Bass reflex alignments explained – Step by step
What are the ported box alignments ?
The bass reflex alignments are like a description on how the box will sound like. A good analogy would be with the sealed boxes. If you haven’t read the article, I encourage you to do so, as it will make more sense. But I will briefly explain it anyway. To calculate the volume of a sealed box, you first need to make up your mind which Qtc you want. Qtc is a factor of Qes, Qms and the Q of the box. Since Qes and Qms are speaker qualities, and are fixed, only the Q of the box can be altered, by modifying the volume of the box. In a reverse fashion, by knowing which Qtc you want, and considering that Qes and Qms are given by the speaker manufacturer, you can calculate the volume of the box.
Sealed vs bass reflex alignments
Here are the sound characteristics corresponding to different values of Qtc for sealed boxes :
- Qtc = 0.5 : Perfect transients, but low efficiency.
- Qtc = 0.707 : This is the number most people try to reach for, as it gives good transients and flat response with minimum cutoff.
- 0.7 < Qtc < 1.2 : Better efficiency, somewhat degraded transients, steeper roll off.
- Qtc > 1.2 : High efficiency, bad transients, bad frequency response.
Since, the ported enclosure is more complex than the sealed box, it is not as easy as choosing a value of Qtc. Instead, there are several well known bass reflex alignments, from which you can choose from. I made the analogy with the sealed enclosure, because it is easier to understand, but for bass reflex, the process is much more complex. Making slight variations for Q in a sealed box, will result in a minor alteration of the response. However, for bass reflex, can cause notable increases or decreases in the bass region, which are referred to as “misalignments”. Ported boxes have much steeper roll-off, and if confronted with misalignment issues, can cause serious transient ringing.
So, to determine to volume of the box and the size of the vent, you first need to choose a certain alignment. Because different drivers have different parameters, and therefore different drawbacks, you need to choose an alignment that compliments your driver, so that you will get, more or less, a flat response.
Types of bass reflex alignments
There are two basic categories for bass reflex alignments, one of which extends into two other categories :
- Assisted.
- Unassisted.
- Flat.
- Non-flat.
Assisted alignments
involve an active electronic filter equalization, to achieve the desired response. This type of alignment is not particularly popular and we shall not focus on it. Instead, we shall concentrate our attention to the unassisted bass reflex alignments, which do not need extra electronic devices to achieve a predicted response. Because of this simpler design, it is more widespread.
Unassisted flat alignments
generally requires values of Qts lower than 0.4, and are divided into 6 categories :
- SBB4 or Super Forth-Order Boom Box – is characterized by a large box, low tuning frequency (longer vent) and good transient response (which puts the term boom-box out of place).
- SC4 or Forth-Order Sub-Chebyshev – about the same enclosure size and f3 as the SBB4, but with different tuning frequency. Somewhat degraded transients compared to SBB4.
- QB3 or Third-Order Quasi-Butterworth – is the most popular vented alignment, because it yields a smaller box and a lower f3. However, the transient response is not as good as SBB4 or SC4.
- B4 or Forth-Order Butterworth.
- BE4 or Forth-Order Bessel.
- IB4 or Butterworth Inter-Order.
The last three bass reflex alignments are called discrete alignments, because they exist for only one single value of Qts. These are quite difficult to obtain, because the box losses affects the value of the alignment. Out of the three discrete alignments, BE4 has the best transient response.
Unassisted non-flat alignments
are generated using a higher value for Qts. These bass reflex alignments tend to have an inferior transient response and frequency response. For this reason, they are not suited for high-end audio applications. However, if the negative parts are not an issue, the non-flat alignments can reach lower values of f3. These alignments are split into 3 categories :
- C4 or Forth-Order Chebyshev – can be useful for low values of ripple (less than 1 db).
- BB4 or Forth-Order Boom Box – has a peak in response close to roll-off, similar to high Qtc sealed boxes (1.2 or higher).
- SQB3 or Super Third-Order Quasi-Butterworth – is a high value Qts extension of the QB3 alignment.
