Multiple-Small-Subs vs A-Few-Large-Subs - diyAudio
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Old 2nd August 2012, 05:07 AM   #1
Eskae is offline Eskae  United States
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Default Multiple-Small-Subs vs A-Few-Large-Subs

I'm trying to learn more about how low end frequencies are produced, and one of first things I want to know is..

For exceptional low end frequency response at high SPL, does it make sense to use a large sub (A Danley TH221 for example) or can you get the same output/response by simply coupling a number of smaller subs?

Are certain types of low frequencies only preducable by very large subs or is it always possible to combine mutiple smaller subs to get the kind of SPL and Frequency response desired?

I've also heard that exceptionally low frequencies needs an exceptionally long horn path in order for the low frequencies to develop and this is because of the pressure that is maintained. Can this same kind of pressure be produced by simply using many subs with short horn paths, instead of one sub with a very long horn path?

Also if a longer horn path is better for low frequencies response is it possible to take a folded horn and build a longer horn onto it to increase the horn length?

Sorry if my questions are dumb, hopefully some people here can improve my knowledge.
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Old 2nd August 2012, 11:07 AM   #2
MaVo is offline MaVo  Germany
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You overthink the problem. Some of it is actually really easy. I did the same thing when i was new to audio.

When evaluating a subwoofer: You look for the frequency response, which should be about flat to the lowest frequency you want to hear. Then you look at the maximum output in dB, which should be enough for your application type and additionally things like power handling or subwoofer size. Then it boils down to knowing what you need in terms of low frequency corner and maximum sound level.

Check the danley subs for what i mentioned. You will for example see the TH115 having less low frequency response than the DTS20, while the DTS20 has less maximum output. This will tell you that you would rather use the TH 115 in a pro audio setting, where sound level is the most important thing, while the DTS20 is best fitted for home theater, which doesnt need as much sound level, but values low frequency response more. The TH221 for example is more of a gimmick subwoofer, made for people who want to have ONE sub do it all for a big audience. You can achieve the same thing with several smaller ones.

Several smaller subs have a flatter frequency response compared to one large sub in domestic settings due to room modes. This doesnt apply in big rooms like cinemas. Read Floyd Toole's book for this matter.
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Old 2nd August 2012, 01:21 PM   #3
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Definitely go with the Danley TH221....
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Old 2nd August 2012, 01:35 PM   #4
Eskae is offline Eskae  United States
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So if I wanted to reproduce the deepness and loudness of a Danley TH221 I could easily do this with mutiple smaller subs right?

I'm trying to figure out then why my buddy bought two Danley TH221 for his small mobile sound business. They are so large he can't move them by himself, and he doesn't own a vehicle large enough to fit them. Typically he doesn't even get paid enough to hire help or rent a truck so it seemed like a pretty dumb move.
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Old 2nd August 2012, 02:40 PM   #5
tb46 is offline tb46  United States
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Hi Eskae,

One of the best ways to gain the knowledge you are seeking is to evaluate the situtations you are pondering in programs like Hornesp or AkAbak. You can then define your questions more clearly. Hornresp should not pose too much of a learning curve, one good starting point is this thread: Simple Tapped Horn Tutorial using Hornresp .

As to the multiple sub question, generally you are looking at air volume displaced by the transducer(s); also, for home use: Multiple Small Subs - Geddes Approach

Regards,
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Old 4th August 2012, 10:45 AM   #6
Rojoh is offline Rojoh  Norway
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Quote:
Originally Posted by Eskae View Post

I'm trying to figure out then why my buddy bought two Danley TH221 for his small mobile sound business. They are so large he can't move them by himself, and he doesn't own a vehicle large enough to fit them. Typically he doesn't even get paid enough to hire help or rent a truck so it seemed like a pretty dumb move.
Yes, subs like TH221 would be perfect for permanent installs, but must be a pain to move in and out of different venues.
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Old 4th August 2012, 04:20 PM   #7
18Hurts is offline 18Hurts  United States
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Live Sound: Optimizing The Low End: Run & Gun Subwoofer Arraying Techniques - Pro Sound Web

Here is information concerning that topic when used as a PA system...
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Old 5th August 2012, 04:47 AM   #8
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Like a lot of things, depends on your goals. Keeping just in sound aspects (as opposed to space, looks, cost...), having a lot of drivers can produce wonderful clean, sharp sound. But for impressive low and large bass, you tend to need large drivers and well-conceived boxes.

There is no way to have great sound in a room without at least two subs in heterogeneous locations to average-out room location influences.

Ben
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Old 18th August 2012, 03:58 AM   #9
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It really depends on what your trying to accomplish. I've had multiple smaller drivers and multiple larger drivers. I will say this and it holds true in my opinion...there's no replacement for cubic displacment...meaning the larger woofer is usually the all round better choice.

I've had multiple smaller woofers hit higher SPL than 2 larger woofers, but the larger woofers sounded way louder and deeper, they seemed to move more air also. If your wanting to rock the house...the larger is the way to go. If your looking for cleaner punchy bass the smaller ones are better.
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Old 18th August 2012, 05:02 AM   #10
Djim is offline Djim  Netherlands
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Hi Eskae,

The extra low frequency extension and displacement for 21” in PA can be achieved with multiple 18” drivers. Usually multiple drivers are more expensive and need more wood. The advantage of multiple smaller 18”units is more motor power and more headroom ‘upstairs’, besides being more transport friendly.

For your second question, horns can be used with separate extensions to lower the low limit at cost of headroom.
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