Hi everyone,
the 15" eminence beta drivers were happy in a OB and now I'd like to try them in a sealed enclosure. The problem I am having is for a flat response the Vas I get is ~600 L and the recommended volume in the spreadsheet is 45-62 L. If I go with a higher damping factor I can have a smaller box, but how will this influence the sound? What volume would be a good tradeoff?
to follow my steps:
decided on a Qtc = 0.707 for a flat response
Qts = 0.58
Vas = 334 L
Volume of the box (Vb):
Vb = Vas / (( Qtc/Qts )^2 - 1)
Vb = 334 L/ (( 0.707 / 0.58 )^2 -1)
Vb = 687 L
If I turn it around, for a Vb of 62 L what damping factor is needed?
Qtc = Qts sqrt(Vas/Vb)+1)
Qtc = 1.47
A higher Qtc, will mean a smaller volume and a happier wife, but the frequency response will not be flat. Is that all there is to it here? I've been reading on the web about boxy sound etc. but can't find any good resource where these things are explained. found this link below quite useful, but it also doesn't go into explaining why the sound is worse. the example for a ported box:
" A ported enclosure will produce louder deeper bass at the expense of sound quality." Speaker Box Enclosure Designer / Calculator Help
any advice and help is welcome 🙂 I can also just try it and go with the max size acceptable for the space we have ~120L and hope for the best 😀 If the speakers are not suitable for a sealed box, would be also interesting to hear before I start building sth that should not be built 🙂
Thanks,
Martin
the 15" eminence beta drivers were happy in a OB and now I'd like to try them in a sealed enclosure. The problem I am having is for a flat response the Vas I get is ~600 L and the recommended volume in the spreadsheet is 45-62 L. If I go with a higher damping factor I can have a smaller box, but how will this influence the sound? What volume would be a good tradeoff?
to follow my steps:
decided on a Qtc = 0.707 for a flat response
Qts = 0.58
Vas = 334 L
Volume of the box (Vb):
Vb = Vas / (( Qtc/Qts )^2 - 1)
Vb = 334 L/ (( 0.707 / 0.58 )^2 -1)
Vb = 687 L
If I turn it around, for a Vb of 62 L what damping factor is needed?
Qtc = Qts sqrt(Vas/Vb)+1)
Qtc = 1.47
A higher Qtc, will mean a smaller volume and a happier wife, but the frequency response will not be flat. Is that all there is to it here? I've been reading on the web about boxy sound etc. but can't find any good resource where these things are explained. found this link below quite useful, but it also doesn't go into explaining why the sound is worse. the example for a ported box:
" A ported enclosure will produce louder deeper bass at the expense of sound quality." Speaker Box Enclosure Designer / Calculator Help
any advice and help is welcome 🙂 I can also just try it and go with the max size acceptable for the space we have ~120L and hope for the best 😀 If the speakers are not suitable for a sealed box, would be also interesting to hear before I start building sth that should not be built 🙂
Thanks,
Martin
Yes and you can easily correct that with a Linkwitz Transform circuit. Oh and it will have a slightly lower efficiency below the resonance frequency. Not likely to be a problem with a 15" woofer I think. 😀
If you want to do it properly, you can also take into account what the room does to the response. Build the subwoofer, measure it in your room and use the parametric EQ on a DSP to make the response flat.
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great 🙂 thank you for the reply 🙂
I did play with the miniDSP some time ago for the OB crossover (Mark Audio Alpair 7.3 for mid-high, Eminence beta 15" for the low), but the sound quality was not that great, lost lots of details. So I tried with the miniDigi to avoid one DAC->ADC step, that was somewhat better, but still not what I had with the Alpairs in a Pensil enclosure.
