I'm new to the forum. I've been building speakers off and on for nearly 30 years, but haven built a pair for several years, and so am just getting back into it. I picking up an organ here in a few weeks and am looking to get some speakers together for it. I'm not really into the whole vintage thing -- this is a later model digital organ (Rodgers 805), and though it is supposed to still be playable, it was hit by lightning and eventually has a few issues related to that (not yet sure how severe those are!). I will be looking to eventually turn it into a virtual organ (Hauptwerk). I mostly concerned about reproducing the extra low notes that an organ produces, which can be around 16 Hz, so I am currently focusing on the sub-woofer [first].
I like the looks (and price) of the SI HT 18 DVC sub-woofer (HT18 18″ Subwoofer | Stereo Integrity), and it looks like there are quite a few successful builds out there, so I'm feeling pretty good about this driver to get the job done.
I like closed boxes. I've built just about every kind of bass box conceivable, but in the end, I find the CB to be the most satisfying. I like the transients, and I like the fact that I don't have to have a filter to control the low frequencies for excursion considerations, and I find that the bass doesn't ring like a ported or equalized box. Space isn't really an issue, so it looks like (I haven't ran the numbers yet) that I could get a .7 Qtc with a box volume of 5.9 ft cu (Modeling question: SI HT-18 Sealed Excursion - AVS Forum | Home Theater Discussions And Reviews). Fair enough, I can live with that box size, and I think I should get plenty of bas considering room reinforcement and the fact that the CB drops of less steeply as compared to a ported configuration.
Here is the deal: I really wanted a 4 ohm load, because I think most amps and AV receivers could handle that. I wanted to run two drivers per side; However, whilst I was getting the lowdown on the driver, they sold out of the 4 ohm coil version! (I should have bought the first night I was looking!)! Nick at Stereo Integrity confirmed they won't be making any more (a damn shame really, since the next available 18 incher in their lineup is $535 bucks!!). So they still got the 2 ohm version which means I can wire them for 2 ohms or 8 ohms. OK, I could wire them for 2 ohms and there are a fair number of amps that can drive that load, but The Pioneer AV receiver I was looking at, for instance, only list power out at 4 and 8 ohms. So if I wire it for 2 ohms it may not be OK for some applications, and if I wire it for 8 then I may not be taking all the advantage of the ability of most modern amps to drive the lower impedance load and make more power. What to do!?
I guess I need to look at the current application now, and work about rewiring it later if I need to. The Hauptwerk virtual organ will put out stereo or mono, but it looks like the stereo is preferred. I was looking at an iNUKE nu1000 or 3000, which will drive a 2 ohm load so I guess that isn't a problem (interesting though that in bridged more it only lists 4 a 8 ohm?). The woofers are rated for 600 Watts each so I'm guessing something in the 1200 W/ch would be appropriate). So, any disadvantage to wiring for 2 ohm impedance? Am I on the right track here? Anything wrong with the logic?
Thanks, Kenny
I like the looks (and price) of the SI HT 18 DVC sub-woofer (HT18 18″ Subwoofer | Stereo Integrity), and it looks like there are quite a few successful builds out there, so I'm feeling pretty good about this driver to get the job done.
I like closed boxes. I've built just about every kind of bass box conceivable, but in the end, I find the CB to be the most satisfying. I like the transients, and I like the fact that I don't have to have a filter to control the low frequencies for excursion considerations, and I find that the bass doesn't ring like a ported or equalized box. Space isn't really an issue, so it looks like (I haven't ran the numbers yet) that I could get a .7 Qtc with a box volume of 5.9 ft cu (Modeling question: SI HT-18 Sealed Excursion - AVS Forum | Home Theater Discussions And Reviews). Fair enough, I can live with that box size, and I think I should get plenty of bas considering room reinforcement and the fact that the CB drops of less steeply as compared to a ported configuration.
