OK.
After checking some notes on the calibrated measures , this for a purposed 24Hz tuning system, the way you are heading to and working with other members, (some notes, I wouldn't be surprised if a different system with smaller vol. higher tuning and giving more of a hump instead of the extension wouldn't sound nicer?! Also it all depends of your room (size and all?).
There's no need for protection with this alignments stated by me before and below.
For the 4" ports (1x port) you have about what was stated, a 78L@24Hz alignment with the port taking about the 4Ls mark. This, having a port with dimensions 4" in metric:
10.13 cm x 46.08 cm (DxL), giving length 18" 1/8 imperial.
Sd Surface Area: 80.60 cm2
For the 3" ports (2x ports) you have a new volume for the ports and length (3L for each port) giving a total volume of 6L (instead of 4L for the 4".)
A new 76L@24Hz enclosure with similar alignment. This, having 2 ports with dimensions 3" in metric (calibrated, again, as was stated on post #26):
7.74 cm x 57.19 cm (DxL), giving lengths 22" 1/2 imperial.
Dimension between ports: 6" (c2c)
Sd Surface Area: 94.10 cm2
All this is logical with the speaker/enclosure you have, the ports you have and the tuning you like (or a low tuning 24Hz and medium to big enclosure net ~70L as was previously stated in the comments).
After checking some notes on the calibrated measures , this for a purposed 24Hz tuning system, the way you are heading to and working with other members, (some notes, I wouldn't be surprised if a different system with smaller vol. higher tuning and giving more of a hump instead of the extension wouldn't sound nicer?! Also it all depends of your room (size and all?).
There's no need for protection with this alignments stated by me before and below.
For the 4" ports (1x port) you have about what was stated, a 78L@24Hz alignment with the port taking about the 4Ls mark. This, having a port with dimensions 4" in metric:
10.13 cm x 46.08 cm (DxL), giving length 18" 1/8 imperial.
Sd Surface Area: 80.60 cm2
For the 3" ports (2x ports) you have a new volume for the ports and length (3L for each port) giving a total volume of 6L (instead of 4L for the 4".)
A new 76L@24Hz enclosure with similar alignment. This, having 2 ports with dimensions 3" in metric (calibrated, again, as was stated on post #26):
7.74 cm x 57.19 cm (DxL), giving lengths 22" 1/2 imperial.
Dimension between ports: 6" (c2c)
Sd Surface Area: 94.10 cm2
All this is logical with the speaker/enclosure you have, the ports you have and the tuning you like (or a low tuning 24Hz and medium to big enclosure net ~70L as was previously stated in the comments).
Thanks Inductor, sorry I missed your post last week.
I finally cut the 4.5" diameter holes to allow a very tight slip fit for nominal 4" PVC pipe. I inserted the 24" port to the cabinet wall depth so I can use the full 84 liter box volume to start with. This is close to sreten's first proposal, but I have not measured impedance yet to see actual tuning frequency.
It sounds very good, definitely louder and lower and clearer tone than in the same box with sealed alignment. It does not have excessive punch, but it can hit "musically" when called to. The HT guys would think it is wimpy impact, but it's OK for listening to music, not bad for a 9.5" cone. I can hear some 20Hz test tone, and anything loose is rattles like crazy with about 10W applied. Seems loud enough for normal music listening. Excursion 20-29 Hz did not appear excessive by sight.
The driver is very detailed from mid bass up to cone breakup, but when it gets on the port it slows a bit. I think I'd like it to sound a little tighter, a bit more detailed if possible, without getting too punchy.
I'd like to hear a bit more tonal texture, as it seems like all bass (violin and electric) notes sound kinda like sinewaves, round and full, I guess audiophiles would call it "warm." But it is definitely NOT 'one note bass' and not as "warm" as when in was in the sealed box. I could be happy with this, just curious what else is possible since this is the extreme lowest Fb and biggest Vb possible.
Do I shorten the tube to make it sound tighter and drier? Or should I try smaller volume with the (still) long port?
The room is very big, with open floorplan. The -9dB at 20Hz of this alignment seems to work well acoustically, even if the tuning is a little too low for this little driver. If I do end up changing the alignment to sharpen the tone I will remember this target FR in the future when I try a more substantial subwoofer driver. It feels good, and the bass transients are strong but not always punchy only when the music calls for it.
I think there is more tonal clarity available. How do I find it, what to try next? I'll post the Z plot tomorrow.
Thanks!!
Rich
I finally cut the 4.5" diameter holes to allow a very tight slip fit for nominal 4" PVC pipe. I inserted the 24" port to the cabinet wall depth so I can use the full 84 liter box volume to start with. This is close to sreten's first proposal, but I have not measured impedance yet to see actual tuning frequency.
