Planning a sound install into a mechanical reefer using a Digitrax sound bug (still working up the sound file).
I'd like to plan ahead for the speaker and since there is plenty of room inside a boxcar body for a speaker I'd like to get a good one that is suitable for what I'm assuming is low frequency generator reverb.
I have a few bass reflex speakers (8 ohm) that I got for another project.
The first one listed here:
RailMaster Hobbies Speakers
Would these work well for generator reverb? Does this type of speaker require an enclosure?
If no enclosure, how are these speakers mounted? I'm assuming the little hole must be kept clear for air to get in.
Any other speaker recommendation? High Bass instead?
Matt from Anaheim, CA and Bayfield, COClick Here for my model train photo website
Southwest Chief Planning a sound install into a mechanical reefer using a Digitrax sound bug (still working up the sound file). I'd like to plan ahead for the speaker and since there is plenty of room inside a boxcar body for a speaker I'd like to get a good one that is suitable for what I'm assuming is low frequency generator reverb. I have a few bass reflex speakers (8 ohm) that I got for another project. The first one listed here: RailMaster Hobbies Speakers Would these work well for generator reverb? Does this type of speaker require an enclosure? If no enclosure, how are these speakers mounted? I'm assuming the little hole must be kept clear for air to get in. Any other speaker recommendation? High Bass instead?
Well I don't use sound in my trains, but in another life I have been designing speaker systems for about 35 years. The speaker you linked to does not need any additional enclosure, it comes already mounted in an enclosure.
The speaker and the port need to remain as unobstructed as possible for best sound quality.
Since I'm not into this onboard sound thing for trains, I cannot recommend other products or comment on the performance of this product, but I hope that sanswered at least part of your question.
The "air" does not actually get in or out of the port, but the sound waves or "pressure" does. So any obstruction will change the sound of the speaker.
Sheldon
Thanks for the information Sheldon.
Ya' can't do it. The ohm rating is wrong.
If I remember correctly the digitrax soundbug using something weird like 28 Ohms.
A port opening is typically used to extend low frequency bass around a narrow frequency. But to be honest, I don't think this will help much. I would doubt you would get another octave lower.
(Someone else who designed his own speakers and built his own amplifiers)
-D
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
I wondered about the Ohms rating.
SoundBug is 32 Ohms, comes with 28mm speaker so you were close
However their documentation indicates you can use a speaker with an impedance of 8 Ohms or greater.
Use the Digitrax speaker and build your own enclosure patterned after the bass reflex design. I do not know the specs of the Digitrax speakers.
With some styrene, this would not be difficult. Some DCC sellers will probably have some ready for a speaker.
I make my own speaker enclosure with styrene.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
I have installed a lot of bass reflex speakers. They are already in an enclosure with the bass port built in. There are actually two sizes of them. The bass reflex is made for narrow diesel installs. The 27mm High Bass speaker he has listed is better and can go in a reefer very easily. This speaker has the best low end bass available from all that I've tried. This is also available in a smaller diameter although he doesn't have it listed. I normally mount my bass reflex with various tacky glues or thin to thick double sided tape. I have always removed the tabs. Mounting where the speaker points down to exit and get sound reflectivity is usually best.
I would not want this 8 ohm speaker being driven by the 32 ohm Digitrax. I have done it and even added in a resistor, but it wasn't good sound. Of course the Digitrax processor is not the best to begin with.
You would be better getting a large 32 ohm speaker and building an enclosure. In your reefer there's lots of room. You can actually use some parts of the body of the box car to act as enclosure sides and just close in the rest for a large enclosure.
Richard
Appreciate all the advice. Good info here thanks
And I too like to make my own enclosures out of styrene. Easy to do, and sounds great. Did this with a high bass speaker in my Bachmann 2-8-0 (Tsunami sound decoder).
Soundbugs are EIGHT OHM. End of story. If I was at home I'd take a picture of mine with the still attached factory speaker it came with, complete with the 8 ohm marking on the back.
Some of the motor/sound comb decoders came with 32 ohm speakers, which accounts for the lack of volume. They ALL work with 8 ohm speakers.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Rich,
The whole point of the packaged speaker and enclosure is that the speaker is actually tuned to the enclosure. Simply building a similar enclosure and using a different speaker is not very likely to have as good of a result.
Bass Reflex enclosures are based on a complex set of formulas that take into account the acoustic properties of the speaker. If the speakers stiffness and resonance are not within specific suitable ranges, one of two things will happen.
One, it might not sound good in ANY ported or base reflex enclosure, or two, the proper enclosure and port may be of dramaticly different sizes than those that work with the other speaker.
Some speakers have stiffness and resonance factors that make them better suited for sealed enclosures (called acoustic suspension), others are better for vented or base reflex enclosures.
Even in large HiFi speakers, the smallest changes in enclosure volume or port area/volume can have dramatic effects on sound quality - so just imagine how that could effect speakers this small.
Because of the variables involved, I would recommend using sealed enclosures in all "do it yourself" cases, and would only consider a ported enclosure as a package like the one the OP linked to.
Just my thoughts based on 35 years of HiFi speaker design as a hobby and part time business.
Because of my experaince and trained ear, HO sound systems are simply not of any acceptable sound quality to me, surely not at the price and/or work involved. But I hope this info helps all you "sound" guys.