Here is the deal: I really wanted a 4 ohm load, because I think most amps and AV receivers could handle that. I wanted to run two drivers per side; However, whilst I was getting the lowdown on the driver, they sold out of the 4 ohm coil version! (I should have bought the first night I was looking!)! Nick at Stereo Integrity confirmed they won't be making any more (a damn shame really, since the next available 18 incher in their lineup is $535 bucks!!). So they still got the 2 ohm version which means I can wire them for 2 ohms or 8 ohms. OK, I could wire them for 2 ohms and there are a fair number of amps that can drive that load, but The Pioneer AV receiver I was looking at, for instance, only list power out at 4 and 8 ohms. So if I wire it for 2 ohms it may not be OK for some applications, and if I wire it for 8 then I may not be taking all the advantage of the ability of most modern amps to drive the lower impedance load and make more power. What to do!?
I guess I need to look at the current application now, and work about rewiring it later if I need to. The Hauptwerk virtual organ will put out stereo or mono, but it looks like the stereo is preferred. I was looking at an iNUKE nu1000 or 3000, which will drive a 2 ohm load so I guess that isn't a problem (interesting though that in bridged more it only lists 4 a 8 ohm?). The woofers are rated for 600 Watts each so I'm guessing something in the 1200 W/ch would be appropriate). So, any disadvantage to wiring for 2 ohm impedance? Am I on the right track here? Anything wrong with the logic?
Thanks, Kenny
That is interesting and I had briefly thiught about using a horn. A couple of questions and observations: I think you would definately need an infrasonic filter, and I have always wondered about all od the notches in the response -- especiall those near the upper range where the sub is being crossed over.
What would be the advantage over a closed box? Are there any detailed plans that use the HT18 or recommendations for horn taper ratios and minimum initial area?
What would be the advantage over a closed box? Are there any detailed plans that use the HT18 or recommendations for horn taper ratios and minimum initial area?
This topic has been beaten to death lately 
.
Hi kennyrayandersen,
For Qtc=.707 Hornresp has Vrc=386.30L (V_net_internal) for a dual driver closed box using the SI HT18.
Closed or vented I recommend a PPSL arrangement of the drivers, see Post #591 here for a closed box example: http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html
The SI HT18 is one of the large voice coil drivers that caused "just a guy" to come up w/ the JAG-Fix, as the measured SPL does not agree w/ the SPL from a simulation. David McBean added a "Large Voice Coil" function in his Hornresp Loudspeaker Wizard.
The background information - and lots more links - can be found in these threads:
http://www.diyaudio.com/forums/subwoofers/277489-tapped-horn-cabinet-16-hz-organ-speaker.html , and
http://www.diyaudio.com/forums/subwoofers/272833-16-hz-church-organ.html
There is a lot of stuff in these threads, and they are almost required reading.
Regards,
.Hi kennyrayandersen,
For Qtc=.707 Hornresp has Vrc=386.30L (V_net_internal) for a dual driver closed box using the SI HT18.
Closed or vented I recommend a PPSL arrangement of the drivers, see Post #591 here for a closed box example: http://www.diyaudio.com/forums/subwoofers/177905-thread-those-interested-ppsl-enclosures.html
The SI HT18 is one of the large voice coil drivers that caused "just a guy" to come up w/ the JAG-Fix, as the measured SPL does not agree w/ the SPL from a simulation. David McBean added a "Large Voice Coil" function in his Hornresp Loudspeaker Wizard.
The background information - and lots more links - can be found in these threads:
http://www.diyaudio.com/forums/subwoofers/277489-tapped-horn-cabinet-16-hz-organ-speaker.html , and
http://www.diyaudio.com/forums/subwoofers/272833-16-hz-church-organ.html
There is a lot of stuff in these threads, and they are almost required reading
.Regards,
Two things here - First -
You can make a ported box that sound just like a sealed box, it's not hard to do. Here's a quick example I did awhile ago.
Details -
Sealed box - -black line - net volume ~= VAS, 200 liters
Ported box - grey line - net volume = 100 liters + port volume
An externally hosted image should be here but it was not working when we last tested it.