Box losses
Before we explain the bass reflex alignments, we need to talk about box losses first. When you are manufacturing a box, you have to take into account that there will some air leakage, or other factors that will change the result. All of these factors combined describe the box losses. You will encounter three main types of losses :
- Air leakage – QL.
- Absorption from damping material – QA.
- Vent losses – QP.
Total losses (QB) is the sum of all 3, which add together in the following fashion :
1/QB = 1/QL + 1/QA + 1/QP
In a real world scenario, where the sound damping material would be absent, or 1″ of wall lining, QA would be minimal. Also, considering that the port is not obstructed, QP is negligible as well. So, when we are talking about box losses, we are talking about box leakage, which is QL. As a result, different amounts of QL, will affect the frequency response in a different way.
Adjusting box losses
When constructing a box, you will have to take account the box losses, or more to the point, the leakage (QL). So, before you start your build, consider that the box will have a normal amount of leakage, which is QL = 7. After you have completed the box, you will have to measure the box losses and see if the value is close to 7. If indeed QL is around 7, then you can congratulate yourself. Otherwise, you will have to take corrective measures.
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Discovering that QL is lower, means you will have to make the box bigger. This usually means that you will have to make the box all over again. If QL is higher, then you will have to make the box smaller. This is done pretty easy, by placing solid objects (rectangular pieces of wood) inside the box, to make the net volume lower. If you are afraid of the low QL result, you can over-volume the box, and after you measured the box losses, you can reduce the volume by the appropriate amount.
How to measure box losses?
You cannot predict how much losses you will have for a predefined enclosure. As a result, only after the box is complete, you can see how lossy it is. To measure the box losses, you will have to make some measurements for the speaker and the enclosure. After you get those values, there are several calculations that you will need to do. Since it is pretty difficult to write all of those formulas, I prefer to add an excel spreadsheet, where you input the needed values and QL is calculated for you.
Excel spreadsheet for calculating QL : Calculate QL
Explanation of terms inside the spreadsheet regarding the enclosure :
- fb – resonant frequency of the box.
- fH and fL – The impedance curve of the enclosure will show 2 peaks. Note the frequencies that correspond to those 2 peaks. fH represents the value for the bigger peak and fL the value for the smaller peak.
- R0 – the impedance at fb.
How to calculate box size using bass reflex alignments ?
First of all, get acquainted with this table in excel format : alignments table. Now follow these steps :
- Choose the alignment you would like, and go to the appropriate table.
- Then go to the QL = 7 column, since it’s the typical loss figure.
- Find out the Qts of your driver, by measuring it, or look for it in the tech sheet.
- If Qts is lower than 0.4, you will end up with a flat alignment. If it’s higher than 0.4, the alignment will be non-flat. You can also tell by the peak-dB or ripple-dB from the table (if it’s 0, it is flat). On the same row with your Qts value, you will have : H (tuning ratio) , α (the system compliance or box volume ration) , f3/fs (the f3 ratio).
- Find out the Vas and fs of your speaker, by either measuring it or by looking it up in the tech sheet.
- Calculate the volume of the box : Vb = Vas / α .
- Calculate the tuning frequency : fb = H * fs .
- If you want to calculate the f3, you can do that by taking the f3 ratio value from the table and multiplying it by fs. Calculate f3 = (f3/fs) * fs .
- Choose a diameter for the port. The bigger the better. Half of the diameter is the radius (R).
- Calculate the length of the port : Lv = [(14630000 * R2) / (fb2 * Vb)] – (1.463 * R) . Length and radius are in inches and volume in cubic inches.
Let’s do a real world example, for an 8″ woofer with the following specs :
Qts = 0.52 ; fs = 47 Hz ; Vas = 7.86 L
- Alignment chosen : SQB3 (since Qts has a high value, it’s a non-flat alignment).
- Looking in the middle column where QL = 7 .
- Qts = 0.52 .
- H = 0.8116 ; α = 0.1971 ; f3/fs = 0.6835 .
