Hi And thanks for reading this post.
I realise from reading this forum's posts that loudspeaker design is complicated and one cannot just shove a drive unit into a box and get good results.
I have bass box pro and win isd software programs, within which you enter the drive units thiele-small parameters and it gives you the enclosure dimensions and port sizes.
But winisd and bass box pro are giving me very much different results for the same drivers, also there are a few websites which do the same thing for free, but the websites are also giving me different results.
What should i do, who should i trust? Or is this a bad way to approach cabinet design altogether. Are there any other programs i should try/or not try.
Any advice would be appreciated. Thanks.
I realise from reading this forum's posts that loudspeaker design is complicated and one cannot just shove a drive unit into a box and get good results.
I have bass box pro and win isd software programs, within which you enter the drive units thiele-small parameters and it gives you the enclosure dimensions and port sizes.
But winisd and bass box pro are giving me very much different results for the same drivers, also there are a few websites which do the same thing for free, but the websites are also giving me different results.
What should i do, who should i trust? Or is this a bad way to approach cabinet design altogether. Are there any other programs i should try/or not try.
Any advice would be appreciated. Thanks.
The problem is that there isn't only one optimal box for a specific driver. In fact the whole concept of optimal is flawed. Some drivers are optimized to work in a closed box, some others work better in a reflex box, other are specifically designed to work in a horn, but there isn't a magic box for each driver, just a range and you should choose the box also depending on the environment.
Just to give an example for a reflex box, many if not all the calculators will give you the enclosure and tuning frequency that will give the lowest F3 point. Unfortunately F3 (*) has no special meaning for our hearing, it is better to concentrate to point like F6 and/or F10. Designing a box for F3 only and forgetting the room interaction will likely result in a peaking bass response. I usually tune my bass drivers lower than the "optimal" value and try to obtain a shallower response.
Speaking of the programs you mentioned, I only used WinISD, but I prefer Unibox to it for many reasons. Unibox is free.
(*) F3 is the frequency in which the SPL is down 3dB from the flat.
Ralf
You are concentrating only on the enclosure part of the speaker design. Just to warn you that unless you are building a subwoofer, you'll have also other problems.
Just to give an example for a reflex box, many if not all the calculators will give you the enclosure and tuning frequency that will give the lowest F3 point. Unfortunately F3 (*) has no special meaning for our hearing, it is better to concentrate to point like F6 and/or F10. Designing a box for F3 only and forgetting the room interaction will likely result in a peaking bass response. I usually tune my bass drivers lower than the "optimal" value and try to obtain a shallower response.
Speaking of the programs you mentioned, I only used WinISD, but I prefer Unibox to it for many reasons. Unibox is free.
(*) F3 is the frequency in which the SPL is down 3dB from the flat.
Ralf
You are concentrating only on the enclosure part of the speaker design. Just to warn you that unless you are building a subwoofer, you'll have also other problems.
Loudspeaker enclosure design is fairly complex. There are a lot of assumptions and tradeoffs to be made. Different software make different assumptions and come up with different results. Probably none of them are really wrong (or right) they just come up with different default assumptions and you are not aware of what they are. This is almost always the problem when people use something that is essentially a black box to them.
I know a fair amount about box models, I've coded several of my own (one I did back in 1998 is much like Unibox) and I feel there is very little difference between most box modelers once you know how they work. The trouble with models that have more settings is knowing what those settings should be set to.
For a sealed box, the main way to affect response shape is box volume. Secondary to that is damping and leakage. Lower volume gets you a higher Qtc. Adding absorptive damping material or leakage lowers Qtc. A good value to start out trying for (to find a suitable box size) is Qtc=0.7 and the useful range can vary from 0.5 and 1. One piece of software may give a default volume with Qtc=0.7 and minimal damping and one may default 0.9 and lots of damping - that can be a significant difference in volume
For a vented box you have two more parameters to play with. You can vary volume and tuning frequency, and also there are more damping terms, for absorption, leakage and port damping. There are many ways of deciding box volume and tuning for a vented box - the software programs may use different ways. They may all be correct.
The damping material models in most all software are simple resistive models and they aren't that much closer to reality than when damping is ignored, IMO. The undamped model gets you 95% of the way there and the damping models might add a percent if you use them correctly, but not if you don't know what the settings are, or should be..
If you post a driver T/S parameters and the different box sizes/tuning frequencies you get with the various software, I can perhaps help you to understand the differences.
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It does get complicated with vented cabinets, horns and multiple drivers.
