It represents an average around 30 seconds of the track.
Others exemples
Bob Sinclar: Love Generation
LMFAO: I'm sexy and I know it
David Guetta : without you
Global Deejays: Party 2 Daylight
Others exemples
Bob Sinclar: Love Generation
An externally hosted image should be here but it was not working when we last tested it.
LMFAO: I'm sexy and I know it
An externally hosted image should be here but it was not working when we last tested it.
David Guetta : without you
An externally hosted image should be here but it was not working when we last tested it.
Global Deejays: Party 2 Daylight
An externally hosted image should be here but it was not working when we last tested it.
Hi, I've taken the models you provided and adjusted them for xmax cone displacement in the passband:
MTH30, B&C 12CL76, 6mm xmax, $162, 7 lb driver
15" Dayton HO (ported, 2.5 ft3, 39.5hz tune), 12mm xmax, $172, 24 lb driver
As you can see, the xmax limited output potential is quite comparable. Yes, I understand that the dayton is seeing over the rated RMS power in this scenario, but that doesn't matter unless you want to play test tones at xmax. The ported dayton extends to a bit below 40hz, a solid 15 hz lower than the MTH30, while having a much more pleasant response curve.
Sure, there are more capable drivers that could be used in the MTH30 to increase output, but there are also plenty of 20+ mm xmax 15's around for more money. And there's no way to get the mth30 to do anything below 50hz.
I've also attached a sim of the HO 15" at the actual 35hz tuning that mine ended up at, which extends to about a 34hz f3, while losing less than 1db sensitivity vs. the original model.
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If only it were so simple
Vented alignments and THs behaving very differently when the volume is turned up. Vented alignments tend to suffer from compression at higher volumes (the output from the vent is non-linear unless the vent is very large, and at higher volume levels the output from the vent is less than you'd expect it to be). Furthermore, you're running the vented alignment at a higher power level, which means that you're going to have more power compression due to voice coil heating as well.
In the case of the TH, the whole box is just one big massive vent, so vent non-linearity is much less of an issue. Secondly, you're running it at a lower power level than the vented alignment to get the same output, so power compression is less of an issue. And finally with most THs, the driver is mounted magnet out, resulting in the magnet sitting in an area of maximum velocity (at or near the mouth), so it's going to get a bit more cooling than a driver in a vented alignment, where the magnet is basically sitting in the box, uncooled by any air flow.
The end result of this is that, even if the predicted output levels at Xmax between the two alignments may be similar, the predicted peak output of the TH is likely going to be a lot closer to reality than the predicted peak output of the vented alignment, and by several dBs too.
All of these suggest that you need an F3 below 50 Hz in order to reproduce these tracks as they are recorded. Any higher than that (and specifically so with one of the higher-order alignments where the FR drops like a stone below Fb), and you're losing a good part of that bass.
Hi ghettosynth,
Would it be possible for you to post the details of a design example where changing the dimensions makes no difference to the predicted results? Thanks.
Kind regards,
David
If only it were so simple
Vented alignments and THs behaving very differently when the volume is turned up. Vented alignments tend to suffer from compression at higher volumes (the output from the vent is non-linear unless the vent is very large, and at higher volume levels the output from the vent is less than you'd expect it to be). Furthermore, you're running the vented alignment at a higher power level, which means that you're going to have more power compression due to voice coil heating as well.
In the case of the TH, the whole box is just one big massive vent, so vent non-linearity is much less of an issue. Secondly, you're running it at a lower power level than the vented alignment to get the same output, so power compression is less of an issue. And finally with most THs, the driver is mounted magnet out, resulting in the magnet sitting in an area of maximum velocity (at or near the mouth), so it's going to get a bit more cooling than a driver in a vented alignment, where the magnet is basically sitting in the box, uncooled by any air flow.
The end result of this is that, even if the predicted output levels at Xmax between the two alignments may be similar, the predicted peak output of the TH is likely going to be a lot closer to reality than the predicted peak output of the vented alignment, and by several dBs too.
