Hi everyone.
Marcelo here from Argentina.
I created this thread to ask some questions and things about my new project that will be begining any time now.
I recently bought a Yamaha RX-V673 on Ebay, it was shipped from the US to Argentina yesterday.
I already have a pair of speakers: Technics SB LX-70. Not the best for Hi-Fi audio, but for now it will work.
The main problem Im facing is to find a suitable subwoofer to reach 20hz.
Why 20hz¿. Well, the only "real" reason is to try to match a THX certified subwoofer. If im gonna do something on my own, better try to do it the best I can (and cheaper too).
For what I've estimated, the best options are 12" or 15" subwoofer, the problem is that here, in Argentina, it's almost impossible to find a sub or a speaker that has Fs >= 20h and < 30hz.
The only one is the Eminence LAB15, but still I could not find it (and it's pretty expensive too, around 500u$s here).
I say Fs >= 20h and < 30hz, because with Fs higher than 30 is harder to get lower freq with a cabinet (and port tunning) that would fit in my room. In fact, according to my calculations, an Fs=25hz driver, could reach 20hz @ -3dB with ~10 cubic ft box (vented).
The only suitable option could be a car subwoofer. Theres a huge market of them and variety. Any one could recommend one? or some TS parameter that I should look for besides the Fs?
Im kindda interested in the Audiopipe TS-VR12 (Subwoofers | TS-VR12) and it's pretty cheap too (around 150u$s).
Other good option is the MTX Mobile 10"
(MTX Mobile 10" Dual 4Ω 250W RMS Subwoofer)
Wich according to my calculations with Bassbox Pro, it could go even lower with a cabinet of 150 liters (5,297 cu. ft.),
Here you can see the room layout (estimated)
(Baticovacha could be translated as Bat-crib
The project is to try to reach 7.2 channels in that room.
To other subwoofer probably could go under the Futon (sofa)... at least that's the idea. Anyone has ever tested something like it?
To power both subwoofer Im NOT going to use a standar subwoofer power amplifier. I'd rather use a rackeable stereo power amplifier (the one's you use in professional audio).
So I could put it under the Yamaha receiver and when I need more volume (or gain), just go there and turn it up, avoiding to go to each subwoofer to turn on/off, volume, etc.
The power amplifier could be the Behringer Euro2000, but Im still looking; mainly because not every Power Amp goes under 20hz.
What do you guys think?
Any recommendations, opinnios and comments will be appretiated!
Thank you!
Marcelo here from Argentina.
I created this thread to ask some questions and things about my new project that will be begining any time now.
I recently bought a Yamaha RX-V673 on Ebay, it was shipped from the US to Argentina yesterday.
I already have a pair of speakers: Technics SB LX-70. Not the best for Hi-Fi audio, but for now it will work.
The main problem Im facing is to find a suitable subwoofer to reach 20hz.
Why 20hz¿. Well, the only "real" reason is to try to match a THX certified subwoofer. If im gonna do something on my own, better try to do it the best I can (and cheaper too).
For what I've estimated, the best options are 12" or 15" subwoofer, the problem is that here, in Argentina, it's almost impossible to find a sub or a speaker that has Fs >= 20h and < 30hz.
The only one is the Eminence LAB15, but still I could not find it (and it's pretty expensive too, around 500u$s here).
I say Fs >= 20h and < 30hz, because with Fs higher than 30 is harder to get lower freq with a cabinet (and port tunning) that would fit in my room. In fact, according to my calculations, an Fs=25hz driver, could reach 20hz @ -3dB with ~10 cubic ft box (vented).
The only suitable option could be a car subwoofer. Theres a huge market of them and variety. Any one could recommend one? or some TS parameter that I should look for besides the Fs?
Im kindda interested in the Audiopipe TS-VR12 (Subwoofers | TS-VR12) and it's pretty cheap too (around 150u$s).
Other good option is the MTX Mobile 10"
(MTX Mobile 10" Dual 4Ω 250W RMS Subwoofer)
Wich according to my calculations with Bassbox Pro, it could go even lower with a cabinet of 150 liters (5,297 cu. ft.),
Here you can see the room layout (estimated)
(Baticovacha could be translated as Bat-crib
An externally hosted image should be here but it was not working when we last tested it.
