Alpine SWR-1223D DIY Sub Build For HT

"This is my first time with WinISD so I am not too sure if I am doing it right."

what did you come up with in winisd?

i really don't see anything wrong with your models there. i've got 20mm for xmax on the swr, you've entered 17mm but you have 20mm in your op.

with a ported, you need a high pass filter around 20hz or so. most plate amps come with something like that built in, so the excursion won't blow up as in the model.

that's tough to answer because it depends on where your electronics rolloff, how much power you will be putting into the system, and the content. the lower tuning also results in more driver excursion above the tuning point, so keep an eye on that too.

LTD02, is giving you the right advise... Basically, he's saying that you need to play around with it in WinISD to find out how a lower tuning will change the model. The one flaw with your ported vs. sealed graphs are that your ported model doesn't have a HPF on it so you're looking at an incorrect model. Add a HPF and then compare the two to see what you want to do. I have an XLS2500 and just ordered a Balanced MiniDSP for the HPF option, as well as, other features. I'm building two 10" sub boxes for my theater and the ported model blew away the sealed model in all areas except the sealed has the advantage in frequencies below 15Hz. At 20Hz the ported design is at 110.8dB vs 99.5dB for the sealed model. Those numbers are only for one sub. I'm building two since I already have two and the crown is a two channel amp. With two you can add 6dB to each of those numbers which means that the ported design model will be ~116dB at 20Hz! That's not bad in my book for two 10" subs! That was what I needed to see and couldn't justify building the sealed boxes. The only downsize to the ported boxes is that I had to make them 4.5^3 ft. vs 1.3^3 ft. for the sealed. So there's the cost of more wood and the additional complication of making the ports. There's also the additional cost of $175 for the MiniDSP plus wires and cables to connect to the MiniDSP. So what I'm getting at is that it'll cost more to build a ported vs a sealed design as there's no cone control below tuning but most likely you're going to want to eq the sealed box to tame the peaks and nulls so you'll end up getting the MiniDSP anyway. That leave the only real difference of having a bigger box, the cost of more wood and the additional complication of making the ports.

Basically, what I'm trying to say is that if you're only building one 12" sub box. I think that you're going to be pretty disappointed if you build the sealed design as it won't have the output that I'm sure you're looking for but it'll roughtly cost you an additional $200 american dollars (the cost of a MiniDSP) to build a ported design.

BTW, don't forget to add a HPF to your ported model so that way you're making a proper informed decision.

That may be true but what will happen to your sub when a movie hits an frequency that low or lower? It appears that it'll be fine but to me it seems like a bit of a gamble. If you don't mind possibly blowing out your sub then do it and take the chance. Just remember that you modeled your sub at 600w of input power. That continuous watts and not peak. Remember that your amp could put out more watts for a short burst. I'm still building my subs so the amount of help I am to you is minimal but regarding the crown amps I can't tell you exactly how many watts it'll put out but it's not going to be that much less that what they stated. There's a thread on here somewhere discussing exactly what you're asking me... How to calculated 1 Khz ratings into 20Hz-20Khz rating. I think it was ~15% less power than stated or something along those lines. Also, you said that you're signal going to the crown is from a denon avr. That denon avr is probably not going to put out enough volts out of the preamp. You have a consumer product being connected to a pro product. While it may work you're not going to get the full output from that amp either. I had the same problem with my XLS 2500 and my onkyo processor. It sounded good but I had to crank the levels way up to get any decent output. I then bought a samson s-convert and it literally sounded like the power double without any adjustments to the levels so you have to take that into consideration as well. If your XLS 1000 is putting out 550w at 2-Ohms then just going directly to the crown considering the loss of voltage you might only be putting out 300-400watts. I don't know for sure I'm just giving an example. There's tons of threads on here discussing pro amps being connected to avrs and the lack of voltage required to get that pro amp to work at full capacity. Again I'm fairly new to all this but regarding controlling amplifier power I always thought of it as being if your avr is at 50% volume then the amp should be at 50% power. I don't know if that's exactly correct but seems perfectly logical to me.

Again, I'm not as educated on these things as other people I'm just rying to give you whatever knowledge that I might have.