I saved myself a lot of grief by just using sealed cabinets with full range drivers. No crossovers, no xmax problems etc etc
I just threw a couple of Fane 12-50WRMS in a sealed cabinet and it worked great, very loud.
I have to admit more recently I got into Fane folded horn cabinets.
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What many here have avoided saying thus far is that there are always competing tradeoffs in performance, only in different competing performance areas that must be traded more or less simultaneously. You're making a few of those trades using the output response plots to indicate the resulting performance. You're controlling the big hitter input parameters--the woofer used with its T/S parameters, the box volume and relative shape, the port length and diameter, how much acoustic absorption material use inside the box--that will largely determine the resulting sound of the bass bins. You still have to decide the placement of the resulting loudspeakers in your listening space which will affect the low frequency performance as much as the parameters do above. It isn't a "one size fits all" problem, unfortunately.
Within--for instance--WinISD, you have choices for drivers, box size, and port tuning frequency. Then you have the response shown in the plot, presented in gain (relative acoustic power output), its phase/frequency, and group delay/frequency.
If it were me, I'd look not only at the frequency response, but also of the phase and group delay. The lower the group delay (in milliseconds) vs. frequency, generally the better the sound without the flabby sound of "ported boxes", which has been shown to be audible. Group delay is the derivative of the phase curve, i.e., the plot of the instantaneous slope of the phase curve. The phase growth at lower frequencies will also be smaller (a good thing) if the group delay is smaller. If you play around with the input parameters, you will see that the group delay, phase and gain curves also move around. Your job is to pick one configuration that appears to be within your choices of input parameters and the resulting output performance, measured in at least three ways: relative gain, phase and group delay.
Usually, there is a sweet spot of "F3", port tuning frequency, and minimized resulting group delay that is preferred by the person doing the trades. This design configuration chosen won't occur necessarily at one optimal point (assuming the driver chosen is held constant), but will usually be a range of driver/box/port/stuffing configurations that you can choose from. This is subject that was mentioned above in terms of "optimal", which for many people is assumed to be a single design configuration or design point. Optimal here means "according to your multi-dimensional trade parameters chosen", and can be a range of values that are very close in terms of input parameters and response. It's not a point-optimized design problem, unfortunately.
If it were me, I'd pick one software application and stay with it rather than switching back and forth between applications. All of them are going to be fairly close in terms of their predictions--probably within your ability to create the product with the parameters shown in the application. Also note that the room position/room loading will significantly affect the overall response--by more than an octave of performance, depending on where you put them in your listening room. Once you've got a design that you're willing to try, then you can check with another software application to make sure that the predicted response doesn't vary too much.
Chris
Hi. Thanks for the replies.
Sorry should have stated earlier, i have an active sub for handling everything up to 120hz, so the speakers i am trying to make are more satellites consisting of small drivers for midrange and a one inch tweeter.
What software do you use for desigining enclosures, winisd and bass box pro seem to be favourites on the net, with leap for advanced users, do you have a favourite?
Finally what do you think of the golden ratio 0.6 : 1 : 1.6 enclosure dimensions. I spoke with a local speaker manufacturer and their technical guy said that drivers work well in an enclosure similar to their vas compliance specification. In that a driver with a vas of one cubic foot will work well in a enclosure with an internal volume of approximatly one cubic foot. A driver with a vas of three cubic feet will work well in an enclosure of approximatly three cubic feet. What do you think?
Sorry should have stated earlier, i have an active sub for handling everything up to 120hz, so the speakers i am trying to make are more satellites consisting of small drivers for midrange and a one inch tweeter.
What software do you use for desigining enclosures, winisd and bass box pro seem to be favourites on the net, with leap for advanced users, do you have a favourite?
Finally what do you think of the golden ratio 0.6 : 1 : 1.6 enclosure dimensions. I spoke with a local speaker manufacturer and their technical guy said that drivers work well in an enclosure similar to their vas compliance specification. In that a driver with a vas of one cubic foot will work well in a enclosure with an internal volume of approximatly one cubic foot. A driver with a vas of three cubic feet will work well in an enclosure of approximatly three cubic feet. What do you think?
I think that if I can damp the rear energy with stuffing then it matters little. I think that if I use an enclosure with a particularly long dimension (pipe-like) then it may not be as easy.
For a satellite enclosure perhaps, but the commonly recognised middle-ground would probably be 1/3 Vas. For a satellite you might be interested in a more flat impedance, less interested in the low end response, and more interested in a gradual transition. You certainly don't need these but they could come in handy.
