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Discussion Starter #1
So I'm planning to build 2 matching subs for my home theater system which will actually also serve as stands for my front speakers since they're bookshelf type speakers.

What I've been thinking is that I don't need tons of bass, and I want to do it cheap, so I got looking at these Dayton SD27A-88 http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-486# subs
They're pretty low power, but they seem to be able to get down decently low.

I plugged all the numbers from Dayton's website (http://www.daytonaudio.com/index.php/loudspeaker-components/loudspeaker-drivers-by-type/subwoofers/sd270a-88-10-dvc-subwoofer.html) into WinISD to create some plots.
They seemed fine to me, 4.691ft^3 cabinet tuned to 24.36Hz with a 2.5" x 2.83" vent. WinISD's plot says that I should be able to get those low frequencies alright
Here is the plot: http://i.imgur.com/kso1I.jpg

Now firstly does this seem reasonable?

Secondly, I got a bit confused after I looked at possibly doing the same thing with 12" subs from this line of Daytons.
I plugged all the numbers in from the spec page on Dayton's website for the 12" sub (http://www.daytonaudio.com/index.php/loudspeaker-components/loudspeaker-drivers-by-type/subwoofers/sd315a-88-12-dvc-subwoofer.html)
And I come out with specs of 2.762ft^3 tuned to 29.47Hz with a 3" x 5.59" vent.
Here is the plot: http://i.imgur.com/zGxcc.jpg

It seems weird to me that WinISD suggests that the larger more powerful sub use a cabinet about half the size and that it be tuned to a higher frequency.
What is it about the specs that would make this much of a difference to the suggested ported cabinet?
Am I entering something wrong?

Here are screenshots of the two subs as I have them entered in WinISD:
10" sub: http://i.imgur.com/nhwxW.jpg

12" sub: http://i.imgur.com/NjXC6.jpg

Can anyone comment on either of my questions? (do both designs seem reasonable based on the specs? & why the drastic differences in cabinet designs?)
Any help will be greatly appreciated.
 

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So I'm planning to build 2 matching subs for my home theater system which will actually also serve as stands for my front speakers since they're bookshelf type speakers.

What I've been thinking is that I don't need tons of bass, and I want to do it cheap, so I got looking at these Dayton SD27A-88 http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-486# subs
They're pretty low power, but they seem to be able to get down decently low.
My only apprehension is the distortion they might produce. Something like an RS-270 for example, will have a similar frequency response, but much lower distortion.

I plugged all the numbers from Dayton's website (http://www.daytonaudio.com/index.php/loudspeaker-components/loudspeaker-drivers-by-type/subwoofers/sd270a-88-10-dvc-subwoofer.html) into WinISD to create some plots.
They seemed fine to me, 4.691ft^3 cabinet tuned to 24.36Hz with a 2.5" x 2.83" vent. WinISD's plot says that I should be able to get those low frequencies alright
Here is the plot: http://i.imgur.com/kso1I.jpg

Now firstly does this seem reasonable?[/quote]

Modeling such a box, you exceed x-max at 35hz with only 30w of input. SPL hovers around 103db. There is a very sharp roll off right before vent tuning, which is part of a somewhat high-ish group delay. Personally, in the same box, I would tune to about 19hz for a more shallow rolloff towards tuning. Max SPL is somewhat traded away, but the in-room frequency response will likely be a lot smoother and less of that "bloated vented sub" sound. Of course power handling drops to 20w...are you sure you don't want to use superior drivers? Sometimes it's not about how loud you want it, but how "effortless" you want everyday loudness. The less distortion and group delay (and the shallower the rolloff), the less attention the subs will draw to themselves.. IMO.

Secondly, I got a bit confused after I looked at possibly doing the same thing with 12" subs from this line of Daytons.
I plugged all the numbers in from the spec page on Dayton's website for the 12" sub (http://www.daytonaudio.com/index.php/loudspeaker-components/loudspeaker-drivers-by-type/subwoofers/sd315a-88-12-dvc-subwoofer.html)
And I come out with specs of 2.762ft^3 tuned to 29.47Hz with a 3" x 5.59" vent.
Here is the plot: http://i.imgur.com/zGxcc.jpg

It seems weird to me that WinISD suggests that the larger more powerful sub use a cabinet about half the size and that it be tuned to a higher frequency.
What is it about the specs that would make this much of a difference to the suggested ported cabinet?
Am I entering something wrong?
The main difference is a much lower Qes (electromagnetic damping) of the woofer indicating a stronger motor structure. The smaller woofer has a Qes = .5 and the larger woofer a Qes = .37

Since the smaller woofer has less motor damping, it needs to be damped by the box (a larger box) while the larger woofer is damped moreso electrically, so it doesn't need a larger box. Don't worry, you're not doing anything wrong. I'm not personally quite satisfied with the way the drivers model, though.
 

