First DIY Subwoofer, Amp question

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hello and thanks for the reply, wasn't expecting that much :)

reply in no particular order, sorry.
300-810 Dayton HPSA1000-R 1000W Rackmount Subwoofer Amplifier
400$ Is still expensive to me, considering this is my first ever DIY subwoofer, but I won't forget this route. Ty.

(I have no idea about your MTX woofer, but aren't car 'subs' generally hopeless in a house?)
To be honest, I don't know if this one is gonna sound good, and that's why I want to try it :D (I've got it on sales; I wasn't worried too much about the specs and such.)

Yeah, though they tend to be suitable for tapped horns, making them 'killer' for most music/HT apps.
Aren't tapped horns usually big ? (I won't forget the 8.8meter one)I wanted to build / I've build a sealed enclosure because my room is about 9 1/2 by 8 1/2. However, If this design fail for any reason, I might try a sonotube for the basement (music / vidoegame/movie app)or a tapped horn (I'll search the forum about that later-on)

i would describe them as crude
Argh, can't wait to get my amp, i'm worried about how they are going to sound now


Talking about amp, i've got a question. *If* I buy a plate amp, how is going to be the installation ? Do I have to make an hole in my enclosure? Or is this thing screwed/glued/whatever on one side of the box ?

Thanks for helping me, its very appreciated
 
Greets!

You're welcome!

Well, 'big' is relative and the driver's specs dictates how big it will be for a given gain BW, though if your room is in feet, then size is much more critical than if it's in meters. Indeed, if in feet and not opening into another sizable area, then you don't need a sub that goes all that low with a lot of gain. In this type app, sealed typically is the best choice for HT.

Anyway, didn't find any info at all, much less specs on this driver, so don't have a clue how it might perform down low.

The plate amp's electronics are open on the back, so either make a hole in the cab and seal it up good, make a separate cavity for it, or build a separate box for it.

GM
 
My bad, yes my room is 9 1/2 by 8 1/2 feets

Thanks for the info about the amps; i think I'll do a separate cab for it because I'd like to try some other enclosure design too (found some tapped horn design at http://www.cowanaudio.com/ that seems pretty interesting.)

Driver specs: (MTX MZS1204)

Qts: 0,58
Vas: 2,363 Ft3 ; 66,9L
Fs:29,26 Hz
Re: 3,3 Ohm
Xmax: 13,5 mm
Qms: 4,48
Qes: 0,67
SPL: 86,02 dB
Sd: 0,581 ft2 ; 0,054m2
_______________________


While I was reading about some diy subwoofer projects, I saw some insulation carpet on each inner side of the box (img below), and I was wondering If it was needed to produce a clean, good sound ? Is there another topic (I will search the forum after this post, don't worry)/ a web site I could read to learn more about insulation ?

MAW-10_07.jpg
MAW-10_08.jpg

(from: http://www.diyaudioprojects.com/Speakers/MAW-10/index.htm )

Thankx for your patience, I know I'm kind of bombing you with newbies question and I hope it doesn't bother you.

Have a nice day.
 
Hmm Personally I'd get a 500W bash amp from Mach 5 Audio. They're Canadian(so is Bash IIRC).

The subs rated for 300W, it should handle it. Do you have a link to the specific sub?

I would use the 500W amp, it give you more head room. I'd rather send my sub too much RMS power, than a nasty clipped squarewave.

Besides thats what gain is all about...just because its capable of 500W doesn't mean you have to use all 500W. You can set the gain with a multimeter, P=(V^2)/R.

And I personally don't like the generalization that car audio subs don't work well in house. You can find very high quality car audio subs. I think the ones that give them a bad name are the cheap ones meant for sealed boxes with a qts of over 0.6. Try an elemental designs O series driver, I like them and IMO they are very clean sounding subwoofers.

Damn just noticed that driver is a high q one...it won't sound good unless its in a sealed box...I'm not a fan of these drivers at all.

So thats my thoughts on the subject at least.
 
Check out your local music stores, pawn shops, ad papers, and Craigslist, Kijiji etc. for used power amps. $300 to $400 should get you something with 400 to 600 watts/channel into 4 ohms, and allows you to run stereo subs. Just be wary of the fictional-watt amps that are marketed to gullible bedroom DJs and karaoke fans, from brands like Gemsound. Verify any power claims if possible, because people are sometimes very creative when advertising amps. eBay too, if you can find a nearby seller; shipping on a big power amp isn't cheap, and it risks damage because sellers don't package them properly.