It sounds very good, definitely louder and lower and clearer tone than in the same box with sealed alignment. It does not have excessive punch, but it can hit "musically" when called to. The HT guys would think it is wimpy impact, but it's OK for listening to music, not bad for a 9.5" cone. I can hear some 20Hz test tone, and anything loose is rattles like crazy with about 10W applied. Seems loud enough for normal music listening. Excursion 20-29 Hz did not appear excessive by sight.
The driver is very detailed from mid bass up to cone breakup, but when it gets on the port it slows a bit. I think I'd like it to sound a little tighter, a bit more detailed if possible, without getting too punchy.
I'd like to hear a bit more tonal texture, as it seems like all bass (violin and electric) notes sound kinda like sinewaves, round and full, I guess audiophiles would call it "warm." But it is definitely NOT 'one note bass' and not as "warm" as when in was in the sealed box. I could be happy with this, just curious what else is possible since this is the extreme lowest Fb and biggest Vb possible.
Do I shorten the tube to make it sound tighter and drier? Or should I try smaller volume with the (still) long port?
The room is very big, with open floorplan. The -9dB at 20Hz of this alignment seems to work well acoustically, even if the tuning is a little too low for this little driver. If I do end up changing the alignment to sharpen the tone I will remember this target FR in the future when I try a more substantial subwoofer driver. It feels good, and the bass transients are strong but not always punchy only when the music calls for it.
I think there is more tonal clarity available. How do I find it, what to try next? I'll post the Z plot tomorrow.
Thanks!!
Rich
Attachments
Extreme alignments have the problem of step response/time behavior in the time domain (vs. frequency domain).
As is so typical in audiophile community, I have golden ears, but I have no taste.
So, can you explain what typical general subjective sound quality changes are to be expected when a port is lengthened or shortened?When you say measure, do you mean Z, and watch the dip approach target Fb?
I am trying ZeroD's proposed alignment next, 78 liters, 25Hz makes a 16.6" port. If I put that inside the box then Vb =78 liters. Clever!
How much extra length should I leave on the rough cut port length?
Thanks
Generally, Longer = lower fb & more gentle rolloff & less possible peaking around fb. Shorter = the opposite.
I meant if you have a calibrated Mic & suitable testing software, such as for eg, ARTA or REW.
I think it's a decent compromise. Don't forget the HPF is important ! If you don't have one yet, then don't go near full power.
Due to the previous discussed limitations with the driver, i wouldn't spend the time needed to keep cutting/extending it. Out of curiosity though to learn by experimenting, you could buy one of those plastic extendable/retractable ports. I think parts express sells them ? That way you could quickly try different lengths, but listening to lots of various tracks to determine your preference would obviously take Longer !
Anyway, keep us posted
Thanks for all the good advice.
I have OmniMic. When I measure the FR for each Lv change, do I measure just the cone, or cone and port separately to add later, or just measure overall FR from listening position (3M.)
Why do I want to measure FR? Do I want to watch FR for any underdamped response above flat? I should hear the punchiness by then, no?
I found a good explanation of reflex port by David Haigner
Says ideal fast and clean sounding reflex alignment has a port with large diameter, short length, but this requires very large box. So I want to keep my full box volume and suffer with less power handling. At 10W it is already very loud for me, I have 20W available til Xmax.
Roger on the High pass filter.
Looking at the Z plot I see it is tuned to 18.9Hz, not 20Hz as simulated. Troels' article about port tuning says most simulators predict too long port.
Up close FR looks good fwiw, matches sim pretty close! The in-room measurement at 3 meters seems useless, other than showing no bad modes. Actually the room modes look much better than normal with the cone and port separated making two LF sources instead of one.
Up close FR looks good fwiw, matches sim pretty close! The in-room measurement at 3 meters seems useless, other than showing no bad modes. Actually the room modes look much better than normal with the cone and port separated making two LF sources instead of one.
Attachments
Is it calibrated ?
The impedance plot will show the fb, & as you've discovered it's 18.9Hz which is near enough. Measuring the FR @ the listening position shows what you are experiencing.
If that's what you desire, yes.
Actually, punchiness usually means underdamped, and/or missing low bass, to a lot of people ! What you're looking for is a smooth & solid low extension.
Yes larger & short length is best, but not always achievable.
Fine
OK
.
WinISD allows for this "End Correction" in the port/s
Good
What really matters, is how it sounds to you.
Are you going to try the 25Hz port ?
I cut the pipe to 16.7". I miss the low bass extension of the 24" pipe, that is really nice but detail is masked. With 16" pipe the mid bass is much clearer. Lowest bass is still a little slow, but not bad.
