Q about driver break-in and final setup

[queequeg99]

I am completely new to speaker building so please forgive me in advance for what are surely very basic questions about (i) breaking in a driver for a Tuba 18 I’m building, and (ii) set up once my sub is constructed.

I’m using two of the recommended MCM 8 inch drivers and a BASH 300 plate amp from Parts Express. My AVR is a Denon 2112ci (with Audyssey Multi EQ XT). I have burned a 30hz tone onto a CD. The sub will going into a basic 3.1 home theater system in our living room (using Hsu Research HB-1 MK2 bookshelf speakers as the LCR fronts).

1. Break in: Do I just connect a CD player directly to line level inputs on the amp, and slowly turn up the volume on the amp until I reach 10V (clipping the multimeter leads to the ends of the red/black wires coming out of the amp)? Or is the AVR involved in this process (in which case, how should I adjust the volume on the amp vs. the AVR to get to the necessary voltage?)? I just don't want to do something really stupid that results on the speaker exploding and me teaching our little girls yet a few new colorful expressions.

2. Setup: Once I have completed the cabinet and installed the drivers, is anything else required before I integrate the sub and amp into my system as I would any sub I might buy from a store? I’ve read about voltage limiters (which I gather my amp doesn’t have built in) and don’t know if that’s a concern in my situation.

Sorry for asking such basic questions. As I type this out, I feel so completely brain dead (like a fish asking birds how to fly). I’ve read a ton of stuff on these forums but I am so out of my element on these issues (and don’t want to screw up my project) that I thought a super explicit Q&A would be best.

Oh, and a few unrelated observations about the T18 build:

1. I’ve seen a number of posts asking about using ¾” stock. For those who tend to overbuild, just follow Bill’s advice and don’t even think about it. I’m the king of overkill in my neighborhood and am amazed at how rock solid the cabinet is so far using the recommended ½ stock (I installed panel 4 last night). I cannot imagine how solid it will be once it is complete. If you find yourself needing a little more of a work out, just laminate your finished cabinet in ¾ MDF.

2. I used the 6-prong t-nuts from Parts Express with Gorilla Glue epoxy. I pulled them through using a hex bolt and had to seriously crank down on the hex wrench to get the nuts to fully embed themselves in the baltic birch. I bought some tiny little security screws per some other posts but doubt I will use them. Those t-nuts aren’t about to go anywhere. I imagine I might not be quite so confident with a softer plywood. However, that baltic birch is seriously tough stuff.

3. Subject to my questions above, these subs are easily doable by any novice. I came into this project owning a circular saw and 6 clamps (I borrowed my father’s jig saw to cut the access panel and baffle holes). If you read everything a few times before starting, measure everything a few times before cutting, and test place everything dry for fit before gluing, you really shouldn’t screw things up.

[88h88]

1: for break in you can certainly use a CD player assuming your amp has the inputs for it, just hit the repeat button on the player so you can leave it for 12 hours or so. Before you attach the drivers use the multimeter on the speaker cables to make sure you're getting 10V. Once that's determined, turn off the amp, hook up the drivers and you're away. Do the instructions for the T18 state a 30hz tone? I've built a few of the PA cabs and they've said 20hz @ 10V, so I'm just wondering.

2: you won't need a voltage limiter on the sub I assume the wife/neighbours/kids/dog will be complaining long before you start hurting the drivers. If you have the amp for the sub you just hook up your sub output from your AVR and if you've got Audyssey or something on it use that to EQ it. Someone will be able to help more with that aspect as my table tuba is tuned by ear rather than automatically done.

Glad everything's gone well so far!

[queequeg99]

1: for break in you can certainly use a CD player assuming your amp has the inputs for it, just hit the repeat button on the player so you can leave it for 12 hours or so. Before you attach the drivers use the multimeter on the speaker cables to make sure you're getting 10V. Once that's determined, turn off the amp, hook up the drivers and you're away. Do the instructions for the T18 state a 30hz tone? I've built a few of the PA cabs and they've said 20hz @ 10V, so I'm just wondering.

Thanks for the quick response. Yes, I had read about the pre-break in test to ensure that you're getting correct voltage. Seems wise.

As for the tone, I'll have to check the plans and exactly what I downloaded when I get home (I made my post from work so I was going off memory).

Thanks again.

[Grant Bunter]

88 is on the money.

Especially the part he wrote about volume.
After building, break in and testing in general, if you find that you're more often inclined to try and turn bass volume up (the T18 won't match a Table Tuba or the like in terms of output), you should consider building another.

Also, take some time in positioning. Having a fixed idea about where the sub should go due to aesthetics and/or the wife may limit low frequency response.
One great way to find the best position for the sub in the room is to have it running at what would normally be your listening position. Crawl around the floor of the entire room, until you find what seems to be the best low frequency response. That's where your sub should be placed

[queequeg99]

88 is on the money.

Especially the part he wrote about volume.
After building, break in and testing in general, if you find that you're more often inclined to try and turn bass volume up (the T18 won't match a Table Tuba or the like in terms of output), you should consider building another.

Also, take some time in positioning. Having a fixed idea about where the sub should go due to aesthetics and/or the wife may limit low frequency response.
One great way to find the best position for the sub in the room is to have it running at what would normally be your listening position. Crawl around the floor of the entire room, until you find what seems to be the best low frequency response. That's where your sub should be placed

A second one is in the plans. The first will go into a corner on the left side of an entertainment console. The second will go on the other side of the console. Not ideal placement but WAF is a big factor in this room. There is a possibility that I could get permission to place a THT LP in the room. But I will have to start another thread with pictures to demonstrate some room placement issues. Also, given the use of this system, I think a THT LP might be a bit much (wait, did I just say that out loud?).

As for subcrawling, WAF-restrictions still apply, although I do have some limited flexibility. One reason I'm really liking the BFM designs is that they make subcrawling so much easier. When I got my Hsu VTF-15H for our dedicated home theater room, I really had no idea how I was going to get it up onto our sofa for subcrawling purposes (i.e. as close to listening position as possible). That damn thing weighs well over 125lbs.