Mini Boombox Audio Equalizer - Page 1
Forum section: electronics / beginners

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 24, 2015, 02:43:45 am
content: Hello everyone. I am constructing a portable speaker system that can outperform my friends bose unit (which produces a fair bit of bass for a small cabinet but the highs sound like crap) amd I have designed my own set and this one has altec lansing woofers and tweeters plus a passive membrane. I have tuned the box and membrane to work best with the speakers, then I connected it to my PC, adjusted my hacked soundboard for boosted lows and highs, and it works quite well. However, carrying 10 pounds of amplifier and soundboard is not portable. I have purchased a PAM8610 20w class D amp, and it works fantastic. Never thought a 6mm^2 chip could deliver that much. Now, I am looking for a good method of adjusting the frequency response. Anyone got any ideas such as a premade configurable sound processor? Thanks!

author: PeterFW
author_rank: Frequent Contributor
timestamp: April 24, 2015, 10:44:27 am
content: I do belive this is overkill but if you really have tuned the low end drivers to the passive membrane with a proper measuring this is the cheapest thing you can get wich is a drop in part:http://www.minidsp.com/products/minidspkits/2-x-in-4-x-outWould be even better if you run a active 2 way system with this board.How dit you design your cross-over?

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 24, 2015, 01:34:06 pm
content: My crossover is one from my dads JBL days. He was one of the JBL toon truck builders. Is there just a simple EQ board anywhere?

author: PeterFW
author_rank: Frequent Contributor
timestamp: April 24, 2015, 01:49:40 pm
content: Quote from: iamdarkyoshi on April 24, 2015, 01:34:06 pmAh... never mind then.Wacking parts together will not work, subjectively it migh sound better to you but compared to something with a flat frequency response it will sound horrible.Most likely your driver is allready working at its linear excursion limit.A crossover has to be designed for a specific set of drivers and at the top end, even the enclosure.And you will not be able to make something better then a bose system, even though bose is not the best speaker manufacturer without at least simulating it.Ask ebay for the next best china "treble bass control","bass boost", "grapic eq" or something like that.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 24, 2015, 01:57:55 pm
content: Well, I can tune this to sound good. I have an expensive RTA and calibrated mic, so once things can be adjusted, I can get a good output. Thanks for the advice though.

author: PeterFW
author_rank: Frequent Contributor
timestamp: April 24, 2015, 02:12:51 pm
content: Quote from: iamdarkyoshi on April 24, 2015, 01:57:55 pmAllthough DSP can make magic happen it will not remove phase differences and resulting bad directivity.Without a parametric EQ (or at least 32band grapic eq) you will not be able to dial it in annyway.If you do not want to design your own passive crossover and have a decent microphone the above linked DSP will produce a decent speaker if you run it in a active 2 way setup.If you have a microphone with a calibration file you should to the whole thing the right way...But remember that PC soundcard microphone inputs might have a horrible sloping frequency response below 100Hz.The hole cost of a completely active 2 way speaker setup can be 120 bucks for the electronics, those you will be able to use for a long time and they can be repurposed into soooo many different speaker designs.But either way, measure the windowed near field impulse response (very close up to the speaker) indoors or you have to go outside to get decent results.If you try to measure the "subwoofer" indoors you will measure pure garbage because the only significant data you will aquire are the internal reflections and standing waves (modes) of the room.

author: lutkeveld
author_rank: Regular Contributor
timestamp: April 24, 2015, 05:09:46 pm
content: You can't DIY a speaker that outperforms a Bose in the same size.Especially if you throw together a random set of components.What do you dislike about the high tones? Maybe you can DIY a small PLLXO to change the response a bit.

author: PeterFW
author_rank: Frequent Contributor
timestamp: April 24, 2015, 05:32:09 pm
content: Quote from: lutkeveld on April 24, 2015, 05:09:46 pmYes you can, depending on the definition of "outperform"You will be able to build a speaker with a very nice flat response, decent directivity and a resonable low end roll off.But it will not produce the same amount of "BOOM! BOOM!" because very bose product i ever say in a small form factor with a decent "BOOM! BOOM!" uses a "one note bass".A one note bass is what describes a high peek at a low frequency with a steep roll of on both sides. Lets say 80Hz, the 80Hz will be reproduced with +10dB and slope off to 120Hz to 0dB above the mean SPL.Below 80 it has a steep roll of to nothing to limit the linear excursion and cut of the sub sonics.That makes good "BOOM! BOOM!" but not a good soundYou can do that several ways, the most atrocious i saw was a 6th or 8th order band pass enclosure with heavy DSP trickery.But passive radiators do just as well, as long as the driver is designed with that in mind to the right resonance frequency in the desired "one note bass" band.I do have to say, the "bose soundlink" is a awesome little speaker with great performance, but it is very pricey for what it does.Bose has a few nice products but for the most part they are ridiculously overpriced.Two small full range speakers coupled with two decent low end drivers in a active 2-way FAST system will produce a very nice sound when dialed in with a proper measuring set up.The above information may contain false information due to my lack of knowledge about the proper english terminology a.k.a. translation error.

author: lutkeveld
author_rank: Regular Contributor
timestamp: April 24, 2015, 06:53:40 pm
content: With 'you' referring to OP, not 'you' in a general sense. Bose has the adventage of custom drivers, DSP options and injection moulds that are out of reach for the normal DIY'er.DIY gets interesting from 3 liters (external) and up. Under that it's fun, but competing with commercial options is difficult unless you really know what you're doing.BOOM BOOM is indeed the result of dynamic DSP'ing. When you turn it up it usually disappears because the drivers can't keep up mechanically.They also use some psycho acoustical tricks to trick your brain into thinking there is low bass, while in reality there isn't really.Bose is king in the portable market. Maybe overpriced for what it does, not for what it is.Have a look at the BOM and certifications. That stuff costs money.FAST is a misnomer for a PR system. A passive radiator is just a bassreflex port alternative, you wouldn't call a BR system a FAST would you?

