Need advice - new Polk system for my SUV

polkfan826

Need advice for new Polk system - comp spkrs, amp and sub
Hello out there in CP - my request is kind of detailed - but I'm sure one of you out there can help me.

Just bought a 07 Acura MDX (with the Nav package) which comes with a 10 speaker fancy audio system. Sounds great (and plays the DVD-A discs which sound cool) but overall is underpowered IMHO and uses factory lightweight speakers. I want more power overall, more mids and low bass. I'm also spoiled with crisp Polk tweeter highs - which I had in my Honda Accord (about to be sold - more on that later)

Here's what I'm planning for an upgrade --does it make sense?

Head unit: Keep the stock one - it's integrated with the HVAC system for the MDX and would be a PITA to replace. Another complication: It's a data link system where the headunit does not control the volume but instructs the stock amplifier via a data link signal chain. The main system amp powers the interior speakers directly while sending a line level signal to a secondary subwoofer amp, mounted within the stock sub enclosure on the passenger side rear panel.

What this means is that I cannot tap the signal before the stock amp and have to utilize the speaker level signal post-amp for front stage and the line level signal for subwoofer. Happily though, there are no separate signal wires for midbass and tweeter so no summing will be needed.

Front soundstage:MM6501's - woofers in stock locations in doors w/ tweeters either in dash stock location - or finding new location to drill new hole in upper door panel. I did this for my older Accord and they still sound great after 11 years.

Rears fill: Leaving oem speakers (they have 6 1/2 drivers in doors and 3" mid/high drivers pointed forward from C pillars. These are decent -- running off the factory HU/amp - so they run of of juice - but I would just be using them for fill and for making rear seat passengers happy.

Subwoofer: - the MDX comes stock with a sealed 8" DVC sub in the rear quarterpanel -- complete with a .25 cu ft custom enclosure. Powered by a seperate 25w stack-of-playing-cards-sized amp mounted right in the enclosure. This amp is fed from main stock amp by line level signal - but I'm guessing its a lowpass signal so I can't use it to drive the rest of the system (also I would lose my fader if I did this). It's a paper resin woofer and I noticed it only plays normally when the balance control is centered. When it's fed to just right or left channel from the HU balance control, the amp stops playing. My first time with a DVC sub -- so I'm not sure how that works. I'm planning to ditch the factory amp and sub and put in new Polk MM840 in same location -powered by new amp.

Amp: Planning to replace the factory amp with a Polk unit -- probably a 500.4 which I found factory refurb for only $199.

Questions:
1. I've read about bi amping the comps in front -- how would I go about doing that? Since I don't need the rear channels of the 500.4 I could send them to the woofers and send the amp front channel power to the tweeters? I believe the amp provides the crossover settings to eq the 6501's, correct?

2. On my Accord, I was running a passive crossover network (caps and coils build for me by local audio shop back in the day) which ran my MM5251's (or whatever they were called back then) and a 10" free air sub all off the same Kenwood 40w x 2 amp. As I remember, the highs, mids and mid/bass were fed to the front comps and the lows to the sub in back. It all worked and sounded awesome. (I was actually tempted to rip it out of the Accord and put it in my new MDX -- but MDX doesn't have a trunk for the free air sub and plus I can put 6 1/2" woofers in the doors rather than the 5 1/4's from the Accord. So the new owner will get the best audio system in a 92 Accord in this area!) Could I run the Polk MM840 the same way off the 500.4 (for instance with the tweeters on their channel) since the highs would be going to the tweets and just the lows from those channels to the sub? How would that get wired up so all the ohms and the frequencies are correct? Would the inboard crossover settings in the 500.4 manage that set-up? If they won't, I will just run the 6501's off the front amp channels (with a HP set to cut out the lows below 60 hz or so) and bridge the rear channels to go to the sub.