Tapped horns still have to flow air just like any other box and do suffer compression. Most of them don't make their sim's either. Real world, when you start putting one or more 180 degree folds into a duct, with no rounding of the turn, you're going to see some very noticeable flow losses once things get going. Not to mention the cone distortions, wonky phase response/group delay/ringing, and time correction to your mains needed to set one up properly.
Data-Bass
There are plenty of poor ported boxes out there. If you take a 15" and put it in a box with a single 3" diameter port, of course you're going to have compression issues around tuning. The JBL white paper and various other sources go into considerable detail about how to size and roundover ports properly and how to counteract compression with frequency response by creating a slight peak at tuning.
The subs I have built use a slot port 15"x2.5", which is equivalent to a 7" round port in section area (not as optimal in flow but close). It also has rounded inlets and outlets, with a 90 degree turn at the end with a 45 deg slat. Bracing has also been optimised to be parallel to the flow of air, there is virtually nothing restricting the flow getting to the port. Running 35hz (actual tuning) test tones at about 2/3rd's max output, port noise (and hence compression) is minimal and there is quite a large amount of air being moved. Trust me, there is plenty of air being moved to cool the woofer motor, which also happens to use a large aluminum cone.
If you really want a proper and optimized ported box, you have to go look at competion car audio. They build extremely stout boxes that are designed for massive power, long excursion drivers, and huge air flow at relatively high tunings. They have numerous tricks optimize air flow which are not normally done in pro or home audio.
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Hi David,
Out of context my comment probably appears to make no sense, of course hornresp designs consider the dimensions of the cabinet, however, only as a consequence of the dimensions of the unfolded horn. In other words, the cabinet dimensions proper that are not a function of the unfolded horn dimensions are of no concern to the model. Please see my comment a few pages ago regarding the THAM12 design. If one increases the height of the cabinet, holding all other areas constant, then one only changes a single variable in the hornresp design. Experimenting with this it seems that I gain some low end extension by increasing cabinet height allowing for a longer horn, but get diminishing returns beyond 3 to 4 inches. My question was not whether or not this is true, it is, rather, it's whether or not I was overlooking anything else. In other words, it appears to me that my modification would adapt the design more to my liking without compromising any aspect of the fold.
Regards,
gs
Once I saw that they substituted a PR alignment for a vented alignment, I stopped reading. The test is IMO invalid - they should have tested a realistic vented alignment with that driver, i.e. one where they either had to implement a massive vent to reduce compression effects (which would have in turn increased the box size), or one where vent size is compromized (as is the case with the majority of built vented alignments).
And even if you have managed to deal with vent compression effects, there's still the compression caused by the increase in voice coil resistance due to heat to be dealt with.
Sorry, but most hits of house I have to play have nothing below 50Hz. Here is an exemple with spectral content frequency of Black Eye Peas I've got a feeling :
As you can see, there's nothing to reproduce below 50Hz. Even you have a 30Hz PA system, it's change nothing!!! So a 50Hz -3dB is perfect for this type of music
If I worked in a club, I would prefer a 40 or 30Hz PA system, because acoustic is supposed to be good, and music isn't just over compressed commercial tracks with nothing below 50Hz. But mobile DJ is another work, and in this way, I repeat again, MTH-30 does the perfect job for this, and I don't think it's a coincidence if the MTH-30 is one or if not the most used DIY bass cabinet by mobile DJ in europe.
!
I've recently listened to a good amount of pop dance music on my 15" HO's configured several different ways:
- 26hz 8th order high pass
- Ports plugged and eq'd to get usable response to 20hz.
- Various other lower order high pass, 25 to 30 hz.
There is most certainly intentional content below 40hz in about half the current pop dance music out there, and in most house remixes. And even below 30hz in some cases. I found that using 8th order high pass allowed the least impact to the rolloff of the low bass vs. lower order filters which had a noticeable impact to the 30-40 hz range. I get really noticable low end grunt out of them, much moreso than any common PA.
