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Boominator MINI (development thread)

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Saturnus View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Saturnus Quote  Post ReplyReply Direct Link To This Post Posted: 14 June 2018 at 3:01pm
Originally posted by protos protos wrote:

Saturnus what do you mean by high frequency "ringing"?

All sounds are basically made up of a multiple of frequencies. These have different individual ADSR (attack decay sustain release) parameters. By adjusting the sustain and release parameters you can compensate for in-room ringing due to sound at higher frequencies bouncing off walls indoors to make a small and typically "hard" sounding room more "soft", and the reverse when outdoors where there's no resonances in the high frequency range which makes it more "soft". That's great if you're using piezos however as they outdoors can sound quite tolerable but for accurate sound reproduction it's typically a good idea to mimic what the intended listening room was when the recording was made. And that will typically be a normal living room.


Edited by Saturnus - 14 June 2018 at 3:02pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote protos Quote  Post ReplyReply Direct Link To This Post Posted: 15 June 2018 at 7:51am
I thought you meant tweeter resonances. Room echo in an untreated room typically makes the sound harder rather than softer unless there are a lot of furnishings curtains and carpets which will absorb HF content.
Outdoors obviously there is no room reinforcement in the bass plus no HF bouncing of any hard surface so in principle there is a roll off at both ends. But a normal EQing should solve this.I understand the psychoacoustic bass synthesizing principle but I don't get how HF ringing is adjusted un less it is the same principle. Unless you introduce ringing digitally by dela ying the fundamental by a few microseconds and adding it to the signal.Do you have a link?


Edited by protos - 15 June 2018 at 7:58am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Saturnus Quote  Post ReplyReply Direct Link To This Post Posted: 15 June 2018 at 8:53am
What I'm doing is applying the same principles as linkwitz transform but to higher frequencies instead of lower frequencies. Linkwitz transform basically transforms the natural Q of the speaker to something you select. Typically this is done to make it possible for a small speaker enclosure to have better low frequency capability. But if you have different settings you can switch between, you can set the Q and the low frequency response to suit different room sizes to take maximum advantage of the room gain, or lack thereof.

You can apply the same principles to higher frequencies as well by adjusting the linkwitz transform formula to work with higher frequencies instead of lower frequencies if you combine it with a peaking filter  to compensate for the high frequency drop off. The peaking filter is key as you need to have a relatively flat frequency response to a fixed frequency, typically 20KHz, regardless of what the (high frequency) Q is adjusted to.

Naturally, this is a very basic method of doing this as it can be done with just 2 parametric bi-quads but it works really well when you have a few discrete predefined settings that is fine tuned by ear. For the DSP to calculate the settings on the fly would be an absolute nightmare.

The reason this method is far better than just using an EQ to adjust for the room resonances is that EQ'ing doesn't solve the underlying problem. By EQ'ing you just adjust the overall response of the speaker to compensate for room resonances. However, by adjusting the Q you make the high frequency response harder or softer from the speaker itself which affects the room resonances as well.

I don't have a link to my own research, no.


Edited by Saturnus - 15 June 2018 at 9:41am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ovaldezkep2 Quote  Post ReplyReply Direct Link To This Post Posted: 29 June 2018 at 6:21pm
Saturnus, 

It's great to hear from you once again, welcome back! Are you using the 4 ohm version or the 6 ohm for the Dayton Audio ND16FA tweeters? Looking forward to building the new design of the mini. I must say that I love listening to my NS6 Mini and I get a lot of compliments when I bring it out to the beach. 

Looking forward to the new design using the newest technology.

Thanks


Edited by ovaldezkep2 - 29 June 2018 at 8:46pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ovaldezkep2 Quote  Post ReplyReply Direct Link To This Post Posted: 09 July 2018 at 9:13pm
Here's a pic of my Boominator collection.. I've been meaning to post this picture for some time. I'm very happy with the sound these produce. I also really enjoyed making them with my dad its a great hobby to have with someone who enjoys to work with there hands. 





