Triple driver - sealed. Pros/cons, and is it too much for a newbie

[turbodawg]

Originally Posted by MedPed

I was doing some measuring...
I can likely manage a pair of 27"x27"x27" sealed cabinets. That is about 11.3 cu.ft. external volume, and likely closer to 10 cu.ft. internally after bracing and driver displacement.

How would a sealed cab that size measure out with the Dayton Audio RSS460HO-4 18" Reference HO Subwoofer 4 ohm. Specs:
Power handling: 900 watts RMS/1,800 watts max • VCdia: 3" • Le: 2.10 • Impedance: 4 ohms • Re: 3.41 ohms • Frequency range: 20-500 Hz • Fs: 19.6 Hz • Sensitivity: 89.2 dB 1W/1m • Vas: 10.52 cu. ft. • Qms: 3.90 • Qes: 0.43 • Qts: 0.39 • Xmax: 12.75 mm • Dimensions: Overall diameter: 18.17", Cutout diameter: 16.69", Depth: 8.94"
http://www.daytonaudio.com/media/res...ec%20Sheet.pdf

Thanks Oliver, for your link to the post by mRgSr: New HT subwoofer. Dayton Ref 18".
He just finished his, and I would love to hear his results/measurements. His internal volume was about 8 cu.ft. Loved the cabinet.

If the consensus is that it might measure well, and he is happy with his, this might well be worth a shot.

Any thoughts?

Two of these drivers =$500. inuke6000DSP 450+tax. Throw in the cabinet costs, I am pushing probably close to $1200-1300. But for two 18" subs, I think it is safe to say, I will likely not be able to pick up anything retail for under $2000 that outperforms this pair, correct? Please agree with me.... please?

What other amp/dsp options should I be considering. I know there is probably a good used market out there, but due to my ignorance in the matter, I probably will not have clue what I am buying, and should likely stick to retail for something that you guys recommend. Also, it is worth getting the DSP amp, or separate amp and dsp units, eg. minidsp.

If you can do 10 cubes each, you might want to model up some ported designs and see where that gets you. It also might allow you to step down to a nu3000dsp - more efficent, less mechanical power handling. With a low tune and properly designed ports, they will sound just as good as a sealed sub with EQ.

[Moonfly]

Originally Posted by MedPed

175 litres are certainly more desirable than 270 for spouse acceptance factor!!
On review of the specs, it does seem that the Fi is more sensitive and with a lighter Mms than the Dayton. Wouldn't know if they are equally stiff.
The Qts is little lower on the Dayton.
The resonant frequency is pretty high on the Fi with a Fs 32.1 vs 19.6 on the Dayton.

I am trying to make sense of these numbers - so I don't over think it, what might these numbers mean to me and for cabinet construction and sound.

Fs is one of things that goes against the driver a bit, but dont be fooled into thinking that a drivers Fs is a brick wall, they can and do play well below Fs with the right cab and proper eq. The suspension on them is a little stiffer than some other drivers, but it helps give the driver some good control and with that big motor on there it still goes plenty low. The Dayton is a good driver, but you only have to compare the Vd of the two drivers to see the difference between the two in how much air they can shift, and the ability to shift air is important if you want to go low. FWIW, I only use xmax figures as well, not xmech, so the spl output figures I quoted earlier are with the driver using full power in a cab designed to ensure the driver never exceeds xmax with that rated amount of power. That helps keep the system clean.

[Moonfly]

Originally Posted by turbodawg

If you can do 10 cubes each, you might want to model up some ported designs and see where that gets you. It also might allow you to step down to a nu3000dsp - more efficent, less mechanical power handling. With a low tune and properly designed ports, they will sound just as good as a sealed sub with EQ.

Dont forget you dont have the same control over system Q with a ported sub, and you cant replicate a true linkwitz crossover with a ported sub either, which is the only way a sub can perfectly be in phase with the speakers (hence why sealed subs are noted to integrate better).

[weltersys]

Originally Posted by Moonfly

Have you ever run a 15hz tone through a sub, and increased output till you can actually hear it measured with a spl meter. I can hear 20hz at fairly high levels, but 15hz and under is pretty nothing audible to me at all.

Yes, I have.
Built a tall isobaricly loaded tapped horn "Totem" sub for my shop, it rolls off below 20 Hz but corner loaded still puts out level clearly audible (around 80 dB) as low as 15 Hz without distorting.
I mostly listen to the radio in the shop, very few songs make the Totem sub come alive, the other 3 higher tuned subs are what generally fill the bill.

Much easier to hear clean low stuff using headphones, it takes a big cabinet or a lot of power to make much output below 20Hz.

[weltersys]

Originally Posted by Moonfly

Dont forget you dont have the same control over system Q with a ported sub, and you cant replicate a true linkwitz crossover with a ported sub either, which is the only way a sub can perfectly be in phase with the speakers (hence why sealed subs are noted to integrate better).

Being "in phase" with the top cabinets is critical at the crossover point.
The phase response of the top cabinets must be determined to match the subs phase response at the acoustic crossover point, a ported top will require a different delay compensation than a sealed top cabinet.

With DSP, proper integration can be achieved with sealed, ported, or horn loaded subs.
All types of subs can integrate well, though certain designs require more DSP to integrate properly.

