There's a great new MJK article on baffles and crossovers
focusing on full-range drivers:
http://www.quarter-wave.com/General/
😎
focusing on full-range drivers:
http://www.quarter-wave.com/General/
😎
Link doesn't work, Nelson.
Was this the one you had in mind?
http://www.quarter-wave.com/General/General_Articles.html
/Hugo
Was this the one you had in mind?
http://www.quarter-wave.com/General/General_Articles.html
/Hugo
Very good article, as Martin's usually are.
I'd still go active, but it was very informative and answered a couple of questions I had re OB design.
I'd still go active, but it was very informative and answered a couple of questions I had re OB design.
I wonder if it could be built and then different full range drivers tried on top, as long as they are 8 ohms and about 90db?
I just read that this afternoon. Another excellent treatise,
The graphs showing hoe the driver response, baffle response and XO response all work together to get a flat response are particularily illustrative.
dave
The graphs showing hoe the driver response, baffle response and XO response all work together to get a flat response are particularily illustrative.
dave
Yes, very cool study, as always.
I wonder if it would be possible to use a JX92S instead of the fostex, and so crossover at lower frequencies? That could be a very desirable speaker.
Graham
I wonder if it would be possible to use a JX92S instead of the fostex, and so crossover at lower frequencies? That could be a very desirable speaker.
Graham
britbug said:
The study shows that each combination of mid/tweeter and bass driver needs to be considered together with the baffle as a system, and that changing any drivers requires a reconsideration of all the parameters of the system.
I do expect you would have an easier job of substituting a similar efficiency mid/tweeter. Adapting the sytsem for active XO would give even more flexibility with the mid-tweeter but at nominally higher cost (but when one considers that many diyers have more than a single amp kicking around, it may actually take less cash flow)
dave
Sensitivity of the Jordan is a bit lower at 88db, and the parameters are different, so as Dave says, you'd have to design something for it from the ground up. There's no reason why that's not possible though. I suspect the Jordan would work rather well run on a baffle, with a suitable woofer in support.
Yet another superb paper on design; one of the best available. Actually, I'd call it the best, period, given that Linkwitz's commentaries, superb though they are, have a somewhat different purpose. Thank you, Martin.
Yet another superb paper on design; one of the best available. Actually, I'd call it the best, period, given that Linkwitz's commentaries, superb though they are, have a somewhat different purpose. Thank you, Martin.
Thanks for the positive feedback everybody. I appreciate it. If people walk away with just two concepts, I hope they are as follows.
1) After reading the article the relative efficiency requirement for the woofer with respect to the rest of the system should be clear. In a passive system this means that the woofer probably needs to be at least 6 to 10 dB more efficient, while in an active system this means that additional boost may be be applied to the woofer to help produce this increased efficiency.
2) Another important point is that a Qts value of 1.0 to 1.2 is an advantage for an OB, in particular with respect to baffle size, and does not automatically mean that the response will boom. I have proven this to myself both analytically and with experience gained from the Lowther OB system using two 15" woofers with significantly different Qts values.
Remember, an open baffle speaker is a system and the alignment of the bass is driven by the woofer's Qts, the baffle size and shape, and the low pass crossover. It is really not that difficult to design and get right if you pay attention to the details.
1) After reading the article the relative efficiency requirement for the woofer with respect to the rest of the system should be clear. In a passive system this means that the woofer probably needs to be at least 6 to 10 dB more efficient, while in an active system this means that additional boost may be be applied to the woofer to help produce this increased efficiency.
2) Another important point is that a Qts value of 1.0 to 1.2 is an advantage for an OB, in particular with respect to baffle size, and does not automatically mean that the response will boom. I have proven this to myself both analytically and with experience gained from the Lowther OB system using two 15" woofers with significantly different Qts values.
Remember, an open baffle speaker is a system and the alignment of the bass is driven by the woofer's Qts, the baffle size and shape, and the low pass crossover. It is really not that difficult to design and get right if you pay attention to the details.
Martin,
You make it all sound so simple. I guess it is when someone else has collected all the information and put it in one place.
Thank you!
You make it all sound so simple. I guess it is when someone else has collected all the information and put it in one place.
Thank you!
Yeah, nice paper Martin. Very clear and easy to follow.
The choices you make are well explained and easy to understand.
So you have well achieved your goals #1 & #2. 🙂
The choices you make are well explained and easy to understand.
So you have well achieved your goals #1 & #2. 🙂
Now we hope for the next article, with Nelson Pass fingerprints on it. You may have guessed: An active two way crossover, designed by Nelson Pass. Then, both of the shortcomings that Martin mentions , could be overcome...
I'll tell ya that I have a pair of Eminence Beta 15's and a pair of Visaton B200's. According to Martins article, they won't match very good in a passive configuration due to the high efficiency of the B200 compared to Beta 15. So, I guess I'll need to go active and equalize the Beta...
Greedy boy...
Vix:
I'll tell ya that I have a pair of Eminence Beta 15's and a pair of Visaton B200's. According to Martins article, they won't match very good in a passive configuration due to the high efficiency of the B200 compared to Beta 15. So, I guess I'll need to go active and equalize the Beta...
Greedy boy...
Vix:
Yep. Designed with OB and FR in mind. I have a nice one
now, but it's going through a revision. If you come to RMAF
you can listen to it.
😎
now, but it's going through a revision. If you come to RMAF
you can listen to it.
😎
Yes, good article Martin. It should help those who enjoy OB have the bass that OB deserves. Also, it provides targets for driver modification for OB use, esp considering Qts.
Geoff.
Geoff.
How about putting an L-Pad on the full range speaker, wouldn't that help to tailor the efficiency?
Tom.
Tom.
Sure would. I guess it comes down to how much efficiency are you willing to give away? Maybe I could keep my Lowther's sound but reduce the efficiency to 90 dB/W/m with the correct amount of padding and end up with a smaller baffle. An interesting idea.
- Status
- Not open for further replies.