Simple Affordable PC Speakers - 5 inch Full Range

[Flint]

Over the past two weeks I designed and built a set of speakers for my main office PC using a nice full range driver from Tang Bang. I like the sound from this driver, but I am going to add a passive filter to it to get a smoother midrange response. Now that these are installed and operating, I am selling my prior speakers - SVS SB-01 bookshelves on Craigslist.

Here's some photos:


Dry fitting the parts of the enclosure


Different angle of the dry fit cabinet


Clamping the full enclosure at one go after gluing it up.


A view of the parts clearly showing the bracing and parts.

 

[Flint]

After sanding and sealing the MDF, I painted with the same Ocean Blue paint I used on my bathroom speakers.


Another shot of the painted speaker


The finished speaker


Both speakers finished and getting an initial operational test

 

[Flint]

In their final resting place for daily use


Here's the measured frequency response at the listening position.

As mentioned above, I'll be adding a simple series filter to lower the output between 600Hz and 6,000Hz to get a flatter response. Being a larger driver, the treble drops off pretty quickly, but so far I am happy with the sound and find it "dull" sounding. That said, I may add a tiny tweeter with a crossover at 8kHz just to restore the sizzle above 10kHz. We'll see.

 

[Flint]

I used a cardboard tube for the port to save the $15 a decent flared plastic port would cost. I also used a spare set of spring terminal input cups instead of binding posts which saved another $15. Additionally, the internal damping material is simple Polyfill stuffing from Walmart.

The bass output is very solid to about 60Hz, which is just less than an octave lower than the SBS-01 speakers they are replacing. And, with no crossover in the midrange, they have a very nice, clear, natural sound which I really like.

I have a set of small soft dome tweeters I may add in the future. Again, the crossover for the tweeters will be high as I only really want to add the top end shimmer these speakers lack.

 

[Dentman]

Is that the same driver as mine in 5" form?

I thought these might be replacing the powered speakers in your spare bedroom.

 

[Flint]

Is that the same driver as mine in 5" form?

I thought these might be replacing the powered speakers in your spare bedroom.

Yes, this is from the same design series as your smaller fullrange speakers used in your 2.1 system. I like that they have underhung voice coils which results is lower distortion and greater dynamics at the cost of peak output. Since these are a mere 18 inches from my face, I don't need much output from them.

Yeah, there is another project I am working on which will be powered, but they are quite different.

 

[jomari]

ah shit, just when i just bought some speakers for my goddamn main room.

any chance you can build speakers smaller than 4 inches, for an LCR setup? cheaply?

the part that sucks is even if it would be affordable, shipping would be a pain in the ass for me.

damn these look good tho

 

[Flint]

ah shit, just when i just bought some speakers for my goddamn main room.

any chance you can build speakers smaller than 4 inches, for an LCR setup? cheaply?

the part that sucks is even if it would be affordable, shipping would be a pain in the ass for me.

damn these look good tho

Um... Don't take this the wrong way, but asking me to make something "cheaply" is a little painful for me. I am trying to survive off this speaker building business and when asked to cut costs for a customer I assume that means I don't make any money to buy food and pay my electric bill.

 

[Flint]

ah shit, just when i just bought some speakers for my goddamn main room.

any chance you can build speakers smaller than 4 inches, for an LCR setup? cheaply?

the part that sucks is even if it would be affordable, shipping would be a pain in the ass for me.

damn these look good tho

However, thanks for the kind words. I means quite a bit that you find my work attractive.

 

[jomari]

Um... Don't take this the wrong way, but asking me to make something "cheaply" is a little painful for me. I am trying to survive off this speaker building business and when asked to cut costs for a customer I assume that means I don't make any money to buy food and pay my electric bill.

i hope i didnt offend you flint, i know for a fact that this is not an easy build, and includes manpower. this is one main reason QUALITY speakers require attention and detail, that only comes with time. apologies if i was overreaching. you truly can make some amazing speakers and i really appreciate you showing this stuff is definitely a great investment.

on a sidenote, i had to consider el cheapo speakers on my end, because i know for a fact that my kid plus a pencil and speaker drivers? not a good combination.

i dread to use my pb-1000 in the room, since its a front firing subwoofer with a plain jane cloth.

again, my apologies and i dont mean to offend. quality materials, quality components, quality craftsmanship can never be cheap.

 

[Flint]

I thought I would share a little of my design process for the LCR filter I am going to insert inline with this loudspeaker in order to smooth out the midrange response to be balanced with the bass and improve the apparent treble to some degree.

Note that this speaker has a baffle size of 10-1/4 by 8-1/2 inches. That means the baffle step loading will start to drop at about 400Hz and reach a full 6dB drop by 330Hz. The math for determining this is: Speed of Sound divided by Length divided by Four. The speed of sound in inches is 13,536 inches per second. The short length is 8.5 inches. So, 13,536 / 8.5 / 4 = 398Hz. the long length math is 13,536 / 10.25 / 4 = 330Hz. That is not complicated math, is it?

So, I knew the filter would have to start having an impact on the electrical signal going to the speaker starting at approximately 300Hz. Since the treble starts rolling off significantly at about 5,000Hz, so I wanted to end the influence of the filter at about 5,000Hz so the signal above that frequency is not reduced.

