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post #181 of 319 Old 03-21-2011, 10:45 AM
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Quote:
Originally Posted by Kevin A View Post

I really enjoyed watching this build! Congrats on achieving your goals & winding up with some very nice subs at a reasonable investment!



Question for you (& others):
I currently have a single THT (24" wide) and am contemplating building a second THT. What would I gain (or lose) if I decide, in lieu of building the 2nd THT, to build two of these MFW-15 Dual Opposed subs (4 drivers) of approximately the same size in this thread ( 23.5x23.5x26.5; 22x22x23.5 internal)? These two would replace my single THT. I assume they'd dig down a bit further than my single THT (or possibly two), but how about output?

Single THT in my room:


IMO, you can't separate the room from the subwoofer. What are you room dims and does it have big openings?

I helped a friend build two THTs for his living room. We calculated the room volume at close to 9000 cu ft. It also had large openings to the rest of the house. He basically had no room gain. That fact combined with a restricted budget were the reasons why I suggested the THTs. They sound great, but his response looks like yours, nothing below 20hz.

Four sealed MFW-15s would have probably given adequate output to 20hz, maybe 15hz but they weren't available at this price. It also would have required a bigger amp, adding cost. With the current clearance on them, I'd consider 4 of them instead of the THT for his room, but I'm not certain it would be a better route.

In a small room, I'd go with 4 MFW-15's sealed in a heartbeat over the THT. I don't really see the point of the THT in smaller rooms. IMO, if your room shows nice room gain, you'd be better off using 2 of the THT drivers but in a sealed alignment than those same drivers in THTs.

If you want to know what kind of room gain you are getting, put a driver in a sealed box that you know the dimensions. Model it and then measure a sweep of it. Compare the curves and you will see what gain you have to work with.
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post #182 of 319 Old 03-21-2011, 12:36 PM
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i would echo everything said in #181.

Listen. It's All Good.
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post #183 of 319 Old 03-21-2011, 12:58 PM
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Quote:
Originally Posted by coctostan View Post

IMO, you can't separate the room from the subwoofer. What are you room dims and does it have big openings?

I helped a friend build two THTs for his living room. We calculated the room volume at close to 9000 cu ft. It also had large openings to the rest of the house. He basically had no room gain. That fact combined with a restricted budget were the reasons why I suggested the THTs. They sound great, but his response looks like yours, nothing below 20hz.

Four sealed MFW-15s would have probably given adequate output to 20hz, maybe 15hz but they weren't available at this price. It also would have required a bigger amp, adding cost. With the current clearance on them, I'd consider 4 of them instead of the THT for his room, but I'm not certain it would be a better route.

In a small room, I'd go with 4 MFW-15's sealed in a heartbeat over the THT. I don't really see the point of the THT in smaller rooms. IMO, if your room shows nice room gain, you'd be better off using 2 of the THT drivers but in a sealed alignment than those same drivers in THTs.

If you want to know what kind of room gain you are getting, put a driver in a sealed box that you know the dimensions. Model it and then measure a sweep of it. Compare the curves and you will see what gain you have to work with.

With a graph like that I would have tried lowering the 20-80hz region 10db's and see how it sounds flat to 15hz.
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post #184 of 319 Old 03-21-2011, 01:27 PM
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Quote:
Originally Posted by coctostan View Post

IMO, you can't separate the room from the subwoofer. What are you room dims and does it have big openings?

Closed roomsingle door entry. Just under 2450 cu ft. (17x18x8)quite a bit smaller than your friend's 9K cu ft. room. Part of the appeal is the slightly smaller overall footprint of the cubes versus adding another 3x3x2 THT box to an already crowded space.