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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aterren Quote  Post ReplyReply Direct Link To This Post Posted: 09 July 2018 at 9:41pm
Nice!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Larzman Quote  Post ReplyReply Direct Link To This Post Posted: 10 July 2018 at 2:01am
definitely a nice looking collection of Boominators. Might even get me motivated to complete mine, all I need is the wood for my Mini.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aterren Quote  Post ReplyReply Direct Link To This Post Posted: 10 July 2018 at 2:26am
when you say mini, which drivers?   I may have some parts to help (assuming you are in the USA).  :)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Larzman Quote  Post ReplyReply Direct Link To This Post Posted: 10 July 2018 at 3:55am
the parts are from the original mini-Boominator design, using what I think were NS6 speakers, whatever was in the original design. I just didn't get the wood and put it together, wood is not my forte', so I guess I didn't have the correct tools to make the cutouts accurately.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aterren Quote  Post ReplyReply Direct Link To This Post Posted: 16 July 2018 at 4:12am
Originally posted by Larzman Larzman wrote:

the parts are from the original mini-Boominator design, using what I think were NS6 speakers, whatever was in the original design. I just didn't get the wood and put it together, wood is not my forte', so I guess I didn't have the correct tools to make the cutouts accurately.

I took a look at my parts and I think I can help you with an assembled frame (all but the baffles) and baffles cut to size and with driver cutouts.   The only thing I am not in a position to do in the near term is route the baffle round over.   PM me if you are interested, otherwise I'll finish the build and put a DSP rather than the passive filter in it.  :)

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tafse Quote  Post ReplyReply Direct Link To This Post Posted: 17 July 2018 at 7:22pm
Good to see you back in the game Saturnus!
I'm returning to the world of DIY audio for a new project, and the boominator mini looks perfect!! Built your original Boominator 7 years ago, and the thing is still going strong. I cannot begin to tell you how much joy it has brought, and short of new batteries and paint the maintence required has been ridiculously low, considered what it has been through. On behalf of myself and all my friends, I sincerely thank youHeartHeartHeart!

So, obviously, I absolutely have to build the Boominator mini too. So I might just go ahead and order the parts right away and await your further instructions. Any change in the choice of parts since your first post?
I haven't managed to find a european seller for all the parts (Im in Norway). Are http://https://www.ebay.com/itm/WONDOM-JAB-Amplifier-w-Bluetooth-DSP-AUX-Volume-Control-30W-50W-60W-100W-/112421366508#shpCntId - these the correct boards (nr. 3 and 5 on the list)? The sellers offers cable packages too, so looks like a good place to grab it all. The woofers and tweeters looks rather easy to come by, and audiophonics.fr looks to be the closest shop to have them both.

Again, thank you for the original, looking forward to the sequel

EDIT: Im actually just bad at searching, found the boards on the same audiophonics store http://https://www.audiophonics.fr/en/amplifier-boards/sure-aa-ja32171-jab-2-50-bluetooth-40-stereo-amplifier--d-21-2x50w-4-ohm-p-10847. - 2-50 and http://https://www.audiophonics.fr/en/amplifier-boards/wondom-aa-ja32172-jab-3-50--d-stereo-amplifier-module-with-dsp-2x50w-p-12162. - 3-50 . Are these the correct ones? If so, I only need a bit of help locating the correct cables


Edited by Tafse - 17 July 2018 at 7:36pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Saturnus Quote  Post ReplyReply Direct Link To This Post Posted: 17 July 2018 at 8:22pm
Yes. There are some changes. These are due to lutkeveld's specialized amp that will come later.

For that amp it'll not be possible to use the 4 ohm version of a the ND140 paralleled to 2 ohm.

Instead use the 8 ohm version of the ND140, and higher battery voltage with 6 cells of lifepo4 for 19.2V.

That does mean we can use the cheaper JAB2 and JAB3 in the 30W version though as an alternative to the specialized amp. Note you need the special cable set to connect the JABs.

Places to get some of the stuff in Europe besides what you already mention are:




Edited by Saturnus - 17 July 2018 at 8:24pm
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