got from the sub in the couch position zeroed at 80dB, 80Hz and the SPL meter in the best listening position:

100 Hz - 75dB
80 Hz - 80dB
63 Hz - 94dB
50Hz - 77dB
40Hz - 82dB
31.5 - 70dB
25Hz - 66dB

The huge peak at 63Hz could be lopped off by the DCX, I'm sure. But the sub appears to roll off steeply at 40Hz, which is not good at all. I don't know if the 10W1 has what it takes to overcome that. Plus, if I cut off that huge peak at 63Hz, what will the response look like in other listening positions? By flattening that peak, with reference to the best listening position, will I create a null in other positions?

In other words, I don't want to end up with a single sweet spot for listening. I'd rather make compromises with that position, than to make the SQ poor everywhere else. I'd rather have minor peaks and nulls everywhere, than great FR in one position and large peaks and nulls everywhere else. My opportunities for sitting down in the best listening position are few and far between. So maybe, the system would be best set up for general listening. Then again, I could probably use the DCX to do that too. I'm really not sure which way to go now.

As for room treatments behind the mains, that's not going to happen - wouldn't be permitted. As a living room and not a dedicated listening room, it doesn't provide me with a lot of flexibility.

 

[annunaki]

Here's the thing. I am willing to bet the native response of your "test" sub is beginning to drop off significantly from 40hz and down. It is probably not all room issues at that point. Decreasing the peak at 63hz by 10db or so is not going to significantly impact the response in other locations.

Also does the mic you are using require correction factor at lower frequencies like the radio shack meter does?

Have you done the same tests in the other locations with the woofer in the couch position to see what the those individual locations are as well as the averages? I would do this so as to get a better idea of how it may impact.

The enclosure I have designed so far will have no issues with output down to the 25hz range.

Well, I'm using a Rives test tone CD, and the increments are pretty coarse, but this is what I got from the sub in the couch position zeroed at 80dB, 80Hz and the SPL meter in the best listening position:

100 Hz - 75dB
80 Hz - 80dB
63 Hz - 94dB
50Hz - 77dB
40Hz - 82dB
31.5 - 70dB
25Hz - 66dB

The huge peak at 63Hz could be lopped off by the DCX, I'm sure. But the sub appears to roll off steeply at 40Hz, which is not good at all. I don't know if the 10W1 has what it takes to overcome that. Plus, if I cut off that huge peak at 63Hz, what will the response look like in other listening positions? By flattening that peak, with reference to the best listening position, will I create a null in other positions?

In other words, I don't want to end up with a single sweet spot for listening. I'd rather make compromises with that position, than to make the SQ poor everywhere else. I'd rather have minor peaks and nulls everywhere, than great FR in one position and large peaks and nulls everywhere else. My opportunities for sitting down in the best listening position are few and far between. So maybe, the system would be best set up for general listening. Then again, I could probably use the DCX to do that too. I'm really not sure which way to go now.

As for room treatments behind the mains, that's not going to happen - wouldn't be permitted. As a living room and not a dedicated listening room, it doesn't provide me with a lot of flexibility.

 

[GO-NAD!]

I am willing to bet the native response of your "test" sub is beginning to drop off significantly from 40hz and down. It is probably not all room issues at that point.

That did cross my mind, as the sub isn't a barnstormer, by any stretch. However, in the best position, it didn't start dropping off until I got down to 31.5 Hz. Even then, at 25 Hz, it was still only down 5 dB.

Also does the mic you are using require correction factor at lower frequencies like the radio shack meter does?

I was using a Rives test tone CD, which already has a set of compensated tones for the RS meter, which I was using.

Have you done the same tests in the other locations with the woofer in the couch position to see what the those individual locations are as well as the averages? I would do this so as to get a better idea of how it may impact.

I plan to do that later today.

 

[annunaki]

The only way to ensure that room gain is not coming into play (with the natural response of the woofer) would be to do a ground plane measurement outdoors away from obstructions with the mic at 6ft. from the driver. You then know what is room gain and what is not.

I am not doubting that the placement may be the culprit here, but I also want to ensure other variables are covered.