Quote:
Originally Posted by coctostan View Post

In a small room, I'd go with 4 MFW-15's sealed in a heartbeat over the THT. I don't really see the point of the THT in smaller rooms. IMO, if your room shows nice room gain, you'd be better off using 2 of the THT drivers but in a sealed alignment than those same drivers in THTs

I appreciate your opinions. Thanks!
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post #185 of 319 Old 03-21-2011, 05:22 PM - Thread Starter
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Kevin,

I agree with everything the other posters said. I dont think you would miss the tht if you build 2 duals, they should go lower by a good bit. As for shear 20hz plus output, I think my 4 duals does a fine job compared to my tht's, but its 8 drivers compared to 2, a testiment to the tht's design. I cant remember from your build do you have any eq? If you get sandbaggers amp, you may not have to boost the low end, depends what he has cooked up.

Wem
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post #186 of 319 Old 03-21-2011, 05:30 PM - Thread Starter
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Quote:
Originally Posted by smokarz View Post

thanks coctostan,

would the 18" cube give me a 2.5-3.0 ft^3 internal volume as suggested for this driver? sorry, i really don't have any clue about sub/speaker building.

also, what amps would you reccomend for two single subs? behringer ep1500? or ep2000? or something else?

I have a drawing for a roughly 2.5ft3 cab I will try to post tonight to give you any idea of what you are looking at.
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post #187 of 319 Old 03-21-2011, 05:44 PM
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No boost needed and we are going off a 2.5ft^3 box

Plus with the amp you will get single point PEQ and also a bass boost if you want it


Quote:
Originally Posted by wembley2000 View Post

Kevin,

I agree with everything the other posters said. I dont think you would miss the tht if you build 2 duals, they should go lower by a good bit. As for shear 20hz plus output, I think my 4 duals does a fine job compared to my tht's, but its 8 drivers compared to 2, a testiment to the tht's design. I cant remember from your build do you have any eq? If you get sandbaggers amp, you may not have to boost the low end, depends what he has cooked up.

Wem


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post #188 of 319 Old 03-21-2011, 05:56 PM - Thread Starter
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Quote:
Originally Posted by wembley2000 View Post
I have a drawing for a roughly 2.5ft3 cab I will try to post tonight to give you any idea of what you are looking at.
Here you go.

 

MFW15 2.5ft3.pdf 10.89453125k . file
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post #189 of 319 Old 03-21-2011, 05:56 PM
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Quote:
Originally Posted by Kevin A View Post

Closed roomsingle door entry. Just under 2450 cu ft. (17x18x8)quite a bit smaller than your friend's 9K cu ft. room. Part of the appeal is the slightly smaller overall footprint of the cubes versus adding another 3x3x2 THT box to an already crowded space.

I appreciate your opinions. Thanks!

In a closed off 17ft x 18ft room I'd definitely stick to multiple sealed. That is really not the best application for a THT. The sealed boxes will take up much less room. 4 MFW-15 drivers should get you flat down to 15hz at reference no problem. I'm not going to be as certain about 10hz but if I were a betting man I'd say you could get there too.

I think you will be very happy with 4 sealed MFW-15's in that room. You gotta have the right tool for the job.
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post #190 of 319 Old 03-21-2011, 05:58 PM
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Wouldn't you be using an LT circuit to flatten out the response? If so, is this not effectively a boost of the low end (not that there's anything wrong with that)?
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post #191 of 319 Old 03-21-2011, 06:20 PM
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Quote:
Originally Posted by vitaminbass View Post

Wouldn't you be using an LT circuit to flatten out the response? If so, is this not effectively a boost of the low end (not that there's anything wrong with that)?

I'm not sure which this post was in reponse to, but yes, you can use an LT circuit, or a high cut and parametric eq. Whichever gets you to the response you want. The bottom line is that with a sealed alignment you only have the drivers displacement to provide SPL at the lowest frequencies. Regardless of LT circuit or boost or cut, the MFW-15 is a 15" sub that can move 13mm.

