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Old 18th October 2012, 04:43 PM   #11
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Quote:
Originally Posted by Cokewithlime View Post
Here are a couple of very important things to consider

1. That TB driver is not all that efficient, with 50W input, a single driver will only get you about 97db @ 30Hz @ 1m - with the three coupled in the enclosure would then get you to about 103db @ 30Hz @ 1m.
So that raises the question, how much room are you trying to fill ?
The boundry gain by putting the sub against a wall will help, so I'd expect higher SPLs than the ones you've mentioned.
WinISD reckons with 3 drivers and 150w (that's 50w per driver - I checked the cone excursion vs one driver and 50w) you'll hit 110dB in half space.
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Old 18th October 2012, 05:14 PM   #12
Doug47 is offline Doug47  United States
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I will try to answer both planet10 and schmeet at the same time. That requires coordination, which I have little...

1. My background is electronics & not audio, so I can see how we might "feel" sound different than what my various boxes "feel' my signals. I don't know how "sensitive" our ears are and how we perceive sound. I've got a lot to learn. In my defense, while researching for this sub, the number folks seemed to focus on was the 3 dB point. The 6 & 10 dB seemed to be listed as an afterthought. Good that I came here for information .

Note, f6 was around 30 Hz, so it's dropping rapidly.

2. The sub will be strictly for the LFE channel and whatever the Audyssey sets it to. Again, my Polks are fine as full range speakers (in fact, one of the complaints I've read about my Polks is they are a bit over the top at the low end). I just want a bit of a boost for the very low end when watching movies (but I don't need Earth shattering).

As for the port speed, I have spec'ed a port with flairs on both ends. I did read about "chuffing" (?) from ports if you get velocities too high. Hopefully, that will help with keeping the air moving in a "nice" way. I also understand to keep the inside of the port tube smooth so as to inhibit turbulence.

I can already see why there are so many different designs for speakers. One would think that by this point, it would be down to a "science" instead of an art.

Although this is my second "from scratch" DIY speaker, I don't see it as my last. This can be a nice hobby to keep me out of trouble once those dang kids quit taking all my money...

Again, thanks for the feedback & information. I am taking notes and thinking about my choices.

I do have a couple of questions about the plots in schmee's post. I see an attenuation dip at ~200 Hz and a spike/diip at ~350. The sub should not be getting signals near 350, but it might get to 200 Hz (I have to look at where the Marantz would cut it off). Is that an "anti-resonance" between the port and the speakers?

And 110dB is more than fine with me. I'm not trying to reproduce a Disaster Area concert...

Last edited by Doug47; 18th October 2012 at 05:31 PM. Reason: Clarify my post and add late breaking information
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Old 18th October 2012, 05:30 PM   #13
bjorno is offline bjorno  Sweden
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Hi, FYI:

b
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Old 18th October 2012, 05:38 PM   #14
Doug47 is offline Doug47  United States
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Quote:
Originally Posted by bjorno View Post
Hi, FYI:

b
You will need to help me with this one. I see you did two different analyses, and found one recommended and one NOT recommended. I am not sure which numbers I need to find. It seems like the "not recommended" version has fewer spikes than the "recommended" version, but the recommended version has better transient response (?). It looks like the recommended version would be good if I can make sure nothing about 200 Hz gets to the sub. That part I can handle. I know how to do that with my amps.

Obviously, you used a MUCH more sophisticated analysis program than what I used (WinSID or something?). That better program is showing things that were not found with my version. I've also not read that I should not use a port with a greater than 3:1 length/diameter.

What I don't see is a box size or port recommendation on either analyses. My guess is they are there, I just don't know where to look (or what to look for).

Help?

And just for funnies, I will be in your (bjorno) neck of the world next week (Helsinki). Yea, I know, different country and all, but I'll be much closer than I am now.

Last edited by Doug47; 18th October 2012 at 05:58 PM. Reason: More clarification
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Old 18th October 2012, 05:57 PM   #15
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by Doug47 View Post
You will need to help me with this one. I see you did two different analyses, and found one recommended and one NOT recommended. I am not sure which numbers I need to find.
The four plots in the right column is IMO a sub I would recommended/ build.

On the right side and down a sub type that you can find mass-produced at bargain prices..i.e like 'F..ting' computer subs probably designed with programs like WinISD or similar. drDyna in this forum have a very good YOU-tube animation link that highlights the expected performance..Sorry I cant find this one.Maybe someone can post the Url?

b

PS: ' It seems like the "not recommended" version has fewer spikes than the "recommended" version, but the recommended version has better transient response (?)'

No, the recommended version will in reality have much smaller spikes as internally damped and a far better transient response that can be seen in HR.

Last edited by bjorno; 18th October 2012 at 06:02 PM.
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Old 18th October 2012, 07:54 PM   #16
Doug47 is offline Doug47  United States
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bjorno, I'm sorry, I still don't understand what you are suggesting. Are you suggesting a box with 12,6 liter volume? A port with volume 3,5 lt? Quoting one of my favorite lines from Hitchhiker's Guide, "Shapes, I need shapes!".
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Old 19th October 2012, 01:28 AM   #17
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Keep in mind that with the aspect ratio you are proposing the box will have at least started to transition to an ML-TL and as such and sims assumming it is a bass-reflex will be off.

I agree with this much
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Old 20th October 2012, 05:57 AM   #18
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Quote:
Originally Posted by Doug47 View Post
THAT could be an issue. Are there any alternatives (same approximate size) that you might recommend? I want the sub to ADD to my enjoyment, not subtract. I will be sitting about 8-10 ft from the sub.
You might want to have a look at the Exodus EX-Anarchy 6.5" driver it's definetly mechanically quieter and also IMHO more musical oriented(lower distortion) than the similar TB drivers.

Also while your at it you might want to really consider an alternative design, say something like building 2 of these proven, tested and measured LilMike designed Tapped Horns Two of then side by side should fit in the space you have available and may have a much higher WAF since they are much lower profile. As to the complexity of construction there are CNC flat packs available for that design - just a thought for you - btw you can use either the TB or the EX-Anarchy in that design.

Quote:
Since none of my sources are analog (DVD-A, Blueray, SACD, mp3, FLAC,internet radio, etc.), will rumble still be a problem?
Yes, unfortunately you should still consider a high pass (rumble)filter that cuts or reduces most LF content below 15>20hz, especially with those very small drivers(6.5") which will never reproduce those frequencies anyways.
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Old 21st October 2012, 01:08 AM   #19
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by bjorno View Post
The four plots in the right column is IMO a sub I would recommended/ build.

On the right side and down a sub type...
Hi, The last sentence is a mistake...Should read: On the left side and down a sub type...Sorry for that.

b
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Old 21st October 2012, 01:23 AM   #20
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by Doug47 View Post
bjorno, I'm sorry, I still don't understand what you are suggesting. Are you suggesting a box with 12,6 liter volume? A port with volume 3,5 lt? Quoting one of my favorite lines from Hitchhiker's Guide, "Shapes, I need shapes!".
Hi,Dough,

I recommended the OD labeled simulation and for only one driver.If you want to use more than one driver the the CSA:s S1,S2,S3,S4 and S5 must be enlarged correspondingly e.g.:

If 3 drivers then S1...S5 should be multiplied with 3 to get the correct areas bu the section lengths L12...L45 should alwauys remain the same.

You need to learn HR, as a start look here:

b
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