F20 vs Sealed Stereo Integrity 18 - Page 2 - AVS Forum
Forum Jump: 
Reply
 
Thread Tools
post #31 of 53 Old 04-25-2013, 10:54 PM
AVS Special Member
 
lilmike's Avatar
 
Join Date: Dec 2009
Location: Pacific Northwest
Posts: 2,163
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 73
OK, couple quick replies, then I'm out.
Quote:
Originally Posted by bradthebold88 View Post

"Stereo Integrity confirms that the power rating for this driver is based on the mechanical overload not what the coil will handle thermally."
This is on Ricci's page and why I felt safe using 1000W like others recommended in an excursion controlled sealed box.

While I have a ton of respect for Josh, he didn't make the driver. If you really think that 2 dB matters, by all means....

Remember - air compresses.... Sealed boxes can only do so much.
Quote:
Originally Posted by bradthebold88 View Post

I don't think I have said anything bad about the F20 in any way, I am just trying to find the max safe output for each sub. I have enough power to power either subs adequately, so power consumption was the lowest priority to me. And considering you can get used EP amps for the same price as a 500W plate amp, power is pretty cheap. The SI will definitely go lower, so I was mainly looking at how many SI's it would take to match the output of an F20 above 20Hz. Another big factor is that 1 F20 has the same external volume of 4 SI boxes. I'm not sure, but I think the F20 would have the distortion advantage.

No offense taken.
Just quit comparing apples and ducks as if they are equal, cause the numbers presented use the same units. I am certainly not defending the F-20's honor here. I designed it - I know all of its shortcomings...
The SI 18 is a great driver for the $$. The F-20 is a decently good horn sub, certainly worth every penny you pay for the plans. They are not the same thing.

As far as which direction you go and what you choose to do?

To each their own. Design something cool, build it, measure it, and then share the results so we all can learn.
Quote:
Originally Posted by bradthebold88 View Post

I don't really care what the max burst power is, I'm not sure how that data is even useful? I'm not sure how Ricci's max long term power measurement is useful if it's way over thermal limit and xmech either? The problem I had was assuming the long term power measurement was comparable to a reasonable amount of power to run with the SI, but it isn't.

For the goal, it doesn't seem like the F20 can be beat for price, distortion, output, or power usage.

You're too kind. It most certainly can. I have no doubt that someone will some day.
Quote:
Originally Posted by bradthebold88 View Post

For my limited floor space though, 4 SI's would have a lot more potential in the same volume, though they would cost a lot more. And so far I've needed two subs to smooth out the response in my room, so that would require 40cf of F20's to get a decent response. I am looking at all aspects of this, not just which one can I make the loudest.

The main reason I brought this up was because of the claim that the F20 had a more than 10dB output advantage compared to an SI at 25Hz when my interpretation of Ricci's data made it seem like the they should have the same output. Still though, based on my last graph (which still might not be accurate), the F20 only has a 5dB advantage at 25Hz, which is much different than >10dB.

At 20 Hz, it does. That was the statement, and models and measurements back this up. There is a significant difference "down low" and as room gain and boundary loading are alignment-agnostic, the differences in the room should be the same as the in 2pi space. If you can't see that from the data Josh and I have provided, as well as LTD's efforts in explaining things, further explanation on my part won't be of much help, so my time is better spent doing other things.
Quote:
Originally Posted by bradthebold88 View Post

I assumed 300W was the limit for the F20 because I think you have said that before. LTD02 was saying that was an underpowered model to compare with though.

The 300 watt limit is related to the combination of that particular driver in that particular cabinet. Other drivers in that cabinet can be fed more power, and as a result, they will make a bit more noise before power compression eats up the rest and turns it all into heat.

In the real world, with non-elite drivers, once you get past about 500 watts, adding more power just means more money spent fixing things when the moving parts hit the stationary ones or the magic smoke comes out, in other words - that means it is time to add more drivers.

1 watt to 500 watts nets you ~27 dB. 500 to 1000 only gets you 3 more, assuming that compression doesn't eat any of that up.
lilmike is offline  
Sponsored Links
Advertisement
 
post #32 of 53 Old 04-25-2013, 11:01 PM
AVS Special Member
 
lilmike's Avatar
 
Join Date: Dec 2009
Location: Pacific Northwest
Posts: 2,163
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 73
And - 2 of 2.
Quote:
Originally Posted by bradthebold88 View Post

Sorry, those were two kind of different questions that I stuck side by side and probably didn't word precisely enough. First I was just wondering if room gain affected horns the same as sealed subs, which you just answered. The second question was whether putting the sub in a room or in a corner would result in more useable extension below 20Hz compared to your outdoor measurements. I think your response to that question was that no placement would extend the F20's frequency response below 20Hz.