The difference is in the room. A smaller room will see its response boost begin at a higher frequency and it will have more room gain at the lowest frequencies. This requires less boost (or potentially no boost) and therefore you need less from your drivers. Wembley has a mid sized room with openings and registers 4% THD at 10hz at reference levels with 8 MFW-15s. It is fairly easy to extrapolate some generalities about performance from there.
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post #192 of 319 Old 03-21-2011, 08:15 PM
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Quote:
Originally Posted by coctostan View Post
In a closed off 17ft x 18ft room I'd definitely stick to multiple sealed. That is really not the best application for a THT. The sealed boxes will take up much less room. 4 MFW-15 drivers should get you flat down to 15hz at reference no problem. I'm not going to be as certain about 10hz but if I were a betting man I'd say you could get there too.

I think you will be very happy with 4 sealed MFW-15's in that room. You gotta have the right tool for the job.
I do like the idea of using two smaller boxes with 4 drivers.

Plus I've got the bug to build again.

Now I just gotta find a local buyer for a well-built THT.
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post #193 of 319 Old 03-21-2011, 11:45 PM
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What is the ideal volume for these 15's?

I was thinking about a 19 or 20" cube with dual opposed side firing but just wondered if this was to small for below 20hz?(meaning if it wont reach 10hz)

Either way just curious. Its hard to pass the value of these things
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post #194 of 319 Old 03-22-2011, 04:38 AM - Thread Starter
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Quote:
Originally Posted by chrapladm View Post

What is the ideal volume for these 15's?

I was thinking about a 19 or 20" cube with dual opposed side firing but just wondered if this was to small for below 20hz?(meaning if it wont reach 10hz)

Either way just curious. Its hard to pass the value of these things

I believe you want at least 2.5ft3 min per driver. Any smaller and you will have to throw some high wattage at them to hit xmax, remember these drivers are only rated at 225 watts.
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post #195 of 319 Old 03-22-2011, 04:41 AM
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So wouldn't throwing higher wattage bring xmax sooner?
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post #196 of 319 Old 03-22-2011, 08:34 AM - Thread Starter
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Maybe I am not understanding your question. I dont have winisd in front of me but if one of these drivers will hit xmax at 225 watts in a 3ft3 box,and you add another driver to that same box with the same power wouldnt the drivers only move half as much due to the smaller volume? So in effect you would have to double the power to each driver to reach the same xmax, and you would be past the thermal limits of the driver. But I could be wrong or just misunderstanding.

Wem
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post #197 of 319 Old 03-22-2011, 09:05 AM
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Yeah, 2.5 cu ft is the minimum if you want to take full advantage of the driver's capacity. The smaller the box the more power it takes to reach xmax and get the full output of the driver. At some point the driver can't handle the power from a thermal perspective even if it is within its excursion range. These are not TC LMS's that can handle 3000w.

You pay for that kind of power handling and what it buys is the ability to get huge output out of a smaller space. You also need more power.

The MFW-15's give moderate output in moderate size boxes with moderate power at a low price. You get big output and deep extension you need the space for multiple woofers. Nothing is free, but some things are better values than others.
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post #198 of 319 Old 03-22-2011, 01:40 PM
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Ok understand now thanks.
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post #199 of 319 Old 03-22-2011, 03:46 PM
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Quote:
Originally Posted by sandbagger View Post

No boost needed and we are going off a 2.5ft^3 box

Plus with the amp you will get single point PEQ and also a bass boost if you want it

sorry coctostan, there were a bunch of posts all close together time-wise, I should have quoted sandbagger's post I was referring to.

Sandbagger, by your post above do you mean that no ADDITIONAL boost should be required because there is already a boost switch/circuit? Is this separate from LT circuit?

I'm interested in what you guys come up with. My current options:
1. Peavey IPR 1600+BFD--would easilly run two of these and the BFD would be flexible. Under $400 if I get the BFD used, but would add more components to my already-busy console.
2. Apex SR plate amps, one for each cabinet. Should have plenty of power, I believe there is LT and HP circuitry. $150/each.

But I also like the idea of an amp that has been custom tweaked just for this driver and cabinet.
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post #200 of 319 Old 03-23-2011, 06:36 AM
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Quote:
Originally Posted by vitaminbass View Post

sorry coctostan, there were a bunch of posts all close together time-wise, I should have quoted sandbagger's post I was referring to.

