Noob speaker box size help.
Hello everyone! I'm a newbie embarking on my first diy 2 way speaker build.I've read a lot of info on d.i.y. speaker building but can't understand a word of all the technical aspects. Basically I bought 2 Seas p17re h419 woofers and 2 seas 27tdf H1211-6 tweeters for the build. But for the life of me,I can't figure out the actual box size for them. The seas woofer specs say that vas for the woofer is 30.5l. Does that mean the actual box volume? Can someone help? Tia!
Hello everyone! I'm a newbie embarking on my first diy 2 way speaker build.I've read a lot of info on d.i.y. speaker building but can't understand a word of all the technical aspects. Basically I bought 2 Seas p17re h419 woofers and 2 seas 27tdf H1211-6 tweeters for the build. But for the life of me,I can't figure out the actual box size for them. The seas woofer specs say that vas for the woofer is 30.5l. Does that mean the actual box volume? Can someone help? Tia!
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Hi, Thanks a lot for pointing me to that post. I've read a lot of info regarding speaker building. But for the life of me,I just don't understand much of it. Could you help by looking at the specs of the drivers provided to determine the box size?
There's not an actual "correct" box size for a given driver. It's a decision making process based on many factors. Here are some questions to consider, as box volume affects power handling, low frequency extension, box shape affects other performance factors, etc.
Obviously, you have drivers to build a two-way speaker. Will there be a sub, or will you be depending on the P17's for low bass.
How much power to you expect to offer them?
What size is the room?
Are you planning on using active crossovers, or passive?
Will you be using DSP?
Are there any dimensions critical to the boxes you plan on building? Will they be on stands?
What kind of music, or more importantly, how do you listen- background music, annoy-the-neighbors volume?
Obviously, you have drivers to build a two-way speaker. Will there be a sub, or will you be depending on the P17's for low bass.
How much power to you expect to offer them?
What size is the room?
Are you planning on using active crossovers, or passive?
Will you be using DSP?
Are there any dimensions critical to the boxes you plan on building? Will they be on stands?
What kind of music, or more importantly, how do you listen- background music, annoy-the-neighbors volume?
download a box simulator such as Unibox or Winisd and learn to use it. It's very easy, and will help with your understanding of the concepts involved
Hi Tim! That's the best explaination I've gotten so far. Now I'm getting somewhere. Didn't know that the box size was dependent on the user's need and not based on the driver itself.
I had intended to build these strictly for 2 channel stereo music powered by a Denon avr 4308 rated at 140w per channel @8 ohms for the best clarity and best bass possible without subwoofers.��
I've obviously jumped the gun,buying the drivers and crossovers ( 4-8 ohm Pass Labs crossed at 2700) before these considerations. I actually went on to build a pair of vented boxes of internal dimensions 16cm wide,30cm high and 29cm deep out of 3/4" mdf ported with 2" by 5" long plastic ports I had lying around. What is your opinion based on this box,woofer,tweeter and crossover combination? Appreciate all the help I can get. Thanks!
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Hi Pete! Thanks for the reply. I tried them a few times but could'nt understand them. I'm an old school guy with very little knowledge of computer software and programs. Thanks though!🙂
Usually it's just a matter of entering parameters from the data sheet, clicking an update button, and looking at the pretty graph... ignore all the stuff that doesn't make sense. Usually they'll ask for more parameters than actually required to get a result, after a few times it becomes clear which are necessary & which not.
Hi all,
Op, you need to check the alignment for your 2-way. A nice alignment is around 15L/42Hz so your box with 12.5L is small considering you also need to add the port volume (and driver). The port size lenght is short also with 5". I would use two smaller ports in diam. or a larger one >2".
Op, you need to check the alignment for your 2-way. A nice alignment is around 15L/42Hz so your box with 12.5L is small considering you also need to add the port volume (and driver). The port size lenght is short also with 5". I would use two smaller ports in diam. or a larger one >2".
This is not the correct interpretation to take from Tim's post.
The box and port sizes are always dependent upon the given driver but there is flexibility depending upon your needs and goals. You are free to build a larger or smaller box and to tune it lower or higher, flat or peaky or with a more gradual roll-off but always dependent on the driver you are using and consistent with the relationships that exist for a vented alignment.
