Hi All,
I am using the formula 15 x Vas x (Qts^2.87) to calculate volume for bass reflex enclosure for the attached full range driver.
Vas = 38.21 L
Qts = 0.93
I am getting a volume of 465 L which is very very large.
First of all ... is this formula correct?
Is there any other way to calculate the volume?
Thanks and regards,
Naveen
I am using the formula 15 x Vas x (Qts^2.87) to calculate volume for bass reflex enclosure for the attached full range driver.
Vas = 38.21 L
Qts = 0.93
I am getting a volume of 465 L which is very very large.
First of all ... is this formula correct?
Is there any other way to calculate the volume?
Thanks and regards,
Naveen
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Well, it's one of several that's been published over time, though personally prefer this one done many years later that calculates larger cabs: Vb = 20*Vas*Qts^3.3
FWIW, the pioneers based Vb on what we call the Vas spec and while technically correct in some ways it's ill suited for small Vas drivers, especially if it's a high Qts, so would need to be tuned using a ~aperiodic vent to damp its ~ 'one note' mid-bass response: Vb = Vas/1.44.
GM
That driver won't make any bass. The fs is too high, even in 500l the -3dB point is at 77Hz. I see 3 options to use this driver:
1. Open baffle. It still needs bass support.
2. 50l sealed with a highpass-capacitor (likely ~300-400µF) which interacts with the impedance and draws it flat at the bottom, around 110Hz f3. The C acts as a low cut too, you only have to add a Subwoofer and no other electronics in the path of the fr speaker.
3. A TQWT could maaaybe work but the driver won't make much bass because it got a very limited linear excursion (< 1 mm) and won't go very deep either because of the too high fs.
4. 30l sealed or OB + subwoofer and dsp, wich can easily cross it over and eq it flat at the bottom.
You'll most likely have to eq the fr driver on the upper range anyway which means you'll need one or several filters. That means NO. 4 is the most promising solution because you have the speaker directly on the amp and the least losses and - as already said - the driver needs EQing in some way.
If you didn't buy it yet, you'd better look for other drivers if you want a pure fr speaker. If you did, I'd go for OB + Sub + DSP (miniDSP is a good choice).
1. Open baffle. It still needs bass support.
2. 50l sealed with a highpass-capacitor (likely ~300-400µF) which interacts with the impedance and draws it flat at the bottom, around 110Hz f3. The C acts as a low cut too, you only have to add a Subwoofer and no other electronics in the path of the fr speaker.
3. A TQWT could maaaybe work but the driver won't make much bass because it got a very limited linear excursion (< 1 mm) and won't go very deep either because of the too high fs.
4. 30l sealed or OB + subwoofer and dsp, wich can easily cross it over and eq it flat at the bottom.
You'll most likely have to eq the fr driver on the upper range anyway which means you'll need one or several filters. That means NO. 4 is the most promising solution because you have the speaker directly on the amp and the least losses and - as already said - the driver needs EQing in some way.
If you didn't buy it yet, you'd better look for other drivers if you want a pure fr speaker. If you did, I'd go for OB + Sub + DSP (miniDSP is a good choice).
Your speaker strangely resembles vintage Philips full range speakers , I forgot AD???? . You find here some ideas . Bass reflex box design for Vintage Philips AD3806RM full range driver. | DIY Audio | Pinterest | Box design, Diy speakers and Design
The fullrange driver is from Sweton Speakers, India. The cone and whizzer aren't coated, the sourround is. They are available from Amazon India for ~15 bucks. They extremely likely couldn't implement a pole core copper cap to fight the impedance rise, especally for that price. They will not sound like the old Philips.
For that price you can't do anything wrong either, for an OB experiment with subwoofer it's probably worth it.
For that price you can't do anything wrong either, for an OB experiment with subwoofer it's probably worth it.
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Maybe there could be copper sleeve/slug/coating.
There is another driver from Boston Acoustics and that has a copper sleeve. I do believe same driver used to be branded as Philips over a decade or two back. Rajdeep Electronics
Do note the mention of HI-Q
The mention of HI-Q in Sweton suggests a bit of copper inside.
One can be ripped apart to figure out or just ask the manufacturer.
thanks everyone for all the inputs !!!