There are three big differences.
1. The sealed box is almost 2x larger.
2. Group delay is a bit higher on the ported box, but only below tuning, and tuning is very low - in other words inaudible difference. The GD spikes higher in frequency are very narrow and won't actually show up in measurements or listening tests.
3. The ported box (once a high pass filter has been added) will go 10 db louder within xmax limits.
A little bit of stuffing would kill the resonances in both the sealed and ported box examples, and if you tune your ported box at least as low as the lowest note to be played theoretically it won't need a high pass filter to protect the driver below tuning, but a high pass filter is still recommended regardless.
Usually people build "max flat" ported boxes with the lowest f3 possible and then complain about the bloated sound when used in a regular room. They call it "ringing" and complain about evil resonances but it's actually the frequency response that is the problem. If you design a ported box to have the same frequency response as a sealed box (especially if the tuning is very low) it should sound like a sealed box because the port, transients, ringing and resonances are not the issue, it's the frequency response that sealed box fans like.
For more information on all this see the original post here - http://www.diyaudio.com/forums/subwoofers/272833-16-hz-church-organ-76.html#post4376143
Second issue -
This driver belongs to a newer very high excursion large coil driver class that does not behave the way a simple simulation will predict, meaning that you can sim all you want but the final product won't match the sim.
First picture BLUE LINE is how this SI HT18 driver sims in a 4.2 cu ft sealed box. (Red line is adjusted to match reality.)
An externally hosted image should be here but it was not working when we last tested it.
This is the same driver in the same 4.2 cu ft sealed box measured result.
An externally hosted image should be here but it was not working when we last tested it.
As you can see there's a huge discrepancy between the blue line in the sim and the actual measurement. Simulating these large coil drivers properly is possible (as the red line in the sim shows) but a simple sim won't get even moderately accurate results.
If Bjorno's sim didn't account for the large coil issue it won't be accurate.
There's at least a small chance that these will be back in stock soon. SI has announced they were discontinuing this line before and after the very predictable surge in sales they ordered a boatload more and resumed the regular sale of this line. There's a lot of speculation that this is just a sales tactic and they will be right back in stock shortly after they sell out, just like last time.
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Kenny,
Bridged mono 4 ohms is the equivalent of 2 ohm stereo operation. Bridging the amp into 2 ohms would be the equivalent of stereo one ohm loads.
Many amplifiers run into current limiting and run hot at 2 ohms, but the iNukes run cool at 2 ohms, and also are capable of sustained low frequency output.
At two ohms, wire gauge becomes more important to keep damping factor high, use as little length and as low a gauge as can be fitted in the Speakon connectors.
Art
I REALLY appreciate the input guys. I guess I got some serious reading to do!
Interesting I got a one-word response from Nick... that was No!
just a guy,
"Usually people build "max flat" ported boxes with the lowest f3 possible and then complain about the bloated sound when used in a regular room. They call it "ringing" and complain about evil resonances but it's actually the frequency response that is the problem. If you design a ported box to have the same frequency response as a sealed box (especially if the tuning is very low) it should sound like a sealed box because the port, transients, ringing and resonances are not the issue, it's the frequency response that sealed box fans like."
Maybe -- I'll take your word for it. I know I've never really heard a 4th order system I liked better than a 2nd order, but I obviously ain't heard them all! I suspect that when tuned to low frequencies that the ported system behaves similar to a CB since the mass in the port doesn't get moving (resonating) until below where there is a lot of output, you may end up with something that is kind of like a quasi-CB? It's certainly worth considering.
Also, I'm not sure that the transients are quite as important with organ reproduction as compared to something like hearing the wave roll off a tympani drum. or the whack that comes off a bass drum; so, in the end, for what I'm using it for a ported box may well do what I need. I just worry about about having to mess with a high-pass for the bass driver -- just another thing to have to try and get right!