Running a ported sub without a high pass is pretty risky for home theater I think. Unless you know that specific movie you are about to watch doesn't have any content below 20hz and be careful of the volume knob. There are a few movies that go down to 10hz but those are pretty rare, I can only think of Hulk right now. I use a Denon 2312 with a EP2500 and puts out more than enough volts. The gain knob on the amp is set to about 1/4 of the way. I measured the lfe output with a multimeter and I was able to get 4.8v with the sub output at +12. You can test this yourself, find a 60hz test tone and measure the lfe output with a multimeter.

Edited by Mrkazador - 12/2/12 at 12:59pm

At volume 00 I get 1.4v with the subwoofer trim level at 0. The input sensitivity of the EP2500 is 1.23v. Not to derail your thread but that should be ok...right? The amp is turned a 1/4 of the way and my subwoofer trim is at -5 on the receiver.

"At volume 00 I get 1.4v with the subwoofer trim level at 0. The input sensitivity of the EP2500 is 1.23v. Not to derail your thread but that should be ok...right? The amp is turned a 1/4 of the way and my subwoofer trim is at -5 on the receiver."

yes. "input sensitivity" on pro amps means the amount of voltage necessary that must be provided by the receiver into the pro amp in order to hit the rated max output of the pro amp.

example: let's say an amplifier "amplifies" the input signal by 40 times and has a maximum output signal of 60 volts. you would need to put in 1.5 volts in order to get the full potential of the 60 volts output. if you only input 0.5 volts, then the amp can only boost it to 20 volts, which is below its capability.

"input sensitivity" is not a very intuitive concept for a person new to all of this, so it is a good question.

I have a feeling I'm doing it all wrong lol. If I get 1.4 volts at 0db, my subwoofer trim should be at 0 or close to it, not -5. I found this guide with lots of information which I have to try out one day.

http://www.hometheatershack.com/forums/home-theater-receivers-processors-amps/35677-gain-structure-home-theater-getting-most-pro-audio-equipment-your-system.html#axzz2E1idn4NA

braveheart, those setup steps seem about right to me. At least, that's what I would do. I always find it funny when people say that they calibrate their system at -6dB and what not. I can't even get close to that without blowing out an ear drum. I use my onkyo 885 test level setting and all my speakers are putting out ~82-83dB at that level. Rather than bump all the levels down equally to reach 75dB I just calibrate the system to those levels. After all we really just want each speaker playing at the same level. I usually watch movies at -19dB on my onkyo and it's plenty loud. One time, I connected the crown xls 2500 to my mains I couldn't get any louder than -30dB on the onkyo with the crown gain halfway up. At those levels my radioshack meter was reading 100dB. Mind you I have a small living room and sit about 9 feet from my mains. It was still very loud and my ears were ringing pretty good after that. My downstairs neighbor was with me when I was doing that test and he was drooling at my modest system. I'm sure that my system is nothing compared to what a lot of you guys have on here though.

There is a major mistake in logic that often occurs when using the receiver test noise to set gain structure especially when making assumptions that there is not enough voltage potential available for your pro amp to produce its maximum output.

The internal pink noise signal is -30dB from the potential output a main channel may be asked for and for the sub channel -40dB from the potential output. If considering redirected bass from 5 main channels as well this signal is -48dB lower than the potential maximum signal strength. A VERY weak signal compared to what you experience with actual movies or music and intentionally so. Pink noise at even 75dB is very annoying that is partly why the calibrations signals are very much reduced in level.

If a 75dB signal requires 1v from the output... A maximum level 123dB signal out of the SW jack at REF level will require >250 volts. This is equivalent to an increase of 63,100 x the power.

You should never use the internal pink noise signal for calibration to determine if your pre-pro/ receiver has enough voltage for your amp to reach full output. It is far too tepid of a signal. Even with the master gain maxed out and the channel trim maxed out it will still be about 20dB weaker than the potential that is there in movies. Your receiver output will be far from clipping at this output. Whatever signal is used should be strong. A 0dB sine wave tone input into the system instead is much better. You are testing for maximum voltage like when a bomb blows up in Batman and you have it cranked and whether your receiver is going to clip without the amp getting enough juice to produce full power. What you are not testing for are the tiny voltages that occur when the weather channel is on at -40dB on the master dial. Should your 2000w pro amp be slamming your subs and clipping when watching the weather channel at -40? Of course not so why would you expect to get this result with such a signal? If you are judging this stuff on the basis of the internal calibration noise in the receiver this is essentially what you are doing. You want to push the preamp output with a very hot signal to the point that it is clipping and see if that is enough to get the amp into clipping. Usually the amp will have run into clipping long prior to the receiver hitting clipping and the amp can be run with the trims turned way down indicating absolutely no reason to use a booster. I have never needed one with any pro amp or receiver I have used and there have been a LOT of different brands.

