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18" subwoofer or not?
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Xoc1 View Drop Down
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Points: 364 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Xoc1 Quote  Post ReplyReply Direct Link To This Post Posted: 04 July 2022 at 10:27pm
So if the amp is the

GM-D8704 4-channel amplifier

It can be bridged to 2 channels
300 W x 2-Channel - 4 Ohm Bridged
So with 2 x 8Ω per channel parallel to make 4 ohm they should get 150W each. 600 rms total.
A single speaker would need a different amp as you would only get 200w @ 8Ω
or 300w @ 4R.

You have not said what drivers you are using but if they are decent I don't think what you have got is far from optimal. the Tham 12 responds well to being used in quads. As a single they are about 98 db at the bottom of their passband but seem to gain 11 db in a quad.
A SS15 might be 100 102 db /W but only gain 10db In a quad.
4 X TH18 would not be louder than the 4 X SS15's but would have more bandwidth in a quad, so you would spend a lot for little gain.
Obviously the bigger speakers would spank your little boxes, but only when given the power that they can handle.
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Jack1991 View Drop Down
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Points: 461 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack1991 Quote  Post ReplyReply Direct Link To This Post Posted: 05 July 2022 at 7:41am
It is that amplifier yes, but 2 channels are for the subs and the other 2 is, 1 for the mids, and 1 for the tops. But what i was thinking is if i had 1 sub box i could use 2 channels for that and then the other 2 channels for just a single mid top.

Cheers for all the info though man, i think ill just stick with the Thams then. Its only a small 12v system which is surprisingly plenty loud enough for what ill ever use it for. Im more just getting the itch to build something again to be honest, something bigger that looked a bit more meaty.

The drivers in the Tham12s are only Thomann 12-280-W as i dont need big power so they are fine for it.


Edited by Jack1991 - 05 July 2022 at 7:48am
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Xoc1 View Drop Down
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Points: 364 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Xoc1 Quote  Post ReplyReply Direct Link To This Post Posted: 05 July 2022 at 9:51pm
The Thomann 12-280-W has no published speaker parameters. But I found some user generated ones that could be used in Hornresp.
My suggestion to you is to get another amplifier to run the mid tops separately. Then you should get a decent output from the 4 Tham 12s as you could run 150w rms each cab.
If you could run a proper crossover with a high pass than even better. Maybe a

t.racks DSP 4x4 Mini would be a reasonable 12V digital crossover? Sim is unfiltered 4 X 12 -280/W at 150W each and a suitable high pass filter.
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Points: 1162 		Post Options Post Options   Thanks (0) Thanks(0)   Quote APW Quote  Post ReplyReply Direct Link To This Post Posted: 06 July 2022 at 8:41am
Originally posted by Xoc1 Xoc1 wrote:

The Thomann 12-280-W has no published speaker parameters.....


From the data sheet:
Re: 6.6r
Fe: 36.035Hz
Sd: 51.071m
Md: 56.900g
Bl: 20.681T
Qms: 5.137
Qes: 0.316
Qts: 0.304
No: 1.274%
Spl: 93.1dB
Vas:75.663Ltr
Cms: 204.291u M/N
Krm: 4.949m Ohm
Erm: 0.867
Mms: 85.706m Kg
Mmd: 79.070m Kg
Kxm: 44.11m H
Exm: 0.716


Edited by APW - 06 July 2022 at 8:51am
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Jack1991 View Drop Down
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Points: 461 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack1991 Quote  Post ReplyReply Direct Link To This Post Posted: 06 July 2022 at 2:30pm
Going to bin this idea now then and stick with the Thams. Thanks for all the advice and help though people 👍🏼

Out of interest though Xoc1, i have a T.racks 4x4 dsp mini which i use for it all. But if i was to get another amplifier say a 2 channel amplifier, 1 for mids, 1 for tops. I wouldnt be able to link that through the same dsp would I? As each channel on the amp requires a channel of the dsp? Or would i just have to use a rca splitter?

Also do you have a good reccomendation for a high pass for the thams?


Edited by Jack1991 - 06 July 2022 at 2:40pm
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DMorison View Drop Down
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Originally posted by Jack1991 Jack1991 wrote:

Out of interest though Xoc1, i have a T.racks 4x4 dsp mini which i use for it all. But if i was to get another amplifier say a 2 channel amplifier, 1 for mids, 1 for tops. I wouldnt be able to link that through the same dsp would I? As each channel on the amp requires a channel of the dsp? Or would i just have to use a rca splitter?

If you're running mono, then you'd only need one channel of the DSP for however many channels of amp are feeding the bass section, one for the mids and one for the highs, so that would take up 3 (or 4 if you have a 4 way rig).
You would need to put a splitter on the bass output of the DSP if you were feeding that to multiple amp channels, or use amps that have pass-through connections already.
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Jack1991 View Drop Down
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Originally posted by DMorison DMorison wrote:

If you're running mono, then you'd only need one channel of the DSP for however many channels of amp are feeding the bass section, one for the mids and one for the highs, so that would take up 3 (or 4 if you have a 4 way rig).
You would need to put a splitter on the bass output of the DSP if you were feeding that to multiple amp channels, or use amps that have pass-through connections already.

Ahh right ok cool yeh that makes sense then. Not sure how id connect it though.



So yeh because my amp is a 4 channel, it has 1x rca input for each channel. So if 2x channels were bridged for 2x subs. Then the other 2x channels bridged for the other 2 subs. But all running the same frequency etc then im not sure how id connect that?

The DSP inputs/outputs are all 1/4" jack. 

Or do you mean literally just 1 output of the dsp, to 1 input of the amp. That would do even if 2x channels are bridged?


Edited by Jack1991 - 06 July 2022 at 3:23pm
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Points: 1617 		Post Options Post Options   Thanks (0) Thanks(0)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 06 July 2022 at 8:11pm
The amp's manual should explain how to connect it up in the various operating modes it offers, but you may well need adapters or a custom cable to convert the balanced TRS output of the DSP to unbalanced RCQ to match the amp's inputs.
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Xoc1 View Drop Down
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RCA input jack A
For two-channel output, connect the RCA
plugs to the RCA input jack A with RCA pin plugs
 INPUT SELECT (input select) switch (2CH position)

So just connect the LF outputs from the DSP to the GM-D8704, A inputs, throw the switch to 2 channel. Wire the Thams in parallel pairs (4 ohm loads) to the 2 bridge amp outputs - Its all in the Manual. RTFM

Plug the DSP HF Outputs from the DSP thru a separate Amp.into the mid tops & I think you have a cost effective upgrade.
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jacethebase View Drop Down
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Points: 5690 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jacethebase Quote  Post ReplyReply Direct Link To This Post Posted: 06 July 2022 at 10:31pm
I have said it before and I will say it again.

There is no replacement for displacement!
www.wedding-production.co.uk

www.stage2sound.com
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Jack1991 View Drop Down
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Points: 461 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Jack1991 Quote  Post ReplyReply Direct Link To This Post Posted: 07 July 2022 at 8:23am
Cool, cheers guys thanks for the help. And yeh sorry man will RTFM in future, my bad. 

Edited by Jack1991 - 07 July 2022 at 8:23am
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fsp View Drop Down
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Points: 2 		Post Options Post Options   Thanks (0) Thanks(0)   Quote fsp Quote  Post ReplyReply Direct Link To This Post Posted: 19 August 2022 at 9:33am
yes of course , why not ?
get a lot of 18 inch you can afford,,you life young just once so do best you can do
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