DIY bluetooth speaker

[Mickster]

The Bazooka (sub) Bass Tubes were used as an example of how a speaker enclosure can be constructed using PVC pipe, the size of the driver was not taken into account.
What is the criteria which determines whether a speaker is a woofer, versus a sub-woofer?
Does a portable 'party' speaker such as the OP wants to build, need sub-bass? Probably not.
If a simple woofer would suffice, let's say something like a 4 inch diameter driver as rjenkins proposes, the enclosure would not be too heavy or unwieldy.
Another link from the Bazooka site shows some more examples, which could be similarly built from store-bought PVC pipe:
**broken link removed**
Combined with rjenkins' suggestion, the bass driver could be in the center t-section, and 2-way mid/tweeter drivers placed in the end of each elbow.

My 0.02c

 

[rjenkinsgb]

What is the criteria which determines whether a speaker is a woofer, versus a sub-woofer?

A woofer is just the larger / lower frequency drive unit in any two-way or three-way etc. speaker cabinet, normally with quite a wide frequency range, but not "full range" in itself.

A subwoofer is to fill in the range below what a normal HiFi speaker can easily produce & normally only handles low frequencies, with a high cutoff at anything from 100 - 300 Hz or so??

I don't know if there is any fixed definition, a lot of makers or sellers seem to use any key word they think will help things sell, regardless of actual capabilities.

Personally, I'd only consider something a true "sub" if it's got decent response down to somewhere around 20 - 30Hz (or lower) - the type of thing that properly reproduces bass drums / bass guitars and rattles the furniture if you get an explosion in a movie!

 

[SentinelAeon]

Btw i tested my new speaker a bit and it seems it goes very low. Probably to 40Hz. Kinda makes sense since i took the speaker from the woofer or subwoofer or what u call those cheap 2.1 systems with 2 speakers and 1 woofer. Anyway it really is awesome. I added 1ohm resistor in series so now it doesnt cut when on full volume. Now i just gotta add resistor for full range speaker so its foolproof for ppl who crank it to 100%.

 

[audioguru]

Just now I looked in Google for Audio Frequency Sweep With Display and found this:

It starts at 20Hz and my 2.5" or 3" computer speakers produce sound at 80Hz then get to the same loudness as much higher frequencies at about 140Hz.
Try it then keep the volume low enough so it produces a smooth sinewave and is not clipping which sounds like a raspy buzzer.

 

[SentinelAeon]

Can you comment on this cheap speaker ? And keep in mind im using cheap 2x25W amp and am not audiofil by any definition. And i like cheap price and i am ok with 4" as opposed to 3":

Home

Dayton Audio TCP115-8 4" Treated Paper Cone Midbass Woofer 8 OhmThe TCP115-8 combines a large motor, 1" 4-layer voice coil, vented pole, and a sizable rubber surround to make use of its 4 mm of Xmax. This combination of features makes it a very versatile driver which can be used as a bass driver...

www.parts-express.com

edit: here they say its actualy quite ok for its price:

 

[SentinelAeon]

I couldnt stop myself and ordered 2 of those tiny things

 

[audioguru]

I bought a pair of RadioShack Minimus 7 speakers (look in Google) when they were on sale long ago. Reviews said they sound good and in the store they sounded good. They have a 4" woofer and a 1" dome tweeter in a sealed cast metal enclosure that was fairly small. They were rated at 30W.
Within 2 years one woofer burned out. The original woofer was stamped 5W Korea so I ordered a replacement and the new woofer was stamped 10W Japan and it sounded fine and lasted for many years. I added a port and used it as a woofer for my beach portable stereo sound system.

The 4" woofer from Parts Express is much better than my old ones and if you make the enclosure large enough (3 litres) and a port tuned to 50Hz then it will make good bass sounds.

 

[SentinelAeon]

I will make the enclosure as small as possible, like always, for portability. I guess 3 litres is doable, its still compact. I plan to use passive radiators, the same ones i used in my last speaker. This time maybe i could seal the rear end of full range speaker ?

 

[Nigel Goodwin]

I bought a pair of RadioShack Minimus 7 speakers (look in Google) when they were on sale long ago. Reviews said they sound good and in the store they sounded good. They have a 4" woofer and a 1" dome tweeter in a sealed cast metal enclosure that was fairly small. They were rated at 30W.
Within 2 years one woofer burned out. The original woofer was stamped 5W Korea so I ordered a replacement and the new woofer was stamped 10W Japan and it sounded fine and lasted for many years. I added a port and used it as a woofer for my beach portable stereo sound system.

The 4" woofer from Parts Express is much better than my old ones and if you make the enclosure large enough (3 litres) and a port tuned to 50Hz then it will make good bass sounds.

As a ex-service engineer for a Sony dealer I was always horrified to look inside a Sony speaker - says 100W RMS on the outside of the cabinet, then the speaker inside is stamped 10W or 20W To be fair, it's not just Sony, it's all the lower cost audio gear.

 

[audioguru]

I will make the enclosure as small as possible, like always, for portability. I guess 3 litres is doable, its still compact. I plan to use passive radiators, the same ones i used in my last speaker. This time maybe i could seal the rear end of full range speaker ?

1) An enclosure that is too small increases the resonant frequency of the system with a peak and cuts lower frequencies= no bass.
2) Passive radiators that have spec's that do not match the spec's of the woofer are like holes in the enclosure allowing low frequencies at the rear of the woofer cone to go through the holes to cancel low frequencies at the front of the woofer cone= no bass.
3) The woofer has a good midrange response so you need a tweeter that is already sealed. Then add a simple crossover network which is an inductor in series with the woofer to cut highs, and a capacitor in series with the tweeter to cut lows. The tweeter will also probably need an attenuation resistor in series to reduce its sensitivity to match the sensitivity of the woofer.
If you seal the rear of a midrange speaker then you will increase its resonant frequency so high that it will sound like a low frequency fog horn.

