NEW 1.2TL's need break in?

[rduval]

Strange as it sounds...I just bought a pair of NEW 1.2's. They have been stored since new, these are the ones from Ebay about a month ago. When they arrived you could tell...they ARE brand new. Boxes, spotless, everything

They came with the TL upgrade kit complete with new crossovers, documentation, etc, which I installed.

So here's the scoop..

I have had (and still have) a pair of the original (non 1.2's) SDA SRS's. I LOVE the bottom end of these speakers but always found the high mids and highs bite so I bought these new 1.2TL's.

Problem is the new ones sound VERY different. The highs and upper mids are much smoother, not as spikey as the originals which is great. But they don't have the same really low bass! They're punchier but the bass doesn't extend waaayyyy doooowwwnn like the originals. I have both sets side by side so I can make an A-B comparison and it's very obvious.

So, I know this sounds strange because nobody's had a "new" set in over a decade but do they need a break-in period or are the 1.2TL's just that different from the originals?

Rick

[F1nut]

If you were sitting still for the last 12 years or so, you might need to loosen up a bit before being your best. ;)

[cds]

Rick,

A thought…

Since you had to install new crossovers along with the tweeters, it is possible that while wiring all the LF drivers you may have switched the polarity somewhere putting the bass drivers out of phase in one of the speakers.

This would be similar to wiring a pair of speakers out of phase at the speaker terminals. I know it’s a pain, but you may have to go through each one and check.

Since you have the original SDAs, you could open one to double check your connections.

Let us know what you find.
Carl

[rduval]

If I remember correctly all the plugs on the crossover are polarized so I don't think it would be possible to switch them around.

I know on the tweeters that they had one large and one small terminal so I didn't screw that up for sure. I didn't actually have to unplug any wires from any speakers other than the tweeters so I can't see that as being the problem but I'm going to pull the crossovers just to be sure.

Rick

[cds]

OK Rick, if you’re saying that the TL upgrade required just changing the tweeter section of the crossover then let’s assume the LF drivers were wired correctly at the factory.

Here’s something I came across on a “defective” pair of SDAs I looked at years ago. The plastic red and black binding post nuts will come off if unscrewed all the way. On these “defective” speakers, someone had put the colored nuts on backwards so when the owner connected the amp using terminal colors, he was wiring one of them out of phase. The label on the back shows the positive and negative terminals that should agree with the colors.

[hoosier21]

Or just play them for a while and let them break in.

[RuSsMaN]

heh heh heh

[Tour2ma]

Is the comparitive set up fair? That is are both the 1.2's in or outside of the SRS's?

[RuSsMaN]

Why would it matter?

Stereo image, etc, sure - but low bass response - nah. He could set them in the middle of the room facing each other, and they should have decent low end.

BIG waves brotha, Tsunami style.

Cheers,
Rooster

[Tour2ma]

Two words: Corner loading...

[rskarvan]

Rick,

I ALMOST bought these speakers out from under you. (I know I saw them first - I hestitated). You got a FABULOUS deal there. If you become unhappy with the 1.2TL's, let me know. I'll take them off your hands.

- ronskarvan@aol.com

[cds]

Two words: Corner loading...

Yes, that was another thought. Back in the days when audio magazines tested SDAs, I remember some reviewers commenting that the low end was very position sensitive. Something like if they were too close together the bass would mask the higher frequencies and if too far apart, the bass would disappear.

Because room placement can be a big factor, have you swapped the positions of your original SDAs and the TLs? If it is room resonance related and you accurately relocate each pair, the symptom should transfer to the older set.


Cheers

[rduval]

Ok...to reply to eveyone at once...

Actually the binding post caps WERE reversed and I fixed it according to the labels on the back...

...They are set up inline, 1.2TL's on the inside 5ft centre to centre, originals on the outside with 1" between the old and new. Both pairs 1ft from the back wall and both have spikes...

...Corner loading, true but even at low levels the difference is painfully obvious so I don't think that corner loading would be the culprit. I do agree that there is a bass sweet spot from a placement point of view. and neither pair are in it at the moment because both are equally as close to it as possible...

Damn I'm frustrated by this!


Rick

[Tour2ma]

How far are the SRS's from the corners? I'd swap either the left or right 1.2 and SRS.

That said, seems we skipped some basics along the line like:
- are all the MW's in the 1.2's functioning?
- are the 1.2's well sealed so their PR is in fulll play?

Probably others that are even more potentially insulting... Sorry if I did, but I'm feeling your pain...

[cds]

Rick,
Disconnect the SDA cable and reverse the polarity on one of the new ones.

Does that make the bass better or even worse?

