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Old 17th July 2011, 08:33 AM   #1
Billyo is offline Billyo  Australia
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Default Interchanging components with this design

Hi all,

In order to boost the WAF, I've been looking seriously at building this sub Sonic MK2

that looks like a little sidetable.

I've got the full (english) specifications from Monacor, which uses a 38cm/15 inch subwoofer

Subwoofer mit SPH-380/2-BR

and a 200/250W plate amp (SAM-2)

Amplifier Modules by Monacor



But frankly, I'd rather use a comparable amp and similar sized driver from parts-express or sourced locally. I know that for hifi speakers, the crossover and cabinet construction is precisely matched to the drivers - but for subs, do the same rules apply?


If I chose a sub of the same diameter and similar specs, with a plate amp of the same power and used it in that cabinet instead of the Monacor components, would it basically perform the same?

Thanks all
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Old 19th July 2011, 08:05 PM   #2
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Quote:
Originally Posted by Billyo View Post

But frankly, I'd rather use a comparable amp and similar sized driver from parts-express or sourced locally. I know that for hifi speakers, the crossover and cabinet construction is precisely matched to the drivers - but for subs, do the same rules apply?


If I chose a sub of the same diameter and similar specs, with a plate amp of the same power and used it in that cabinet instead of the Monacor components, would it basically perform the same?

Thanks all
Yes, basically the same as any two cars with similar specs will "perform the same".

I have not compared the amps or speakers you mention, but I have found amps and speakers with similar specifications often perform quite differently.

Usually differences are most apparent when "pushing the envelope", if you pick a sub that won't exceed Xmax at the level you want to listen at, and an amp that will deliver that amount of music power, the difference won't be much.
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Old 19th July 2011, 11:01 PM   #3
Billyo is offline Billyo  Australia
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Thats good news! Thankyou


Compared to multiway speakers, I can barely find any subwoofer designs on the web...

would this mean that subwoofer design is mostly a matter of driver diameter, matching the cabinet volume to the size of the driver and then picking an amp with enough power to operate it? Ergo, most subs are just boxes of a particular volume.

Do points that are crucual for multiway - such as cabinet architecture, the crossover and the driver quality - not matter so much?
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Old 19th July 2011, 11:13 PM   #4
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It's not that simple...

construction really matters, if done on the cheap you'll hear the box more than the driver. The crossover order and frequency and time alignment and the relevant delay parameters all come into play. driver quality... yea it matters a lot, more than midrange or lowmids.
With the energies involved, comparatively huge compared to a midrange box, design matters. 80-90% of the total acoustic energy in a three or four-way system comes from the sub.
good luck.

Last edited by revboden; 19th July 2011 at 11:21 PM.
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Old 19th July 2011, 11:33 PM   #5
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A reasonably well executed sub, one with decent specs and used within its capabilities will be affected more by the room it's in than most other factors. The most common problem is room mode excitation, especially when only a single sub is used. Next is integration with existing satellites. Getting it right usually involves moving things around and adjusting relative output levels. As for the the design of the sub, it's esier to get it right using a lower "Q" driver with a reasonably low Fs - somewhere around 30 to 40 Hz in a sealed cabinet that's not too small, check out programs like WinISD to get started.

LinearTeam

And avoid the temptation to reach way down low with your design, in most average size rooms, you'll have "room gain" that helps out starting around 40hz and below. I'd say go for it, and let us know how it works out.

Mike
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Old 19th July 2011, 11:46 PM   #6
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Quote:
Originally Posted by Billyo View Post
Compared to multiway speakers, I can barely find any subwoofer designs on the web...

would this mean that subwoofer design is mostly a matter of driver diameter, matching the cabinet volume to the size of the driver and then picking an amp with enough power to operate it? Ergo, most subs are just boxes of a particular volume.

Do points that are crucual for multiway - such as cabinet architecture, the crossover and the driver quality - not matter so much?
You must not be looking very hard .

Cabinet shape, bracing, material, crossover type, driver quality, phase response, and dozens of other tidbits all are important in sub design.
That said, our hearing is more critical in the so called “speech range”, the 400 to 4000 Hz decade than the sub range.

There are hundreds (if not thousands) of different sub designs on this site alone, falling in to around a half dozen or more distinct categories, with combinations of those making for dozens of other variants.

Sealed (Infinite Baffle, acoustic suspension)
Bass reflex (BR)
Fourth or Sixth order Band Pass (BP4, BP6)
Tapped Horn (TH)
Tuned Quarter Wave Pipe (TQWP)
Transmission Line (TL)
Horn (Front Loaded Horn, folded or straight, offset, etc.)

All the above can use plenums, push pull or isobaric variants.

And change the drivers in any of the above, and response characteristics also change.

Have fun !
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Old 20th July 2011, 12:34 AM   #7
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Default danger! danger!

Ya got me thinking. Once you hear a properly tuned, integrated, custom made DIY subwoofer, You will look at store bought subs and think 'what a pointless waste of money'. Once you start down this road... You'll have to listen to all your music again just to hear what you've missed.

Don't say I didn't warn you...
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Old 20th July 2011, 02:03 AM   #8
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Revbden, the most important thing for a subwoofer box other than physical dimensions being right for the chosen type and alignment is strength. There is usually little box resonance to worry about if it's strong enough to resist excessive panel flexing, the wave lengths involved are over 10ft for frequecies 100Hz and below, so no internal resonance. Also human hearing is not nearly as sensitive for distortion and frequency response where subs do thier thing. Subwoofers are generally much easier to get right than satellites.

Mike
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Old 20th July 2011, 11:36 AM   #9
Billyo is offline Billyo  Australia
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Wow - this is a different world from hifi multiways! Thxs for opening my eyes :-)


So I've just spent an hour or so on this site, reading about sealed enclosures The Subwoofer DIY Page v1.1 - Sealed Systems

I plugged in the spec for a Dayton sub Dayton Audio RSS315HF-4 12" Reference HF Subwoofer 4 Ohm High Fidelity Reference Series into the spreadsheet that Brian kindly provided http://www.diysubwoofers.org/design/ported.zip

One of the parameters that can be chosen is the volume of the enclosure... which begs the question of which of the output characteristics are the most important in terms of optimising the system (Alpha, Fb, etc)

Can someone point me towards a resource that explains how to optimse these variables? Can I just skip straight to the frequency response chart to get the "bottom line" on the system performance without needing to concern myself with the more esoteric parameters?
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Old 20th July 2011, 08:51 PM   #10
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Quote:
Originally Posted by Michael Bean View Post
Revbden, the most important thing for a subwoofer box other than physical dimensions being right for the chosen type and alignment is strength. There is usually little box resonance to worry about if it's strong enough to resist excessive panel flexing, the wave lengths involved are over 10ft for frequecies 100Hz and below, so no internal resonance. Also human hearing is not nearly as sensitive for distortion and frequency response where subs do thier thing. Subwoofers are generally much easier to get right than satellites.

Mike
well...yeah

but you don't have to send subwoofers into space.

edit: satellites are easy as long as you keep the drivers separate with their own amp and eq . don't get me started on people who try to put everything in one box and run it off one amp (unnecessary complexity) ...

Last edited by revboden; 20th July 2011 at 09:13 PM.
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