Of course plugged and eq'd it dug deeper at the expense of headroom.
I can imagine that a MTH30 would be very effective with a pair of 10" or 12" mains that have very limited bass extension below 100hz.
Hi ghettosynth,
Post #57: "... I want to develop intuition for how these parameters interact..."
The best and easiest way I have found to get a grip on what these boxes are doing is to learn Hornresp Hornresp it is a great free program that is very well supported. You may have found this already: Hornresp for Dum... hmm... Everyone - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com or this one: Simple Tapped Horn Tutorial using Hornresp
That way you can determine if what you are looking at are minor or major differences. Hornresp has been found to be an accurate tool to evaluate tapped horns. You have to be careful about getting the simulation input to reflect the physical layout; e.g.: if you increase the height of the THAM12 you will increase L23, and you will also be changing the cross sections of the horn path (depends on where you add the additional height), both changes have to be entered into the simulation.
Hope this helps.
Regards,
Post #57: "... I want to develop intuition for how these parameters interact..."
The best and easiest way I have found to get a grip on what these boxes are doing is to learn Hornresp Hornresp it is a great free program that is very well supported. You may have found this already: Hornresp for Dum... hmm... Everyone
- Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com or this one: Simple Tapped Horn Tutorial using Hornresp That way you can determine if what you are looking at are minor or major differences. Hornresp has been found to be an accurate tool to evaluate tapped horns. You have to be careful about getting the simulation input to reflect the physical layout; e.g.: if you increase the height of the THAM12 you will increase L23, and you will also be changing the cross sections of the horn path (depends on where you add the additional height), both changes have to be entered into the simulation.
Hope this helps.
Regards,
I didn't quote that as a discussion of ported designs, they are not discussing ports.......I quoted it as a discussion of some possible failings of tapped horns, as they are not as perfect as you make them out to be.
There are plenty of good resources out there on how to properly design a bass reflex port, and when done properly they mitigate the issues you bring up.
Originally Posted by sebDIY
Another point: you can not reproduce music at high levels with a flat response curve. It's common to push sub level for 12 dB or higher.
This "loudness contour" can be accomplished easier by turning up the sub level or using an equalizer and turning down the frequencies above and boosting those below the point where a "haystack" is desired.
As far as the rest of sebDIY's comments regarding the Mackie HD1502, it's "theoretical" output level is something like 10 dB higher than the measured response of 125 dB.
I actually measured 125 dB of good sounding low frequency output from the box.
It surprised me, at the time I remember thinking "this box could be used without a sub for small gigs".
At any rate, I don't care what anyone here does, but the choice is fairly simple.
If one wants poppy bass 55 Hz and up, the small THs work well, if you want low bass extending to around 35 Hz in a similar size package, use long throw low Fs drivers in a BR box using large ports.
That said, I find one large cabinet easier to move than two small cabinets, and one larger TH cabinet can give the LF extension lacking in the small TH and the upper punch lacking in the BR box.
Art
Another point: you can not reproduce music at high levels with a flat response curve. It's common to push sub level for 12 dB or higher.
A bottom boost of 6 to as much as 20 dB is common for DJs and even some live PA rigs.
This "loudness contour" can be accomplished easier by turning up the sub level or using an equalizer and turning down the frequencies above and boosting those below the point where a "haystack" is desired.
As far as the rest of sebDIY's comments regarding the Mackie HD1502, it's "theoretical" output level is something like 10 dB higher than the measured response of 125 dB.
I actually measured 125 dB of good sounding low frequency output from the box.
It surprised me, at the time I remember thinking "this box could be used without a sub for small gigs".
At any rate, I don't care what anyone here does, but the choice is fairly simple.
If one wants poppy bass 55 Hz and up, the small THs work well, if you want low bass extending to around 35 Hz in a similar size package, use long throw low Fs drivers in a BR box using large ports.
