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-   -   MTH30 Questions : Complete Noob! (http://www.diyaudio.com/forums/subwoofers/228434-mth30-questions-complete-noob.html)

ghettosynth 22nd January 2013 10:46 PM

MTH30 Questions : Complete Noob!
 
Hi All,

I'm not at all new to electronics DIY and I have some experience with very basic woodworking and access to appropriate tools. That said, the last time I tried to build a speaker cabinet it was in the 9th grade with mitered joints and cleats and, well, let's just say that I didn't get very far.

Ok, that out of the way, being all grown up (outside) and motivated, I've decided that the MTH30 seems like it will be a good companion to my alto TS110s and I want to shake this fear of cabinet building as I have some other projects where ultra-budget is essential.

So, if you guys don't mind, I have some really basic noob questions.

1) I see that the MTH30 calls for MDF. I would rather use plywood for weight, is this a good idea? If so, does it require changing the plan in any substantial way? Any experiences with plywood vs mdf would be helpful here. I don't care about the additional cost if it makes the cabinet lighter.

2) Are the cabinets glued and screwed, or just glued, I can't tell from photos online. They appear to be just glued.

3) From the pictures that I've seen, I'm not seeing anyone line the cabinets with the acoustic dampening material that was found in virtually every speaker made when I was a kid. Do you not need/want this in these type of cabinets? Don't laugh, I really don't know the answer.

4) I'm in the U.S. so getting one of the called for drivers is a bit expensive. I've seen that people have used at least two different alternative drivers that are available from parts express. The RCF LF12g301 and the Goldwood GW-12090. The RCF is $199 and the Goldwood is $99. I also have a couple of JBL tops with 2206s in them that I could borrow temporarily to try out and compare. The question is, what differences should I expect between these drivers? I'm really new to this so I don't yet have any intuition on translating driver specs to real world differences. So, if possible, please be specific and discuss in terms of real world performance differences. I'm not adverse to buying the right driver, but I don't want to waste money on differences that I can't use. I care a lot about sound quality, I care a little less about maximum output.

If it helps this (or these if I build two) are only going to be used for DJ applications, both indoors and out, for small gigs. I largely play somewhat downtempo as well as classic house music, if this helps understand my application. Also, you can assume that they will be powered with an appropriate amp for the driver, so that isn't a factor in which one that I choose.

Thanks in advance,
gs

weltersys 23rd January 2013 12:18 AM

1) Use plywood.
2)Use screws unless you like reassembling.
3) Acoustic dampening reduces output in a TH or BR cabinet. For full range cabinets it is used to keep upper frequencies from ringing through the port, for sealed cabinets it can increase apparent volume.
4) The Goldwood only has an Xmax of 5.4 mm, there are 12" with over 20mm Xmax available.
A speaker with double the Xmax can move more air, 6 dB more output.
5) The MTH30 does not look like a particularly good TH design.

Smaller designs don't go as low, but ones worth looking at for DJ use are the THAM, SS15, XOc1's TH18, my Keystone design, the Othhorn, and the Gjallerhorn at the very large end.

ghettosynth 23rd January 2013 01:34 AM

Hi,

Thanks for the response, you cleared up quite a bit. You make two claims about the MTH-30, 1) that it's not a good TH design, and 2) that it's not suitable for DJ use.

Let me first address the second point. I have JBL 18 inch subs for when I need big subs, although, I'm planning to replace those at some point. I'm fully aware that I'm giving up low end extension but even a 12" sub will add some nice bottom end to my little altos. I'm not looking for this to be my only sub, but I do want it to be small. Of the alternatives that you suggested, if I found the right information, only the SS15 and your THAM series is 15 or smaller. The rest are 18" subs, correct? I couldn't find plans for the XOc1 or the SS15, but in the photo of the builds, it looks a bit larger. So, I'm not at all interested in building an 18" box right now. I want to make mistakes with smaller pieces of wood!