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 24, 2015, 06:56:36 pm
content: The microphone is calibrated to the RTA, a standalone unit. But I will admit that the Bose does have a one note bass. I have gotten decent results with mine, but I will add a second set of drivers for just the lows, then a full range set for the rest.

author: lutkeveld
author_rank: Regular Contributor
timestamp: April 24, 2015, 06:59:16 pm
content: 2.1 is a stupid choice for small portable speakers

author: PeterFW
author_rank: Frequent Contributor
timestamp: April 24, 2015, 07:21:59 pm
content: Quote from: lutkeveld on April 24, 2015, 06:53:40 pmA passive radiator is not the same as a BR port, but they are close.The passive membrane has some advantages but they are drawbacks as well...F.A.S.T = Fullrange + Subwoofer, a small full range speaker is used together with a subwoofer and a very low crossover point way, way under 1Khz.Classiv two way system but instead of the tweeter you use a small fullrange speaker.There are some very nice, very high excursion subwoofers that work really nice in a sealed box under 3L with a linkwitz transformation.What that has to do with a PA system, i do not know...But i dont want to get into a discussion about "who knows more"... i have hung too many PA speakers and spend too much time building my own to care about a pissing match...

author: lutkeveld
author_rank: Regular Contributor
timestamp: April 24, 2015, 07:34:23 pm
content: I said 'alternative'It's based on the same principle; helmholtz resonance.I think you misread my post. I said 'PR'-> passive radiator, not PA->public adress.I meant to say that using a passive radiator with a fullranger isn't what's known as FAST.FAST is with an active subwoofer, crossed to a fullranger as you say.Linkwitz would be bad decision for a portable system since you have a limited voltage swing available.Not trying to start a pissing match at all. Just a dicussion. Maybe I should use more smileys

author: PeterFW
author_rank: Frequent Contributor
timestamp: April 24, 2015, 08:07:06 pm
content: Quote from: lutkeveld on April 24, 2015, 07:34:23 pmAh. okThey are in theory much better, i was blindet by lack or port resonance, low tuning frequency, no escaping noise (air and internal sound) and smaller cabinets for a while and ran a lot of simulations.But they allways fell short and the group delay went through the roof.Even way into the upper low frequencys were it does start to matter.Even tried stuffing short BR tubes with various stuff to achieve a "desinged leakage".Now i like closed boxes for everything above 100Hz and propper bass reflex for everything below with a bit of sprinkled in DSP and a semi passive cross over ;^^QuoteWell then, everythings good, will do

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 25, 2015, 12:35:06 am
content: Wow, thanks for the responses everyone. I own a large 3D printer, and access to my schools printer, so cabinets arent an issue. I also have plenty of speakers to dink with.

author: lutkeveld
author_rank: Regular Contributor
timestamp: April 25, 2015, 05:14:44 pm
content: Using several known formula's and the CAD programs based on them to design a speaker is much easier than trial and error.If learning is the objective: go ahead. If beating Bose is the objective: good luck

author: PeterFW
author_rank: Frequent Contributor
timestamp: April 25, 2015, 05:53:33 pm
content: Quote from: lutkeveld on April 25, 2015, 05:14:44 pmOh yes, cheap medium density fibre board is by far the best bang for your buck.If you 3D print... there are some problems with 3D printing speaker enclosured.Allthough i have seen someone build a decent set of speakers using a 3D printer to incorporate a seamless waveguide right into the front.QuoteHehe, in theory it should be pretty easy:One 2x2 DSP Unit = 80 BucksOne cheap 4 channel class D amp = 20 BucksOld laptop brick = 0 to 10 BucksTwo 2 inch full range drivers = 30 BucksTwo 3 inch subwoofer drivers = 60 Bucks (one would be enough)Calculate a decent small BR enclosure, stick everything in a box, sub in the middle, full range left and right, cross over at 300-800hz and fiddle with the knobs on the DSP until your microphone shows a reasonably flat response.That should sound way, way better then the bose box, i would wager that it will sound damn good if you chosse the right drivers, not loud but damn good.But it will be a bit more pricey and at least 4 times bigger then a bose soundbar

author: lutkeveld
author_rank: Regular Contributor
timestamp: April 25, 2015, 06:01:27 pm
content: If Hoffman and his stupid law didn't exist, speakerdesign would be much easier ;pIt's easy to beat a bose soundlink soundwise. It isn't easy when you maintain the same formfactor

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: April 25, 2015, 09:53:04 pm
content: Well, there becomes a point where form factor is negligible. A Macbook Air is just as portable as my laptop, but my laptop can have 5 more USB devices plugged in. and costs less. This is sorta what I am trying to achieve. So far, with my soundboard's EQ, my unit sounds as good as my friends bose, and it can go WAY louder. Now I need to find the mic for my RTA...