The TD8M and TD6M are not quite available yet. We have done them in small quantity but are finalizing some things to get them into normal production. They will be great options when available. The TPL150H is going to be the best option at higher SPL. The Raal is a good option as well. The Mundorf is likely the best option available in terms of sound quality.
Forum Replies Created
stryke on August 3, 2015 at 11:58 pm · in reply to: TD15H(+) + JBL 2447/2380, WAS : TD15H(+) + BMS 4590/4592 #11448
The JBL2231A was a good woofer in it’s day. Since then, many things have improved. Based on the 190L enclosure, the TD15H-8 will be a good drop in upgrade.The lower end of the response curve and overall efficiency will be nearly identical. That is where the comparisons really stop though as the TD15H is far superior in many ways.
The TD15H has 14mm Xmax vs 5mm for the 2231A. This means it will give nearly 3x the volume displacement, or low end output equivalent to almost 3 of the 2231A. In the a 190L enclosure tuned just over 20hz, the 2231A reaches the 5mm rated Xmax at 32hz with only 82W input. This gives a max SPL of 109.6dB at 32hz. The TD15H will not surpass the Xmax until 650W input power and reach 118.3dB at this same 32hz in the same enclosure. Very significant.
The TD15H also has much better upper end response. Inductance of the 2231A is 1.4mH while the TD15H is only .3mH. Not only is the inductance low, but it is linear and does not change with excursion. You can read all about the benefits of the motor with Full Copper Faraday Sleeve below if you have not yet. The 2231A has nothing to address flux modulation or linearize inductance. This is a HUGE upgrade to go with the TD15H over the 2231A.
The TD15H+ we will not be making now due to some parts issues. It was more for pure subwoofer use though so is not ideal for your application anyway.
There is really no issue with tuning below the driver Fs. The compliance of the system is determined mainly by the enclosure so the free air resonance of the driver is not all that significant. The 2x TD12X in 11cf tuned to 20hz looks quite good with a gentle sloped response. I would put a highpass filter at about 18-19hz to prevent over excursion below there. If you do that you should be within Xmax limits to about 800W input to the pair.
If you can hear something rubbing, chances are that something got into the gap. If it is non-magnetic it is typically easy to get out, especially if it is on the ID of the coil. If it is outside the coil it is harder. If it is anything that can be held in with the magnet it can be extremely hard to get out.
Have you checked to make sure the phase plug is screwed down tightly? They just thread onto a 1/4-20 set screw in the middle. If it is tight, I would take the phase plug out and go around inside the gap with a piece of paper to see if there is anything in there. be careful as there is a split in the kapon former. You don’t want to get the paper caught in the split. Look for any marks on the phase plug. Blow out the gap with an air compressor. Also look for anywhere that the spider may be unglued.
Are you powering both sets of voice coils on each woofer? On a dual voice coil woofer, if only one set of terminals is hooked up, you risk damaging the woofer very easily.
While this looks nice, I would suggest against it. While they are used in this configuration often, no woofer is designed to play up or down firing. Gravity has an initial effect of creating a sag that can be calculated based on mass and compliance. There is also an additional amount of sag that occurs over time as the suspension becomes more permanently biased. Biased suspension voids any warranty in the industry. Not to mention that the acceleration of gravity creates a slight non linearity between the coil’s acceleration on the upward and downward stroke.
If you are going to do it, you could have from 2-5 cubic foot per driver. The larger the box, the less power you need on the low end. I would ideally keep about 3″ from the woofer to any surface.
Simon was nice enough to help out with forum questions for years. He contributed to the forum and lot and was very much appreciated. He got busy with other things since then and I hope he is doing well.
There will be only a small difference in the Qtc of the system. The isobarik design can help with motor non-linearity and inductance non-linearity. Both of these are already addressed in the motor design of these woofers though. Any benefit of the isobarik mounting will be small compared to the lowering of distortion you will get from using more drivers. Each woofer has to move only half as far for the same SPL level then which is a massive benefit for lower distortion.
Take a look a the modeled curve included. If you have 4 drivers with 4x Vas, there is no concern over things being boomy. Realize these are drivers with a large Vas already so this is less critical than a driver with much smaller Vas. Also a room is not air tight, will have leaks, and walls are not fully rigid so it won’t model like it is exactly the size it is.
You say you already have 8 drivers. If you had around 7000L you could easily fit all 8 in with 2x the Vas. Qts is around .73 assuming the room is perfectly sealed and air tight. This is very close to the Qts of .7 of the driver. You can never go lower than that. With 2x the Vas you are already getting very close to “infinite” numbers. This is a well damped system that will not be boomy at all.
In reality the room will appear even bigger because there are doors, windows, duct work, outlets, etc that would create losses. I know over on the cult forum they recommend the 10x Vas but it simply isn’t needed. Your main benefit will be in using all 8 drivers to get more efficiency, more headroom and lower distortion at any given SPL level.
It is very common to use the trunk space as the infinite baffle enclosure in a vehicle. In the case of the VW with the trunk being in front it could be possible. I cannot recommend cutting holes into the structure of the vehicle though as I would not want to be responsible for that. Volume wise there should be enough room in this trunk though to support the IB10AU or SBP12 though if you could make it work.
In reality, the 10x Vas number is a theoretically perfect point. In reality it is not a necessity. Here is a comparison of the IB15HT-8 modeled in red with 1x Vas, orange with 4x Vas, and green with 10x Vas. You can see that there is a big jump in low end efficiency with the increase to 4x Vas, but from there to 10x there is very minimal gain. Even down at 10hz there is only .66dB of difference.