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Old 15th September 2005, 06:40 AM   #1
diyAudio Member
 
Join Date: Sep 2005
Default Starting with my first sub

I have descided that my first speaker project will be a sub. However, there seems to be so many factors to consider that I will try to expand my plan piece by piece. I have a ton of questions, so please bear with me.

1. I am trying to descide on a woofer, but since my knowledge is so minimal I do not know if the information I need is on the manufacturers web sites or not. You need to know the recomended box size, has the unit Vas anything to do with it?

2. As I will do a Constrained layer damping (CLD) box, I guess a plate amplifier will be hard to use, then their depths would penetrate both boxes? External amps is it for CLDs?

3. What are the benefits/drawbacks with a side firing vs. a bottom firing sub?

4. As its inteded use is in a SMALL home "studio", when do you need to shield the woofer, are there safe distances? I am very likely to set it up quite close to my CRT.

5. What do one need in terms of equipment, software and hardware?
I am a Mac guy, so software, if there are any, should be geared to that platform, preferably for OS X. I have found these software examples, I do not know if they are of any use:

-AudioTest 1.6
-Tone Generator www.nch.com.au
-Fuzzmeasure
-MacSpeakerz (only OS 9???)
-Mac the Scope
- Charlie Wright has created a MAC*version of a spreadsheet for calculating sealed systems, called MACSEAL.HQX

Is there more out there?

As for hardware, except for wood working tools etc, what do you need?

6. As I will have plenty of time before I actually start the practical phase, I was wondering if anybody has a view on any of these two books, from a beginners perspective:
-Loudspeaker Design Cookbook -- by Vance Dickason
-Speaker Building 201 -- by Ray Alden

Many claims that the Dickason book is so good, but that it often quits before reaching the end of the problem. The Alden book is a suposedly much better version of his earlier book. If I, as a beginner should choose one, which one?

Many thanks,
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Old 19th September 2005, 09:04 PM   #2
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Join Date: Sep 2005
Yes, I can see that my questions rendered very little interest, but to get me started, I would very much appreciate any input on questions 3-5.


3. What are the benefits/drawbacks with a side firing vs. a bottom firing sub?

4. As its inteded use is in a SMALL home "studio", when do you need to shield the woofer, are there safe distances? I am very likely to set it up quite close to my CRT.

5. What do one need in terms of equipment, software and hardware?
I am a Mac guy, so software, if there are any, should be geared to that platform, preferably for OS X.
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Old 19th September 2005, 10:25 PM   #3
simon5 is offline simon5  Canada
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Join Date: Nov 2004
Location: Québec, Québec
1. Smaller Vas = smaller box size but there's several parameters that will affect the box size. Vas is only one of them. It will also depend on how low you want to go.

2. If you're going with CLD, yes I guess you should use an external amplifier like a Pro amplifier or something.

3. Bottom firing : Some subwoofers are designed to play this way, they have slightly more excursion when in downfiring mode. You can also make a subwoofer that looks like a furniture piece. The main disadvantage is if you plan to use your subwoofer for 10-20+ years, you will probably need a new driver because the suspension will weaken over time.

Side firing : Suspension will weaken less overtime. Most subwoofers are made for side firing operation. You'll see the woofer so that's an advantage or disadvantage depending on you. It's better if you plan to crossover your subwoofer really high.

4. You can't put your subwoofer on the floor? Safe distance, it depends on the subwoofer driver and on the specific CRT. Maybe a foot, rough guess. You'll see when you're too close, your screen will distort and need to use degauss often. Yes you could shield it too with shielding material.

5. I'm not a Mac guy, but since you can run PC things on OSX, you could try WinISD Pro and Unibox. You don't need much things besides wood working tools (?). If you go ported you'll need a PVC pipe, might want to get some rubber feet, wood glue, wood clamps, weatherstripping tape that glue on both sides to seal the driver but that you can remove if there's a problem, thick copper wire, paint, if you go sealed you'll want to use polyfill...

6. I've heard good things about the Dickason book, dunno about the other one, can't help you on that one.

If you need more information, please reply.
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Old 19th September 2005, 10:48 PM   #4
Raoul is offline Raoul  United States
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Join Date: Feb 2003
Location: OR
3. First things first. Here is a link to determine whether a sub can be oriented in a downfiring position:

http://www.adireaudio.com/Files/Tech...rientation.pdf

By orienting a sub downward, you are limited to space it is firing into, which can provide a bit of additional effective output. Adire had a pretty good paper on this as well, but it seems to have vanished into the ether. You might want to check their tech papers, as they may provide some answers to some of your questions. The link is:

http://adireaudio.com/TechInfo.htm

Also, some of their old papers can be found here:

http://www.adireaudio.com/Files/

4. Depends somewhat on the woofer. I gaussed my television (by accident) with my Brahma 12 from a good seven to eight feet away. However, the sub now sits only a few feet (maybe four) from the television, tilting at an axis to the CRT. If you plan on sticking the sub right next to the CRT, you may want to consider shielded. Maybe someone else has some experience with this...

5. Can't help you there.

Hope this helps.

edit: Looks like simon5 beat me to the post If you search the forum for CLD, you should find at least a few threads discussing there applications in loudspeakers and subs.

The Dickason book is a good place to start. You can probably find an older edition for a reasonable price.
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Old 20th September 2005, 07:23 AM   #5
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Join Date: Jul 2005
Location: U.A.E
Hi Buqqsson,
My 2 cents on your questions.

4. Even so-called shielded speakers do show up with colour patches on the CRT. I moved a spare speaker around, till the patch disappeared and then hid it with a portrait in front. Shielded speakers are costlier since they use another magnet to cancel the effect of the main one. I suppose you'll have to use mains speakers in addition to the sub in future, so these could also affect the CRT. Safest way is to keep the speaker as far away as you can, without any colour patches appearing on the screen.

6. Dickason's book is good enough for a speaker builder.

Goodluck with your foray.
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Old 20th September 2005, 08:34 AM   #6
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I think vance dickason's book is much more comprehensive than speaker building 201, but i would recommend that you get both if possible (but the dickason one if you can only get one), i found the speaker building 201 explained some concepts more clearly for a novice than the dickason book.
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