)The project is to try to reach 7.2 channels in that room.
To other subwoofer probably could go under the Futon (sofa)... at least that's the idea. Anyone has ever tested something like it?
To power both subwoofer Im NOT going to use a standar subwoofer power amplifier. I'd rather use a rackeable stereo power amplifier (the one's you use in professional audio).
So I could put it under the Yamaha receiver and when I need more volume (or gain), just go there and turn it up, avoiding to go to each subwoofer to turn on/off, volume, etc.
The power amplifier could be the Behringer Euro2000, but Im still looking; mainly because not every Power Amp goes under 20hz.
What do you guys think?
Any recommendations, opinnios and comments will be appretiated!
Thank you!
You did not mention how large the subwoofer cabinets can be. This is a very important variable in the equation!
With a large (e.g. more than 10 cubic feet) cabinet, there are many 12" drivers that could be used for a vented loudspeaker that can easily reach 20 Hz, or lower.
I am not familiar with drivers that are available in your country, and within your budget, but if you can make the cabinet very large you can often use a less expensive driver, and let the cabinet and port do the work of creating a lot of low bass energy.
The driver you mention look to me to be car sound drivers. These are not good for low bass in a home setting. I did not see the Fs listed for the Audiopipe driver for instance. You need to find a driver or drivers that provide all the Thiele Small data in a data sheet, and the frequency response. Since (I assume) you do not have a way to measure these parameters for the driver, you should make sure that you purchase one that is very high quality and has clearly stated specifications. It would be better if you could measure the parameters for the actual driver you end up buying, because they can often be +/- 20% from the manufacturer's numbers.
What companies that sell speaker parts can you purchase from in your country? PA drivers can work too in large boxes. What is your upper cost limit for the driver?
-Charlie
With a large (e.g. more than 10 cubic feet) cabinet, there are many 12" drivers that could be used for a vented loudspeaker that can easily reach 20 Hz, or lower.
I am not familiar with drivers that are available in your country, and within your budget, but if you can make the cabinet very large you can often use a less expensive driver, and let the cabinet and port do the work of creating a lot of low bass energy.
The driver you mention look to me to be car sound drivers. These are not good for low bass in a home setting. I did not see the Fs listed for the Audiopipe driver for instance. You need to find a driver or drivers that provide all the Thiele Small data in a data sheet, and the frequency response. Since (I assume) you do not have a way to measure these parameters for the driver, you should make sure that you purchase one that is very high quality and has clearly stated specifications. It would be better if you could measure the parameters for the actual driver you end up buying, because they can often be +/- 20% from the manufacturer's numbers.
What companies that sell speaker parts can you purchase from in your country? PA drivers can work too in large boxes. What is your upper cost limit for the driver?
-Charlie
Thanks for reading, Charlie!
Yeah, the Audiopipe didn't have enough data to calculate exactly.
The size of the cabinet Im attempting is aroung ~10 cubic feets, more or less. Mostly because of room limitation and design. I dont like the idea of a 2mts tower on the corner. (thats why Im looking for low Fs)
If you check the MTX sub, it has all the parameters:
The price of the Audiopipe is around 160u$s, the MTX is 180u$s.
My budget could go to 200u$s for a subwoofer that "does the job", meaning a cheap subwoofer that could do 20hz and be cheap. Still, I could spend around 400u$s if I find something really good.
Speakers brands here in Argentina: 18 sound, Eminence, DAS, DUS, JBL, Selenium. There are others but these are the best known.
Car Subwoofer brands: Bravox (Brazilian), Bomber (Brazilian), Audiopipe and many others.
The problem, of course, is that is more easy to find a suitable car sub than PA sub/speaker.
Im still looking, testing and searching...
He also loves Huey Lewis and the News... right?
An externally hosted image should be here but it was not working when we last tested it.
Alpine doesn't even exist in argentina.
Well, to be sincere, there are some car stereos and very few speakers, but nothing more. Very little variety and stock. Also, theres only one seller who offers Alpine...
