MFW-15 Dual Opposed Build - Page 11 - AVS Forum
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post #301 of 319 Old 05-05-2011, 08:46 AM
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Originally Posted by penngray View Post

Nice boxes from Mark!! I guess if he is building sealed duals then the MFW-15 is fine in a sealed box.

Thanks. There is plenty of discussion here and elsewhere, but these are sized around what we are dialing in a modified SA-1000 amplifier (similar to what we do with the Turbo kit) which is capable of driving 4 MFW-15 drivers in 2.5-3.0 cu.ft. each sealed (series-parallel 4 Ohm). There are plenty of other options for enclosures where anyone can build their own or even pick up 2 or 4 of these from PE. Our cabinets will of course be more expensive than the above option, but built to much higher standards as well.

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post #302 of 319 Old 05-05-2011, 12:15 PM
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Any idea on the price of the amp yet?
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post #303 of 319 Old 05-06-2011, 11:41 AM
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Posted update on our forum

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Any idea on the price of the amp yet?


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Bringing you Custom subwoofer kits, with flames if you want
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post #304 of 319 Old 05-10-2011, 05:53 AM
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Are there any problems with dual opposed configurations when the woofers of multiples face each other? Any cancellation issues?

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post #305 of 319 Old 05-10-2011, 09:47 AM
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Quote:
Originally Posted by NicksHitachi View Post

Are there any problems with dual opposed configurations when the woofers of multiples face each other? Any cancellation issues?

No. You just need sufficient breathing room so as to not load the woofers with a restricted airflow. How much is enough depends on woofer size, mass, and the total compliance of the driver and sealed box as this determines at what point the loading becomes insignificant. 3-4" should be plenty.

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post #306 of 319 Old 05-21-2011, 04:50 AM
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Quote:
Originally Posted by wembley2000 View Post

Here is an example of adding below 20 boost with a BFD. The filters give 9db boost at 10hz. This is just an example, there are other ways to do it, use at your own risk.

Wem

Wem,

I was playing with WinISd(I'm very new with it) and I'm having a very hard time applying any boost down low without getting into severe overexcursion. Even a 2db boost centered 20Hz Q.4 exceeds x-max about 12hz. Are you running beyond x-max but under x-mech possibly?





Would you be nice enough to share your filter settings? I know my room would be different etc, but I'm just playing with the EQ and learning at this point.
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post #307 of 319 Old 05-21-2011, 04:25 PM - Thread Starter
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I am not good at putting filters in winisd. Remember even with boost added I have my subs each wired 8 ohm per each channel of an ep 2500 and 4000, so really no matter how much boost I add I can only put out 450watts per channel. What I normally do is take a rew sweep of my sub out at reference level with no eq then take a sweep of the sub out with boost/eq, I try to not boost the signal higher than reference, but I do sometime. I watch movies at -20, but the lfe channel is actually hot down low. Hope this helps.

Wem
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post #308 of 319 Old 05-21-2011, 04:50 PM
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"I was playing with WinISd(I'm very new with it) and I'm having a very hard time applying any boost down low without getting into severe overexcursion. Even a 2db boost centered 20Hz Q.4 exceeds x-max about 12hz. Are you running beyond x-max but under x-mech possibly?"

remember that winisd is a 2pi space model (the same as if you put the sub out in a large parking lot). if you have a medium to small room, you will get some gain below about 25hz.

also, eq requires power, so every time that you add 3db that is the same as doubling power.

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post #309 of 319 Old 06-21-2011, 03:43 PM
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Very nice build Wem...

I'm interested in doing the same but I have a couple questions that have popped up in my mind.

In my main theater, I currently have 3 original MFW-15's that work great and sound great as well. The graph for my room with them is attached. I'm having trouble trying to post it so I had to put it in a word document. Sorry.
Anyway, the current 3 MFW's with room gain go down to approximately 15Hz Attachment 215610

I currently have the 3 mfw's in different places in the room. 2 are up front and the 3rd is on a sidewall midpoint. In order to minimize cancellation, I needed to play with the phase control on the 3 subs. The two upfront are basically set at the same phase, but the mfw at the sidewall midpoint is somewhere around 90 degrees from the other two.

My room placement options are somewhat limited and I would like to use the same locations for the 4 new opposed build's using wembleys design. So the question then is, if I run the 4 new opposed builds with a EP4000, how is phase for something like this addressed? I understand you could wire one bank of subwoofers at 180 degrees via reverse polarity, but what if you need something other than a 180 degree phase shift? Are you SOL or what are the options?

Next question, if I do this build, I will likely try the EP4000 with a sms-1 for equalization. Is it ok if I run something other than a 2, 4, 6, or 8 ohm load with these if I decide to add more than 4 of wem's builds to my theater? I'm assuming this isn't a problem as long as I stay above 2 ohms, but figured I'd ask.

