Otop 8

High power and fidelity from an easy to build cabinet.
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jklomp
Posts: 6
Joined: Fri Jun 05, 2020 1:55 am

Re: Otop 8

#16 Post by jklomp »

I am going to build these for the 100-500Hz spectrum. So I don't need the tweeters. Do I still need some timber in the middle to complete the horn?

Grant Bunter
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Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
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Re: Otop 8

#17 Post by Grant Bunter »

jklomp wrote: Sat Jun 06, 2020 2:10 am I am going to build these for the 100-500Hz spectrum. So I don't need the tweeters. Do I still need some timber in the middle to complete the horn?
Hello and welcome to the forum :)
You’re planning to use these as kick bins?
What’s subs and tops are they going with ?
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

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Bill Fitzmaurice
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Joined: Tue May 02, 2006 5:59 pm

Re: Otop 8

#18 Post by Bill Fitzmaurice »

I'd say that chances are this is the wrong cab for the job you intend it for.

jklomp
Posts: 6
Joined: Fri Jun 05, 2020 1:55 am

Re: Otop 8

#19 Post by jklomp »

Hi Bill,

I will build them to replace 2 acoustic boxes in my "stereo" that can't keep up with the Tuba HT and the mid and high arrays. All I am after is about 6Db more from the same 8" speakers. So will they need something in the mouth in place of the tweeters, or will they perform without that?

Grant Bunter
Posts: 6700
Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
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Re: Otop 8

#20 Post by Grant Bunter »

jklomp wrote: Wed Jun 10, 2020 12:00 am Hi Bill,

I will build them to replace 2 acoustic boxes in my "stereo" that can't keep up with the Tuba HT and the mid and high arrays. All I am after is about 6Db more from the same 8" speakers. So will they need something in the mouth in place of the tweeters, or will they perform without that?
What are the 8 inch speakers?
If they’re not recommended drivers, or fit the required TS parameters, then you don’t get the response in the charts from the cab...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

jklomp
Posts: 6
Joined: Fri Jun 05, 2020 1:55 am

Re: Otop 8

#21 Post by jklomp »

Hi Guys,

I asked a simple question and all I am getting back is questions. I am perfectly happy to destroy 2 sheets of ply to see if it will solve my problem. Covid gives me plenty of time. So the question was: Do I need to add some timber in the middle instead of the tweeters so the mouth dimensions stay the same, or can I omit that. Thanks.

Grant Bunter
Posts: 6700
Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
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Re: Otop 8

#22 Post by Grant Bunter »

Bruce put it better...
Last edited by Grant Bunter on Sat Jun 13, 2020 4:16 pm, edited 1 time in total.
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

Bruce Weldy
Posts: 8007
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Otop 8

#23 Post by Bruce Weldy »

jklomp wrote: Sat Jun 13, 2020 1:22 am Hi Guys,

I asked a simple question and all I am getting back is questions. I am perfectly happy to destroy 2 sheets of ply to see if it will solve my problem. Covid gives me plenty of time. So the question was: Do I need to add some timber in the middle instead of the tweeters so the mouth dimensions stay the same, or can I omit that. Thanks.
The reason for the questions is the same reason that you'd want more info if your 4 year old came and ask if you had a 20 foot ladder. The question itself raises a lot of questions. Everyone is just trying to help - because it seems, based on the little information, that you might be building the wrong box.

So, the answer is no - the tweeter array isn't integral to the stability of the box.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

jklomp
Posts: 6
Joined: Fri Jun 05, 2020 1:55 am

Re: Otop 8

#24 Post by jklomp »

Thanks Guys,

I will give a full report once I have 'destroyed' my ply and done all the measurements.

jklomp
Posts: 6
Joined: Fri Jun 05, 2020 1:55 am

Re: Otop 8

#25 Post by jklomp »

Hi Guys,

Otops built and tested.