Once I was happy with the crossover I built a passive crossover and the details were back.
ok, then it's time to try the 15" in a sealed box 😀
I did play with the miniDSP some time ago for the OB crossover (Mark Audio Alpair 7.3 for mid-high, Eminence beta 15" for the low), but the sound quality was not that great, lost lots of details. So I tried with the miniDigi to avoid one DAC->ADC step, that was somewhat better, but still not what I had with the Alpairs in a Pensil enclosure.
Once I was happy with the crossover I built a passive crossover and the details were back.
ok, then it's time to try the 15" in a sealed box 😀
Have you calculated EBP?
Is the speaker suitable for sealed box ?
Sealed or Ported Speaker Box Enclosure Calculator
Is the speaker suitable for sealed box ?
Sealed or Ported Speaker Box Enclosure Calculator
All woofers work in a sealed box. If EBP is high it just means that it won't produce much bass relative to midrange in a sealed box. In that case a ported box would be better if the goal is to obtain a flat response down to bass frequencies, though another way to get to that flat response is using an equalizer. 🙂
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Anything a small box can do, a big box can do better.
Can you honestly say you tested DSP blind and fairly*? A lot of us can't understand the griping.... reminiscent of complaints about CDs.
"DSP" can mean EQ and lots of time tricks and/or Xover (hence, bi-amp).
But, TBTL is right. Just build it (big enough and covered in nice wood veneer) and then see the dramatic influence of your room. Then EQ, because we ALWAYS have to. That's the way a guy who tried OBs would do it.
Pity the acoustic forum is hidden away elsewhere.
B.
*fair A/B testing requires quite precise FR matching across the whole freq compass before starting the shoot-out.
Can you honestly say you tested DSP blind and fairly*? A lot of us can't understand the griping.... reminiscent of complaints about CDs.
"DSP" can mean EQ and lots of time tricks and/or Xover (hence, bi-amp).
But, TBTL is right. Just build it (big enough and covered in nice wood veneer) and then see the dramatic influence of your room. Then EQ, because we ALWAYS have to. That's the way a guy who tried OBs would do it.
Pity the acoustic forum is hidden away elsewhere.
B.
*fair A/B testing requires quite precise FR matching across the whole freq compass before starting the shoot-out.
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academia50:
yes, it's 55, the speaker is on the far end of sealed leaning to vented
TBTL: yes EQ 🙂 doing an active crossover is somewhere down the road
bentoronto:I think DSPs are great, being able to modify the sound in the digital domain is a huge advantage and offers a lot of flexibility.
I've tested the miniDSP in a non objective way with their UMIK-1 microphone. Tried the calibration from the factory and the calibration files from the webpage I bought it from. The calibrations differed more than I expected. It was great to try different crossovers which would be expensive and tedious in the analog world. Had great fun with it.
I am just saying that in my hands the sound was more rich and detailed to my ears with a passive crossover then what I could muster up with the miniDSP. I have to be honest here, I didn't go into any phase delays or all the tricks the DSP can do, just crossover and I tried some EQ for smoothing the frequency response with parameters estimated in REW.
I actually wanted to use the miniDSP as a crossover and make use of the EQ, but I don't have a 4 channel DAC and amplifier.
Maybe it's time to give DSPs another try. Which DSP are you using and are you happy with it?
yes, it's 55, the speaker is on the far end of sealed leaning to vented
TBTL: yes EQ 🙂 doing an active crossover is somewhere down the road
bentoronto:I think DSPs are great, being able to modify the sound in the digital domain is a huge advantage and offers a lot of flexibility.
I've tested the miniDSP in a non objective way with their UMIK-1 microphone. Tried the calibration from the factory and the calibration files from the webpage I bought it from. The calibrations differed more than I expected. It was great to try different crossovers which would be expensive and tedious in the analog world. Had great fun with it.
I am just saying that in my hands the sound was more rich and detailed to my ears with a passive crossover then what I could muster up with the miniDSP. I have to be honest here, I didn't go into any phase delays or all the tricks the DSP can do, just crossover and I tried some EQ for smoothing the frequency response with parameters estimated in REW.
