HSU VS JTR

[lovinthehd]

Just seems like a too small allowance off the top of my head and don't remember what mine are but pretty sure larger than .15 cft, would think your driver displaces more than .15 cft too; I suppose there isn't an entry for the specifics of the driver if it just allows 4% for such.....

Not that it makes a huge difference.

 

[TLS Guy]

Don't see a Vt in the spec he posted....and if it is meant to be V(total) as in the spec, that makes no allowance for the driver.

Vt is V total. Vb is the optimum air volume in the box. for a sealed alignment that is before stuffing is added. Vt is Vb plus driver, bracing ports etc. There are no ports in a sealed enclosure. Only the designer/builder can know the true Vt as the program can not tell how the box will actually be built. It can only give Vb plus driver displacement assuming that is known from the data entered.

 

[TLS Guy]

Isn't Vt the Total inside volume NOT taking into account the driver and Vb the inside volume taking into account the driver? In the specs, the Vt (3.864 cu.ft) is larger than the Vb (3.715 cu.ft)...

You said that I can add Eq to this ported design.. but it's not a ported design. it's sealed....

"You need to add back the volume of the bracing" This goes back to my original question, adding an inch to the L W and H would account for bracing and some. Do you think this is ok or should I stick with the exact specs in the file that I posted?

I wrote ported in error. I have corrected it. You can only Eq a sealed design and not a ported one.

 

[TLS Guy]

Just seems like a too small allowance off the top of my head and don't remember what mine are but pretty sure larger than .15 cft, would think your driver displaces more than .15 cft too; I suppose there isn't an entry for the specifics of the driver if it just allows 4% for such.....

Not that it makes a huge difference.

If the driver volume was in the data base, or entered correctly that will be right. A driver has a lot of open air. It is magnet plus the rear ribs. The cone is at most a cone, but it is almost always a truncated one, or not even a truncated cone, and has a profile much more shallow than a cone.

 

[Alex2507]

You can only Eq a sealed design and not a ported one.

After disconnecting the plate amps, I found my ported subs to benefit from EQ'ing.

Am I missing something here?

 

[everettT]

After disconnecting the plate amps, I found my ported subs to benefit from EQ'ing.

Am I missing something here?

The plate amps probably employed at least one filter, the low pass of some sort. Could have also had a slight boost at 25hz or there about.

 

[TLS Guy]

After disconnecting the plate amps, I found my ported subs to benefit from EQ'ing.

Am I missing something here?

Well may be, may be not. What we are talking about here is using Eq to increase bass extension. A sealed sub never decouples from the box obviously. A ported sub on the other hand only has its cone excursion limited by the resonance, and where this resonance occurs is pretty much defined by the T/S parameters of the driver. So below resonance a ported box is just an open box. If you try and Eq to extend the bass then you just get useless cone excursions and no output. These cone wasted excursions can and do damage drivers, and cause a dramatic rise in distortion.

So in a ported design, F3 will be what it is and you can't change it. In a sealed sub you can add Eq to the inverse of the bass roll off which is 12 db per octave, as long as the driver does not run out of linear excursion. Since in the operating range a driver for a ported sub does not need a very high xmax, A driver for sealed application needs much greater xmax and ability to handle power and will be a much more costly proposition.

Now we get to the issue of which system produces the cleanest bass.

Well you can get good bass extension from a low Q driver in a sealed enclosure, and end up with an acceptable Qtc, if the design is done optimally, and you don't go for F3 lower than is wise, as commercial designers so often do.

For sealed if you choose a low Q driver you will have a very high F3, before Eq. You then have to apply so much extra power the design becomes impractical. So in my view in both good and practical sealed and ported designs, Qtc ends up about the same. So the only advantage of the sealed design ends up being much smaller cabinet volume, but at the expense of much greater power requirements and therefore cost. Iron mans law kicks in and always will. So the ported design will always be the cheaper to implement.

Now you see why I like TL designs, as you can take a low Q driver and still get bass extension and low Qtc without high power drive. The penalty however is a large increase in enclosure volume with a strong dominant dimension depending on the orientation of the pipe, vertical or horizontal.