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Discussion Starter #3 (Edited)
My only apprehension is the distortion they might produce. Something like an RS-270 for example, will have a similar frequency response, but much lower distortion.
Interesting.. I hadn't really considered working with that speaker, as it's labelled as a standard "woofer".. That being said, the specs look ideal for my requirements.

I used the rs125's in a pair of bookshelf speakers I built, the microbes, and I really like them.

I entered the specs in winISD and here's the plot it came up with, along with a 4.06 ft^3 cabinet @ 24.82Hz using a 2.5" x 3.44" port
http://i.imgur.com/mXUWY.jpg

Would you go with these specs?
I've discovered that there is a lot to cab design for a subwoofer, and most of it is above my level of understanding.

Also, Do you think this Sub plate amp http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-804 (240w @ 4 ohm) or perhaps this amp http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-813 since I'd just be building the plate amp into its own cabinet anyways (and this one appears to have more adjustments available), would work well for 2 of these built into separate enclosures wired in parallel for 4 ohms?

My plan is to build two of these cabs in sort of a tower style so that they can act as stands for my front bookshelf style speakers.

Does this all seem like an alright idea?

Thanks a lot for the help with this.
 

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thinking cheap, I have one of these SD315A-88 12" out in my shop in a 4.2ft^3 box tuned to 18Hz with two 3" ports 21" long and it sounds great. It's relatively efficient and a quality driver. I sometimes Plug one of the ports and that tunes the box to ~ 14Hz for better transients and a little less low end when I'm listening at night so I don't bother the neighbors.

cheers
rev.
 

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Discussion Starter #5
thinking cheap, I have one of these SD315A-88 12" out in my shop in a 4.2ft^3 box tuned to 18Hz with two 3" ports 21" long and it sounds great. It's relatively efficient and a quality driver. I sometimes Plug one of the ports and that tunes the box to ~ 14Hz for better transients and a little less low end when I'm listening at night so I don't bother the neighbors.

cheers
rev.
I just plotted that driver with those cabinet specs in winisd and it looks odd to me. the output seems to drop off steadily below 80Hz, down -7db at 20Hz.

http://i.imgur.com/VmoX1.jpg
 

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Interesting.. I hadn't really considered working with that speaker, as it's labelled as a standard "woofer".. That being said, the specs look ideal for my requirements.
the dayton reference series drivers are flat out a smart choice - the RSS315 and RSS270 are undoubtably great choices as woofers. thanks to their shorting ring optimized motors, distortion is low. They don't have quite the throw of a dedicated subwoofer like a CSS Trio 12, though. Which is what I recommend making the step up to ;P

http://i.imgur.com/mXUWY.jpg

Would you go with these specs?
I didn't model it myself yet, but looking at the transfer function graph, it's probably tuned a smidgen too high. I would tune this at 20hz in a 4.6 cu ft box instead. Less flat of an anechoic response, but a better mating to the effects of rooms and thus it should have superior sound quality thanks to the gradual shallow rolloff towards the tuning frequency.

end of the day though, even the RS 270 which like you said is a woofer, doesn't have the kind of excursion that IMO a memorable sub will have :whistling: though it IMO is a better choice than the other 10" woofer you're looking at.

I just plotted that driver with those cabinet specs in winisd and it looks odd to me. the output seems to drop off steadily below 80Hz, down -7db at 20Hz.

http://i.imgur.com/VmoX1.jpg
Such a frequency response looks very smart to me and a pretty good mate with room gain. I prefer an anechoic F3 in the region around 25hz to 35hz however this is splitting hairs as the F4 is in that region and the room will have its own effect on frequency response. At the end of the day a good setup will have some level of EQ to get response clean.
 

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Discussion Starter #7
I didn't model it myself yet, but looking at the transfer function graph, it's probably tuned a smidgen too high. I would tune this at 20hz in a 4.6 cu ft box instead. Less flat of an anechoic response, but a better mating to the effects of rooms and thus it should have superior sound quality thanks to the gradual shallow rolloff towards the tuning frequency.

end of the day though, even the RS 270 which like you said is a woofer, doesn't have the kind of excursion that IMO a memorable sub will have :whistling: though it IMO is a better choice than the other 10" woofer you're looking at.
Interesting, I had always thought that a flatter response is desirable, thinking that you would want even amplitude at all frequencies. Why is it that a shallow roll off towards the tuned frequency is better?

Here's my dilemma.. I'm hoping to drive 2 subs with the Dayton 240w @ 4ohm amp. What sub would you recommend for clean bass reproduction with only 240w to drive them?
Or do I really need to run 2 of those amps?..
 