A 10W7 in a sealed enclosure of 1.35ft^3 net volume could be done with a 13 x 13 x 22 enclosure that would allow for .2ft^3 for displacement. Using a small bit of parametric eq would net an anechoic f3 of 30hz.

This response uses a lowpass x-over of 80hz 2nd order and an infrasonic filter 4th order at 20hz and +3.0db eq at 30hz with a 'Q' of 2.0. This keeps the max excursion withing the xmax +10% range (below any audible distortion level). This is all very easily achieved with a DCX2496.

Your in room response will be easily usable down to 20hz. My in room response is usable to 15hz with my 12W7.

As you can see below, it would be +/-3db from 30hz-90hz with minimum 107db output capability (anechoic). In-room would be at least +3db higher or more.

That did cross my mind, as the sub isn't a barnstormer, by any stretch. However, in the best position, it didn't start dropping off until I got down to 31.5 Hz. Even then, at 25 Hz, it was still only down 5 dB.



I was using a Rives test tone CD, which already has a set of compensated tones for the RS meter, which I was using.



I plan to do that later today.

 

[GO-NAD!]

The only way to ensure that room gain is not coming into play (with the natural response of the woofer) would be to do a ground plane measurement outdoors away from obstructions with the mic at 6ft. from the driver. You then know what is room gain and what is not.

I am not doubting that the placement may be the culprit here, but I also want to ensure other variables are covered.

I suspect that there is some room gain in placement closer to the corner. The manufacturer's specs state a FR of 27 -150 Hz, but with no +/- 3dB variation. I would guess that the -3dB (anechoic) point is a bit higher than 27Hz. However, time permitting, I think I'll try some measurements outside. How far from the house, should the sub be placed? My deck is 12' wide. Would that be far enough from the side of the house?

A 10W7 in a sealed enclosure of 1.35ft^3 net volume could be done with a 13 x 13 x 22 enclosure that would allow for .2ft^3 for displacement. Using a small bit of parametric eq would net an anechoic f3 of 30hz.

This response uses a lowpass x-over of 80hz 2nd order and an infrasonic filter 4th order at 20hz and +3.0db eq at 30hz with a 'Q' of 2.0. This keeps the max excursion withing the xmax +10% range (below any audible distortion level). This is all very easily achieved with a DCX2496.

The crippler here, is that a 10W7 is about $400 and a 8W7 is about $280 - in the US. I have yet to find any retailer in Canada selling these models. I can guess that shipping them from the US, even with the dollar around par, would cost me about $550 and $400, respectively. If I went with either, I can forget about the DCX, as my budget would be blown.

In contrast, I can get a 10W1V2 shipped from crutchfield.ca for $150, including tax. That's a big difference.

Going with a W7, would hinge on being able to acheive an acceptably flat FR without equalization.

The extension acheived in the 10W7 that you modeled is way deeper than I need. Can you model a 8W7 in a smaller enclosure to see what you come up with. I tried messing around with WinISD, but I'm clueless...

 

[GO-NAD!]

Just to add to my last post, I took some more readings with the sub in the couch position and the SPL meter in some other typical seating positions. The FR was very similar in each of those positions. So, I guess if the sub was equalized for the best listening position, it should work OK for the other seats.

If you look at the photo of the living room, you'll see a small table behind the chair where all my components sit. Well, under that table is where my present sub sits. The FR in that position is similar to the exact opposite position on the opposing wall, right beside the end table, with a slight edge going to the end table position.

After all the hemming and hawing, I need to figure out what the best option will be.

The undercouch design will absolutely require equalization. For some, that may be no big deal. For me, it means another component, more cables (more expense, a learning curve for operation and setting. Each time the couch is moved, the sub will have to go with it, meaning the equalizer will have to be re-set.

On the other hand, I won't need to apply a finish, which equals less time and money.

A free-standing sub will take up some floor space and might need equalization.

If no equalization is required, because of placement flexibility, that's all the expense, bits & pieces, time and effort not required as well. If I finish it nicely, there will be bragging rights as well.

You might get the impression that I'm trying to talk myself into forgoing the undercouch enclosure and going with a conventional design.

