Review: Denon DJ Prime 4 (Standalone DJ Controller)

This review comes fairly late in the life of the Prime 4, but when I was shopping I couldn't find many reviews that covered actual usage of the device in the way I was going to use it. I've been DJing for a good while now, and I started feeling some limits of 2 channels and the relatively small footprint of Pioneer's DDJ-FLX4. For me, DJ hardware comes in 2 price ranges: really accessible great value for money (DDJ-FLX4 is definitely there), and extremely expensive wallet melting (most things with 4 channels).

I ended up browsing Facebook Marketplace and eventually found a deal I couldn't pass up. The listing said it came with a Denon Prime 4, a Magma flight case, and a 2TB internal SSD... for $1,200. While this is a lot of money, I've been playing house parties for a couple years and have started headlining conventions and raves. 

Playing big shows with huge crowds showed some of the things my FLX4 was lacking. Specifically, those were:

• Lack of booth outputs - if you can't hear yourself, you're going to be DJing using the echo of the sound off the back wall of the venue. This is a bad situation to be in, and headphones in my experience don't disclose the full story.
• Lack of 4 channels - I do a lot of live remixing and use stems constantly because I enjoy a lot of vocal music and mixing in rap vocals. I'd find myself playing the instrumental version of one track and the vocals of another... and then it's time to mix out and I'm left with the choice of cutting the vocals and looping the beat, or cutting the beat and doing acapella until I get the new track beat matched and phrase aligned. Not my favorite situation.
• Reliance on bringing my laptop to gigs - Not the biggest deal, but I'm already tired of lugging a ton of things to my gigs and I don't want to take too many chances with my $4,000 Razer laptop daily driver. I got it to be super reliable and fast for downloading tracks and processing stems, but that comes at the expense of heat and being tied to a power brick.
• XLR compatibility - XLRs are a standard connector type and are way stronger and more reliable than RCA cables. They are also "balanced" which increases the audio quality by reducing distortion during the amplification stage. 
• General feel - Okay, I understand the FLX4 is built to a price point, and it does a fantastic job. I am absolutely not beating up on it considering the $900 price premium I paid to get an improvement from it. After some heavy use, I noticed that the pitch bend randomly drifted slightly, but enough to mess up my beat matches.
• FX - This was a huge deal for me because my FX usage on the FLX4 was suffering because I didn't know what effect I was using. There's no screen or label that says which effect you're using and changing the effects and choosing which channel they're active on was inefficient. On the Prime 4, the thing has 11 total screens. It fully breaks out the FX so you can fully adjust the parameters and assign it to specific channels. Also, the FLX4 locks down some features that you would've gotten with a higher end model, while I guess the Prime 4 is the old flagship that got all the features.
• Ability to turn off the crossfader - I'm not a big scratch DJ. I do it sometimes, but for some shows I just want to disable it. On my FLX4 I 3D printed a "fader lock" that blocks me from accidentally hit it. On the Prime 4, there are switches for each channel that assign the crossfader to certain channels or "pass thru" to avoid any mishaps.

I got in my car to go pick up the Prime 4 and drove slightly outside of my state to meet with the Facebook Marketplace guy. He was a really cool guy and had been mixing for 30 years. His story was that he just needed more room and was daily driving some Denon SC5000s and a discrete mixer. I tested the controller a bit and paid him and drove all the way back home to tear into it and start migrating my Rekordbox library.

Versus the Prime 4+

This is the big question you'll probably be asking due to the major difference in prices you'll find online. Here's the difference:

• Released in 2023
• Stems support is included (you pay $10 once for this feature on the Prime 4 or other Engine DJ devices). Note that it released with on-console stem creation, but I think that was removed temporarily to rework it.
• Larger 6" jog wheels (vs. 5.1" on the Prime 4)
• Amazon Music and Apple Music support
• Some material changes

This wasn't convincing enough to make me spend an extra $1,000.

Software

This was one of the big things I was worried about, but I was pleasantly surprised in quite a few ways with Engine DJ. Denon gets that you may be coming from a competitor's software, so they offer library importing from Rekordbox, Serato, iTunes, and Tractor. It also offers just normal drag-and-drop track imports if you have a big folder of music files.

I'm coming from Rekordbox, so I had to export a copy of my existing library as an .xml format file. I just saved it on my desktop for easy accessibility and got rid of it when I was finished.

In RekordBox to export your library you can click "File" and then "Export Collection in XML format".

In Engine DJ, for Rekordbox to show up, you have to make sure it's enabled in the settings, as shown below. 

First click the gear, then "Library", and then make sure Rekordbox Library is enabled.