- fs = 47 Hz ; Vas = 7.86 L .
- Vb = 7.86 / 0.1971 = 39.88 L (2433.63 cubic inches) .
- fb = 0.8116 * 47 = 38.14 Hz .
- f3 = 0.6835 * 47 = 32.12 Hz .
- Choosing the diameter to be 4″. This means R = 2″
- Lv = [(14630000 * 4) / (1454.66 * 2433.63)] – (1.463 * 2) = (58520000 / 3540103.24) – 2.93 = 16.53 – 2.93 = 13.6″
So for our 8″ woofer we got :
- SQB3 alignment.
- Volume of the box 39.88 L .
- Tuning frequency 38.14 Hz .
- f3 = 32.12 Hz .
- Port diameter 4″ .
- Port length 13.6″ .
Conclusion
Similar to Qtc from sealed boxes, the bass reflex alignments work in a similar fashion. It’s like choosing your response curve before you even made the box. Unlike the closed enclosure, bass reflex has an additional element (the vent) and it’s not as simple as choosing a Qtc value. Driver Qts is an important variable in this equation and will determine whether the alignment will be flat or non-flat.
References
- Loudspeaker Design Cookbook 7th Edition by Vance Dickason (Audio Amateur Pubns, 2005). (Amazon affiliate link)
- Image source : link.
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69 comments
This is a great article thanks for the information, could you point out how you calculated the allignment table or point me to the source i want to develop a program using Octave also a source to calculate the assisted allignment table would be great. Anyways the excel spreadsheet is the great source
You can find the alignment table in the Loudspeaker design cookbook , which I highly recommend.
I can’t understanding this “Discovering that QL is lower, means you will have to make the box bigger. If QL is higher, then you will have to make the box smaller.”
Let me give you a practical example. I’m just using random numbers to make a point.
If you calculate the box for QL = 7 to be 20 L.
After you made the box, and measure QL and find out it’s 15, then the box is less leaky (more air tight). This means it doesn’t need to be as big. So to get the same response, as you calculated before, the box needs to be smaller (Let’s say 18 liters).
In conclusion a box with QL=7 and V=20L will have the same response as a box with QL=15 and V=18L. Again I’m just using random numbers to make a point.
A box which is less leaky has a smaller footprint than a box with normal losses, considering they achieve the same frequency response. The inverse is also true. If QL = 5 then the volume needs to be higher than 20L to achieve the same frequency response.
It’s not uncommon to make a box with QL of 15 if you use silicone sealant on the inside joints of the box.
Please point me to a article/link to “assisted” LF extension be it sealed or ported
I have ample power & PEQs. No knowledge source to tap into.
Thanks, tony
If you are talking about electronically assisted designs, you can go ahead and search on google for “Linkwitz transform circuit”. I’m sure you will find many articles to clear things up. Sadly, I haven’t wrote about this subject.
The LT circuit is for sealed boxes.
If you are interested in assisted bass reflex boxes, then you might want to check Speaker Builder 1/82 article by Dr. Bullock on sixth-order alignments. You might be lucky and find a pdf somewhere online. If not, you can buy Bullock’s book which contains this article.
Hi
It is great article!
My question can be a little weird but
If we put the port outside of the box,Can we use same alignment table??
I will use it For my calculation..
Thanks..
It doesn’t matter if you place it inside or outside the box. If you place it inside, you have to make the box bigger to compensate for the volume displaced by the port. Remember, these calculations will yield the net volume of the box. Then, you have to add everything you place inside the box (port, volume displaced by speaker, bracing, crossovers etc).
If you place the port on the outside, it’s basically the same thing. Only difference is that you don’t account the port for the overall volume of the box.
Thanks.
I want to be more specific with one more question:
I am trying to build supravox baffles compenses enclosure suitable with my Drivers..
And I need a confirmation..
Bass reflex enclosure compliance Cab=Vb/p*c^2.
Is this equation universal For all bass reflex??
Yes that equation holds true for all bass reflex enclosures.
