Hello- an introduction, since I recently joined here. I'm in my 50s now, enjoyed a lot of dabbling in building and modifying amplifiers and speakers back in my teens and early 20s, and getting back into it now after building with my son (20) a refurbed Dynaco SCA-35 with new Dave Gillespie EFB and replacement pc boards, and other upgrades.
I gave my son a TubeCube 7 amp for Christmas and also bought some parts that I hope will make some nice compact speakers (within the constraints that go with small) to go with the TubeCube for the current and coming years when he'll be moving frequently with dorms, apartments, etc.
The drivers I bought are the relatively new Fountek FR59EXE
FR59EXE
Parts Express' website listings for the FR59EXE seem to suggest an f3 of about 326hz for a sealed enclosure and about 182hz for a ported enclosure (bot with enclosure volumes different from what I am using)
For enclosures I bought some electrical PVC junction boxes, Kraloy JB444, which are marked as having an internal volume of 56 cu. in. / 916 cc.
Also picked up some surplus small rack handles, and, after the various work is done, the grey PVC is going to be coated in aerosol Rustoleum truck bed liner, for both looks and durability.
Photo of the partially built unit, laying on its back (driver will face sideways, the hardware wasn't tightened so it's on its back in the photo) are attached.
I recognize that the laws of physics are such that these FR59EXE drivers will never be bass-monsters, but I would like to do what I can, given these drivers and enclosures, to try to eke out maximum reasonable/ clear bass given what I am working with.
A month or so ago when I began plotting this, I'd used some online calculators and had seemed to come up with approximations of a 1/2" diameter port in the vicinity of 1.25 - 1.75 long. But those calculators also seemed to presume box proportions different than the roughly cube-shaped shape of the PVC boxes that I am using. And also because I am a re-newb to much of this (and a lot of the science of speaker design was either absent or not in wide circulation when I was dabbling in this 20+ years ago) I am not super confident in my use of the design/calc tools.
Appreciate any and all suggestions, please, on porting this and otherwise trying to get maximum/ clear bass from this little unit.
Thanks very much in advance for any help!
I gave my son a TubeCube 7 amp for Christmas and also bought some parts that I hope will make some nice compact speakers (within the constraints that go with small) to go with the TubeCube for the current and coming years when he'll be moving frequently with dorms, apartments, etc.
The drivers I bought are the relatively new Fountek FR59EXE
FR59EXE
Parts Express' website listings for the FR59EXE seem to suggest an f3 of about 326hz for a sealed enclosure and about 182hz for a ported enclosure (bot with enclosure volumes different from what I am using)
For enclosures I bought some electrical PVC junction boxes, Kraloy JB444, which are marked as having an internal volume of 56 cu. in. / 916 cc.
Also picked up some surplus small rack handles, and, after the various work is done, the grey PVC is going to be coated in aerosol Rustoleum truck bed liner, for both looks and durability.
Photo of the partially built unit, laying on its back (driver will face sideways, the hardware wasn't tightened so it's on its back in the photo) are attached.
I recognize that the laws of physics are such that these FR59EXE drivers will never be bass-monsters, but I would like to do what I can, given these drivers and enclosures, to try to eke out maximum reasonable/ clear bass given what I am working with.
A month or so ago when I began plotting this, I'd used some online calculators and had seemed to come up with approximations of a 1/2" diameter port in the vicinity of 1.25 - 1.75 long. But those calculators also seemed to presume box proportions different than the roughly cube-shaped shape of the PVC boxes that I am using. And also because I am a re-newb to much of this (and a lot of the science of speaker design was either absent or not in wide circulation when I was dabbling in this 20+ years ago) I am not super confident in my use of the design/calc tools.
Appreciate any and all suggestions, please, on porting this and otherwise trying to get maximum/ clear bass from this little unit.
Thanks very much in advance for any help!
Attachments
Greets!
A few quick notes....... for vented, not a good plan to tune < 1/2 octave below Fs = ~139 Hz * 0.707 = ~98 Hz and even though it will only handle a couple of watts due to low tuning, the vent ideally needs to be at least 0.75" i.d. diameter to minimize any vent 'chuffing', so assuming ~50"^3 net box volume [Vb] = ~3.62" long.
GM
A few quick notes....... for vented, not a good plan to tune < 1/2 octave below Fs = ~139 Hz * 0.707 = ~98 Hz and even though it will only handle a couple of watts due to low tuning, the vent ideally needs to be at least 0.75" i.d. diameter to minimize any vent 'chuffing', so assuming ~50"^3 net box volume [Vb] = ~3.62" long.