HiQ is being used commonly in the market. I am not sure if this is a specific name used by a particular company in the beginning. My initial idea was to purchase a few Boston Acoustics HiQ drivers. They are basically out of production now!! But still many drivers are available in the local market with the name HiQ. We don't know which of them are nearly close to the original Boston Acoustics HiQ. Someone who used the HiQ drivers from Sweton company said the build quality etc are good. But from the specs i came to know this driver needs a huge enclosure. But thanks everyone for the suggestions !!!
I may try an OB !!
HiQ is being used commonly in the market. I am not sure if this is a specific name used by a particular company in the beginning. My initial idea was to purchase a few Boston Acoustics HiQ drivers. They are basically out of production now!! But still many drivers are available in the local market with the name HiQ. We don't know which of them are nearly close to the original Boston Acoustics HiQ. Someone who used the HiQ drivers from Sweton company said the build quality etc are good. But from the specs i came to know this driver needs a huge enclosure. But thanks everyone for the suggestions !!!
I may try an OB !!
I was actually looking for a simple bass reflex design ... may be we call it 4th order alignment technically
Philips stopped producing these FR drivers in the end of the 1980s, nobody wanted FR anymore. The most drivers after that were either off the shelves of other manufacturers or ordered after specifications. A lot if not most of the speaker companies do that to cover the lower price end even if they produce drivers themselves. The same for Boston, they buy the cheap ones. On the photo I've posted you can clearly see at the coating of the surround and also the gasket are done per hand, automated production does not have these tolerances. Boston started around 2000 with automated production, developed the machines and put them in factories in low paying countries for production. I'm very sure the Boston 8" FR came from Sweton.
Loudspeaker Manufacturers Make their Own Drivers? p2 | Audioholics
Well, HI-Q is no indicator at all because it's used by tons of speaker brands and meaning either high quality, ranked below HiFi or high Q-factor (Qts).
Anyway, I can't imagine they would use a copper cap because it needs surprisingly high precision production with very low tolerances (stamp/press) at a critical place (voice coil, pole core) and includes a lot more production parts, assembly lines and assembly time and logistics in the process and doubles (or more) the worktime per unit. Maybe I'm wrong but I did not find any mention of the copper cap being used either.
You don't have to rip one driver apart to check it, just measuring the impedance tells if a inductance control is in place. If there is no impedance control, the measurement above the fs resembles a kinda more or less long 'u'-shape, if one is in place, the lower part is mostly flat or rises slowly in a slight slope and starts to rise faster only at the upper end.
To compare drivers in this regard is often difficult because every company measures and (most important) scale the impedance plot vastly different from others.
Here two examples, I think everyone can now tell which is which
(Both measurements from Tang Band drivers but still very different scaling. Doesn't matter in this case because it just has to show the typical behaviour.)
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As I explained in my last post, the drivers are most likely identical and are from the same production line. From what I saw on the few photos I found, the build quality is ok-ish (coating smeared on the membrane is not a good build quality, no matter if it won't be audible), you'll have to expect and deal with tolerances. For the price it's definitely okay, you will probably not find many 8" FR driver for that price, let alone significantly tighter tolerances but you have to deal with what you'll get.
You're welcome!
FWIW, here's the HP calculator program it's from, which I used along with Altec's earlier, much more feature filled program than this basic one till getting a real computer in '96.
R.H. Small is the 'S' in T/S, so lends a bit of credibility to maybe this much later one being best overall
: G. Margolis and R. H. Small, "Personal Calculator Programs for Approximate Vented-Box and Closed-Box Loudspeaker System Design," J.Audio Eng. Soc., vol. 29, pp. 421-441 (1981 June); corrected on p. 824 (1981 Nov.).
GM
I may have a good suggestion. The Beyma 8 AGN is an affordable stiff fullranger with high fs and a qts of 1,15.
A very popular and simple horn was designed for it, the Viech (beast in German). If you google Beyma Viech you will find many photos of builds. I made it for a friend, quite amazing for the low price. It gives dry punchy bass up to 60hz or so.
Hence why not try making it with cheap panels? Is not difficult to make.
Important, the designer later removed the damping material at the back of the box and replaced it with a tight roll of damping materian just helow the driver, to filter out the high frequencies better. That is how i made it.
A very popular and simple horn was designed for it, the Viech (beast in German). If you google Beyma Viech you will find many photos of builds. I made it for a friend, quite amazing for the low price. It gives dry punchy bass up to 60hz or so.
Hence why not try making it with cheap panels? Is not difficult to make.
Important, the designer later removed the damping material at the back of the box and replaced it with a tight roll of damping materian just helow the driver, to filter out the high frequencies better. That is how i made it.
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