Dear Marius Tanasescu,
I like reading this work, it demonstrates a very clear way of putting it down in words and equations. Thanks for making this available.
There is a thing puzzling me still, and I am not sure how to make this up from the written information:
Imagine one wants to make a small box volume, so smaller than “6. Calculate the volume of the box : Vb = Vas / α “. Can this be compensated for by altering the bass reflex port?
If yes, can the port length be calculated by using the smaller (desired) box volume in the equation “10. Calculate the length of the port : Lv = [(14630000 * R2) / (fb2 * Vb)] – (1.463 * R) .” Or must additional measures be taken for the calculation?
How far could this “limit” be pushed (if possible in the first place)? 10% less? 20%?
Any feedback welcome,
JvanderHoeven
You can calculate the port length using that formula, yes. Problem is that as you keep decreasing the volume of the box (Vb), the port will demand a very long length. And since the box is small, you don’t have any room to fit such a long port. If you want to make a small enclosure, sealed would be a better bet.
On August 16, 2017, you wrote “It doesn’t matter if you place it inside or outside the box.”
On January 7, 2018, you wrote “And since the box is small, you don’t have any room to fit such a long port.”
I understand that many people will roll their eyes at the very idea of a tube sticking out of a box (or cite WAF as trumping everything else in the universe, a peculiar view). But it seems to me that since everyone agrees that compact speakers should be placed on stands rather than on the floor that there need be no conflict–fully or partially external duct(s) can be “disguised” as part of the stand. Do you agree that what limits design here is the non-linearity of the air spring when compression is too large (5% is often used as a rule of thumb)?
That seems like a great idea with disguising the port into the stand. Never thought about that. I haven’t got any experience with really long ports, as I always try to fit them inside the box. But the biggest issues I see with long ports is dealing with organ pipe effects.
Hi Marius,
Great article, thanks for the information!
You had mentioned “Choose a diameter for the port. The bigger the better.” May I know why bigger is better? Thanks
Hello Bernard
Ideally a port should be as large as the speaker diameter, but that will translate into a very long length, and it’s not possible. As you go lower in diameter, you run into power compression issues and unwanted port noise (chuffing) at higher volumes. As a rule of thumb, go for a large diameter while the length remains reasonable.
I see.. thank you very much
Hi Marius,
Using the provide formula in this article, if I decided to use two ports in stead of one port (consider the area of the 2 ports opening is the same as one), should I use the same port length for both ports?
Thank you again.
Yes, you have to use that length for both ports. I know, it gets kinda difficult when choosing ports with larger area, but it’s the way to go, when possible.
Hi
I already asked but I want to ask again to. be sure.
Bass reflex enclosure compliance Cab=Vb/p*c^2.
Is this eq. also true if I use ‘funnel’ like shaped port?
I mean that is it true for ‘changing cross sectional area’ ports..
The compliance of the air inside the box is independent of the size and shape of the port. So, to answer your question specifically : yes, the equation is true for tapered ports.
Thank you very much..
Dear Marius Tanasescu,
Could you help me with the following: How should one use the formulas (how should one approach box design) in case two smaller woofers are preferred over using one larger one? By doing so one can make, for example, the box frontside less wide (resulting in a “slimmer” box). Such designs are rather common to my impression, using two woofers and one bass-reflex-pipe. How should the calculations be started? Just by doubling the Vas, or is it more complex/very different? Any suggestion welcome.
If the speakers are identical, resonant frequency and Qts remain the same. Like you said, you have to double the Vas value, and take your calculations from there.
I want to design and build a new box type I am not proficient with using the SBB4 alignment but have had no luck finding the specific design tables I require. In The Loudspeaker Design Cookbook there is a short section on Augmented passive radiators and the examples given use 2 other alignments, but not SBB4, how do I generate a design table for this alignment or do you know of any reference to them for Augmented passive radiator with SBB4 alignment?