Rather than relying on the math to determine the ideal filter, I performed measurements from the location of my head while seated at my desk in front of the speakers. The goal is to get the best sound in this real world location, not in an anechoic chamber. I input the measurements I made of both the acoustical frequency response and acoustic phase response as well as measurements of the electrical impedance and electrical phase into a crossover modelling program I own and created a virtual filter based on the math then adjusted the values of the resistor, inductor and capacitor to get the best results for my actual real-life system.

After fidgeting with the values and settling on something I think will work well, the finished filter I am going to make looks like this:


As shown in the diagram, the positive signal has the filter inserted inline. The inductor determines at which low frequency the electrical signal will be reduced as the frequency raises. The capacitor determines at which high frequency the electrical signal will stop being reduced as the frequency raises. The resistor determines how much cut in level the filter will peak at the center of the operating range. All three interact with one another, so changing the value of any single component will alter the resulting performance of the others to some extent. So, having a modeling program is essential to the design process. In the olden days before simple crossover simulators existed, I would calculate using lots of paper, equations from a filter design book, and a proper electronic calculator to estimate the ideal values. Then I would assemble a test filter and measure the results electronically and acoustically, which also meant plotting values on logarithmic graph paper. Then I would alter the filter to adjust for real world results until I got the performance I was seeking. I got pretty good at testing up to 6 variants of a filter in one day using that method - and I thought I was fast!

Anyway, in addition to the components of the filters impacting one another, the impedance of the loudspeaker is also not linear. That means that how the filter would operate if the speaker were a perfect resistive load of 8 ohms (which is how the manual equations are written), the actual impedance of the speaker is reactive and thus the performance will vary. At a test voltage of 1V, the resistance of this particular driver at 300Hz is 7.53 Ohms, but it rises to a resistance at 5,000Hz of 11.9 Ohms. So, a capacitor calculated to be a certain value based on an 8 Ohm load will not start to impact the signal at 5,000Hz. Keep in mind, the impedance changes with input voltage, as well, because heat and the voice coil's position in the magnetic gap also cause variation in the resistance at various frequencies. These variations in impedance based on voltage and the reactive nature of the driver itself are major contributors to why I heavily recommend active crossovers and the complete removal of any passive components in a crossover/filter.

 

[Flint]

So, here's the predicted impedance plot of the speaker with and without the filter inserted:


Blue = Load on amp for Speaker without filter / Red = Load on amp for Speaker with filter

Note that the cause of the reduction is the nature of the filter. The inductor starts resisting the voltage at about 200Hz and forces the signal through the resistor, adding almost 8 ohms (the value of the resistor in the filter) to the impedance at the high point of 2,000Hz. Then, the capacitor starts passing the signal without resistance at higher frequencies until at about 9,000Hz where it is passing the signal without any added resistance. In fact, due to the nature of any passive filter, there is a point above 11,000Hz where the resulting resistance on the amp is very slightly lower than the speaker alone.

All good, right? Well, there are consequences to adding a passive filter. Look at what the filter is predicted to do at frequencies below 100Hz! That is actually decreasing the effective damping value of the amp on this speaker system. It is not a huge drop (no more than about 1/3 Ohm), but it is there and it will have a detrimental impact on the performance. But, at the very low levels I am listening in this location and the fact I am not expecting killer bass below 60Hz, I don't think the impact will be grossly obvious, if audible at all. This issue, the decoupling of the speaker from the amplifier's output, is another reason I always encourage the use of active crossover and the absence of any passive components between the amp and the drivers in a speaker system.

 

[Flint]

How does the modelling software predict the acoustic performance of the system will change with this filter?


Yellow = Speaker Frequency Response with no filter / Red = Speaker Response with filter

Keep in mind, this chart is based on real measured acoustic performance where I will be listening to these speakers. That means things like the reflection off the desk is causing a null centered at 320Hz and all the other acoustical issues associated with placement of both the speakers and the listener.

But, clearly the filter starts having a subtle impact on the sound starting at about 240Hz but gets serious at about 450Hz and peaks in the range from 1,000Hz to 2,400Hz before returning to having no impact at about 7,000Hz. The overall impact is similar to what would happen if I took a graphic EQ and cut all the sliders in the midrange with the most extreme cut being -5.5dB at about 1,500Hz and generally not touching the sliders below about 200Hz or above 6,000Hz.

This is what a passive filter looks like, how it works, and what it does to the signal in relatively simple terms.

It is very difficult to get into the dynamic and time-based impact on the performance when using passive filters. Capacitors have a rise time, decay time, and inherent crossover distortion when the voltage flips from positive to negative. Inductors interact with the speaker's voice coil and magnet and also have decay time issues. And resistors can shift in value based on temperature caused by high signal levels. If the voice coil in the speaker gets hot (as in listening at high levels), the values of the inductors and capacitors become too large or too small, in an asynchronous fashion (meaning that inductors need to be smaller at higher voice coil resistance levels and capacitors need to be larger at higher resistance levels), so the effective filter slopes slide apart from (or towards) each other. It is insane all the issues passive crossovers / filters inherently have. And, yes, these are yet more reasons I always encourage the use of active crossovers without any passive components between the amp and the speakers.