I actually wanted to use the miniDSP as a crossover and make use of the EQ, but I don't have a 4 channel DAC and amplifier.
Maybe it's time to give DSPs another try. Which DSP are you using and are you happy with it?
You are the very soul of judicious thinking.
I and thousands of ecstatic other users and for more than a decade use the Behringer DCX2496, all-singing all-dancing DSP. It may also be Number One on the golden-ear DSP criticism list. You can input with SPDIF coax from an inexpensive USB converter or 3 channels of base-band audio and it outputs in 6 channels of audio.
Cheap and easy to sell if you tire of it.
B.
An EBP of 55 is more apt for sealed, but in the extreme is my project (postponed), Eminence DeltaPro 18 A with EBP 84 ..........
This number if it reveals that it is almost at the limit to use as sealed, so much so that Eminence indicates that it is not applicable .....
So, I do not share that any speaker is suitable for sealed or vented and it only depends on the box, ( tbtl dixit )I think it depends on the range of working frequencies that we want to reproduce. Some speakers will do it much better than others...
I share 100% this statement, it is easily verifiable with a simulation program like Win ISD or Horn Resp.
It is easier for me to use the first one even if I only manage a few digits of resolution, for me it is more than enough...😉
......at the other extreme is my ....
Oh, why did Esperanto not become universal?
It will have something to do with "divide and reign" ?
Oh, porqué no se hizo universal el Esperanto ?
Tendra algo que ver con " divide y reinarás " ?
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thanks for sharing the info 🙂 ah, the DSP has no RCA connectors, would need to make my signal balanced first, but this could be also a fun project 🙂
converting unbalanced to balanced signal: found a link to Jensen posted by AndrewT a while ago...
http://www.jensen-transformers.com/wp-content/uploads/2014/08/an003.pdf
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Nice to see you investigating.
Yes, the Behringer has XLR (AKA Cannon) connectors (a good pro standard). But is designed to work unbalanced too. For a couple of dollars, you just buy inexpensive XLR-to-RCA plugs (2 male connectors for input* and as many females for output as you need and if you buy cheap ones, a spare or two). That's it.
I don't think there's reason to follow LordSansui's links when using just home cable lengths. The Behringer has input and output adjustments (and every conceivable other control) for gain management tasks.
B.
*if you are inputting with SPDIF/AES coax (which cleverly skips the Behringer input ADC) you only need one male which goes to Input C.
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Attachments
Excellent link, it has taken me a while to read it completely because Google Translator does not work directly on PDF files. I must copy and paste then .. (for paragraphs, quite laborious, but it works)
Thanks for the contribution. To clarify the concepts of balanced-unbalanced signals ...🙂
Im wondering how Alpha 15A would work in ridiculously small sealed.
For example: 25-30L (or volume that will lead to 80-120Hz F3) and DE250 in horn above it.
Goal: Hight qtc, punchy LCR speakers with natural* rising/Harman curve and AVR XO dialed at F3, so overall slope would be 24db/oct (AVR highpass is usually 12db if remember correctly)
I already have Alpha 15A´s and DE250 & horns. It would be nice to have dynamic and shallow LCR set paired with sealed 18" sub.
*By natural I mean that no eq should be needed to get rising reponse towards low freqs, small enclosure and high qtc will lead to that.
For example: 25-30L (or volume that will lead to 80-120Hz F3) and DE250 in horn above it.
Goal: Hight qtc, punchy LCR speakers with natural* rising/Harman curve and AVR XO dialed at F3, so overall slope would be 24db/oct (AVR highpass is usually 12db if remember correctly)
I already have Alpha 15A´s and DE250 & horns. It would be nice to have dynamic and shallow LCR set paired with sealed 18" sub.
*By natural I mean that no eq should be needed to get rising reponse towards low freqs, small enclosure and high qtc will lead to that.