I couldn't find a lot of detail about the MTH-30, and, discovering your THAM series, your own THAM-12 and THAM-10 are actually quite appealing. I will be using it with my TS110as which go down to about 70hz. Alto claims max SPL of 120 dB continuous. Given that the THAM-15 is about 1/3 more volume than the MTH30 and that the driver is 1/3 more weight and cost, I'm still leaning towards a smaller sub. Also, the 10" driver is almost as much as the 12" driver and takes significantly less power. So, I'm still feeling that the 12" is still the right size for me.

So, given that I'm fully aware that this is a compromise, and that I'm looking for something in a smaller cabinet, could you perhaps elaborate a bit on (1) above? Is your THAM-12 design a better design, and if so, why? I do like that 1) it's a bit smaller than the MTH-30, and 2) that, to my naive eyes, the B&C driver appears to be a bit beefier than the RCF (but also less sensitive) for about the same price.

Inductor 23rd January 2013 01:54 AM

weltersys, (+1)
ghettosynth, You probably wouldn't be able to achieve lower/sub bass frequencies region with that nice driver of yours RCF LF 12G301.
I would do like you, finding a nice driver and stick to it, but one that works in a horn and goes low, that one is good for a horn and doesn't go low in my list.
Get opinion from a professional or then listen or measure the drivers yourself.
I definitely go add a pair to your PA active speakers, like the Alto TS110, and choose something in the trends of the EMINENCE Omega Pro-15a or the EMINENCE KILOMAX PRO 15 A. But hey this me. I have horns and they don't go low (maybe 40Hz) but they can be really noise if you push the limits. Your driver looks excellent for a horn but it doesn't go low in my books... That's your choice.
Bill Fitzmaurice Design DIY Kits | Speaker Hardware

PASC 23rd January 2013 02:36 AM

Hi!
Already made Made 6 of them .
-Plywood, plenty of good glue, and screws is a must; I use plenty of T-50 pin nails.
BeA Deutschland - Befestigungstechnik
-no dampening;
-best drivers from tested ones are:
12PS100
12ps100 - Parts Express Ships Fast and Ships Free
12CL76
B&C 12CL76 12" Neodymium Woofer 294-695
With these drivers you could take a four string bass guitar and play the notes thru it as it should.
Correct band sets helps to maintain drivers health; Low cut around 40Hz at minimum; high cut at 96Hz was the best performance in my opinion.
Let your ears also help in judgement.
Regards,

ghettosynth 23rd January 2013 01:34 PM

Quote:

Originally Posted by PASC (Post 3338311)
Hi!
Already made Made 6 of them .
-Plywood, plenty of good glue, and screws is a must; I use plenty of T-50 pin nails.
BeA Deutschland - Befestigungstechnik
-no dampening;
-best drivers from tested ones are:
12PS100
12ps100 - Parts Express Ships Fast and Ships Free
12CL76
B&C 12CL76 12" Neodymium Woofer 294-695

Thanks, to be clear, did you mean 6 of the MTH30? I read in another thread that the 12ps100 didn't simulate well in that cabinet so I want to make sure that you aren't talking about the THAM12?

Quote:

With these drivers you could take a four string bass guitar and play the notes thru it as it should.
Correct band sets helps to maintain drivers health; Low cut around 40Hz at minimum; high cut at 96Hz was the best performance in my opinion.
Let your ears also help in judgement.
Regards,
Nice. From what I've read, the TH designs are quite musical.

ghettosynth 23rd January 2013 02:31 PM

Quote:

Originally Posted by Inductor (Post 3338290)
weltersys, (+1)
ghettosynth, You probably wouldn't be able to achieve lower/sub bass frequencies region with that nice driver of yours RCF LF 12G301.
I would do like you, finding a nice driver and stick to it, but one that works in a horn and goes low, that one is good for a horn and doesn't go low in my list.

Sure, I appreciate the input. The simulations paint a pretty strong picture for the 12" subs. None of them will go that low, that's ok. I get that. I admit, the THAM15 looks appealing from many angles, but, for this first build I want to keep the size manageable. I may change my mind between now and when the build starts, but for the time being, I feel that a small 12" sub suits my needs.