Lastly, I'm assuming that going from 3 of the original MFW's to 4 of wembleys dual boxes would be a pretty big improvement due to the increase of volume of the air moving but I'm just trying to get additional impressions from what I might expect from this upgrade. I imagine going from the ported MFW's to sealed would sound somewhat different anyway. The original MFW's are actually pretty impressive if you don't have problems with them. I don't think I really need to upgrade but when you're into a hobby and some sort of project comes along like this, well, I've got to consider it.

Thanks Wembly and all and I hope this isn't considered a thread jack. I really dig this project!

Best wishes everyone,

AIH
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post #310 of 319 Old 06-22-2011, 08:29 AM
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Quote:
Originally Posted by wembley2000 View Post

I am not good at putting filters in winisd. Remember even with boost added I have my subs each wired 8 ohm per each channel of an ep 2500 and 4000, so really no matter how much boost I add I can only put out 450watts per channel. What I normally do is take a rew sweep of my sub out at reference level with no eq then take a sweep of the sub out with boost/eq, I try to not boost the signal higher than reference, but I do sometime. I watch movies at -20, but the lfe channel is actually hot down low. Hope this helps.

Wem

OH, so only 112W per driver. That helps.

Any reason your not running bridged to get more power to each driver? Or you just playing it safe?

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post #311 of 319 Old 06-22-2011, 08:47 AM
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Quote:
Originally Posted by Mark Seaton View Post

No. You just need sufficient breathing room so as to not load the woofers with a restricted airflow. How much is enough depends on woofer size, mass, and the total compliance of the driver and sealed box as this determines at what point the loading becomes insignificant. 3-4" should be plenty.

I disagree with this thought. Restricting the outward half of the drivers stroke is not necessarily a bad thing given the mechanics of air spring distortion.

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post #312 of 319 Old 06-22-2011, 10:21 AM
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Hey Bosso do you have any before and after measurements saved of the effects of the plate on your subs? I wanted to look at this myself but probably won't get a chance with everything else going on.
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post #313 of 319 Old 06-22-2011, 11:02 AM
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Quote:
Originally Posted by NicksHitachi View Post

Wem,

I was playing with WinISd(I'm very new with it) and I'm having a very hard time applying any boost down low without getting into severe overexcursion. Even a 2db boost centered 20Hz Q.4 exceeds x-max about 12hz. Are you running beyond x-max but under x-mech possibly?





Would you be nice enough to share your filter settings? I know my room would be different etc, but I'm just playing with the EQ and learning at this point.

Winisd effectively multiplies the "System Input Power" you are specifying for your project. In other words when you spec a box and say it will receive 100W, it will model for 100w where eq is set to 0db. When you set eq to 3db power doubles to 200w. Make sense? You can see this power multiplication if you select the "Apparent amplifier load" view. Without eq you will see where power peaks (it isn't constant because the speaker is a resistive load). Now apply some eq and watch what the amp load does.

In practice, when you apply an eq boost, you are eating up some headroom by approaching some limit of power handling, amp capacity or driver excursion. Depending on where the boost is applied, you might need to lower your overall "System Input Power" to reflect this reduced headroom.
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post #314 of 319 Old 06-22-2011, 05:00 PM - Thread Starter
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Quote:
Originally Posted by NicksHitachi View Post

OH, so only 112W per driver. That helps.

Any reason your not running bridged to get more power to each driver? Or you just playing it safe?

Actually 450watts per cab/225 watts per driver.

I could wire 2 cabs together and run the 2 sets bridged off of the 2 amps, but I would only gain 3db's and risk both thermal and mechanical damage.
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post #315 of 319 Old 06-22-2011, 05:45 PM - Thread Starter
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AudioIronHorse,


Quote:


I currently have the 3 mfw's in different places in the room. 2 are up front and the 3rd is on a sidewall midpoint. In order to minimize cancellation, I needed to play with the phase control on the 3 subs. The two upfront are basically set at the same phase, but the mfw at the sidewall midpoint is somewhere around 90 degrees from the other two.

My room placement options are somewhat limited and I would like to use the same locations for the 4 new opposed build's using wembleys design. So the question then is, if I run the 4 new opposed builds with a EP4000, how is phase for something like this addressed? I understand you could wire one bank of subwoofers at 180 degrees via reverse polarity, but what if you need something other than a 180 degree phase shift? Are you SOL or what are the options?

You would need a DCX2496 or a minidsp (i am not sure about the mini though, i have a DCX) to incrementally adjust phase.

Quote:


Next question, if I do this build, I will likely try the EP4000 with a sms-1 for equalization. Is it ok if I run something other than a 2, 4, 6, or 8 ohm load with these if I decide to add more than 4 of wem's builds to my theater? I'm assuming this isn't a problem as long as I stay above 2 ohms, but figured I'd ask.