I imported it to Engine DJ by right clicking the area under my Rekordbox collection and chose to "Import Collection," selecting the XML file we just exported from Rekordbox.

Make sure you're in the Rekordbox menu in Engine DJ and then right click ON the Collections drop down to get the option to import your collection.

After a fairly quick importing job, I had all my track ratings, hot cues and labels, BPM and key information in Engine DJ. What a convenient solution.

I discovered Engine DJ is not like RekordBox exactly. You're not using the DJ controller to control the software on your PC, but you are able to play with the audio a bit from within the program. It's a music database first and foremost, which I'm absolutely fine with, and it does a great job at it despite being a little unintuitive in my opinion.

The friction I had with it stems from the fact that there's no "watch folder" option for the program to immediately import new tracks from a music folder on your computer. It is a database program, so you can just keep one giant folder, or a few sorted folders, or even folders with a certain amount of files in them so they don't get too laggy when you're filtering through them, but you do have to drag and drop the folder into your Collection every time you add new songs (if you're downloading tracks to your computer or ripping them from CD).

Additionally, I could not for the life of me get it to accept files from my SMB share coming from my server. Even mapping the share to a drive letter and changing the permissions to "Full Access" to "Everyone" did not help. However, keeping a folder on my local computer and dragging it worked fine. I'm not sure if this is a "me thing" since Denon claims you can store tracks and even stems on a networked drive, but at this point I think I'm done fighting with it.

I've chosen to add another SSD to my laptop and keep all the music and stems on it, and sync that with my Prime 4, and ensure I don't lose anything by backing that drive up to the server separately. This solution is fine I suppose, but I really hope they come up with clear guidelines on how to make sure it works with networked drives.

As for exporting your music to the Prime 4, there is a USB type B port on the rear of the device near the power button. It takes a USB 3.0 cable that you plug into your laptop. Once plugged in, you turn on the Prime 4, tap the "Source" menu, and choose "Computer Mode". This will enable it to be seen by Engine DJ on your computer. 

To get my music to export, I had to move it all to one playlist to make sure it was all on the device. It wouldn't let me export the collection, so this was my only option. 

First, click the "Sync Manager" in the bottom left, fill the box of all the playlists that you'd like to move onto the Prime 4's internal drive, and click "Export to Drive". It will then begin the exporting process.

It's also possible to move files to the Prime 4 by connecting it and moving files to the internal drive or importing them from a USB device. The reason you wouldn't do this is the Engine DJ software on the computer analyzes all the music that touches it, so it's already done and loaded into your library with key and BPM info for searching your tracks easier.

My overall impression of the software is that it's really basic and decently well done. That's all you really need when you're doing most of the work on the DJ hardware really. There needs to be a little bit more development before it becomes professional grade in my opinion as far as making the exporting process easier, but I did figure it out.

EDIT:

I did find out you can also directly just click and drag tracks onto the device if you enter "Computer Mode", which exposes the internal drive to your computer. However, this doesn't bring over track info, stems, or anything of that nature, so I would still advise using the Engine DJ program for this.

Stems

Finally, we have music on the device! I settled down to play some music but then realized how much I rely on stems. I listen to a lot of vocal EDM type tracks which can clash without a way to cleanly cut out the vocals or instruments. On Prime 4, there's a $9.99 one-time fee for enabling this, that can be paid from your InMusic account (which is required to set up the device initially anyway). Here's a link that'll take you to the InMusic store page for it. You can process stems in the desktop software, but you can only play them if you have stems unlocked on the device. An item of note, InMusic mentions that your Prime 4 must come online once every 30 days to ensure the stems license is valid... which is absolutely lame. If you purchase stems on the device, you should be able to use them until the Prime 4 goes up in flames. I question what will happen to stems on the device when the server InMusic uses to verify your purchase is taken offline. These days when companies remove features after you pay for them, the wording here really makes me nervous.

InMusic has a really good tutorial for getting stems working on your Prime 4, so I'll link that here if you need some help after purchase.

The stems take a long time to process. I'm using a Razer Blade 16 from 2023 on the Razer cooling pad and it's absolutely slow. Watching the process in Windows Task Manager, it appears to be working 3 threads at a time and therefore working on 3 songs at a time. However, the machine learning algorithm that it's using appears to be written to utilize Intel CPUs and Intel iGPUs only - leaving my fancy Nvidia RTX 4080 in my laptop unused. This was also a problem I saw with Rekordbox not utilizing my extra GPU power.