You're still not grasping what I am trying to communicate here.

No amount of room gain or boundary loading will change the horns TUNE. The RESPONSE in room may well go much lower, but the tune of the horn is set by the length of the horn, not the room you put it into.

As I have no idea what your room is, and no way to determine your room gain or boundary loading, I don't talk about what it might be.

Several people have measured their F-20's response extending well below the horn's tune in their rooms. That's great - if you have their room.... Since I don't.....

Best of luck with your project, whatever direction you decide to go.
lilmike is offline  
post #33 of 53 Old 04-25-2013, 11:33 PM - Thread Starter
Senior Member
 
bradthebold88's Avatar
 
Join Date: Jul 2011
Location: Denver, CO
Posts: 421
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked: 26
Thanks. That's clears up the frequency response question at the end. I think what I was trying to say was that it drops off pretty hard after the 20Hz tune and that room gain probably wouldn't be able to make up for it and give a good response below 20Hz. That depends on the room how the graph would look though. I wasn't aware anyone got better extension than 20Hz.

As far as LTD's quote, he said "more than 10db higher spl at 25hz". There is a big difference between the 5dB in the charts and more than 10dB, at least 4x the power, which is not insignificant. Even if the claim was at 20Hz, the 8dB difference there is still at least 2x the power difference from >10dB, which as you said is a significant power and driver risk increase.

I know there is a range of error comparing these two graphs though, and who knows, they could be off by 6dB which is a very significant power difference. It would be nice if someone who has both could measure them both with reasonable power. Or at least someone with the SI to measure it ground plane with a normal amp. (maybe there is one besides Ricci's I haven't seen?)

I think I am going to go with 4 SI's for the better extension and fact that they take up less than half the volume that 2 F20s would. I'm sure my girlfriend won't be entirely happy about 16cf of subs in the living room. A pair of 5ft, 20cf towers would get me in trouble. 4 SIs should get me into the output range of 2 F20s though. The 4 SIs and extra amp are about $1000 more than building F20 boxes for my Daytons, so it's kind of a tough choice. I'm pretty sure the Daytons will go into F20's for my brother though, so I would at least get to experience them in different rooms.

I've considered building an F20 and testing my 15" Dayton HF against an SI, but even using particleboard, which seems like the cheapest 4x8 sheet of anything, would be >$50 in wood. Using ply would put it closer to $75 or $100 just to test something I wouldn't keep.

Living room: Definitive BP2000TL, CLR3000, BPVX, Quad SI 18" subs
Bedroom: Definitive BP30, CLR2000 Also have had: BP7000SC, BP8B, BP10B, BPX, Dayton 15" HF subs, Rythmik F15
bradthebold88 is offline  
post #34 of 53 Old 04-25-2013, 11:40 PM
AVS Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 15,935
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Liked: 840
"John that is 200v peak and 125A... per channel..."

roger. i should have caught that. the spec of 8000w into 8ohms bridged is 252v rms, so about 357 peak. figuring the caps have enough juice for one full peak to peak burst cycle peaking at 400 volts eek.gif, that is about 45,000 watts and 114 amps peak (not rms) into 3.5 ohms, so i guess it wasn't amp limited after all.

Listen. It's All Good.
LTD02 is online now  
post #35 of 53 Old 04-26-2013, 12:04 AM
AVS Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 15,935
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Liked: 840
"As far as LTD's quote, he said "more than 10db higher spl at 25hz". There is a big difference between the 5dB in the charts and more than 10dB"

sorry. brian's original question was about 750-1000 watts at hand. i assumed the mfw driver which was originally used in a commercial design with a 500 watt amp could take 750. 750 watts into each give about a 10db difference at 25hz and about 6db advantage to f20 in the upper frequencies.

Listen. It's All Good.
LTD02 is online now  
post #36 of 53 Old 04-26-2013, 12:14 AM - Thread Starter
Senior Member
 
bradthebold88's Avatar
 
Join Date: Jul 2011
Location: Denver, CO
Posts: 421
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked: 26
Ah, that makes sense, thanks.