I suppose with all of the good simulation software that is now available it's much easier than it once was (you know -- back in the day when us old farts were hard at speaker-building!).
Interesting I got a one-word response from Nick... that was No!
just a guy,
"Usually people build "max flat" ported boxes with the lowest f3 possible and then complain about the bloated sound when used in a regular room. They call it "ringing" and complain about evil resonances but it's actually the frequency response that is the problem. If you design a ported box to have the same frequency response as a sealed box (especially if the tuning is very low) it should sound like a sealed box because the port, transients, ringing and resonances are not the issue, it's the frequency response that sealed box fans like."
Maybe -- I'll take your word for it. I know I've never really heard a 4th order system I liked better than a 2nd order, but I obviously ain't heard them all! I suspect that when tuned to low frequencies that the ported system behaves similar to a CB since the mass in the port doesn't get moving (resonating) until below where there is a lot of output, you may end up with something that is kind of like a quasi-CB? It's certainly worth considering.
Also, I'm not sure that the transients are quite as important with organ reproduction as compared to something like hearing the wave roll off a tympani drum. or the whack that comes off a bass drum; so, in the end, for what I'm using it for a ported box may well do what I need. I just worry about about having to mess with a high-pass for the bass driver -- just another thing to have to try and get right!
I suppose with all of the good simulation software that is now available it's much easier than it once was (you know -- back in the day when us old farts were hard at speaker-building!).
LOL, what were you expecting? He's done it before he might do it again. Or he might not.
Like I said, most people build "max flat" ported boxes with the flattest possible response until the lowest possible f3. I've never seen anyone make or even simulate something like what I've shown, which is an attempt to match a sealed box response with a ported box. Max flat ported boxes will sound boomy in room.
What you hear is frequency response, not transient response or ringing from the subwoofer. Those are things you just will not even notice if the tuning is low like 16 hz. What you WILL hear is the room. If there's lots of room gain the frequency response will be overly bloated in the lower octaves if you build max flat ported.
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The Fulcrum Acoustic TS 215 and TS 221, and my "PPSL 2x15 Shoehorn"
http://www.diyaudio.com/forums/subwoofers/255010-compact-2x15-ppsl-using-dayton-pa385-8-drivers.html
are all along the lines of your simulation. Most subs for PA use no longer use "max flat" alignments, opting for increased power handling and excursion to reduce cabinet size. The result can be anywhere along a continuum of alignments from a few to 12 dB (or more) down at Fb.
Art
Attachments
diy has regulated itself in part to push buttons and drop down menus. thinking outside the box, against convention etc are widely regarded as ridiculous.
So, I'm working my way through the 17 Hz Organ novella! Good Gosh almighty -- what a lot of drama!
In the mean time I ordered (4) IS HT18s D2 I may not need all four of them. My room is around 18 by 33 by 12h. The organ will be set up on one of the long walls.
JAG, I'm quite sure we did exactly as you were hypothesizing -- the goal back in the day was to get as low an F3 as possible whilst keeping the frequency response as flat as possible. It might well be that a different alignment would yield superior results. Also, as I was saying, I'm pretty sure the transient response of an organ isn't as critical in any case. LEt me get through the rest of the pile and then we'll open it on up!
In the mean time I ordered (4) IS HT18s D2 I may not need all four of them. My room is around 18 by 33 by 12h. The organ will be set up on one of the long walls.
JAG, I'm quite sure we did exactly as you were hypothesizing -- the goal back in the day was to get as low an F3 as possible whilst keeping the frequency response as flat as possible. It might well be that a different alignment would yield superior results. Also, as I was saying, I'm pretty sure the transient response of an organ isn't as critical in any case. LEt me get through the rest of the pile and then we'll open it on up!
OK, I finished the 17hz thread. My situation is a little different. First I don't have an existing box. Second I (in my humble opinion) probably have a little stronger background than the OP to seperaye fact from fiction, and thirdly I'm not trying to fill a sanctuary, but rather a livingroom. If that can be done with 2 drivers, one per channel, then fine, I'll add the extra boxes to my AV system.
