My New Fi Q18 Sub Project -Input Wanted Please

**Martianpc** · **07-23-09, 12:13 PM**

I just moved into a new place and set up my HT room, I am not satisfied with the output I am getting from my current sub which is a Klipsch RW-12d. I want to build a new sub most likely using the Sound Splinter RL-P18

I do not have an amp or drivers currently so I need advice on what to buy for the amp. I considered using an ep2500 for the sub but I have no idea what sort of active crossover I would need. I think I may be able to use the sub out built in crossover in my Onkyo 805. (can be set between 80 and 120hz).

My current equipment is an Onkyo sr805 receiver, all Klipsch reference speakers RF82 up front, RF 52 in the rear and an older model KLF-C7 center.

The room is about 13x18 when the blackout curtain is closed and if that is not closed the room is open to the rest of the basement.

I want a loud but deep sound from the sub, should be able to feel them strongly during good actions. The room is mostly all concrete and I still need to try to treat the walls somehow.

Here are some pictures so please give any advice that might help me. Thanks

back of the room curtains partially open to rest of room. They close all the way though and black everything out.

Here is what I am planning so far. I would like to position it in the front of the room under the screen.

72" Wide
23" Tall
23" Deep

Made of 3/4" MDF with corner and cross bracing.

The port would be a slot port along the bottom that would be 21.5" wide on the inside (23" deep - 1.5" for MDF wall themselves) and 5.5" tall while being 59.89" deep. This will give me a tune of right around 16hz. Obviously the EP2500 will have more than enough power for this sub, but it allows me to build a second in the future if so desired.

The internal volume should be around 18 cubic feet after the port and sub.

Here are some rough sketches of my current plan.

If my Winisd is right, I should not have any port noise with around 50 ft/s peak at 14hz, I should be able to reach high spl and not bottom out. I have included the Winisd file as an attachment for anyone who cares to see the plan. This is not a final decision but a strong possibility. I do not know if I need a crossover besides my Onkyo because I would not have a subsonic filter to the best of my knowledge.

Specifically looking for pointers on:

-The Box design
-The Amp
-Built in crossover on RX going to be ok?
-Subsonic filter needed?
-Port issues?
-where to brace that box?

Thanks in advance for any help, I am new to HTS and was suggested by an AVS member that this is the place for DYI projects. Thanks!

**Mike P.** · **07-23-09, 12:51 PM**

First let's deal with the modeling.

The low pass filter should be 4th order at 80 hz. There's no need for the high pass 2nd order at 8 hz since it isn't doing anything. As you have it modeled the cone excursion is exceed at 14 hz with the amount of input power you have entered. Should you find the sub is bottoming out, depending on how hard you push it, you may need a add on High Pass Filter.

The first port resonance is too low. Change the port height to 4" and the air speed is well under 26 m/s and this raises the port resonance to 160 hz.

**Martianpc** · **07-23-09, 02:07 PM**

Hi Mike, thanks for the quick reply. I went ahead and changed the modeling to reflect a 4" x 21.5" port and fixed the filters. I also modeled up a Fi Q 18 that actually looks like it might actually preform very well under the same box without risking bottoming out. Not to mention it is 100 dollars cheaper to buy.

Do you think the crossover in my Onkyo set at 80hz will be sufficient to manage the output to an EP2500 amp?

I have included the model for the Fi sub as well. I appreciate the help and expertise.

**Mike P.** · **07-23-09, 02:26 PM**

The Q18 models close to the RL-p18. They both exceed Xmax at 14 hz when pushed hard.

I don't recall if anyone had insufficient voltage on a Onkyo to drive a EP2500 or not.

The 4" x 21.5" is longer then the 5.5" x 21" port. You'll have to recalculate the volume of the box to see if there is a difference in net volume.

**Martianpc** · **07-23-09, 05:30 PM**

Not to be a pain, but I am confused, I checked my model again and I am showing a port length of 42.43in which is shorter than the previous port of around 5.5" which had a length of about 59.8. You mentioned the port would become longer, however I am seeing it as shorter in length as a result of moving to a 21.5" X 4" opening.