Living room: Definitive BP2000TL, CLR3000, BPVX, Quad SI 18" subs
Bedroom: Definitive BP30, CLR2000 Also have had: BP7000SC, BP8B, BP10B, BPX, Dayton 15" HF subs, Rythmik F15
bradthebold88 is offline  
post #37 of 53 Old 04-26-2013, 08:05 AM
AVS Special Member
 
Looneybomber's Avatar
 
Join Date: Sep 2006
Location: Lawrence, KS
Posts: 4,666
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 23
Quote:
Originally Posted by LTD02 View Post

"John that is 200v peak and 125A... per channel..."

roger. i should have caught that. the spec of 8000w into 8ohms bridged is 252v rms, so about 357 peak. figuring the caps have enough juice for one full peak to peak burst cycle peaking at 400 volts eek.gif, that is about 45,000 watts and 114 amps peak (not rms) into 3.5 ohms, so i guess it wasn't amp limited after all.

In one of my circuits classes, when talking about 3 phase power and industrial loads, they used numbers fairly close to what you're using.
*insert pic of burning house here*

YID DIY
Looneybomber is offline  
post #38 of 53 Old 04-26-2013, 09:26 AM
AVS Addicted Member
 
MKtheater's Avatar
 
Join Date: Jul 2006
Location: New Hartford, NY
Posts: 14,204
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 93 Post(s)
Liked: 403
The F-20 is a sealed horn. In my room it rolled off under tune just like a sealed sub so under tune the SI 18 will have the clear advantage because you are comparing a higher excursion 18 vs a lower excursion 15. Now within the horn path the 15 gets a significant boost and why it has more output. Yes, 4 SI's can fit in the same enclosure but now you need more amps and all this costs much more money. Everyone pretty much knows that multiple sealed is the best way to go if money is not a factor because you just keep adding drivers and power to reach spl goals. The horn gets you the loudest and cheapest for a single box. For an example, I had 4 F-20's in my room and it cost about $1200 total with amps. It gave me flat to 15hz in room and reference from 15hz and up. My sealed system takes up less room and has much more output below 15hz but cost 3x as much. Both gets the job done but if you want lower it costs more money. My sealed system also has more output above 15hz too but again it costs lots more. Here are the two different systems with both pics and THD numbers.

Here are the 4 F-20's



This is what I got at the LP

Compression sweeps with no EQ



Here are THD at 10% graphs







Lets now compare it to a multisub sealed system(8x18)



Here are the 10% THD sweeps







Then I switched to smaller drivers but with more x-max and less rolloff down low. (13x12) Also more drivers to make up the displacement above 20hz.







MKtheater is online now  
post #39 of 53 Old 04-26-2013, 10:21 AM
AVS Special Member
 
Ricci's Avatar
 
Join Date: Mar 2007
Location: Louisville KY
Posts: 5,081
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 186
Quote:
Originally Posted by LTD02 View Post

"John that is 200v peak and 125A... per channel..."

roger. i should have caught that. the spec of 8000w into 8ohms bridged is 252v rms, so about 357 peak. figuring the caps have enough juice for one full peak to peak burst cycle peaking at 400 volts eek.gif, that is about 45,000 watts and 114 amps peak (not rms) into 3.5 ohms, so i guess it wasn't amp limited after all.

Well again I am not sure exactly what it will burst into 4 ohms bridged but I just assume it is somewhere near 280-300v and leave it at that. And yes even with this the amplifier is still the limiting factor in some of the burst tests. Above 50Hz almost every long throw sub will briefly take everything the amp has without going past xmax. Some of the bruisers like the XXX will take the entire amp below 20Hz in a burst in the 4 cube sealed test box without damage.




As far as the OP's questions...Yes this really is an apples versus potato's comparison. First off I can guarantee that If I tested an F20 the way that I do I would get a few more dB out of it for sure. As Mike says he is not in the habit of blowing drivers and he was using a tiny amp comparatively, not to mention the differences in test gear, calibration and setup.

