Bridging question

motorstereo

I have a pair of 1.2tl's with the 1000va dreadnaught and I'll be adding a second amp in the very near future. The amp I'm adding is a Mcintosh mc2500 to pair up with my present 2500

. There's 2 different ways to run the amp; mono bridged or mono paralleled. I'm leaning towards the mono parallel method and I'm wondering if this method will work without causing damage to the 1.2tl's and dreadnaught. Also if anyone has any thoughts on which way of running those Mac's mono'd is best (strapped or bridged) I'm all ears.

westmassguy

Bridged is for 8 ohm speakers. Your 1.2tls will drop well below 3 ohms at certain frequencies, so Parallel should be used.

motorstereo

That's what I was hoping to hear westmassguy. Do you think there will be a problem with running things as shown in the parallel mono schematic?

westmassguy

I looked at the manual, and parallel is recommended for 4 ohm speakers. Just be sure to wire them off the correct terminals. Other Mac owner may chime in. You might want to contact their customer service on Monday, just to confirm everything. No harm there.

motorstereo

Thanks for your help. I'm mainly worried about the SDA's and if it's alright to run the amp in that configuration with the dreadnaught. I know that's the dreadnaught main purpose is for to allow the use of monoblocks. But I'd like to know if the parallel mono mode is safe with the interconnect? Bridged ratings are stamped on the top of the amp for 1/2 ohm operation so it should handle the 1.2tl's with relative ease.

westmassguy

I would think they will perform extremely well. The Dreadnaught is designed precisely for the situation you have. I would still recommend speaking with Mcintosh Customer Service or Tech support. Explain everything to them, and their recommendation for connecting the speaker wires. That's the only area that's a little grey in the manual.
The 1.2tls are listed as "Compatible" with 8 ohm outputs, so they're most likely 6 ohm nominal. If you upgraded the Sub Bass Inductor to a lower resistance version, they're more likely 4 ohm nominal now. Even in their stock form, they will hit 2 ohms at certain frequencies.

Schurkey

The way I understand things:

Parallel = double the amperage output, no change in voltage output. Perfect for low-impedance speakers.

Bridged = double the voltage output, double the amperage output (up to the limit of the output devices, heat-sink, and power supply) Theoretically four times the power delivery vs. standard operation--often less in practice. Very easy to get into trouble by over-driving the amp leading to overheating. Factory-bridged amps often use lower rail voltage which drops the power output somewhat, but reduces the tendency to over-drive the amp.

One of the experts will correct me if I'm wrong, or if I missed something important.

mantis

I know people have used these technics for many years but my experience never seemed to work out.
I fully believe if you need more power then what the amp can do per channel, buy more powerful amps. It seems like dynamic range falls short when you bridge.

motorstereo

So running parallel mono wired as the pic shows isn't going to create some sort of havoc such as running dual mono's does without the A1 or the dreadnaught. I guess I should've been more specific from the start. I'm not concerned about the amps not being able to drive any load that I put in front of it. Parallel mono won't damage anything in the speakers or dreadnaught....... am I correct?

westmassguy

The Dreadnaught completely isolates the two Amps. It should not be a problem as long as the terminal wiring at the Amp is correct.

motorstereo

Thank you westmass guy. I appreciate your time answering my somewhat vague question. That's the exact answer I was hoping to hear.

motorstereo

motorstereo

And this is the reason I was asking the bridging questions. I wasn't expecting much but I was pleasantly surprised by the increase in the soundstage width and the bass got a lot tighter as well. The big polks really like having 1000wpc of strapped Mac's

westmassguy

Very nice, enjoy.

DaveHo

Nice stack! Drool! Is that a sub in the corner? What you need that for, lol!

motorstereo

Thanx; Yes that's an 18'' Def tech sub in the corner. After today I don't think I'll be using it much anymore

motorstereo

Here's my finding having lived with dual 2500's for a few days now. After some investigation I've found that the strapped mode does not work properly with sda's. For whatever reason I was getting the sda signal through all the speakers on the opposite side when using the balance knob.
I've switched to the bridged mode now and all is well. I'm thinking the sda signal was getting passed through the strapping connectors. Thankfully nothing got damaged and I've learned something in the process. In their present bridged mode with all that current and wpc on tap I've never heard the Polks sound this good.

motorstereo

If anyone is on the fence about using mono-blocks with their sda-dreadnaught combo I can highly recommend doing just that. Now that I've got everything dialed in I've found several unexpected perks.

The soundstage has grown much wider and deeper. It extends to the walls on either side of the rig where it didn't quite make it with a single amp before. The depth now seems to extend several feet behind the back wall (how is this possible) The sweetspot has increased substantially in size from just a few feet to several feet in length now as well as about a foot wider to. I've also noticed the further back I step the wider the soundstage grows. Orchestra recording are simply outstanding for doing this. It's also nice that I no longer have to be dead center in the equilateral triangle for the sda effect. Detail on low level listening is also slightly but noticeably better. Turning up the volume knob now makes the dynamics go completely off the charts. It's quite apparent that the Polks like lots of current at their rated 1000 wpc.

I also used to use my 18'' sub crossed at 40-50hz to help fill in that area and below. The sub has not been turned on since the 2nd amp arrived and honestly I can't see a need for it anymore. It does make for a good solid equipment stand though lol. The only downfall I can foresee is I'm probably not going to be very happy with my electric bill. But then again I'm not using the internal 200 wpc amp in the sub so things just may balance out.

I'd also like to thank everyone in this forum for the help they've been in my journey to acquire this great sound that I presently have. Most especially I'd like to thank darqueknight for your research on that wonderful dreadnaught which allows me to run this big pair of amps.

And lastly I'd like to wish everyone a very Merry Christmas and best wishes for a happy and prosperous New Year here on the Polk forum

honestaquarian

Reference class system demo material!