I haven’t got into the augmented passive radiator that much, but I’m going to make an educated guess (take it with a grain of salt). SBB4 alignment is similar to the sealed enclosure, it has a high-ish F3 . Augmented PR’s have the advantage of having a lower cut-off frequency, compared to a classic passive radiator. For this reason, I think you can’t have APR and SBB4 in the same sentence. Didn’t do any due diligence on the matter and I might be wrong though.
Hi,
Do we also have to make the speaker box bigger to compensate for the volume occupied by sound damping material placed inside the box ? Like BAF wadding or wool filling or acoustic foam. It can be challenging to measure the actual air volume occupied by these type of material.
Thank you.
No, you don’t add up the damping material. The density is too low to be taken into consideration.
Hello, this is a very informative article, but I could not find this information.
How are you calculating FH and FL?
Are you using a termlab style sensor?
Are you just checking impedence rise peaks throughout a frequency sweep?
No. These are alignments. Like pre-calculated frequency curves. You can find the numbers in Dickason’s book (see references at the end of the article).
Hello, Marius, I speak from Brazil. Great article! One question: Passive radiator box use inner lining? (blanket / glass wool etc.) If yes, in what quantity? Thanks for any response and sorry for my English. Hugs
Sound dampening material is mostly use for sealed boxes, but it’s not uncommon to see it in bass reflex or passive radiator boxes. If you don’t have any panel resonances or other box problems, I would just leave the box as is. But if you want to use a small quantity to line the walls, it’s up to you.
Hello!
On a certain site (micka.de) there is an calculator that uses Bullock alignment for pasive speaker enclosure. Results are almost the same as QB3 alignment..
Just want to ask how close the rear end of the BR tube (D=5.7 cm) can be close to the surface (inside the box i mean)? Is 4 or 5 cm o.k. ?
Thanks.
As a rule of thumb, the distance between the rear of the port and nearest boundary should be at least the diameter of the port. So if your port is 5.7 cm. The distance should be at least 6 cm
Hi ! A local manufacturer told me that speaker (in BR box) allways “see” a tube litle bit longer than it in reality is (as calculated) becouse air in near front (and end) of the tube vibrates together with the air inside the tube and that is the reason. Do You know somenthing about it?
Tnx!
Well it depends on the shape of the port. If it’s straight or flared. And if it’s flared what is the radius of the flare etc. The formula which calculates the length of the port has a correction factor at the end of the equation, which is different depending on the shape of the port. But the size difference (between real and calculated) is not something significant and it’s not something to worry about.
Hi Marius,
thanks a lot for this so informative article!
I want to build a sub for my Hi-Fi system and i’m using a Dayton reference 15″ RSS390HF-4 tuned to an SBB4 alignment. For an aesthetic reason i’ve chosen to use two reflex ports (3.5 inch each in diameter) instead of one (6 inch in diameter, which will lead to a length of 25.24 inch, a bit too much for the box).
How long those ports should be? How can I compute them? Many thanks in advance!
I actually did the number crunching for you.
The box needs to be 178 liters tuned to 19.5 Hz
This means that the port needs to be :
6″ -> 27.32″ long
2 x 3.5″ -> 19.17″ each
If the port is producing all the sound at the tuned frequency and the speaker cone isn’t moving , how is it possible that there is any sound at all ?
The majority of the energy is produced by the port at the resonance frequency. The speaker still moves, but the excursion is just a little.
Hi Sir,
Thanks for this very detailed and valuable information which is very difficult to find elsewhere.
I am planning to build a bass-reflex box for a 10 inch subwoofer. Vital T/S parameter are provided by the vendor. Qtc=0.39, Vas=48.6L, fs=29Hz. (AudioLabs from China: model DL100TZB-01), Don’t know if these values are accurate.
You mentioned here that misalignments can cause major problems. Does that mean Qtc value should be accurate within 0.01? What happens if the actual Qtc is 0.40 or 0.38. After bulding the box, does it result in any serious distortion in any frequencies? Likewise for any error in value of Vas or fs what are the after effects?
Also, is it serious problem, if the built volume of the box is a little different than calculated, say by half a litre.
