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Dual Ported Dayton Audio RSS390HO-4 Reference 15 Build for HT - Page 2

post #31 of 38
Thread Starter 
Quote:
Originally Posted by Martycool007 View Post

Braveheart, have you been able to fix the lack of mid-bass issues? If so, what was the key to fixing this
issue? How do you like having two of the Dayton HO15's now instead of just one?

That's the FR till 150Hz (sub+mains), which is a lot better uptill 115Hz without any EQ. However, there are 3 suckouts at 115Hz, 120Hz, and 125Hz (encircled), which I think I can fix by pulling the mains further out towards the LP and increase distance from the rear wall. I haven't got the time to do it yet.



Co-location gave me better midbass response as opposed to each sub on opposing walls. I could easily dig down to 11Hz that way, but I had huge suckout from 100Hz to 110Hz. Co-locating removed that null and pushed it further up in the response.


As far as listening is concerned I guess a lot has been said by a lot of DIYers in terms of sound definition. I would simply say the duals just drop the jaw, I threw anything and everthing at them at -10dB (Reference Scale) on AVR master volume. Following movies were tested;

Casino Royal (First 20 mins)
Knowing (Plane Crash, Train Wreck, and the final ending)
FOTP (Plane Crash)
Master and Commander (First 20 minutes)
Shooter (Hut explosion scene at the end)
Pearl Harbour (Japs attack)
WOTW (Pod emerging scene)
Skyfall (Last 25 minutes)
The Town (Last 20 minutes)

The subsonic response is hugely tactile. The duals can easily pressurise the rib cage, twist the gutts inside, easily flap the pants, and send a shockwave down the spine effortlessly. The feeling is similar to how you feel water hitting you from all sides during floating, if you know what I mean. It seems as if one is floating in bass. Also, the chest slam area (30-40Hz) hits you like a nuke. Midbass (100-150Hz) though a tad weaker in the current arrangement but it is a lot better than before.

Overall, just one word.................FANTASTIC

Couple of more things here .............Daytons are amazingly clean subs in terms of response. Also, the box resonance is virtually zero. On the other hand you can safely call Def Tech SC Ref a resonator more than a subwoofer coz all you hear from SC Ref is box resonance and that is it.

Note: As opposed to the intial plan of 850 watts, um feeding 1100 watts per sub, which pushes the cones to 19mm without deteriorating the response. And the drivers are still in the break in period. That means these babies can really take brutal pounding and the published Xmax is extremely conservative.
Edited by braveheart123 - 5/11/13 at 9:57am
post #32 of 38
Thread Starter 
Now over to my question regarding cables in post # 27, can anyone pls help me on the issue?
post #33 of 38
Both cable options should give the same result.
post #34 of 38
Quote:
Originally Posted by braveheart123 View Post

That's very simple. Let's say you have a suckout at 60Hz, the formula to calculate 1/4 wavelength reflection off the rear wall is as follows;

1/4(speed of sound/frequency) = 1/4 (345/60) = 1/4(5.75) = 1.4 meters = 1.4 x 3.28 = 4.59 feet

So, 4.59 feet should be the minimum distance of driver from the rear wall in order to avoid a 60Hz suckout.

Note: Speed of sound is temperature dependant.


Thanks for the reply, Braveheart123! I am a little confused by this formula. How did you get the number 345 in the first equation? Is that a constant, as in, always there?
Also, how did you get the number 3.28 in the forth equation? Is that a constant as well? I understand the math part of this just fine, I am just confused as to where you
got those numbers that I asked about. I appreciate you taking the time to explain this to me!
post #35 of 38
speed of sound is 343 meters/sec or 1126 feet/sec. So 1/4*[(1126 ft/s) / (60 1/sec)] = 1/4*(18.77) = 4,7 ft
(about the same as what braveheart said)

The 3.28 is just a conversion factor for meters to feet. 1 meter = 3.28 ft

It always helps me to include units in the formulas smile.gif
post #36 of 38
Thread Starter 
Quote:
Originally Posted by Martycool007 View Post

Thanks for the reply, Braveheart123! I am a little confused by this formula. How did you get the number 345 in the first equation? Is that a constant, as in, always there?
Also, how did you get the number 3.28 in the forth equation? Is that a constant as well? I understand the math part of this just fine, I am just confused as to where you
got those numbers that I asked about. I appreciate you taking the time to explain this to me!

Formula to calculate Wavelength = Speed of Sound / Frequency under consideration

Just multiply the result with 1/4 or 0.25 to get the quarter wavelength of the subjected frequency. Since, I took the speed of sound in meters, I simply multiplied 3.28 with the result to convert it into feet.......1 Meter = 3.28 Feet.
Edited by braveheart123 - 5/13/13 at 11:01am
post #37 of 38
post #38 of 38
Quote:
Originally Posted by LTD02 View Post

here is a good read on the topic marty: http://www.peavey.com/support/technotes/soundsystems/boundarycancellation.cfm
Except some of it is incorrect. For instance:
Quote:
Here is an example of conditions where the kick drum can be diminished due to boundary cancellation. Lets assume that a typical stage is 3 1/2 ft. high (42 in. or 1.07 m), and the subs are placed on the corners of the stage. If we divide the speed of sound by a given frequency, we get the wavelength or physical size of that wave form in air. In most warm rooms, the speed of sound is 1130 ft. per second (344.5 m).80 / 1130 = 14.125 ft. (4.3 m)One-fourth of this dimension is 3.53 ft or 42.4 in. (1.08 m)Guess what? This height stage is canceling half the energy of the kick drum frequency.
That scenario is only correct if the listeners position is on a direct line between the floor and the speaker, ie., directly above the speaker. Where the audience is concerned what matters is the difference between the position of the sub and the point on the floor at which the wave reflects to them. The further away they are from the sub the less that difference is, progressively raising the floor bounce cancellation frequency out of the subwoofer band width. One can even use this to one's advantage, cancelling out too much content close to the speaker where you don't want it, leaving it unaffected further out. It also can work to great disadvantage. Every bass player is familiar with their bass struggling to get enough volume on stage, especially if there's a low ceiling causing cancellation close to the amp. But in the back of the room where that cancellation mode isn't present the bass can be knocking glasses off tables. This very phenomena gave rise to the myth of wave propagation, where it was assumed that one had to be a certain portion of a wavelength away from the source to hear it. Proponents of that theory didn't have an answer when asked how car stereos, let alone headphones, could be heard in the lows.
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