GM
Thanks! In terms of any observable difference in how it will sound, will we likely perceive notably more bass if we tune for 98 hz vs the [if I am inferring correctly from your comment] 'safer' 139hz? And if 139hz is maybe wiser to aim to tune for, what do your calcs indicate for a port length for the 139hz? [your figures are coming out with a slightly longer length than mine, but I trust your calculations as being better informed than mine]
If I need to go with a port diameter around .75" i.d., I'll probably use Schedule 80 3/4" PVC which is 0.742 i.d. - a bit under the .75 but closer than any of the other available options. Any other options start getting substantially bigger in diameter and the next smallest- Sch 40 1/2 PVC is .622
Thanks!
My other puzzlement is that some of the online calculators, like this one
Loudspeaker enclosure calculating with Thiele Small parameter
[and that is if I trust them, and also if I trust whether I am using them correctly, neither of which is a given...]
seem to suggest that, with my parameters of driver and box size, I gain nearly no advantage in low frequency response as compared to a sealed box?
Thanks again for input and for patience with someone just getting re-immersed in any of this
Loudspeaker enclosure calculating with Thiele Small parameter
[and that is if I trust them, and also if I trust whether I am using them correctly, neither of which is a given...]
seem to suggest that, with my parameters of driver and box size, I gain nearly no advantage in low frequency response as compared to a sealed box?
Thanks again for input and for patience with someone just getting re-immersed in any of this
In the .916 liter enclosure, leaving it closed gives a fairly smooth response (Qc = 0.85). The downside is that Fc = 330 Hz.
If a .75" vent is used with the .916 liter enclosure, it would need to be .55" long to tune to 182.5 Hz. However, the response has a +2.5 dB hump at 400 Hz. Leaving it closed does look better.
You could get a better vented box response with a 2.40 liter (147 cu in) box tuned to about 140 Hz. A 1.50" dia x 1.75" long vent would get about 140 Hz in a 2.40 liter box. (another option is 1.0" dia x 0.53" long) If you leave the 2.40 liter box closed, Fc = 231 Hz, and Qc = 0.60.
Another option would be 1.832 liters (2 x .916). A .75" dia x 0.38 long vent would tune to 140 Hz also. A closed box of 1.832 liters has Fc = 253 Hz and Qc = 0.66.
Hope this helps.
If a .75" vent is used with the .916 liter enclosure, it would need to be .55" long to tune to 182.5 Hz. However, the response has a +2.5 dB hump at 400 Hz. Leaving it closed does look better.
You could get a better vented box response with a 2.40 liter (147 cu in) box tuned to about 140 Hz. A 1.50" dia x 1.75" long vent would get about 140 Hz in a 2.40 liter box. (another option is 1.0" dia x 0.53" long) If you leave the 2.40 liter box closed, Fc = 231 Hz, and Qc = 0.60.
Another option would be 1.832 liters (2 x .916). A .75" dia x 0.38 long vent would tune to 140 Hz also. A closed box of 1.832 liters has Fc = 253 Hz and Qc = 0.66.
Hope this helps.
Thank you! I am beginning to think of how to do a secondary/ separate enclosure that could be like a very small subwoofer, to reach down to the lower frequencies....and/or, before getting into additional enclosures and drivers, I have a few spare enclosures and some scraps of PVC conduit that I could just try some trial and error of different ports, just in case I happen to be able to blunder upon something that manages to sound good...
I'm also wondering if a series capacitor could pull the resonance of the driver downward, although how much it could accomplish at that would probably be limited and they'd start getting bulky...
6th order assisted is the accepted way to electronically extend the LF: http://www.xlrtechs.com/dbkeele.com/PDF/Keele (1975-07 AES Published) - New Set of VB Alignments.pdf
GM
GM
Trouble is that your drivers will only go down to 330Hz (sealed) or maybe 180Hz (vented). None of which will give any impression of bass. Most 20-year-old sons will want to hear the bass.
A sub that will reach that high will be very audible and located. So, it would be better to have stereo subs. Plus, I don't know any sub amp that would allow a cutoff at 330Hz... so it would have to be passive, and parts for an XO this low are getting expensive.
Suggestion...
Maybe keep those Fountek drivers for a car audio project, and consider another driver that will be a lot more satisfying, without all the headaches that seem to be on the way trying to build this.
You're welcome!