Thanks
Hello,
Thanks for this useful article!
I am building a subwoofer in bass reflex design. I have a 10 inch driver with Qts=0.39, fs=29Hz, Vas=46.8L. But I am no sure, if these parameters are accurate. If the actual Qts value is different by say, 0.01 (0.40 or 0.38), how does this affect the sound ouput in a negative way? Likewise for any error in fs or Vas, what is the after effects on ouput? Will there be any distortion in any frequencies? How much error can be tolerated in such cases?
Thanks.
People take these things way to seriously. You won’t even notice these slight changes. In term of Qtc, depending on what you try to achieve, a value between 0.5 and 1 is acceptable. If you start to exceed 1 then they start to sound progressively bad. Also a variance of a few liters is mainly nothing (depending an your OCD 🙂 )
Thanks! But, you mentioned:
” Making slight variations for Q in a sealed box, will result in a minor alteration of the response. However, for bass reflex, can cause notable increases or decreases in the bass region, which are referred to as “misalignments”. Ported boxes have much steeper roll-off, and if confronted with misalignment issues, can cause serious transient ringing. ”
Does this mean I need to have the accurate value of driver’s Qtc for the calculations?
When you are talking about the speaker you are referring to Qts. And yes, you do need an accurate Qts value to determine a box correctly. However, if the Qts is 0.35 and you designing a box using Qts of 0.37 is not the end of the world. The box will still sound decent. Plus, there are variances between speaker batches. There are a lot of things which can influence the result. However, if you following the general guidelines for building a box, and not stress about all the minute details, you should be good most of the time.
Hello,
A great article thanks, a helpful summary.
One question.
Which of the reflex alignments is closest to being similar to a critically damped sealed box alignment? Q=0.5?
i.e. Are there any other reflex alignments that are critically damped?
Is there a way to calculate or model other alignments which are critically damped?
Thanks
Gilbert
Yes. It’s the SBB4 alignment.
Markus,
Thanks for the super quick response!! 🙂
Confirms my initial thoughts from the descriptions above, just wanted to be sure
KR
Gilbert
Great article!
Actually, I want to apply the reflex port to small speakers that is over 1.5 Qts..;
However, The bass reflex alignments table you are attached in this aticle is just for 0.7Qts.
Could you send me an extended Qts table or let me know equations to calculate this table more? Thanks!
These are bass reflex alignments (with specific frequency response characteristics) and are possible only until a specific a Qts value. If the Qts value is not in the table, you have to use a box modeling software and get your custom frequency response curve. However, since you have such high Qts, a large sealed box or an open baffle would be more suitable.
i have series of doubts
actually we are design a box that gives a response spl vs frequency in software or calculating myself
1) what if subwoofer has for example Fs 20 hz and all ts parameters any way and we calculate in software the response in graph that gives freq vs spl chart but my question is manufacture provide spl vs freq for infinite baffle it looks from 20 to 80 hz it increase from 40 dB to 90dB now if i putsub in that calculated box what is the freq vs spl graph because we are not loading frd file previously
2) does it give response irrespective frd respone of what manufacture is provided or it gives response frd graph but below the tune freq it going to subtracted from -db value to frd spl db value
help me please
because in your seal box project ,you are not considerd frd files then how can you say what actual output of subwoofer once you make subwoofer box finally .
forgot about room gain, response because i need actual subwoofer output like anechoic because every sub has differnt spl graph then how they perform same / what software tells is same for all different subs but response grap is different
hope you understand my doubt
ok u didn’t understand what i have writen just above , may be i didnt convey in easy way
let me say in another way
for subwoofer what u calculated is by giving ts values and it gives graph just like above graph but what about spl chart(frd) given by manufacturer of course it is measured in half space
it has different spl values at different frequency values
1) then how actual response look like ? once we apply 2.83v signal(20Hz-200HZ)
2) any scaling or relation between box response and frd values of subwoofer below the tuning frequency ?
reply my doubt
If you want the actual response, you will have to measure it with a microphone, you can’t model the frequency response of speaker just by using the T/S parameters. The box, however, will have a significant impact on the low frequencies and the part just before roll-off and the actual roll-off can be modeled. That’s why when you use box modeling software the response from roll-off and upwards is a flat line. It assume an ideal situation where the speaker plays perfectly linear. In reality you should look only at the response when it starts to roll off. To get an idea how low the speaker will play in that particular box.
