Building boombox: Choosing right speakers. SP-60 or HP-10T

[Krille]

Time to build a boombox, and I have been looking on some speakers and boxdesigns for them. HP-10W seems to be the shit but is hard to get a hold of now so, the alternative is HP-10T which some seem to hate (haven't found out exactly why?). Two of the Hp-10T is one idea I have though.

The second is Monacor SP-60 which everyone seem to like and I will be going with four of them if I choose this speaker. (The same cost as for two Hp-10T)

The tweeters I'm going for, whatever bas/midrange speaker I choose, is piezos. I'm looking at Monacor MPT-001 or 005. I want something portable with volume, bass and okay sound for drunk people overall, not HI-FI quality. And I know that bass under 100Hz outdoors is hard to get without sufficient power.

I'm going to use the Amp6 Basic for this.

I have been trying out WinISD to get a boxdesign that seems to work, have mostly been playing around with the SP-60 though and then a 85Hz tuned, 12.5 liters vented design on the box for two speakers in a bi-polar design (not going for magnet to magnet) is my plan as it seems to be okay and give + 3db at around 100Hz. (Guide me here please though, I'm a noob at this).
Will be skipping the ports at first to see how the play in a closed environment, the Qtc is around 0.7 in that case.

The box for HP-10T might just be a cube, like a half Boominator with two speakers in bi-polar placement. Haven't calculated anything on this design though.

What do you think, two HP-10T's or four SP-60? I'm planing on playing in mono if I choose the HP-10 to get greater volume and stereo (with the option to go all mono to increase volume if it sounds okay) with the SP-60.


Edit: I know the relevance of dB and how much +3dB is, but outdoors with a lot of the bass being eaten up isn't this the best idea?
12L with a tuning of 65Hz might be more smoother though and not so tiring for the ears.

[gnome]

You must be going to Roskilde!

[Krille]

Wont be going that far unfortunately, just some local festivals in Sweden (:

[Krille]

Well, I went with the SP-60's in a vented bi-polar design. This is the result:

IMG_20120704_163254.jpgIMG_20120704_163319.jpgIMG_20120704_163331.jpgIMG_20120704_163419.jpg

Crappy pictures at the moment :/. The boombox has a "hat" (namned the boombox "DubbelKeps" in swedish, "DoubleHat" in english ) so it can stand in the rain and glasses of liquid can be placed on top of it with no worries if you spill something. The sound doesn't radiate as much upwards as without the hat but hey, you sit in front most of the time so you don't notice any real difference! I am a little disappointed on the volume side but I'll have to try it out more on bigger parties.

Someday I will throw some paint on there because it looks like crap right now ;D.

Here's the mighty serious festival campsong for the box: http://soundcloud.com/krillee/keps-mix6 (long story!)

[V-bro]

Well, I went with the SP-60's in a vented bi-polar design. This is the result:

IMG_20120704_163254.jpgIMG_20120704_163319.jpgIMG_20120704_163331.jpgIMG_20120704_163419.jpg

Crappy pictures at the moment :/. The boombox has a "hat" (namned the boombox "DubbelKeps" in swedish, "DoubleHat" in english ) so it can stand in the rain and glasses of liquid can be placed on top of it with no worries if you spill something. The sound doesn't radiate as much upwards as without the hat but hey, you sit in front most of the time so you don't notice any real difference! I am a little disappointed on the volume side but I'll have to try it out more on bigger parties.

Someday I will throw some paint on there because it looks like crap right now ;D.

Here's the mighty serious festival campsong for the box: http://soundcloud.com/krillee/keps-mix6 (long story!)

Volume wise you might get some gains from placing a smaller input capacitor on the amp (like 470nF) and put up the gain through the roof in the amplifier you are using... (AMP6?)

ALso I am not so sure if that bass reflex configuration is optimal, did you ask Saturnus about this?

[Krille]

Volume wise you might get some gains from placing a smaller input capacitor on the amp (like 470nF) and put up the gain through the roof in the amplifier you are using... (AMP6?)

ALso I am not so sure if that bass reflex configuration is optimal, did you ask Saturnus about this?

I got a 0.22 uF input capacitor to reduce the lowest frequencies and the most sensitive input configuration on my AMP6. I guess I'm used to louder boomboxes like some old Hitachi's witch go to about the same volume and have great battery time. They don't sound as good on louder volumes though.

