How to get more boomy bass?

Igla

Member
2003-06-29 8:45 pm
Slovenia
Hi,

I have a specific problem I can't solve or find anything usefull on Google.
The thing is I built a floorstanding boombox for my daughter.
Internal volume of the box is 55 liters (about 1.94 cubic feet) and it has 2 bass reflex ports at the back with internal diameter of 72 milimeters (about 2.94 inches).
I only put polyester damping sheets (1/2 inch thick) on back and bottom panel. This gives me the bass response I like.
The drivers are about 40 years old and I don't have any data except impedance and rated power (two 8'' woofers 50W/4ohm ; two mids 30W/8ohm). Mid drivers go high enough to also serve as tweeters.
We can say I just placed ''two loudspeakers in one box''. The amp is Lepy amp and the source is bluetooth module.
I will attach the photo later but just imagine two mid drivers at the top of the box and two 8'' woofers below. One mid and one woofer on left channel and the second mid and woofer on right channel. Below is quick drawing of crossover.
I don't have any measuring equipment and no drivers data to simulate the response so all tuning was done only by ears.
I'm used to the sound of my system but this boombox sounds good; perhaps too good for a boombox and old cheap drivers. It has the sound I usually like: rounded and reasonable deep bass, slightly recessed mids and nice hights. I can sit there and just enjoy the music.

So; where is the problem?
Well; my daughter (as all teenagers I suppose) does not care about transient response and micro details in bass response. All she wants is boomy, fat and punchy bass so in her dictionary ''only big and fat bass is good bass''. As big as it gets.

I can increase bass with tone controls on the amp or I can lower the mids and hights with crossover to virtually increase the bass. I could also do baffle step filter to increase the bass response but I would like to start with the tuning of the box.
I would like to tune the box in that way I could get as much bass as I can with this setup. I tuned the bass reflex ports by ears – I cut PVC pipes much longer then shorten them centimeter by centimeter and listened till I got the biggest bass I could.

Is there any other way to make this box to sound more boomy? If I understand correctly I would need to increase Q factor of the box/system. Correct?
How you do that?

Thanks for the answer;
Regards
 

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seedlings

Member
2007-04-20 9:19 pm
Given a 1.94 ft3 box with two 3” ports

ROUGH calculations
Length
8” tunes to 43Hz
4” tunes to 55Hz
0.5” tunes to 80Hz

If you want more boominess, triple the box size for a modest 6dB boost near port frequency. There is no magic. Probably just max out the bass EQ, or swap drivers.
 

impuls60

Member
2011-04-07 2:24 pm
Are you running a stereo signal in a mono box? Giving them their own volume might help giving more bass. If you add more loose dampening material the effective volume would get larger which would be in line with Seedlings recommendation.
 
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ILikeFoodz

Member
2014-06-22 12:33 pm
I always thought smaller box volume tended to result in higher Q/boomier bass? I know this is true for sealed at least. For ported I would imagine a higher port resonance qould also be needed, so one would shorten the port length. Am I missing something here?

If I'm correct, then filling in part of the box volume with something rigid like sand (don't actually do this, sand in the driver motor is a bad thing...) or sealing off part of the box and then shortening the port should give your "desired" result :)
 
Thanks for the answers.
I have attached a photo of my boombox. The loudspeaker is half finished. I need to finish a small box to put in power supply, amp and bluetooth module. It will sit on the top of the boombox.
I run left mid driver and upper woofer on left channel of the amp and right mid driver and the woofer at the bottom on right channel of the amp. This was the easiest way to connect the drivers with the amplifier I have available at the moment Lepy amp:
Lepai V3S Mini Hi-Fi Stereo Digital Amplifier Amp mp3 | eBay
I have tried one of my TPA3116 amps but Lepai runs those drivers better.

I have done lots of experiments:
-Insulation:
First I lined all internal walls with loudspeaker insulation (white polyester sheets about 2 centimeters thick). I had a feeling like the insulation was sucking bass energy. The bass was there but like it was stucked in the box and didn't came out.
Then I started to remove the insulation piece by piece.The best results I get if the insulation is only on the back wall and at the bottom. This sounds much better and it lets the bass go out of the box.
-Ports:
I tried removing both BR tubes but the bass became weak and small. Then I tried one port - 6 centimeters length gives the best bass. But the box gives bigger bass with 2 tubes. I played with the length of tubes and it seems that with length of 16 centimeters I get the most bass the box can give. I will try again and shorten both tubes during weekend inch by inch and listen.