On the Prime 4, stems cannot be processed on the device itself and have to be pre-rendered on the desktop software. This is a big deal since Rekordbox did it on the fly, and did a pretty decent job on most songs, and got it done fairly quickly while caching them. I admit there's problems with the Pioneer approach as well, but I'm hoping Denon figures out how to utilize more power. That being said, Rekordbox would throttle the whole system while processing stems and would regularly cause audio to skip while I was using them and performing live, probably due to Windows prioritization of audio. I've heard this issue does not exist or isn't as pressing on Mac OS devices.

I do think it's interesting that they break the songs into 4 separate tracks (vocals, instruments, bass, and drums) versus Rekordbox just breaking out 3 (vocals, instruments, drums). The simplicity of RekordBox's approach didn't bother me, but I think having access to the extra track will enable more musicality in my mixes.

As far as file size, the stems will be about 2x the size of the original song. The actual results I tested had music that was about 10-12MB per track, and the stems were an additional 20-30MB per track. If you have a large library this will affect you, but storage is cheap (for now) so may as well have stems of everything. 

EDIT: I have now tried the stems and they are ROUGH, even compared to Rekordbox. There's a bunch of bleed-through of vocals and instruments even when turned off. Some tracks were better than others. There's probably a bias in the training data towards EDM tracks, but even with some of the relatively simple ones it still thought that the synth was vocals. There needs to be a big improvement to the stem processing before this is truly threatening Pioneer. I'm not sure if they need to start shooting nice job offers to the devs at Serato, but they need to improve their ML model to stay relevant to anyone who has gotten used to really clean stems.

Console Hardware

Okay, now I get to gush on it a little bit. The hardware is fantastic. It's a bit heavy, but it's also an extremely high-quality piece of equipment. It has 11 screens which cover the effects, album art in the middle of the platters, and the giant height-adjustable touch screen in the middle of the unit.

Most of the device is plastic, with aluminum "skins" on top to make the device feel more premium and hold up to wear better. It's worth noting that my curiosity got the better of me and I tried disassembling the console from the top only to find that this just removes the skin. 

In this picture you can see the skin is just an aluminum panel with labels on it and sticky tape on the back. Nice that it's replaceable, and eBay has a lot of skin options if you damage yours or want a different aesthetic for your Prime 4.

If you want to repair anything on this other than replacing said skin, you'll need to access it from underneath which will require quite a bit of disassembly. Parts availability looked pretty good online. The main boards were expensive, but the main components getting wear like the cue buttons and knobs and faders all seem to be pretty generic components that make it simple to fix if you know how to solder.

I'm not a big crossfader user, but this one is nice as far as they go. It feels quick and only the tiniest amount of friction to give it some weight. There are a bunch of hardware buttons on the top and front side of the unit to change how the crossfaders behave.

Source switches for each channel.

I'm a bit nervous about the chances of knocking the "X-Fader Contour" knob and breaking off the potentiometer. I found 2 units on eBay with this issue while I was shopping around.

The feel of the jog wheel platters and the pitch bend fader are my favorite things about the unit. The jog wheel is capacitive touch with a screen in the middle, and the outer portion is a really nice feeling plastic. The platter is cold to the touch and appears to be aluminum. There's an LED status ring that flows around it and shows the status of the playing track through colors. The pitch bend fader / bpm fader is aluminum, and there's a ton of travel. The range is adjustable in the software, and there's an LED that comes on when you're in the middle. The best part about the fader is that it is so smooth and makes perfect beat matching easy. Gone are the days of constantly having to bump my FLX4's fader up and down trying to make a 16% beat match stretch and wasting valuable time. This was worth the purchase.

The knobs, pads, and other faders also feel great. The one thing that I didn't expect is the plastic-y buttons for "Cue" and "Play", but they feel pretty good to use. I almost wish they did them the same way they did the performance pads in a firm but "drummable" rubber. The performance pads were very responsive and allow cue drumming to feel very direct and sensitive. Most of the knobs are covered in a rubbery material, making them feel premium.

Onto the Engine OS running on the device, it's very responsive. You can even search for media by plugging in a USB keyboard and it just works. I haven't used the Prime 4 outside yet, but I believe the screen is bright enough to navigate that. Following the example of the desktop software, Engine OS is very simple, but there's power and speed that comes with that. I haven't noticed any kind of lag or anything short of a perfect experience.

Pardon the glare, my light is very bright and not diffused. As you can see, the screen is pretty bright too. This is on the minimum brightness setting too.

This is a 4-channel device, so you can press a button to switch the platter from deck 1 to deck 3 and deck 2 to deck 4. This happens almost instantly, so it's not a big deal to quickly switch tracks and bump the bpm slightly. The mixer has all 4 channels displayed, so you can always change that without switching anything. I did have to go into the settings and change the mixer to "isolate", in order to fully cut a frequency band when I have the knob all the way down, but this is a style thing for me.

