Fast, fun, Inexpensive OB project

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I tried a few 6.5 and 8 inch that I had on the shelf - even some Saba green cones. Ended up with an old VOM (Phillips?) fullrange. Gave the speakers to a friend when I moved, he still has them and loves them.

Hard to say what to pick without going crazy in cost. I have some FaitalPro drivers that might work - but haven't ever tried them in the Manzie. Others here will certainly have some suggestions.
 
I would suspect that the second GRS might be better used as part of a 2.5 way configuration, low-passing it in at half the existing crossover freq or so. You could also deepen the wings on the bottom GRS. The interaction with OB cancelation would be the focus. Not an utterly simple adventure.

Skip
 
Dual Woofer Manzanita Ultra

Second try.... I did design and build a dual woofer commercial Manzanita Ultra from 2012-2017. Model Manzanita Ultra Plus! It utilized a Seas Prestige 8 inch full range, P/N FA22RCZ. (Seas H1597-08) As Skip Pack discussed in his post, not an easy design to get right. The crossover used 14 component parts. The Ultra Plus performed well, both as an Audiophile and home theater speaker..... but did not sell well primarily due to its size. The Seas 8" is still available from Madisound and others. Will try to post a picture in a separate post. J
 
Sujat.. Your question is a good one... However, there are so many variables... in the pro audio world, power dissipation is quite important... but in a residential hi fi Open baffle application it is of little value. Most open air, lightly loaded woofers can be driven to Xmax with as little as 15 watts. So, as you postulate, the electrical dissipation quoted by the manufacturer means very little in an OB application.
 
Sujat.. Your question is a good one... However, there are so many variables... in the pro audio world, power dissipation is quite important... but in a residential hi fi Open baffle application it is of little value. Most open air, lightly loaded woofers can be driven to Xmax with as little as 15 watts. So, as you postulate, the electrical dissipation quoted by the manufacturer means very little in an OB application.


Thank you for your prompt response, Mr. Busch. I value your insight as well as your considerateness in addressing my question. It does give me a corroborative support to my layman-level understanding.

A further question in this regard -

1. Can the Cms value of a mid-bass driver be of any indication at all as to how much power it may safely handle unloaded or lightly loaded?

2. Can Cms be seen as an independent indicative value of power handling of a bass driver in free air, regardless of the Fs and Sd?

Suppose there r two bass drivers: an 8" with Fs=60 hz and a 12" with Fs=40 hz, both with Cms 0.8 & Qts=0.68 In such case what could be the likely mechanical power handling for each of these drivers unloaded?

I hope my question is reasonable. I eagerly look forward to gaining some idea that i can take as a workable premise to base judgement upon.

Thanks in advance.... :)
 
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Sujat.... free air power limits can be difficult to predict... If for example your 8" is a very high Xmax sub woofer with say 12 mm peak excursion, (very low efficiency) and the 12" has a small 4 mm peak excursion, (fairly high efficiency relative to the 8") the 8" will take several times the power before going non-linear at F/S. Maybe as much as 75 or more watts. The 12" may reach its Xmax at F/S with just 12-15 watts. I am making several assumptions here, but you get the idea. Add in the variable of loading based on the effective size of an Open Baffle, the estimate above could vary quite a bit based on the loading the baffle actually provides. Hope this make some sense. J
 
An unloaded driver is not power limited, its excursion limited. There is little point looking at power handling. Driver will hit xmax much before hitting power limit. Frequently Asked Questions

Thanks, wonderfulaudio. Yes, i do get the idea. I did mean the excursion.... i used the wrong term.

As Mr. Linkwitz clarifies, at its Fs a 12" driver may reach full excursion when driven with just 5+ watts on an open baffle. * Does it really mean you can drive it with no more than say 7-8 watts until destruction when used in an OB design?!

It appears confusing, because by reasonable logic then, Jamo R907s using two 12" drivers should be driven to full excursion with no more than 20 watts, even if we consider a fair buffer for a possibly different set of variables; yet they quote their long term power handling at about 200 watts. How can they work beyond their full excursion limits then? It does appear quite contradictory to my layman level understanding.

Could u please shed some light here?
 
