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Old 4th January 2011, 04:21 PM   #1
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Default polk monitor 70: worth any kind of upgrade or not?

due to a holiday impulse buy (lol) I have a pair of polk monitor 70's.

I tried them and didn't like the sound but thought that maybe the cabinets are salvagable and with some driver replacements and active crossover (maybe eq) it could be passible.

is this is a fool's errand? tell me now that there's no way to make this into at least a mid-fi system and I'll stop and just sell them as used.

but I'd like to give it at least a chance. this is a tower config with 4 6" holes and one 'mtm' tweeter hole toward the top. there's also a port at the bottom/front. I currently do have an active crossover (dcx2496) and am building some chip-amps for the various driver channels. I don't really see the need for a passive crossover and that gives me a lot of freedom in picking drivers (no?)

the as-shipped config seems to be the bottom 2 6" drivers in series and being a bass or midbass system. there is a roll of padding between the lower 2 and the upper region (the mtm area). maybe I can have 1 *good* aftermarket driver in the lower area and have a 6" round mdf disc made to cover the other hole. that wouldd be a lowpass section.

on top the tweeter hole is non-standard and so its a loss for all but the smaller surface-mount style tweeters. maybe I ignore the factory tweeter hole, cover it up and put the new tweeter up in the top woofer hole, with a suitable mdf bezel plate made for it.

finally a midrange could fit in the remaining 6" hole. any size driver less than or = 6" would fit with another mdf bezel.

I took some shots of the drivers that come shipped with this speaker system. I'm not sure they are even worth using. the question is: is the cabinet worth using; or is it too backward to try to find drivers to fit just a 'chassis' instead of the other way around?
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Last edited by linuxworks; 4th January 2011 at 04:23 PM.
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Old 4th January 2011, 10:55 PM   #2
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Try and send them back?? I think you may have already answered your own query, I hope you didn't spend too much money on them>
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Old 4th January 2011, 11:02 PM   #3
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Default I hope I didn't come across as too flippant

I have made the same basic mistake myself too many times to count.

Perhaps you can Bi / Tri-amp but a quick look suggests that tweeter would have cost the manufacturer about $1- unless it actually is a Neo and my own feeling is that 6inch is too big for MTM set-up; although that is open to debate depending on the quality of the chosen drivers, how much bass do they have?
How do they sound to you "As is"
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Old 4th January 2011, 11:28 PM   #4
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its too expensive to send back. it was free shipping (great when you plan to keep it, lol) but its going to be nuts to mail this back. I'd have to craigslist them or something like that - which is still a possibility.

the thing is, I do like the cabinets and they don't look all that bad. I can add more bracing on the inside and I dont' mind mdf bezels to retrofit drivers into 'standard' 6" holes.

I did want some floor standing speakers with full range sound. mostly I've been running smaller speakers (tannoy pbm8, pbm6.5, mission 700) and I want a step-up in size, mostly for better bass. this cabinet is about right for what I think I would need in bass response. question is: can it sound ok enough with decent drivers and some RTA work to find where things should be, crossover wise ?

if this does not work out my next option is to just buy a full kit (parts express or similar) and build a known good design. I'm not all that great with woodwork, though, and the fact that this cabinet is 'all done' (essentially) and actually looks good to me did appeal to me as a project starter.

but if its really a bad idea, I could just abandon it now before I get too far into it.
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Old 4th January 2011, 11:38 PM   #5
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OK i am no expert but i can try ( and play devils advocate ) are all woofers the same? Do you have the ability to measure the parameters? can you find the makers parameters for the drivers if you can't measure them???
is the box divided into 2 discrete sections already 9 one for bass the other for bass/midrange???????
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Old 4th January 2011, 11:50 PM   #6
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yes, all shipped woofers seem identical. very cheap, not good sounding, meant to look flashy is my guess. I am very willing to dump ALL drivers, in case that was not clear.

there's no way I can get specs on the included drivers. I almost don't care at best, I *might* be able to use 2 of the original drivers in the lower section as pok sort of intended. they came wired in series (those 2 6" woofers) and that was on the lower 2 posts on the spkr terms on the back. its possible that if they are crossed over low enough, they won't sound so bad and are left as a midbass system.

above those 2 holes is a roll of padding that polk placed in there. it seems they meant that as an isolation barrier. keeping with that idea, the lower region can handle the more air-moving bass and the upper can be a SMALLER driver than 6" (with a bezel adapter) and a tweeter in teh final remaining 6" top hole.

the tweeter factory hole seems useless and I'd put the factory tweeter back and just leave it disconnected. once the black cover is over the speaker system, all evils would be hidden anyway.

so, I am willing to order some tweeters, build a bezel adapter from mdf and try to make due with a good set of mid/tweeter in that upper region and see if that is at least listenable. then I'd power the lower section and see if the extra bass was helpful or worked against the system.

and again, I know this is somewhat backwards in how to design a system and I know that even if I pick decent drivers that work well together that they might need 'some work' to sound ok in this box. I realize that but I'd like to know if its do-able or if its just throwing good money at bad.

if I don't use the stock drivers, maybe someone who owns this set and likes them will buy them locally from me. who knows. but using the stock drivers is NOT a design goal and I'm happy to dump them. very happy, actually
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Old 4th January 2011, 11:53 PM   #7
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not sure if this image will show or not, but this is what they look like from the stock photo:


Click the image to open in full size.
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Old 5th January 2011, 12:01 AM   #8
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those drivers are going to be nasty at $199 for a pair of speakers with that many drivers and such a large box. Don't know what your driver budget is but I have personally thinking about using an Alpair 5 as a >800Hz driver in a sealed box with a decent 8" - 10" bass driver and a sharp crossover. However such ideas would require taking the box apart to modify it internally and $199 is expensive for a pair of middling quality wooden boxes.
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Old 5th January 2011, 12:19 AM   #9
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Can you check the wiring again and the DCR of those woofers please? if they are all 8R woofers then i would suggest keeping them all, wire them series /parallel and mounting them clamshell.
Then use the top half of the box and buy a decent midrange and tweeter or even 2 half decent 3inch mids and a tweeter for WWMTM arrangement
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Old 5th January 2011, 12:23 AM   #10
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the sale price, if that matters, was $150 each, plus some for tax.

lets say I sell all the woofers and maybe I get $10 each (argument's sake). that's 4 per spkr as $40. that makes the cabinets closer to $100ish.

now are they worth using?

I also don't need to fill every driver space. maybe I ignore the 2 lower holes and fill them with blanks (discs). maybe I allocate all my funds to 1 good 6" driver for the 2nd top hole and a good matching tweeter for the top 6" hole (with bezel to adapt it). a nice large 2 way (lol). I could even be happy with that if the 2-way sounded clean enough and had a full enough sound.

and remember, I do have a deq2496 as well as dcx2496 (and measurement mic). was hoping, to some degree, to have a little fun with DIY and learn a few things as well.

for prices, I think I could justify $50 per driver, or in that range. again, not all 4 holes would be filled! perhaps 2 or 3 but not 4.
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