**ironglen** · **07-23-09, 07:47 PM**

I thought my 14.5hz tune would be safe, and maybe I'm a bit fearful as the driver has so much travel to give, but I think a hpf would be a good safeguard, especially with movies like LOTR, Titan AE My Mal-X moved alot the other day, and it wasn't even turned up- scared me a bit as it would be an ordeal to lose the driver.

**Mike P.** · **07-23-09, 09:42 PM**

Quote:

Martianpc wrote:

Not to be a pain, but I am confused, I checked my model again and I am showing a port length of 42.43in which is shorter than the previous port of around 5.5" which had a length of about 59.8. You mentioned the port would become longer, however I am seeing it as shorter in length as a result of moving to a 21.5" X 4" opening.

Sorry about that, I meant to say shorter. My bad.

**Mike P.** · **07-23-09, 09:47 PM**

Quote:

ironglen wrote:

I thought my 14.5hz tune would be safe, and maybe I'm a bit fearful as the driver has so much travel to give, but I think a hpf would be a good safeguard, especially with movies like LOTR, Titan AE My Mal-X moved alot the other day, and it wasn't even turned up- scared me a bit as it would be an ordeal to lose the driver.

I agree on having a safeguard in place. It's well worth the $100 price tag for a add on High Pass Filter to ensure the safety on the sub. There's a big difference between relaxing and enjoying a movie as opposed to worrying if the next hit is going to damage the sub.

**Martianpc** · **07-23-09, 11:41 PM**

Do you have a recommendation for a certain HPF? I am trying to stay inexpensive on this project. Although I am starting to wonder if I will need anything to help manage the high output levels expected from this beast.

**Mike P.** · **07-23-09, 11:55 PM**

I suggest you build the sub and try it out first. Depending on your listening habits maybe you don't need a HPF. No sense spending more money then you have to.

**Martianpc** · **08-02-09, 12:37 AM**

Though I would post an update. I ordered an EP2500 and a Fi Q18 D2 which are now in the mail. I also started getting my wood together to make the box. The final design is 72 inches long and 23 tall by 23 deep with a slot port. I have not ordered a HPF because I am going to see how it does at first without as Mike suggested. If things are moving too much then I will look into a HPF option. I am not doing anything fancy with my woodworking as I do not have the tools. Just 90 degree corners with Titebond II wood glue and my brad nailer to make it.

On the inside I am going to caulk all the seams to make it really airtight and sand down all my edges on the bracing as well as the port corners to make them all smooth. I am still not sure of what I may do to actually cover the box. I have considered rubberized undercoating spray paint to give it a smooth finish that looks nice, truck bed liner to give it a durable look more in line with pro audio gear, carpet, paint, or veneer (which I have no idea what to use or how to use).

I will update this thread as the build moves along with pictures. -Mike

--Safe to move to the Fi section now as it is 100% for sure a Fi build

**Martianpc** · **08-03-09, 10:52 PM**

More pics of the build progress. I need to do more bracing, but I am not sure what to do exactly. I did a bit more since this picture but not a ton before putting the top on. It feels pretty solid and when smacked with a closed fist it gives a pretty good solid thud. I think I am going to test it out when the Q gets here before going nuts on the bracing. I did make 1 decent sized mistake and didnt even realize it until it was too late. I ended up making my port only 3.25 inches instead of 4. This is because I didnt take my wood into consideration properly for the port wall. It lowers my tune down to about 14.6hz but I am still under 26ms of air velocity though so I should be ok. I rounded all the corners in the port so I hope that helps. Anyway here are some pics

**Martianpc** · **08-04-09, 12:49 PM**

Ok the box is done, installed, sounds TERRIBLE. Not a box resonating bad, just very directional sound. Some areas get loud, some are quite, some you feel it, some you dont. It bottomed out during the hulk and it really didnt seem that loud. my system as a whole is drawing upwards of 16 amps at times until the breaker trips in the power conditioner. For whatever reason it doesnt seem to get moving until the volume is really high and even still it doesnt seem that much louder than my old 12 inch Klipsch sub. I know I am doing something very wrong, but I have no idea what. I have my EP2500 connected to my onkyo receiver with a phono to 1/4 inch cord going into input 1 on the amp and the sub bridged. PLEASE help me figure this out. I am feeling really depressed about the project right now.