Sandbagger, by your post above do you mean that no ADDITIONAL boost should be required because there is already a boost switch/circuit? Is this separate from LT circuit?

I'm interested in what you guys come up with. My current options:
1. Peavey IPR 1600+BFD--would easilly run two of these and the BFD would be flexible. Under $400 if I get the BFD used, but would add more components to my already-busy console.
2. Apex SR plate amps, one for each cabinet. Should have plenty of power, I believe there is LT and HP circuitry. $150/each.

But I also like the idea of an amp that has been custom tweaked just for this driver and cabinet.

Sandbagger & I think a few others will find this an attractive and no hassle option as well. Kevin & I have been working on getting the response dialed in, and then we have some other final tweaking to do that will keep the amp and driver out of trouble. What Sandbagger meant in his post was that with the MFW-15 drivers in 2.5 cu.ft. sealed per woofer, the amplifier will have response correction to result in a 12dB/oct roll off with a +/-3dB window of 20Hz to beyond 120Hz (still tinkering). The frequency response will look like other sealed designs I've done including the 3 UFW-12 upgrade variants Sandbagger is already offering. This smooths the inductance hump and extends the bottom end making for a good match with many rooms. Since this response correction does not rely on the front panel PEQ or the rear bass boost switch, those are still available for the user, along with the very handy 12V trigger on back.

We will be optimizing for the amplifier to work well with 2 (series) or 4 (series-parallel) MFW-15 drivers in 2.5 cu.ft. per driver, with volumes up to 3 cu.ft. likely working just fine with a little more output down low. While the in-room measurements make it hard to see the original frequency response, I regularly find that the total power response driving the room (outdoor/ground plane response) is audible, and a smoother starting point makes for a superior subjective result. The amp Sandbagger will supply makes for a smooth and ready to play response with the MFW-15 drivers in a simple sealed volume. The addition of having the limiting set for the amp & drivers adds some peace of mind to those worried about bottoming drivers from scenes that might sneak up on them.

The components needed are available in a Behringer DCX-2496 and external amplification, but this is a ready to go option allowing the builder to move on to the integration with the room. While not the cheapest route to getting bass from the drivers, I feel it will make for a good value to some enthusiasts.

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post #201 of 319 Old 03-23-2011, 07:13 AM
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Mark-

Will these amps allow response down to 10hz and simply use a limiter to prevent over excursion or will there be a HP filter? I assume you will be implementing a LT circuit. Any idea of how much power each driver will see?

Edit: Hit send accidentally. I wanted to add that I think this will likely be a great option, especially for people who can't hide pro amps and their fan noise. Combined with Audyssey, most people will have no use for additional eq which is very nice.
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post #202 of 319 Old 03-23-2011, 07:55 AM
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While I am not mark, I am the other 1/2 of the sideshow

With 2 (series) or 4 (series-parallel) each driver should see about 250W as the amp puts out an honest 1000W into 4 or 500 into 8.

The changes I make to the limiter will keep the driver well within its excursion limits and keep it from making any bad noises.

While everything hasn't been hammered out yet but, there should still be plenty of output down at 10hz

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post #203 of 319 Old 03-23-2011, 08:53 AM
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Quote:
Originally Posted by coctostan View Post

Mark-

Will these amps allow response down to 10hz and simply use a limiter to prevent over excursion or will there be a HP filter? I assume you will be implementing a LT circuit. Any idea of how much power each driver will see?

Edit: Hit send accidentally. I wanted to add that I think this will likely be a great option, especially for people who can't hide pro amps and their fan noise. Combined with Audyssey, most people will have no use for additional eq which is very nice.