How do I account for the volume of the box and port dimensions of two different speakers in the same housing? Do I use this process separately for each speaker then add the volume and port dimensions to get the final values?
Thank you
Yes, you are calculating the net volume of the box. After that, you have to add everything that takes spaces inside. Like the volume displaced by the speakers, port, braces etc. The resulting volume is the box you need to build.
To reduce the Mach# at the port is desirable, and it is an objective to get port area nearly equal to driver area. In so doing the duct lengths get excessive. I would guess that extended duct length adds up to attenuation that defeats the advantage of port area. Is this true? If so, how to go about determining a trade-off between the two dimensions?
Well, you try to stay as much as possible below 30 m/s air velocity. This comes natural because if the air velocity is too low, which is a good thing, the port will be impossibly long, and you can fit it inside the box. If you do manage to fit a very long port, you might end up with pipe organ effects, but most of the time it’s not possible in the first place.
Dear Marius,
when calculating Vb, one should subtract the volume of driver , crossover, wall reinforcement stuctures, port, etc…. inside the enclosure. It is not clare for me, if port will be round shape, whether the whole volume (which port occupies, thus – Pi x r*2 x h) of the port or just the wall thickness of the port pipe must be subtracted?
Thanks!
The calculate the gross volume, you have to add (not subtract) to Vb the volume displaced by anything inside the box. Regarding the port, you add the volume of the whole cylinder (not just the walls).
Thanks a lot for comments. Hope you can find time for another one. I have two Pioneer TS-W304R subs, 300W RMS and amp 250W. Subs are lower end items in price scale, but want to squeeze the best out of them . As Vas is 77,88l and Qts 0,7 – bass reflex alignment table gives C4 or BB4 a=0,4 and 0,2 which leads to Vb 200 and 400l or in other words infinite baffle. However, manufacturer recommends enclosure mounting from 24 to 56 l depending on type. Difficult to decide, where would be most reasonable starting point. Basically, I can yield max 80l per sub enclosure in a car if this helps. As low Fb as possible is preferred. Thanks again!
0.7 Qts is basically for infinite baffle. So, if you can mount them on the rear parcel shelf of your car with the magnet sticking inside the trunk, that would be best.
Hi, I downloaded your QL spreadsheet and got a negative result, i.e. -2.56, what does this mean?
Thanks in advance Mike.
I’m guessing that you mismatched some values in the spreadsheet. Can you tell me the exact values you input?
Hi Marius,
fs 45
Qms 2.47
Qes 0.61
Qts 0.492
Re 7.1
R0 5.03
fL 24.3
fH 98.4
fB 53.48
These figures come from Loudspeaker Enclosure Design Workbook.xls by Geoff Swan. Regards, Mike.
Hi, if i use Neville Thiele’s figures from his paper, I get 0.4609:
fs 55
Qms 6.67
Qes 0.833
Qts 0.741
Re 4
R0 9
fL 30
fH 100
fB 60
How does one interpret this?
Cheers, Mike
The interpretation is that 7 is normal losses. Lower than that is high losses. Higher than 7 is low losses. You get a negative number because your R0 < Re which shouldn't be the case. Check your measurements. Make sure you measure your speaker and not use spec sheet data.
Hi Marius, thanks for the speedy replies, is the answer 0.7 or 7.0. Do you perhaps have some sample figures I can try?
Regards, Mike.
7 Is normal losses. 3-7 more than average losses. Less than 3 (including 0.7) is high losses. Very leaky box and you should consider making another or fixing it. 7-100 very good box, air tight. 100+ virtually no leakage.
Okay, thanks.
Regards, Mike.