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?
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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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"
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"
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.
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.
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???????
is the box divided into 2 discrete sections already 9 one for bass the other for bass/midrange???????
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
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
not sure if this image will show or not, but this is what they look like from the stock photo:
An externally hosted image should be here but it was not working when we last tested it.
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.
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
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
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.
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.
Well my suggestion still stands, use what you have for the bass, spend some money on a driver with good midrange and power handling There is an excellent Peerless 6inch that has a round face ( most are truncated ) the 830869
lets see if anybody else pipes up and chips in
Speaker driver
Other suggestions
https://www.madisound.com/store/product_info.php?cPath=45_228_256&products_id=1108
https://www.madisound.com/store/product_info.php?cPath=45_228_256&products_id=1140
https://www.madisound.com/store/product_info.php?cPath=45_228_256&products_id=8688
lets see if anybody else pipes up and chips in
Speaker driver
Other suggestions
https://www.madisound.com/store/product_info.php?cPath=45_228_256&products_id=1108
https://www.madisound.com/store/product_info.php?cPath=45_228_256&products_id=1140
https://www.madisound.com/store/product_info.php?cPath=45_228_256&products_id=8688
if I use lm3886 style chipamps, they seem to prefer 8ohms vs 4ohms.
each amp would directly power one driver or possibly one group of identical drivers. but 8ohms buys more flexibility when building that chip-amp, so if we can find 8ohm drivers, it makes my life a lot easier.
all the drivers you listed are in my price range. but HOW does one pick? what made you pick those, for example?
would getting some measurements of my cabinets help?
thanks again for your help.
each amp would directly power one driver or possibly one group of identical drivers. but 8ohms buys more flexibility when building that chip-amp, so if we can find 8ohm drivers, it makes my life a lot easier.
all the drivers you listed are in my price range. but HOW does one pick? what made you pick those, for example?
would getting some measurements of my cabinets help?
thanks again for your help.
I selected drivers with reasonable graphs at the price you gave
So two of those cheap drivers in series is an 8R load, make an amp for each set of 8R speakers.
midrange performance is what I look for, nice smooth graph with a smooth roll-off and not too many peaks and dips.
if using a 155mm midrange you will then need a tweeter that can be crossed as low as possible, your DCX should allow 4th order slopes so this probably won't be a problem
XO is supposed to be a smooth transition between drivers and the rule of thumb is to set the XO no more than one wavelength apart, so for a 165mm midrange that is half 165 or 90mm plus half the diameter of the tweeter, which is usually about 110mm, so the C2C distance is ~145mm which is about 2k
FREQUENCY & WAVELENGTH CALCULATOR
Select a tweeter whose resonant frequency is 2 octaves below that. Robust tweeter needed if using shallow slopes steeper slopes should allow a higher tweeter Fs but always buy the best tweeter you can
thanks again for the tips on woofer selection. any ones you like at parts express? I need to order some other things from them and if I can make one big order, shipping is free for me
any of those madisound units would probably be fine and they are all in my price range.
I don't have any experience with MTM style configs. I wonder if its even worth trying to continue with this style in this cabinet given that we might choose smaller midrange units and have to build bezel adapters and not be able to really move them closer together.
if you have your hands tied and cannot change driver to driver spacing, how 'bad' is that and can it be corrected for in the deq/dcx chain?
I get the impression that mtm config needs the box to be 'just so' and is not well suited to afterthought retrofitting. is that your thinking as well?
if its going to be too much of a ghetto job to convert an MTM box into another different driver'd MTM box then I'm ok with just going 2-way on a good pair of woofer/midrange and keeping things simple.
any of those madisound units would probably be fine and they are all in my price range.
I don't have any experience with MTM style configs. I wonder if its even worth trying to continue with this style in this cabinet given that we might choose smaller midrange units and have to build bezel adapters and not be able to really move them closer together.
if you have your hands tied and cannot change driver to driver spacing, how 'bad' is that and can it be corrected for in the deq/dcx chain?
I get the impression that mtm config needs the box to be 'just so' and is not well suited to afterthought retrofitting. is that your thinking as well?
if its going to be too much of a ghetto job to convert an MTM box into another different driver'd MTM box then I'm ok with just going 2-way on a good pair of woofer/midrange and keeping things simple.
I actually prefer MTM with the correct drivers, and if you can get a tweeter that will fit the I see no problem.
Given that you are using electronic XO selecting XO frequency can be trial and error but I have no experience with those units ( I use a simple Behringer CX )
Truth is tho that often it is easier to build new boxes; how-ever one way to use what you have is to utilize yours as a sealed box and just fill it with polyester and fiberglass.
As tweeter height is sort of predetermined by your box put the midrange at the top and the tweeter underneath and simply seal the other hole with a plate, separating the mid from the woofers will be more difficult, as it needs a compartment of its own to work properly in this context.
I'll have a look and see if there is a tweeter i think will work, sonically i have always liked silk domes but YMMV
Given that you are using electronic XO selecting XO frequency can be trial and error but I have no experience with those units ( I use a simple Behringer CX )
Truth is tho that often it is easier to build new boxes; how-ever one way to use what you have is to utilize yours as a sealed box and just fill it with polyester and fiberglass.