So for a vented box it's the net internal volume that matters, so the gross volume minus the volume occupied by the port, the drivers, any bracing, the xo and anything else solid that might be inside the box. Your internal gross volume is 13.9L, so you probably have something closer to the 12.5L net that Inductor mentions. Given that and a 2" x 5" port, your tuning frequency (Fb) is about 52Hz, F3 is about 49Hz and you have a 2dB peak at about 70Hz. See pic below, blue trace.
That's not ideal but it's not too bad and some people may actually like that kind of response. You'll get about 100dB at 1m with 20W before the voice coil starts moving beyond the magnetic gap as long as the driver isn't playing frequencies below about 40Hz - ie. before the driver's xmax of 3mm is exceeded. So loud movies without a sub will not be ok but music without a sub should be fine. A 2" port diameter at that SPL will not see excessive air speed so chuffing shouldn't be a problem.
That's basically all the important stuff you need to look at with a vented box. If any of it seemed like jibberish, ask for clarification.
Now ideally that driver wants about 16L net tuned to 42Hz with a 2" x 6.5" port (pink trace). F3 is about 42Hz and your peaking at 70Hz is now gone. So you're getting more LF extension here and none of it will be louder than the rest of the speaker.
For you, given only about 12.5L, the best you can do for more LF extension is to tune a little lower to about 44Hz with a 2" x 7.5" port (black trace). You lose the peaking again and move F3 a couple of Hz lower.
Personally, I'd probably try the ports you have right now and only consider changing them if you find that the little bit of peaking you get is being perceived as boomy bass.
All sims are with Unibox and based on the driver spec sheet. Real world results could be slightly different.
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Hi jReave. Thank you so much for the insight. Now I'm beginning to understand what all the technical stuff actually meant.Obviously,there's still a long way for me to go before I may be competent enough to fully understand the intrinsics of speaker building.
About the gross internal box volume,is 16x30x29cm only 13.9L? So what would the internal dimensions be to get 16L? I built the boxes like a tower speaker with only the upper part to house the 2 drivers with an adjustable partition inbetween which can be moved to increase or decrease box volume.
You are right about the boominess. It does get a little boomy sometimes. I'll try extending the port length as you recommended.
Thanks alot for explaining the details. Much appreciated.
Volume (in Litres) = L x W x H (in cm) x 0.001
So for eg, 10cm x 10cm x 10cm =1L
For yourself, try 16 x 37 x 29cm = 17.2L , depending on what else is taking up space inside the chamber.
Try a port length of about 20cm to start. That's a tuning of 38Hz and an F3 of 42Hz. Then listen and if you think you want the bass a little louder, shorten the port to about 17.5cm. Listen again and again if you want the lowest frequencies a little louder, shorten to about 15cm. Somewhere in there I think you should find something to your liking.
So for eg, 10cm x 10cm x 10cm =1L
For yourself, try 16 x 37 x 29cm = 17.2L , depending on what else is taking up space inside the chamber.
Try a port length of about 20cm to start. That's a tuning of 38Hz and an F3 of 42Hz. Then listen and if you think you want the bass a little louder, shorten the port to about 17.5cm. Listen again and again if you want the lowest frequencies a little louder, shorten to about 15cm. Somewhere in there I think you should find something to your liking.
jReave! You've been of immense help.Thank you so much for your invaluable assistance in painstakingly explaining these in simple terms. Most appreciated.🙂
About the xmax of 3 mm you mentioned,is that the max this woofer cone should move? Cos,according to the specs the linear coil travel is stated as 6mm.While the max is 19mm. I did some further testing today playing some music with fast deep bass and noticed the cones moving rather violently. Way more 3mm for sure. I immediatedly reduced the volume for fear of damage. Could you explain if this normal please?
About the xmax of 3 mm you mentioned,is that the max this woofer cone should move? Cos,according to the specs the linear coil travel is stated as 6mm.While the max is 19mm. I did some further testing today playing some music with fast deep bass and noticed the cones moving rather violently. Way more 3mm for sure. I immediatedly reduced the volume for fear of damage. Could you explain if this normal please?