You get the idea
Yes, and it works very well. Being so close to the sub means it does not need to play that loud which means less spill into other rooms. It also gives a nice bass shaker effect without the uneven response and "sofa modes".
Having to be small if you want to fit it under the sofa does pose a design challange.
Have in mind that Im going to put two subs. One goes at the front and the other under/rear the sofa.
I was thinking in using low profile car subwoofers because the space between the sofa and the floor es very small (around 12cm height).
[After some calculations]
Cabinet for under the sofa:
At least it has a decent size an volume.
Any speakers recommendation or specs that I should look for?
I'd checked it.- It's a pretty nice work!
The Jbl GTO1214 could do the work. In a 150 liters cabinet, it has a very smooth response.
Prices are almost the same as the MTX.
Jbl GTO1214 = 211u$s
MTX Mobile 10" = 180u$s
JBL GTO1014 = 155u$s
Comparison in a 150 liters cabinet:
I think that the JBL could be a very good choice for value and money. Very versatile too.
Now I have to find a suitable power amp for it!
It looks like you are on the right track.
You should check a couple additional things:
- maximum vent/port velocity (should not exceed 25m/s)
- what are the vent resonance frequencies and magnitudes
If your current box modeling program can not show the vent resonances, download a copy of Unibox from my web site:
UniBox - Unified Box Model for Loudspeaker Design - Kristian Ougaard
The vented box section has an option (a checkbox) that says "Include effect of port resonance". It's located on the "Speaker Design" tab, below the vented box parameters, in cell A79. Unibox is a free Excel box modeler.
-Charlie
Thanks man! Did it! Almost the same results as Bassbox Pro.
But... Well, this is awkward... The maximum vent/port velocity is 44m/s.
At 20hz is around 31m/s.
Ermm... What should I do, Charlie?
Let me answer your question and add some background info:Thanks man! Did it! Almost the same results as Bassbox Pro.
But... Well, this is awkward... The maximum vent/port velocity is 44m/s.
At 20hz is around 31m/s.
Ermm... What should I do, Charlie?
Problem: vent/port velocity is too high
Q: Why is this a problem?
A: when the port velocity is "high" the air can not flow in and out of the port as fast as it needs to because turbulence develops and this causes the air flow resistance to increase quickly. That causes "port compression" which means the effectiveness of the port decreases and it can't keep up with the output from the driver. The result is a sag or droop in the frequency response around the port tuning as SPL is increased. Another problem caused by vent velocities that are "too high" is "chuffing". Chuffing is an audible noise (but not resonance) made by the air rushing in and out of the port.
Q: How can I reduce the vent velocity?
A: The following help to reduce port velocity:
1. Increase the box size (this will result in a shorter vent length for the same tuning) - see note below.
2. Increase the diameter or cross sectional area of the port (this will result in a longer port length).
The last point brings up the other thing I mentioned: port resonances. These are similar to what you hear when you blow across the top of a glass bottle. When ports become "long" compared to their diameter, they make for good pipe resonators and sometimes the lowest resonance frequency can be under 200Hz. This is why I always suggest using Unibox to model the frequency of the resonance(s), and to check their amplitude. As long as the resonances are small, no problem. But if they are large in amplitude they can be audibly annoying. Keep in mind that a crossover will not effect the resonance, because it is created by the air rushing in and out of the port, not by that frequency being emitted by the driver itself.
Can you post a plot of the frequency response from Unibox with the "show port resonances" option enabled?
-Charlie
Note: increasing the box size will also change the low frequency response of the driver in the box and may lead to a hump in the response. The hump can cause ringing of the time domain response (transient response) similar to what is observed for a high Q sealed box response.
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The other thing I should mention is that the plot of vent velocity is valid for a constant input signal level as a function of frequency, that is the bass frequencies around tuning and the higher frequencies (e.g. 50Hz and up) have the same amount of power. This is not the case for music. If you listen mostly to music, there will be little to no power in the music spectrum below about 30Hz. Your vent velocity peak is occurring around 18Hz and by 30Hz is it well under the 25m/s limit. So on music type program material the high vent velocity might not be a practical problem. On the other hand, port resonances will be more of an issue to worry about, so I recommend, again, to check those.
