How much better can i make this TH

[bko69]

I'm totally new to THs. i have done a lot of reading here and on other forums and finally decided to make one so i could hear what they sound like. i took Patrick Bateman's double driver idea and crossed it with FlipC's mini clone design. i did not do any modeling and sort of made it up as i went along. here is what i came up with. i'm using the MCM 55-2421.




here are the cut measurements of my wood:

20.75" x 9.5"
16.5" x 9.5"
14" x 9.5"
12.5" x 9.5" - 15 degree angle on one end
10" x 9.5"
24" x 9.5"
24" x 9.5"
23" x 9.5"
24" x 24"
24" x 24"

it sounds pretty good but could it sound better? or am i way off here? i think the throat is 12.5"

i'm using a QSC PLX 2404 to drive it. how hard can i drive these? i'm using the sub out of a Behringer FBQ1502 set at 75hz. is this right or can i set it at 100hz?

my plan is to make 4 of these for use in a PA system.

Thanks,

bob

[jbell]

is your response pretty flat? or do you have notes that stick out really loud?

From my guesstimates on your TH from pictures, if you would have started at 1" of space at the start of the horn, instead of 0", and then follow the flare around, you should have a nice even response. Horn resp says you should get 120db at 40v, drivers in series. 40v is as far as I would push them.

[FlipC]

Im curious about phase response.
Since the drivers are offset and 1 isn't inverted.

Also be a bit more descriptive in "how it sounds".
Suggest simple tone test. Hook up a laptop and use it to generate specific frequencies. Start at 20 Hz and go up by 5 Hz each time. Make notes about perceived loudness. If you have ability to measure SPL well then this is mute. Do that.
Either way. It will allow you to know
if there any real problems with the design. Also will let you know how to EQ out those problems if they exist.

And what wood is that?

Good build.

[davygrvy]

The S1 dimension (area at the start of the flare) has a great affect on the flatness. You could try stuffing foam or wood blocks down there to see what changes it might do by pulling off the near driver.

[bko69]

Thank you for all the replies and suggestions so far. i will answer some of the questions:

yes drivers are wired in series.

i'm using 1/2" mdf for most of the box. the brown wood on the inside is 3/4" mdf. this is just a test box i made with scraps i had. the real box will be made with baltic birch.

as for the flatness and sound. i'm totally new to this so i'm not sure what i'm listening for. i have ordered an spl meter and downloaded tone generating software. i will run the test as suggested and try stuffing foam in the end and running the test again. is there a certain distance the spl meter needs to be and volume setting?


thanks again,

bob

[davygrvy]

The "usual" way for testing subs, especially for PA use, is outside with no boundaries for at least 50 feet (1/2 space). Microphone is place at ground level for what's called near coincidence at a distance of 10 meters and power is run at 100W (28.3Vrms@8ohms). The chart you get scales perfectly to 1W/1M. Big office building parking lots are good for this on weekends when no one is there. You can always go smaller by doing it in your driveway, closer, and less power for checking flatness.

[bko69]

here are the results of my spl test. it has been raining here pretty hard so i could not go out side to do measurements. this was done in my garage at 1 meter 2.83 volts.

30hz 28
35hz 30
40hz 56
45hz 68
50hz 76
55hz 80
60hz 76
65hz 81
70hz 81
75hz 83
80hz 84
85hz 86
90hz 86

looks like it does not do so good in the lower end.

bob

[Patrick Bateman]

Originally Posted by bko69

here are the results of my spl test. it has been raining here pretty hard so i could not go out side to do measurements. this was done in my garage at 1 meter 2.83 volts.

30hz 28
35hz 30
40hz 56
45hz 68
50hz 76
55hz 80
60hz 76
65hz 81
70hz 81
75hz 83
80hz 84
85hz 86
90hz 86

looks like it does not do so good in the lower end.

bob

It's +/- 5db from 50 to 90hz... That's about what I'd expect from the MCM. It has a very low QTS. That's one of the reasons I like it so much, it's very horn friendly. Woofers with a high QTS end up needing huge enclosures if you horn load them.

If you want to get some more bass out of it, go to Radio Shack and buy about six 10ohm resistors. They're $1.99 each in a pack of two. Wire all six in parallel. Then re-measure the response. It should play lower. If it's too peaky, remove a resistor. Re-measure again. If it's still too peaky, repeat.

If you're in SoCal, SpeakerCity in Burbank stocks some monster resistor values. I think Apex Jr sells them too.

[Patrick Bateman]

Originally Posted by bko69

I'm totally new to THs. i have done a lot of reading here and on other forums and finally decided to make one so i could hear what they sound like. i took Patrick Bateman's double driver idea and crossed it with FlipC's mini clone design.

Uh oh, are you talking about "the smallest tapped horn" thread?

I wound up building that, but with three woofers, and a different layout. Here's the info:

Small Tapped Horn For a Car - DIY Mobile Audio

[walters]

bko69, you could make your th a little wider. maybe 14in. instead of 9.5in. or even 16in. that will help it go lower