I found a website that shows the frequency response of a speaker in a sealed and in a ported enclosure with various enclosure volumes

A New Approach to Box Design and Woofer Selection

www.mfr-eng.com

 

[SentinelAeon]

I will take a look at that page. I am still amazed though how i was able to make this speaker to sound so good. Like really good bass. I didnt calculte at all, i just took a center speaker from some 5.1 system, removed the speaker that was inside, added 2 speakers and 2 passive radiators. And trust me when i say a 300$ sony bluetooth speaker with oh so much talked about ultra bass function, well it was blown away. And my goodbye to my friend with JBL extreme 2 was: it's important to compete, not to win. He didnt get it, but everyone around did and laughed.

 

[SentinelAeon]

Btw i found out i have several pc power suply units that arent working. That gave me an idea and a new challenge. I wanna see how well of a speaker i can make in that small enclosure. Since i am dealing with a very very small box, i was thinking maybe i can put in a woofer and a small tweeter, then maybe add 2 or 4 smaller passive membranes. And the purpose of this would be to test if those passive membranes even help this setup or not. Well, we will see, i wanna test it

 

[audioguru]

Since your first speaker enclosure was randomly designed but was a success then you should buy a lottery ticket.
Look here:

 

[SentinelAeon]

You are mocking me again Btw, yesterday i tested the speaker at home with some ultra bass song and it tore the wire again. So this time i not only soldered it pretty well but also glued over it with epoxy. And it survived, 3rd time is the charm.

Btw when i get the 4" woofer i will ask u to help me design the enclosure. That is, the size. As u know i am trying to keep it as small as possible. So maybe u can help me find the optimal size that will be best compromise between bass and portability. Oh, and i also decided i will use 1 woofer to make speaker in the power suply enclosure. Just because i am interested how that would work. And yes obviously i know bass will be a lot less then it would be in bigger enclosure but i still want to test it.

 

[audioguru]

The woofer in a ported or passive radiator'ed enclosure flops around with no control below the enclosure/port tuned frequency.
Maybe your enclosure/port tuned frequency was too high then the woofer had no control at most bass frequencies.
If the tuned frequency is 40Hz then when bass plays frequencies near 40Hz the cone of the woofer hardly moves since the port or passive radiator makes those frequencies. But at frequencies below 40Hz like 20Hz then the cone moves Uncontrolled which might break its wires. Bass is seldom as low as 20Hz.
Your enclosure/passive radiator was probably tuned to 100Hz or 120Hz which cause the woofer cone to move a lot all the time with lower frequencies, but your videos showed the passive radiator also moving a lot. Maybe your woofer could not survive the high power, low frequencies you fed it.

 

[SentinelAeon]

Btw passive radiators move a lot, but i have no way of finding out if they actualy produce bass. Is there a way to test it ? Because when i put my hands over passive radiators, i dont feel like there is any less bass

 

[audioguru]

A passive radiator cancels bass if its spec's, the woofer's spec's and the enclosure's size do not match because when the woofer's cone moves outwards then the passive radiator's cone moves inwards.

The design is supposed to be so that when the woofer's cone moves outwards a little then the tuning causes the passive radiator's cone to also move outwards but move a lot which increases the bass sounds.
I guess that if you hold the passive radiator's cone still then the enclosure will act like it is sealed and the woofer's cone will move a little more but with less bass level.

 

[SentinelAeon]

What would be the easiest way to test the bass with some cheap instrument ? For instance lets say i make closed speaker, put song on and see the bass. Then i install 1 passive radiator, test it. Insert another passive radiator, test it. Add coins to passive radiators to see if they make it better or worse. I guess i could just use my ears but its kind of hard to tell what is better and what is worse.

I would like you to understand my motive behind this speaker building, so that u would be able to help me better. I am not low on cash, i could buy the baddest JBL bluetooth speaker and have awesome bass and quality and this and that. I am an engineer, both on paper and in my mind. And i like learning new things. As far as calculating passive radiators is not an option,since those i ordered dont have any specs. And even if it had, i wouldnt know where to begin to trying to find the right passive radiator, i know nothing about that.

EDIT: something just dawned on me. You said for good bass i need big enclosure. And i say for portability, big enclosure is a no go. But what if i was to make a speaker that could change its size ? Similar as a drawer, or those plastic bottles you simply retract when there is no water in them. Wouldnt that work ? So when i have speaker in backpack, its retracted. When i take it out, i simply transform it into 2 or 3 times bigger size.

 

[audioguru]

When I worked for a sound systems company, I measured the frequency response of expensive speaker systems.
The input was an expensive pink noise generator that fed a good amplifier and an expensive wideband microphone fed an expensive frequency level analyser.
The test must be done in an anechoic chamber that was not available so I laid the speaker on its back outdoors away from anything that makes echoes and hung the mic above it from a tree branch.

At home I made a cheap pink noise generator using an IC that is now obsolete and calibrated its resistors so that its output is exactly the same as the expensive generator at work. A very expensive microphone at work became obsolete so I took it.

You could use the online frequency sweep tone I linked and play it into your amplifier/speaker away from echoes. Then listen to what low frequency sounds almost as loud as much higher frequencies and listen for a peak on the level of any frequency.

 

[SentinelAeon]

What about that thing about speaker that can change the size of its enclosure on the go ? Would that be of any use ?