 

[moves]

"You need to add back the volume of the bracing" How do I do this?

This goes back to my original question, adding an inch to the L W and H would account for bracing and some. Do you think this is ok or should I stick with the exact specs in the file that I posted?

 

[TLS Guy]

"You need to add back the volume of the bracing" How do I do this?

This goes back to my original question, adding an inch to the L W and H would account for bracing and some. Do you think this is ok or should I stick with the exact specs in the file that I posted?

Well you calculate the volume of the bracing and add it to get the final volume. So your final volume should be the Vt in the spec sheet plus bracing volume and plate amp if you use one. This should be really simple stuff. I'm having a hard time understanding the confusion. I thought I had made this clear, but obviously not.

 

[moves]

Well you calculate the volume of the bracing and add it to get the final volume. So your final volume should be the Vt in the spec sheet plus bracing volume and plate amp if you use one. This should be really simple stuff. I'm having a hard time understanding the confusion. I thought I had made this clear, but obviously not.

Obviously not.... I just want to double check that increasing the cabinet size dimensions (LWH) is the way to account for bracing... it seems obvious but I've never done this before so sorry to frustrate you with my questions.

 

[moves]

So your final volume should be the Vt in the spec sheet plus bracing volume...

In order to get Vt with bracing is to increase the cabinet size by the amount of the bracing volume... Correct?

 

[TLS Guy]

Obviously not.... I just want to double check that increasing the cabinet size dimensions (LWH) is the way to account for bracing... it seems obvious but I've never done this before so sorry to frustrate you with my questions.

I'm not frustrated, but just trying to figure out what I have to do, to make my posts easier to understand.

So yes, the bracing displaces air, and so the only way you can add back the air is to increase the dimensions of the box to compensate.

 

[moves]

I'm not frustrated, but just trying to figure out what I have to do, to make my posts easier to understand.

So yes, the bracing displaces air, and so the only way you can add back the air is to increase the dimensions of the box to compensate.

Perfect thanks that makes it clear for me. Just double checking.

 

[moves]

Well may be, may be not. What we are talking about here is using Eq to increase bass extension. A sealed sub never decouples from the box obviously. A ported sub on the other hand only has its cone excursion limited by the resonance, and where this resonance occurs is pretty much defined by the T/S parameters of the driver. So below resonance a ported box is just an open box. If you try and Eq to extend the bass then you just get useless cone excursions and no output. These cone wasted excursions can and do damage drivers, and cause a dramatic rise in distortion.

So in a ported design, F3 will be what it is and you can't change it. In a sealed sub you can add Eq to the inverse of the bass roll off which is 12 db per octave, as long as the driver does not run out of linear excursion. Since in the operating range a driver for a ported sub does not need a very high xmax, A driver for sealed application needs much greater xmax and ability to handle power and will be a much more costly proposition.

Now we get to the issue of which system produces the cleanest bass.

Well you can get good bass extension from a low Q driver in a sealed enclosure, and end up with an acceptable Qtc, if the design is done optimally, and you don't go for F3 lower than is wise, as commercial designers so often do.

For sealed if you choose a low Q driver you will have a very high F3, before Eq. You then have to apply so much extra power the design becomes impractical. So in my view in both good and practical sealed and ported designs, Qtc ends up about the same. So the only advantage of the sealed design ends up being much smaller cabinet volume, but at the expense of much greater power requirements and therefore cost. Iron mans law kicks in and always will. So the ported design will always be the cheaper to implement.

Now you see why I like TL designs, as you can take a low Q driver and still get bass extension and low Qtc without high power drive. The penalty however is a large increase in enclosure volume with a strong dominant dimension depending on the orientation of the pipe, vertical or horizontal.

F3 on the cabinet I am thinking of making is 32.04 Hz... is that considered high?
The Qtc is 0.707

Just wondering if there is a better sealed design that I should consider for this driver. Thoughts? The 2 subs will cost me about $2500 CAD so I just want to make sure that I can make the best cabinet with the right volume that I can. Thanks for your help.