I also tried the 7" cutoff piece. Sounds louder, clean, but no low bass, unnatural tone.
I'll post measurements later.
I also tried the 7" cutoff piece. Sounds louder, clean, but no low bass, unnatural tone.
I'll post measurements later.
I shortened the port to 14.5" to get measured 24.2 Fb. I can tape the pipe cuttings back on easily to compare. It's a little more detailed, but I miss the extension. Not sure which I like yet.
I calculated the alignment of the Duetta speaker linked in this thread by S4m (thanks!) Duetta uses rectangular equivalent of a ~3.84"x16.7" round port in about 85liters Fb 23Hz. I have tried that alignment when the port is exterior to the box. I do like how that sounds. It is extended and natural tone.
What about adding acoustic damping to the inside of the box? I currently have one side and the rear covered in 2" soft pink FG, so not much damping at all. I will be rolling it off LR2 ~150-250. So all fundamental wavelengths are larger than box dimensions. Does that mean I don't need to worry about acoustic damping? Thanks
I calculated the alignment of the Duetta speaker linked in this thread by S4m (thanks!) Duetta uses rectangular equivalent of a ~3.84"x16.7" round port in about 85liters Fb 23Hz. I have tried that alignment when the port is exterior to the box. I do like how that sounds. It is extended and natural tone.
What about adding acoustic damping to the inside of the box? I currently have one side and the rear covered in 2" soft pink FG, so not much damping at all. I will be rolling it off LR2 ~150-250. So all fundamental wavelengths are larger than box dimensions. Does that mean I don't need to worry about acoustic damping? Thanks
Hi,
Complete nonsense. The smallest that is practical is not optimum in any way.
What determines the smallest practical are the acceptable compromises.
Its also complete nonsense a Chebyshev needs a box 7 times bigger
than Butterworth. Its a very poor article in many simple respects.
In fact Chebyshev alignments use smaller boxes than Butterworth.
Its also wrong about damped alignments needing less box volume
than Butterworth, generally they need a little more and port detuning.
rgds, sreten.
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Yes, sreten I agree with you in your post here.
But I bet that what the author is saying (without more unnecessary confusions) that you have the least net for an optimal alignment, as one acceptable comparing to a large reflex with a step response that is less favorable. In the same line of what I'm saying (I'm not in defense of anyone in special, the author might have his personal explanation, and that if he's not dead already) you have Pi Speakers and the Wayne Parham's alignments.
But I bet that what the author is saying (without more unnecessary confusions) that you have the least net for an optimal alignment, as one acceptable comparing to a large reflex with a step response that is less favorable. In the same line of what I'm saying (I'm not in defense of anyone in special, the author might have his personal explanation, and that if he's not dead already) you have Pi Speakers and the Wayne Parham's alignments.
@ Richidoo
85 L @ 23Hz or 24.2Hz = 1.2Hz difference = not much at all ! Did you measure the 23Hz or estimate ?
Remember, a port outside the box takes up no internal space. Inside the box you need to account for this space, by subtracting it from the gross empty box size. So the external port gives you more internal literage for your driver.
Unless you were using it as a bass/mid, in my experience you don't need to stuff a bass box. Plus, a lot of stuffing effects the response. The box will acoustically appear bigger than it is.
Damping is different, & means reducing box vibrations etc, which is good.
I would try & roll off earlier than 150Hz if you can.
85 L @ 23Hz or 24.2Hz = 1.2Hz difference = not much at all ! Did you measure the 23Hz or estimate ?
Remember, a port outside the box takes up no internal space. Inside the box you need to account for this space, by subtracting it from the gross empty box size. So the external port gives you more internal literage for your driver.
Unless you were using it as a bass/mid, in my experience you don't need to stuff a bass box. Plus, a lot of stuffing effects the response. The box will acoustically appear bigger than it is.
Damping is different, & means reducing box vibrations etc, which is good.
I would try & roll off earlier than 150Hz if you can.
Measured. There is a small but noticable difference in the sound quality with 2.3" shorter port. They are both good.
Yes, thanks. It sounds better outside.
Cool, thanks! What's your port dimensions Mike?
Another box design, from Eton, their old "11.2" kit. 60liters with a shorty 70x120mm port.
http://www.audiokit.it/ITAENG/Altoparlanti/ETON/Eton11-2kitcabinet.pdf
http://www.audiokit.it/ITAENG/Altoparlanti/ETON/Eton11-2kitxover.pdf
I also tried a pseudo LLT with 24"L x 3"D pipe in the 82 liter box. It sounded pretty good at low volume, but excursion maxed out too easily.
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