Well, the "Serious Sub" looks like a great option to me for a new subwoofer build. Granted it would need a lot of power and EQ but I was wondering what everyone thought about going the route of using a 21" PA driver for a subwoofer.
I like the idea of going this route since the cone doesn't have to move as far for the same output and will give a much more effortless sound to the bass frequencies.
I don't see many builds like this so I dont want to rush into it. Especially considering the many Tapped Horn designs out there that are also worth considering.
Different tradeoffs that I can recognize right away are:
Tapped horn: Limited extension, large enclosure
Sealed 21" PA: limited SPL compared to TH, Massive power needs, needs EQ.
Any input into the different approaches would be appreciated.
Thanks.
I like the idea of going this route since the cone doesn't have to move as far for the same output and will give a much more effortless sound to the bass frequencies.
I don't see many builds like this so I dont want to rush into it. Especially considering the many Tapped Horn designs out there that are also worth considering.
Different tradeoffs that I can recognize right away are:
Tapped horn: Limited extension, large enclosure
Sealed 21" PA: limited SPL compared to TH, Massive power needs, needs EQ.
Any input into the different approaches would be appreciated.
Thanks.
A large TH can reduce excursion considerably, and can extend in to the 10 Hz range with a fraction of the power and driver expense of a good 21" driver in a sealed enclosure.
It really comes down to budget, tolerable cabinet size, and desired SPL at X low frequency.
I find a pair of sealed moderate Xmax 12" adequate for my SPL needs down to the low teens in my home, if I wanted more output would simply add more.
Since I find even short exposure to much over 100 dB at 20 Hz to make me feel sick for a while, I have no desire for more LF output than I have.
Attachments
best advice is to do some enclosure modeling to get a starting point, seeing as your "easily recognizable" trade-offs are not set it stone in either enclosure. With each enclosure type, you can manipulate the evil triangle known as Hoffmans Iron law. A tapped horn need not have a large enclosure, but if you make it too small sensitivity and low end extension may suffer. Each one has tradeoffs within themselves that you can easily see with enclosure modeling.
Which actual models have you produced/investigated?
Which actual models have you produced/investigated?
A few observations about the serious sub design:
- Weight of each sub is about 265lb including driver. That's pretty darn heavy. Take any sub design and put that much mass into it and it will sound better.
- Overall outer dim's seem to be about 25" x 23" X 20", which is pretty compact and smaller than many ported 15's people build. 110L internal sealed seems a bit low for this driver IMHO.
- There is a bunch of parametric EQ being done, to flatten room response and boost the low end. IMHO this induces pretty noticeable phasing issues. When given the choice between a bit of minor uneven frequency response (+/- 3-5db in room) vs. eq induced phasing issues, I would rather have the minor uneven response because it will sound more natural and clear than messed up phase. Phase issues in the upper bass and midbass are VERY noticeable in your dynamics/tranisent response, say from 50hz to 300hz.
- I would rather have a ported box (with a correctly designed port) than sealed plus EQ, even though it would probably end up much larger with this woofer.
- The Sd is equivalent to two 15" woofers. Xmax of the PD is about 10.5mm, so a single long throw (21mm+ xmax) 15's could match it in output.
- I can't imagine the cone is particulary rigid. Do you prefer your distortion from the cone flexing (21" sub) or from the motor/spider/surround movement (long throw 15")? The industry & market has been saying for quite some time that long throw smaller drivers are much more practical, and can sound quite good if done properly.
- He may have a point about the accoustic coupling of the large woofer to the surrounding air. You get a sensitivity boost by stacking multiple (usually) horn subs together to get better coupling, so I would imagine a single large driver does better than a long throw smaller driver in that respect.
- IMHO the mdf, lead, and bracing is not very efficient for the weight and complicated build. 1" thick birch plywood with 1/8" bitumen on the inside would probably be as stiff and damp while being less than half the weight and much easier to build. The bracing is overly complex, two 3" slats (no holes) along each wall with 2" cross braces would be just as effective and much simpler to build.
- Weight of each sub is about 265lb including driver. That's pretty darn heavy. Take any sub design and put that much mass into it and it will sound better.
- Overall outer dim's seem to be about 25" x 23" X 20", which is pretty compact and smaller than many ported 15's people build. 110L internal sealed seems a bit low for this driver IMHO.
- There is a bunch of parametric EQ being done, to flatten room response and boost the low end. IMHO this induces pretty noticeable phasing issues. When given the choice between a bit of minor uneven frequency response (+/- 3-5db in room) vs. eq induced phasing issues, I would rather have the minor uneven response because it will sound more natural and clear than messed up phase. Phase issues in the upper bass and midbass are VERY noticeable in your dynamics/tranisent response, say from 50hz to 300hz.