Of course signal boosters boost the signal. That is exactly what they are designed to do. That does not mean that they are needed in most cases. They also will boost any hum or line noise as well so if you do not need more clean voltage than the electronics ahead of it in the chain can provide you are only degrading the signal by introducing it.

I only mention this because i have seen a lot of guys make this mistake. Moral of the story is that you need to determine the maximum output potential of the preamp output. This is why this should always be done with all speakers disconnected. if you stop prior to either amplifier clipping or preamp output clipping you do not know if you have enough voltage or not.
Edited by Ricci - 12/4/12 at 11:05am

Josh,

What's a good way to identify the max clean sub signal output the AVR is capable of? How do I tell that the preamp is clipping?

thank you

Use a free audio measurement program like REW that has a signal generator and an RTA. Run the audio out of your pc into the receiver aux in. Set the signal generator for a sine wave. 60Hz is good for bass. The SW output should be run back into the pc or sound card and monitored with the RTA. Crank up the output until the distortion jumps dramatically this is the onset of clipping. You will see the sideband harmonics jump up. REW will even tell you the THD% real time. 1% is a good stop point. First start by ensuring that you aren't clipping the input to the pc or sc so set it at minimum gain. Before turning up the receiver levels turn up the output signal from the audio program and sc with the receiver output set low and make sure that you aren't overdriving the input into the receiver. If you see distortion jump up with the receiver turned well down that would be either input clipping or sc output clipping. Set the levels out from the sc just below that point then leave them alone. Then turn the receiver up on the master while monitoring the distortion in the RTA you may even have to boost the channel trim as well. You may have enough voltage to clip the sc input even with the sc input sensitivity set to minimum. If so just stop there as you won' t be certain what happens past that point. Once you get the receiver gain set to where it is just below clipping plug the output back into the amplifier instead and run the signal and monitor the clip light on the amp while adjusting the input trim on the amp. If the clip lights are lighting up you have more than enough gain and this confirms it. Find the spot on the amp trim where the clip lights just start to stay on solid. This ensures that your receiver will not clip until your amp is already clipping hard and allows the least amount of gain needed at the amp which can help combat hum and noise. Avoid messing with the amplifier trim after this. At this point you can unplug the amp again and take a cheap hacked up RCA cord and connect a dmm to it and measure the voltage if you are curious. You can also do this for the main channels which will max out at somewhat less voltage usually. You only need do one of those the rest should be similar.

All speakers should be disconnected or off during this. All EQ should be disabled dynamic, Audyssey, external, etc...

If you have other devices between the receiver and amp such as a minidsp or a Dcx. You move onto these after the receiver one at a time until you get to the amp. You should maintain the strongest clean signal you can up to the amplifier. The amplifier should clip first before anything else. Again avoid adjusting any input or output trims after this is done except for the receiver settings.

When EQ is enabled things get more complicated. If it is in the first unit in line the receiver you need not mess with anything. If it is after the receiver you may need to adjust the input and or output trims for the device doing the EQ. Boosting is not what you have to worry about so much it is cutting which will allow the input to clip on the device EQing prior to the output producing enough voltage to clip the amp. So if you have a deep cut it is then possible to clip the EQ devices input prior to getting full power from the amp. At this point after EQ in an outboard device you can run its output into the sc and Measure the EQd response shape of the outboard EQ device only! to determine how much cut is there and increase the EQ devices output by a corresponding amount. This last part is not necessary if you have more than enough headroom that you will be very unlikely to need it. It is only needed if you want to be able to get EVERY scrap of output the system is capable of at any frequency.

Thank you very much!

"They do not match at all."

winisd is a 2pi space model...as if you were measuring a sub in an open field.

rooms have modes, boundary gain, and pressure vessel gain depending on the dimensions and the construction of the room.

the thiele small parameters that underlie winisd are not meant to predict room effects, just roughly the effect of a driver in an enclosure.
Edited by LTD02 - 12/5/12 at 2:40am

my guess is that your audyssey thing is the problem.

Can you show the raw response with no EQ and no smoothing together with the after EQ response? If I had to guess there is a lot of boost being supplied somewhere and it is requiring a lot of power from the amp.