Two reasons.
1) I was trying to build off of the two way passive OB design to see what could be gained or lost by using an H or U frame.
2) To me, a 20" wide OB is a very attractive size and I think going narrower for a passive set-up is sacrificing bass response. So I was trying to compare what I consider real world high performance design options.
If you want ot use a Goldwood 15" woofer on an OB, take a look at the two versions which have a much higher Qts. They are really not suited to be used in an H or U frame but they are really interesting options for an OB design.
Hi MJK,
I really like the look of your design here, both the aesthetics and your measured performance.
The Goldwood GW-1858 woofers will be in my hands in a week. I'm mating them up with an open baffle pair of MOTH drivers. I already own the MOTH's and wanted to give them a try.
The published specs for the MOTH's are not accurate. GM measured his pair at:
Re= 11.2 ohms
Le= 0.13mH
Fs= 47.3Hz
Qms= 9.6
Qes= 1.23
Qts= 1.09
Sd= 201 cm^2
Vas= 58.5 liters
Cms= 1.03 mm/N
Mms= 11 gramms
Rms= 0.34 kg/s
BxL= 5.42 N/A
SPL= 91dB
Any thoughts regarding the MOTH drivers for the OB portion of this design?
Thank you!
-David
I really like the look of your design here, both the aesthetics and your measured performance.
The Goldwood GW-1858 woofers will be in my hands in a week. I'm mating them up with an open baffle pair of MOTH drivers. I already own the MOTH's and wanted to give them a try.
The published specs for the MOTH's are not accurate. GM measured his pair at:
Re= 11.2 ohms
Le= 0.13mH
Fs= 47.3Hz
Qms= 9.6
Qes= 1.23
Qts= 1.09
Sd= 201 cm^2
Vas= 58.5 liters
Cms= 1.03 mm/N
Mms= 11 gramms
Rms= 0.34 kg/s
BxL= 5.42 N/A
SPL= 91dB
Any thoughts regarding the MOTH drivers for the OB portion of this design?
Thank you!
-David
Attachments
dw8083 said:
Hi,
Well what do want to know ? Qts =1.1 pretty much rules any
sensibly sized box design but is near ideal for a big open baffle.
Some form of aperiodically leaking box well stuffed might work.
Re is very high = an ~ 15 ohm driver.
Xmax linear and mechanical would be nice to know.
http://www.stereophile.com/floorloudspeakers/104moth/index1.html
Fig 4 is PITA to interpret, I wish it was not normalised to on axis.
It does indicate somwhat off-axis will be better, but so might be
on axis and some trap fiters at 2.2 and 10 KHz.
I cannot work out the bass loading.
/sreten.Attachments
I cannot work out the bass loading. edit : Well it does appear
to be vented, exaggerating the upper bad peak and giving
the knee around 30Hz, done for power handling I assume.
I cannot work out why 50Hz tuning increases output down
to 30Hz but not around 50Hz, no expert on high Q tuning.
Shown is very large baffle, sealed and vented.
/sreten.
to be vented, exaggerating the upper bad peak and giving
the knee around 30Hz, done for power handling I assume.
I cannot work out why 50Hz tuning increases output down
to 30Hz but not around 50Hz, no expert on high Q tuning.
Shown is very large baffle, sealed and vented.
/sreten.Attachments
Why not just put the Moth into a 30,000 L box. It sims nicely.
Har har...
I would use the Moth on an Open Baffle or the design that it was made for. I have the plans somewhere... but can't seem to find them. I do like the idea of the Moth on OB with the Goldwoods in H frame. I think it will sound splendid.
Har har...
I would use the Moth on an Open Baffle or the design that it was made for. I have the plans somewhere... but can't seem to find them. I do like the idea of the Moth on OB with the Goldwoods in H frame. I think it will sound splendid.
dw8083 said:Hi MJK,
I really like the look of your design here, both the aesthetics and your measured performance.
The Goldwood GW-1858 woofers will be in my hands in a week. I'm mating them up with an open baffle pair of MOTH drivers. I already own the MOTH's and wanted to give them a try.
The published specs for the MOTH's are not accurate. GM measured his pair at:
Re= 11.2 ohms
Le= 0.13mH
Fs= 47.3Hz
Qms= 9.6
Qes= 1.23
Qts= 1.09
Sd= 201 cm^2
Vas= 58.5 liters
Cms= 1.03 mm/N
Mms= 11 gramms
Rms= 0.34 kg/s
BxL= 5.42 N/A
SPL= 91dB
Any thoughts regarding the MOTH drivers for the OB portion of this design?
Based on those T/S parameters, I think the Moth driver will mate well with the Goldwood H frame. The 91 dB/W/m efficiency is about the same as the Jordan JX92S and the Fostex F120A and FX120 which are all aout 89 dB/W/m. So based on that limited information, I would probably just substitute the Moth driver for the Jordan driver on the same OB and use the active crossover to blend them together. I would use the original 2nd order crossover frequencies and slopes given at the top of Figure 19 in my write up and probably just increase the boost to the H frame form 2.5 dB to 4.5 dB. That would be my starting point and you can then adjust the crossover by ear until the system sounds best in your room.
