NEW 1.2TL's need break in?

cds

Way to go Rick! Now I suspect any remaining bass difference may be more easily attributed to corner proximity.

rduval

I agree with the corner placement issues regarding bass but the 1.2's and in the spot that the originals WERE and the difference is still apparent.

Even at low volumes you can hear sub-bass from the originals that you don't hear from the 1.2's. I'm not a acoustical expert but I think that you'd have to have enough volume for some reflection before that would come into play.

I will check all the drivers. Mind you, if all move forward when I hookup the 9v battery to the rear terminals with the + to the + and the - to the - then they must all be in phase, is that right?

As for getting rid of the scrap...well I think i'll hold on to them for a little while yet.....:D

Rick

cds

Rick,
Believe me, you don’t have to be an acoustical expert to know when the bass is different. I believe we should get the definitive word from Polk on this. I myself would prefer a more robust low end, so if the originals have a different low end, we need to determine why.

The SRS and 1.2’s both use the same radiator but the SRS uses the same drivers for the stereo array and the SDA array (4 MW6503 each). The 1.2 models used MW6511 drivers for the SDA array. So what we need to know is how the cabinet tuning changes at very low frequencies when all 8 drivers are 6503’s. If the 6511 driver rolls off at a higher frequency, perhaps that is the difference you detect.

With samples of each I could run tests but the quickest answer may come from Polk. I always thought the changes were intended to keep the characteristics the same or improve them in subsequent models. Maybe what you and I like was not a desirable characteristic and it was tuned out.

To check the phasing, you can use a 9V or 1.5V battery and should see all the drivers move together. You can connect it either way to the binding posts, but you must connect it the same way on each. The drivers will all move in or out depending on the polarity of the battery.

To get things straightened out, I would first put the plastic caps on to match the rear panel diagram. Then test with the battery basing the connections on the cap color. Both speakers should do the same thing.

Carl

Tour2ma

Glad to read about the progress, although I did have to do it with a sore jaw as mine hit the keyboard when I saw the pic of all four... Talk about a wall of sound. :eek:

Yup, corner loading is probably responsible for the residual difference in bass, but it's really have to annoy me to lug around both pair. I do have to make a double mental note on that battery check. Saved a lot of effort there.

One thing I am curious about is: what would happen to the SDA effect if you swap the positions of one side only, i.e., reverse the right channel SRS and tl positions? The centerline of the sytem would not be the centerline of either pair... could be good.. could be awful...

I am still a little puzzled by the bracing difference you reported:

Originally posted by rduval
The only internal cabinet structure where the newer ones seem more "sophisticated" is that the internal walls are grooved into a large checkerboard pattern . This is not done on the originals. Perhaps, from an engineering point of view, this creates many "I" beams and makes the cabinet stiffer? maybe?

Are you saying there are grooves in the MDF, or that there are raised "beams" fixed to the MDF? Can you get a pic?

Thanks for the posts... and good luck with the Carvers...

DarqueKnight

Originally posted by rduval
Ok, here's where I'm at...

One thing I noticed inside the originals vs the 1.2's is that the originals have a LOT more bracing. I mean A LOT! ANy thoughts on if this has something to do with it?

Rick

Rick,

The SDA 1.2 and 1.2TL, use a "monocoque" cabinet structure. A monocoque structure is one that bears loads on the skin of the structure rather than on internal supports or bracing.

As you have noted, the original SRS cabinet has much more internal bracing than the SRS 1.2 cabinet, yet both cabinets weigh about the same (182 pounds for the SRS and 180 pounds for the SRS 1.2). The 1.2 cabinets are much heavier and stiffer than the SRS cabinets.

DarqueKnight

Originally posted by rduval
Even at low volumes you can hear sub-bass from the originals that you don't hear from the 1.2's. I'm not a acoustical expert but I think that you'd have to have enough volume for some reflection before that would come into play.

Rick

The SRS cabinets resonate more in the bass region than the SRS 1.2 cabinets. That resonance was addressed with the redesign of the SRS 1.2 cabinet mentioned in my earlier post.

In addition to the driver phasing problems you corrected, some of the bass you were "missing" was due to the much lower levels of resonance of the SRS 1.2 cabinets.

The 1.2TL was Polk's attempt to make as accurate a speaker as possible at that specific price point. Some people prefer the sound of the original SRS with all its euphonic colorations. I have both versions and like them both, but for different applications.

madmax

I have both the 1.2's and SRS-SDA as well. Side by side comparison as you are doing should be extremely close in sound. I can tell little difference in the bass region. Something is wrong. Although I have not done side by side comparisons I do know my room and speakers and have used both pairs in the same location. I do like the SRS-SDA a little more than the 1.2's but it has little to do with the bass/sub-bass. Good luck!
madmax

rduval

Originally posted by Tour2ma

I am still a little puzzled by the bracing difference you reported: Are you saying there are grooves in the MDF, or that there are raised "beams" fixed to the MDF? Can you get a pic?

Thanks for the posts... and good luck with the Carvers...

The board is actually grooved out. Pics would be pretty hard because of the angle but if you pull your sub radiator you can see it.

Rick

Tour2ma

Probably not since I have the SRS's, but if I catch your drift you're essentially saying that squares were routed out of the MDF leaving a laticework of ridges behind... yes?

rduval

Basically yes. But it's not very intricate. They're buttoned up now but if memory serves the squares are about 6"x6".

Rick

Tour2ma

Thanks... I've got the picture...