- I would rather have a ported box (with a correctly designed port) than sealed plus EQ, even though it would probably end up much larger with this woofer.
- The Sd is equivalent to two 15" woofers. Xmax of the PD is about 10.5mm, so a single long throw (21mm+ xmax) 15's could match it in output.
- I can't imagine the cone is particulary rigid. Do you prefer your distortion from the cone flexing (21" sub) or from the motor/spider/surround movement (long throw 15")? The industry & market has been saying for quite some time that long throw smaller drivers are much more practical, and can sound quite good if done properly.
- He may have a point about the accoustic coupling of the large woofer to the surrounding air. You get a sensitivity boost by stacking multiple (usually) horn subs together to get better coupling, so I would imagine a single large driver does better than a long throw smaller driver in that respect.
- IMHO the mdf, lead, and bracing is not very efficient for the weight and complicated build. 1" thick birch plywood with 1/8" bitumen on the inside would probably be as stiff and damp while being less than half the weight and much easier to build. The bracing is overly complex, two 3" slats (no holes) along each wall with 2" cross braces would be just as effective and much simpler to build.
Last edited:
Once the box gets small enough, the tapped horn will have the same sensitivity and frequency response as a ported design of the same size. Always model your driver from a tapped horn design in a ported design of the same volume.
As tapped horns get larger they can trade low frequency extension for sensitivity and output while maintaining a relatively flat frequency response.
Whereas ported designs mostly improve their low frequency extension (a bandwidth increase), and drop in sensitivity.
Last edited:
Some one else commented to me the other day that 15" would be more than enough as well.
I have yet to build anything as I keep reading and studying the books I have on audio design etc.
I think my problem is that I don't know what compromises I like best.
I am limited by size and the one that I can fit in my room is the T6 tapped horn that only really reaches about 28hz which is still enough for the majority of movies but the ones that go lower I think I will be missing something as even with my current sub that reaches 20hz, I feel like there are alot of times that there is content that I am not getting like in "How to Train Your Dragon" and other movies.
A dual 15" in a sealed cab will most likely meet all my needs but like what was mentioned earlier, the EQ can cause phasing issues.
an LLT is too large for me for the most part as well and can suffer from chuffing if not done right.
I currently run a PC12-NSD and I have thought about doing another ported cylinder for the easy sealed sub with dual 15" or just going to a 15" tuned lower to about 15-17hz. However, my wife would like me to go to something a little more eye friendly...So then I have looked at sealed boxes and ported boxes. But to really get a little bit lower of extension in a ported sub the boox usually ended up pretty large. So I then looked at PR designs and I dont like the extra expense...
GAH! audio is such a pain sometimes....maybe i'll just get a divorce ahah!
When I ran my recent project of a pair of dayton HO 15's as sealed (plugged the ports) with big EQ, they ran out of headroom/xmax @ 20-25hz in a moderately sized living room watching movies. For dedicated HT use I would want more, so a ported design tuned to around 18hz or so.
To get below 40hz with a tapped horn at high sensitivity (98-100 db/w/m/2pi horn resp sim), it seems that you get into increasingly huge boxes. An efficient 20hz tapped horn is going to be HUGE, if it is small it will have have the same sensitivity of a ported box of the same size.
If you are willing to compromise, there is tons of bass presence (physical shake) in the 30-40hz range, so if your response is strong there it can pass as deep bass for the casual observer. Several of the larger diy tapped horns acheive that well.
I know people LOVE tapped horns here, but I think a well designed and constructed ported box is more practical and effective for all around home music and HT use.
Tell me about it... It just never stops.
You have not mentioned exactly what your size demands are yet. Have you looked at all your placement options? Maybe you could use a new table? Stereo bench? Is IB an option?
turbodawg:
Force>Power
Edit:
It's not deep bass until all your cabinet doors start shaking a lot, the room itself resonates but you can hardly hear the sound at all. Great fun! But I settle for less.
Last edited:
EQ does result in phase shift, but when used for corrective purposes, it reduces phase shift, which is a positive feature, not an "issue".
As you can see in the examples below, the flatter equalized response also results in a flatter phase response.
The Mackie HD1502 uses built in equalization, note how flat both the frequency and phase are.
The DSL SH-100 has a dip in FR around 125 Hz, and a bit much HF above 8K, notice how both areas smooth out in phase response when corrective EQ is applied.
The trade off is whether the EQ will cause audible distortion when applied liberally.
With speakers like the B&C 21" (or their high powered 18"), the suspensions "put the brakes" on high excursion, it is almost impossible to make them sound bad. I can't say the same about the Lab 12, even though I'd agree with Sreten that 2xLAB12's in 100L each tuned to 20Hz, 500W each,
is more than enough for nearly all domestic systems.
My observation with listening to movie sound tracks is that most VLF is accompanied by enough other upper noise that LF distortion tends to be hidden, unless it is really severe, like voice coils hammering on the top plate.