Godzilla said:
I first looked at building a BIB for the MOTH's. With GM's very considerate and helpful guidance in the MOTH BIB thread, the idea went bust. They need a 9^3ft box and even then did not sim well.
OB seems like the only way to go with the MOTH. I was very excited to read about Martin's H-frame work with the GW-1858. Seemed like a fit.
Nelson says the MOTH's PM6A's sound is very good, but a notch below an actual Lowther PM6A. But hey, with a $1000usd price difference we cannot have everything.
Thank you for your help to steer a noobie in the right direction.
-David
In the prior post I incorrectly stated the MOTH needed a BIB 9^3ft box, but the actual number was 46^3ft!
Moving forward.... My GW1858's arrived this weekend. They are hugh drivers, look impressive and very cool!
I'll start the H-frame GW-1858/OB MOTH build this coming weekend.
-David
Moving forward.... My GW1858's arrived this weekend. They are hugh drivers, look impressive and very cool!
I'll start the H-frame GW-1858/OB MOTH build this coming weekend.
-David
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I had wood cut for my H frames this weekend. The dry fit is perfect! Just need to cut the holes for the drivers. The guy also cut some select pine for my super tweeters. About an hour and $26 well spent IMO. I had a good day at Home Depot. Wifey was misreable. She just wanted to buy a few light bulbs.
I have not been able to work on any projects for several months but now I'm back in business and ready to make sawdust!
I have not been able to work on any projects for several months but now I'm back in business and ready to make sawdust!
moth build
dw8083
if you want guides to router the holes for the moth cicada driver
let me know.
i have one for the frame and one for the hole itself. 1" stock
recommended as a min.
sundbyd@comcast.net
dw8083
if you want guides to router the holes for the moth cicada driver
let me know.
i have one for the frame and one for the hole itself. 1" stock
recommended as a min.
sundbyd@comcast.net
I would really like to try this ob system with an active crossover but have a couple of questions regarding room placement...
I have a fairly small living room and would have to place the rear of the H frame close to the rear wall. If I placed them parallel to the wall the rear would be 8" out from the wall and if I angled them slightly the inside edges would be 8" and the outside would be about 10". Is it a waste of time to have a ob setup that is placed this close to the wall? I am guessing that I might get some unwanted bass peaks. I haven't decided on a mid/hi frequency driver but I like
the idea of using the Goldwood and experimenting with different drivers for the top end.
Next question is; If I use a Behringer DEQ could I equalize this out?
I have a fairly small living room and would have to place the rear of the H frame close to the rear wall. If I placed them parallel to the wall the rear would be 8" out from the wall and if I angled them slightly the inside edges would be 8" and the outside would be about 10". Is it a waste of time to have a ob setup that is placed this close to the wall? I am guessing that I might get some unwanted bass peaks. I haven't decided on a mid/hi frequency driver but I like
the idea of using the Goldwood and experimenting with different drivers for the top end.
Next question is; If I use a Behringer DEQ could I equalize this out?
vaughn said:
That sounds a little close to the rear wall. My room is not that big and I have them just over 2 ft (minimum distance) from the rear wall and rotated towards the listener. I think having them rotated so they are not parallel with the rear wall is very important. You probably want ot be listening to the H frames almost on axis. If they are too close to the rear wall I would be worried about the bass being canceled by the reflected output from the rear of the H frame.
That is a nice feature, in an active system any driver that can be used from 200 Hz up is a likely candidate. You can adjust the relative volume levels so they match using the active crossover.
Not sure I understand the question. I don't know much about the Behringer DEQ but my understanding is that it can be used to EQ away many room generated problems. If you have both the DEQ and the DCX you should have plenty of flexibility for making a wide range of drivers work very well with the H frame woofer in your room.
dublin78 said:
I did get a chance to mount the F120A a few weekends ago, they fit in the same hole as the Jordan but rotated 90 degrees. It is definitely a little brighter driver and more forward, it gives the illusion of more detail. I had to reconfigure the crossover back to the original settings that I had designed for the Jordan which sounds better to my ears. While it is brighter and a bit more detailed I am not sure it is as good in the upper bass and low midrange region, it could be I need to play with the crossover setting some more to get this back. But overall the F120A is a really nice driver.
I pulled them back out to measure the T/S parameters and re mounted the Jordan drivers. After listening to the Jordan drivers again, I am leaning to preferring them over the F120A drivers. The F120A had more high end response but they just did not seem to do as good a job on the midbass. I probably need to swap back again and listen some more.
Both drivers perform really well in the design and my preference is based on a very subtle difference. I can see where other people might prefer the F120A over the Jordan and I could not argue. No clear cut winner just small differences in voicing, either would work well. Hopefully that does not come across as waffling but as two very strong candidates either of which would be satisfying to most listeners.
On another front, I now have passive crossovers designed for the Jordan, the F120A, and the Goldwood H frame which will eliminate the need for bi amping and an active crossover. The price of the components is about the same (~ $180) for either full range driver. I just need to decide which one to build and then order the parts.
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