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Interesting, I had always thought that a flatter response is desirable, thinking that you would want even amplitude at all frequencies. Why is it that a shallow roll off towards the tuned frequency is better?
A flatter response IS desirable. In the majority of rooms, you can expect a shallow rise in response below roughly 30hz or so because of the long wavelengths at play "combining". if your speaker is too flat in a "anechoic model" there's a good likelyhood that it will sound "sluggish" or "bottom heavy" when placed in a room. The shallow rolloff leads you to approxomiate a likely flat in-room response :T

Here's my dilemma.. I'm hoping to drive 2 subs with the Dayton 240w @ 4ohm amp. What sub would you recommend for clean bass reproduction with only 240w to drive them?
For clean bass reproduction, you want a large, linear motor of some sort, and shorting rings.

A pair of these:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-445

perhaps?

Or do I really need to run 2 of those amps?..
I strongly recommend it. a pair of these kits:

http://www.creativesound.ca/details.php?model=TRIO12BASH300KIT

perhaps. The advantage of high excursion, high power handling, low distortion true subwoofer drivers will be well worth it when you're over and done with it, IMO. Or maybe two RSS390s :D
 

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Discussion Starter #9
I strongly recommend it. a pair of these kits:

http://www.creativesound.ca/details.php?model=TRIO12BASH300KIT

perhaps. The advantage of high excursion, high power handling, low distortion true subwoofer drivers will be well worth it when you're over and done with it, IMO. Or maybe two RSS390s :D
Maybe I am just better off to put all my sub money into one better sub, and then build a dummy stand to the same dimensions.. just for the symmetry.

Thanks for the link.. Shipping within Canada is definitely a nice perk of ordering from css.
 

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Maybe I am just better off to put all my sub money into one better sub, and then build a dummy stand to the same dimensions.. just for the symmetry.
Nope. One superior sub will always be outperformed in-room by two lesser subs. It's the nature of how bass interacts with the room. You want as many spaced sources of bass in the room in order to randomize excitation of room modes.
 

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Discussion Starter #11
Hm.. good to know. I've got to do some thinking on this.

Nope. One superior sub will always be outperformed in-room by two lesser subs. It's the nature of how bass interacts with the room. You want as many spaced sources of bass in the room in order to randomize excitation of room modes.
 

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The cheapest way to do amplification, is generally to pick up a single pro audio amplifier and drive two woofers off of it, rather than a plate amp.

IE Two Dayton 15" RSS 390s + One Crown XLS 1500 for example
 

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Discussion Starter #13
So I've decided that long term I will build two of these trio12 bash300 kits, but for right now I'm going to just build one.
I'm going to work up some specs with winISD and see what I come up with.
 

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get some rough dimensions and I will try modeling you an ML-TL for them when I get home today. This will factor in the effect of internal standing waves on the response.
 

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Discussion Starter #15
Here's the transfer function magnitude graph I came up with at 4cuft tuned to 18hz
http://i.imgur.com/0vxTg.jpg

WinISD suggested 20hz tuning, but the plot looked flatter.. Do you think 18hz would be a better idea? Or even lower?
http://i.imgur.com/iAbjd.jpg

My next concern is the cone excursion.. I hadn't ever considered this before, since I'm new to this, but is this a concern?
http://i.imgur.com/nzW4i.jpg
I've read about people modifying the bash plate amps to cut off the low frequency at a certain point.. Is this hard to do?

And then my port speed. I'd like to not have to use super long ports, so I plugged in a 3" x 9.66" port spec which gives a maximum port air velocity of 69m/s at 17.4hz. Is that alright?
http://i.imgur.com/VDNj3.jpg
 

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Discussion Starter #16 (Edited)
get some rough dimensions and I will try modeling you an ML-TL for them when I get home today. This will factor in the effect of internal standing waves on the response.
Okay, so looking at this again, and taking my desired cabinet size into consideration, it looks like I"d actually need 4.68cuft, which doesn't really change things too much.
Here's 4.68cuft @ 18hz
http://i.imgur.com/H5kfK.jpg

So I'd like to have a cabinet that's 3' tall by 1.25' wide and 1.25' deep. This comes out to 4.68cuft.

EDIT:
Just took into consideration the volume of the plate amp, the manual says it's 6x9.875x3.5", or 207.375cuin or .12cuft. So technically I suppose my box would physically be 4.68cuft with 4.56cuft of volume.
I think winISD takes into consideration the volume of the driver since I entered all it's dimensions in its profile.
I'm not sure if it takes the port volume into consideration as well though.. does it?
 