**Mike P.** · **08-04-09, 07:29 PM**

First lets deal with the box. The longest inside length is about 68 inches. This is the half length of a 100 hz frequency. You should add a foot or so of damping to each end of the sub to eliminate an resonance issues.

You should verify that the sub is correctly wired and that you do not have the 30 hz HPF engaged on the EP2500.

When you tested the sub did any of the panels vibrate? If so you need to add more bracing.

Try moving the sub to different locations in the room and see if the sound improves.

**Martianpc** · **08-04-09, 08:56 PM**

Quote:

Mike P. wrote:

First lets deal with the box. The longest inside length is about 68 inches. This is the half length of a 100 hz frequency. You should add a foot or so of damping to each end of the sub to eliminate an resonance issues.

You should verify that the sub is correctly wired and that you do not have the 30 hz HPF engaged on the EP2500.

When you tested the sub did any of the panels vibrate? If so you need to add more bracing.

Try moving the sub to different locations in the room and see if the sound improves.

1.) do you recommend any particular type of damping?

2.) I will say how I wired the sub, although I think I did it right, could have made a mistake. I wired it in series since it is a d2 sub. I connected the positive to the first voice coil positive, and the negative to the second coils negative then I have a wire going from the postive and negative that are unused on each coil. All my wire is 10 gauge. As far as I can tell the 30hz filter is not on.

3.) None of the panals vibrate, while I do not have a ton of bracing, I tried very hard to place it in effective areas.

4.) I am going to try to move it around, but placement is limited due to the ridiculous size of the thing. When my Klipsch was up front it made similar levels of bass or more and it also was a front facing, front firing sub. Not like that means all that much though I suppose.

Here are pictures of the box, the amp switches, and the amp wiring. Thanks soooo much for the help.

--I watched a few scenes that should have incredible bass like the depth charge scene in u571 and it really wasnt there. with the amp maxed out on the gain the mains were overpowering the bass by a good bit. In all of my testing the amp never even got warm except when I ran some sine waves. I am wondering if my output voltage is too low on the Onkyo receiver maybe being part of the problem.

Click here for large image of switches

Thanks so much for the help. -Mike

**Mike P.** · **08-04-09, 09:24 PM**

I see what you mean by limited positioning possibilities.

For damping I've heard that using closed-cell foam, and then a couple of thick layers of felt works well.

Your amp switches are correct.

As for the low voltage issue, that would have been my next guess.

**Martianpc** · **08-04-09, 09:38 PM**

Is there a way to test my output voltage with my multimeter? If low voltage is an issue, what would you recommend to bring it up. Ideally with a subsonic filter in it also. Since I have already bottomed this sub out, which btw, was terrifying and much louder than any bass I have made yet.

One idea I had is to raise my tune a bit maybe to 17 or 18. I dont know that I could do that easily since it is all nailed and glued together, but I could plug the slot port and put in a 12 inch round by 43 inch long round port to bring my tune up to 18 and run it out the side maybe just routing a hole in the end and bracing the port on the inside.

**Fi Audio** · **08-04-09, 10:24 PM**

Hmmm.... something very odd going on. I remember initially looking at your box and thought it correct. Ill go back over it to make sure again, but something is definitely amiss somewhere.
Do me a favor and pop test the coils with a battery... + to + and - to - and it should move out... reverse and it should move in.
As for voltage out of the Onkyo... you can test with a multimeter that has AC peak hold, or if you have a constant tone disc you will get a stable reading.
Dips 4/5 are for input settings I think... not sure if they need to be the other way for a single line in for bridged mode. Need to google a manual for that one.

We will get this one solved ASAP and have you pounding.

Thanks,
Scott

**Martianpc** · **08-04-09, 10:52 PM**

Thanks Scott, what type of battery? 9v? Also, I did make a mistake when building my box and made my port 3.25" instead of 4" This lowers my tuning to about 14.5 which is low, but for scenes like the U571 depth charges I would have thought that would actually help. I have a few cd's with sine tones on them, for measuring the voltage, just touch the positive and negative of my signal wire while playing any sub 80 hz tone? or is a certain tone is best? I appreciate the help. Thanks, -Mike

**Fi Audio** · **08-05-09, 01:03 AM**

9V is fine. Itll let you see the movement easier than a AA would

Yes, you can play about any tone under the low pass filters range (assuming the Onkyo has a LPF setting). 14.5 is low still... but you wouldnt be loosing massive output above tuning by doing so. Not as pronounced as you have described by any means.
Try 60Hz and then 30 Hz, and 20Hz... then 14Hz if it has it just to see if the Onkyo is rolling things off hard on the bottom end for some reason. Im figuring most decent meters should read AC at 14 Hz fine. I know all of the units I have (including the cheapos) will remain linear there.

