The MB Quart QLS line is discontinued product from around '00-'03.
As some of you may know, the company was owned by Fosgate Audionics at that time. Product was called MB Quart. Fosgate made the subs for MB Quart at this time. MB Quart continued to make the mids and tweets.
Before that, it was Quart Mobile. The product was called MB Quart.
Before that, I am not sure of the product name, but it was Quart and Peerless.
They split and formed two companies. I am sure you guys have heard of Peerless.
A company called Maxxsonics purchased MB Quart from Fosgate and moved manufacturing to China. This put the guys in Germany that created such a fine product out of work. Maxxsonics ruined MB Quart, and Maxxsonics owns the rights to the brand.
The German guys got investors together, and re-opened under the name German Maestro. They are currently making some fine product. These are the guys that may have the documents you request. As mentioned, they are German. Anything I have seen in the past is in German. Personally, I have not devoted time to reading graphs for speakers. I just audition.
I have not looked for such documents due to the fact the QLS line is 10+ years old, and the fact that auditioning is what I prefer.
I may be able to find stuff on the new product, which should give an idea of their ability to build quality product.
Quart was never known for their subs, which is why Fosgate took over the sub manufacturing.
Any time a member is looking for a 1k pair of speakers, or a 3k complete system, I recommend MB Quart QLS. I have never recommended MB Quart subs.
Or Polk subs, or B&W subs, or Infinity subs, yada yada. Just like in car audio, Quart was the chosen mids and tweets, and JL was the chosen subs.