Open Baffle Questions

[Lazz]

Built speakers before, but never OB. Was thinking about using a 12 or 15 inch coaxial for mid and upper duties or would a 8 to 10 inch be better with 2x15 inch for bass duties. Was thinking about possibly either a Eminence /Selinium / Radian / B&C / Beyma /Paudio or possibly if i can get a Tannoy DC. Wondering what the sound quality is like compared to each other and any other possible contenders. What does the inbuilt cd tweeter compare like to say, a normal tweeter? Was thinking about maybe using the Dayton RS 15's or TC 1000's or Mach 5 audio Maw 15{cheap} or Fi Car audio Q15 for bass. How would two of these per channel in parallel work with the above in regards to sensitivity?I've been comparing a list of woofer comparisons from the cult of ib and the TC's seem to have huge displacement.The design will be based loosely around the Jamo r909,BD design Quasar. Thx. P.S what about this brand http://www.reaudio.com/

[ThomasW]

We have some fairly exhaustive threads dealing with this topic, some date back to early 2003 (Linkwitz launched the Phoenix and we introduced the Arvo Pärt design).

Here are a couple links to get you started. A search will turn up a bunch more.

https://www.htguide.com/forum/showthread.php?t=13074

https://www.htguide.com/forum/showthread.php?t=23598&highlight=Isris

[AJINFLA]

The design will be based loosely around the Jamo r909,BD design Quasar.

The Jamo is passive, with the corresponding complex XO, specialized bass drivers and relatively modest sensitivity. The BD is a HE mid with active (dipole corrected) bass. What route are you taking?
The drivers mentioned tend to suggest the latter. But then, woofer sensitivity is mentioned?
Both require woofers crossing high, narrowing the field significantly.

cheers,

AJ

[Lazz]

More the BD style.I have a range of amplifiers to choose from so was thinking about using active xover or something akin to those lines.Maybe Behringer?

[Lazz]

Also was wondering what would be the difference in using as an example a 8inch coax with say 95db sensitivity as opposed to a 12or15inch coax with 95db sensitivity with the two 15inch woofers for bass.In theory if the spl is the same is it ok to assume that they would sound reasonably similar in output with only a difference in tone due to the actual size.What size would be appropriate in the set up I'm contemplating.Thx.

[Dennis H]

Also was wondering what would be the difference in using as an example a 8inch coax with say 95db sensitivity as opposed to a 12or15inch coax with 95db sensitivity with the two 15inch woofers for bass.In theory if the spl is the same is it ok to assume that they would sound reasonably similar in output with only a difference in tone due to the actual size.What size would be appropriate in the set up I'm contemplating.Thx.

The difference is the crossover frequency. The woofers need a 6dB/octave EQ rolloff because of the open baffle. If the small coax needs to cross an octave higher than the big one, the woofers, and thus the whole system, lose 6dB of sensitivity. Pretty tricky stuff balancing sensitivity and dipole EQ with multiple drivers.

[AJINFLA]

The million dollar question is - can you measure? All this is speculation if you cannot. Even if you use something as flexible as the DCX2496, you must be able to measure.
To expand on what Dennis said, there are a great many differences. The 15" driver will load the tweeter differently vs the 8". The 15" driver will require less excursion (of the waveguide) for the same SPL. The 15" driver will become directional much lower in frequency, leading to dipolar radiation (rather than dipole) lower in frequency, the 15" drivers upper response will require a lower XO to the tweeter, lowering the dipole to monopole transition, etc, etc, etc.

cheers,

AJ

[Lazz]

In pure sound quality terms, would I be better off trying to get a Tannoy dual/con and mating it with the TC 1k's as a start and see how that works out or is there an alternative coax any one can recommend off the shelf or even if I have to mix and match the mid/cd.I,m from Australia and want to try and at least purchase the drivers now from overseas as our xchange rate isn't too bad at the moment.Priced some Eminence beta 8cx here and was quoted $350Aus ea {ouch} .

[dobias]

Wharfedales

I'm planning to have another try at open baffles (OB). I started with Wharfedale speakers back after WWII when it was "Hi-Fi".
When Stereo was marketed, I added a second set of their 12 CS/AL cloth surround full range 12" speaker & their 3" cone tweeter.
I tried a few of G.A.Briggs' speaker enclosure designs without luck. I agreed with his hypothesis that an open baffle would sound better. However, the size of his recommended sand filled baffle (36'w x 30"h) was still insufficient with a single full range woofer. I reverted to smaller enclosures for the wife acceptance factor (WAF)
Recently, I dug my old speakers out of storage & fell in love with them all over.I then searched eBay & found a couple of the Wharfedale 12" cloth surround woofers.
Briggs believed the answer to sufficient bass with an open baffle was the addition of second woofers.
There is very little information about any of these speakers except for resonance & magnet weight.
I have used Briggs' recommended simple capacitor crossover for the 3" tweeters without any crossovers applied to the 12 CS/AL full range speakers. However, I plan on adding crossovers to the additional 12" woofers.
What crossover frequency would be best & what type should I use?
The open baffle I'm planning is going to be made of glass. I'm thinking of from 18"w to 24"w x 30"h with the tweeter pointing up. The glass will be two thicknesses of 1/2" that will be water jet cut to accept the speakers & laminated together. With the back painted black they should be attractive.
This will only be possible because of a friend that has recently obtained a water jet cutter for his bathroom glass business.
I'm sure Briggs would approve of the material.
Is there any helpful advise here for this dinosaur? Please keep the suggestions simple.
Frank

[jdybnis]

Frank,

If you haven't already, take a look at Troels Gravesen's site.