**Ricci** · **08-05-09, 03:44 PM**

Further questions...

Have you ever seen the clip lights flash on the EP2500?
How much excursion is the sub getting on some of these scenes? Just guess it doesn't have to be precise.
What is your crossover frequency to the sub set at?
Do you run REW?
What is your SW level inside the Onkyo set at?
Have you level matched all of the speakers to each other with an SPL meter?
Do you have an SPL meter?

My gut tells me it's the standard old EP2500 not getting enough juice to do it's thing, or it's a bad room acoustics sub placement situation. Could even be both.

**Martianpc** · **08-05-09, 03:44 PM**

Quote:

Fi Audio wrote:

9V is fine. Itll let you see the movement easier than a AA would

Yes, you can play about any tone under the low pass filters range (assuming the Onkyo has a LPF setting). 14.5 is low still... but you wouldnt be loosing massive output above tuning by doing so. Not as pronounced as you have described by any means.
Try 60Hz and then 30 Hz, and 20Hz... then 14Hz if it has it just to see if the Onkyo is rolling things off hard on the bottom end for some reason. Im figuring most decent meters should read AC at 14 Hz fine. I know all of the units I have (including the cheapos) will remain linear there.

Hey Scott, here are my results:

The 9v battery did make the sub push out when + was to + and pull in when - was to -. It didnt go all the way to xmax I dont think, although the battery may be older (out of smoke alarm

). I also tested the sine waves and recorded their voltages. I initially did the testing with my laptop using the sine generator in winisd. Then I had a disc that had a 30 hz tone so I used my disc in the dvd player and got stronger voltages. I only have 30hz on disc to test though. Here are my results. Thanks again for any input, I did notice that at -20 db on the receiver I tend to have very low output, but then at 0 (reference) on the receiver my voltage was pretty high. (look at the 30hz disc tone for best example)

Tones:
60hz
-20 volume
---.5v up to 1.5 near 0vol

30hz
-20 volume
---.2 at 20 4.7v at 0 vol

--.5v at 20 8.3 at 0 --- on disc through dvd player.

20hz
-20 volume
---.2v at 20 4.3 at 0 vol

14hz
-20 Volume
---.2 at 20 3.7 at 0 vol

**Martianpc** · **08-05-09, 03:56 PM**

I feel like I should make an update, I just ran my tone disc through ( I do not know which tracks are what tones) and I am somewhere between 10hz and 18hz right now, and the sub does move a ton actually it seems. I do not feel much in the room I am in, however, I found out that the rest of the house can feel it. The lights hanging over the pool table were moving a bit.... so I dont think its my voltage that is the problem. I am disapointed at very low hz I can hear a good bit of port noise unfortunatly, however it seems to go away at the higher tones. I need to find out how to actually hear it in my room, which for whatever reason is very tough to do.

**Martianpc** · **08-05-09, 03:57 PM**

Also since I did bottom out once already I am afraid to again. I know a subsonic filter will help with the sub 14hz tones, but according to winisd I will bottom out from 20-24 as well with enough volume. How can I avoid that one?

**Martianpc** · **08-05-09, 04:06 PM**

Quote:

Ricci wrote:

Further questions...

Have you ever seen the clip lights flash on the EP2500?

--No

How much excursion is the sub getting on some of these scenes? Just guess it doesn't have to be precise.

with the volume very high, I maxed it out once

What is your crossover frequency to the sub set at?

80hz

Do you run REW?

Do not have a good mic

What is your SW level inside the Onkyo set at?

0 (not + or -)

Have you level matched all of the speakers to each other with an SPL meter?
Do you have an SPL meter?

Do not have a meter

My gut tells me it's the standard old EP2500 not getting enough juice to do it's thing, or it's a bad room acoustics sub placement situation. Could even be both.

Thanks--Mike

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