 

[Flint]

Oh... I should comment that unlike a traditional electronic graphic EQ, with common LCR circuits you cannot increase the voltage passing through the circuit to the speaker. You can only reduce it, or "pad" it down. There is an exception using a transformer (which Klipsch has used very successfully - and may still use today), but it is difficult to get a transformer to work except in very special situations which usually require high impedance loudspeakers, like a 16 or 24 Ohm driver, as many compression drivers for horns offer.

As, aside from when using a transformer, any time you use a passive filter, you are cutting the signal going to the louout 87dspeaker. That means you are sacrificing the effective output of the system for a given input level. In my speaker, above, I am sacrificing up to 5.5dB SPL of acoustic energy for the same volume setting on the amp. However, I am doing it to balance the output in the midrange to the lower output in the bass and treble.

According to the TB spec sheet, the sensitivity of this 5" driver at 1kHz is 90dB at 2.83V at 1M. With the filter I am adding to the speaker, the new sensitivity is going to be about 86.5dB SPL at 2.83V at 1M because the filter is effectively cutting the 1kHz output by about 3.5dB.

At the risk of becoming like a broken record, this is yet one more reason I encourage the use of active crossovers over having any passive components between an amp and a speaker. This is why my new Statement speakers can play louder than any sane person could ever handle in my room while using a mere 45 watt amp on the midrange drivers and tweeters. In fact, they are so sensitive, I took out my very high quality Paradigm Halo A23 amps due to the noise floor being audible and replaced them with the smaller amps which reduced the noise floor by over 5dB.

 

[Flint]

One more note on the process...

I am not assuming the predicted ideal filter is going to be the final filter. However, I had to order the inductors to make them, so I cannot go with a larger value for the inductors. I can unwind the wire on the inductors I ordered to achieve a lower value, but I cannot increase their values. I have several resistors in values all around the desired 8 Ohms, so I can easily alter them. I have a jar full of capacitors of various values and quality, so I can easily wire them in parallel to get almost any value I need near to the predicted target.

If I do decide a larger value inductor is worth the effort, I could order some more at about $6 each, but I would have to feel the change in performance is worth the costs.

 

[Randy]

They look cool for sure and I am sure they sound great.

Another nice project FF.

 

[The DirtMerchant]

Just what $ amount does "affordable" mean?

 

[Flint]

Just what $ amount does "affordable" mean?

Well, since my labor is "free" to me, the cost is relatively low because I used MDF pieces which were cutoffs from other projects, cardboard tube ports, and input cups I've had in my parts drawer for years. The only real expense to me was the paint (about $10 worth), wire & solder (about $1), glue ($0.50), and stuffing material ($2). I bought these drivers on a daily special deal for about $42 each. So, my costs (not including time, wear on tools, expendables like paint brushes, gloves, and paper shop towels), and electricity, is less than $100. I haven't considered the costs of the LCR filters, yet, but if I did and included replacing the parts I am using out of the parts drawer (which I will eventually need to do), they are probably about $20, or less, in components. So, approximately $120 for the ingredients I had to buy for this project or parts I will definitely be replacing.

Now, my time investment is about 40 man-hours (including an extra 8 hours I anticipate will go into fine-tuning and installing the LCR filters). I know what I charge for my time, but I'll let each of you determine what you think someone's time is worth with my level of experience and expertise.

 

[Huey]

Well, since my labor is "free" to me, the cost is relatively low because I used MDF pieces which were cutoffs from other projects, cardboard tube ports, and input cups I've had in my parts drawer for years. The only real expense to me was the paint (about $10 worth), wire & solder (about $1), glue ($0.50), and stuffing material ($2). I bought these drivers on a daily special deal for about $42 each. So, my costs (not including time, wear on tools, expendables like paint brushes, gloves, and paper shop towels), and electricity, is less than $100. I haven't considered the costs of the LCR filters, yet, but if I did and included replacing the parts I am using out of the parts drawer (which I will eventually need to do), they are probably about $20, or less, in components. So, approximately $120 for the ingredients I had to buy for this project or parts I will definitely be replacing.

Now, my time investment is about 40 man-hours (including an extra 8 hours I anticipate will go into fine-tuning and installing the LCR filters). I know what I charge for my time, but I'll let each of you determine what you think someone's time is worth with my level of experience and expertise.

Well since you are a 13 year old Polish girl with one leg longer than the other, and whose father beats her terribly, You'll probably get a few more dollars than the other guys, just for sympathy.

Seriously though, I wouldn't have told what the costs where, but based on what you stated they were, I'd say 3 to 5 times the costs of the materials should be the final price.

 

[Flint]

Well since you are a 13 year old Polish girl with one leg longer than the other, and whose father beats her terribly, You'll probably get a few more dollars than the other guys, just for sympathy.

Seriously though, I wouldn't have told what the costs where, but based on what you stated they were, I'd say 3 to 5 times the costs of the materials should be the final price.

I don't imagine ever selling these.