There are 3 important limitations to every driver:
1. Xmax - the distance the voice coil can travel without going beyond the top or bottom of the magnet. Understand that if the coil moves outside of the magnetic gap, it is no longer under proper control, so sound quality deteriorates. This is the one most of us around here are most concerned about. If you see linear coil travel listed as "p - p" it means peak to peak so that's xmax times 2.
2. X mechanical - the actual physical limit that the voice coil (and cone) can travel because of the limits of the suspension, ie. the spider and/or the surround. This time if you create enough force with enough power, you may indeed rip the driver apart. Like xmax, x mechanical is 1/2 of the peak to peak limit. So here your driver is safe for peak to peak cone movement of 19mm. This one is more of a concern to max SPL instead of the best sound quality. Note of course for both of the above that cone movement is dependent on frequency - lower notes require more and more cone excursion.
3. Max power - the power limit the voice coil can handle before it is likely to blow up. Usually if you are running LF's thru the driver, xmax is reached way before the power limit so it's not really that important. But say if you are talking about a high passed mid (so a reduction in LF's) in a 3-way, cone excursion will be much reduced and now max power may become more important. A misunderstanding of this rating in particular is a very, very common rookie mistake.
1. Xmax - the distance the voice coil can travel without going beyond the top or bottom of the magnet. Understand that if the coil moves outside of the magnetic gap, it is no longer under proper control, so sound quality deteriorates. This is the one most of us around here are most concerned about. If you see linear coil travel listed as "p - p" it means peak to peak so that's xmax times 2.
2. X mechanical - the actual physical limit that the voice coil (and cone) can travel because of the limits of the suspension, ie. the spider and/or the surround. This time if you create enough force with enough power, you may indeed rip the driver apart. Like xmax, x mechanical is 1/2 of the peak to peak limit. So here your driver is safe for peak to peak cone movement of 19mm. This one is more of a concern to max SPL instead of the best sound quality. Note of course for both of the above that cone movement is dependent on frequency - lower notes require more and more cone excursion.
3. Max power - the power limit the voice coil can handle before it is likely to blow up. Usually if you are running LF's thru the driver, xmax is reached way before the power limit so it's not really that important. But say if you are talking about a high passed mid (so a reduction in LF's) in a 3-way, cone excursion will be much reduced and now max power may become more important. A misunderstanding of this rating in particular is a very, very common rookie mistake.
Thanks again,jReave! So,in my case was I driving the woofer too hard to cause excessive cone excursion? I was just reading something about the woofer "unloading" that could cause such eratic excursions.
Also,when I tried another 6 1/2" Peerless woofer in the same 16x30x29cm enclosure,it didn't seem to have such problems.Pls advise!
Also,when I tried another 6 1/2" Peerless woofer in the same 16x30x29cm enclosure,it didn't seem to have such problems.Pls advise!
So it sounds to me like you were powering the Seas driver beyond xmax but probably within xmech and within max power limits.
Again using Unibox, the Seas will take about 100W in 16L tuned to 42Hz with frequencies above 40Hz (ie. most music) before cone excursion starts to hit about 19mm peak to peak. SPL at 1m should be about 106dB. I somehow doubt you were playing them that loud in a home environment, though I could be wrong and if I am I am going to suggest that you do your ears a favor and turn it down, but otherwise the Seas are robust drivers and I wouldn't worry about it. Look at the max short term power those things can handle - 250W.
Now in terms of sound quality, I don't think you are in the optimum range at those excursion levels but if you are happy with how they sound, who gives a flying leap about technicalities, although as a general rule of thumb I would have to say that all things being equal (which they generally aren't) less cone excursion is to be preferred.
Are the Peerless better? Perhaps. Perhaps not. I can't say without knowing which driver it is and even then that will only be based on the specs. Maybe the Peerless wants a much bigger box in which case cone excursion would be limited by sub optimal box volume. Both Seas and Peerless are both generally known to be very good quality drivers. In this hobby specs are important but in the end subjective opinion is very frequently the final arbiter, ie. which one do you think sounds the best?