Carl

[madmax]

To save a lot of effort looking for the correct polarity on all the woofers take a little 9V battery and with the speaker completely disconnected from everything else connect the + side of the battery to the + side of the speaker and - side of the battery to the - side of the speaker. The 4 inner speakers should pop out about 1/8th inch or so. Check both speakers.
madmax

[bikezappa]

Fuck'in A relpy Madmax. I will remember that trick.
Simple
Quick
Accurate

[dorokusai]

I did that battery trick and heard music.....

[madmax]

The battery trick is quick, easy and safe. It does assert a 20 watt pulse onto the woofer if it is fully charged (new) so obviously on higher power speakers it can cause no harm. I have used it on the smallest of speakers without harm as well. As for the tweeter it will only make a small click because the series capacitor will block the dc voltage. (the click only happens when you charge the cap, afterwards you will not hear it).

This is only a guess but I bet if he hooked up the SDA cable the SDA speakers in the opposite speaker would pop in when you touch the battery terminals.

madmax

[Tour2ma]

Originally posted by dorokusai
I did that battery trick and heard music..... Then you're improving since most of the time you just hear voices...


(Damn you're on a roll... )

[cds]

A 9 volt battery will work, but it doesn’t have much current capacity driving into a low impedance load. Across that kind of load, the actual voltage probably drops to a couple volts.

In a pinch, I’ve used an alkaline 1.5V AA, C, or D cell. A good cell will easily drive the cones out and the voltage is not high enough to cause any driver issues.

BTW, in the 1.2’s and 2.3’s both the Stereo and SDA arrays are DC coupled to the binding posts. Therefore, all the MW drivers will move forward if the battery is connected + to red and – to black.

If the results are the same in both speakers, the internal crossover phasing is correct

[madmax]

Originally posted by Tour2ma
Then you're improving since most of the time you just hear voices...


He only hears the music when he connects the battery to his head, not the speakers. (just wanted to clear up this one point).

[rduval]

Ok, here's where I'm at...

I thoiught I'd try swapping the crossovers..just to see if the bass followed the crossovers. Unfortunately the original do not have plugs like the 1.2's & TL's, everything is soldered onto the board so it's no so easy. To complicate matters the slip on lugs for the tweeters are different so I stopped there for a moment.

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?

Also the original crossover is massive compared to the 1.2's. It barely slips through the access hole! That's got to have something to do with the sound! Not that size alone matters, just that they are very different.

I think the next step for me is just to try the TL tweeters in the originals. Anybody done that? Any comments?

One positive note for anyone who folloed the old thread regarding using 2 carver M1.0t's in mono mode, you'll remember that the feedback blew them both up becuase they are not common ground. Somebody suggested that running a common ground cable betweeen the negative terminals might do the trick...it did! That's all I needed to do..$500 lesson to repair them but they're great now.


Rick

[Tour2ma]

Glad to hear about the amps...

Your comment on the bracing really surprises me. One of the things I have read here is how much Polk improved the stiffness of their flagship model as it progressed from the SRS trhough the 1.2 to the 1.2 tl. I always took that to mean more and better bracing... Just doesn't jive with you're observations.

Please post some pics if and when you can...

[cds]

The bracing observation is interesting. I suspect Polk determined that the benefit realized with the original bracing would not be noticed by most users and reduced it in subsequent cabinets as a cost cutting measure. Funny, I’ve never seen the original cabinet but adding more bracing on the newer models always came to mind whenever I’ve had them open.
Any difference caused by cabinet wall resonance would be noticed at higher volumes but it would not cause a lack of bass. At low volumes cabinet bracing should not be a factor.

The difference in the crossover is also interesting but I also suspect it may be a result of design refinement. For example, earlier SDA designs contained more “stuff” because Polk originally had the dimensional function using both woofers and tweeters. Later versions eliminated the tweeter portion of the array.

I don’t have access to a schematic of the original so I can’t compare it to the newer models, but I don’t think I’ve ever read a review on the 1.2 models that noted a lack of bass. There has to be something else wrong.

Do you have access to any type of signal source other than music? If not test equipment, how about a test CD with tones? If you could play a steady 30 – 40 Hz tone and observe the amplitude of the woofer cone movement at a specific volume setting, that may help.

Have you done the battery test and compared the cone movement of the two versions? There should not be much difference unless one of the new crossovers is screwed up.

Another little detail is that the cabinet should be sealed. A significant air leak somewhere will effect the low frequency response. Did you install gaskets under each tweeter? You should also be able to compare the cabinet air seal by pressing a MW driver down, releasing it and comparing how quickly it returns to the rest position. If it snaps right back, there is an air leak in the cabinet. Obvious leaks spots are the bass brace and 4 mounting feet holes. Be sure things are screwed in to them.

Keep us posted.

[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?