As tweeter height is sort of predetermined by your box put the midrange at the top and the tweeter underneath and simply seal the other hole with a plate, separating the mid from the woofers will be more difficult, as it needs a compartment of its own to work properly in this context.
I'll have a look and see if there is a tweeter i think will work, sonically i have always liked silk domes but YMMV
https://www.madisound.com/store/product_info.php?cPath=45_229_324&products_id=8437
https://www.madisound.com/store/product_info.php?cPath=45_229_324&products_id=8645
https://www.madisound.com/store/product_info.php?cPath=45_229_324&products_id=791
Starting points, I just looked at price, Fs and smoothness of graphs
https://www.madisound.com/store/product_info.php?cPath=45_229_324&products_id=8645
https://www.madisound.com/store/product_info.php?cPath=45_229_324&products_id=791
Starting points, I just looked at price, Fs and smoothness of graphs
I bought a lot of stuff from PE because I like free shipping
First, measure the overall diameter of the midwoofer to make sure that the replacement will drop right in.
Second measure the overall diameter of the tweeter to see if it is a standard size (~104mm). If it is then alot of plastic flange tweeter can be use if are willing to cut the flange to drop in the stock tweeter hole.
For simplicity I would keep the MTM configuration and wire 2 4 ohms midwoofers in series for your 8 ohms requirement. You can keep the 2 bottom woofers in place but not hook up for the complete look.
First, measure the overall diameter of the midwoofer to make sure that the replacement will drop right in.
Second measure the overall diameter of the tweeter to see if it is a standard size (~104mm). If it is then alot of plastic flange tweeter can be use if are willing to cut the flange to drop in the stock tweeter hole.
For simplicity I would keep the MTM configuration and wire 2 4 ohms midwoofers in series for your 8 ohms requirement. You can keep the 2 bottom woofers in place but not hook up for the complete look.
there are a few real tiny tweeters that would fit in the factory hole and
they'd need some bezel or adapter, still. you also suggested cutting a
tweeter's flange to mount in the factory tweeter hole. while its possible and
not too hard, it would be annoying to have to do that again if you replaced
the tweeter later on. not sure I like that solution, really.
I think the 'least touch' method is to use filler discs to cover holes that
don't get new drivers and to adapt drivers to existing holes if possible but
not to force it. you do get a longer distance of driver to driver that way,
which does suck, but if you don't want to redo the front, what other choice do you have?
they'd need some bezel or adapter, still. you also suggested cutting a
tweeter's flange to mount in the factory tweeter hole. while its possible and
not too hard, it would be annoying to have to do that again if you replaced
the tweeter later on. not sure I like that solution, really.
I think the 'least touch' method is to use filler discs to cover holes that
don't get new drivers and to adapt drivers to existing holes if possible but
not to force it. you do get a longer distance of driver to driver that way,
which does suck, but if you don't want to redo the front, what other choice do you have?
Hang on a sec. Before you throw out the baby with the bathwater..
Don't assume that because the Polks were $150 that the components are uniformly crap. For one, the Model 70's retailed at more like $500/pair, not $150/pair, so tossing all the drivers because you think Polk paid $5 each for them may not be the best conclusion.
You said you don't like the sound of them, but you didn't explain what was it that you didn't like. Too laid back? Too muddy? Too forward? You know that a lot of the sound of a multi-way system is in the crossover design, and a poor xover can make even "premium" drivers sound terrible. It may be that those drivers and cabinet sound good if crossed over properly. Unless there are serious, serious FR or distortion problems, a good crossover would probably make a huge difference. If you replace the drivers you're going to need a crossover anyway, whether active or passive.
What you might consider doing, and this might be more fun anyway, would be to get one of the woofers and the tweeter measured and get their FR graphs, then see if anyone here is up to the challenge of designing a decent crossover for it considering that data, the cabinet dims, your listening preferences, wattage available, etc. It's possible $30 of inductors, caps, and resistors will turn your speakers into what you were expecting.
In fact, I know someone (on another board) that does free crossover design if you just send them drivers to work with.
It may turn out that the woofers are fine but the tweeter has enough issues to be uncrossable, but at least then you know you just need to replace the tweet and can make the rest into something workable.
Don't assume that because the Polks were $150 that the components are uniformly crap. For one, the Model 70's retailed at more like $500/pair, not $150/pair, so tossing all the drivers because you think Polk paid $5 each for them may not be the best conclusion.
You said you don't like the sound of them, but you didn't explain what was it that you didn't like. Too laid back? Too muddy? Too forward? You know that a lot of the sound of a multi-way system is in the crossover design, and a poor xover can make even "premium" drivers sound terrible. It may be that those drivers and cabinet sound good if crossed over properly. Unless there are serious, serious FR or distortion problems, a good crossover would probably make a huge difference. If you replace the drivers you're going to need a crossover anyway, whether active or passive.
What you might consider doing, and this might be more fun anyway, would be to get one of the woofers and the tweeter measured and get their FR graphs, then see if anyone here is up to the challenge of designing a decent crossover for it considering that data, the cabinet dims, your listening preferences, wattage available, etc. It's possible $30 of inductors, caps, and resistors will turn your speakers into what you were expecting.
In fact, I know someone (on another board) that does free crossover design if you just send them drivers to work with.
It may turn out that the woofers are fine but the tweeter has enough issues to be uncrossable, but at least then you know you just need to replace the tweet and can make the rest into something workable.
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