 

[moves]

There is also this cabinet design that was sent to me:

 

[Alex2507]

F3 on the cabinet I am thinking of making is 32.04 Hz... is that considered high?

It's a lot higher than the seven cubic foot 19 Hz coffin you just linked.

 

[TLS Guy]

F3 on the cabinet I am thinking of making is 32.04 Hz... is that considered high?
The Qtc is 0.707

Just wondering if there is a better sealed design that I should consider for this driver. Thoughts? The 2 subs will cost me about $2500 CAD so I just want to make sure that I can make the best cabinet with the right volume that I can. Thanks for your help.

A sealed sub will always have a high F3 without Eq. Having to Eq a sealed sub is part of the design. You ALWAYS have to Eq a sealed sub to get the required bass extension. To get a driver to get to 20 Hz without Eq requires an acoustic transformer, like a ported enclosure, a pipe or horn.

A sealed design is always inefficient and requires a driver with high xmax that will take a lot of power to handle the Eq required.

The cabinet volume for that driver is optimal. 32 Hz is actually pretty low for a sealed sub before Eq.

The drivers you have selected are optimal for sealed rather then vented alignment.

A vented sub will be much larger than a sealed sub. If you want a vented sub you should select a more suitable driver which will be cheaper, as you don't need such a massive motor system.

 

[moves]

To get a driver to get to 20 Hz without Eq requires an acoustic transformer, like a ported enclosure, a pipe or horn.

Thanks I'll just stick to the sealed cabinet I think but oh oh.... so I have bought a 2X4HD miniDSP... do I also need to add an acoustic transformer?

 

[everettT]

Thanks I'll just stick to the sealed cabinet I think but oh oh.... so I have bought a 2X4HD miniDSP... do I also need to add an acoustic transformer?

https://www.minidsp.com/applications/advanced-tools/linkwitz-transform?gclid=Cj0KCQjw6fvdBRCbARIsABGZ-vSZzQwlIcNgf5wIV1yN_KW-3o4tf_6x2jcQqCYNRVgk3cgGUDh72pwaAnFDEALw_wcB
That should get you where your going

 

[TLS Guy]

Thanks I'll just stick to the sealed cabinet I think but oh oh.... so I have bought a 2X4HD miniDSP... do I also need to add an acoustic transformer?

You will need mini DSP.

The point I was making is that a sealed speaker only has the loudspeaker cone to actually interface with the air to produce sound waves. At low frequency, a loudspeaker cone is a terribly inefficient coupler to the air in the room, and has to be driven by brute force. Whereas pipes, and horns especially plus also tuned ports are much more efficient at coupling to the room. So the enclosure can be looked at as an acoustic transformer to interface the driver with the room at low frequencies.

So in a ported speaker at the bandwidth of the resonance the loudspeaker cone pretty much stops still and the vast majority of the sound is efficiently radiated from the port.

Similarly with a TL, at the closed end of the pipe where the speaker is the pressure is high and air displacement minimal. This occurs over a much larger bandwidth than a ported design. So there is a wide bandwidth were the cone movement is very low and radiation of sound is from the port. This couples very efficiently and pipes are able to cover the room in a very uniform fashion. This is what organ builders call the encircling property of pipes.
This is really notable as a massive difference between a true pipe organ and an electric one producing sound from speakers. The true pipe organ has a highly uniform loudness throughout the room. This is why it enhances singing and supports the congregation to sing lustily. An electric organ on the other hand is much louder close to the speakers and does not support congregational singing nearly as well as a well designed and built pipe organ. That is a property that makes the sound of my TLs in the room very different from other designs.

The most efficient way to couple a speaker to the room is a horn, where the pressure between driver and throat is enormous and sound output from the horn mouth loud. in compared to the output from the loudspeaker driver.

So the point is speaker designs other than sealed act as acoustic impedance transformers to drastically improve the match between driver and room. If it were not for the size advantage you would absolutely never entertain the idea of putting a loudspeaker in a closed box. You would reject it out of hand!