You see, if I can get away with not needing equalization, I'd be happy. It would be one more thing I wouldn't have to mess around with. If I'm going to need equalization regardless of the enclosure type, I may as well resign myself to the fact that I'll have to make the effort to incorporate it.

A really compact design - I'm talking 12"x12"x24", or so, using perhaps a 8W7 in a sealed enclosure - would be flexible for placement. That, in itself may negate the need for an equalizer. Might be cheaper too, when considered from an overall expense aspect.

 

[annunaki]

I suspect that there is some room gain in placement closer to the corner. The manufacturer's specs state a FR of 27 -150 Hz, but with no +/- 3dB variation. I would guess that the -3dB (anechoic) point is a bit higher than 27Hz. However, time permitting, I think I'll try some measurements outside. How far from the house, should the sub be placed? My deck is 12' wide. Would that be far enough from the side of the house?



The crippler here, is that a 10W7 is about $400 and a 8W7 is about $280 - in the US. I have yet to find any retailer in Canada selling these models. I can guess that shipping them from the US, even with the dollar around par, would cost me about $550 and $400, respectively. If I went with either, I can forget about the DCX, as my budget would be blown.

In contrast, I can get a 10W1V2 shipped from crutchfield.ca for $150, including tax. That's a big difference.

Going with a W7, would hinge on being able to acheive an acceptably flat FR without equalization.

The extension achieved in the 10W7 that you modeled is way deeper than I need. Can you model a 8W7 in a smaller enclosure to see what you come up with. I tried messing around with WinISD, but I'm clueless...

Let me talk to my guy at the local JL dealer. I will see what I can get a 10W7 for and you could pay the shipping with the exact cost of the driver. He usually hooks me up pretty well.

Here is the response in a 1.3ft^3 sealed enclosure (you could keep the same suggested dimensions of the 10W7 enclosure. Native +/-3db response is from 36.74hz - 95hz at 104.7db or more anechoic. This includes using a 20hz high-pass filter 2nd order or higher with 500 watts rms.

 

[GO-NAD!]

Let me talk to my guy at the local JL dealer. I will see what I can get a 10W7 for and you could pay the shipping with the exact cost of the driver. He usually hooks me up pretty well.

Here is the response in a 1.3ft^3 sealed enclosure (you could keep the same suggested dimensions of the 10W7 enclosure. Native +/-3db response is from 36.74hz - 95hz at 104.7db or more anechoic. This includes using a 20hz high-pass filter 2nd order or higher with 500 watts rms.

I installed WinISD Pro 0.50a7, to see if I could understand how to use it, but it's not working for me. I keep getting error messages like "floating point division by zero" and "invalid floating point operation". Is there a bug in this program, or might it not have installed properly?

36.74 Hz for the 8W7 in that sealed enclosure seems a bit high - what could I expect in-room to be? Can you get prices for both the 8W7 and the 10W7? If I were to go with either, I can forget the DCX, as the budget would be busted.

I might be able to spring for a BFD sometime down the road though. As mentioned before, if I can get away without having to equalize at all, I'd be happy.

 

[GO-NAD!]

I am willing to bet the native response of your "test" sub is beginning to drop off significantly from 40hz and down. It is probably not all room issues at that point.

Annunaki, you know your stuff! I tested my sub outside, about 30' from the house and guess what - it does start to drop off significantly at 40Hz! At 31.5 Hz, it was down 6dB and at 25Hz it was down 16dB! I knew it wasn't a great sub, but I didn't realize how anaemic the response really was.

 

[just-some-guy]

kinda interesting thread. as i am thinking about taking my kappas, puttin em in a 1.25cf per side car box. and puttin that behind my chairs. hopin that would give me some more SLAMMM. idk

 

[annunaki]

Annunaki, you know your stuff! I tested my sub outside, about 30' from the house and guess what - it does start to drop off significantly at 40Hz! At 31.5 Hz, it was down 6dB and at 25Hz it was down 16dB! I knew it wasn't a great sub, but I didn't realize how anemic the response really was.

Commercial subs have MANY compromises. Many of which result in a lower quality product to the end user.

The 8W7 without eq will easily surpass what you currently have.

I will get some pricing for you on those two drivers.

The under couch option would be night & day (with a DCX) compared to your present set up.