3. Assuming the above setup ould work, should I get the DVC MM840 or the regular one? What is the difference?

4. Would the MM840 be OK in the smallish (roughly .25 cu ft) enclosure? Pretty sure the depth of the woofer is ok - but I see from the MM840 specs that it would like more cu ft of air in an enclosure. Granted I'm going for sq, not trying to rattle neighbors windows, so wondering if I could just live with it. Another option would be for me to go with another brand of sub -- some make a shallow-mount 8" which is both designed for a smaller enclosure AND because of it's design takes up less airspace in the enclosure. BUT....it's not a Polk and I'm kind of brand loyal.

5. Will I need to clean up the spkr level signal (and get rid of all the HU eq and processing) with a box like the JL Cleansweep? I've read on MDX forums that other have not had to mess with this - but I'm unsure. Thoughts? Any MDX 2nd generation owners out there perchance?

6. What gauge power wire should I run to the 500.4?

Thanks again for the help

pentoncm

polkfan826 wrote: »

3. Assuming the above setup ould work, should I get the DVC MM840 or the regular one? What is the difference?

4. Would the MM840 be OK in the smallish (roughly .25 cu ft) enclosure? Pretty sure the depth of the woofer is ok - but I see from the MM840 specs that it would like more cu ft of air in an enclosure. Granted I'm going for sq, not trying to rattle neighbors windows, so wondering if I could just live with it. Another option would be for me to go with another brand of sub -- some make a shallow-mount 8" which is both designed for a smaller enclosure AND because of it's design takes up less airspace in the enclosure. BUT....it's not a Polk and I'm kind of brand loyal.

5. Will I need to clean up the spkr level signal (and get rid of all the HU eq and processing) with a box like the JL Cleansweep? I've read on MDX forums that other have not had to mess with this - but I'm unsure. Thoughts? Any MDX 2nd generation owners out there perchance?

6. What gauge power wire should I run to the 500.4?

Thanks again for the help

DVC means that there are two voice coils on the sub. What does this mean? All it means is that it has more options when wiring it up. Get a DVC sub so that you can wire the coils in parallel and present a 2ohm load to your sub amp.

I would put the 8 inch MM sub in a .35 cu ft. that is what the recommended size is. I wouldn't worry too much about displacement, its going to be tiny on an 8 inch sub. If you really want to use a smaller .25 cu ft enclosure, pack it with a quarter pound of polyfill. The larger enclosure will make sure you get full low end extension and get a flat response that isn't peaky.

I would go ahead and get a 4 gauge power wire kit.

Don't waste your money on a JL audio cleansweep, how much is it like $250. If you want to clean up the signal, get the Audison Bit Ten for $400. It would let you run your speakers fully active (no passive crossovers), give you 31 band eq's on every channel, and gives you time alignment. This is in addition to de equalizing factory systems. I don't like things like the clean sweep because they are pricey but don't let you tune the system afterward.

polkfan826

Don't waste your money on a JL audio cleansweep, how much is it like $250. If you want to clean up the signal, get the Audison Bit Ten for $400. It would let you run your speakers fully active (no passive crossovers), give you 31 band eq's on every channel, and gives you time alignment. This is in addition to de equalizing factory systems. I don't like things like the clean sweep because they are pricey but don't let you tune the system afterward.[/QUOTE]

Interesting -- hadn't heard of that brand/item. May be more than I want to spend -- I will keep researching.

polkfan826

I would put the 8 inch MM sub in a .35 cu ft. that is what the recommended size is. I wouldn't worry too much about displacement, its going to be tiny on an 8 inch sub. If you really want to use a smaller .25 cu ft enclosure, pack it with a quarter pound of polyfill. The larger enclosure will make sure you get full low end extension and get a flat response that isn't peaky.

I'm confused -- won't the added polyfill's displacement make my existing .25 enclosure smaller? Or are you saying that the polyfill will not change the volume but it will make the .25 sound better with the MM840?

pentoncm

Poly fill will make the sub behave as though it is in a larger box. This is because it will slow down the bass waves coming from the speaker. The rule of thumb is to use 1 pound of poly fill per cu ft of air space. There is a point however that if you add too much, it would make it sound worse. Like if you already had a larger than optimal enclosure and you stuffed it with a bunch of fill, it would be bad.

