Yeah, finally got a chance to look at the driver's specs and it would take a ~80 L cab and a big 'hit' on what little efficiency it has to go low without some solid corners to load them. Note too that the cabs must be tuned to at least the lowest frequency desired, so if tuned to ~50 Hz as the 25 L implies, then a solid 42 Hz low E most 'FR' designs shoot for isn't going to happen; plus, as a general rule it's not wise to tune a reflex < ~ 0.7x Fs, making even 42 Hz tough for this little driver if not used in multiples or horn loaded.
One ohm shouldn't do much unless the specs are pretty far off published, so get a couple of cheap 25 ohm pots at RadioShack or similar to dial in what sounds best and don't be surprised if the settings are different due to room loading variables. If you find some settings you like, then measure their resistance and replace them with non-inductive wire wound power resistors.
GM
I'll always 'run against the grain' on this since to my way of thinking if the manufacturer wanted it to sound like it does after such a long period they would have designed it that way.
Nope, music is AC.
WRT to 'matching' in general, I've never had much luck with matched speakers in folk's rooms, usually requiring different cab tunings also, but then either the room's and/or speaker's size always dictated locations near walls/corners. The ones with one speaker in a corner and the other next to a doorway basically meant two very different speaker alignments and no easy way to passively make them sound the same. Digital is good for some problems and this is one of them.
GM
The cabinet is tuned to 46hz (25L + 2 1.5"x4" ports) unless damping has altered the tuning. According to Talaerts, Hobby Hifi reported that a 25L cabinet with about this same tuning plus a 1ohm resistor yielded a 39hz f3. This of course might not have been the case but it certainly influenced my design. If what you're saying is true then I'm probably not going to do much better than 45hz or so, although I am corner loading the speakers. But I think that's alright; even now I'm getting just about all the bass I need. Maybe my next project will be a small sub to get those last few hz, but I doubt I'll ever go so far. I like the fact that I'm getting close to full range sound with no electronic components (unless I add that resistor) and no need for EQ. In the end, that's the point isn't it?
According to Talaerts, Hobby Hifi reported that a 25L cabinet with about this same tuning plus a 1ohm resistor yielded a 39hz f3.
I like the fact that I'm getting close to full range sound with no electronic components (unless I add that resistor) and no need for EQ. In the end, that's the point isn't it?
OK, again though for future fine tuning/design reference, best to follow good reflex design practice. I mean, any output below Fb is just rapidly increasing distortion with decreasing frequency. If tuned low enough, then it's not an issue due to our poor hearing acuity down low, but for many folks this threshold begins around 35 Hz and some even lower, so this tuning would be too high for low enough distortion at ~40 Hz, especially once a pair of corners has amplified/transmogrified it and no doubt why some folks can't tolerate either reflex and/or corner loading at all.
Way too narrow a performance focus for me, but a truism of biblical proportions for this forum
. GM
Greets!
Agreed, whatever it takes to get the system as tonally flat as practical over the desired BW, though I'm surprised you didn't need a by-pass capacitor to allow the extreme highs through; or do you use super-tweeters?
GM
Hm. I guess the problem with being a beginner is not knowing all the fundamentals to "good reflex design practice." While I understood that distortion increased below Fb, I didn't realize how quick the increase is, or not to expect usable bass below tuning at ALL. Well, I can't expect to get everything right with my first speaker.
One question that's always nagged me: I know that stuffing increases the effective volume of the cabinet with respect to the driver, at least in sealed enclosures. If the same is true with BR cabinets, does stuffing then alter the effective tuning of the ports as well? a 30L cabinet with the same ports would yield a 42hz tuning.
Excuse my ignorance once again, but what is the effect of a 10 or 22ohm resistor on efficiency, if any? I assumed that each ohm lowered efficiency by 1db but apparently not.
One question that's always nagged me: I know that stuffing increases the effective volume of the cabinet with respect to the driver, at least in sealed enclosures. If the same is true with BR cabinets, does stuffing then alter the effective tuning of the ports as well? a 30L cabinet with the same ports would yield a 42hz tuning.
Excuse my ignorance once again, but what is the effect of a 10 or 22ohm resistor on efficiency, if any? I assumed that each ohm lowered efficiency by 1db but apparently not.
Understood and why I 'spelled out' some major ones for you in my first two responses. Play with WinISD Pro to see how tuning affects a reflex's [vented alignment, be it a simple hole in the baffle or ducted port] group delay. Ditto adding series resistance and especially when adding damping [changing Ql, Qa, Qp].