That said, I find one large cabinet easier to move than two small cabinets, and one larger TH cabinet can give the LF extension lacking in the small TH and the upper punch lacking in the BR box.
Art
Furthermore, I just happened to come across this design for a 21" ported PA sub that remains somewhat portable. This another good example of a properly designed bass-reflex box.
Data-Bass
Here is one of the designs that inspired me to go the ported route:
Q15 Compact 15" Bass bin - Speakerplans.com Forums - Page 1
Hi ghettosynth,
Post #57: "... I want to develop intuition for how these parameters interact..."
The best and easiest way I have found to get a grip on what these boxes are doing is to learn Hornresp Hornresp it is a great free program that is very well supported. You may have found this already: Hornresp for Dum... hmm... Everyone
That way you can determine if what you are looking at are minor or major differences. Hornresp has been found to be an accurate tool to evaluate tapped horns. You have to be careful about getting the simulation input to reflect the physical layout; e.g.: if you increase the height of the THAM12 you will increase L23, and you will also be changing the cross sections of the horn path (depends on where you add the additional height), both changes have to be entered into the simulation.
Hope this helps.
Regards,
Yes, absolutely. At first I was just going to build something, but I took precisely that path, along with a tutorial somewhere on the net, to do what you are describing. You're right, of course, increasing the height requires some care in how one deals with the horn cross sections, particularly in the front of the cabinet. I was not ignoring this detail, however, it's not clear to me that some imprecision here would not be dominated by the additional height. I don't know this, I'm making this assumption based on my reading so far.
I'm not rushing out to build this, of course, I'm trying to build up my understanding first. As turbodog points out, either the THAM12 or the MTH30 built as is would add significant low end extension to my small 10" tops, but, if I could adapt either design slightly to lower f3 somewhat, they might be even more useful to me.
I just want to add, regarding the 15" tops, that for me, they are not a solution. In fact, I had initially planned to go that route and simply not bother with subs for small gigs. There are numerous problems with this approach, however, including that I didn't like any two way 15" cabinets that I listened to and three way cabinets are large and/or expensive. For my purposes I considered both the PRX635 and the Line6 cabinets but both are too heavy/large for those times when I wouldn't need even that much low end and too expensive for those times when I need a speaker in a harsh environment. Obviously I could take them, but I'd be far too concerned about them. Of course, I could purchase those in addition to the small altos, but I see no advantage to that, small subs are a much cheaper option and give me more flexibility.
So, I have two cheap decent speakers that meet my needs, alone, for many simple "gigs" where I need portable sound; adding some small (reasonably priced) subs to that, I can use those speakers for even more gigs that I would normally have to rent a truck/van for in order to haul out my larger (still small by any professional standard) setup. For these speakers, weight and size matter, and by that, I mean that I'm considering each dimension. Making a THAM12 4" taller doesn't affect my ability to carry one (modulo the additional weight), but making it 4" wider or deeper might.
The MTH30 is much larger than the THAM12, but people seem to prefer the MTH, is this largely due to ease of building, or is there something that I'm not seeing in the simulation comparisons that suggest, to me, that they perform rather similarly?
Regards,
gs
And if one wants poppy bass and some low extension but willing to compromise on both a bit with an f3 of between 40 and 45 hz in a box that isn't much wider than a 12" driver, then my sense is that one should still choose the TH, please correct me and point me to any suitable design if I'm wrong. Is this not especially true if power is also a concern?
Perhaps a large part of my value perception is more related to how practical matters drive designs as opposed to what is actually necessary. 12" TH designs are often nice little rectangles where as BR designs are often big cubes; I suspect that this is done to maximize the relationship between surface area and volume which minimizes weight and cost; I don't actually know here, I'm just guessing. So, 12" BR designs based on one driver, EV ZX sub, etc., don't have an f3 of 35hz because the boxes aren't large enough because they're made at a size appropriate for the 12" driver. Moreover, if you're going to make the box larger, you'd still want a cube-like box so you might as well use a 15" driver?