Audison/Hertz has been around for a while but they are located in Italy. They have only been distributing in the USA for a few years now. They are very popular right now in car audio. There are no authorized online retailers that I know of, so the only way to buy their products is through local shops. If you want to look into them, go to the electtomedia usa website and look for dealers.

polkfan826

pentoncm wrote: »

Poly fill will make the sub behave as though it is in a larger box. This is because it will slow down the bass waves coming from the speaker. The rule of thumb is to use 1 pound of poly fill per cu ft of air space. There is a point however that if you add too much, it would make it sound worse. Like if you already had a larger than optimal enclosure and you stuffed it with a bunch of fill, it would be bad.

Audison/Hertz has been around for a while but they are located in Italy. They have only been distributing in the USA for a few years now. They are very popular right now in car audio. There are no authorized online retailers that I know of, so the only way to buy their products is through local shops. If you want to look into them, go to the electtomedia usa website and look for dealers.

Very interesting -- I will definitely try the polyfill. Thanks for the info!

Would the Audison unit make it easier to bi-amp the 6501's and then run the sub off the back channels of the amp as well? Or is 125/channel rms enought to run to the 6501's? How is yours set up if you don't mind me asking?

pentoncm

I have a Kenwood Excelon x595, the front preamp outputs go into my Bit Ten. The Bit Ten then sends out 5 channels of output. My MM6501s take up channels 1-4; channels 1 and 2 are for my tweeters, and 3 and 4 are for the woofers. Channels 1-4 go from the Bit Ten go into my mtx amp that puts out 105 W at 2ohm, 70w at 4ohm. So my front woofers get 105W and the tweeters get 70W. The fifth channel sends the signal out to my subwoofer amp.

I do not run rear speakers, there are a number of people here who go by this method.

This is an active setup, not biamping. Biamping still maintains the passive crossovers but gives you more power to each of the components. Active means that the signal goes from the processor to the amp and then directly to the speakers. This allows you to control the crossover points and slopes of each driver.

polkfan826

pentoncm wrote: »

I have a Kenwood Excelon x595, the front preamp outputs go into my Bit Ten. The Bit Ten then sends out 5 channels of output. My MM6501s take up channels 1-4; channels 1 and 2 are for my tweeters, and 3 and 4 are for the woofers. Channels 1-4 go from the Bit Ten go into my mtx amp that puts out 105 W at 2ohm, 70w at 4ohm. So my front woofers get 105W and the tweeters get 70W. The fifth channel sends the signal out to my subwoofer amp.

I do not run rear speakers, there are a number of people here who go by this method.

This is an active setup, not biamping. Biamping still maintains the passive crossovers but gives you more power to each of the components. Active means that the signal goes from the processor to the amp and then directly to the speakers. This allows you to control the crossover points and slopes of each driver.

Unfortunately I can't tap the signals from the HU (line level) like you did -- due to my vehicle's OEM system (it feeds the main amp directly in a data chain set-up - all controls require both to be working. I would have to feed the Bit Ten a spkr level input - can it do that? Or, I could tap the line level signal going from the main amp to the small sub amp - but I'm guessing that is low pass filtered.

Could the Bit Ten take the filtered line level signal (from the main amp) - clean it back to flat - and then process it and feed the new signals to the new amp - like you did? If that would work, I would run the processed components and the processed sub signal to the amp and then to the speakers - and I could just leave the oem speakers in back running of oem main amp.

I would lose fader control at the oem head unit, though. Could I get fader (fronts to rear subs) with a remote control I saw with the Bit Ten. thnx again

pentoncm

Yes the Bit Ten is designed to integrate with OEM systems using speaker level inputs. That is the Master Input and takes a 2V to 15V input. What you could do is take the front speaker level outputs from your HU before they get to the factory amp and send that to the Bit Ten. That stereo signal would be reconstructed into 5 channels and de-equalized. Then if you use a 4 channel amp you could run the MM6501s fully active up front. The fifth channel would go to a new sub amp.

If you want the rears to work, you could leave the rears hooked up to the oem amp.