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Here's the transfer function magnitude graph I came up with at 4cuft tuned to 18hz
http://i.imgur.com/0vxTg.jpg

WinISD suggested 20hz tuning, but the plot looked flatter.. Do you think 18hz would be a better idea? Or even lower?
http://i.imgur.com/iAbjd.jpg

My next concern is the cone excursion.. I hadn't ever considered this before, since I'm new to this, but is this a concern?
http://i.imgur.com/nzW4i.jpg
I've read about people modifying the bash plate amps to cut off the low frequency at a certain point.. Is this hard to do?

And then my port speed. I'd like to not have to use super long ports, so I plugged in a 3" x 9.66" port spec which gives a maximum port air velocity of 69m/s at 17.4hz. Is that alright?
http://i.imgur.com/VDNj3.jpg
when deciding on a alignment there are more things to consider than SPLs.

tune to 20 or lower? I always consider group delay when choosing tuning combined with SPL graph and port lengths. you have to come up with a compromise between them. but... the larger the box the easier it is to tune low thus keeping the transients and group delay low. so box size is also part of the consideration.

Cone excursion is the big factor with a BR box, pay attention to it!
The bash 300 has a built in High-pass filter at ~18Hz. in the EQ/filter tab in WinISD add a high-pass at 18hz, order=2.

Port velocity: a 3" port core limit is 15 m/s faster than that it stops working as a port.

later,
rev.
 

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.

EDIT:
Just took into consideration the volume of the plate amp, the manual says it's 6x9.875x3.5", or 207.375cuin or .12cuft. So technically I suppose my box would physically be 4.68cuft with 4.56cuft of volume.
I think winISD takes into consideration the volume of the driver since I entered all it's dimensions in its profile.
I'm not sure if it takes the port volume into consideration as well though.. does it?
WinISD does not consider (adjust volume) anything when recommending Bv you have to do that yourself, I recommend 'Boxnotes' its free. http://www.subwoofer-builder.com/freesoft.htm
 

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Discussion Starter #19
when deciding on a alignment there are more things to consider than SPLs.

tune to 20 or lower? I always consider group delay when choosing tuning combined with SPL graph and port lengths. you have to come up with a compromise between them. but... the larger the box the easier it is to tune low thus keeping the transients and group delay low. so box size is also part of the consideration.

Cone excursion is the big factor with a BR box, pay attention to it!
The bash 300 has a built in High-pass filter at ~18Hz. in the EQ/filter tab in WinISD add a high-pass at 18hz, order=2.

Port velocity: a 3" port core limit is 15 m/s faster than that it stops working as a port.

later,
rev.
Okay, good to know about the built in high pass filter, I added that in, and cone excursion looks all safe now that's good.

As for the port velocity, obviously a 3" port is not going to work for me in this application then, and I think my best bet is going to be a slot port.. I'm looking at building one up the back side of the cabinet which would have dimensions of 1.5" in height, and then 15" wide (width of cabinet), and then the length of the cabinet which is 36". That appears to give me a tuning of 18.5Hz at a volume of 4.46cuft and a port velocity of 14.5 m/s at 300w.

I'm going with 4.46cuft volume now because I am deducting the volume of the driver and plate amp, both right around .12cuft each.

Here's a really quick paint side profile I did.
http://i.imgur.com/DP7KZ.jpg
 

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Discussion Starter #20
tune to 20 or lower? I always consider group delay when choosing tuning combined with SPL graph and port lengths. you have to come up with a compromise between them. but... the larger the box the easier it is to tune low thus keeping the transients and group delay low. so box size is also part of the consideration.
Looking into these other factors you've mentioned.. My group delay was pretty high at lower frequencies.. SO I took another stab at cabinet volume with a few adjustments.

If I stay with the same volume (4.68cuft not including the port section at the back - refer to drawing in previous post) and subtract .12cuft for driver, and .12 for plate amp, I get 4.44cuft.
For my port I have to use a slot port with the dimensions of 1.11"x15"x36" to tune it to 16Hz.
Tuned to 16Hz my group delay is not quite so bad.

Here are the graphs based on these specs:
Transfer function magnitude (f3 of 28.79hz): http://i.imgur.com/CcerN.jpg
Cone excursion (with 18hz hpf eq. Peaks at 15.24mm): http://i.imgur.com/yIiiX.jpg
Port air velocity (peaks at 15.3m/s @ 15hz): http://i.imgur.com/4jQKk.jpg
Group delay (13.8ms @ 30hz): http://i.imgur.com/LznVx.jpg
Group delay (30ms @ 20hz): http://i.imgur.com/qZAm5.jpg

Am I missing any important factors with this design?
Is the port air velocity alright given that the slot port is only 1.11" high (and 15" wide)?
 
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