You can see on the right portion of both decks there's a "beat grid" section. You can play a song from your library and then hold the "Edit Grid" button until the editor shows up and then move the grid around with the platter. I've used it a couple times and it's pretty good and fast for making sure your live sets have good visual cues in case you can't hear what's going on for some reason, or you use "Sync".

In the middle there are 4 effects that you'll probably use most often: Filter, Echo, Wash, and Noise. I was worried they wouldn't be up to par with Pioneer, but they're actually just as good and quicker and more accessible to use. There's also a section at the top of the board for controlling more FX. There are 26 discrete effects:

• Echo
• Echo Out
• Swell Verb
• Delay
• Flanger
• Phaser
• Hold Echo
• Ping Pong
• Recycler
• Pitch Down
• Roll
• Stutter Out
• Riser
• Scale Down
• Reverb
• LFO Verb
• Reverb Drop
• Reverse Verb
• Reverb Rise
• Flanger (-)
• Flex Gate
• Beat Break
• LFO Filter
• Backspin
• Brake
• Crush (Bitcrush)

You can control the parameters, frequencies you apply the effects to, wetness / dryness, and beats that the effect is active on, so there's a ton of adjustability.

I'm not a big microphone user, so I haven't tested the mic outputs, but they seem intuitive and come with the ability to EQ, add echo, or set "Talkover" to auto-duck your playing tracks when you speak into the mic.

The connectivity options are really good because you can stream from sources like Tidal, Beatport, Soundcloud, Dropbox, and Beatsource. Additionally, you can connect to Ableton Link and control lighting systems with a subscription to Soundswitch. I don't use any of these services, but I like having the ability to tap into them if I'm doing weddings. For the most part, I'll be using the internal SSD that I got with mine. This one is 2TB, formatted internally to exFAT, but when I looked on Denon's guide for choosing a drive they mentioned that there's no real size restriction. The only guidance they give you is that SSDs are faster than spinning disks (HDDs), and that you should keep your library under 50,000 tracks for the best performance when sorting. After several years of DJing for diverse crowds, I have around 6,000-7,000 tracks and I'm constantly sorting through them so that's an acceptable limitation. I may have to increase the internal SSD size once I start rendering more stems. 

A note on the internal hard drive: though there is no size limit, transfers from the cable to your laptop are limited to USB 2.0 speed. In practice, my max transfer speed was 35 megabytes per second. This is really slow if you're moving bulk files often. If you're looking to purchase an SSD for your Prime 4, you don't need anything extremely fancy because of this. You still need an SSD to get good speed when browsing tracks, but faster drives will not speed up transfer because of the USB 2.0 limitation. If you need an SSD, this is a great choice for everyone. 2TB will fit 10,000-20,000 songs in lossless quality (with stems) and 50,000-75,000 songs in MP3 320 quality (with stems).

One of my main points about getting this was the booth output. I'm able to play my music on speakers facing the crowd, but the booth output allows me to also play it on speakers facing me so I can hear what the crowd hears without the delay. I haven't used this yet, but it's got a 2 band EQ and that's about all I need. Also, there is a zone output that you can assign to deck #4 and play music and control the level separately for another location. A good use for this would be weddings, where there's usually a main dance floor, but there might also be another location where you want some more chill music like near the food, or in a "hang out" spot that's not as loud as the dance floor.

On the right side of the console is FX bank 2, booth output settings, and "zone" settings, as well as the SD card and 2 USB inputs. Note the "device eject button" that it advises you use before removing drives to avoid corrupting the database. Over on the left is the master level control.

As far as places to plug things into the Prime 4, it's got a lot. 4 USB ports (2 rear, 2 top), and an SD card slot. The ports on the back are both XLR and RCA compatible, so you retain flexibility with whatever you're hooking into, whether it's a house party with someone's stereo receiver with RCAs, or a mainstage at a convention with XLR booth and mixer connections. There's also a 1/8" TRS headphone jack as well as a 1/4" jack so you have options there too. The microphone connections are XLR or 1/4". Sorry in advance for the rough pictures, this thing is big and I didn't want to move it.

Here you can see the phono / line in for external sources and turntables. Of course on the right of the image is the 2 mic ports.

You can see all the balanced inputs, the "Link" Ethernet connection which is for connecting to lighting products, 2 USB inputs, and the connection to the computer through the USB type B port.

Headphone input on the front. I like using the 1/4" because it seems stronger and harder to break off by bumping into it.

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- Nurem