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DIY Subwoofer

March Audio

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#41
My eye can't help but be drawn to the pictures before reading...

An adjustable sliding dual-tweeter tall narrow front baffle was my initial instant impression here:

View attachment 15480
And I thought you were going to say something phallic ;)
 
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jhaider

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#42
Actually once you know the trick its quite easy. You need to make one of these for your router out of a bit of ply.

View attachment 15456

View attachment 15457
That's a neat jig. It looks more intuitive to use than the commercial ones, such as the "Jasper Jig."



However, the assumption is that one has a router to attach to the jig. That is a fairly specialized tool. If someone is not already a fairly avid woodworker, the assumption that one has a router sitting idle is unlikely to be true.
 
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#43
The Jasper Jig with a cheap harbor freight plunge router is perfect. I keep them permanently attached. The HF router isn't exactly a 'use every day' kinda router and I don't cut circles but maybe two dozen times a year. HF also has 20 to 25% off coupons rather frequently.
 

FrantzM

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#44
Ok

From iPad...

The bucket subs work and rather well. They require a lot of power. At least 200 Watts. I will try to measure this weekend and post the measurements.
I have performed simple REW measurements and have eq accordingly. Sounds good but not enough SPL for my leaky (typical tropical construction with open windows) room.
Later
 

FrantzM

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#45
Hi
I will ask for your kindness... I am a neophyte at this and am trying to learn on the fly .. With so much going in my business not much time to mess with things but the bucket subs work. This is the FR I got with 2 JBL LSR308 and the bucket-subs powered by a 100 wpc Rotel Amp... EQ via min DSP ....
FR in ROom with 2 BUSKET-SUBS.jpg


I am impressed I didn't believe it was going to be that good... It does sound like it though... MAX SPL @55 Hz is a low-ish 92 dB .. Am I reading this right or ???
 

RayDunzl

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#46
92dB maximum?

Have you tried to estimate their sensitivity? 2Vrms or 2.83Vpk signal - what SPL?
 

RayDunzl

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#48
Will try to figure out how
I would:

Take away the EQ and the 308s...

Put an A/C voltmeter on the speaker leads.

Play a tone with REW - 60Hz should not be inappropriate for a meter.

Adjust volume to produce 2Vrms or 2.83Vpeak - that's 1W at 8 Ohms, 2W at 4 Ohm

Perform SPL measure at various frequencies or sweep. Match the sweep level with the tone level in REW.
 

FrantzM

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#49
Not yet
Will try to figure out how
I would:

Take away the EQ and the 308s...

Put an A/C voltmeter on the speaker leads.

Play a tone with REW - 60Hz should not be inappropriate for a meter.

Adjust volume to produce 2Vrms or 2.83Vpeak - that's 1W at 8 Ohms, 2W at 4 Ohm

Perform SPL measure at various frequencies or sweep. Match the sweep level with the tone level in REW.
i will do it next week

Thanks Ray!
 

restorer-john

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#50
Adjust volume to produce 2Vrms or 2.83Vpeak - that's 1W at 8 Ohms, 2W at 4 Ohm
2.83V RMS is 1watt @ 8 ohms. (2W @ 4ohms) The peak voltage will be 4V, or 8V peak to peak.

2V RMS is 1 watt @ 4ohms. (0.5W @ 8ohms) The peak voltage will be 2.83V, or 5.65V peak to peak)

An AC voltmeter/DMM will read either True RMS or Average, which on a 60HZ sinewave will be the same (or close enough) :)
 

RayDunzl

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#51
Oooh...

My bad... Should have compared my volatile memory to the calculator...
 

FrantzM

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#52
Hi

I was trying to measure the sensitivity of my subwoofers. Lowish perhaps 83 dB but they were rattling like crazy. I decided to ditch the Leaktite buckets and went for 5-gallons paint buckets ... The Quikrete is setting now in these new enclosures and I will get back to the subs later and tell you all about them :)
 

bigx5murf

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#53
Did you ever end up measuring just the subs? The plans say this thing should be flat down to 25Hz. But plugging the specs into BassBox6 is showing F3 of 50Hz and F6 of 43Hz. While 25Hz is at -16db. There also seems to be a slight peak from 85Hz to 105Hz.
 

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