Amps with larger cases can be quieter, since they can use bigger (and therefore slower) fans. Amps with two-speed fans can be nearly inaudible when on low. (Peavey PV8.5C and CS800 are a couple I've used). (Although my AB Precedent 900 moans loudly thanks to a single-speed fan with a poorly designed grill).
 
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dangus said:
Check out your local music stores, pawn shops, ad papers, and Craigslist, Kijiji etc. for used power amps. $300 to $400 should get you something with 400 to 600 watts/channel into 4 ohms, and allows you to run stereo subs. Just be wary of the fictional-watt amps that are marketed to gullible bedroom DJs and karaoke fans, from brands like Gemsound. Verify any power claims if possible, because people are sometimes very creative when advertising amps. eBay too, if you can find a nearby seller; shipping on a big power amp isn't cheap, and it risks damage because sellers don't package them properly.

Amps with larger cases can be quieter, since they can use bigger (and therefore slower) fans. Amps with two-speed fans can be nearly inaudible when on low. (Peavey PV8.5C and CS800 are a couple I've used). (Although my AB Precedent 900 moans loudly thanks to a single-speed fan with a poorly designed grill).

fictional watts are a problem ... if you dont have any particular reason to trust the brand try to find a spec that looks something like power@%thd

basically power at 1% thd can probably be considered maximum real power ... any power divorced from distortion numbers is potentially fictional

the weight of the amp can be a good way to tell if the power is real or not, but you have to adjust for the class of the amp (A, B, H, D) and the type of transformer used (regular, toroid, transformerless) ... unless you understand how those factors affect the weight you should not use the weight of the amp as a measure

unless you can put the amp into a closet avoid amplifiers with fans. i have one and i love it, but the fan is a real pain ... even though its a variable speed one

realistically though, the most power without a fan that you can have is Crown K2 ... anything beyond that will require a fan or it will melt :)
 
Greets!

You're welcome!

Various forms of damping is normally used to attenuate any spurious out-of-phase mids/HF output due to standing waves in the box and/or in the vent that can comb filter with the mains output, reducing clarity, perceived attack/decay rate of transients, etc..

Carpeting is so dense it's normally only used on subs and then only 'noisy' ones. In sufficient quantity, fiberglass insulation, wool, polyfil, etc. stuffing can increase the cab's apparent acoustic Vb, i.e. lower its Q: http://web.archive.org/web/20021007....cyberglobe.net/caraudio/resources/fiberfill/
Note that a well designed rectangular box only requires minimal density lining of the top, back and one side wall and even less for cabs optimized for minimal reflections.

Can't say I agree with the others about high Q drivers being only suitable for sealed and/or de facto having too low a SQ since some of the highest SQ speakers (including horns) I've built used high Q drivers. As Tom Danley has repeatedly pointed out in both postings and in the products he designs, it's all about using the right driver for the app. Of course none of this is meant to mean this particular high Q driver has any SQ to speak of, just that knowing MTX and many other car audio manufacturers have a long history of selling junk we shouldn't dismiss them all out-of-hand for HIFI/HT apps.

Anyway, traditionally, high Q drivers are used in OB, IB, TL, MLTL, true bass-horns and really large vented alignments, so it boils down to how big can you tolerate. At a glance it looks like ~7.773 ft^3 minimum is required to get to a useful ~20 Hz Fb, though it could be made tall to fit in a corner or lay down along a wall such as this MLTL:

L = 84.875"
CSA = 158.247"^2 (suggest 16" x 9.9")
zdriver = 29.187"
zport = 81.875"
dport = 5"
Lport = 8"

All dims i.d. and approximate. Sim uses 0.3 lbs/ft^3 of polyfil spread along its length.

GM
 

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i dont think this driver deserves 8 cubic feet of box

in fact i dont think any 12" driver deserves a box bigger than 3 cubic feet

im not saying it wouldnt work ... im saying that anybody willing to look at a 8 cubic foot box every day might as well put a 18" driver in there

just because you can do something doesn't mean its worth it
 
Lokalazeros said:

........i think I'll do a separate cab for it because I'd like to try some other enclosure design too (found some tapped horn design at http://www.cowanaudio.com/ that seems pretty interesting.)

Greets!

Due to the driver's relatively high Vas, low mass corner (Fh), it takes a big box to go low, 505.914 L net, so a bit large for your room size and with a small room, probably way over-kill, so hard to justify the size.

Still, it doesn't sim too shabbily if the specs are fairly accurate and could have its footprint halved for 375.075 L net along with a ~6 dB increase in output if a clamshell isobaric pair was used combined with a 300 W amp capable of driving a nominal 2 ohm load as simmed.