-Charlie
-Charlie
Ok. Got it!
Damn, you know a lot...
I updated the port diameter.
And here is the Freq. response:
A stupid question... I googled around and I couldnt find a concrete answer.
The position of the speaker on the box will affect the resonant freq?
What I mean is that if you put the speaker on the middle of the box, the air would circulate differently that if you put it on the right next to the inner wall/side.
For example, here are some graphics to explain my thought. Lets asume it's a "perfect" or well made cabinet with all the specs and requirments, etc etc.
If you place the speaker in the center it would sound the same that if you put it on the right? Im not an engineer, but It's only logical that the air movement will be different and that may affect que resulting freqs.
(The big tube is the air vent).:
Or maybe Im just crazy... just thinking out loud
No. The driver position and relationship to the port will not influence the port resonances. Those are created by the port in response to the air moving through it. It's a property of the dimensions of the tube.
The resonances you show are probably on the limit of what would be OK. If you plan to put the whole thing under your couch and don't have the port aimed directly at your listening position, the couch and floor will likely adsorb or mute some of the 200Hz resonance. Keep in mind that close proximity of the port tube openings to other surfaces can influence the tuning. For instance, if the port tube end that is inside the box is within about 1 tube diameter of a wall, the resonance of the tube can change WRT the tube being in "free air". Same for the outside end of the port tube - keep in mind that it may end near the the couch itself. You can measure this effect and adjust for it, or you can try to design it in to the sub from the beginning. Usually vented boxes require some final "tuning" of the port (adjustment of the length by +/-10%) and this requires measurement of the impedance curve of the completed driver in box. There is a good tutorial on this at the end of this Leach paper, starting where it says "system verification":
http://users.ece.gatech.edu/~mleach/ece4445/downloads/ventedbox.pdf
-Charlie
Ok. Sorry for the stupid question
Thanks again!This sub will go next the Tv like in the picture of the room in the first post.
It wont fit under the sofa.
The one under the sofa Im still looking, maybe it will be a low profile car subwoofer.
I think Im going to buy the JBL one of these days, if I find it for the right price.
Just called to an audio store and the price was 350u$s.
Still if you or anyone has a better recommendation or opinion it's very welcome!
With room gain I see no reason to reason to tune so low. IMO you trade real bass >30hz for LFE that only rattles stuff from shelves.
I know, I know. It isn't the best for some ears. I dont like either that it shakes the whole room. But i want to have the full range of freqs on my HT, mostly in the sub freqs.
Remember that this HT will have 2 subwoofers. Would you agree to put a sub at 20hz and the other >30hz?
It is true that car subwoofers (which I did a lot of work on) are "wrong" for home subs. BUT. It is also true that in Latin America it is hard to find drivers, and very expensive to order from overseas.
Plus, some car subs (like that MTX) have a higher Q. In a large sealed box, or with a low-tuned port, that can actually be fine for home.
I can think of no reason to put one sub at 20 Hz and another at ">30 Hz" (do you actually mean highpass filtered?). Run subs in parallel so they can reinforce each other.
A lot of your simulation plots show a rolloff from high frequencies but then a small bump in the bass. This indicates resonant behavior. It doesn't automatically mean terrible sound, but I really prefer to see plots that keep rolling off smoothly.
If you keep posting data from any subs you find affordable, we can keep critiquing.
Plus, some car subs (like that MTX) have a higher Q. In a large sealed box, or with a low-tuned port, that can actually be fine for home.
I can think of no reason to put one sub at 20 Hz and another at ">30 Hz" (do you actually mean highpass filtered?). Run subs in parallel so they can reinforce each other.
A lot of your simulation plots show a rolloff from high frequencies but then a small bump in the bass. This indicates resonant behavior. It doesn't automatically mean terrible sound, but I really prefer to see plots that keep rolling off smoothly.
If you keep posting data from any subs you find affordable, we can keep critiquing.
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