The max long term sweeps are not supposed to be a power recommendation. None of the DIY systems sound pleasing or ok during their loudest sweep and neither do most of the commercial units which have high pass filters and limiters set. There are usually bad excursion or vent noises and all sorts of distortions. Those tests are to show whether the system responds to power in a linear manner and when and where it starts compressing the output whether due to driver/PR/vent/horn throat non linearity, thermal compression or whatever. This test is only stopped when either A. The compression reaches 3dB or greater broadband. B. The driver makes clear mechanical distress noises. C. The amplifier runs out of power. These sweeps are ascending sine sweeps starting at 2Hz and ending at 240Hz and they last for >22 seconds. The drive level starts at a level that produces 90dB at at 2M at 50Hz from the system. The sweep is repeated back to back with only a few seconds of down time in between and the voltage is increased 1.78x for each subsequent sweep until conditions A,B or C are met. Often more than one of these conditions occur at the same time during the last sweep. Usually the last sweep will be increased a smaller amount as the system would clearly not survive the next full 1.78x voltage increment. This is a brutal test and I have killed drivers doing it by not gauging when to stop or how much to increase the volume for the final sweep. These are 100% duty cycle signals so they are much more brutal than any typical content listened to. Even heavily compressed electronic music is only like 25% duty cycle at most. None of the systems will handle sine wave power equivalent to that used during even the second strongest long term sweep for any length of real time without getting fried. Since music is a lower duty cycle the system would handle these power levels longer than with the sine sweeps but how long depends completely on the content. I would suggest that the max long term sweep that is the next power level down or even 2 would probably be safe with typical content but again there are so many variables that it is difficult to say for sure. I really do not listen to things run at the edge for long duration so i have had good luck using amps that have loads of power and using it to reach greater short term peak outputs. Some other guys have a heavier hand on the volume knob and seem to push things with EDM for hours straight in which case the same overpowered amps I would use could easily fry the driver. Also most of us don't like to be running things at the ragged edge all of the time because it shortens your equipments life span and it just doesn't sound as good when things are strained.

So what is the point of these tests? Well... The max long term sweeps show you where and when the system compresses, how loud it will go at maximum prior to blowing up or melting, distortion, the effects of voice coil heating etc...This is using a 100% duty cycle signal that has the power increased each time. This is the absolute worst case signal and how the system responds to it. CEA-2010 is the opposite and is in some ways the best case signal of a bandwidth limited very short duration "blip". This allows the system to reach its maximum output potential without the thermal effects and danger of melting something and is another way of looking at distortion in the system, while setting the limits of the output to be that of the driver sensitivity, linearity, distortion and mechanical clearances. We want all of these tests to not be limited by the amplifier and to have the system being tested be the final limiting factor as much as possible,so that is why the ridiculous amount of power and the 240v 50A line. Otherwise you would be testing amp limitations as well. It may not be a realistic amount of power to supply to these systems but what is? 1000w? 2000w? Mfgr's rated power? Peak or program? Just 1W?

Also note that both the CEA-2010 and the sine sweeps will have the voltage listed going forward so that power applied can be calculated. Don't forget that there is going to be significant impedance rise at the higher power levels though. I guess the moral of the story here is that this stuff is a lot more complicated than a few output graphs and the CEA-2010 and max long term graphs are not a representative of what you can get out of the driver in your system unless you are well versed in advanced limiter and protection settings in the amplifier. These tests should be thought of as absolute maximum "potential" output levels past which damage occurs in very short order. The actual output you want to be using from the systems is about 6dB down from there. wink.gif
Ricci is offline  
post #40 of 53 Old 04-26-2013, 12:51 PM
AVS Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 15,935
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Liked: 840
josh, nice write up. that or something similar would make a great link for the website "how to interpret the long term test results".

Listen. It's All Good.
LTD02 is online now  
post #41 of 53 Old 04-26-2013, 12:56 PM
AVS Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 15,935
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Liked: 840
mk, nice post.

i'm a little surprised at the 8x18" performance at 20hz. seems like that number should have been much higher even with the modest throw of the drivers employed. any idea what was going on there?

Listen. It's All Good.
LTD02 is online now  
post #42 of 53 Old 04-26-2013, 01:57 PM - Thread Starter
Senior Member
 
bradthebold88's Avatar
 
Join Date: Jul 2011
Location: Denver, CO
Posts: 421
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked: 26
Thanks for the explanation Ricci, that makes a lot more sense now.

And thanks MK, so it looks like 8 SIs is comparable to 4 F20s, which is what I would expect now. If I read your graphs right.