Really, this one is so overkill for your room size that I doubt you'd ever use > 20 - 25 W unless you're hearing's as far gone as many older 'rockers', but SQ would be a moot point due to it barely moving even on < 20 Hz spikes:

GM
 

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I knew It was going to be an overkill, until I realisez that I had a V.U. meter on my main amp (Aurex St-335 MKII). When on normal listening condition, it seems like im not going really high, less than .5W (that is, IF the Vu Meter is accurate). Then I knew it was going to be one hell of an overkill:bigeyes: Anyway... I'll probably move it out to the basement (we have a 3/4-the-house-size room in which there is a computer and some videogame consoles) and build a smaller, less powerfull, accurate *I hope*, sound system.

I've read every entry since last time, altought I won't reply to each, I'd like to thank you for replying. I'm learning a lot :)
Will continue to look in the ad papers/pawn shop for a used amp; and probably going to buy this week or next one.

I can't wait to ear it:D

Have a good day !
 
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Lokalazeros said:
I knew It was going to be an overkill, until I realisez that I had a V.U. meter on my main amp (Aurex St-335 MKII). When on normal listening condition, it seems like im not going really high, less than .5W (that is, IF the Vu Meter is accurate). Then I knew it was going to be one hell of an overkill:bigeyes:

it seems you don't understand the logarithmic scale

500W is only 30 decibel more than 0.5W ... thats without compression

in reality you will get about 4db of compression due to voice coil heating and another maybe 2db from the driver operating outside of the gap so in the end 500W will only be about 24db more than 0.5W

24 db is the difference between lowest and highest setting on a +/- 12db equalizer ... its not all that much

i see amplifiers as an investment anyway, to me its not an issue of how much power i need or things like that ... if the amp looks like its worth the asking price and i can afford it i will buy it ... doesn't matter if i need it or not
 
Hey
I finally finished building my sealed box, and wanted to give some feedback, since you helped my a lot.
Since I haven't got my amp yet, i've put the sub in my car. (I was already running a pair of Kicker Comp, in their factory box) Well, I was impressed, really. Altought it seems to take a little more power to power the 12'' versus 2x 10'', the Mtx seems to have more punch, kicking you harder in the chest than the 2x 10'' I had. (Maybe the 12 is moving more air than the 2x10.). I still have to do the finish on the box (dont know if I will actually paint it or whatever), but I can't wait to have an amp in my room to power it :D

The box was done to the MTX specs sheets (about 12'' 1/2 x12'' 1/2x 15''), heavily glued and screwed each two inch for maximum stiffness and strenght. (I don't actually know If it was a screw overkill, but i love the way it look (and sound):D )

thanks again, I hope I'll someday be able to help other like you did for me.

Have an happy day.
 
Greets!

Don't know, two 10" have more piston area and I assume more power handling than the 12", but box alignment could account for the difference.

Hmm, the MTX box appears to be designed for car audio use, so unless the amp has considerable bass boost down low and enough power to handle it, it probably won't have much real bass even in a corner, just lots of mid-bass 'punch'.

Anyway, you're welcome and hope it performs good enough for you.

GM
 
Hello,
In fact, the 2 10'' together have the same power handling (rms) than the 12''. (300w)

it probably won't have much real bass even in a corner, just lots of mid-bass 'punch'
After checking the setting I had put on my car amp to make the 12'' sound good, I have to agree with you. it's going to take a lot of bass boost down low.

I am happy with the sound I get in my car, but I think that using this sub in my room will me way to complicated and a waist of my time. As you said GM, the sub itseft was intented to be used in a car, not as a hi-fi device.

I think the best thing to do would be to paint it/whatever and sell it, then look at what I really need in my room. After establishing a list of main goals, I will be able to upgrade my system in an intelligent way. (I realised that actually my 3 speakers :)xeye: ) used in stereo may not be the best for audio reproduction. (a pair in front of me at 60 (right) and 120 cm(left), then another speaker of another brand and of another size of driver, probably with other crossover setting, at my left, 45 degree behind.

Afterall, IMHO, It is worthless to have an excellent 20-80hz if anything higher can't be reproduced in a descent way. (Already made this mistake in my car, don't want to do the same in my room).

Back to the lab :)

Have a beautiful day.
 
Greets!

Absolutely! It's the mains that provide almost all of the sub output's harmonics, so bass SQ is for the most part a function of the main's SQ when XO'd at < ~80 Hz.

Yes, if you want a relatively small sub and deep bass you'll need an appropriate low Fs/Vas, high power/Xmax sub driver and a high power amp to drive it.

GM
 
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