That said, without some measurements, we are guessing what is enough for you, the PC12-NSD is not enough, but a Gjallerhorn would obviously fail the WAF.
Attachments
OK....but boosting the low end on a sealed sub with either a low shelf, linkwitz transform, or PEQ will produce phase shift and group delay, similar to a ported box.
Just happened to stumble across this as a (somewhat) compact sub that gets down to 35hz or below........
Cubo Sub
(scroll down to see plan)
cubo sub - Speakerplans.com Forums - Page 1
http://www.diyaudio.com/forums/subwoofers/192707-best-sub-5.html
Cubo Sub
(scroll down to see plan)
cubo sub - Speakerplans.com Forums - Page 1
http://www.diyaudio.com/forums/subwoofers/192707-best-sub-5.html
That is not true, at least not with the Alesis DEQ830 I use for monitor EQ for live sound and on my stereo, inserted in the tape loop.
The screen shot shows my stereo sub out driving a sealed 2x12" sub measured in room, near field (on the floor next to the plenum output), with no EQ, and with EQ flat to 25 Hz, the lowest band on the DEQ830.
No group delay has been added by the EQ as evidenced by the phase in the upper portion of the band pass being unchanged.
As you can see, the phase response in the area of EQ has actually flattened compared to the EQ'd response.
The DEQ830 is a non-combining filter type, the EQ's response below 25 Hz goes back to flat response, resulting in the relative phase change below 25 Hz.
At any rate, not all EQ is created equal, but the DEQ830 does not produce any undesirable phase shift or group delay.
Although more difficult to accomplish than using Smaart, even with your Radio Shack dB meter you could determine whether whatever EQ you use introduces group delay.
Art
Attachments
That graph clearly shows an increased rate of phase change with the EQ, which would translate into increased ramp up of group delay. There is no way that can be considered an improvement in phase response.
Last edited:
Smaart 6’s automatic delay locator finds the time offset (delay) between two input signals by measuring the impulse response of the SUT. This measurement was performed automatically for the frequency and phase response measurements posted, without doing it phase traces would not be valid.
The delay measurement requires both reference and measurement signals.
If there was a "ramp up of group delay", it would show as a change in the upper pass band's phase response, and it would have changed the delay noted in Smaart 6’s automatic delay locator, neither of which occurred.
If there is something I'm missing in the interpretation of the Smaart phase response graphs, please point it out.
The GD does indeed increase at the EQd area. But not due to EQ per say, it is just following miniphase behavior where a change in frequency response (here a steeper change in rollof) produces a related change in phase. Phase improves above EQ point due to flat frequency response, and it worsens below due to steeper rollof.
As Art pointed out the same happens when flattening the frequency response the phase flattens as well.
No matter what you do you will have increasing GD at lower frequencies due to LF rollof, making it less steep will produce less GD, by design or by EQ does not matter.
The only way to make it completely flat is to have a sealed sub in a sealed room and EQ the response flat to 0Hz.
EQing a sealed to the same response as a ported cab will produce the same GD. Unless the ported is not miniphase, but all I have measured have been miniphase.
Having a flat phase/amplitude down to where the rollof starts is IMHO better than having a change starting way above that point. Even if the steep rollof due to EQ will produce lots of GD in a big spike, when transforming the frequency response back to time domain (or just feeding the speaker with music) you will have a less altered attack and decay of transients as more of the passband can pile ontop of each other to create a pressure impulse without spreading it out in time. If that makes any sense.
Big bass horns have a very bad GD spike at the rollof point due to the high dB/oct the small back chamber + acoustical loading produces, yet the attack and decay seems to be unparalleled. And the slower rollof of a BR with it's lower GD can't seem to keep up.
As Art pointed out the same happens when flattening the frequency response the phase flattens as well.
No matter what you do you will have increasing GD at lower frequencies due to LF rollof, making it less steep will produce less GD, by design or by EQ does not matter.
The only way to make it completely flat is to have a sealed sub in a sealed room and EQ the response flat to 0Hz.
EQing a sealed to the same response as a ported cab will produce the same GD. Unless the ported is not miniphase, but all I have measured have been miniphase.
Having a flat phase/amplitude down to where the rollof starts is IMHO better than having a change starting way above that point. Even if the steep rollof due to EQ will produce lots of GD in a big spike, when transforming the frequency response back to time domain (or just feeding the speaker with music) you will have a less altered attack and decay of transients as more of the passband can pile ontop of each other to create a pressure impulse without spreading it out in time. If that makes any sense.
Big bass horns have a very bad GD spike at the rollof point due to the high dB/oct the small back chamber + acoustical loading produces, yet the attack and decay seems to be unparalleled. And the slower rollof of a BR with it's lower GD can't seem to keep up.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.