So it looks like 2 SIs vs 1 F20: the F20 has a little more output at 20Hz, but the SIs would have a little more above and a lot more below that. The SIs would take up half the space and look nicer, but would cost about twice and much for drivers and amps. 4 SI's would also give me the ability to run them in 4 separate spots if I needed a better response in a future room.

The tradeoff is double the space, less low frequency extension, looks , and placement of the F20 vs double the price (or more) for double the drivers and amps for the SI's.

If this were for a theater, I would probably go with the F20's because I already have drivers and amps, I would just need to build boxes. A pair of F20s is pretty massive for a living room with a girlfriend though.

Living room: Definitive BP2000TL, CLR3000, BPVX, Quad SI 18" subs
Bedroom: Definitive BP30, CLR2000 Also have had: BP7000SC, BP8B, BP10B, BPX, Dayton 15" HF subs, Rythmik F15
bradthebold88 is offline  
post #43 of 53 Old 04-26-2013, 03:10 PM
AVS Addicted Member
 
MKtheater's Avatar
 
Join Date: Jul 2006
Location: New Hartford, NY
Posts: 14,204
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 93 Post(s)
Liked: 403
My 20hz was surprising as well but it could have been room noise or something. It was violent in my room with that sweep! These are CHT 18's and you can see how they do in a ported cab on the Data bass site for a direct comparison and then you can get an idea how the F-20's would do.
MKtheater is online now  
post #44 of 53 Old 04-26-2013, 03:51 PM
Advanced Member
 
Decadent_Spectre's Avatar
 
Join Date: Sep 2005
Posts: 897
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 10 Post(s)
Liked: 18
Quote:
Originally Posted by MKtheater View Post

Everyone pretty much knows that multiple sealed is the best way to go if money is not a factor because you just keep adding drivers and power to reach spl goals.

This is a matter of opinion and not fact as you seem to portray. Sealed is the best way to go IF and ONLY IF you want to get to 5Hz in a small room, above 20-40Hz horns dominate, depending on the design of course. Some horns can destroy 8x sealed LMS with a single cabinet in their pass band. Sealed are best used as air pumps in small rooms for HT, which is what they are used for typically on this forum but your blanket statement is incorrect unless this is what you meant.
Decadent_Spectre is offline  
post #45 of 53 Old 04-26-2013, 04:00 PM
AVS Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 15,935
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Liked: 840
"The SIs would take up half the space and look nicer, but would cost about twice and much for drivers and amps."

didn't i say something along those lines in the thread that you grabbed my quote from? :-)

i think you made the right choice for your situation. some sort of eq to bring up the bottom end would be a good idea if you haven't already identified a solution.


"My 20hz was surprising as well but it could have been room noise or something. It was violent in my room with that sweep!"

ah, that would definitely make sense.

Listen. It's All Good.
LTD02 is online now  
post #46 of 53 Old 04-26-2013, 04:27 PM
AVS Addicted Member
 
MKtheater's Avatar
 
Join Date: Jul 2006
Location: New Hartford, NY
Posts: 14,204
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 93 Post(s)
Liked: 403
I am always talking about full bandwidth HT so remember that when I say multiple sealed. Just look at the difference at 10hz with the 13's. I would need 32 F-20's for the same output at 10hz so for low end sealed is much better. Of course you could build a 10hz horn but it would be very big and may not fit. Again, dedicated room for HT.
MKtheater is online now  
post #47 of 53 Old 04-26-2013, 04:32 PM - Thread Starter
Senior Member
 
bradthebold88's Avatar
 
Join Date: Jul 2011
Location: Denver, CO
Posts: 421
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked: 26
That thread was confusing. You said what you said, one guy said you would need 4 18's to match an F20, one guy said they should be the same, hence my initial confusion.

Audyssey alone bumps my low end up ~8dB and makes my current Daytons flat to 10Hz in my room. They can only take 210W before exceeding xmax in the mid 30Hz area though, which I why I am looking to upgrade. I run a 20Hz HPF which can still exceed xmax by a good good bit with ~650W/ch with the EP4000, so I'm wasting the extension anyways.

I am still having a hard time choosing the SI's though. Building F20s would only cost wood, the SI's would cost >$1000 and running two EP4000s on a 15amp line with the rest of my home theater stuff might cause issues.

If I went with F20s, there's no way to limit the output of the EP4000s is there? So there is no way I could prevent sending them twice the recommended power for the box using the amp I already have.