It could be this is the limit with those woofers and I can't do anything else with the box and the only thing I can do is to crank up the bass potentiometer on the amp. Perhaps I could decrease the volume of the box to see the effect.

I could get better woofers but this suppose to be a cheap project with what I have available at the moment in my working room.
Those woofers are from old loudspeakers made by Ei Nis (a company from former Yugoslavia) - I have attached a photo I found on internet - about 20 liters closed boxes with mediocre sound and weak bass. I don't have and I can't find no parameters of those old woofers so I can't do simulations.
 

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R Kneck;
I have the cabinet against the back wall but I have no option to put it in the corner in my working room.
I think the bass will be more boomy in my daughters room but I will need to test it. This project is suppose to be a surprise so I need to wait till she go somewhere so I’ll have an hour or two to test the response in her room.
I need to check this loudspeaker test system. Thanks for the link.

Tsmith1315;
Yes; I’m 100% sure they are copy of some German drivers. They were made by Ei Nis factory. From all I could find on the net those woofers were always used in closed cabinets. Couldn’t find any bass reflex cabinets with those drivers. I also think those woofers are not ment to give fat and boomy bass. As my tests show they indeed are not the best option for my project.
I have attached a few photos of the woofer.

celef;
I will try to shorten bass reflex ports centimeter by centimeter during weekend and listen to the results.

For the sake of experiment and learning and mostly to have some fun I was thinking to replace the upper woofer with (about 30$):
WS 20 E - 8 Ohm | Visaton
and the bottom woofer with this (about 40$):
WS 25 E - 8 Ohm | Visaton

What do you think about those two woofers? Would they work in 55 liters cabinet?
I couldn’t find any cheaper woofers around here. If I order the drivers from let’s say Germany or UK I would pay more for shipping then the cheap woofers cost.
 

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I'm going to tell the story again:

Take a stereo amp, make a L+R channels mixer with two resistors (+ cap)
Take some single spare speakers, like 5" woofer and 3 " fullrange.
Build a cab for the woofer: mine was double chamber reflex> good bass<

THIS IS IT!

OH, yes: after the amplifier, each speaker has its own LP or HP
Again: some spare passive components do the job
 
fatmarley;
I know and I agree.
This was a project to replace boombox experiment I built for my daughter a few years ago.
It was fast and cheap built with some Westra 8'' woofers and some cheap tweeters from old radio. The box was made of computer cardboard box … you know … paper towels and some wood glue.
So; here we are.
I was bored and those woofers from Ei and other drivers (more Westra mid tone drivers and tweeters) were sitting on my shelf for +30 years so I said… what the hell … I’m bored …. let’s do an experiment.

I need to say; I’m used to full range loudspeakers/TDA1543 NO OS DAC/Gainclone/TPA3116D2/Valve amp sound but this boombox work very well as it is and the sound is not bad at all. The bass is good and deep enough, mids are just where I like them and hights are soft but detailed if you take in account cheap and old drivers.

BUT …. boombox should not sound good. Bass must be boomy and blown up and one note and exaggerated, would you agree? This is what an average teenager wants. That’s why they’re listening to those JBL one note bass battery loudspeakers and similar.

So I nicely asked this forum how to make loudspeakers more boomy with the drivers and other parts I already have on the shelf in my working room.
As simple as that.

picowallspeaker;
My English is somehow rusty so I didn’t fully understand your answer; sorry.
 

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I’m bored …. let’s do an experiment.

…. boombox should not sound good. Bass must be boomy and blown up and one note and exaggerated, would you agree? This is what an average teenager wants.

So I nicely asked this forum how to make loudspeakers more boomy with the drivers and other parts I already have on the shelf in my working room.
As simple as that.

Biggest woofer you can get into the box, then add lots of boost and a port to try to make up the lost bottom end = boomy one-note teenager bass. I lived in the car audio world for some years, and that all-too-familiar technique is one of the reasons I finally exited.

With what you have already built, (if you're not concerned about shredding the old Ei Nis woofers) try reducing box size significantly, like 30% to start. Just stuff something solid in there to take up space and see where that takes you. Bricks, books, basset hounds, look around and see what you've got that will go through the woofer hole. I'd start with port frequency in the 50 Hz ballpark. Keep experimenting with it.

A pair of the 20cm Visatons would probably serve your purpose well, you might even get a pair of 25cm's working in there. But since this is experiment and amusement, I'd fool around a bit more with the currently paid-for woofers first.

Be aware: All of these suggestions go against the normal hi-fi aspirations of the forum and are likely to be eschewed as something that will not work.