Quote:

I have horns and they don't go low (maybe 40Hz) but they can be really noise if you push the limits. Your driver looks excellent for a horn but it doesn't go low in my books... That's your choice.
What do you mean by "really noisy?"

tnx,
gs

turbodawg 23rd January 2013 03:02 PM

Quote:

Originally Posted by ghettosynth (Post 3338095)
Ok, that out of the way, being all grown up (outside) and motivated, I've decided that the MTH30 seems like it will be a good companion to my alto TS110s and I want to shake this fear of cabinet building as I have some other projects where ultra-budget is essential.

Hi, I have a portable PA build in progress, with a pair of Peavey Impulse 100's, very similar size and output to your alto's. I looked at every compact tapped horn, horn, bandpass horn, ported horn, t-tqwt, and bandpass design out there over a period of several months, tried modeling my own, and eventually decided on a pair of 15" subs in a compact slot ported box with 35hz tuning:

http://www.diyaudio.com/forums/subwo...on-ref-ho.html

In a 20x22x16" 50lb build, having low extension (usable in room to 30 hz w/o eq) and no need for digital time delay to time align the mains was a big bonus, while still getting nearly the sensitivity (95 db/w/m/2pi) and max output of a compareably sized horn. I am extremely happy with their performance so far - very clean, powerful and musical.

weltersys 23rd January 2013 03:39 PM

Quote:

Originally Posted by ghettosynth (Post 3338268)
Thanks for the response, you cleared up quite a bit. You make two claims about the MTH-30, 1) that it's not a good TH design, and 2) that it's not suitable for DJ use.

I'm not looking for this to be my only sub, but I do want it to be small. Of the alternatives that you suggested, if I found the right information, only the SS15 and your THAM series is 15 or smaller. I want to make mistakes with smaller pieces of wood!

I couldn't find a lot of detail about the MTH-30, and, discovering your THAM series, your own THAM-12 and THAM-10 are actually quite appealing.

So, given that I'm fully aware that this is a compromise, and that I'm looking for something in a smaller cabinet, could you perhaps elaborate a bit on (1) above? Is your THAM-12 design a better design, and if so, why? I do like that 1) it's a bit smaller than the MTH-30, and 2) that, to my naive eyes, the B&C driver appears to be a bit beefier than the RCF (but also less sensitive) for about the same price.

I made no claim that the MTH-30 is not suitable for DJ use.
Many DJ's use total garbage, the MTH-30 would be a distinct step up.
My statement that the MTH30 does not look like a particularly good TH design is based on comparing it to others that appear better in terms of output vs. size and frequency response.

The Tham is Anders Martinsson's design, not mine.
The B&C drivers are well suited for TH use, you will find that though they appear to be less sensitive, they don't fold up like a cheap suit at high drive levels as lighter, more sensitive cones (Eminence 3015LF, etc.) do:

http://www.diyaudio.com/forums/subwo...pped-horn.html

The SS15 is Jbel's design:
http://www.diyaudio.com/forums/subwo...challenge.html

Since my Keystone, the Xoc1 TH18, the Othhorn, and the Gjallerhorn are all larger than you want, I won't bother linking them.

This design is smaller than the Tham 15 or SS15, has more LF output, but less output above around 50 Hz Hz:

FREE SUB PLAN: Dual Lab12 (Front Loaded) by Welter Systems

It is about the size of a JBL SRX 718, but has more LF output, it goes deeper than a SRX 728.
Using a pair of TC EPIC 12" instead of the Lab 12s, it would be very close to the same output as the 728 in less than half the size.

I have a pair of the WS 2x12" cabinets for sale unloaded if you are interested.

Art

weltersys 23rd January 2013 03:54 PM

Quote:

Originally Posted by turbodawg (Post 3338871)

In a 20x22x16" 50lb build, having low extension (usable in room to 30 hz w/o eq) and no need for digital time delay to time align the mains was a big bonus, while still getting nearly the sensitivity (95 db/w/m/2pi) and max output of a compareably sized horn.

Turbodawg,

You are using the Dayton Reference 15 four ohm driver in a very small low tuned ported box.

It is only 87 dB one watt one meter at 100 Hz, and drops considerably in sensitivity from there, probably in the 80 dB one watt one meter range at Fb.

Have you any measurements?

Art


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