Rear deck vs. closed box

[presscot]

I acquired a pair of old subwoofers, MB Quart model QM340CX, size 10 inches. I'm deciding what type of cabinet to make. Having looked at old car audio magazines, because the subs are quite old, I found that in the past they used to install the sub in a suspended way (or maybe called an infinite baffle?), that is, attach it to the underside of the rear speaker panel without using the cabinets. Because the subs I got were designed and made in that era, should I install them that way? (I think the subs at that time were probably designed to be mounted on the rear deck/ infinite baffle style) How does the sound of a suspended system compare to a closed cabinet? Please give me some advice.
P.S. Here are their parameters. I tried putting them in the cabinet design program (BassBox 6 Pro) but there was no infinite baffle option available.
Impedanz 4 Ohm
Re 3.4 Ohm
fs 44.2 Hz
Qms 8.51
Qes 0.77
Qts 0.71
Le 0.89
Vas 55.8 Liter

 

[Perry Babin]

I would have thought that you'd have had at least a few replies. I'm not a speaker guy so I made a quick search and according to the Emininence site:

Qts of 0.7 or above indicates suitability for free-air or infinite baffle applications.
https://eminence.com/pages/support__understanding-loudspeaker-data

Whether they work well in the rear deck will likely depend on the vehicle. I remember the second generation Camaros making surprisingly good bass with nothing more than a pair of 6x9s. If I remember correctly (questionable), four Sony L10s across the back deck were just about the best you could get in the 70s. Other cars produced very little bass, no matter what you did. You also have to have reasonable expectations.

 

[mattstat]

there was no infinite baffle option available

That's typical. If you want to model it, just use a sealed box of very large size. How large? There's no firm cut-off, so start with something huge, then back it down until you start affecting the Fc (resonance frequency of closed box system) and roll-off.

The quoted text in the first link refers to raising Fs, but that should be Fc (or Fb depending on whose software/text). Also, Qts in this passage should be Qtc or worded differently to make these things a little clearer. Fs and Qts are specifications for the driver only. When you are talking about the system, a different term is normally used.
https://www.diyaudio.com/community/threads/at-what-point-is-the-baffle-infinite.46987/
"If the volume of the Closed Box we end up with is equal to the speaker's Vas, then both the Qts and the Fs will be raised by a factor of 1.4, as the above equation illustrates. Plug the numbers into the equation above, and that is the answer you arrive at. That is fairly significant, but not near what most Closed Boxes do. Most Closed Boxes are built with the box volume only a small fraction of the Vas, with Qts and Fs being raised higher than 1.4.

If, however, you make a Closed Box with a box volume 25 times the Vas, then your Qts and Fs will be raised only by a factor of 1.02. That is a fairly insignificant factor. An Fs of 30 Hz will be raised only to 30.6 Hz, A Qts of 0.40 will become a Qts of 0.408."

https://www.avsforum.com/threads/infinite-baffle.2426698/
"You want a minimum of 4x VAS and preferably over 10 x VAS in volume for the enclosure to act as an infinite baffle. It will model like a very large sealed enclosure. Advantages include very low power requirements to reach full excursion."

should I install them that way

Depends on how you are trying to use them.