By doing this, if you used the fader control on the oem headunit, fading forward would adjust the master volume level going into the Bit Ten affecting the MM6501s and the sub. I have the DRC which is $200 extra, unless you get the Bit Ten D (comes with remote for $600 total), this gives you sub control but also lets you use the fader function. I use the fader to fine tune the woofer/tweeter levels.

If you plan on going all out and optimizing crossover points and equalizing the front components, you will not want the rear speakers going very loud at all.

polkfan826

pentoncm wrote: »

Yes the Bit Ten is designed to integrate with OEM systems using speaker level inputs. That is the Master Input and takes a 2V to 15V input. What you could do is take the front speaker level outputs from your HU before they get to the factory amp and send that to the Bit Ten. That stereo signal would be reconstructed into 5 channels and de-equalized. Then if you use a 4 channel amp you could run the MM6501s fully active up front. The fifth channel would go to a new sub amp.

If you want the rears to work, you could leave the rears hooked up to the oem amp.

By doing this, if you used the fader control on the oem headunit, fading forward would adjust the master volume level going into the Bit Ten affecting the MM6501s and the sub. I have the DRC which is $200 extra, unless you get the Bit Ten D (comes with remote for $600 total), this gives you sub control but also lets you use the fader function. I use the fader to fine tune the woofer/tweeter levels.

If you plan on going all out and optimizing crossover points and equalizing the front components, you will not want the rear speakers going very loud at all.

OK good news on the spkr level inputs. Agree about the rear spkrs just being low volume level fill.

But I don't really want to buy a 2nd amp -- was hoping to run the rear sub in bridged mode off the back two channels of a 4 channel amp. The 500.4 gives me 125w (conservative) to the 6501's in front - and then bridged 250 to the MM840 in back - that should be enough for my needs. Is there a better way to run the comp set and the sub off one amp if I was to use the Bit One?
Audison makes great stuff - but $400 is alot to spend and it may be more control than I need. hmmm

pentoncm

The only way to do what you want, is to use the passive crossovers that came with the components. This is not ideal as they rob amplifier power, (30% is a safe number), they totally mess up the impedance curve, and you can't fine tune the tweeter level other than the switch on the crossover.

Alpine Mrx M50 is only $187 from Cartoys.com (authorized retailer), you could use this as your sub amp and the other 4 channel for woofers and tweets.

pentoncm

Things get expensive real fast :twisted:

polkfan826

pentoncm wrote: »

The only way to do what you want, is to use the passive crossovers that came with the components. This is not ideal as they rob amplifier power, (30% is a safe number), they totally mess up the impedance curve, and you can't fine tune the tweeter level other than the switch on the crossover.

Alpine Mrx M50 is only $187 from Cartoys.com (authorized retailer), you could use this as your sub amp and the other 4 channel for woofers and tweets.

Really appreciate all your help pentoncm - I think I'm going to go passive and just use the one amp. I had MM5250's and a 10" free air sum running tri-mode (all passive) off a 40w x 2 kenwood amp in my old car -- and it was loud enough for me. Could have used some more power for the sub, but the 500.4 will solve that as it will send more than 250w rms bridged to the sub (vs 80w in the old car). And the 500.4 comes with a remote volume adjustment for the rear channels (sub) so that is taken care of.

Now just to solve the challenge of getting a clean signal (devoid of all the pre-programmed eq and volume hi-jinks) from the hu to my amp. If I don't have to sink 400 into a bit ten (granted they are really nice) that would be even better. Apparently the mounting depth and height of my MDX's stock enclosure also poses a problem with the MM840. too deep and too high I'm being told. And it never ends...:rolleyes:

pentoncm

So you have two options to get around the factory eq.

(1) change the HU, which I think you don't want to do.
(2) Get some sort of processor, JL cleansweep is an overpriced option as it doesn't give you any tuning (not even bass/mid/treble). A new HU makes more sense than the cleansweep. At least then for the same amount of money you could get time alignment, crossover selection, some EQ bands. Bit Ten is most likely the cheapest option as far as a full blown processor. Bit One is $1000, JBL MS8 is $799. You could consider the Alpine PXE-H660 at sonicelectronix.com for $250, far less tuning than Bit Ten but would give you good sound.