That's only true IF Qts is around 0.36 AND you are building a vented enclosure. Or if you are building a closed box with (very) high Qts.
Your active sub provides also a high pass filter for the satellites? If not you probably have to provide the equivalent with the slope of a closed box.
Anyway, what's the driver you want to use?
Ralf
I honestly do not know what drivers i am going to use for the satellites, was hoping for some clues. I have a few drivers lying around but am unsure as to thiele small parameters, perhaps good for experimenting with.
The amp i have is the arcam avr 800 (£4k), with a hp laptop as a source (£1.5k), and polk audio sub (£1k) This is all i have so far. Would be willing to spend approximatly £100 per driver. Also, have a few b&c tweeters which are good quality.
The amp i have is the arcam avr 800 (£4k), with a hp laptop as a source (£1.5k), and polk audio sub (£1k) This is all i have so far. Would be willing to spend approximatly £100 per driver. Also, have a few b&c tweeters which are good quality.
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It doesn't matter which you use. The difference between them is generally within tolerance of specs and often even within the tolerance of the T/S model itself.
If has no utility in box dimensions, perhaps marginally useful in locating a tweeter to get spread diffraction, but even then not "magic".
Truthfully? Sounds like the guy wanted to get off the phone with you by giving a plausible-sounding answer
I've been designing loudspeakers for almost 50 years. I no longer even look at Thiele-Small parameters or do box calculations - it's just not very important. Once you put the speakers in a room, the room will dominate the situation making all those complex calculations that you did meaningless. You have to correct the room, not design the speakers. Just put the woofers in a closed box of solid but well damped construction and throw out all those simulations. Place the speakers in the room, add a couple more closed box subs and find the right EQ for your particular situation (the techniques are well documented by moi.)
Then move on to what really matters - everything above the woofer region. You think woofer design gets complex, try working out a CD system crossover.
Then move on to what really matters - everything above the woofer region. You think woofer design gets complex, try working out a CD system crossover.
For the last 2 weeks I've been trying out various box volumes, sealed and ported with a few different woofers. Using winisd, measuring and listening etc.
In main listening room this is what I'll be doing! -
"Just put the woofers in a closed box of solid but well damped construction and throw out all those simulations. Place the speakers in the room, add a couple more closed box subs and find the right EQ"
In main listening room this is what I'll be doing! -
"Just put the woofers in a closed box of solid but well damped construction and throw out all those simulations. Place the speakers in the room, add a couple more closed box subs and find the right EQ"
I tend to agree that a given low end response rolloff may not work well, but when there is augmentation it can come together. Eg a tweeter crossover can sound wrong without the mid also playing but becomes irrelevant once it is.
I have also found that the absolute response of a box on its own is 'overrated' when part of the bigger picture.
I have also found that the absolute response of a box on its own is 'overrated' when part of the bigger picture.
Thanks!
I have the b&c de35 twts, i searched before purchase and they are well liked. I paid £100 each, just a few weeks later the price dropped to £50.
I do have to agree about the room , i used to have a rectangular living room in my old house and the sound was brilliant, now i've moved and the room is more square like, all my lovely sound quality has mysterly disappeared, i do think however enclosure consideration may bring some of that sound quality back.
What do you think may be good to dampen the enclosure walls and kill some of that back radiation and standing waves. I thought bitumen pads, are they ok, what do you use? Do you have to buy fancy esoteric stuff, or will cheaper alternatives do.
I have the b&c de35 twts, i searched before purchase and they are well liked. I paid £100 each, just a few weeks later the price dropped to £50.
I do have to agree about the room , i used to have a rectangular living room in my old house and the sound was brilliant, now i've moved and the room is more square like, all my lovely sound quality has mysterly disappeared, i do think however enclosure consideration may bring some of that sound quality back.
What do you think may be good to dampen the enclosure walls and kill some of that back radiation and standing waves. I thought bitumen pads, are they ok, what do you use? Do you have to buy fancy esoteric stuff, or will cheaper alternatives do.
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Those are not hifi tweeters - of course you will need sound deadening treatment, but outside!
I had the same experience - I bought a pair of DE 5 and soon the price halved.
Just for trying the (in) famous high efficiency, since I got a pair of 15 " and a midrange was to come. Still it is an unfinished system, 'coz it can't be fitted in a room ( and it needs subs )
I had the same experience - I bought a pair of DE 5 and soon the price halved.
Just for trying the (in) famous high efficiency, since I got a pair of 15 " and a midrange was to come. Still it is an unfinished system, 'coz it can't be fitted in a room ( and it needs subs )
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