See attachments. I did mostly get my 6Db and as an added bonus, a flat phase response in the target frequency band. The Otop is a bit lumpier in the response, but nothing APO equalizer can't fix. Measurements are 1W/1Meter (2.0volt rms). Being winter here I had to do it indoors, so some of the lumps and bumps may be the room. But they are worth painting and keeping!
Attachments
Omnitop spl and phase.jpg
Sealed spl and phase.jpg

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J_Dunavin
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Joined: Sun Jul 09, 2006 3:13 pm
Location: Appleton WI
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Re: Otop 8

#26 Post by J_Dunavin »

What drivers did you use here?
Good info though as I’m considering building a set
2 - OTop8
2 - T39
8 - DR200
2 - DR250
9 - T24
6 - T45
1 - Auto Tuba

jklomp
Posts: 6
Joined: Fri Jun 05, 2020 1:55 am

Re: Otop 8

#27 Post by jklomp »

The acoustic box are Dayton Hifi woofers. The Otop are cheap Chinese speakers, 250W rms. The measured SPL of the speakers is the same. But the Dayton's would not be suitable for this enclosure. Even the cheap speakers are marginally suitable, but you can see the results. The Dayton Audio PA200-8 would be better, at least 3Db more and probably flatter response. Fairly cheap in the US. Measured properties of the Chinese speakers attached. Measured after a night on 50Hz and cooled down again.
Attachments
speaker 4 tsp.jpg
speaker 4 180620.jpg

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MarcBass
Posts: 108
Joined: Thu Feb 23, 2012 6:41 pm
Location: Toowoomba, Qld, Australia

Re: Otop 8

#28 Post by MarcBass »

These poor Otop 8's don't seem to have had a lot of uptake.

I have some delta 8's and some beta 8's laying around idle and the profile of this build would work quite nicely for a couple of venues & events I have lined up. Hence, I have been collecting parts for a while and am almost ready to start building.

I have a question about power requirements for the Otop 8. I intend to build 4 boxes each wired to 16 ohms. What is the ideal amp size to run a single 16 ohm unit with and to run an 8 ohm combination of two 16 ohm boxes with?
Built:
2 T39 24 inch 3012LF
2 W8 melded array Fane Sovereign 8-225 loaded
2 W8 flat array Delta Pro 8
2 Omni 12 (2*10 BP102) TallBoy
2 SLA pro 4x6

Bought:
2 OT12's 3012 / NSD


Next Build: 2 SLA pro 2x6

Grant Bunter
Posts: 6700
Joined: Mon Nov 28, 2011 11:12 am
Location: Ilfracombe Queensland Australia
Contact:

Re: Otop 8

#29 Post by Grant Bunter »

MarcBass wrote: Thu Feb 18, 2021 10:38 pm These poor Otop 8's don't seem to have had a lot of uptake.

I have some delta 8's and some beta 8's laying around idle and the profile of this build would work quite nicely for a couple of venues & events I have lined up. Hence, I have been collecting parts for a while and am almost ready to start building.

I have a question about power requirements for the Otop 8. I intend to build 4 boxes each wired to 16 ohms. What is the ideal amp size to run a single 16 ohm unit with and to run an 8 ohm combination of two 16 ohm boxes with?
G'day Marc,
Long time no see here in the forum, so welcome back.
Hope everything's going good over on the coast.

I don't have the plans, but I know from the WH8 plans that the beta 8a will take about 60W (22V/8 ohms) at 100Hz before it reaches Xmax in that cab.
I wouldn't think it would be remarkably different in the Otop8 with the exception that wired in series, power handling is doubled.
So, 1 cab a side or 2 (in parallel) shouldn't matter at all (amps don't like low impedance loads, but should handle a 16 ohm load just fine, even if not specced), 300W/8ohms/channel should be more than enough, throw in some headroom as well...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 6 with melded array wired series/parallel.
Bunter's Audio and Lighting "like"s would be most appreciated...

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MarcBass
Posts: 108
Joined: Thu Feb 23, 2012 6:41 pm
Location: Toowoomba, Qld, Australia

Re: Otop 8

#30 Post by MarcBass »

Thanks Grant,

Yes, I should have thought W8 for running specs.

If I can get my act together I'll test them out at the May Day march in town and post a review.

(BTW: Closer to the coast than you are, but still west of the range.)

Cheers

Marc
Built:
2 T39 24 inch 3012LF
2 W8 melded array Fane Sovereign 8-225 loaded
2 W8 flat array Delta Pro 8
2 Omni 12 (2*10 BP102) TallBoy
2 SLA pro 4x6

Bought:
2 OT12's 3012 / NSD


Next Build: 2 SLA pro 2x6

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