Correct: Sub Box Polyester Fiberfill
Changing the system's effective Rdc changes Qes [effective motor strength], ergo Qts [electrical+mechanical quality factors], what T/S requires to calculate sims from. For quick reference, doubling Rdc doubles Qes, lowering efficiency ~3 dB:
Qes' = Qes*(1+Rs/Rdc), where Rs is the series resistance and Rdc is the driver's DC resistance, so:
Rs = (Qes'/Qes-1)*Rdc. Remember to include the series resistances of your amplifier/cable/inductors in Rs, so the actual resistor you buy may be somewhat smaller than calculated value. Or do as I do and just use a pot to dial in the sound, then measure it for the fixed resistor value.
Qts' = Qes' *Qms/(Qes'+Qms)
Vas is unchanged
n0 = 9.614*10^-10*Fs^3*Vas(liters)/Qes'
SPL = 112.02+10*Log(n0)
GM
Correct: Sub Box Polyester Fiberfill
Changing the system's effective Rdc changes Qes [effective motor strength], ergo Qts [electrical+mechanical quality factors], what T/S requires to calculate sims from. For quick reference, doubling Rdc doubles Qes, lowering efficiency ~3 dB:
Qes' = Qes*(1+Rs/Rdc), where Rs is the series resistance and Rdc is the driver's DC resistance, so:
Rs = (Qes'/Qes-1)*Rdc. Remember to include the series resistances of your amplifier/cable/inductors in Rs, so the actual resistor you buy may be somewhat smaller than calculated value. Or do as I do and just use a pot to dial in the sound, then measure it for the fixed resistor value.
Qts' = Qes' *Qms/(Qes'+Qms)
Vas is unchanged
n0 = 9.614*10^-10*Fs^3*Vas(liters)/Qes'
SPL = 112.02+10*Log(n0)
GM
Thanks GM for bringing the science. I must admit I am somewhat frightened of equations, which is why I've had trouble poring over the white papers on your site (although I find the results incredibly interesting). Am I correct to assume that altering group delay will result in nulls in output, similar to unstuffed TLs?
I'm trying to get winISD pro to work on my fiance's computer but it's getting hung up on some problems with the TS parameters I'm putting in.
I'm trying to get winISD pro to work on my fiance's computer but it's getting hung up on some problems with the TS parameters I'm putting in.
The HELP files pretty well defines what each is and what it affects, so please elaborate:
Under "advanced->", you can find controls for box losses. There, you can see what effect the each loss type will have on your box design (Smaller the value, greater the loss). There are three types of losses:
Ql, leakage losses. These are produced by leaks in enclosure or in driver itself. Generally, this is most dominant loss type in vented boxes. Typical value is 5-20. This is quite impossible to predict before building the actual box. For reasonable quality box, WinISD pro uses Ql of 10 by default.
Qa, absorption losses. These are produced by losses in enclosure. Any stuffing will increase the absorption loss. With no stuffing inside the box, 100 is typical. Heavily stuffed enclosure has this about 3-5.
Qp, port losses. These are produced by port. Port has some resistance (air doesn't actually flow through the port without some friction). Actually, by setting this into very small value, you can turn vented box into closed one!
GM
You're welcome! You and me both, but Ron E, another forum member, has a way with 'dumbing it down' to a great extent.
I don't have a website nor have I published any white papers, so which site are you referring to?
No, it will result in lower Q roll off slopes, hence lower distortion and usually better integration with the room's acoustics.
Nulls in TLs are a function of pipe harmonics: Resonances of open air columns
The HELP file is pretty complete, but some folks have had problems anyway, so have written up some additional help: WinISD Pro Tutorial and Download (A detailed guide on how to use WinISD Pro) - Home Theater Forum and Systems - HomeTheaterShack.com
More good info: DIY Subwoofers - General Discussion at Home Theater Forum and Systems - HomeTheaterShack.com
GM
I'm sorry GM, with all those equations you were throwing at me I got you confused with MJK! 
After going over quarter-wave.com, I just associate MJK with equations now. Anyway, thanks again for your help. The help button on my WInISD alpha doesn't work and after searching for answers to the Q thing I came up with nothing. Even with your explanation it still seems very hypothetical to me, but at least I know what values are realistic.
After going over quarter-wave.com, I just associate MJK with equations now. Anyway, thanks again for your help. The help button on my WInISD alpha doesn't work and after searching for answers to the Q thing I came up with nothing. Even with your explanation it still seems very hypothetical to me, but at least I know what values are realistic.
You're welcome! No problem, A good one to be confused with!
Yes, lots of good info and his math skills are light years beyond mine.
Hmm, seems like someone else posted having this problem. Wonder why, he asks rhetorically............
Correct, without knowing the physical properties of the material used in WinISD, no way to correlate it to a specific stuffing density, but each does show how any qualified damping material can affect performance, just not how much is required, so must be adjusted empirically by ear or the appropriate measurement.