Again using Unibox, the Seas will take about 100W in 16L tuned to 42Hz with frequencies above 40Hz (ie. most music) before cone excursion starts to hit about 19mm peak to peak. SPL at 1m should be about 106dB. I somehow doubt you were playing them that loud in a home environment, though I could be wrong and if I am I am going to suggest that you do your ears a favor and turn it down, but otherwise the Seas are robust drivers and I wouldn't worry about it. Look at the max short term power those things can handle - 250W.
Now in terms of sound quality, I don't think you are in the optimum range at those excursion levels but if you are happy with how they sound, who gives a flying leap about technicalities, although as a general rule of thumb I would have to say that all things being equal (which they generally aren't) less cone excursion is to be preferred.
Are the Peerless better? Perhaps. Perhaps not. I can't say without knowing which driver it is and even then that will only be based on the specs. Maybe the Peerless wants a much bigger box in which case cone excursion would be limited by sub optimal box volume. Both Seas and Peerless are both generally known to be very good quality drivers. In this hobby specs are important but in the end subjective opinion is very frequently the final arbiter, ie. which one do you think sounds the best?
Hi jReave!
I've been testing the speakers these few days in the same box and port sizes.I think I've found the reason why the speakers were lacking in performance previously. The Eq setting on the amp had been set to Off. I turned it back On and continued testing with the various frequency bands.Finally settling on the V shape and Smiley face settings.The speakers then came alive.Now the woofers go really deep and the tweeters finally began to sing.
I don't think I turned up the volume too high before. The highest volume level is -20 in my 16 by 22 feet living room. The brief erratic woofer excursions before,could have been caused by a glitch in transmission since I'm streaming you tube music from my tablet to my tv and then out putting to the amp.The woofers cone excursions are now very much controlled.No cone excursion issues since.Except for the occasional boominess.
What other improvement in performance can be expected by increasing the port length and box volume to 16L as you've so painstakingly suggested? Thanks!
I've been testing the speakers these few days in the same box and port sizes.I think I've found the reason why the speakers were lacking in performance previously. The Eq setting on the amp had been set to Off. I turned it back On and continued testing with the various frequency bands.Finally settling on the V shape and Smiley face settings.The speakers then came alive.Now the woofers go really deep and the tweeters finally began to sing.
I don't think I turned up the volume too high before. The highest volume level is -20 in my 16 by 22 feet living room. The brief erratic woofer excursions before,could have been caused by a glitch in transmission since I'm streaming you tube music from my tablet to my tv and then out putting to the amp.The woofers cone excursions are now very much controlled.No cone excursion issues since.Except for the occasional boominess.
What other improvement in performance can be expected by increasing the port length and box volume to 16L as you've so painstakingly suggested? Thanks!
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And another thing to try is temporarily blocking the ports (a bunch of layers of duct tape across the end, if you can remove it without a mess. Or stuff with cloth). See if you prefer the sound.
Yeah, probably. If things sound OK they are probably OK. Loud bass requires moving a lot of air, that's why DJ setups generally have big woofers. A small woofer has to move more for the same sound pressure level (SPL).
For way more information than you may want, here are "Head_Unit’s Rules Of Protection":
1) If when things start to sound distorted or odd you TURN IT DOWN, you are unlikely to ever break anything.
2) If you constantly "turn it up to 11" you will break something.
3) The amp and speaker power ratings do not matter. Don’t bother “matching” the amp and speaker power. That is a seemingly sensible yet actually meaningless exercise, because:
- Speaker specifications are 92% useless (and I say that as a loudspeaker engineer). This is due to different manufacturers measuring the same specs in different ways on different setups.
- Specs for amps are not thorough since they are measured into resistors for pragmatic reasons and speakers are not resistors at all.
4) Amps' 4 ohm or even 2 ohm rating is the most meaningful even if your speakers are 8 ohms. Should be 20-20k Hz, distortion under 1% or it's baloney.
5) For amps "more" power means (IF specs are comparable) at least three times as much due to the logarithmic nature of hearing.
6) You are less likely to damage speakers with a big amp, since let’s face it everyone cranks it up sometime, and a small cheap amp is then more likely to clip and possibly put out DC and ultrasonics (This assumes the speakers are not tiny little pieces of poop).