Living room: Definitive BP2000TL, CLR3000, BPVX, Quad SI 18" subs
Bedroom: Definitive BP30, CLR2000 Also have had: BP7000SC, BP8B, BP10B, BPX, Dayton 15" HF subs, Rythmik F15
bradthebold88 is offline  
post #48 of 53 Old 04-26-2013, 04:43 PM
AVS Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 15,935
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Liked: 840
"If I went with F20s, there's no way to limit the output of the EP4000s is there? So there is no way I could prevent sending them twice the recommended power for the box using the amp I already have."

depending on which specific driver you use, you might be able to wire them in series for something like 8 ohms and run either bridged or off one channel, whichever provides the right amount of power.

Listen. It's All Good.
LTD02 is online now  
post #49 of 53 Old 04-26-2013, 05:07 PM - Thread Starter
Senior Member
 
bradthebold88's Avatar
 
Join Date: Jul 2011
Location: Denver, CO
Posts: 421
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked: 26
Quote:
Originally Posted by LTD02 View Post

"If I went with F20s, there's no way to limit the output of the EP4000s is there? So there is no way I could prevent sending them twice the recommended power for the box using the amp I already have."

depending on which specific driver you use, you might be able to wire them in series for something like 8 ohms and run either bridged or off one channel, whichever provides the right amount of power.

I have the 4-ohm 15" Dayton HF. If I wire them in series that would work off one channel, but then I wouldn't be able to set the delays separately or run them in different spots. I'd either have to run them both in the same spot or deal with them being a bit out of phase and running a 15ft wire between them.

If I salvage my current boxes for polyfill and binding posts and sell the Daytons to my brother I could probably save ~$300 towards the SI's. Or 300W plate amps are on sale for $120.

Living room: Definitive BP2000TL, CLR3000, BPVX, Quad SI 18" subs
Bedroom: Definitive BP30, CLR2000 Also have had: BP7000SC, BP8B, BP10B, BPX, Dayton 15" HF subs, Rythmik F15
bradthebold88 is offline  
post #50 of 53 Old 04-27-2013, 09:59 AM
AVS Special Member
 
lilmike's Avatar
 
Join Date: Dec 2009
Location: Pacific Northwest
Posts: 2,163
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 73
Quote:
Originally Posted by bradthebold88 View Post

I have the 4-ohm 15" Dayton HF. If I wire them in series that would work off one channel, but then I wouldn't be able to set the delays separately or run them in different spots. I'd either have to run them both in the same spot or deal with them being a bit out of phase and running a 15ft wire between them.

If I salvage my current boxes for polyfill and binding posts and sell the Daytons to my brother I could probably save ~$300 towards the SI's. Or 300W plate amps are on sale for $120.

Well - I said I'd bow out of this thread, cause I felt I had nothing left to contribute. The power handling and amp question is something I can respond to.

If you were to go with the F-20, you could use your existing drivers and should be able to safely power them with the EP-4000.

Chuck's testing shows that an EP2500 makes ~600 RMS into 4 ohms. The EP4000 is essentially the same amp, just re-badged and re-rated at 1% THD, vs 0.1% THD.
The F-20 with the HF would have an impedance no lower than 4 ohms, it would actually average more than that, so the amp would deliver a bit less power.

The HF should work fine loaded in an F-20 with an EP-4000 wired in stereo. Get something like a balanced MiniDSP to handle the suggested highpass and any needed sub EQ.
lilmike is offline  
post #51 of 53 Old 04-27-2013, 10:26 AM - Thread Starter
Senior Member
 
bradthebold88's Avatar
 
Join Date: Jul 2011
Location: Denver, CO
Posts: 421
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked: 26
Ok, I was just going off this that you said, "I'd power the RSS390HF with 300 watts personally."

But if you say it'll work fine, that is even more tempting. I'm not sure how to model a horn though, so I didn't know at what power it would run to excursion or some other problem.

I already have a MiniDSP, so it would only cost me wood to try it. Can I use the Home Depot cabinet grade ply for this because it's cheaper, or is it still important to use better quality wood with a horn as well?