GM
I thought some people might like to know how these speakers are getting on after a few weeks. First off, I have not opened them up since stuffing them with the 1/2lb acousta-stuf per speaker. This really did the trick of bringing out the bass, and I've not had any desire to tinker with the internal goings-on since. By my estimation the internal volume is now approximately 28.5L and the tuning is approximately 42hz. Right now both speakers are placed just about against the backwall, toed in about 5 degrees, and driver center is 37" from side wall. Occasionally I prop up the front a few degrees also.
Last night one of my students came over for a lesson. As he is also an audiophile so I asked him to bring some of good evaluation CDs and stay for a listening session. His speakers at home are Avalon Acoustics something-somethings. Anyway, after an hour or so we came to some mutual observations.
The bass from these speakers, while deep, is not convincing. In other words you will hear it but never feel it, robbing you of the tactile experience. But that was to be expected. With a 5" driver, just to have the bass there is all I had hoped for. (My next speaker will utilize larger drivers, perhaps even something along the lines of a bi-amped Beta 12LTA and alpha 15 OB. But this will have to wait until I have the space.)
We also agreed that imaging is quite good with these speakers. My friend bought his avalons on the basis of their soundstage capabilities, so for him this is the critical thing. We experimented a little bit with bringing the speakers away from the rear wall but didn't experience a major change in imaging. Given the addage that 'the thinner the baffle, the better the imaging,' we agreed that any propensity the speakers had in this regard was probably due to the single point source.
For me, I find the balance of the speakers to be quite acceptable overall. At the same time, I must respect the fact that there is a rising response in this driver even as I grow accustomed to it. I rarely have the urge to adjust the balance when I'm listening, but on a few tracks my friend preferred a slightly attenuated top end starting around 4k. There were even a few tracks where we attenuated the bass output. But when we switched to small ensemble jazz or 'world' music (e.g. Peruvian, Indian, Persian), we both preferred to bring the speakers back to their natural output.
I think the sweet spot for these speakers is female vocals and horns, which it delivers with astonishing clarity. I never get over my pleasure at hearing them through the W5s. Overall, I tend to select acoustic music to listen to with them: I love hearing the natural string decay of a Persian Setar or the picking of an acoustic guitar on these speakers. But they play electronica and other heavier music with confidence as well. I think the DCR design is very effective at suppressing cone movement because I never get the feeling that these drivers are being pushed outside of their comfort zone.
Anyway, those are just a few observations. I'm happy to say that I'm quite satisfied with these speakers, even considering their inherent inadequacies. Take it or leave it. The most important change I can make to my system now is to improve the quality of my source, and for that I need a good, cheap DAC. So the search begins anew!
Last night one of my students came over for a lesson. As he is also an audiophile so I asked him to bring some of good evaluation CDs and stay for a listening session. His speakers at home are Avalon Acoustics something-somethings. Anyway, after an hour or so we came to some mutual observations.
The bass from these speakers, while deep, is not convincing. In other words you will hear it but never feel it, robbing you of the tactile experience. But that was to be expected. With a 5" driver, just to have the bass there is all I had hoped for. (My next speaker will utilize larger drivers, perhaps even something along the lines of a bi-amped Beta 12LTA and alpha 15 OB. But this will have to wait until I have the space.)
We also agreed that imaging is quite good with these speakers. My friend bought his avalons on the basis of their soundstage capabilities, so for him this is the critical thing. We experimented a little bit with bringing the speakers away from the rear wall but didn't experience a major change in imaging. Given the addage that 'the thinner the baffle, the better the imaging,' we agreed that any propensity the speakers had in this regard was probably due to the single point source.
For me, I find the balance of the speakers to be quite acceptable overall. At the same time, I must respect the fact that there is a rising response in this driver even as I grow accustomed to it. I rarely have the urge to adjust the balance when I'm listening, but on a few tracks my friend preferred a slightly attenuated top end starting around 4k. There were even a few tracks where we attenuated the bass output. But when we switched to small ensemble jazz or 'world' music (e.g. Peruvian, Indian, Persian), we both preferred to bring the speakers back to their natural output.
I think the sweet spot for these speakers is female vocals and horns, which it delivers with astonishing clarity. I never get over my pleasure at hearing them through the W5s. Overall, I tend to select acoustic music to listen to with them: I love hearing the natural string decay of a Persian Setar or the picking of an acoustic guitar on these speakers. But they play electronica and other heavier music with confidence as well. I think the DCR design is very effective at suppressing cone movement because I never get the feeling that these drivers are being pushed outside of their comfort zone.
Anyway, those are just a few observations. I'm happy to say that I'm quite satisfied with these speakers, even considering their inherent inadequacies. Take it or leave it.
The most important change I can make to my system now is to improve the quality of my source, and for that I need a good, cheap DAC. So the search begins anew!- Status
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