Further, ease of construction is important to me. Isn't it the case that if I did make a more rectangular BR design that it would require more bracing than a cube? The TH design naturally braces the long dimensions of the rectangle. The bracing in the 15" design shown above appears to use irregularly shaped L sections. Ok, that's not too hard, I've got a jig-saw, but it's the sort of thing that adds time to construction and may not be as cut and dry as the bracing in a TH design.
If I'm way off base here then any links that would help clarify trade offs would be much appreciated.
I would sometimes agree with this, but for this system in particular, I want smaller cabinets because the trade off will often be one small vs one large as opposed to two small vs one large.
Regards,
gs
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The only link you need to clarify tradeoffs is Hoffman's Iron Law, which applies to TH as well as BR.
TH require more cabinet volume to go as low as a BR, but can be about 6 dB more sensitive.
Cost savings at the expense of size.
In general, larger drivers need larger boxes to go low, the 15" cone area sensitivity advantage over a 12" may be negated when put in a small low Fb BR.
As far as ease of build, little difference between the two small TH under consideration.
On paper the two TH cabinets perform quite similarly.
The Tham 12 is really a good compromise between small size and high output with low power.
Given the compromised LF of both designs, I'd go with the smaller of the two.
That said, a BR is easier to build, the shape matters little, and you could maximize cabinet volume specifically to fit in available space in your car, generally harder to do with a folded horn.
The larger the panels in any cabinet the more bracing required.
As a DIY you can also go with a lower tuning and use better drivers than the typical PA subs aimed at people that don't care about LF, they just want to get the kick drum as loud as the bass player for as little money as they can get by with, a good chunk of the money spent going to convince them that some tiny cabinet with a crappy driver will somehow produce awesome bass.
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If going with the THAM 12, I suggest paying a lot of attention to the bracing in the first fold. Don't do like what I did with my THAM12 lookalike and think you can get away with making the external panel removable and mount the driver through the hole. Two layers of 3/4 ply AND metal bracing inside and that panel STILL vibrates, enough to toss one of my tops off of it when I turned the bass up during the last "war volume" test.
Which reminds me of another advantage to THs that don't show up in the sims - all that wonderful free side-panel bracing that comes as a result of folding a horn into a box
.I wonder why MLTLs are not being considered? They're basically a cross between TL and vented, and offer some of the advantages of both alignments. I'm considering one now for my PA310, which on paper seems to offer similar LF extension to my TH with the same driver, but in a smaller box and a slight decrease in efficiency. The major plus to the new design is I'll be able to get both the MLTL and my tops into the back of my car
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I wanted to avoid building another box just for this one test. Sue me! All 4 of my bass reflex test enclosures are PR so I can vary the tuning from about 15-45Hz. You are correct that there would certainly be vent compression if using a port. That little 12" could really use a 6" aero port. It would have been impractical to tune so low with a vent in that small of an enclosure as well. Still assuming that the bass reflex is an ideal scenario with a very large flared vent it is an interesting comparison.
Truthfully it would be more interesting to do this comparison with cabs having a more typical alignment with a 30Hz tuning. I could do it with my 21sw152's with the cabs that I have but it is a lot of work and a PITA.
Another interesting comparison on the other end of the spectrum would be various alignments of the same external volume and low corner using the same driver.
LOL. You could replace the PRs with MDF disks cut to the same diameter and screwed into place. Then use one of those disks to host the vent. If it's too long, mount it externally
One of the interesting studies I've seen suggests the use of a vent that looks like the nozzle for rocket in order to reduce compression effects. Basically taking the concept of flaring almost to the extreme.
Might be difficult to get that in practice. To get a flat response in different alignments with the same driver may require different box volumes, and trying to achieve the same target F3 is going to make it even more difficult.
I guess you could try a TH compared to a BR with the same Fb where the vent for the latter is sized such that the total box volume works out to the that of the TH, but I'm going to bet that's still going to be a bit difficult to actually achieve.