No I haven't asked Saturnus directly, tried to make this thread to get some help but decided to to read everything I could find about the speakers in the forum and make my own box-setup that was small enough and had acceptable bass output. I used WinISD for this and this is the graph and vent conf.:
Capture.jpgCapture2.jpg

[V-bro]

They can survive a beating though, I've had these speakers at first (more than 20 years ago) in a long column shaped enclosure, bass reflex bort at the bottom and about a meter high, quite narrow baffle and about 20cm deep. I remember how I was blown away by the sound. I used a Phillips tweeter (25mm soft dome) then and just a single cap. I owned a pair of Mission 762 speakers back then and remember how they beat them in several ways in terms of bass impact, smoothness of the sound. When well implemented these can sound very very well. I can see a few things in your design that will give some minor or worse problems. Like the countersinking of the speaker hole. This has been proven to me to give distortions as I've proven with measurements on the Megamini project. Also I remember Saturnus mentioned that two woofers in BR should have their own space and port, though I am not sure how he solved that in the Boominator. I do know from experience that I have made a few designs (protos) in the past with a single box and port and two drivers that never really managed to perform well.....

[Krille]

Yeah they seem to handle whatever you throw at them, the amp goes to the limit before they do! As you have written before, the only real negative thing about them is the thin casing (can't find the correct word for it now) and rather heavy magnet witch combined makes it vulnerable. The speakers I got had already taken a beating under shipping even when properly packed. You can probably blame the careless handling under delivery for that though.

Oh okej? I did the countersinkning because I read somewhere here that they needed it to actually sound better and have more breathing space when mounted front to back . Guess that was wrong then. Oh well, haven't noticed any distortion yet, the only thing that I don't like is the rather sharp tweeters, but what can you expect from cheap piezo-replicas. Haven't played them so much yet though so they probably get a little softer in time. When it comes to boomboxes and I'm not picky with the sound quality, especially not when these speakers are so cheap as they are. Will probably use the SP-60 for some more serious indoor speakers later if they survive to see what they can deliver when treated right.

The boombox sounds better than the other old boxes I have (Hitachi 3D8, CX-W700 and trk-8180) Its heavier but not much more than W700 if you use nine R20 batteries. For the price though, I don't think you get much better than 3D8 or even 3D7 if you want something light with okay "partysound" and able to play pretty loud if you need to, the batteries lasts forever too! They go pretty cheap on ebay. Thinking on replacing the speakers with something more sensitive that works in that small box and have better quality to upgrade it some. But that's a future project.
3D8.jpg

Edit: Have to say I'm somewhat disappointed over AMP6, you here everywhere that batteries last for days even when you max it most of the time (with 12-14Ah batteries) but with nine almost fresh LR20 batteries which should be equal to around 8Ah (even 12Ah if spec. stated on Wiki is correct) and had a voltage of 13.5v the voltage had dropped 1v when playing on max for around 10minutes, and dropped to around 12v when playing if not lower. That will give me about 30minutes on max before it goes under 10v and you'll have to lower the volumes because the chip shuts off because of voltage drop. And that is with modified inputcaps.
That's probably the worst thing about "digital" amplifiers, they hardclip when batteries runs out more and more and shutdown to protect themselves and you'll have to lower the volume to be able to keep on playing. Analog amplifiers often just distort more and more and the volumes lowers on its own until the batteries just can't keep up anymore.

Of what I have read the amp can draw maximum ~3Amp on peaks but ~0.3A is somewhat of an RMS current value on max which you can calculate on am I right? That should give me around 4 hours on regular cheap R20 batteries made of zink-carbon that can't handle as high current output as alkaline types. Hmm, I'll guess I have to try it with fresh batteries in real life.

How long can you all play with your batteries?


Im probably rambeling about a lot here, correct me if I'm wrong somewhere. Time to sleep..

[alexlangberg]

Remember that the voltage drop is not linear. It might drop from 13.5v to 12.5v in 10 minutes, then from 12.5 to 12 in 3 hours, then from 12 to 11.5 in 6 hours, then from 11.5 to 11 in 3 hours etc. It's hard to know exactly what the discharge curve is.

I have a boomblaster with an AMP6 and 2x SP-60, 4ohm version. It runs for so long on a 7Ah SLA battery that I never had the option to test battery life in one go but I would guesstimate about 20 hours at full volume. It's rarely used at full volume so you can probably add 50% or more to that in real life.

[Krille]

Thanks for the answer Alex, got me a lot calmer. I guess I just have to wait and see how long it runs in the end then.