The response correction/EQ does not change the power available from the amplifier, just the input signal required to reach that power at a given frequency. I won't go so far as to call it an "LT" as it is not in a classic definition. The results are very similar to what Sandbagger measured outdoors and posted for the amp only and 15" upgrade to the UFW-12 from AV123 here in our forum. In case Bosso is watching, note I'm specifying +0dB/-6dB. There is a high pass in the chain, as I don't see any justification for these particular drivers flopping around at 3Hz for dino-stomps and alien thunderbolts. The 12dB/octave slope will be maintained to 7-10Hz allowing single digit extension in most dedicated theaters as others have seen.

Real impedance in the sealed box gives a little flexibility in the Voltage we can allow the amp to swing, but looking at nominal delivery of a series-parallel configuration you will see ~250W per driver with *each* 15" sealed driver having a performance envelope of roughly 113-116dB @ 1m gp in the 40-100Hz range with just over 100dB @ 1m gp at 20Hz. 4 drivers makes that 112dB @ 20Hz with the drivers remaining well behaved at +/-12-13mm. I haven't done outdoor max output measurements on the 2.5 cu.ft. sealed utilization of the driver, but reality will be within a 1-2dB tolerance window of most measurement variation.

Add in the practical use of protective limiting and you will have very strong useful output and this allows worry free listening at higher levels even when a brief blip might have otherwise left you cringing, checking voice coils or diving for a remote. To tie in the "Motor City" aspect, this setup comes with stability control and ABS... just in case.

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post #204 of 319 Old 03-23-2011, 09:00 AM
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Sounds good. My modeling appears to agree exactly with yours. Depending on price, this could be a great way to go.
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post #205 of 319 Old 03-23-2011, 09:21 AM
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Kevin & Mark,

If someone wants to go with 2 dual MFW15, does it mean new cabinets will need to be made?

Thanks,

Hugh
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post #206 of 319 Old 03-23-2011, 09:40 AM
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Quote:
Originally Posted by Mark Seaton View Post


The response correction/EQ does not change the power available from the amplifier, just the input signal required to reach that power at a given frequency. I won't go so far as to call it an "LT" as it is not in a classic definition. The results are very similar to what Sandbagger measured outdoors and posted for the amp only and 15" upgrade to the UFW-12 from AV123 here in our forum. In case Bosso is watching, note I'm specifying +0dB/-6dB. There is a high pass in the chain, as I don't see any justification for these particular drivers flopping around at 3Hz for dino-stomps and alien thunderbolts. The 12dB/octave slope will be maintained to 7-10Hz allowing single digit extension in most dedicated theaters as others have seen.

Real impedance in the sealed box gives a little flexibility in the Voltage we can allow the amp to swing, but looking at nominal delivery of a series-parallel configuration you will see ~250W per driver with *each* 15" sealed driver having a performance envelope of roughly 113-116dB @ 1m gp in the 40-100Hz range with just over 100dB @ 1m gp at 20Hz. 4 drivers makes that 112dB @ 20Hz with the drivers remaining well behaved at +/-12-13mm. I haven't done outdoor max output measurements on the 2.5 cu.ft. sealed utilization of the driver, but reality will be within a 1-2dB tolerance window of most measurement variation.

Add in the practical use of protective limiting and you will have very strong useful output and this allows worry free listening at higher levels even when a brief blip might have otherwise left you cringing, checking voice coils or diving for a remote. To tie in the "Motor City" aspect, this setup comes with stability control and ABS... just in case.

Do those numbers include colocation gain?

Also, are you recommending 2.5 or 3.0ft ^3ea? Seems like more extension would be the way to go...... Or are you concerned with taking up less real estate?
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post #207 of 319 Old 03-23-2011, 10:22 AM
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Quote:
Originally Posted by OnixMan View Post

Kevin & Mark,

If someone wants to go with 2 dual MFW15, does it mean new cabinets will need to be made?

Thanks,

Hi Hugh,

The discussion above is related to guys buying the remaining inventory of MFW-15 drivers Colombia and Eminence were left holding when AV123 folded. ErichH here on AVS picked up the ones Eminence had. This is also a good use of and means for those who get a Turbo kit to sell or re-purpose their drivers in a sealed sub using more drivers.