On the crossovers, there are an extra 4 or 5 larege electrolytic caps and the coils, and as you can see 2 of the coils are MUCH bigger. Maybe it's same amount of wire, just a larger form?

I haven't done the battery test yet, just haven't gotten around to it but I will. I'm reasonably confident that they're ok though. It's not that they lack bass, they have LOTs of puch it's that what they have is upper bass where the originals have low, ground rumbling, rattles your teeth out bass. Subwoofer bass. It's smooth and it's sweet and it goes waaaaaaaaaay down. I really wish the old crossovers had the plugs like the newer ones, it would have made it so easy to try.

Cabinets are as well sealed as the originals. If you press in on the bass radiator all upper drivers come forward. If you hold the bass radiator until the 6" normalize then release it take about 3 or 4 secs to come back, about the same as the originals.

I'm beginning to wonder if the really low sub-bass was deliberatly tuned out of the speakers in the later models to prevent damage by under-powered systems?

Rick

[rduval]

Oh and for those interested I've also included the pic of my current setup so you can see how everything's layed out. The old ones are on the outside, the 1.2TL's in the middle.

Rick

[hoosier21]

how much have they been played? I mean has your original question about break in been ruled out?

[wallstreet]

Just leave em just like that.:eek:

[rduval]

OK!!! SOME SUCCESS!!!

1) I did the battery thing...SOB..they were reversed! So I changed the colored caps but when I get a minute I'm gonna fix them in the cabinets..so far so good.

2) Found out the when the negatives of the 2 carvers are bridged YOU GET MONO! SERIOUSLY! I had to bridge them for the old ones but since the 1.2's have the transformer interconnect I don't need to. Wow, soundstage really opened up.

3) Since I was screwing around with the cabling I changed the speaker cables from the Monsters I was using to the AudioQuest Slates I had bought. WOW WHAT A DIFFERENCE! Bottom end opened up, mids were sweeter, etc. The 1.2's still aren't quite as full as the originals but they're close.

So right now...I'm pretty happy...sorry to disappoint all of you who sent me private emails offering to buy them ;) .

Only problem at the moment is that one of the Carver 1.0's that I just had rebuilt started making a crackling sound so I'll take it back tommorow to get them to go over it again so I'm running on one amp now for the right "pair" (yep I'm running all 4 at the moment but the old ones are only the bottom end since the 1.2's are so much sweeter...) and I'm running my 1.5t for the left.

Anyway...thanks so much for everyones help...couldn't have got it sorted out without ya...

Rick

[cds]

Rick,
Gee, I wish I had a main speaker setup that looked like that.... Dream on.

From your picture, the originals are on the outside and closer to the wall. As any pair of speakers approaches the room corners, the boundary / corner effect becomes more pronounced.

If you had posted your picture stating you had two pair of identical brand X speakers as shown and asked which pair would produce higher levels of bass, the answer would be the outer ones. They are nearer the corners and thus benefit from room boundary reinforcement. If I were doing a speaker response test using a SPL meter in your setup, I would expect higher levels of low frequency from the outer pair…. all other things being equal.

Question, have you swapped the TL’s to the outer position?
It may be that both are producing nearly the same low bass amplitudes, but the room boundaries are reinforcing it better with the originals, and the result is more “shake the floors and your bones” bass. Room tuning via speaker placement can be really critical in some installations.

Without a schematic of the original crossover it’s hard to speculate what the difference represents. The larger coils could simply be the fact that they are wound with larger gauge wire. This should not be noticeable at low frequencies unless you are testing them at very high volume levels.

The crossover should be out of the picture for really low frequency because it is DC coupled to the drivers.
A quick check with the battery should show all 8 drivers moving forward or backward. If for example the SDA connection in the crossover were open in one of the TL’s, only the 4 stereo drivers would move forward with the battery. At very low frequencies, this would reduce your effective cone area.

Also, if one or more of the 6.5's were wired out of phase, that would screw up the low end. If they have the same size spade lugs, it would be easy to do.

Your check for cabinet leaks sounds fine, and since the cabinets are the same size, the only other “tuning” variable effecting low frequency would be the response characteristics of the 6.5” drivers and the passive radiator. Polk could have changed something, but since they don’t disclose the individual driver specifications you would have to swap all the 6.5’s and the radiator to see.

The easiest experiment at this point would be to:

1) Check each TL with a flashlight battery to verify all the 6.5 drivers are functioning in phase and

2) Swap the speaker positions, placing the TL’s on the outside.


If you lived closer, I’d offer to drive over and get those crummy TL’s out of your hair. Hey, why not put the SL3000’s and crossovers in your original SDA’s and have the best of both worlds? Then sell all the rest of the bone pile to me for scrap…. Well I can dream can’t I?

Cheers

[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... :D 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...