Wharfedale 3" tweeters: http://www.troelsgravesen.dk/super3.htm
High Efficiency Speakers intro: http://www.troelsgravesen.dk/HES.htm
Main page: http://www.troelsgravesen.dk/Diy_Lou...r_Projects.htm

[dobias]

jdybnis,
Thank you very much. I was unaware of this report. I believe he missed the way of using these 3" tweeters that was intended. I remember Briggs wanted the full range speaker to cross over at about 5,000 cps. The simple capacitor was also Briggs' way of avoiding "excessive" manipulation of the sound by a more complex cross over. I think he was an early proponent of the KISS way of engineering.
Frank

[jdybnis]

I think the author of that page understands very well how they were intended to be used. This quote is from another page on the same site:

I have to tell I have a copy of Gilbert Briggs' book Loudspeakers, bought in 1971. This is one of the best books available on loudspeakers and despite several decades old, still tells most of what is important to know in constructing dynamic loudspeakers. Being 19 years old back then, I desperately needed basic information on loudspeakers and this was my speaker bible for many years, and still is today.

I think the important things to take away from that report, if you are going to use that tweeter are:

1. Coat the fabric surround with something that makes a seal. If you can blow through the fabric with a straw it will kill the low end response.

2. Make sure the dust cap has not come loose and is resonating, it will cause a sever dip in the response.

[dobias]

low end of tweeter

By using the tweeter (as intended) above 5,000 cps, it would still be beneficial to coat the surround? I'm not trying to be argumentative, I'm anxious to learn.
Frank

PS: I. too, bought Briggs' book when it was still new and have reread it many times for what I was able to absorb from it.

[jdybnis]

The driver is actually being crossed over at 2.5kHz. That driver is 16ohms, the capacitor starts having an effect at half the frequency than with a typical 8ohm driver.

My first reaction is that I would coat the surround and use a 2nd order crossover. The drop in distortion from reducing the low-end excursion will massively outweigh any detrimental effects of a high quality air-core inductor.

On further consideration I realize that I really don't understand how a 3" upfiring "tweeter" is supposed to work. I would need to see on and off-axis measurements of both drivers in the original enclosure to have an idea of how it is all supposed to work

[Lazz]

Copied this from another thread.https://www.htguide.com/forum/showthread.php?t=26587
Quote:
Originally Posted by Lazz
Thx Jon the Ciare you mentioned looks nice-100.5db spl,fs 29hz is this low enough for open baffle to play deep bass,xmax 7mm is this enough?$210good.These are the specs for the 15" TC 1000's are they simmilar to the 12's you tested from Oz Audio for the Arvo but bigger.Which are the ones to get 4ohm svc or dvc.I should have mentioned I'm thinking of possibly using a 12 or 15" coaxial-something like a Radian or Tannoy DC ,or Cantare 12" havent fully decided yet.


Qts 0.346
Qes 0.381
Qms 3.82
Fs 15.6Hz
Res 3.66Ω
Ls 2.64mH
Lp 3.58mH
Rp 3.16Ω
Dia 320mm
Vas 393l
mms 238g
cms 433um/N
bl 15.0T*m
Spl 87.8dB


Do you guys think the coaxials will have any problems operating open baffle xover at @100hz to use with the Mach 5 woofers.Would the bass from this type of driver have big accurate sound or would they be boomy like in a car type situation.I'm after a deep but accurate sound for listening to a variety of music from modern to Mussorgsky.Perhaps if anyone who's used the TC's or Daytons can chime in.I've noticed some people that have experimented with ob have used cheap bass drivers and reported good results but obviously one doesn't know what level of sq makes them happy.I always believe you must at least start with good drivers to have any chance of quality{I know there's exceptions}.I'm coming from diy Dynaudio wmtmw.But after hearing some Tannoy coaxials was very impressed with the way they had a huge life like potrayal to the music,like being in the auditorium at the time of the performance.I know my Dynaudio's are more accurate in imaging etc but I've listened to many box speakers B&W ,Duntechs etc but they dont have that emotion! I'm looking for.I'm hoping the open baffle will get closer to what i"m looking for.I've heard ob only in the midrange on some commercially available speakers here in Australia and loved the sound.

[Lazz]

Bump.

[Lazz]

Ok guys I think I've narrowed my woofer choice down to either the Dayton RSS390's or the 15"TC Sounds TC1000's x'ing over to a Visaton B200{as a trial}.Which woofers would you guys get? Which ones will play louder down low.Thx.