I guess you could put a dense plug in the port opening and just use the original cabinet which would be a little on the large side, but for an honest upgrade in output you would want to go to a pair of sealed drivers per vented MFW-15.

If someone want's to keep it really simple, the Dayton Audio SWC15 15" Subwoofer Cabinet is back in stock and is sized for a direct drop in of the MFW-15 driver (same frame size as the Dayton DVC 15"). It's 2.5 cu.ft. and if you want prettier/larger and don't mind routing the hole, you can get any of the 3cu.ft. sub cabinets from Parts Express. I expect most will roll their own, but options abound, and I *might* even try a simple concept with my cabinet shop some might find attractive.

Mark Seaton
Seaton Sound, Inc.
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post #208 of 319 Old 03-24-2011, 10:24 AM
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Do those numbers include colocation gain?

Also, are you recommending 2.5 or 3.0ft ^3ea? Seems like more extension would be the way to go...... Or are you concerned with taking up less real estate?

We are doing our initial development to work with a 2.5 cu.ft. box with a response that fits a 6dB window from 20-140Hz. The added 0.5 cu.ft. over 4 drivers make the system 2 cu.ft. larger, which can be significant to some. I believe more of those interested in the matched amplifier will appreciate the option of a bit less space. If you look at what you gain with larger boxes, I think you will see that the gains diminish for multiples the volume. The other factor is getting the most from the driver. For those who won't have 16 drivers in their room, the lack of concern of any over-driving is welcome, and I think it makes the solution a bit more attractive and practical for most. Upping the size to 3.5 cu.ft, is akin to adding another 20+" cube in the room between all 4. That added size ends up gaining you less than 2dB down low. 5 cu.ft. makes for a nice response that requires less EQ, but I'd want to test the drivers to see if you would have to worry about mechanical noises. I also figure any DIY can do the bigger boxes and the amplifier's cost isn't as well justified. The response shaping we do and the limiting we put in place will allow for a solution that most DIYers don't take the time to optimize to this level. Between the drivers Danny and EricH has and those jumping on the Turbo upgrade, there will be plenty of drivers out there for many to have some fun with this. For those going the Turbo route, they could easily cover the cost of shipping by selling off the original driver.

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Seaton Sound, Inc.
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post #209 of 319 Old 03-24-2011, 11:11 AM
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We are doing our initial development to work with a 2.5 cu.ft. box with a response that fits a 6dB window from 20-140Hz. The added 0.5 cu.ft. over 4 drivers make the system 2 cu.ft. larger, which can be significant to some. I believe more of those interested in the matched amplifier will appreciate the option of a bit less space. If you look at what you gain with larger boxes, I think you will see that the gains diminish for multiples the volume. The other factor is getting the most from the driver. For those who won't have 16 drivers in their room, the lack of concern of any over-driving is welcome, and I think it makes the solution a bit more attractive and practical for most. Upping the size to 3.5 cu.ft, is akin to adding another 20+" cube in the room between all 4. That added size ends up gaining you less than 2dB down low. 5 cu.ft. makes for a nice response that requires less EQ, but I'd want to test the drivers to see if you would have to worry about mechanical noises. I also figure any DIY can do the bigger boxes and the amplifier's cost isn't as well justified. The response shaping we do and the limiting we put in place will allow for a solution that most DIYers don't take the time to optimize to this level. Between the drivers Danny and EricH has and those jumping on the Turbo upgrade, there will be plenty of drivers out there for many to have some fun with this. For those going the Turbo route, they could easily cover the cost of shipping by selling off the original driver.

thanks mark!

more on plugging the originals, if you plugged from the inside(pulled the driver) the original shouldn't be that far off. . But like you said not really good use of that box.....
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post #210 of 319 Old 03-24-2011, 11:14 AM
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those of you using the ep4000 are you using a dedicated 20A line? I'm wondering at what point I I'm gonna have to do this, and putting more watts toward the subs is causing me some thought......
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