ATLANTIC CENTRAL Rich, The whole point of the packaged speaker and enclosure is that the speaker is actually tuned to the enclosure. Simply building a similar enclosure and using a different speaker is not very likely to have as good of a result. Bass Reflex enclosures are based on a complex set of formulas that take into account the acoustic properties of the speaker. If the speakers stiffness and resonance are not within specific suitable ranges, one of two things will happen. One, it might not sound good in ANY ported or base reflex enclosure, or two, the proper enclosure and port may be of dramaticly different sizes than those that work with the other speaker. Some speakers have stiffness and resonance factors that make them better suited for sealed enclosures (called acoustic suspension), others are better for vented or base reflex enclosures. Even in large HiFi speakers, the smallest changes in enclosure volume or port area/volume can have dramatic effects on sound quality - so just imagine how that could effect speakers this small. Because of the variables involved, I would recommend using sealed enclosures in all "do it yourself" cases, and would only consider a ported enclosure as a package like the one the OP linked to. Just my thoughts based on 35 years of HiFi speaker design as a hobby and part time business. Because of my experaince and trained ear, HO sound systems are simply not of any acceptable sound quality to me, surely not at the price and/or work involved. But I hope this info helps all you "sound" guys. Sheldon
Sheldon,
Resonance is one reason I use thick cardstock sometimes vs styrene to make an enclosure. Also taking into account the possibility of insulating the speaker and/or enclosure from the loco itself. The resonance you can get from the loco itself can sound as interference. High Bass sound takes high energy to produce which is normally found in larger speakers (the Bose example is one where maximizing bass with minimal speakers works however, but those are very controlled sound waves). So, in general as you know, the larger speaker, with larger magnet and more high quality cone normally results in better sound.
The Bose example points out as do you, how we handle the front and back sound waves is important and not just a matter of simply putting the speaker in the loco faced down.
Actually at this point I am experimenting with multiple speaker installs trying to maximize the total sound effect. Each one trying to capture different frequency response ranges. BTW, I have found some of the specifications of the speakers, especially referencing the response ranges to be questionable. So I am developing a database. Including installs that didn't work and had to be redone.
I did not know your background in sound and may be coming your way for some advice as this adventure continues.
Wish me luck.
I actually used some software to design a folded horn speaker enclosure for the H-8 tender. The number I was seeing managed to extend the frequency down to ~130Hz. Not to shabby. But the entire insides had to be gutted.
Backwave resonance can be controlled somewhat by stuffing the backside of the speaker enclosure with polyfill or loose fiberglass-loosely packed. That last tidbit is important. You lose the sound deading properties of the materials if you pack them too tight.
DigitalGriffin I actually used some software to design a folded horn speaker enclosure for the H-8 tender. The number I was seeing managed to extend the frequency down to ~130Hz. Not to shabby. But the entire insides had to be gutted. Backwave resonance can be controlled somewhat by stuffing the backside of the speaker enclosure with polyfill or loose fiberglass-loosely packed. That last tidbit is important. You lose the sound deading properties of the materials if you pack them too tight.
What software, can I get it? That sounds great. We've had to gut some weight out of locos to get the sound to propogate properly. Which gets to be a trade off vs pulling.
We've tried backfilling with foam, not fiberglass. When you say fiberglass, you mean the cloth before adding resin, correct? Why fiberglass, that's interesting?
Train Modeler DigitalGriffin: I actually used some software to design a folded horn speaker enclosure for the H-8 tender. The number I was seeing managed to extend the frequency down to ~130Hz. Not to shabby. But the entire insides had to be gutted. Backwave resonance can be controlled somewhat by stuffing the backside of the speaker enclosure with polyfill or loose fiberglass-loosely packed. That last tidbit is important. You lose the sound deading properties of the materials if you pack them too tight. What software, can I get it? That sounds great. We've had to gut some weight out of locos to get the sound to propogate properly. Which gets to be a trade off vs pulling. We've tried backfilling with foam, not fiberglass. When you say fiberglass, you mean the cloth before adding resin, correct? Why fiberglass, that's interesting? Richard
DigitalGriffin: I actually used some software to design a folded horn speaker enclosure for the H-8 tender. The number I was seeing managed to extend the frequency down to ~130Hz. Not to shabby. But the entire insides had to be gutted. Backwave resonance can be controlled somewhat by stuffing the backside of the speaker enclosure with polyfill or loose fiberglass-loosely packed. That last tidbit is important. You lose the sound deading properties of the materials if you pack them too tight.
http://www.avsforum.com/avs-vb/showthread.php?t=1295597
http://www.ehow.com/how_15992_soundproof-room.html
Fiberglass is a very common substance used in cheap speakers behind the drivers to help control backwaves. It's also used for sound insulation in home theaters.
Rockwool also works even better due to it's mass. But it's messier and harder to work with, and not appropriate for such a small space.
Foam is okay, but the two above really do work well. They have a high STC due to their energy absorbing pourous cavities. http://en.wikipedia.org/wiki/Sound_transmission_class
No, fiberglass like the insulation in your walls and attic.
"poly fill" - polyester pillow stuffing, works well also.
Digital G and Sheldon,
Thanks.
I deal more in fiberglass cloth and so that was my first reference.
That folded horn reminds me of the Bose system. Hard to do in a diesel, I'll have to think about it. We've been toying around with propagation like Atlas does with they're A Frame. I made an A Frame and put it into an ALine SD90MacH kit we built. It didn't work well at all, so we went a different direction. We actually tried about 4 to 5 different install theories due to the large space available. I learned a lot with that one.
BTW we ended up putting two 1.06 HB in the radiator, in parallel to get max bass. As I recall the reflex was in 3rd place. It was the Tsunami Alco 251 V16, closest thing I could find to an H engine. The sound files for that are very heavy in bass and overdrive most speakers.
Here's a Youtube video with some spekaer comparisons - watch Part 2 as well:
http://www.youtube.com/watch?v=4uwdWaN05fU&feature=mfu_in_order&list=UL