Living room: Definitive BP2000TL, CLR3000, BPVX, Quad SI 18" subs
Bedroom: Definitive BP30, CLR2000 Also have had: BP7000SC, BP8B, BP10B, BPX, Dayton 15" HF subs, Rythmik F15
bradthebold88 is offline  
post #52 of 53 Old 04-27-2013, 11:40 AM
AVS Special Member
 
lilmike's Avatar
 
Join Date: Dec 2009
Location: Pacific Northwest
Posts: 2,163
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 73
Quote:
Originally Posted by bradthebold88 View Post

Ok, I was just going off this that you said, "I'd power the RSS390HF with 300 watts personally."

Remember the rest of the context there. If I recall, dutchswan was buying amps to power 4 F-20s that he was using to fill a space that has more square feet than my house, and was worried about having enough power. There is 2 dB of difference between 300 and 500 watts, but the driver is seeing nearly double the excursion and thermal loading. Buying the bigger amp really isn't worth it in my opinion, especially when they'll never see clip lights in normal use.

That being said...if I had the drivers and I had the amp? Sure, I'd use them. Just set your highpass properly, and don't run 19 Hz sine waves. Things should be fine in normal use.
Quote:
Originally Posted by bradthebold88 View Post

But if you say it'll work fine, that is even more tempting. I'm not sure how to model a horn though, so I didn't know at what power it would run to excursion or some other problem.

I already have a MiniDSP, so it would only cost me wood to try it. Can I use the Home Depot cabinet grade ply for this because it's cheaper, or is it still important to use better quality wood with a horn as well?

Modeling is only part of the answer.

Here is the excursion predicted at 600 watts to a cabinet:



The model says you're just over xmech below 20 Hz, but the model is based on small-signal Thiele-Small parameters, and these parameters are not constant. In reality? Well, the suspension stiffens up with more excursion, and the motor's force decreases as the coil leaves the gap, so things should work a bit better in the real world.

How much better? Don't know, as I have not tested any driver to it's actual limits in the F-20, and for the reasons stated earlier, I don't intend to.

If I attached the SPL plot of that same model, it indicates that 2 of the F-20s, placed in an acoustically perfect corner, fed with 600 watts will make over 135 dB at a meter. So what?

If you really want to put up big SPL numbers, you could send the driver full power at about 40 Hz, if I recall, someone did that a while back.

Max SPL numbers are something that is best relegated to marketing copy, sort of like peak amplifier output. Ricci has shown that in the short-term, drivers are capable of handling immense power. Again - so what?

Peak numbers just don't matter in day to day use. How are you really going to use it? 120 dB at the seats is LOUD. A pair of F-20s will deliver that in a typical room, and should do so all night long.
More than 120 dB at the seats? Well, hope the neighbors are friendly...that or a long ways away.

As far as ply, I'm not familiar with the cabinet-grade offerings at Home Depot. Can you get the CFP purebond poplar that my local Home Depot has? It's about $36 a sheet, which is cheaper than Arauco locally, and it looks like decent stuff. It is also sustainably plantation grown, and made in the USA, which is cool. It has a cross-banded poplar core, so it should be plenty strong. I have three sheets that I need to cut up and turn into MicroWrecker #2 one of these days. I have no idea how it cuts or takes screws yet. Hopefully, it works similarly to Arauco.

When it comes to materials and construction, horns are really no different than any other cabinet. It's gotta be airtight, wood quality counts, and you need to use bracing.
lilmike is offline  
post #53 of 53 Old 04-27-2013, 11:57 AM - Thread Starter
Senior Member
 
bradthebold88's Avatar
 
Join Date: Jul 2011
Location: Denver, CO
Posts: 421
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked: 26
Ok, thanks, that helps. I'm not worried about running full power constantly, I just want to make sure if I clip the amp at 20Hz during a loud scene it wouldn't violently bottom out and destroy the driver or something like that.

I have one other question right now. Do horns have to go in corners as part of their design? I only have one 90 degree corner in my room and that's the only corner a sub could go in. My other sub is in the middle of a wall. Trying to search for that didn't give the info I was looking for.

And the cabinet grade ply is 11ply stuff with a thin veneer for $35. The Arauco here is $50 and had as many voids as the HD stuff, but people said to use the Arauco anyways for the sealed boxes I was looking at. I will look into the purebond poplar.

Living room: Definitive BP2000TL, CLR3000, BPVX, Quad SI 18" subs
Bedroom: Definitive BP30, CLR2000 Also have had: BP7000SC, BP8B, BP10B, BPX, Dayton 15" HF subs, Rythmik F15
bradthebold88 is offline  
Reply DIY Speakers and Subs

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off