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Sujat.... free air power limits can be difficult to predict... If for example your 8" is a very high Xmax sub woofer with say 12 mm peak excursion, (very low efficiency) and the 12" has a small 4 mm peak excursion, (fairly high efficiency relative to the 8") the 8" will take several times the power before going non-linear at F/S. Maybe as much as 75 or more watts. The 12" may reach its Xmax at F/S with just 12-15 watts. I am making several assumptions here, but you get the idea. Add in the variable of loading based on the effective size of an Open Baffle, the estimate above could vary quite a bit based on the loading the baffle actually provides. Hope this make some sense. J


Yes, Mr. Busch, i do get what you have explained. Thank u. :)
 
It appears confusing, because by reasonable logic then, Jamo R907s using two 12" drivers should be driven to full excursion with no more than 20 watts, even if we consider a fair buffer for a possibly different set of variables; yet they quote their long term power handling at about 200 watts. How can they work beyond their full excursion limits then? It does appear quite contradictory to my layman level understanding.

Could u please shed some light here?

Ask them, most probably you wont get a reply. I think we need not take marketing figures seriously.
 
Jamo OB power rating

Sujat: As for Jamo and power rating(s) ... Being a three way and assuming HI-FI and NOT pro-audio use, the 200 watt rating is understandable. This is a maximum transient value. True max continuous value is in the 20-30 watt area. Also, once the woofers go non linear, their efficiency rapidly drops.. so it takes more and more power to drive them to their X-limit value. Suspect on the Jamo that would be somewhere around 12-15 mm peak on the woofer pair. Plus somewhere around 30% or more of that 200 watt max is directed at the midrange and tweeter with most music. Plus some crossover losses to boot.
 
Sujat: As for Jamo and power rating(s) ... Being a three way and assuming HI-FI and NOT pro-audio use, the 200 watt rating is understandable. This is a maximum transient value. True max continuous value is in the 20-30 watt area. Also, once the woofers go non linear, their efficiency rapidly drops.. so it takes more and more power to drive them to their X-limit value. Suspect on the Jamo that would be somewhere around 12-15 mm peak on the woofer pair. Plus somewhere around 30% or more of that 200 watt max is directed at the midrange and tweeter with most music. Plus some crossover losses to boot.



Thank you, Mr. Busch! I find your explanation well appealing even to my layman-level logic and understanding!

I just revisited their webpage, and i stand corrected about their claims: long term power handling = 350 watts(!); short term (transients) = 500 watts.

Jamo.com | R 907

I suppose they must have engineered these 12" woofers specifically for such extreme application - as you state.... extremely long stroke, and probably an extremely low Cms value too.

Thanks for your inputs. :)
 
Sujat.... free air power limits can be difficult to predict... If for example your 8" is a very high Xmax sub woofer with say 12 mm peak excursion, (very low efficiency) and the 12" has a small 4 mm peak excursion, (fairly high efficiency relative to the 8") the 8" will take several times the power before going non-linear at F/S. Maybe as much as 75 or more watts. The 12" may reach its Xmax at F/S with just 12-15 watts. I am making several assumptions here, but you get the idea. Add in the variable of loading based on the effective size of an Open Baffle, the estimate above could vary quite a bit based on the loading the baffle actually provides. Hope this make some sense. J



Mr. Busch, may i reframe my question a bit differently, in case it may facilitate a numerical answer (in rough indicative estimates for guidance, of course) ? I cannot expect definitive values, nor does it involve any legal responsibility for anybody!

Is there a set of criteria (eg: Cms, etc.) that i should look for in an 87 dB/watt/metre sensitive 8" midbass driver to suit an open baffle (or probably a very lightly loaded.... Vb=Vas*4 sized sealed enclosure) given i should need to feed it with up to 20 watts and yet remain well within its excursion limits? I aim for a max. SPL of 99-100 dB at 1 metre.

Even an approximate set of values should be of great help to me in extrapolating a bit and eventually work my way to reach the desired target!

Thanks and regards,
Sujat
 
Sujat: I need to make way too many assumptions to provide a meaningful answer. Ultimate system efficiency and effective low frequency cut off for an O.B. system are largely determined by the baffle dimensions and configuration. So.... can you advise what you have in mind in those two areas? Once that is known, you can start to look for your 8" driver. This assumes of course there is a driver available that can work within your design goals. J