[Moonfly]

Originally Posted by weltersys

Being "in phase" with the top cabinets is critical at the crossover point.
The phase response of the top cabinets must be determined to match the subs phase response at the acoustic crossover point, a ported top will require a different delay compensation than a sealed top cabinet.

With DSP, proper integration can be achieved with sealed, ported, or horn loaded subs.
All types of subs can integrate well, though certain designs require more DSP to integrate properly.

The speakers do matter, but only in a system where the sub and speakers are sealed and a .707 system Q is used, and both crossover at 80hz and use LRC's will both be perfectly in phase. Any deviation from that and perfection isnt possible. The problem with ported subs is the driver and port each have their own phase, so its impossible to dial both in perfectly. The LRC research stuff shows us this.

[Moonfly]

Originally Posted by weltersys

Yes, I have.
Built a tall isobaricly loaded tapped horn "Totem" sub for my shop, it rolls off below 20 Hz but corner loaded still puts out level clearly audible (around 80 dB) as low as 15 Hz without distorting.
I mostly listen to the radio in the shop, very few songs make the Totem sub come alive, the other 3 higher tuned subs are what generally fill the bill.

Much easier to hear clean low stuff using headphones, it takes a big cabinet or a lot of power to make much output below 20Hz.

Sorry but I'm still not convinced. Besides the fact your chosen weapon is heavily rolling of below 20hz, I wouldnt trust a resonator to deliver a completely pure tone. Try it with a high end sealed sub using a 15hz sine wave at 100db, and I'd be quite surprised if you could still hear that. Maybe you can, maybe you cant, I just find it a bit far fetched. No offence intended, JMO.

[weltersys]

Originally Posted by Moonfly

Sorry but I'm still not convinced. Besides the fact your chosen weapon is heavily rolling of below 20hz, I wouldnt trust a resonator to deliver a completely pure tone. Try it with a high end sealed sub using a 15hz sine wave at 100db, and I'd be quite surprised if you could still hear that. Maybe you can, maybe you cant, I just find it a bit far fetched. No offence intended, JMO.

Moonfly,

Headphones are a "high end sealed sub", it takes far less than 100 dB for me to hear a 15 Hz tone on my Sony MD 7506, or GK Ultraphones, which also use the 7506 element in Peltor muffs.
The revised curves of ISO 226:2003 indicate average persons can hear 16 Hz at 90 dB, I may be above that average, but even if not, 10 dB is an order of magnitude over what an average person needs to hear 15-16 Hz.

I felt ill after listening to a pair of BC18SW115-4 open air playing sine waves at 12-20 Hz during break in, though quite audible, I doubt they were at 100 dB.

Regarding your statement "The problem with ported subs is the driver and port each have their own phase, so its impossible to dial both in perfectly" it does not address the fact that the phase response of of (almost) any two cabinets can be combined, using time delay, to coincide at the crossover point.

There are no real world transducers with flat phase response over their entire frequency range, no "phase perfect" speaker exists without DSP.

To illustrate, the screen shot below has the magnitude and phase response of four tests:
An Acoustic Research sealed 10" (presumably a Q of .707)
A BC18SW115-4 in a bass reflex cabinet
A BC18SW115-4 in a tapped horn
A BC18SW115-4 in a tapped horn with top cabinets using sealed Eminence Alpha 8", crossed over and equalized for flat response.

The last is a giveaway, as only one trace has a flat response, which also equates to a smoother phase response.

Can you identify the crossover point between the TH 18" and the sealed 8"?
Can you identify the other three phase traces?

Have fun, good luck!

Art

[weltersys]

Originally Posted by Moonfly

Besides the fact your chosen weapon is heavily rolling of below 20hz...

The Totem ISOTH sub in a corner had even more extended LF than I remembered, only about 5 dB down at 16 Hz.
Pretty darn good LF for a pair of $5 drivers .

Edit: The RTA 420 mic used for the measurement rolls off in response at least 2 dB at 16 Hz, 16Hz may be the 3 dB down point for the Totem sub.

Art

[Moonfly]

Originally Posted by weltersys

Moonfly,

Headphones are a "high end sealed sub", it takes far less than 100 dB for me to hear a 15 Hz tone on my Sony MD 7506, or GK Ultraphones, which also use the 7506 element in Peltor muffs.
The revised curves of ISO 226:2003 indicate average persons can hear 16 Hz at 90 dB, I may be above that average, but even if not, 10 dB is an order of magnitude over what an average person needs to hear 15-16 Hz.

I have to admit that I can also hear low 15hz tones from my headphones, but I do question why when with a sub I cant untill the level is pretty high.

Regarding your statement "The problem with ported subs is the driver and port each have their own phase, so its impossible to dial both in perfectly" it does not address the fact that the phase response of of (almost) any two cabinets can be combined, using time delay, to coincide at the crossover point.

The LRC is perfectly in phase at the crossover point providing all required parameters are met. The problem with a driver in a ported cabinet is that you have two sources of sound, but they are tied to the same cabinet, you cant separate them to dial them in so to speak. The difference in phase between the driver and port is locked in by the fact they share the same cabinet.

There are no real world transducers with flat phase response over their entire frequency range, no "phase perfect" speaker exists without DSP.

Agreed.

As a guess, I'd guess at the yellow.