Our peak hearing acuity is in the 2-3 kHz range, falling off at each end, so tuning can often be off quite a bit before folks will notice if for no other reason than down low the room's eigenmodes, reflections dominate, so no need to sweat the small errors, which on paper the fractionally smaller tube shifts the tuning < 1 Hz lower, though if you bevel/taper/'knock off' both ends of the vent at ~45 deg. it will shorten it a bit acoustically, raising tuning plus lowering its vent mach a little.
The main difference you would hear between the two [based on sims and IME] is an obviously more robust, 'toe tapping' mid bass, possibly to the point where more internal damping is required than normal whereas the EBS will sound more like a well damped sealed alignment [low Qtb = much better transient response] except with more mid bass gain, though still ~ -3 dB down at the ~139 Hz tuning point [Fb], which if you play with an equalizer this isn't a major difference this low down.
That said, Hornresp is one of the most accurate programs WRT basic vent tuning, i.e. vent-in-baffle away from any box side, back walls.
Note too that tuned really low and/or in an odd spot such as a mantle/whatever, one often needs to either empirically or use room acoustics software to tune them in room to best overall blend them to it, which in turn can often require each speaker be tuned individually.
Re 'safer' tuning, it's more about playing louder over a narrower bandwidth [BW] with the extended bass shelf [EBS] alignment's lower tuning actually protecting it a little lower at the expense of a lower mid bass output.
With such alignments, especially high tuned ones, they need some form of high pass filter to protect them unless of course the amp is so low power it can't overdrive them.
Anyway, again assuming a 50"^3 net Vb, 139 Hz = 3.9 cm/1.53" long vent.
GM
??? Is the published Fs this far off?!
Otherwise in his oversize box it can get down to ~100 Hz and by either sitting off axis and/or using EQ to get the necessary baffle step correction to tonally balance it out to its HF limit it should sound as good or better than current TV stereo speaker systems.
GM
My son, without any attempted influence on my part, moved beyond the draw of oompah-whoompa and into clarity and depth of sound, all on his own, several years ago. That's making it very fun for me to dive back into audio experimentation after not having done much with it since I was his age, and, the information available today is a cornucopia (bordering at moments on overwhelming) compared to when I was dabbling in audio in the '70s and '80s.
Re: 'headaches,' I appreciate the effort to spare me frustration, I kind of want to see this project through, at least as best I can within the unavoidable constraints, and I take some sort of curious satisfaction in trying to pull off something a bit difficult/ out of the box.
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Thanks! Re: high pass & risk of overdriving the speakers, these will specifically be used with a single-ended EL34 amp that will max out, optimistically, at 3w per channel, so the risk of being overdriven isn't what it would be a 'normal' system.
I am also giving thought to whether I should consider a passive radiator - Parts Express/Dayton has come out with some new small ones - instead of a vent - but I'm, so far, very unfamiliar with how to pick the details of a PR in relation to driver characteristics and box size. I greatly appreciate everyone's patience with my level of knowledge/ lack thereof- I am on the steep but exciting early end of the learning curve... Thanks
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With speakers this small, you really want them very near to the wall behind them. The last thing you want is a loss of any bass. (See Baffle Step Correction)
You're welcome!
@##$%^&!, missed this assuming it was one of those dinky chip amps so popular nowadays and per usual, didn't find its output impedance and/or damping factor listed, a key spec when wanting to use a tube SET amp, which in turn would have saved us some time since SETs automatically require pretty much exact Fs tuning [equal amplitude impedance peaks] when one wants to maximize bass response.
Still, according to HR it's already exceeding Xmax [~10% distortion] at 2 W and clipping at 3 W/~135 Hz, so caveat emptor.
PRs typically require powerful motors to perform well; that, or have incredibly high Vas [limp as wet toilet paper suspension], i.e. most likely requires DIY from scratch in this case, so might want to experiment with rigid baffle, base and make the rest of the cab out of thin veneer or other flexible material to allow it to increasingly 'breathe'/resonate in the bottom 1/2 octave if not happy with a simple vent.
GM
Thanks again to all for all of the input. Been busy helping family with various things but plan to do some empirical testing of these with ports of varying dimensions, hopefully Saturday. If they seem incapable of delivering reasonable amounts of low frequency sounds, I am already conspiring of different possible ways to make a small but effective subwoofer, maybe with the micro-sized Tang Band subwoofer amp that's available from Parts Express.
Thanks again!- Exploring some 'sub' thoughts here:
https://www.diyaudio.com/forums/subwoofers/331946-micro-scale-ripole-sub.html#post5650618
Thanks again!- Exploring some 'sub' thoughts here:
https://www.diyaudio.com/forums/subwoofers/331946-micro-scale-ripole-sub.html#post5650618
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