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-   -   Is this realistic? (http://www.diyaudio.com/forums/subwoofers/68940-realistic.html)

troyhenson 1st December 2005 04:21 PM

Is this realistic?
 
Hi. I've been poking around the forum for a while and haven't been able to find anything based on this driver. It's the 10" Dayton Titanic 280C-4. I want to build a small sub that will have decent extension (who doesn't) and the graphs I'm getting out of WinISD seem almost too good to be true.

Here's a link to the driver: http://www.partsexpress.com/pe/pshow...number=295-414

And here's one to the Dumax report: http://www.partsexpress.com/pdf/295-414dumax.pdf

If I put this in a sealed box (just 16.5 liters in size) I get a Qtc of 0.645. At this point the graph doesn't look that great, but this will only be used for a sub, so I put in a lowpass filter at 80 Hz (Butterworth, n=2).

It will also be driven by a plate amplifier. The 120 W amplifier from Parts Express (URL here: http://www.partsexpress.com/pe/showd...number=300-792 ) actually puts out 156 W into 4 ohms. This will keep the driver from exceding Xmax. This amplifier has a built-in 6db boost at 30 hz (Q=2.0)

With this I get pretty flat response that is 103 dB over the range I will use it (below 80 Hz) and is down 3dB at 27 hz. I realize that is not earth shaking low, but it seems very good (almost too good) for a sealed sub in a very small 16.5 liter enclosure.

Questions: Is this reasonable? If not, what am I missing? Are the specs correct? Any advice would be appreciated.

-Troy

damo21 1st December 2005 05:18 PM

Unfortunately, I can't get hold of one of those here unless I get it sent via UPS, which sux, I'd have to pay shipping plus customs/duty... wouldn't be worth it. Perhaps you could buy 2 and send me one via USPS :P

troyhenson 1st December 2005 08:15 PM

2 Attachment(s)
I'll try to post the WinISD results I'm getting.

-Troy

troyhenson 1st December 2005 08:35 PM

Are there other dirvers that would give similar results (for perhaps a lower cost) in as small an enclosure? One of the advantages of having such a small enclosure is that I can get away with (eventually) having two of them to even out the room's response. For this project I'm uninterested in enclosures that get near 30 liters (1+ ft^3). Thanks in advance.

-Troy

BassAwdyO 2nd December 2005 10:12 PM

It shouldnt be too far off... 18.7mm of xmax on a 10" driver should get you a decent amount of extension and SPL

troyhenson 3rd December 2005 12:01 PM

Thank you for the sanity check. Parts Express has this driver in a kit with a 1 cubic foot volume. They claim slightly higher SPL (105 dB vs 103) using a more powerful amp (250W instead of 150) and say extension is about the same (theirs is 30 Hz vs WinISD's 27 Hz, and I don't think I could tell the difference between these). The volume WinISD gives me is only 16.5 liters, which is about a 10" cube (internal volume) or about 0.58 cubic feet. This is close to just half the volume of the kit from Parts Express. Qts for the smaller box is still below .707, so theoretically it should not sound boomy.

My questions are these:
1. Why am I getting such good numbers out of WinISD?
-- Is Parts Express just underselling their 10" Titanic kit so they don't cut into the sales of the 12" kit?
-- Is the EQ & lowpass added in WinISD making up the difference?
2. If it is the EQ & lowpass filters, what has been everyone else's experience with these?
-- If they color the sound, how do they color it?
3. How does the Parts Express kit avoid exceeding Xmax with the 250W amplifier?

I'm seriously considering building this sub so any pre-purchase advice would be helpful. Thanks in advance,

-Troy

BassAwdyO 3rd December 2005 10:22 PM

Quote:

-- Is the EQ & lowpass added in WinISD making up the difference?
I dont know that the lowpass is doing much for you, but a bit of eq can make a big difference


Quote:

If they color the sound, how do they color it
Depending on the Q of the boost it might just give more boom at 30hz or it could add gain to anything within an octave of the center frequency. How it will effect the SQ will depend alot on the Q of the boost.


Quote:

How does the Parts Express kit avoid exceeding Xmax with the 250W amplifier?
Set the gain lower, or use a rumble filter

Rademakers 3rd December 2005 10:47 PM

Quote:

If it is the EQ & lowpass filters, what has been everyone else's experience with these?
In my expierence a system with a lowcut has an higher output and/or powerhandling, for both the speaker and amplifier. This can matter if you're driving the system near the continues max for longer periods of time, while playing low frequency material or sources. Filters do add group delay.

Wkr Johan

BassAwdyO 4th December 2005 01:15 AM

LowCut = Highpass

HighCut = Lowpass


Lets get it straight what we're talking about here

Rademakers 4th December 2005 08:15 AM

Good point, I'm getting sloppy.

With a lowpass you can move the f3 (relatively) downward. This is because a lowpass does lower f0 in most cases, while it doesn't effect the f3. So 3 dB down from the "new" lower f0 is lower as the original f3 was.

This aside however, I wouldn't totally trust on the predictions you'll get from WinISD. It's a good program for rough calcculations but for precise calculations you need programs that use parameters you didn't know excisted (I just know that I don't know).

Even the most expensive programming out there won't give results that totally merges with reality.

So if they haven't measured their (stated) response I wouldn't trust them either. But perhaps it's just in my nature not to trust the marketing department :clown:

Wkr Johan


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