My current thinking is to cross the sobs at something like 100-125 hz and then pass off the upper end to an MTM with maybe a pair of 6 1/2 midwoofs and a 25-28 mm tweet.
So, after reading the other organ thread, I'm thinking either ported with a low tuning or possibly a folded horn (if I can get past all of the port resonances (they just look odd.. )). I can build pretty much anything (not bragging, just saying), so there are basically no limitations on the box (unlessbit gets crazy big).
Let the fyn begin!
My current thinking is to cross the sobs at something like 100-125 hz and then pass off the upper end to an MTM with maybe a pair of 6 1/2 midwoofs and a 25-28 mm tweet.
So, after reading the other organ thread, I'm thinking either ported with a low tuning or possibly a folded horn (if I can get past all of the port resonances (they just look odd.. )). I can build pretty much anything (not bragging, just saying), so there are basically no limitations on the box (unlessbit gets crazy big).
Let the fyn begin!
What kind of horn are you looking at? Front loaded horn resonances don't look odd. Here's the measured response (green line) of Submaximus front loaded horn. It's quite large (4 feet x 4.75 feet x 2 feet) but it works. He had the SI 18 in mind when he designed it but this measurement shows the Mach 5 Audio UXL which is a bit more money than the SI 18 and a bit less available but it's the same type of large coil high power high excursion driver. The UXL is even more high power and high excursion than the SI 18. It's not trivial to design a horn so it's best to see how the SI 18 would work in this one (to check response and to check output vs a ported box). This one is tuned a bit lower than you need but if you used a high pass filter the low knee would be pretty close and this would have lots more output than sealed or ported. If you want more details - http://www.avsforum.com/forum/155-d...aded-horn-uxl18-stereo-integrity-ht-18-a.html
An externally hosted image should be here but it was not working when we last tested it.
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The "waves" are only about +/- 3 dB, small compared to the likely room response variations, but are part of the price paid for greatly improved sensitivity compared to a ported box. The rising response may actually result in a (generally) flat room response.
If you think an MTM with "maybe a pair of 6 1/2 midwoofs and a 25-28 mm tweet" is adequate for your upper end SPL requirements, a horn like the Submaximus will be way overkill.
Of course, for some folks too much bass is just enough...
The Submaximus measurement is what undersized horn response looks like. Full size horns don't have this much ripple but a full size horn with this tuning would be approximately the size of the room you want to put it in, so not very practical.
Here's what a full size ideal horn tuned to 12 hz with the UXL driver looks like. Response shown at 1 watt referenced to 3.2 ohm Re, although the minimum impedance of this horn in the operating range is 5 ohms so in reality it's even more sensitive than shown.
With 105 db sensitivity and 1.1 mm excursion at 1 watt (again in reference to 3.2 ohms Re which is lower than actual horn impedance) you don't really need a high pass filter and you could really break some stuff with this. And there's much less ripple in this response than the massively undersized Submaximus horn with the same driver.
And it's only 75000 liters. That's not a type, this is seventy five thousand liters.
An externally hosted image should be here but it was not working when we last tested it.
We would hope the sensitivity is greatly improved over a ported box but this horn is actually really massively undersized, tiny actually for the tuning frequency. And if it's not at least 4x larger than a ported box it won't have much sensitivity gain. That's why I suggested checking against a ported box to see how much advantage there really is. I haven't checked.
Of course since it is a horn it will outperform a ported box even if there is no advantage at all on paper (in a sim). The horn will always have lower power and port compression so will probably have a 6 db advantage even if there's no advantage at all in sims.
Bill Fitzmaurice's THT has only about 2 db of sensitivity gain over a ported box , for example, despite the fact that he's constantly blabbering about anything less than 6 db sensitivity gain being not worthwhile. I haven't looked into any of his other products but I doubt any of them have that much sensitivity gain.
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