You would be ok with 1 amp for 8 drivers, wire 2 banks at 4 ohms, then run off of each channel, anymore though and i would get another amp.

Quote:


Lastly, I'm assuming that going from 3 of the original MFW's to 4 of wembleys dual boxes would be a pretty big improvement due to the increase of volume of the air moving but I'm just trying to get additional impressions from what I might expect from this upgrade. I imagine going from the ported MFW's to sealed would sound somewhat different anyway. The original MFW's are actually pretty impressive if you don't have problems with them. I don't think I really need to upgrade but when you're into a hobby and some sort of project comes along like this, well, I've got to consider it.

You would be louder and lower, but you are going from 3 drivers to 8. You will need to boost the lowend though, but you could do that with either the DCX or the minidsp. I just built a ported cab with this driver that is tuned to around 18hz, and it is pretty impressive, 3 of them im sure do a fine job but you just dont get the extension you do with sealed though.

I am pretty sure I will never go back to any other way but multiple sealed.

Hope this helps,


Wem
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post #316 of 319 Old 06-23-2011, 07:58 AM
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Quote:
Originally Posted by wembley2000 View Post

AudioIronHorse,




You would need a DCX2496 or a minidsp (i am not sure about the mini though, i have a DCX) to incrementally adjust phase.


I have an sms-1 that has incremental phase adjustment. Hmmm... maybe I could run the front 2 off one channel of the ep4000, and the other two off the other channel after making the phase adjustment. I would think that would work. Agree?



You would be ok with 1 amp for 8 drivers, wire 2 banks at 4 ohms, then run off of each channel, anymore though and i would get another amp.


Ok so hypothetically speaking what would happen if I did something like this:

I build 6 enclosures with 2 drivers a piece.

I wire the enclosures for an 2 ohm load (2-4 ohm drivers in [parallel).

I then wire 3 enclosures per channel of an ep4000, presenting each channel of the amplifier with a 6 ohm load (3-2 ohm enclosures in series).

That's what I'm roughly getting at by asking if you can run a EP4000 on something other than a 2, 4, or 8 ohm load. What happens if your run a 6, or some other oddball number other than the standard 2,4, or 6?

Using the example above for the 6 ohm/channel setup, would there be any advantage to doing it this way over the 4 enclosures that Wembly built? I only have one dedicated spare 20amp circuit in my equipment rack that I could run an EP4000 with, so I'd like to use just one amp.


You would be louder and lower, but you are going from 3 drivers to 8. You will need to boost the lowend though, but you could do that with either the DCX or the minidsp. I just built a ported cab with this driver that is tuned to around 18hz, and it is pretty impressive, 3 of them im sure do a fine job but you just dont get the extension you do with sealed though.


Again, wont the sms-1 work for boosting the low end?



I am pretty sure I will never go back to any other way but multiple sealed.

Hope this helps,


Wem


It does help sir. Sounds like you are enjoying your build. Now that you've had it for a while, any additional impressions?

Thanks much for sharing your knowledge Wembly. Again, fabulous build!


AIH
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post #317 of 319 Old 06-24-2011, 06:33 AM - Thread Starter
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I dont have any experience with the sms-1 so I cant be much help there, but if it has 2 outputs it may work.

Your wiring example should work, but each driver will only get around 90 watts. I am not sure about the ep wattage into 6 ohms, just guessing 550 watts. BTW I am going by the wattages measured in the measuring amplifiers thread.

I really enjoy the subs, I did move them around in the room some lastnight to see if I could get a better FR. I did get a better graph, but the subs are not quite as pretty as they were stacked up but I am going to leave them there for a few weeks to see if I can live with them.

Wem
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post #318 of 319 Old 06-24-2011, 10:45 PM
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I believe the sms-1 has 4 outputs, all with separate phase adjustment. I'll have to dig into it more.

Yeah I'm just not sure if there would be an advantage to running more woofers below their limits or not. Or you gain anything by wiring multiple woofers at a lower load.

You wouldn't anticipate any conflicts with using some of your opposed design cabinets for the front stage with something like Sandbagger/Seatons dual front firing style cabinet kits for behind my theater chairs would you? I would think that as long as the internal volumes of both match, you will get the same performance being it's just a difference in configuration.

Thanks for answering my questions about your project Wembly. I'm glad you are happy with the results of your build. I guess you have convinced me. I ended up ordering 20 woofers from Danny. I'm not quite sure exactly what I'm going to do with all of them just yet, but I do have a few different systems where I could use them.

Looks like it will soon be time to start my own thread.

Thank you again for your responses and guidance,

AIH
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post #319 of 319 Old 06-26-2011, 05:35 PM - Thread Starter
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I dont think the box design will matter, like you said just keep them about the same size.

Good luck with your builds, I would have ordered 20 of the drivers also if I had the money, just cant beat the price.

Wem
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